LITERATURE

REVIEW
 Table of Contents
Chapter 1 INTRODUCTION................................................................... 1

1.1 BACKGROUND (CLASSIFICATION OF THE SECONDARY RMS) ... 1

1.2 THE TREATMENT OF THE SECONDARY RMS ........................... 2
1.3 DEMERITS OF PYROMETALLURGICAL TREATMENT OF
SECONDARY ............................................................................ 3
1.4 TREATMENT OF THE SECONDARY RMS BY
HYDROMETALLURGICAL PROCESSES ....................................... 3
1.5 MERITS OF HYDROMETALLURGICAL TREATMENT OF
SECONDARY RMS.................................................................... 4
1.6 MAIN METHODS OF METAL PURIFICATION AND
CONCENTRATION .................................................................... 5
1.7 APPLICATION OF ELECTROLYTIC IRON POWDER .................... 5

Chapter 2 POWDER MANUFACTURING TECHNIQUES .................... 8

2.1 WHAT ARE POWDERS ............................................................. 8

2.2 WHAT IS POWDER MANUFACTURING ...................................... 9
2.3 MERITS AND DEMERITS OF PM ............................................. 10
2.4 CHARACTERISTICS OF METAL POWDERS . ............................. 12
2.5 METHODS OF METAL POWDER PRODUCTION ........................ 14

Chapter 3 ELECTROWINNING ........................................................... 26

3.1 WHAT IS ELECTROWINNING .................................................. 26

3.2 HISTORY ............................................................................... 26
3.3 PROCESS ............................................................................... 27
 3.4 DIFFERENCES BETWEEN ELECTROWINNING AND
ELECTROREFINING ................................................................ 27
3.5 ELECTROWINNING OF IRON (PYROR PROCESS) ..................... 28
3.6 FUNDAMENTAL FEATURES .................................................... 30
3.7 DIAPHRAGM .......................................................................... 31
3.8 ANODES, COMPOSITION AND CONSTRUCTION ........................ 32
3.9 THE CATHODES .................................................................... 33
3.10 OPERATING CONDITIONS AND PRODUCT QUALITY ................ 34

Chapter 4 ELECTROREFINING .......................................................... 36

4.1 WHAT IS ELECTROREFINING ................................................. 36

4.2 CONCEPT .............................................................................. 36
4.3 STATIC\PACKED BED ELECTROLYSIS.................................... 39

Chapter 5 FACTORS AFFECTING ELECTROLYSIS AND OPTIMUM

CONDITIONS ...................................................................... 42

5.1 FACTORS .............................................................................. 42

5.2 POLARIZATION ...................................................................... 43
5.3 OPTIMUM CONDITIONS.......................................................... 47

Chapter 6 RECYCLING OF BATTERIES AND CANS........................ 49

6.1 WHAT IS BATTERY RECYCLING ............................................ 49

6.2 PROCESS OF RECYCLING BATTERY AND ITS MERITS ............. 49
6.3 BATTERY CASINGS ................................................................ 50
6.4 METALS RECOVERABLE FROM BATTERIES ............................ 51
6.5 BATTERY RECYCLING PROCESS ............................................ 51
6.6 RECHARGEABLE DRY BATTERIES.......................................... 52
6.7 RECYCLING RECHARGEABLE BATTERIES................................ 52
 6.8 SAFE DISPOSAL OF BATTERIES .............................................. 56
6.9 MERITS OF RECYCLING BATTERIES....................................... 56
6.10 RECYCLING OF CANS ............................................................ 58
6.11 RECYCLING STEEL CANS ....................................................... 59

Chapter 7 REFERENCES ..................................................................... 62

 Table of Figures
Figure 1 Ranges of particle size suitable for different applications of non-
ferrous powders. [2] .................................................................................. 9

Figure 2 Particle shapes [5] .................................................................... 13

Figure 3 Mechanical methods of powder production [1] ........................ 15

Figure 4 Chemical and electrochemical methods of powder production [1]

............................................................................................................... 16

Figure 5 Atomization processes [1] ......................................................... 21

Figure 6 Atomized particle shapes [1] .................................................... 22

Figure 7 Atomized Particle size [1]......................................................... 22

Figure 8 Methods of producing metal powders by electrolysis of metals [2]

............................................................................................................... 25

Figure 9 Pyror process flowchart [11] ..................................................... 29

Figure 10 Chemical analysis of obtained electrolytic iron powder [11] ... 35

Figure 11 Schematic diagram of the electrorefining process [12] ............ 37

Figure 12 Relation between potential and current density [14] .............. 38

Figure 13 Titanium anode basket [15] .................................................... 40

Table 1 Optimum conditions for powder electrodeposition [16] ............. 48

Table 2 Optimum conditions for powder electrodeposition [17] ............. 48

 INTRODUCTION
As a traditional technology, pyrometallurgy has been used for recovery of metals from
spent materials. However, it has encountered some challenges from environmental
considerations. Consequently, state-of-the-art smelters are highly dependent on
investments.

Today, the attention is directed toward the hydrometallurgical processes that are
already widely used for treatments from primary sources; in fact, most of the metals
extracted from the mines are recovered by hydrometallurgical techniques. For example,
cyanide leaching of gold has been used by the mining industries for more than 100
years.

Various innovative methodologies are used in the recovery of valuable metals and
critical raw materials (CRMs) from secondary sources. In particular, CRMs are
interesting due to their vast industrial applications, high market prices and extensively
used CRMs, the sanctuary value attributed to CRMs during international political and
economic crises, and the limited resource of these metals may explain the recent
increasing CRMs share value.

Background (Classification of The Secondary RMs)

Secondary RMs (Raw Materials) can be classified in scraps and by-products of
industrial and mining processes such as new scraps (in process scraps), residues
deriving from industrial processing (scraps, powders achieved during the production,
refining and metalworking operations) , tailings from mining operations with
interesting metallic contents and wastes as old scraps (post-consumer scraps), scraps
of metals from the collection of end-of-life products, wastes from electrical and
electronic equipment (WEEE).

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The Treatment of The Secondary RMs
The treatment of the secondary RMs is needed mainly to preserve the environment
from technological waste and avoid the release of pollutants components (toxic plastics
and metals), that belong to the fastest growing category of waste in the world: from
33.8 million tons in 2010 to 41.8 million tons in 2014 with a forecast of 50 million tons
in 2018. Another important objective is the transformation of the waste in resources.
In particular, WEEE are very interesting for the recycling of metal components because
they have concentrations of precious metals even typically higher than those of primary
resources (minerals) and don’t require extraction and pretreatment being available
after collection in urban centers (urban mining) with significant economic and
environmental benefits. WEEE are not only generically rich in metals, but are rich in
metals called critical. The metals present in secondary RMs can be divided into five
main categories:

1. Base metals: Cu, Al, Ni, Sn, Zn, Fe;

2. Precious metals (PMs): Ag and Au
3. Platinum group metals (PGMs): Pd, Pt, Rh, Ir, Ru
4. Hazardous metals: Hg, Be, Pb, Cd, As, Sb
5. Critical metals: rare earth elements (top five: Nd, Dy, Eu, Y, Tb), Te, Ga, Se, Ta,
In, Ge.

The recovery of base metals is not a target of the innovative treatments, which vice
versa point to precious metals, PGMs, and critical metals, for their high market value,
low availability, high demand, importance in emerging technologies, and relatively high
content in secondary RMs to primary sources.

Pyrometallurgical processes can only be operated on a large scale to be economically

viable; moreover, they are not able to recover non-metallic components (plastics) and
some metals, they are highly energy-consuming and are associated with the production
of harmful gaseous emissions.

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Demerits of Pyrometallurgical Treatment of Secondary
The application of the pyrometallurgical processes to the treatment of the secondary
RMs, presents the following main disadvantages:

• Unsustainable management and treatment from the economic and

environmental points of view.

• Production of polluting gases (halogenated compounds) that require large

investments for monitoring and abatement.

• Organic materials are not recycled.

• Failure to recover metals such as Fe and Al, which end up in the slag as oxides.

• Dust generation in exhaust fumes containing metals Zn, Pb, Sn, Cd, and Hg.

• Partial separation of the precious metals, such as Au and Ag, which requires
the use of hydro and electrometallurgical methods.

Treatment of the Secondary RMs by Hydrometallurgical

Processes
Hydrometallurgy consists in the extraction of metals through aqueous solutions.
Hydrometallurgical processes are generally characterized by the following main phases:

• Leaching with appropriate chemical agent: the metals are extracted from the
solid phase and transferred in the aqueous phase in the form of soluble ionic
species.

• Separation of the solid phase from the liquid phase through filtration,
decantation or centrifugation.

• Purification, concentration, recovery: removal of interfering species and/or

concentration of the target metal by precipitation, cementation, solvent
extraction, adsorption on activated carbon, ion exchange on resins, electrolysis.

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Hydrometallurgy is a new technology compared with pyrometallurgy, but offers
interesting perspectives, linked to the exhaustion of primary resources and the use of
RMs.

Merits of Hydrometallurgical Treatment of Secondary

RMs
The application of hydrometallurgical processes to the treatment of the secondary
RMs, presents the following main advantages:

• Materials that have low metal content to be treated with pyro processes can be
treated sustainably with hydrometallurgical processes.

• Hydrometallurgical methods are treatments at low temperatures that require

little energy expenditure in comparison with the pyrometallurgical processes.

• Hydrometallurgical processes can handle a wide range of incoming solids

through the same operations, optimizing operating conditions (flexible systems).

• Pyrometallurgical processes become sustainable only for very large scales that
require large initial investments and security over the supply of large quantities
of minerals for a long time; vice versa, hydrometallurgical processes are
sustainable even on medium small scales, requiring lower initial investment costs
and lower operating costs.

• The reagents used in the hydrometallurgical processes can be regenerated and

recirculated into the circuit of treatment.

• The hydrometallurgical processes allow obtaining high purity metals that do

not require further refining.

• In the hydrometallurgical processes there are limited corrosion problems

compared to those of the pyro processes that require refractory linings.

The hydrometallurgical processes constitute the future of metallurgical treatments as

they allow treating, by flexible and sustainable circuit, secondary resources, of different
mineral and technological origin, for metals recovery.

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Main Methods of Metal Purification and Concentration
After dissolution by leaching and subsequent solid/liquid separation, various methods
of metal purification and concentration can be applied; the main ones have been
reported as follows:

• ion-exchange resins

• adsorption on activated carbons: in the column, carbon in pulp (CIP), carbon

in leach (CIL)

• solvent extraction

• precipitation

• electrometallurgical processes.

Electrometallurgy includes metallurgical techniques that use electricity to recover

metals such as Cu and Zn by reducing from the purified and concentrated leached
solution (electrodeposition or electrowinning), to refine metals from pyrometallurgical
processes (electrorefining of Cu and Pb) and to recover metals from high purity oxides
that are melted and reduced (Al, Mg, Na, and Ca by electrolysis of molten salts).

Application Of Electrolytic Iron Powder

Among all types of commercial iron powders, iron powders produced by electrolysis is
the purest. It has a very irregular particle shape and therefore a relatively large surface
area per unit mass which make it ideal for many chemicals, catalytic and food additive
applications. In addition, due eliminating uncertain factors due to impurities it is used
as research material in various fields. In particular, it is essential for new product
development in the steel, special steel, and super alloys.

Electrolytic iron offers High malleability due a smaller number of impurities atoms
which hinder the dislocation motion ,High corrosion resistance compared to less pure

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iron due to formation of passive oxide film on its surface and has smaller coercive force
and high magnetic permeability make it good soft magnetic material.

1. Food additives

High purity electrolytic iron powder is used to fortify food - this is a process of adding
minerals to semi-processed foods for nutritional benefits. Bioavailability is key with
regards to electrolytic iron powder because it's 99.5% pure

2. Chemicals

Electrolytic Iron Powder can be used as a catalyst and reagent in chemical and
diamond production. The manufacturing will benefit from great productivity and cost
efficiency in its applications due to the high reactivity and purity of Electrolytic Iron
Powder. This pure iron powder is used in the industrial chemicals sector to create
intermediates and end products.

3. Pharmaceutical manufacturing

High purity electrolytic iron powder is the world's top choice for active pharmaceutical
ingredient manufacturers. It is employed as a reducing agent in pharmaceutical
reactions, and all grades of Electrolytic Iron Powder fulfil Food Chemical Codex
(FCC)chemical standards.

4. Magnetic alloys

High purity electrolytic iron powder is used in the production of Ferromagnets, where
high purity, good particle size distribution, and sintering qualities are required.

5. Transformer cores

Annealed electrolytic iron powder is used in the manufacture of ferromagnetic cores

for radios, televisions, and other audio devices.

6. Heat conductivity enhancement

Iron powder added to the polymers in order to withstand and transfer heat properly.
As it aids in the conductivity of heat and greater temperatures.

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7. Printing

High purity electrolytic iron powders may also be used to make magnetic inks and
toners. Because of its purity, soft magnetic characteristics, particle size distributions,
low density, excellent flow, powder shape, and electrical features, this pure iron powder
is one of the finest solutions for printing.

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 POWDER MANUFACTURING
TECHNIQUES

What are Powders

Powders appear to be an ill-defined group of substances. The scientific literature on
powders does not provide any evidence of what is or should be covered by the term,
nor can a clear-cut definition be found.

In the large international dictionaries such as the Encyclopedia Britannica, the

Encyclopedia Americana, 'Webster', etc., a powder is stated to be:

• Matter in a finely divided state: particulate matter

• A preparation in the form of fine particles, especially for medical use.

• any of various solid explosives (gun powder).

All of the sources above fail to establish a size range or an upper bound for what would
be accepted as a powder and what wouldn’t. the general consensus being that a
collection of small discrete solid particles in close contact with each other, the (empty)
space between the particles being usually filled with gas so that the bulk density of a
powder is always considerably lower than the density of the individual particles.
However, this definition also covers a heap of pebbles which no one would call a
powder.

While there is no general consensus to the upper and lower bounds of what constitutes
a powder, the following [fig.1] show the powder particle size range for various alloys
and applications.

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 Figure 1 Ranges of particle size suitable for different applications of non-ferrous powders. [2]

What is Powder Manufacturing

Powder manufacturing, more commonly referred to as powder metallurgy or PM for
short, refers to a broad range of processes used to create materials or component parts
using metal particles. In manufacturing, PM methods can minimize or completely
replace the need for subtractive manufacturing, minimizing material waste and product
costs.

PM also opens the door for using materials which can’t be obtained by traditional
manufacturing techniques due to technological limitations e.g., tungsten and its alloys,
as well as other refractory metals, it is also used to produce alloys and composites of
that meet certain design requirements.

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Merits and Demerits of PM

Merits

1. Economically friendly

From all the raw materials used for powder metallurgy, almost 97% are part of the
final product. PM techniques also have very little waste and no scrap. Every piece of
powder that enters the process is included in the finished component; this leads to
massive cost savings.

2. Flexibility

Unlike other processes, PM processes can mix and blend different materials (metals
and non-metals) into a single sound product. PM can also produce complex part
geometries and intricate design into its finished products.

3. Near-Net shape

The parts and products produced by PM require no secondary processing (subtractive

manufacturing), as each part is near net shape, and does not require any finishing.
Additionally, PM parts have an extremely high dimensional accuracy and low
tolerances.

4. Raw materials

Raw materials for powder metallurgy are easily accessible and readily available as well
as being relatively inexpensive. This is because powdered metals are very common, and
ordinary materials.

5. Repeatability

The repeatability and uniformity of PM processes avoids errors such as the degradation
in quality that occurs during production, which creates imperfections and deviations
in the final part, which is undesirable in mass production.

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6. Wear resistance

PM parts have a high wear resistance and coefficient of friction, which helps increase
their expected service life.

7. Chemical homogeneity

PM parts are chemically uniform which is free from slag, inclusions and the like. This
uniformity in chemical composition also results in uniformity in physical properties
which also increases the service life of the part.

Demerits

1. High capital investment and raw materials cost.

The required machinery and infrastructure to start production using PM techniques is

relatively expensive, so are the raw materials.

2. Size

PM parts techniques have many size constraints which prevent large parts due to the
required compressive force and compaction requirements.

3. Density

While PM parts have relatively high densities, they will always be less dense than
parts created using fusion processes.

4. Mechanical properties

While the produced parts will have excellent hardness and compressive properties,
their tensile and plastic properties will be much lower than those produced using fusion
methods.

5. Hazards

The storing of some metal powders might be hazardous as they could be radioactive
or chemically active. The risk of aerated powder explosion or dust explosion is also
always present.

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Characteristics of Metal Powders .
1. Chemical composition and purity

The chemical composition of a powder usually reveals the type and percentage of
impurity and determines the particle hardness and compressibility. Impurities are
elements or compounds which are undesirable in the material. These impurities not
only influence not only the mechanical properties, but also the chemical, electrical and
magnetic properties of the powder. It may also influence the pressing, sintering and
other post-sintering operations which are essential for the production of finished
product from powders.

2. Particle size

Particle size affects many properties which include: mold strength, density of compact,
porosity, expulsion of trapped (occluded) gases, dimensional stability, agglomeration
and flow and mixing characteristics. Metal powders used in powder metallurgy usually
vary in size from 20 to 200 microns. Particle size is expressed by the diameter for
spherical shaped particles and by the average diameter for non – spherical particles.
This is either measured using sieve analysis, or other methods of sizing.

3. Particle shape

There are various shapes of powder particles including:

6. Flaky
1. Acicular: needle-shaped
7. Lamellar: plate-like.
2. Angular: sharp-edged or roughly
8. Granular: approximately
polyhedral shaped.
equidimensional but irregularly
3. Crystalline: a geometric shape
shaped.
freely developed in liquid.
9. Irregular: lacking any symmetry.
4. Dendritic: a branched crystalline
10. Modular: rounded, irregularly
shape.
shaped.
5. Fibrous: regularly or irregularly
11. Spherical: globular shaped.
threadlike.

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 Figure 2 Particle shapes [5]

4. Particle microstructure

The metallographic examination of these powders will reveal not only various phases,
inclusion impurities, fissures and internal porosity, but also the particle size, relative
size distribution and particle shape.

5. Apparent density

Apparent density -sometimes called packing density or loading weight- is defined as

mass per unit volume of loose or unpacked powder. Thus, it includes the internal pores
volume, but not the external pores volumes. It is affected by: chemical composition,
particle shape, size, size distribution, method of manufacture of metal powders as well
as shape and surface condition. It normally ranges from 20-50% of theoretical density.

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6. Tap density

Tap density is the apparent density of the powder after it has been mechanically shaken
down or tapped until the level of the powder no longer falls. It appears to the widely
used for strong, packing or transport of commercial powders and also as a control, test
on mixed powders.

7. Flowability

The flow-rate/flowability is a very important characteristic of powders which measures,

the ability of a powders to be transferred. It is defined as the rate at which a metal
powder will flow under gravity from a container through an orifice, both having the
specific shape and finish.

Methods of Metal Powder Production

Metal powders can be produced using a wide variety of methods. These methods are
outlined in the figures below.

The fine details of these methods are beyond the scope of this study, so only a few of
them will be discussed, those being:

1) Mechanical Methods
a) Comminution\Milling
2) Chemical Methods
a) Chemical Reduction\Oxide Reduction
b) Decomposition of gaseous compound (Carbonyl Process)
c) Chemical deposition from solution
3) Physical Methods
a) Atomization
4) Electrochemical methods

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Figure 3 Mechanical methods of powder production [1]

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Figure 4 Chemical and electrochemical methods of powder production [1]

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Mechanical Methods
Comminution

Comminution is the oldest mechanical operation for size reduction of solid materials
and an important step in many processes where raw materials are converted into
intermediate or final products. It is the most widely used method of powder production
for hard metals and oxide powders. Secondary grinding of spongy cakes of reduced
oxide, electrolytic or atomized powders is the most common milling process; hammer
crushers and rod mills are used for this purpose. The energy efficiency of comminution
is very low and the energy required for comminution increases with a decrease in
produced particle size. Comminution occurs as two steps: grinding and milling.

Main purposes of comminution:

1. Particle size reduction 6. Solid-state blending (incomplete

(comminution or grinding). alloying).

2. Particle size growth. 7. Modifying, changing, or altering

properties of a material (density,
3. Shape change (flaking).
flowability, or work hardening).
4. Agglomeration.
8. Mixing or blending of two or more
5. Solid-state alloying (mechanical
materials or mixed phases.
alloying).
9. Nonequilibrium processing of
metastable phases

During milling, four types of forces act on particulate material: impact, attrition, shear,
and compression. Impact is the instantaneous striking of one object by another. Both
objects may be moving or one may be stationary. Attrition is the production of wear
debris or particles created by the rubbing action between two bodies. This type of
milling force is preferred when the material is friable and exhibits minimal abrasiveness.
Shear consists of cutting or cleaving of particles and usually is combined with other
types of force. Shear contributes to fracturing by breaking particles into individual
pieces with a minimum of fines. Compression is the slow application of compressive
forces to a body (crushing or squeezing of particulate material).

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Mechanism of comminution

1. Micro-forging

Individual particles or a group of particles are impacted repeatedly so that they flatten
with very small change in mass.

2. Fracture

Individual particles deform, and cracks initiate and propagate resulting in fracture.

3. Agglomeration

Mechanical interlocking due to atomic bonding or Van der Waals forces.

4. Deagglomeration

Breaking of agglomerates.

Chemical Methods
Chemical reduction\Oxide reduction

In the solid-phase reduction process, metal oxides or metal salts (carbonates, halides,
oxalates and formates) are treated by a reducing agent at temperatures below their
melting point. Oxide-reduced powders characteristically exhibit the presence of pores
within powder particles and thus are called sponge powders. This sponginess is
controlled by the number and size of the pores and accounts for the high green strength,
good compactibility and sinterability of such powders. Typically, high reduction
temperatures (> 0.6𝑇𝑀 ) facilitate the formation of large intraparticle pores and
powders of a small specific surface area that are required for a high compressibility.
Parallel with these, elevated temperatures may cause excessive sintering and
agglomeration, which cause difficulties with the disintegration of the sintered cake.
Low reduction temperatures lead to the production of powders with fine pores, large
specific surface area and high green strength. But extremely low reduction
temperatures (< 0.3𝑇𝑀 ) can readily produce pyrophoric powders.

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Process theory

Thermodynamics of metal oxide reduction by hydrogen or carbon monoxide is

determined based on the analysis of the generalized reaction:

1 𝑥
Generalized reaction: 𝑀𝑥 𝑂𝑦 + 𝐻2 (𝐶𝑂) ⇋ 𝑀 + 𝐻2 𝑂(𝐶𝑂2 ) Equation 1
𝑦 𝑦

Oxide dissociation: 𝑦
𝑀𝑥 𝑂𝑦 ⇌ 𝑥𝑀 + 𝑂2 Equation 2
2

Reducer combustion: 𝑦
𝑥𝐵 + 𝑂2 ⇌ 𝐵𝑥 𝑂𝑦 Equation 3
2
Decomposition of gaseous compound (Carbonyl Process)

Decomposition of gaseous metal carbonyl has been in use for many years as a method
of manufacturing high purity nickel and iron powders.

Since early in the 20th Century, crude nickel has been refined by passing carbon
monoxide over it to form nickel tetracarbonyl, 𝑁𝑖(𝐶𝑂)4 .

Nickel tetracarbonyl is liquid at room temperature and can be purified by distillation,

then decomposed to metallic nickel by heating to a higher temperature. Both nickel
powder and pellet are manufactured in this way.

In an analogous process, the reaction of 𝐶𝑂 with sponge or scrap iron to form iron
pentacarbonyl is used to make ultra-fine iron powder currently employed in a number
of applications, including metal injection molding.

Processing parameters for the decomposition of metal carbonyls can be controlled so

as to produce a variety of particle shapes, from fibrous to completely spherical, and
sizes down to a few microns or less.

Chemical deposition from solution

The Sherritt process for production of nickel and cobalt powders is an example of
chemical deposition from aqueous solution. In the Sherritt process, sulphide
concentrate (or matte) is first leached in an ammoniacal solution of ammonium
sulphate at 93~ under pressure, to facilitate purification. After removal of iron and

P a g e | 19
copper, nickel is recovered from the solution by the injection of hydrogen under
pressure, causing precipitation of metallic nickel. Successive layers are built up on the
particles, resulting in a granular powder with an 'onion skin' structure and an average
particle size around 150 microns. The Sherritt process has been in commercial use since
1954 and most of the nickel powder produced by this process is compacted into
briquettes or roundels for use as alloying feedstock in the steel industry.

Physical Methods
Atomization

Because of the ease with which a liquid can be broken up into fine droplets, atomization
has become the prevailing mode of powder production of nonferrous metals and their
alloys. Currently, the worldwide atomization capacity of non-ferrous metals amounts
to 10 million metric tons per year. The basic types of atomization processes include:

4. Impact atomization a liquid

1. Jet atomization, where a liquid
stream
metal is dispersed into droplets
5. Ultrasonic atomization, where a
by the impingement of high-
liquid metal film is subjected to
pressure jets of gas, water or oil
ultrasonic vibration
2. Centrifugal atomization, where a
6. Impulse atomization, where
liquid stream is dispersed into
impulses are mechanically applied
droplets, flakes, or ribbons by the
to the melt
centrifugal force effect of a
7. Vacuum atomization, where
rotating disk, spinning cup,
heavily saturated molten metal
spinning roller or consumable
with a gas is atomized in the
electrode
vacuum
3. Disintegration of liquid metal

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 Figure 5 Atomization processes [1]

General characteristics of atomized powders

1. Particle size

Atomized metal powders are generally found to follow log normal distributions before
any screening is done.

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 Figure 7 Atomized Particle size [1]

2. Particle shape

The principal characteristics that set atomized

powders apart from powder produced by other
methods such as electrolysis, reduction,
precipitation, and so forth, is their shape and
density. It is generally true to say that
atomized powders are free of fine porosity and
are relatively compact, with high packing
densities and low surface areas, compared with
these other types of powder. This means that
they have good flow characteristics, good
compressibility, and lower sintering activities
than other types.
Figure 6 Atomized particle shapes [1]

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 3. Purity

It is a general characteristic of atomized powders that there are no impurities of the

type found in chemically or electrolytically produced powders that can have chloride
or sulfate surface contamination. However, dissolved impurities such as oxygen, sulfur,
or carbon can be found, normally unchanged in concentration from the melt. Inclusions
are also mainly determined by melt practice, except where sloppy handling allows
contamination after manufacture, an ever-present problem for all powders. Surface
oxidation is often thought of as the main purity index, but is not always as important
as the other two types, especially where oxides are readily reduced in sintering.
Obviously, inert atmosphere processes minimize contamination, while air atomization
introduces the most impurities. Water atomization lies between these extremes.

4. Gas porosity

Is a special case of contamination. If porosity is found in any atomized powder, the

first suspicion is always of gas solution in the melt, normally hydrogen, but possibly
oxygen or steam. Hydrogen-bearing melt stock (e.g., cathode nickel, copper, cobalt)
and dampness should be checked and melt deoxidation practice reviewed.

5. Composition and microstructure

Atomization has the fundamental advantage over other methods of powder production:
the composition is completely flexible, being limited only by melt miscibility or
volatility considerations.

The powder particle sizes resulting from atomization allow cooling rates many orders
of magnitude above those in casting processes, ranging from 102 to 107 K/s. This is
now known as rapid solidification (RS), but well before the invention of this
terminology, such materials as 𝐶𝑢𝑃𝑏 bearing alloys and PM high-speed-steel were being
produced by atomization and PM compaction methods.

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Electrolytic Methods

The electrolytic or electrochemical methods can be used to produce a variety of metal

powders. The main properties of such powders are purity, dendritic shape of particles
and good compressibility. Electrochemical methods make it possible to control
crystallization (definite shape and size of powder particles) by selecting the process
parameters: concentration of the metal and hydrogen ion exponent pH of the
electrolyte, cathode potential, current density, temperature and rate of circulation of
the electrolyte, type and size of anode and cathode and their distance from each other,
type and quantity of addition agents and conditions of removing deposits at the
electrodes. The use of some techniques (permanent anodes, electrochemical reduction
from solid phase, electrodes with highly developed surface) makes it possible to utilize
production waste and to achieve complete recovery of the metal as powder. Electrolytic
powder alloys do not require chemical homogenization; moreover, some alloys are
produced only by the electrochemical method.

P a g e | 24
Figure 8 Methods of producing metal powders by electrolysis of metals [2]

1, with non-permanent anodes; 2, with permanent anodes; 3, on smooth electrodes; 4, on electrodes with
developed surface and heightened transient factor; 5, galvo dynamic electrolysis; 6, controlled potential
electrolysis; 7, impulse electrolysis: (a) current impulses; (b) current impulses alternated with
ultrasonic impulses (zone electro-chemistry).

P a g e | 25
 ELECTROWINNING

What is Electrowinning
Electrowinning, also called electroextraction, is the electrodeposition of metals from
their ores that have been put in solution via a process commonly referred to as leaching.
Electrorefining uses a similar process to remove impurities from a metal. Both processes
use electroplating on a large scale and are important techniques for the economical and
straightforward purification of non-ferrous metals. The resulting metals are said to be
electrowon.

In electrowinning, an electrical current is passed from an inert anode (oxidation, made

out of lead (Pb)) through a leach solution containing the dissolved metal ions so that
the metal is recovered as it is deposited in an electroplating process onto the cathode
(reduction, stainless steel, aluminum (Al), titanium (Ti). In electrorefining, the anode
consists of the impure metal (e.g., copper, iron) to be refined. The impure metallic
anode is oxidized and the metal dissolves into solution. The metal ions migrate through
the acidic electrolyte towards the cathode where the pure metal is deposited. Insoluble
solid impurities sedimenting below the anode often contain valuable rare elements such
as gold, silver and selenium.

History
Electrowinning is the oldest industrial electrolytic process. The English chemist
Humphry Davy obtained sodium metal in elemental form for the first time in 1807 by
the electrolysis of molten sodium hydroxide. Electrorefining of copper was first
demonstrated experimentally by Maximilian, Duke of Leuchtenberg in 1847. James
Elkington patented the commercial process in 1865 and opened the first successful
plant in Pembrey, Wales in 1870. The first commercial plant in the United States was
the Balbach and Sons Refining and Smelting Company in Newark, New Jersey in 1883.

P a g e | 26
Process
Most metal ores contain metals of interest (e.g., gold, copper, nickel) in some oxidized
states and thus the goal of most metallurgical operations is to chemically reduce them
to their pure metallic form. The question is how to convert highly impure metal ores
into purified bulk metals. A vast array of operations has been developed to accomplish
those tasks, one of which is electrowinning. In an ideal case, ore is extracted into a
solution which is then subjected to electrolysis. The metal is deposited on the cathode.
In a practical sense, this idealized process is complicated by some or all of the following
considerations: the metal content is low (a few percent are typical), other metals
deposit competitively with the desired one, the ore is not easily or efficiently dissolved.
For these reasons, electrowinning is usually only used on purified solutions of a desired
metal, e.g., cyanide-extracts of gold ores.

Because metal deposition rates are related to available surface area, maintaining
properly working cathodes is important. Two cathode types exist, flat plate and
reticulated cathodes, each with its own advantages and disadvantages. Flat plate
cathodes can be cleaned and reused, and plated metals recovered by either
mechanically scraping the cathode (or, if the electrolyzed metal has a lower melting
point than the cathode, heating the cathode to the electrolyzed metal's melting point
causing the electrolyzed metal to liquify and separate from the cathode, which remains
solid). Reticulated cathodes have a much higher deposition rate compared to flat-plate
cathodes due to their greater surface area. However, reticulated cathodes are not
reusable and must be sent off for recycling. Alternatively, starter cathodes of pre-
refined metals can be used, which become an integral part of the finished metal ready
for rolling or further processing.

Differences Between Electrowinning and Electrorefining

Electrowinning and electrorefining are important industrial processes useful in
obtaining a pure metal from impure metal ore. The key difference between

P a g e | 27
electrowinning and electrorefining is that in the electrowinning process, the impure
metal is in the leach solution, whereas in the electrorefining process, the impure metal
is the anode. Moreover, in electrowinning, an electric current pass-through leach
solution from anode to the cathode, where the pure metal is deposited on the cathode,
while in electrorefining, impure metal is the anode, and it gets oxidized to dissolve the
metal into the solution, followed by the movement of metal ions through the electrolyte
towards the cathode for pure metal deposition.

Electrowinning is the electrodeposition of metals from the ores that have been put in
solution via leaching. Electrorefining is the electrodeposition of metals from the ores
that have been put in solution to remove impurities from the metal ore. The key
difference between electrowinning and electrorefining is that in the electrowinning
process, the impure metal is in the leach solution, whereas in the electrorefining process,
the impure metal is the anode.

Electrowinning of Iron (Pyror Process)

The underlying idea of the Pyror process was to bring the iron content of the pyrite
(𝐹𝑒𝑆2 ) into an acid-soluble form (𝐹𝑒𝑆), using a heat treatment to expel the loosely
bound second Sulphur atom from the pyrite. The heat treatment was performed either
as a calcining procedure at 800 to 900 °𝐶 under inert atmosphere or by smelting in an
electric furnace. The latter may preferably be performed with the addition of an iron
oxide-containing material, such as a fayalite slag.

As acid for the extraction of iron we chose to work with sulphuric acid, mainly because
hydrochloric acid is a more corrosive agent, thereby creating greater problems in
handling. The extraction of the iron was carried out at 90 to 95 °C in a three-stage
counter-current leaching system of the Dorr–Oliver type, the reaction being:

𝐹𝑒𝑆 + 𝐻2 𝑆𝑂4 ⇌ 𝐹𝑒𝑆𝑂4 + 𝐻2 𝑆 Equation 4

P a g e | 28
 Figure 9 Pyror process flowchart [11]

In [fig.9] is shown a flow-sheet presenting the main features of the Pyror process. The
flow-sheet is very simplified. In particular, this relates to the treatment of Residue 1.

Prior to entering the electrolytic cells, the solution is purged with air, to get rid of
remaining hydrogen sulphide and to form minor amounts of iron hydroxide to occlude
contaminants. The purified solution from the leaching process enters the electrolytic
cells, in which iron is deposited at the cathodes, while oxygen is evolved and sulphuric
acid is regenerated at the anodes. In a subsequent step trivalent iron in the electrolyte
is reduced by means of hydrogen sulphide or Sulphur dioxide. The reduced electrolyte
is recycled to the leaching system, thus closing the circuit. The residue from the
leaching step (Residue 1) is taken to a sulphating roasting followed by processing of
the various valuable components through more or less well-known methods.

P a g e | 29
Fundamental Features
The reactions taking place in an electrolytic cell when depositing iron from a solution
containing iron sulphate, can be written as follows.

At the Cathode:

𝐹𝑒 2+ + 2𝑒 − → 𝐹𝑒 Equation 5

1
𝐻 + + 𝑒 − → 𝐻2
2 Equation 6

𝐹𝑒 3+ + 𝑒 − → 𝐹𝑒 2+ Equation 7

At the Anode:

1
𝑆𝑂42− + 𝐻2 𝑂 → 𝐻2 𝑆𝑂4 + 𝑂2 + 2𝑒 −
2 Equation 8

𝐹𝑒 2+ → 𝐹𝑒 3+ + 𝑒 − Equation 9

Reactions [Eq.5] and [Eq.8] are the main reactions, while [Eq.6], [Eq.7] and [Eq.9] are
undesirable side reactions. In addition to the above-mentioned reactions, a secondary
oxidation takes place to some extent, involving the oxygen being evolved at the anode.

1
2𝐹𝑒𝑆𝑂4 + 𝑂2 + 𝐻2 𝑆𝑂4 → 𝐹𝑒2 (𝑆𝑂)4 + 𝐻2 𝑂 Equation 10
2

This reaction has the same end product as reaction [Eq.9]. These reactions clearly show
that electrolysis must be performed using a diaphragm in order to prevent the anodic
reaction products to reach the cathode, thereby reducing the current yield.

𝑔
The electrical conductivity of a solution in the iron concentration range of 20 − 30
𝐿

is fairly low. Therefore, to reduce the voltage drop across the cell, additions of salts
like sodium or ammonium sulphate were made to improve this situation.

P a g e | 30
Even more important is the salt addition as a means to improve the current yield.
Thus, an increase in the concentration of Glauber salt

𝑔
(𝑁𝑎2 𝑆𝑂4 · 10 𝐻2 𝑂) from 0 − 200 , all other conditions being unchanged, raised the
𝐿

current yield from 65% to 90%. This may be explained by 𝑁𝑎+ ions taking over part
of the current transport from 𝐻 + ions, thereby reducing the tendency of the latter to
be discharged at the cathode. At the same time, fewer 𝐻 + ions will pass through the
diaphragm, having a favorable effect by resulting in a higher pH in the catholyte. The
negative influence of low pH on the current yield was fairly small in the pH range 2.0–
2.75, while it was clearly noticeable below pH 2.0.

Above a pH of about 2.75 the quality of the iron deposit deteriorated, exhibiting
increased surface roughness, including the formation of dendrites (“trees”). This was
associated with oxide inclusions in the deposit. Surface roughness and dendrite
formation also appeared at current densities above 2.7– 2.8 𝐴 ∙ 𝑑𝑚− 2 . This can be
ascribed to a diffusion-controlled deposition mechanism, which gives rise to excessive
hydrogen evolution. Temperature variation within the range from 70 to 90 °C had very
little effect on the current yield. High temperature diminished the surface roughness of
the iron deposit.

Diaphragm
As explained in the preceding paragraph, a diaphragm between the cathode and the
anode compartments was required in order to obtain acceptable current yield and
product quality. Several different candidate materials were tested, such as asbestos
cloth, glass cloth impregnated with silica gel, porous sintered stainless steel etc. Only
when fabrics made of vinyl chlorideacrylonitril became available to us (supplied by
Wellington Sears Co.), a diaphragm that gave satisfactory and reproducible results
could be made. Even better was a terylene fabric supplied by Gourock Ropework
(Scotland). It was of the continuous multi-filament type, GX 2620, 33/34 shoots per

P a g e | 31
inch. As demonstrated towards the end of the test period in the pilot plant, an average
current yield of 85% could be attained with the use of this type of diaphragm.

Anodes, Composition and Construction

Electrowinning of iron requires an anode material that in principle is insoluble. In a
sulphate environment a lead-based anode is the natural choice. However, pure lead
shows insufficient corrosion resistance under the conditions in question, in addition to
being too weak mechanically. Therefore, a rather extensive study was initiated to find
a suitable lead alloy for this purpose. These tests were started in 1950 and were
continued during the next 7 years until the operation of the pilot plant was
discontinued in 1957.

The test equipment was quite simple: A plate of the alloy in question was placed into
a U-shaped frame of ebonite, while the cathodes, being of the same alloy, were located
on either side in such a way as to keep exactly the same distance to the anode plate.
After starting up the pilot plant, the test liquid was anolyte from this system, the
liquid being renewed every other day. Otherwise, the test conditions were a
temperature of 80 °C, current density 3 𝐴 ∙ 𝑑𝑚− 2 . The test anodes were evaluated by
weighing and by visual inspection. The best results were obtained with an alloy
containing:

• 𝑤𝑡. % antimony

• 𝑤𝑡. % tin

• Balanced lead

The experience gained in the pilot plant supported this conclusion.

The results obtained with the above-mentioned alloy corresponded to corrosion rates
in the range of 0.13 to 0.25 mm per year, which is very low and certainly acceptable
in practice. The corresponding lifetime of a 10 mm thick anode was estimated to be 4
to 5 years.

P a g e | 32
Throughout the years various anode designs were tested, of which the following was
preferred. The anode was cast as a simple plate of 10 mm thickness, with a saw-toothed
lower edge. This plate was welded to a busbar, which was made of copper embedded
in a lead alloy of the same composition as the anode plate. Along the edges of the
anode was placed a half-rounded profile of semi-hard rubber, supporting the diaphragm
and keeping it away from the anode surface. The diaphragm material was formed like
a bag, which was fitted to the anode unit and glued together along the top.

The feed solution was added to the cathode compartment through a main measuring
nozzle and was taken out of the anode units through individual nozzles. There was a
tendency of the diaphragm to become clogged by impurities, crystallization of sodium
sulphate etc. To prevent it from building up, causing an increased difference between
the levels of the catholyte and anolyte, a bent glass tube acted as a bypass valve to let
some of the liquid flow directly into the anode compartment. The width of the anode
between the rubber edges was 910 mm, and the thickness of the complete anode
assembly was 35 mm.

The Cathodes
As far as cathode material is concerned, there are in principle two ways to go. A
starting sheet may either be included in the product, which means it should be made
of electrolytic iron, or other materials may be used, the iron deposit then being removed
by stripping.

In the latter case different types of materials were tested, such as hot- or cold-rolled
steel, acid-resistant steel plates of various thickness, aluminum etc. The stripping
proved to be quite cumbersome and labor intensive, despite efforts to prepare the
starting sheets so as to facilitate stripping. On a larger scale starting sheets made of
electrolytic iron by combined hot- and cold rolling would undoubtedly be the best
choice in this respect. In the pilot plant starting sheets made of electrolytic iron were
used in a few cases only.

P a g e | 33
The starting sheets were soldered to the busbars, which were made of 50 by 16 mm
steel equipped with a copper or copper alloy edge contact. The width of the cathode
was 950 mm, the submerged height being 1020 mm. The spacing between the cathodes
was 105 mm, thus allowing 28 cathodes and 29 anodes to be placed into an electrolytic
tank with inner dimensions of 3.0 by 1.05 m, and a height of 1.2 m. The tank was
made of steel with a lining of hard rubber. The tank was resting on glass blocks that
served as electrical insulators. Maximum 15 cathodes were used in each of the two
tanks, due to limitations set by the rectifier capacity (8000 A, 12 V).

Operating Conditions and Product Quality

As for the operating conditions in the electrolytic cell, the feed solution had an average
acidity corresponding to pH ∼ 2.0. The iron concentration ranged from 55 to 65 g/L,
of which close to 99% was in the divalent form. The content of sodium sulphate
(𝑁𝑎2 𝑆𝑂4 ) was 55−60 g/L.

The catholyte solution was approximately pH ∼ 2.0, about 25 g/L iron and 90 to 100
g/L sodium sulphate. In the anode compartments the electrolyte contained sulphuric
acid in the range 55– 60 g/L, 55–65 g/L sodium sulphate, and about 25 g/L iron, of
which 60–75% was in the trivalent form.

Prior to being recycled to the leaching system, the trivalent iron was reduced by
hydrogen sulphide. Sulphur dioxide could also be used to compensate for any loss of
sulphuric acid.

The cell temperature ranged from 75 to 80 °C, the current density was around

2.5 𝐴 ∙ 𝑑𝑚− 2 and the cell voltage was about 3.75 V, including losses at the edge
contacts. The temperature had a pronounced effect on the properties of the iron
deposit. It was found that a temperature of at least 70 °C had to be applied to avoid
cracking and peeling of the deposit. The preferred temperature was 75 °C, with due
regard to the quality of the deposit, energy consumption, anode corrosion etc.

P a g e | 34
 Concerning the quality of the iron product, the objective was to produce a fairly
ductile iron with a smooth surface free from pores, thus being well suited for large scale
production. Porous, brittle iron for the production of iron powder was beyond the scope
of the project. A too low concentration of iron in the catholyte solution had a
detrimental effect on the iron deposit, resulting in cracking and peeling. All factors
taken into consideration; an iron concentration of 25 g/L seemed to be optimal.

Tests were carried out with various impurities in the catholyte solution. Metal
impurities like zinc, manganese, antimony, lead and chromium had negligible effects
on the deposit, whereas Sulphur in elemental form and as hydrogen sulphide resulted
in a rough surface, partly with dendrites (“trees”). A similar rough surface appeared
when trivalent iron entered into the cathode compartment, e.g., as a consequence of a
leaking diaphragm. The tendency towards tree formation was most pronounced along
the edges of the cathode. It was counteracted by giving the cathode a somewhat larger
submerged area than that of the anode. A representative analysis of the electrolytic
iron produced towards the end of the test period is given:

Electrolysis could be run for up to several S ( total) 0.007 wt.%

weeks before stripping was performed, S (sulphide) 0.003 wt.%
resulting in coherent deposits of Zn 0.003 wt.%
considerable thickness (13 mm and more on Co 0.006 wt.%
either side).
Cu b 0.0005 wt.%
As mentioned above, the voltage drop Cr b 0.0001 wt.%
across the cell under the given conditions
Al b 0.0001 wt.%
was about 3.75 V. At a current yield of 85%
Mn b 0.0001 wt.%
this corresponds to an energy consumption
of 4.25 kWh per kg iron. P b 0.0001 wt.%
As b 0.0001 wt.%
Si b 0.0005 wt.%
Figure 10 Chemical analysis of obtained electrolytic iron powder [11]

P a g e | 35
 ELECTROREFINING

What is Electrorefining
Electrorefining is one of electrochemical process which concerned with removing
impurities from impure metal which act as anode in electrolytic cell and the cathode
is a pure metal, Electrorefining using either aqueous solutions or molten salts as
electrolyte, Aqueous electrolyte is used in refining some metals such as copper and
nickel, but refining of reactive metals such as aluminum, titanium, vanadium molten
salts are used .

main advantage of electrorefining is the wide variation of quality of the scrap metals
purification of many common metals as well as reactive metals can be electro refined
but copper electrorefining outweighs all others.

Depending on the type of impurities to be removed, electrorefining can be done in one

of two ways. Either the impurities are selectively removed from the anode so that the
purity of the metal arises, or the impure metal forms the anode which further dissolved
as ions the deposited as pure metal on the cathode.

Despite the fact that both of these techniques are documented in the literature for
electrorefining processes, the second way appears to predominate in commercial
practice.

Concept
The principle of electrorefining based on using an applied potential to make
electrochemical reactions occur in desired direction (Selective Deposition) , the external
source supply the cell with the required current and potential .the electrochemical cell
consists of anode of the impure metal and the cathode is pure metal both immersed
is electrolyte contains the metal ions of purified metal and other additive which increase

P a g e | 36
the efficiency of process such as organic additives which added to modify the
morphology of deposit on cathode.

The electrolyte and other parameters are selected to insure both the anodic dissolution
and the deposition of the metal occur with high efficiency and none of the impurity
metals can transfer from the anode to the cathode

when the electric charge is supplied to the cell this make oxidation process occur at
anode which make the impure metal dissolve as metal ions which in turn migrate to
the cathode on its surface it deposited as pure metal.

Figure 11 Schematic diagram of the electrorefining process [12]

Cathodic Reaction 𝑀𝑒 +𝑛 + 𝑛𝑒 − → 𝑀𝑒

Anodic reaction 𝑀𝑒 → 𝑀𝑒 𝑛+ + 𝑛𝑒 −

The type of impurities, current density and electrolyte composition determine the
degree of purity and the morphology of the deposited metal.

The impurities in the metal either have a potential more than the purified metal (More
noble) or have a potential less than it (less noble).

At the anode the impurities which less noble will dissolve but more noble impurities
will not dissolve and fall down to electrolyte and forming anodic slime which can
further processed to extract the precious metals.

P a g e | 37
At the cathode fewer noble impurities will not be deposited, and more noble impurities
could be deposited depending on deposition overpotential and their concentration

The choosing of electrorefining based on electrolysis conditions which hinder the

dissolved impurities from be deposited on the cathode and ensure the impurities that
can be deposited will not dissolve at anode.

The primary parameters of electrorefining are potential and current density which is a
direct measure of kinetics. Increasing the potential will increase the current density
which by turn increase the rate of electrorefining process .

energy required is much lower than that in the electrowinning because no additional
potential is required to overcome the difference in half cell potential and elimination
of large overvoltage of water hydrolysis so the applied potential is only required to
overcome the overpotential of deposition and dissolution which is generally small and
the potential drop. 𝑉𝑎𝑝𝑝𝑙𝑖𝑒𝑑 = 𝜂𝑐 + 𝜂𝑎 + 𝐼𝑅

Figure 12 Relation between potential and current density [14]

P a g e | 38
Static\Packed Bed Electrolysis
In conventional electrorefining, the metal has to be refined is first melted and formed
into the shape of an anode, these cast are suspended from an integrated ears which
make electrical contact with circuit.

In electrochemical operations, the static bed technique (anode support system) which
uses impure metal in particulate form can be used to substitute the conventional anode
plates. Inert metallic basket anode is used and filled with small pieces of metal to be
dissolved. This technique has been used in metal refining on a laboratory and industrial
scale. During continuous operation the metal level in the basket continually decreases
and it is necessary to provide for topping up the basket

The basket-anodes can be filled with a wide form of anode particulates, including
irregular chips, squares, rectangles, and granules. These anode particles can be
generated using pyrometallurgical operations or scrape chopping in general, the anode-
support is shaped like a rectangular basket with two or more flat parallel perforated
sides and the bottom is unperforated plate. But the process may require a different
shape of basket such as using cylindrical basket in plating internal face of tubes.

Titanium, graphite are typical materials to make this basket, but other metals are
occasionally utilized as well. Although Titanium is common material to make these
baskets as it durable and not corrosive because of formation of passive oxide film and
has lighter weight it should not be used in electroplating process that employ periodic
reverse current because the metal is partially despassivated during the cathodic cycle.

P a g e | 39
 Figure 13 Titanium anode basket [15]

Merits and Demerits of Static Bed Electrorefining

Merits

1. Energy saving because of needn't to melt impure metal and cast it as in

conventional way
2. It eliminates the need for specially shaped anode metal and the practice of
replacing corroded anodes.
3. It allows for a continuous anode area by refilling the anode mass on a regularly.
4. It gives the best current distribution and, as a result, the most uniform thickness
in various cathode regions.
5. The electrode material has a high specific area, which accelerates the dissolving
of impure anode particles.
6. less slime falls to the cell bottom when compared to conventional anode plates
7. Throughout the electrorefining process, the anode does not change shape.
8. The anode area's size may be readily adjusted using plastic screens.
9. Compared to conventional way There are no leftover anode ears that need to
be remelted since all of the metal that needs to be refined is submerged in the
electrolyte.

P a g e | 40
Demerits

1. The system's high cost if titanium basket is used, resulting in a higher initial
investment.
2. The anode mass can develop voids during filling the baskets, which might lead
to titanium active corrosion in these areas, which requires using rounded shaped
particulates to reduces the problem.
3. The oxide film that covers its surface functions as a barrier against further
corrosion of titanium but also act as an electrical insulator. For this reason,
when this system is compared to the conventional cast or rolled anodes, the
energy requirement must be sufficient to accommodate for the somewhat higher
voltage drop.

P a g e | 41
 FACTORS AFFECTING ELECTROLYSIS
AND OPTIMUM CONDITIONS

Factors

Current Density

Current density refers to the amount of current passing through a unit area of an
electrode. A high current density can result in rapid metal deposition and impurity
removal, but it can also cause overheating and reduce the efficiency of the process. An
example of this can be seen in the electrowinning of copper, where a high current
density can result in rapid copper deposition, but it can also cause the formation of
copper dendrites that can reduce the efficiency of the process.

Temperature

Temperature affects the solubility of metal ions and the rate of reaction in the
electrolyte solution. Increasing the temperature can increase the solubility of the metal
ions and the rate of reaction, but it can also cause thermal stress and reduce the
efficiency of the process. An example of this can be seen in the electrorefining of
aluminum, where high temperatures can increase the rate of aluminum production, but
it can also cause the formation of aluminum oxide that can reduce the efficiency of the
process.

Electrolyte Composition

The composition of the electrolyte solution affects the solubility of the metal ions and
the rate of reaction. The electrolyte must be formulated to provide optimal solubility
for the metal ions and to maintain the stability of the solution. An example of this can

P a g e | 42
be seen in the electrowinning of zinc, where the composition of the electrolyte solution
can affect the solubility of the zinc ions and the rate of reaction.

Electrode Composition

The composition of the electrodes affects the rate of metal deposition and the rate of
impurity removal. The electrodes must be formulated to provide optimal conductivity
and to maintain the stability of the electrode surface. An example of this can be seen
in the electrorefining of nickel, where the composition of the electrodes can affect the
rate of nickel deposition and the rate of impurity removal.

Agitation

Agitation of the electrolyte solution can improve the mass transfer and increase the
rate of reaction. However, excessive agitation can cause mechanical stress on the
electrodes and reduce the efficiency of the process. An example of this can be seen in
the electrowinning of lead, where agitation can improve the mass transfer and increase
the rate of lead deposition, but excessive agitation can cause mechanical stress on the
electrodes and reduce the efficiency of the process.

Voltage

The voltage applied to the electrodes affects the rate of metal deposition and the rate
of impurity removal. A higher voltage can result in rapid metal deposition and impurity
removal, but it can also cause overheating and reduce the efficiency of the process.

Polarization
In electrochemistry, polarization refers to the effect of a voltage or current on the
electrochemical potential of an electrode. When a current flows through an electrode,
it can cause a change in the electrochemical potential of the electrode, which can lead
to a decrease in the rate of electrochemical reactions at the electrode surface.

P a g e | 43
This effect occurs due to the buildup of charge on the surface of the electrode, which
can create a barrier to electron transfer and reduce the rate of electrochemical
reactions. This buildup of charge is often referred to as the "overpotential," and it is
a measure of the voltage required to overcome the barrier and initiate the
electrochemical reaction.

Polarization can occur in a variety of electrochemical processes, including

electrorefining and electrowinning, as well as electroplating, fuel cells, and batteries.
In these processes, polarization can have a significant impact on the efficiency and
effectiveness of the process by reducing the rate of reaction and increasing the energy
required to carry out the process.

Various techniques can be used to reduce the effects of polarization in electrochemical

processes, such as optimizing the operating conditions, adjusting the current density
or voltage, and using specialized electrode materials. By minimizing the effects of
polarization, it is possible to improve the efficiency and effectiveness of electrochemical
processes and produce high-quality products.

Polarization is a phenomenon that occurs during electrolysis, which is the process of

using an electric current to drive a chemical reaction. In electrolysis, a voltage is
applied to an electrolyte solution, causing the positive ions to move towards the
negative electrode (cathode) and the negative ions to move towards the positive
electrode (anode). However, as the current flows, a buildup of charge can occur at the
electrodes, which can lead to polarization.

In electrorefining and electrowinning, polarization can have a significant effect on the

efficiency and effectiveness of the process.

Electrorefining is the process of purifying impure metal through the use of electrolysis.
During electrorefining, polarization can lead to a decrease in the rate of metal
deposition on the cathode. This can result in a lower quality of the purified metal and
may require longer processing times to achieve the desired level of purity.

P a g e | 44
In electrowinning, polarization can also occur, leading to a decrease in the rate of metal
deposition on the cathode. This can result in a decrease in the efficiency of the
electrowinning process, which can lead to higher costs and lower yields.

To minimize the effects of polarization, it is important to carefully control the voltage

and current during the electrolysis process. Additionally, the use of specialized
electrolytes and electrode materials can help to reduce polarization and improve the
efficiency of the electrorefining and electrowinning processes.

In electrorefining, polarization can be caused by a number of factors, including the

resistance of the electrolyte, the size and shape of the electrodes, and the current
density (i.e., the amount of current per unit area of the electrode surface). As the
current flows through the electrolyte and the electrodes, a buildup of charge can occur
at the surface of the electrodes, which can lead to an increase in the potential difference
between the anode and cathode. This can lead to a decrease in the rate of metal
deposition on the cathode and an increase in the rate of metal dissolution on the anode,
resulting in lower purity of the refined metal.

In electrorefining, polarization can be caused by several factors, including the

resistance of the electrolyte, the distance between the electrodes, and the composition
of the electrolyte. As the current flows through the electrolyte, it encounters resistance,
which can cause a voltage drop and result in polarization. The size and shape of the
electrodes can also affect the current distribution and lead to uneven deposition of
metal on the cathode.

To reduce the effects of polarization in electrorefining, it is important to optimize the

operating conditions of the electrolysis process. This can include adjusting the current
density and the temperature of the electrolyte to reduce the resistance and promote
more efficient ion transport. The use of specialized electrode materials can also help to
reduce the effects of polarization by providing a more uniform surface for metal
deposition. For example, the use of electroplated copper cathodes in copper

P a g e | 45
electrorefining can improve the purity and quality of the refined copper by reducing
the effects of polarization.

To reduce the effects of polarization in electrorefining, several techniques can be

employed. One such technique is to increase the temperature of the electrolyte, which
can reduce the resistance of the solution and promote more efficient ion transport.
Another technique is to use specialized electrode materials, such as graphite or
platinum, which can reduce the buildup of charge at the electrode surface and improve
the efficiency of the electrolysis process. Additionally, controlling the current density
and the voltage applied to the electrodes can help to minimize the effects of
polarization.

In electrowinning, polarization can also occur due to a number of factors, including the
resistance of the electrolyte, the size and shape of the electrodes, and the concentration
of the metal ions in the electrolyte. As the current flows through the electrolyte and
the electrodes, a buildup of charge can occur at the surface of the cathode, which can
lead to a decrease in the rate of metal deposition.

To reduce the effects of polarization in electrowinning, several techniques can be

employed. One such technique is to increase the concentration of metal ions in the
electrolyte, which can promote more efficient ion transport and reduce the buildup of
charge at the cathode surface. Another technique is to use specialized electrode
materials, such as nickel or stainless steel, which can improve the efficiency of the
electrolysis process by reducing the effects of polarization. Additionally, controlling the
current density and the voltage applied to the electrodes can help to minimize the
effects of polarization.

In electrowinning, polarization can also occur due to a number of factors, including the
concentration of metal ions in the electrolyte, the size and shape of the electrodes, and
the rate of mass transfer between the electrolyte and the electrodes. As the current
flows through the electrolyte and the electrodes, a buildup of charge can occur at the
cathode surface, which can lead to a decrease in the rate of metal deposition.

P a g e | 46
To reduce the effects of polarization in electrowinning, it is important to optimize the
operating conditions of the electrolysis process. This can include adjusting the current
density and the voltage applied to the electrodes to reduce the buildup of charge at
the cathode surface. The use of specialized electrode materials, such as lead or titanium,
can also help to reduce the effects of polarization by providing a more uniform surface
for metal deposition.

Overall, the effects of polarization on electrorefining and electrowinning can have

significant impacts on the efficiency and effectiveness of these processes. By carefully
controlling the voltage, current density, and electrode materials used in these processes,
it is possible to minimize the effects of polarization and improve the efficiency and
purity of the refined metals produced. However, it is important to note that the specific
techniques used to reduce the effects of polarization can vary depending on the metal
being refined or recovered, the composition of the electrolyte, and other factors specific
to the particular process.

Optimum Conditions
After carefully reviewing multiple reference documents, several possible conditions were
obtained. These include:

P a g e | 47
 Anode material Mild steel scrap (Packed Bed)

Cathode material Stainless steel sheet

pH 3.5 - 5.5

Voltage 7 -10

Current density
𝐴
(Cathodic) 0.3 - 0.5
𝑐𝑚2

Electrode spacing 2.5 – 3.5 cm

Temperature 45 − 55°𝐶

Electrolyte 𝐹𝑒𝐶𝑙2 : 20 𝑔𝑚; 𝐾𝐶𝑙: 14.35 𝑔𝑚; 𝑁𝐻4 𝐶𝑙: 14.35 𝑔𝑚; 𝐹𝑒𝐶𝑙3 : 0.5 𝑔𝑚

composition 𝑝𝑒𝑟 500 𝑚𝑙 𝑜𝑓 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑙𝑦𝑡𝑒

Table 1 Optimum conditions for powder electrodeposition [16]

Anode material Mild steel scrap

Cathode material Stainless steel sheet

pH 4.5

Voltage 3.2

𝐴
Current density (Cathodic) 0.1
𝑐𝑚2

Electrode spacing 3 cm

Temperature 25 − 30°𝐶

𝑔𝑚 𝑔𝑚
Electrolyte composition 12 𝐹𝑒 2+ ; 75 𝑁𝑎𝐶𝑙
𝑙 𝑙
Table 2 Optimum conditions for powder electrodeposition [17]

P a g e | 48
 RECYCLING OF BATTERIES AND CANS

What is Battery Recycling

Before we go into battery recycling, let's define batteries. A battery, on the other hand,
is a substance containing chemicals capable of converting chemicals into electrical
energy. Battery recycling is the practice of reusing and reprocessing batteries in order
to reduce the number of batteries discarded as material waste. Batteries include a
number of hazardous chemicals and heavy metals, and the contamination of soil and
water caused by their disposal has aroused environmental concerns. Recycling batteries
is therefore vital for both environmental and health reasons.

Normally, batteries can power a wide range of gadgets. They include lamps,
automobiles, and phones. Batteries can also be utilized to power a home as an
additional source of electricity. Batteries are no longer infinitely usable. Things either
grow rotten or unusable over time. That is where battery recycling comes in.

Recycling batteries entails processing them. The goal is to ensure that you can reuse
them rather than throw them away. This is critical since it reduces the quantity of
batteries that are improperly disposed of. It is important to note that batteries contain
metals and hazardous chemicals. Furthermore, if battery components are regularly
discarded, they may cause land and water contamination. As a result, it would be
preferable if you safeguarded the environment from these harmful consequences.
Furthermore, recycling avoids the need for new battery production, which contributes
to the worldwide material waste problem.

Process of Recycling Battery and its Merits

Many of the devices we use now run on both battery and gas. These two elements have
one thing in common: they can be used indefinitely. When they do, it is customary to
refill gas or dispose of old batteries and replace them with fresh ones. However,

P a g e | 49
disposing of batteries may result in a significant amount of garbage in the environment.
Furthermore, batteries are widely utilized and contain a large amount of hazardous
material. So, getting rid of them might not be the best choice. Recycling your batteries
is an alternative to tossing them away. Unlike many other items such as plastic and
paper, recycling batteries has unique fundamentals.

Battery Casings
Most battery casings are made of corrosion-resistant, lightweight materials such as
plastic, aluminum, or steel alloys. These materials can be molded or molded into
elaborate patterns and shapes, as well as coated or processed to improve their
performance or appearance, making them appropriate for battery casings.

Iron or iron alloys may be utilized in some specialized battery types, such as those
used in large-scale industrial applications, where the extra weight and durability of
iron is desirable. Yet, for the majority of consumer gadgets and other portable devices,
battery casings should be composed of lightweight and corrosion-resistant materials.

Many distinct battery types, particularly those used in heavy-duty or industrial

applications, feature steel casings. This is because steel is a strong, long-lasting, and
corrosion-resistant material that can provide the battery with the necessary protection
while remaining relatively light and portable.

Steel alloys, such as stainless steel, are widely used in battery casings due to their high
strength and resistance to corrosion and rusting. Steel casings can be molded into
elaborate designs and structures to provide additional protection and durability, and
they can be tailored to accommodate a variety of battery types and sizes.

Steel casings can also be coated with various materials or given additional treatments
to improve their operation or appearance. For example, to add more insulation or
shielding from moisture or other external variables, a layer of plastic or similar polymer
material may be placed to the steel battery box.

P a g e | 50
Steel is a popular material for battery casings due to its strength, endurance, and
corrosion resistance. However, depending on the battery's specific function and needs,
various materials such as plastic, aluminum, and other alloys may be used in battery
casings.

Metals Recoverable from Batteries

• High-quality ferromanganese concentrate recovered from batteries can be

utilized by steel manufacturers. One ton of this concentrate replaces at least
three tones of manganese-containing iron ore, saving the energy required for
iron ore extraction and processing.

• Concentrate of zinc recovered from batteries, which contains at least 40% zinc,
is reused by zinc smelters and in industrial electrolysis.

• Mercury Recovered from batteries, pure mercury can be utilized in metric

instruments and fluorescent lighting.

• Nickel The nickel recovered from batteries can be used to make stainless steel.

Battery Recycling Process

You are already aware that batteries can be recycled. Knowing how to recycle batteries
is also essential. You must first recognize that there are multiple batteries before you
may recycle them.

Various batteries have various components. They include lead, lithium-ion (Li-ion),
nickel-metal hydride (Ni-MH), nickel-cadmium (Ni-Cd), lithium-ion polymer, nickel-
zinc, and alkaline. Manufacturers utilize these components to make various batteries.
As a result, the use, power, as a result, while the majority can be recycled, there are a
number of steps necessary. Also, certain batteries can be recycled more simply than
others. Remember that this can occasionally be influenced by the cost of their
constituent parts as well as the toxicity of the chemicals used to manufacture them.

P a g e | 51
Rechargeable Dry Batteries
Rechargeable battery technology is quickly evolving, and its application in consumer
products is rising. These batteries have a lengthy life but must be disposed of at some
point.

Nickel-metal hydride batteries

These batteries were designed as a less damaging alternative to 𝑁𝑖𝐶𝑑 batteries and
have a longer life.

Nickel cadmium batteries.

Cordless power tools, medical equipment, alarm systems, and emergency lighting all
employ nickel cadmium (𝑁𝑖𝐶𝑑) batteries. The EU has prohibited the use of 𝑁𝑖𝐶𝑑
batteries in other applications since cadmium is harmful to human health and adequate
alternatives exist for all other applications.

Lithium-ion and lithium-ion polymer (Li-Ion) batteries

These batteries store more energy than 𝑁𝑖𝐶𝑑 and 𝑁𝑖𝑀𝐻 batteries. Cameras, MP3
players, laptop computers, and mobile phones all contain them. Because they have the
potential to create flames, they must be transported with caution.

Recycling rechargeable batteries

When rechargeable batteries reach the end of their useful life, they can be recycled in
the following ways:

To prevent hydrogen from escaping, NiMH batteries are reprocessed by manually

separating the various materials (plastic, hydrogen, and nickel) within a vacuum
chamber. The end result is a product with a high nickel content that can be utilized
to make stainless steel. Other metals, including iron, are recovered as well.

P a g e | 52
A pyrometallurgical procedure is used to cure 𝑁𝑖𝐶𝑑 batteries. The cadmium removed
is 99.9% pure and can be utilised in fresh batteries. Iron nickel can also be recovered
and used to make steel.

Pyrolysis (heat treatment) is used to reprocess Li-Ion batteries in order to maximize

the recovery of cobalt and other metals such as iron and copper for resale. The residual
products can then be used in smelting plants, cement plants, and as road construction
materials.

Alkaline Zinc Air /Zinc Carbon Batteries

Alkaline batteries are recycled by mechanically separating their components. The first
step is to gather used alkaline batteries, as well as lead batteries and other battery
kinds. The batteries are sorted after separation.

When batteries are dismantled for recycling, three portions are removed. The
components are made of steel, plastic, and paper, as well as zinc and manganese.

Producers use the materials that have been processed in recycling plants to create new
products.

For the recycling of zinc-carbon and alkaline batteries, a hydrometallurgical process is

proposed. A preparatory treatment for the disassembly of batteries, followed by an
acidic-reductive leaching. The resulting solution is subsequently purified, and zinc and
manganese dioxide are extracted using electrolysis. Separation of zinc-carbon and
alkaline batteries from other types of batteries is done manually.

Batteries are crushed using a hammer mill in the dismantling area, and the black
powder, which contains graphite and metallic oxides, is separated from the coarse
fraction by screening (iron scraps, plastic films and paper pieces). A magnetic
separation is used to separate magnetic waste, and an electrostatic separator is used
to recover non-ferrous materials.

Plastic films and papers that remain are either landfilled or burned. Metallic waste can
be recycled for steel and ferro-alloy manufacturing using a pyrometallurgical process.

P a g e | 53
The battery powder is washed with water to remove the potassium hydroxide; the
resultant solution can be evaporated to produce pure KOH or neutralized by sulphuric
acid to yield potassium sulphate. An acidic-reductive leaching employing sulphuric acid
and hydrogen peroxide as reductant can achieve total dissolving of zinc and manganese
oxides.

This section produces a manganese and zinc sulphate solution, along with other
dissolved metals; as a result, the solution must be filtered before proceeding to the
electrowinning section.

The aqueous solution is then passed through a precipitation process in which iron is
precipitated by ammonium hydroxide (pH = 4) and certain metallic ions are eliminated
by zinc dust (reducing agent) during the cementation step. The purified Zn-Mn
solution is then ready for electrowinning, which involves plating metallic zinc on the
cathode and manganese dioxide on the anode. The electrolysis exhaust solution is
recycled back into the leaching reactor.

Lithium Ion, Nickel Metal Hydride, Nickel-Cadmium Batteries

Lithium-ion (Li-ion) rechargeable batteries are used in electronics and autos.

Automobiles and portable devices such as cameras also use rechargeable nickel-based
batteries.

Both batteries are similar in terms of recycling. They also match lead-acid batteries in
numerous aspects during the recycling process. Here is a detailed step-by-step guide to
recycling lithium and nickel batteries.

• Collection

Recycling companies pick up discarded lithium and nickel batteries through this
method from drop-off locations or other places.

• Sorting

P a g e | 54
Recycling workers remove the plastic components of a battery from the metal ones in
this stage. Both resources are ideal for creating new items.

• Smelting

High-Temperature Metal Reclamation is carried out here on the lithium-ion and nickel-
based battery components. Extraction techniques are also used on the metals in the
batteries. In this process, metals including iron, nickel, manganese, and chromium are
obtained and used to create new items.

Mercury Batteries

After collection, mercury batteries are recycled using liquid and heat extraction
processes. In mercury batteries, extremely toxic metals are discovered. Because of the
existence of these toxic metals, recycling businesses handle recyclable materials under
strictly controlled extraction settings.

The mercury recovered during the extraction process can be utilized to manufacture
new mercury batteries, measuring devices, and fluorescent light components.
Manufacturers may employ plastic and other materials derived from batteries to make
new things.

Recycling batteries can be difficult. Recyclers must therefore be aware of these

challenges for recycling diverse battery varieties. Mercury batteries are being phased
out due to their very toxic components, while equipment manufacturers continue to
use other battery types.

Knowing the parts of your batteries will help you use them correctly and dispose of
them for recycling.

You are well aware that the first stage in recycling batteries is collection. But how
should batteries be collected precisely?

P a g e | 55
Safe Disposal of Batteries
The numerous battery kinds that we have were made using varied materials and
production processes. The procedure for recycling batteries has been described.
Whether it is acceptable to place batteries in a recycle bin is one important question.

We've discussed the collection procedure needed for battery recycling. But it's
important to distinguish between gathering batteries and throwing them in a recycle
bin. Instead of recycling bins, recyclers collect batteries at collection sites.

Because of this, you shouldn't put batteries in a recycling bin. The causes are
completely obvious. Batteries can have their hazardous materials and heavy metals
washed away by placing them in a recycling bin. These dangerous compounds may
seep into other items and negatively affect soil, water, and air and make pollution.

Additionally, for safety concerns, it is not suggested to place batteries in recycling bins.
Despite the fact that some of these batteries are dead, by placing them in a recycling
bin, you ensure that they go in recycling trucks with other items. Due to the current
that the battery and the movement of the vehicle may produce, the battery's
components could catch fire.

Therefore, think carefully before you dispose of that dead battery in the recycling bin.
Instead, properly recycle your battery by bringing it to a collection site. In this manner,
the battery can be processed such that the recyclers can get excellent use out of it.

Merits of Recycling Batteries

Why recycle batteries now that you know and the best way to do it? There are many
benefits to recycling, indeed.

As we already mentioned, used batteries can seriously hurt the environment. And we
don't want that. That being said, recycling is a wise decision. We are able to protect
the environment thanks to it.

P a g e | 56
Do you want to know how this occurs, then? Here are five reasons that recycling
batteries helps the environment and the entire globe.

1. Conservation of Non-Renewable Resources

Recycling batteries enables the conservation of raw resources that cannot be replaced
by people. For instance, recyclers reuse used or waste items to conserve metals and
natural resources. Other manufacturers can use the resources in this way to develop
new products.

2. Recycling Batteries Prevent Pollution

Batteries that are incorrectly disposed of risk having their chemicals wash away. The
dangerous substances may contaminate the air, water, or soil by evaporating or
leaching. Recycling batteries will reduce pollution and keep them out of the
environment.

3. Recycling Reduces Solid Waste That Ends Up in Landfills

Batteries that have been recycled can be used to make new goods. They can avoid
going into landfills this way.

4. Battery Recycling Saves Energy

It takes a lot of energy to manufacture fresh batteries. However, manufacturers use

less energy when recycling old batteries. Recycling allows you to save the energy
required to produce new batteries. The power can be used by manufacturers to create
other practical items.

5. Recycling Creates New Jobs

People are required at recycling plants to complete the entire process. As a result, more
employment opportunities are provided by battery recycling.

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Recycling of Cans
Cans are containers made of metal that can be used for a number of things, including
packaging other goods as well as storing and preserving food and beverages. Beverage,
food, and aerosol cans made of aluminum and steel are typical can kinds.

Steel and Aluminum , which are the two most common materials used to make cans,
are both highly recyclable. Recycling cans aids in resource conservation, energy
efficiency, and greenhouse gas reduction. Can recycling is the act of gathering and
turning used cans into new goods.

The following steps are commonly included in the recycling of aluminum cans:

• Collection: Cans are gathered from customers, businesses, and other sources and
categorized according to the type of content.

• Shredding: The cans are broken down into tiny pieces and burned in a furnace
to get rid of any coatings or impurities.

• Melting: To produce aluminum ingots or billets, the shredded and thoroughly

cleaned metal is then heated in a furnace.

• Rolling: After being rolled into thin sheets, the aluminum ingots or billets are
ready to be used to make new aluminum cans or other items.

Similar methods are required for recycling steel cans, but extra stages are also necessary
to remove coatings and prepare the steel for melting, such as magnetic separation to
separate steel from other components.

By generating jobs in the recycling sector, recycling cans not only supports local
economies by reducing waste and conserving resources. Can recycling also lessens the
quantity of waste that is disposed of in landfills and incinerators, which can assist to
lessen environmental pollution and safeguard public health.

P a g e | 58
Differences Between Steel and Aluminum Cans

Although both steel and aluminum cans are generally made up of metal, there are a
number of noticeable distinctions. Because iron makes steel magnetic, you can identify
a can as steel by seeing whether it attracts a magnet. Steel is more frequently used to
package food (e.g., coffee and pet food), while aluminum is more frequently used to
package drinks (such as soda). When recycled, aluminum cans will yield a higher profit
than steel cans, although steel is employed in a wider range of items, such as houses
and automobiles.

Recycling Steel Cans

One of the first types of food packaging, steel cans date back to the 14th century and
are used to store everything from pet food to vegetables to soup. Tin lining is frequently
used to line steel cans, giving them the nickname "bi-metal cans," but this has no
bearing on how recyclable the product is.

Recycling Steel Cans Preparation

1. The paper label found on the majority of steel cans does not need to be removed.
It won't be worthwhile for you to separate the paper and recycle it with other
paper because it will be removed throughout the recycling process due to its
poor quality.
2. Rinse your cans thoroughly to get rid of any food residue. This will lessen the
possibility of animals attacking your recycling and stop your recycling container
from stinking.
3. Completely remove the steel lid, insert it into the container, and then clamp
the top shut. Additionally, this will stop animals like cats or birds from getting
their heads stuck in the cans.

P a g e | 59
Process of Recycling Steel Cans

1. Collection Steel cans are gathered from homes, places of business, and recycling
drop-off locations. Steel cans are sometimes collected separately from other
recyclables, while in other places they could be put in a bin with other
recyclables.
2. Sorting: Aluminum cans, plastic bottles, and paper are separated from the steel
cans. Either physical labor manually or mechanized machinery automatically
can accomplish this.
3. Processing: Steel cans are cleaned and ready for recycling during processing.
The cans' labels and other non-metal components are removed, and the cans
are then broken up and shredded into small pieces.
4. Melting: Steel that has been shredded is melted to a liquid form in a furnace.
To make new goods, the liquid steel is then poured into mould.
5. New product creation: The liquid steel can be molded into a variety of goods,
including new steel cans, building supplies, automobile components, and home
appliances.
6. Distribution: Recycled steel is used to create new products that are used in a
variety of sectors.

Merits of Recycling Cans

Reasons to recycle steel cans:

• With a recycling rate of more than 88 percent, steel has the highest rate of any
material. Steel cans are able to be recycled into any steel product, although this
is primarily because of scrap metal, such as cars.

• Cans made of steel can be recycled indefinitely without losing any quality. Metal
is scarcer than glass, paper, or plastic, hence recycling is more important.

P a g e | 60
 • Since recycled steel makes up two thirds of all new steel produced, the other
third must be made of virgin materials.

Environmental Advantages:

The decrease in garbage that is dumped in landfills is one of the main advantages of
recycling steel cans. Metal from recycled steel cans is melted down and used to create
new goods. Due to the fact that fresh steel does not need to be mined or created from
scratch, this procedure conserves natural resources. Additionally, recycling steel cans
helps to minimize greenhouse gas emissions by lowering the energy needed to generate
new steel.

Economic Advantages:

Steel can recycle can also have positive financial effects. For instance, steel is one of
the commodities that is recycled the most globally, and its high rate of recycling aids
in lowering the environmental effect of steel manufacturing. Moreover, recycling steel
cans is typically more efficient

P a g e | 61
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