1

BLEACHING WITH PERACETIC ACID

By Muskkan (20110045), Manpreet Singh (20110041), Bhagwan Singh Rathore (20110017)

Preparatory and Coloration of Textiles, Dr. B. R. Ambedkar National Institute of Technology,
Jalandhar, Punjab, India

INTRODUCTION

Today, it would be more truthful to say that bleaching of textile materials is more of an art or
skilled work rather than a mere scientific exploration. Bleaching is a critical part of textile
preparation. The prime purpose that bleaching serves is to enhance the final appearance of the
material.
The definition of bleaching given by the Terms and Definitions Committee of the Textile Institute
is-
The procedure, other than by scouring only, of improving the whiteness of textile material, by
decolorizing it from the grey state, with or without the removal of natural colouring and/or
extraneous substances (Chesner L & Woodford G.C, 1958). The pigments in natural and synthetic
fibers are destroyed in bleaching during heat-setting processes. It should be made sure that
bleaching should proceed without degrading the fiber to any appreciable extent.
This review is concerned with peracetic acid, a peroxycarboxylic acid which is more often used in
the textile industry. It majorly collects information and articles on peracetic acid to create a
chronological picture of its uses. European textile mills are now using peracetic acid in TCF (totally
chlorine free) bleaching (Guersy & Dayioglu, 2000; Scarborough & Mathews, 2000; Wurster,
1992). Temperature, pH and concentration of peracetic acid and its dwell time plays a major role in
formation of peracid. Figure 1 displays the structure of peracetic acid.

Figure 1: Alkyl or aryl per- or peroxy-carboxylic acids

(https://images.search.yahoo.com/search/images?p=peracetic+acid&fr=mcafee&type=E211US885G0&imgurl=http%3A

%2F%2Fen.wikipedia.org%2Fwiki%2FSpecial%3AFilePath%2FEthaneperoxoic_acid_200.svg)
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IMPORTANCE

Peracetic acid, due to its versatile chemical system has found its significance in textile processing
segments. It is a well established oxidant with bleaching properties which can be usefully used to
replace sodium hypochlorite and sodium chlorite. The acid is used frequently due to its specificity
of attack. Higher whiteness with lower chemical change can be achieved. The easy commercial
availability of the chemical has lowered its cost. Peracetic acid is commercially available for textile
bleaching in 5% and 15% solutions (Gursoy, N., Dayioglu, H. 2000). Major PAA manufacturing
industries are Solvay chemicals (Belgium), Peroxy chem. (US), Envirotech chemical services (US),
Evonik industries (Germany), Kemira chemical (Finland), Ecolab (US) and Aditya Birla Chemicals
(India)(Sharma N, Bhardwaj N K & Prashad Singh R B, 2020) .Two methods are proposed for
Peracetic acid bleaching:
● Liberation of oxygen that takes place in acidic medium
● Liberation of perhydroxyl radical that occurs in neutral and alkaline medium

PROPERTIES OF PERACETIC ACID:

Peracetic acid is the mono-acetyl derivative of hydrogen peroxide. It is prepared by adding 30%
hydrogen peroxide (one part by volume) to acetic anhydride (three parts by volume) in the presence
of a catalytic amount of sulphuric acid ( 1 %). (Prabaharan M, Nayar RC, Rao JV. 2000)[3].

(1)

Spontaneous decomposition takes place at higher temperatures and pH levels to give acetic acid
and oxygen [Eqn 2].

(2)
Heavy metals can also cause decomposition specially in the presence of single-transition ions [Eqn
3].

(3)
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Spontaneous decomposition and hydrolysis of PAA are undesirable since they lead to the formation
of products which have no bleaching action. Eqn 4 shows the reaction occurring when PAA is used
for bleaching ( Križman P , Kovač F, Tavčer P 2005) [4].

(4)

Epoxidation of double bonds present in the unwanted coloured compounds results in the bleaching
action of peracetic acid. It is water white in color with 36-40% strength. The only precautions to be
taken in handling are to keep it in a clean cool place in the vented containers supplied, and to keep
naked lights away from the storage vessel (Chesner L & Woodford G.C, 1958). .
Table I displays the physical and chemical properties of peracetic acid (Tieckelmann RH, Kurschner
LM, Gurunthan SS, Penn RL, Swicegood JT 1992).

Table I: Physical and Chemical properties of peracetic acid

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Process Parameters:

Process Parameters are the key variables that affect the production process. In order to obtain
effective execution of the process its parameters should stay under continuous control. These
parameters mainly include pH, temperature, time, concentration.
In Bleaching, these parameters help to determine the following three quality attributes:

● Whiteness: Also known as bleaching, is the percent of total reflection versus a white
standard (Datacolor/ Berger).

● Yellowness: Yellowness is measured on a scale of yellow to blue where a positive number

denotes yellowness, a negative number denotes blueness and zero denotes neutrality.

● Degree of Polymerisation: The degree of polymerization (DP) values were determined

according to the modified cuoxam method described by Buecbs and Mertens.

The standard bleaching conditions were 30 minutes dwell time at 60°C, pH 6.5 and 2.5 g/L
Peracetic Acid. The DP value of the greige fabric was about 2600 ( Steiner N 1995).

How pH and Temperature affects Bleaching?

pH
Peracetic acid has a single acidic proton with pKa of 8.2 at 25°C (Koubek et al., 1963). The reactive
species in bleaching is the peracetate ion. As is evident from Eqn 1-4, formation of acetic acid
during reaction causes gradual drop in pH.

Figure 2 shows the effect of pH on whiteness values.

The maximum bleaching effectiveness is achieved in the
range of initial pH of between 7 to 7.20. This can be
explained by the fact that the liberation of perhydroxyl
ions, which.are mainly responsible for bleaching, can
occur only in neutral and alkaline media (Prabaharan M,
Nayar RC, Rao JV. 2000). At pH of 6-7, more effective
removal of mineral impurities & metals and better
penetration of liquor occurs in cellulosic materials.

Figure 2: Effect of pH on the WI of bleached colton and

peracetic acid decomposition during bleaching (Rucker J W 1989) .
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Temperature:

Peracetic acid decomposition increases with increase in temperature which facilitates rapid
availability of perhydroxyl ions for bleaching. The increase in bleaching effectiveness with
temperature is thus counteracted by decreasing peracetic acid stability, and a maximum in
whiteness is thus obtained at 50℃(Rucker J W 1989). Figure 3 depicts the effect of temperature
on Whiteness Index and decomposition of peracetic acid during bleaching.

Figure 3: Effect of temperature on the WI of

bleached cotton and peracetic acid decomposition
during bleaching.

Increasing the temperature is accompanied by(Abdel-Halim E S, & Al-Deyab S S 2011) :

1) Rapid decomposition rate of peracetic acid
2) The percent loss in fabric weight is increased marginally
3) The Whiteness Index of bleached samples is improved
4) Increment in the elongation percentages, carboxyl content and carbonyl content and
5) Acceptable decrement in the tenacity
 6

Applications of Peracetic acid:

Most of the traditional Peracetic acid applications are for industrial chemical synthesis. For more
than a few decades Peracetic acid has been proven to be an effective bleaching agent. In the
textile industry it is used to achieve a high degree of whiteness without degrading the cotton
fabric. Abdel-Halim and Al-Deyab (2011) reported that cotton fabrics were bleached with lab
prepared PAA, bleaching was carried out at low temperature and also studied the different
parameters that could affect the bleaching process. Results obtained show that fabric bleached an
acceptable whiteness index with slight loss of tensile strength (Sharma N, Bhardwaj N K &
Prashad Singh R B, 2020).

Further Peracetic acid has been successfully utilized in food processing, brewings, healthcare,
textile and paper industries (Kitis, 2003) and treatment of wastewater. Primarily in Europe, it is
used in disinfection and cleaning operations. It is a very strong oxidant as well as reductant which
performs under acidic conditions.

Environmental Relevance of Peracetic

Peracetic acid is a biodegradable chemical. It is an environment friendly bleaching agent. The

Figure 4 given below shows the utilization of Peracetic Acid in various sectors (Sharma N,
Bhardwaj N K & Prashad Singh R B, 2020).

Figure 4: Use of Peracetic Acid in different sectors

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The rapid utilization of Peracetic Acid in sludge and its fully biodegradable residues do not
interfere with sludge humus improvements in soil constitution through increased cohesion, better
crumble structure, and, often, an increase in water retention (Fraser et al., 1984). The essential
geochemical cycles performed by microorganisms in soil are not affected which includes organic
carbon, nitrogen, and sulphur.
However, the acetic acid contributes slightly to higher BOD levels of the wastewater in the order
of magnitude of 20-40 mg BOD/L. Comparing this number to the base load of COD/ BOD
typically present in a textile plant discharge (several hundreds of ppm), shows that this is not a
major issue (Steiner N 1995).

METHODS OF SYNTHESIS OF PERACETIC ACID

Mostly the peracetic acid can be synthesized by the reaction of hydrogen peroxide with acetic acid .
It also can be synthesized by the reaction of hydrogen peroxide with tetra-acetylethylenediamine
(TAED). The commercial availability of an equilibrium solution has lowered the price of peracetic
acid.
Similarly Peracetic acid can be synthesized by different types of different mechanisms. Three out of
them mentioned below -

1. By the reaction of Hydrogen and Acetic Acid:

This method is mostly used in industries of production of Peracetic acid.

Peracetic acid can be formed by the reaction of Hydrogen peroxide and Acetic acid in the presence
of a strong acid catalyst. Since the reaction is a reversible chemical reaction .

Process:

● Chemicals Used : Hydrogen peroxide (H2O2)

Acetic acid (CH3COOH)
Sulphuric acid (H2SO4)

● Procedure
Firstly the Sulphuric acid is added in acetic acid in a flask.
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Then 30% of peracetic acid is added after some time in the flask and mixed homogeneously. The
ratio of acetic acid and hydrogen
peroxide to be added for the reaction is 3:2 . The solution stirrer for some time and then after some
time the Peracetic acid can be obtained .

● Mechanism

Figure 5: Mechanism of formation of peracetic acid by hydrogen peroxide and acetic acid.
(https://images.app.goo.gl/xMcbKLMJ5kGjynRk8)

● Graphical Representation of formed Peracetic Acid

Figure 6: The formation rate of peracetic acid at different

temperatures. The amount of sulfuric acid catalyst in the
reaction mixture was 6 wt-%.
 9
(https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FTh
e-formation-rate-of-peracetic-acid-at-different-temperature-The-amount-of-sulfuric_fig2_25167279
7&psig=AOvVaw0DqzlY-wb7W9lUaKv_y2Ij&ust=1649863448600000&source=images&cd=vfe
&ved=2ahUKEwjj-8K36o73AhXdR2wGHbCCC5QQjRx6BAgAEAk)

2. By the Reaction of Hydrogen Peroxide and Acetic Anhydride

Peracetic acid also can be formed by the reaction of hydrogen peroxide and acetic anhydride in the
presence of an alkali medium catalyst like sodium hydroxide or EDTA. A by-product of acetic acid
is also formed in this process. This process occurs at room temperature. Time taken for maximum
synthesis of peracetic acid is 4 hours. Maximum yield of the process is 80% (S.R. KARMAKAR ,
1999). This method is a rarely used method because the excess of acetic anhydride may cause an
undesirable side reaction to yield highly explosive product diacetyl peroxide .

Mechanism

Figure 7: Mechanism of Process Hydrogen Peroxide with Acetic Anhydride

(S.R. KARMAKAR , 1999)

3. By the Reaction of Hydrogen Peroxide and TAED

The other most commonly used method of synthesis of Peracetic acid is the reaction of hydrogen
peroxide with Tetra-acetylenediamine (TAED). TAED is a bleaching activator and mostly used in
bleaching of cellulosic fiber.
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Process

Tetra-ethylenediamine reacts with hydrogen peroxide ion to form a new product DAED
(di-acetyleneethylenediamine) with Peracetic acid ion. Now peracetic acid anion react with
hydrogen peroxide at the PH of 8-9 and make an equilibrium with free peracetic acid. This peracetic

acid reacts with its own per anion and forms active oxygen molecules . These oxygen molecules act
as a bleaching agent in bleaching of peracetic acid(Long X, Xu C, Du J, Fu S, 2013).

Figure 8: Equilibrium concentration of peracetic acid and ion with pH

(https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2F
a-The-perhydrolysis-reaction-of-TAED-b-bleaching-performances-of-H2O2-H2O2-AED-and_fig
3_330348265&psig=AOvVaw3BZtXWUxXmfTtWo4C0-TnS&ust=1649864391224000&source
=images&cd=vfe&ved=2ahUKEwj2loD57Y73AhWkRWwGHU9tCioQjRx6BAgAEAk)
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Mechanism

Figure 9: Mechanism of Reaction Hydrogen Peroxide and TAED

(S.R. KARMAKAR , 1999)

ADVANTAGES AND PROBLEMS ASSOCIATED WITH DIFFERENT

MANUFACTURING PROCESSES

Besides per acetic acid there are many more methods of bleaching with different bleaching
agents:
● Bleaching with Sodium Chlorite(NaClO2)
● Bleaching with Sodium Hypochlorite(NaOCl)
● Hydrogen Peroxide(H2O2)

1. Bleaching with Sodium Chlorite (NaClO2)

Bleaching with sodium chlorite is most efficient at pH 4.02.The temperature during this
bleaching is 40-80℃ .Sodium Chlorite bleaching has several advantages:
● Under recommended conditions ,high whiteness is achieved without degradation
of cellulose.
● It can be applied not only to cotton but also to other textile materials and their
mixtures such as on rayons etc.
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● Traces of irons do not catalyze bleaching reactions and degradation of cellulose

does not take place.
● Rinsing after bleaching seizes the bleaching reactions and does not bring
degradation of cellulose since no fiber substantive alkali is used.

Problems associated with Sodium Chlorite Bleaching:

● As sodium chlorite is very corrosive so it is necessary to use ceramic or plastic
Material for this bleaching process.
● Choice of a suitable method of activation of bleaching agent.
● Design of the equipment to be used during this bleaching process.
● Selection of corrosion resistant materials for bleaching plant
Construction.

2. Bleaching with Sodium Hypochlorite (NaOCl)

Sodium Hypochlorite, the active ingredient in chlorine bleach has a variety of uses and is
an
Excellent disinfectant/antimicrobial agent. Sodium hypochlorite has a relative density of
1.1. As a bleaching agent for domestic use it usually contains 5% sodium hypochlorite.

Advantages of using this Hypochlorite bleach are:

● Sodium hypochlorite can penetrate into the fabric more thoroughly as compared to
bleaching powder,therefore less time in bleaching is required in case of sodium
hypochlorite.
● This hypochlorite being a sodium salt of hypochlorous acid does not require any
dissolving arrangement and is ready for immediate use as compared to bleaching
powder that partially dissolves in H20.
● Due to its bleaching power at low temperatures and low cost ,this mainly used in
Textile and laundry factories.
● It is a very cheap oxidiser, with considerably more brilliant white effects than
other peroxide bleaches.
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More stable the solution of hypochlorites the less readily it bleaches the textile and any
circumstances which makes the solution less stable in turn increases the bleaching effect.

Problems associated with Sodium Hypochlorite Bleaching:

● On addition of alkali increases the stability of the bleach therefore decreases its
bleaching effect.
● Sodium hypochlorite or bleaching powder provides more damage to cellulose
than calcium hypochlorite because of the swell up action of NaOH which forms in
solution.
● The formation of high toxic chlorinated organic by-products(AOX) during the
process of this bleaching,have limited its use over recent years as these
compounds serve as a potential hazard to drinking water resources when
discharged.

Table III shows the data of total AOX and CHCl 3 concentrations in spent hypochlorite bleach
liquids and rinse solutions.

Table III: AOX and CHCl3 concentrations in bleaching liquids (ppm)

1. (Steiner, N. (1993)

NaOCl Stage H2O2 Stage 1. Rinse 2.Rinse

AOX 105 19 5 2

CHCl3 11.5 11.5 0.3 0

In many countries in Europe very strict discharge limits are already in place, for example:
Germany:0.5 ppm or 9 max. 10g/h ,making the use of hypochlorites almost impossible without
high cost wastewater treatment .
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For that reason,the textile industry seeks environment safe alternatives for hypochlorites which
provide better brightness under similar process conditions.

3. Hydrogen Peroxide (H2O2)

Hydrogen peroxide is established as a bleaching agent and used increasingly in bleaching of

cotton as it offers following benefits over older Hypochlorites processes-
● Easier to handle than hypochlorites
● Enables processing to take place rapidly with consequent reduction in labour cost

Advantages Associated with Hydrogen Peroxide Bleaching:

● It decomposes to give oxygen and water only,best suited to applications where the effect
on the environment of effluents has to be minimal.
● In chemical pulp bleaching,this bleaching agent is widely used as a reinforcement to
existing bleaching stages.
● Alkaline extraction with peroxide include improvement of environmental parameters
such as COD(Chemical oxygen demand), BOD (Biological oxygen demand),
AOX(Adsorbable organic halogen)

Problems Associated with Hydrogen Peroxide Bleaching:

Though H2O2 is a powerful bleaching agent but is has also many problems accompanied with it :
● H2O2 stables at pH 1-3;but at highly alkaline pH 11.5 -13 it has least stability.its bleaching
action takes place at pH around 10.5 due to accumulation of per hydroxyl ions in
bleaching bath.but at weak alkaline media it does not produce any whitening effect as
results causes the degradation of cellulosic material.
● ‘Catalytic damage’ occurs during h2o2 bleaching of cotton fabrics resulting in small spots
of unevenly dyed fabric or the formation of holes sometimes appearing.
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● Peroxide residues in effluents(which remain left after bleaching ) to biological treatment

are harmful to microbial activity there so must be avoided which can be done by destroying
peroxide residues by reacting it with SO2.

APPLICATION ON COTTON

Peracetic acid bleaching is a chlorine free and most importantly Environmentally compatible
process . And mostly used for less degradation and superior whiteness .Also no extra chemicals
required during the process of bleaching. It is a colorless solution having 35-40%. Only 3% solution
of peracetic acid is enough for bleaching. It was observed in the last some time that in the course of
peracetic acid dissociation, acetate free radical and hydroxyl free radicals are released . These
radicals do the bleaching process and decompose the coloring materials into textiles. The bleaching
is also done by only peracetic acid because this process of bleaching is also done on the neutralized
zone pH , so there is no requirement to add any acid or alkali in the solution to maintain the pH. But
for the maximum whiteness obtained at pH 8 , a small amount of alkali should be added.

Method of Cotton Bleaching

Materials A desized scoured cotton fabric

Peracetic acid , as a 15% equilibrium solution
Sodium carbonate

Process

First a bleaching bath is prepared with the required volume of water , at a material of liquor ratio
1:20 by adding the peracetic acid solution. The PH of the solution is maintained by the addition of
sodium carbonate. Then the fabric is added to the bleaching solution and the temperature of the bath
is raised upto 40°C for 10 min. After 10 min, temperature of the bath is raised slowly but
continuously at the rate of 5°C per min, upto bleaching temperature (80°-85°C). Now the bleaching
 16
is done at this temperature for 40 min. After the compilation of the bleaching process , the fabric is
taken out from the solution . fabric is washed thoroughly with the hot water and Dried in an
ambient condition.
Then the whiteness and the damage on the fabric was measured .

PROCESS PARAMETERS

Effect of pH in Cotton Bleaching

The maximum bleaching effect on cotton fabric is obtained at the pH of 8.2 which corresponds to
the pk-value of the peracetic acid. Also very less or negligible degradation of cotton fabric occurs,
if pH is maintained in the range of 6-8.2. Below the pH of 6 bleaching can be done but the
brightness of the cotton fabric significantly decreases. At a pH of 9 a slightly higher brightness is
obtained but at the expense of DP value(Value of Degree of Polarization). Due to decomposition of
the peracetic acid to O2 and CH3COOH. No bleaching can be done at the higher pH of 9 , because
of the decomposition of the peracetic acid. The optimum pH range for the Peracetic acid bleaching
stage is around 6-7.

Figure 10: Effect of pH on Brightness

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Effect of Temperature in Cotton Bleaching

Basically, onn the cotton fabric, the peracetic acid bleaching can be done in the range of
temperature of 20°C–80°C. At the temperature of less than 20°C no bleaching will happen. And
above the temperature of 80°C, more degradation of cotton fabric is observed, so no bleaching takes
place. So the effect of temperature on bleaching and peracetic acid was evaluated over the range of
20°–80°C. As expected, the brightness of the cotton fabric increases with the increasing
temperature. To avoid fiber damage, the preferred temperature range for peracetic bleaching is
50°–80°C.

Figure 11: Effect of temperature on bleaching

Effect of Dwell Time in Cotton Bleaching

Dwell time is also utmost important for any process. Typically , the bleaching time should be as
short as possible. Also it can be seen that best bleaching brightness is obtained on cotton fabric after
20 min. In general 60–80 min is preferred dwell time for peracetic acid bleaching for cotton fabrics.
In the preferred dwell time bleaching brightness increases with increasing dwell time. If the dwell
time is more than 80 min, then more damage on the fabric will happen.
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Figure 12: Effect of Bleaching Time on Brightness of Fabric

Effect of Peracetic Acid Concentration

Peracetic acid does not produce any toxic by-product in bleaching reactions and it is also less
corrosive. It is also a chlorine free bleaching agent. So the higher amount of peracetic acid
concentration is not so harmful for bleaching textile as well as environment. As usual, the higher
concentration of bleaching agent proportionally increases the brightness of the cotton fabric. It is
also observed that even at relatively high peracetic acid concentration , very less or negligible
degradation on cotton fabric was observed.

Figure 13: Effect of PAA concentration on brightness of fabric

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Effect of Heavy Metals

To determine the effect of metal, which of the mostly fourth period transition metals forms the
catalytically complex. So, only these metal effects are evaluated. Heavy metals are a common
problem in all types of bleaching, which often leads to catalyst damage on the fabric. It seems like
to also seen that in presence of fourth period transition ions, there is no any damage on the cotton
Fabric as well as no loss in the brightness of the cotton fabric. But with other metal ions whiteness
also decreases and cotton fabric is also slightly damaged.

Figure 14: Effect of Iron and Other Metal on the Brightness of Fabric

STABILITY OF PERACETIC ACID

On storage all Peracetic Acid solutions tend to decompose to some extent. Peracetic acid is an
example of organic peroxide that contains weak peroxide bonds. These bonds break under certain
appropriate conditions and supply free radicals. Though these free radicals play an important role in
the bleaching process, the potential instability is minimized by adding some amount of stabilizers.
The phosphates, quinolates do stabilize Peracetic Acid.
 20

The chemicals used for product stabilization can also be used for bleach bath stabilization for
example., Pyrophosphates, hexametaphosphates and phosphonates (Hickman W S, 2000 ). The
Table II gives an indication of the stability of a dilute solution of peracetic acid of similar strength
to that used in textile bleaching(Chesner L & Woodford G.C, 1958).

Table II: Stability of Dilute Peracetic Acid Solution

(Initial conc. of soln. at 20℃. 3 g. of approx. 37% peracetic acid per litre; pH 2.8)

EQUILIBRIUM OF PERACETIC ACID

Peracetic acid is a strong oxidant with a reduction potential of 1.06 V , which is similar to that
traditional bleaching agent, chlorine dioxide (Journal of Molecular Catalysis A: Chemical).
Equilibrium peracetic acid here denotes the mixture of peracetic acid , hydrogen peroxide, acetic
acid and water in the chemical equilibrium. Or we can say that all four components present at some
specific time , known as equilibrium time.
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Equilibrium peracetic acid is usually produced from the reaction of acetic acid and aqueous
hydrogen peroxide solution. This reaction is reversible and thus an equilibrium mixture of reactants
and products is obtained.

Figure 15: Equilibrium Reaction for Peracetic Acid

(https://images.app.goo.gl/h8EXzF6wdThuvsjH7)

The rate at which the equilibrium is achieved can be accelerated by adding a strong acid catalyst.
Also the concentration of equilibrium peracetic acid varied with the hydrogen peroxide and acetic
acid concentration(Unis, M.M.A., (2010)).

Experiment for Equilibrium

Before the reaction , a certain amount of acetic acid and sulphuric acid is added in a flask. Then a
certain volume of 30% hydrogen peroxide is added and all chemicals are mixed homogeneously.
The initial volume ratio of acetic acid and 30% hydrogen peroxide was 3:2. The solution is to keep
it at a constant temperature in the water bath. It takes hardly 6 to 7 hrs to establish equilibrium.
Samples were taken out from the solution and quickly analyzed in accordance. The kinetic
constants were obtained by fitting experimental data by a simplex optimization method. Each
datum was the average result of at least a double test.

Mechanism

The mechanism of equilibrium peracetic acid synthesis and hydrolysis have been proposed . It was
found that the reaction did not involve the dissociation of the O–O bond in initial hydrogen
peroxide. In the mechanism of EPAA two methods are suggested to set an equilibrium a and b.
Mechanism a consists of the hydrogen peroxide to the carbonyl carbon for the formation of a
tetrahedral transition state with the subsequent loss of a water molecule. While mechanism b
 22
consists of an acidic medium for the activation of carbonyl carbon and the subsequent position of
the hydrogen peroxide and the loss of a water molecule.

Figure 16: Detailed Mechanism of Equilibrium Reaction

(Unis, M.M.A., (2010))

It can seened that the mechanism b is more preferred than the mechanism a because no acid
catalyst exits in the reaction system. So the forward and reverse process may be described by the
detailed scheme containing the moving of electrons (Figure 16).

Determination of kinetic constants

Equilibrium equation for peracetic acid is shown in Figure 15.

At the equilibrium, multiply of concentration of reactants and product is proportional to each other .
Means,
K1 [H2O] [CH3COOOH] = K2 [CH3COOH] [H2O2]

Kobs = [H2O2] / [CH3COOOH] = K1 [H2O] / K2 [CH3COOH]

 23

Koverall = [H2O2] [CH3COOH] / [CH3COOOH] [H2O]

So after solving above equation we can get:

Koverall = K1 / K2

The rate of hydrolysis (K2 )of peracetic acid can be determined:

Kobs =K1 [H2O] – K2 [CH3COOH]

Kobs = Kobs . K2 [CH3COOH] + K2 [CH3COOH]

K2 = Kobs / (1+Kobs )[CH3COOH]

Similarly the rate of formation of peracetic acid can be determined:

Kobs = K1 [H2O] + K2 [CH3COOH]

Kobs = K1 [H2O] + Kobs / (1+Kobs )

On solving this we can write:

K1 = K obs. Kobs / (1+Kobs )[H2O]

EVALUATION OF STRENGTH OF PERACETIC ACID

The first industrial of peracetic acid was as a bleaching agent heat set nylon.however there is loss of
10% loss in strength not usually serious in view of high tensile strength of nylon.Mainly the
chemical damage that occurs bleaching mayb due the attack by free radicals produced from both
H2O2 and CH3COOH, thus:
 24

Figure 17: Formation of Free Radical from H2O2 and CH3COOH

2. (Chesner, L (1963))

A method of preventing or lowers of strength losses in bleaching,is to add either a oxalic acid or
diethylenetriaminepenta-acetic acid(DTPA).If the nylon contains traces of copper picked up during
processing,the benefits get from these complexing agents are further getting high.

On the other hand,a very special case of the bleaching of Leavers lace,that may contain up to 100
p.p.m of copper as due to its method of production,no advantage has been offered by sequestering
agents and the only safe bleaching agent is sodium chlorite.

This is illustrated in Table IV given below:

Table IV: Bleaching of leavers lace containing 47.4 p.p.m of Copper

(Chesner, L (1963))

Treatment Loss in strength(%)

3g/l. peracetic acid 44.0

3g/l. peracetic acid +0.5 g/l. oxalic acid 30.0

3g/l. peracetic acid+0.18 g/l. DTPA 30.0

1g/l. sodium chlorite 3.5

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CONCLUSION

This review reminds the reader that Peracetic Acid is a very powerful oxidant with
bleaching, antimicrobial and biocidal properties which can be usefully used, on
environmental grounds, to replace both sodium hypochlorite and sodium chlorite.
The objective was twofold:
● Evaluate efficacy of Peracetic acid to bleach cotton.
● Determine application parameters, i.e., concentration, time, temperature and
pH.
It is proven to be viable and as an industrial chemical is easily available. It can safely be
introduced to an existing process design as it does not form any toxic by-products. Higher
whiteness values with less fiber damage is achieved.
Few of the risks and disadvantages associated with Peracetic Acid is with its
● preparation, storage and transport
● use under neutral bleaching conditions would dictate a prescour to remove
seeds and motes.
● high cost, which is partly due to limited production capacity worldwide.
It can nevertheless be safely used for bleaching cotton fabric partially dyed with azoic and
vat dyes, some of which are sensitive to the more widely used bleaching agents (Chesner L
& Woodford G.C, 1958). ). The quality of the bleached material is in line with that of
hydrogen peroxide bleaching.
 26

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