MASS TRANSFER - II

CORE PAPER

UCH – 2603

SSN AUTONOMOUS REGULATIONS 2018

Lecture 5.4 – Dialysis and Ion Exchange
Course Instructor: Dr. Nalinkanth V. Ghone
Associate Professor, Chemical Engineering
SSN College of Engineering

Email: nalinkanthv@ssn.edu.in
Mobile: 8122603376
 Membrane Technology

• Dialysis
Artificial kidney.

- NaOH recovery in textile effluents, alcohol

removal from beer, salts removal
(pharmaceutical industry).
• Dialysis
Looks not very important...?.

GS PV
ED
MF
HD

UF
RO

Membrane and module markets

 Membrane Technology

• Electrodialysis (ED)
 Membrane Technology

• Electrodialysis (ED)
 Membrane Technology

• Electrodialysis (ED)
-Ionic Membranes (non porous).
- Based on polystyrene or polypropylene with
sulfonic and quaternary amine groups.
- Thickness: 0.15-0.6 mm.

- ED with reverse polarization (EDR).

- ED at high temperature (60ºC).
- ED with electrolysis.
 Membrane Technology

• Electrodialysis (ED)
VC
- Required membrane area c+out

j+  dA +m + VC  z  dc+ = 0 j+

VC

• Charge flow
c+in
i: electric current density (A/m2)
Am: membrane surface (m2)
j+  F dI
=i= combining
 dA m

AT = N  A m =
+
N  VC  cin +
(
− cout +
 z  F V  cin
=
) +
− cout zF ( )
i i
η: global electrical efficiency (~0.5 commercial equipment) j: cation flow (eq/m2 s)
F: Faraday constant (96500 C/eq) N: number cells in the equipmentz: cation charge (eq/mol)
 Membrane Technology

• Electrodialysis (ED)
- Then the required energy, E (J), is
UC: potential gradient in a cell (V)
E = N  UC  I  t = N  I  R C  t
2 RC: total resistance in a cell ()

( )
as + +
VC  cin − cout zF
I = i  Am =

then 2
 VC  c  z  F 
E = N    RC  t
  
2
 VC  c  z  F 
ó P = N    RC
  
P: required Power (J/s)
 Membrane Technology

• Electrodialysis (ED)
Where, the required specific energy, (J/m3), is
2
E  c  z  F 
Ê = = VC     RC
N  VC  t   

La cell resistance can be estimated from a model

based on series of resistances where the resistances to
transport are considered through two membranes and
the compartments concentrate and diluted.
 Membrane Technology

• Electrodialysis (ED)
- How to determine operational i?
Limit boundary • Cation Transport
 
i +
 tM = D 
(
z  c +D − c +DM i +
+ t
)
cCM+ F  F
cC+
i=
(
D  F  z  c+D − c+DM )
( )
- +
cD+
  t +M − t +

cDM+ If cDM+D= F0 z  c+

ilim =
  tM − t )
(
D
concentrate diluted + +

Cationic Membrane Usually: i = 0.8ilim t: transport number

D: diffusion coefficient
 Membrane Technology

• Electrodialysis (ED)
- Intensity Evolution versus applied potential

i (A/m2)
Ionic water
splitting

Resistance rise
ilim
Ohmic zone

U (V)
 Membrane Technology

• Electrodialysis (ED)
- Fields of application:
Water desalination.
- Competing to RO.
- Economically more interesting at very high or
very salt concentrations.

- Other fields of application:

Food Industry.
Treatment of heavy metal polluted water.
 Membrane Technology

• Electrodialysis (ED)
- Examples:

 Water softening.
 Production of drinking water from salty
water.
 Nitrate removal.
 Lactose demineralization.
 Acid removal in fruit juice.
 Tartrate removal from wines.
 Heavy metal recovery.
 Production of chlorine and sodium
hydroxide.
 Membrane Technology

• Electrodialysis (ED)

Electrolytic Cell for the production of

chlorine and sodium hydroxide with
cationic membrane.
 Membrane Technology

• Electrodialysis (ED)

Electrolytic cell for the production of

sulfuric acid and sodium hydroxide
with bipolar membrane.
 Membrane Technology

• Electrodialysis (ED)
Anode
H2 2H++ 2e-

Cathode
O2 + 4e- + 4H+ 2H2O

Global
2H2 + O2 2H2O

Hydrogen fuel cell with a cationic

membrane.
 Membrane Technology

• Pervaporation
- Industrial applications.
- Alternative to distillation when thermodynamic
limitations.
• Low energy costs.
• Low investment costs.
• Better selectivity, without
thermodynamic limitations.
• Clean and closed operation.
• No process wastes.
• Compact and scalable units.
 Membrane Technology

• Pervaporation
1.0

azeotrope
0.8
Ehtanol at permeate

Phase equilibria
(vapour)
0.6

pervaporation
0.4

pseudoazeotrope
0.2

0.0
0.0 0.2 0.4 0.6 0.8 1.0

Ethanol at feed (liquid)

Pervaporation process of an ethanol/water mixture with a PVA

membrane.
 Membrane Technology

• Pervaporation
Condenser
Distillation
column
Ethanol >90% w/w

Feed Intermediat Ethanol >99.95% w/w

tank

Permeate

Plant for
Pervap. unit

Ethanol 20-80% Ethanol 15% w/w

production of
w/w Boiler

Water
ethanol from
sugar
Combination of distillation and pervaporation (Bethéniville,
for the
France).
 Membrane Technology

• Pervaporation
Dehydration of organic solvents.

Organic solvents to apply

pervaporation.
Methanol Alil alcohol Ethyl Acetate Tricloretilene
Ethanol Furfurol Buthyl acetate Tetrachloretane
n-Propanol Methylfurfurol Diethyl ether Tretrahydrofurane
Isopropanol Diethilenglicol Diisopropyl ether Aniline
n-Buthanol Acetone Dipropyl ether Benzene
t-Buthanol Buthanone Ethyl propyl ether Toluene
2-Penthanol Cyclohexanone Chloroform Xylene
Hexanol Methyl ethyl Ketone Methyl Chloride Ethylen diamine
Cyclohexanol Metil isobuthyl Ketone Chlorethylene Ethanol amine
Isoamilic Alcohol Caprolactame Dichloro ethylene Diethyl amine

• Hydrophilic membranes: PVA, PAN...

 Ion exchange process

1. The ion exchange is the exchange of equivalent numbers of

similarly charged ions,between an immobile phase, which may be
a crystal lattice or a gel, and a liquid surrounding the immobile phase.
2. If the exchanging ions are positively charged, the ion exchanger is
termed cationic,and anionic if they are negatively charged.
3. The rate at whichions diffuse between an exchanger and the liquid
is determined, not only by the concentration differences in the two
phases, but also by the necessity to maintain electroneutrality in both
phases.
4. Ion exchange is not a membrane process but it is used for product
of protein isolates of higher concentration than obtainable by
membrane concentration.
5. Fractionation may also be accomplished using ion exchange
processing.
1. It relies on silica based adsorb charged particles at
either end of the pHscale.
2. The design can be a batch type, stirred tank or
continuous column. The column ismore suitable for
selective fractionation.
3. Whey protein isolate (WPI), with a 95%
proteincontent, can be produced by this method.
4. Following adsorption and draining of thedeproteined
whey, the pH or charge properties are altered and
proteins are eluted.
5. Proteinis recovered from the dilute stream through
UF and drying. Selective resins may be usedfor
fractionated protein products or enriched in fraction
allow tailoring of ingredients.
Application examples of ion exchange
membrane
•Production of High Purity Chemicals
•Production of Ultra Pure Water
•Food and pharmaceutical
•Demineralization of Cheese Whey
•Demineralization of Organic Acids and Amino Acids
•Demineralization of Natural Extract
•Demineralization of Poly-saccharide
•Demineralization and Purification of Pharmaceutical
Intermediate
Environmental conservation
•Desalination of Leachate
•Removal of Nitrate from Under-Ground Water
Others
•Production of Salt from Sea water
•Production of Drinking Water from Brackish Water
•Desalination of Deep Sea Water
•Acid Recovery from Waste Acid
 My Philosophy for MT-II

“Problematic paper, but solutions to the problems lies in theory”

“The only way to understand theory is reading & relating it to

reality and questioning”

“The only way to solve problems is by exercising solution to

problems”