Establishment of an activated peroxide system for low-temperature cotton bleaching using N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride

Article abstract of DOI:10.1016/j.carbpol.2014.11.054

Cotton bleaching is traditionally carried out in strongly alkaline solution of hydrogen peroxide (H₂O₂) at temperatures close to the boil. Such harsh processing conditions can result in extensive water and energy consumptions as well as severe chemical damage to textiles. In this study, an activated peroxide system was established for low-temperature cotton bleaching by incorporating a bleach activator, namely N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) into an aqueous H₂O₂ solution. Experimental results showed that the TBBC-activated peroxide system exhibited the most effective bleaching performance in a pH range of 6-8 which could be approximated by adding sodium bicarbonate (NaHCO₃). The TBBC/H₂O₂/NaHCO₃ system led to rapid bleaching of cotton at a temperature as low as 50°C. In comparison with the hot alkaline peroxide bleaching system, the TBBC/H₂O₂/NaHCO₃ system provided cotton fabric with an equivalent degree of whiteness, higher degree of polymerization, and slightly lower water absorbency. The new activated peroxide system may provide a more environmentally benign approach to cotton bleaching.

Full text of DOI:10.1016/j.carbpol.2014.11.054

Carbohydrate Polymers 119 (2015) 71–77
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Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol
Establishment of an activated peroxide system for low-temperature
cotton bleaching using
N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride
Changhai Xua,c,∗, David Hinksb,c,∗, Chang Suna,c, Qufu Weia,c
a Key Laboratory of Eco-textiles, Ministry of Education, College of Textiles and Clothing, Jiangnan University, Wuxi, Jiangsu 214122, China
b Department of Textile Engineering, Chemistry and Science, College of Textiles, North Carolina State University, Raleigh, NC 27695, USA
c International Joint Research Laboratory for Advanced Functional Textile Materials, Jiangnan University, Wuxi, Jiangsu 214122, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Cotton bleaching is traditionally carried out in strongly alkaline solution of hydrogen peroxide (H2O2)
at temperatures close to the boil. Such harsh processing conditions can result in extensive water and
energy consumptions as well as severe chemical damage to textiles. In this study, an activated peroxide
system was established for low-temperature cotton bleaching by incorporating a bleach activator, namely
N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) into an aqueous H2O2 solution.
Experimental results showed that the TBBC-activated peroxide system exhibited the most effective
bleaching performance in a pH range of 6–8 which could be approximated by adding sodium bicar-
bonate (NaHCO3). The TBBC/H2O2/NaHCO3 system led to rapid bleaching of cotton at a temperature as
low as 50 ◦C. In comparison with the hot alkaline peroxide bleaching system, the TBBC/H2O2/NaHCO3
system provided cotton fabric with an equivalent degree of whiteness, higher degree of polymeriza-
tion, and slightly lower water absorbency. The new activated peroxide system may provide a more
environmentally benign approach to cotton bleaching.
Received 7 October 2014
Received in revised form
13 November 2014
Accepted 21 November 2014
Available online 3 December 2014
Keywords:
Cotton
Peroxide bleaching
Activated peroxide system
Low-temperature bleaching
N-[4-
(Triethylammoniomethyl)benzoyl]butyrolactam
chloride
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
bleached cotton fibers. Hence, there is currently a strong demand
for establishing an alternative approach to cotton bleaching.
Raw cotton contains natural yellowish impurities which can
significantly detract from the inherent whiteness of cotton cellu-
lose. Bleaching is therefore required in preparation of cotton-based
textiles to remove these impurities. Hydrogen peroxide (H2O2)
is the most widely used oxidant for cotton bleaching in the tex-
tile industry due to its environmental friendliness and low costs
(Zeronian & Inglesby, 1995). However, cotton bleaching with H2O2
is often carried out under extremely alkaline conditions at the
boiling temperature. Such harsh processing conditions not only
cause extensive energy consumption, but also severe chemical
damage to cotton fibers. Additionally, when the bleaching process
is completed, a neutralization process is required to remove the
residual alkali by adding acetic acid, and a large amount of water
is also required for washing to remove the residual H2O2 from the
A low-temperature bleaching process can be achieved with an
activated peroxide system which is established by incorporating a
so-called bleach activator into an aqueous H2O2 solution (Hofmann,
Just, Pritzkow, & Schmidt, 1992). A peracid is in situ generated by
reaction of bleach activator with H2O2 (this reaction is also called
perhydrolysis), which has an oxidative potential higher than H2O2
and is responsible for cotton bleaching at lower temperatures. Acti-
vated peroxide systems nowadays have been widely applied for
domestic laundering for removal of coloring contaminants from
textiles (Milne, 1998). Since the beginning of the 21st century,
activated peroxide systems have been increasingly considered in
the textile industry as a promising approach to low-temperature
cotton bleaching, in which tetraacetylethylenediamine (TAED) is
mostly used as a bleach activator because of its commercial avail-
ability and environmental benignity (El-Shafie, Fouda, & Hashem,
2009; Hebeish et al., 2009; Long, Xu, Du, & Fu, 2013; Scarborough
& Mathews, 2000; Shao, Huang, Wang, & Liu, 2010; Xu, Long, Du,
& Fu, 2013). However, TAED has poor water solubility which limits
its application in industrial textile bleaching. In addition, the TAED-
activated peroxide system is not very effective at temperatures
below 70 ◦C. Therefore, much effort has been dedicated to finding a
∗
Corresponding authors at: College of Textiles and Clothing, Jiangnan University,
1800 Lihu Avenue, Wuxi, Jiangsu 214122, China. Tel.: +86 510 85326031;
fax: +86 510 85912009.
E-mail addresses: changhai xu@jiangnan.edu.cn (C. Xu), dhinks@ncsu.edu
(D. Hinks).
http://dx.doi.org/10.1016/j.carbpol.2014.11.054
0144-8617/© 2014 Elsevier Ltd. All rights reserved.

72
C. Xu et al. / Carbohydrate Polymers 119 (2015) 71–77
100 mL of DI water. Triton X-100 (0.1 g) and Prestogen N-D (0.1 g)
were also added to the solution as bleaching auxiliaries. A combi-
nation of TBBC and H2O2 in a molar ratio of 1:0 to 1:10 was added
to the solution under stirring to form the TBBC-activated peroxide
system for use as a bleach bath.
Scheme 1. Chemical structure of TBLCs (n = 1–5).
2.3. Cotton bleaching
new bleach activator capable of establishing a more effective acti-
vated peroxide system (Abdel-Halim & Al-Deyab, 2013; Cai & Evans,
2007; Cai, Evans, & Smith, 2001; Hashem, El-Bisi, Sharaf, & Refaie,
2010; Ibrahim, Sharaf, & Hashem, 2010; Wang & Washington, 2002;
Wang, Li, Zhu, & Yang, 2014).
A sample of cotton fabric (10 g) was immersed in the bleach bath.
Bleaching was heated to and maintained at a target temperature
(e.g. 25, 50, 75 and 100 ◦C) for various time periods from 0 to 60 min.
When bleaching was completed, the bleached cotton fabric was
rinsed thoroughly in water and dried under ambient conditions.
Three replicates were run for each bleaching experiment.
N-[4-(Triethylammoniomethyl)benzoyl]lactam
chlorides
(TBLCs) are a novel class of quaternary ammonium compounds
as given in Scheme 1, which are designed and tailored for use
as bleach activators (Lee, Hinks, Lim, & Hauser, 2010). It is
assumed that the cationic group provides a good water sol-
ubility of TBLCs, and the lactam group be cleaved by H2O2
2.4. Measurements of cotton fabrics
2.4.1. Degree of whiteness
The degree of whiteness of bleached cotton fabric was measured
using the CIE whiteness index (WI) according to the AATCC Test
Method 110-2010. The measurement was performed on a Data-
color SF 600× spectrophotometer (Datacolor International, USA)
with the following settings: illuminant D65, large area view, spec-
ular included and CIE 1964 Supplemental Standard Observer. Each
sample was folded twice to give an opaque sample with four plies,
and measured four times with 90◦ rotation between measurements
to give an average value.
to generate
a peracid, namely N-(4-carboperoxybenzyl)-N,N-
diethylethanaminium chloride (CPBDC) as demonstrated in
Scheme 2. N-[4-(Triethylammoniomethyl)benzoyl]caprolactam
chloride (TBCC) is a prototype of TBLCs which was firstly applied
for low-temperature bleaching of cotton fabric (Gursoy, El-Shafei,
Hauser, & Hinks, 2004; Gursoy, Lim, Hinks, & Hauser, 2004; Lim,
Gursoy, Hauser, & Hinks, 2004; Lim, Lee, Hinks, & Hauser, 2005). In
these early investigations, however, the TBCC-activated peroxide
system was established and applied deliberately under alkaline
conditions using a large excess amount of H2O2, and the resultant
bleaching performance was not as satisfactory as expected. TBCC
was found to have a poor stability to hydrolysis which was thought
to be a barrier to developing an effective activated peroxide system
(Lee, Lim, Hauser, & Hinks, 2005). There was no breakthrough until
2.4.2. Degree of polymerization
Cellulose dispersions were prepared from bleached cotton fab-
rics using cupriethylenediamine solution as a solvent, and the
fluidity (F) of cellulose dispersions was determined according to the
AATCC Test Method 82-2007. The degree of polymerization (DP) of
cotton fabrics was calculated from the fluidity by Eq. (1). The DP
value is correlated with chemical damage of cotton fibers resulting
from oxidative bleaching. A higher DP value indicates a lower fiber
damage.
N-[4-(triethylammoniomethyl)benzoyl]butyrolactam
chloride
(TBBC) was synthesized with an enhanced hydrolytic stability and
found to be effective under near-neutral pH conditions (Lee et al.,
2010; Xu, Shamey, & Hinks, 2010). Though work has been carried
out on testing the performance of the TBBC-activated peroxide
system on cotton bleaching (Xu, Shamey, Hinks, & El-Shafei, 2012;
Xu, Hinks, & Shamey, 2011), the mechanism that controls the
reaction pathways of TBBC in the system is unclear. In this study,
experimental data are generated from cotton bleaching with the
TBBC-activated peroxide system, by which the involved mecha-
nism can be elucidated and a proposal is inspired to establish a
new activated peroxide system based on TBBC.
ꢀ
ꢁ
74.35 + F
DP = 2032 log10
− 573
(1)
F
2.4.3. Water absorbency
The water absorbency (WA) of cotton fabric was evaluated
by measuring the elapsed time of a water drop on the cotton
fabric according to the AATCC Test Method 79-2010. A shorter
elapsed time of water drop on cotton fabric indicates a better water
absorbency.
2. Experimental
2.1. Materials
3. Results and discussion
Cotton greige knitted fabric was kindly provided by Cotton
Incorporated (USA), and used as the model fabric for bleaching.
TBBC was synthesized and purified to ≥97% using the method
reported previously (Lee et al., 2010). H2O2 (35% w/w) was pur-
chased from Sigma-Aldrich (USA). Trion X-100 was used as a
wetting agent in bleaching, and purchased from Fisher Scientific
(USA). A peroxide stabilizer commercially named Prestogen N-D
was purchased from BASF (USA). Cupriethylenediamine (0.1 M)
was used for preparing cellulose dispersions from bleached cotton
fabrics, and purchased from the Fisher Scientific Company, USA. All
other chemicals were of analytical grade unless otherwise stated.
3.1. Key factors affecting bleaching performance
3.1.1. pH value
The TBBC-activated peroxide system was prepared in 0.1 M
buffer solutions at various pH values with the addition of 30 mmol/L
TBBC and 36 mmol/L H2O2, in which H2O2 was used in a slight
excess over the stoichiometric amount for driving reactions to com-
pletion. The effect of pH values on the bleaching performance was
estimated by the degree of whiteness of bleached cotton fabric. As
can be seen in Fig. 1, a maximum degree of whiteness was achieved
when cotton fabric was bleached at a pH value in the range of 6 to
8 which is hereby denoted by pHM. This indicates that the perhy-
drolysis of TBBC was optimally conducted for generation of CPBDC
(Scheme 1) which was most effective at pHM for cotton bleaching.
The degree of whiteness decreased as the pH value decreased from
pHM to 3. This was most likely due to the fact that the perhydrolysis
2.2. Preparation of the TBBC-activated peroxide system
A quantity of buffer substances (citrate, phosphate or carbonate)
or an alkaline agent (NaHCO3, Na2CO3 or NaOH) was dissolved in

C. Xu et al. / Carbohydrate Polymers 119 (2015) 71–77
73
Fig. 2. Effect of temperature on the degree of whiteness of cotton fabric for bleaching
with the TBBC-activated peroxide system at pHM. Note: bleaching was carried out
in 0.1 M buffer solution for 60 min by adding 30 mmol/L TBBC and 36 mmol/L H2O2.
Fig. 1. Effect of pH on the degree of whiteness of cotton fabric for bleaching with
the TBBC-activated peroxide system. Note: bleaching was carried out in 0.1 M buffer
solution for 60 min by adding 30 mmol/L TBBC and 36 mmol/L H2O2.
to 12 at 100 ◦C, respectively. This was actually due to the use of a
1:1.2 molar ratio of TBBC to H2O2, of which the slightly excessive
amount of H2O2 was proposed to drive the perhydrolysis of TBBC
to completion but became more active for cotton bleaching with
increasing alkalinity and temperature.
of TBBC was decelerated or eventually terminated under such low
pH conditions that CPBDC could not be generated in an adequate
amount for cotton bleaching. The degree of whiteness decreased as
the pH value increased from pHM to 12 for bleaching at 25 and 50 ◦C,
11 for bleaching at 75 ◦C, and 10 for bleaching at 100 ◦C. In previous
investigations (Lee et al., 2005, 2010), such a decrease in the degree
of whiteness with increase in pH was often ascribed to the hydrol-
ysis of TBBC as demonstrated in Scheme 3. Since the perhydrolysis
rate is at least two orders of magnitude faster than the hydrolysis
rate (Jencks & Carriuolo, 1960; Pearson & Edgington, 1962; Wiberg,
1955), however, the hydrolysis of TBBC would not be responsible
for the decrease in the degree of whiteness. It has been known that
peracids readily undergo alkali-catalyzed bimolecular decomposi-
tion in an aqueous solution (Ball, Edwards, Haggett, & Jones, 1967;
Goodman, Robson, & Wilson, 1962; Koubek et al., 1963). It thus
deemed reasonable in this work that the decrease in the degree
of whiteness with increase in pH should be ascribed to the alkali-
catalyzed bimolecular decomposition of CPBDC as demonstrated in
Scheme 4, especially under more alkaline conditions.
3.1.2. Temperature
It appears in Fig. 1 that the effect of pH on the degree of white-
ness varies with temperature. For a clearer understanding of the
effect of temperature on the bleaching performance, the degree of
whiteness at pHM is plotted against temperature as shown in Fig. 2.
The effect of temperature on the degree of whiteness at pHM is
more apparent within the range of 25–50 ◦C than within the range
of 50–100 ◦C. This is because a higher temperature accelerated the
rates of the TBBC perhydrolysis and the subsequent cotton bleach-
ing with CPBDC, and the TBBC-activated peroxide system provided
an adequate bleaching performance at a temperature above 50 ◦C. It
is noted that the value of pHM decreased from 8 to 6 as temperature
increased from 25 ◦C to 100 ◦C, for which a possible reason may be
that an increase in temperature promoted the dissociation of H2O2
at a lower pH and as such the TBBC perhydrolysis. As indicated in
It is interesting to find in Fig. 1 that the degree of whiteness
increased as pH increased from 11 to pH 12 at 75 ◦C and from 10
Scheme 2. Perhydrolysis of TBLCs.
Scheme 3. Hydrolysis of TBBC.
Scheme 4. Possible alkali-catalyzed bimolecular decomposition of CPBDC.

74
C. Xu et al. / Carbohydrate Polymers 119 (2015) 71–77
Fig. 3. Effect of molar ratio of H2O2 to TBBC on the degree of whiteness of cotton fabric for bleaching at pH 7 (a), pH 10 (b), pH 12 (c), and on the difference in the degree of
whiteness between cotton fabrics for bleaching with and without adding TBBC (d). Note: bleaching was carried out in 0.5 M buffer solution at 50 ◦C for 60 min.
Fig. 2, it is very possible to establish an effective TBBC-activated
peroxide system at a temperature as low as 50 ◦C.
molar ratio of H2O2 to TBBC increased from 1:1 to 10:1, especially
from 1:1 to 2:1. This was most likely caused by the nucleophilic
attack of H2O2 on CPBDC as demonstrated in Scheme 5 because the
excessive amount of H2O2 used in the system more readily disso-
ciated under alkaline conditions (e.g. pH 10) to perhydroxyl anions
(HOO−) which are very strong nucleophilic reagent.
3.1.3. Molar ratio of H2O2 to TBBC
Various molar ratio of H2O2 to TBBC was used in the activated
peroxide system for bleaching at pH 7, 10 and 12, respectively. The
plots of the degree of whiteness against the molar ratio of H2O2 to
TBBC are shown in Fig. 3. As can be seen, the molar ratio of H2O2 to
TBBC had a great effect on the degree of whiteness which, however,
is related to pH.
When a large excess amount of H2O2 was applied in the TBBC-
activated peroxide system for bleaching of cotton under extremely
alkaline conditions (pH 12) as shown in Fig. 3c, it is difficult to
observe the effect of the nucleophilic attack to CPBDC by H2O2 on
the degree of whiteness because of a joint effect of the hydroly-
sis of TBBC (Scheme 2), the bimolecular decomposition of CPBDC
(Scheme 3) and the enhanced H2O2 bleaching. In order to clearly
recognize the effect of the excessive amount of H2O2 on the bleach-
ing performance, the data shown in Fig. 3a–c were mathematically
treated by subtracting the degree of whiteness that was achieved
using the H2O2 system (without adding any TBBC) from the degree
of whiteness that was achieved using the TBBC-activated peroxide
system (with adding 30 mmol/L TBBC), and the results were plot-
ted in Fig. 3d. It is noted that the excessive amount of H2O2 caused
more negative effect on the bleaching performance at higher pH
values.
It has been widely accepted that a large excessive amount of
H2O2 should be used in activated peroxide systems under alka-
line conditions for providing an additive effect on the bleaching
performance (Gursoy et al., 2004a,b; Lim et al., 2004, 2005). It
seems plausible that such an additive effect existed because the
TBBC-activated peroxide system provided a little better bleaching
performance than the H2O2 system as observed in Fig. 3c. However,
the fact is disclosed in Fig. 3d that the TBBC-activated peroxide
system lost most of its bleaching performance in the presence of
an excessive amount of H2O2 under alkaline conditions due to the
nucleophilic attack of H2O2 on CPBDC (Scheme 5). This finding is
very valuable for establishing an effective activated peroxide sys-
tem for cotton bleaching.
When the TBBC-activated peroxide system was established and
applied for bleaching at pH 7 (Fig. 3a), the degree of whiteness of
cotton fabric was greatly increased as the molar ratio of H2O2 to
TBBC increased from 0:1 to 1:1 and stayed relatively constant over
the molar ratio range of 1:1 to 10:1. It is indicated from Fig. 1 that
the perhydrolysis of TBBC was optimally established for genera-
tion of CPBDC which was responsible for bleaching at pH 7. When
the molar ratio of H2O2 to TBBC was less than the stoichiometric
ratio (e.g. 1:1), the amount of CPBDC generated from perhydrolysis
would depend on the amount of H2O2 used in the system. As the
molar ratio of H2O2 to TBBC was increased above the stoichiometric
ratio, the amount of CPBDC generated from perhydrolysis would be
stoichimetrically equal to the amount of TBBC. An excessive amount
of H2O2 may drive the perhydrolysis of TBBC to completion, but was
ineffective for bleaching at pH 7.
When the TBBC-activated peroxide system was established and
applied for bleaching at pH 10 (Fig. 3b), however, the molar ratio of
H2O2 to TBBC exhibited profoundly different effect on the degree
of whiteness of cotton fabric. As the molar ratio of H2O2 to TBBC
increased from 0:1 to 1:1, the degree of whiteness of cotton fab-
ric increased similarly but relatively lower as compared with that
resulting from bleaching at pH 7. The lower degree of whiteness
was ascribed to the alkali-catalyzed bimolecular decomposition of
CPBDC (Scheme 4). However, it is interesting to note in Fig. 3b that
the degree of whiteness of cotton fabric greatly decreased as the

C. Xu et al. / Carbohydrate Polymers 119 (2015) 71–77
75
Scheme 5. Nucleophilic attack of H2O2 on CPBDC.
Scheme 6. Possible reactions in the TBBC-activated peroxide system.
3.2. Establishment of the TBBC/H2O2/NaHCO3 system
cotton fabrics as shown in Table 1. It can be seen that the
TBBC/H2O2/NaHCO3 system was equivalent to the H2O2/NaOH
system in improving the degree of whiteness of cotton fabric. It
is interesting to note that, unlike the H2O2/NaOH system which
resulted in a remarkable reduction in the degree of polymeriza-
tion of cotton fabric, the TBBC/H2O2/NaHCO3 system resulted in no
apparent reduction in the degree of polymerization of cotton fabric.
This indicates that the TBBC/H2O2/NaHCO3 system had advantage
over the H2O2/NaOH system in protecting cotton fibers from chem-
ical damage during the bleaching process. The TBBC/H2O2/NaHCO3
system was found to be slightly inferior to the H2O2/NaOH sys-
tem in improving the water absorbency of cotton fabric, but it is
Based on the above results and discussion, it can be con-
cluded that there may exist several possible reactions in the
TBBC-activated peroxide system as demonstrated in Scheme 6. The
perhydrolysis of TBBC and the cotton bleaching with CPBDC are
desired reactions while the hydrolysis of TBBC, alkali-catalyzed
bimolecular and H2O2-attacked decompositions of CPBDC are
undesired side-reactions. pH is a key factor affecting the proceeding
of these reactions and, at pHM, the desired reactions are optimally
established but the undesired side-reactions are prevented. Hence,
the bleaching performance can be maximized by maintaining the
TBBC-activated peroxide system at pHM
.
In practical cotton bleaching, it is advisable to use a common
alkali as an approach to approximating pHM in the TBBC-activated
peroxide system. NaHCO3, Na2CO3 and NaOH were primarily exam-
ined in this work. As can be seen from Fig. 4a, NaHCO3 was more
applicable than Na2CO3 and NaOH for maintaining pH within the
desired range before and after bleaching, e.g. pHM 1. As is known,
NaHCO3 is a weaker alkali than Na2CO3 and NaOH. An aqueous
solution of NaHCO3 has a pH value of less than 9 while aqueous
solutions of NaHCO3 and NaOH may have pH values of greater than
10. Hence, NaHCO3 had an advantage over Na2CO3 and NaOH for
use as an alkali in suppressing the undesired side reactions in the
TBCC-activated peroxide system. Accordingly, NaHCO3 was supe-
rior to Na2CO3 and NaOH, actually equivalent to pHM for improving
the degree of whiteness as shown in Fig. 4b. NaHCO3 was not only
effective for neutralizing the acid produced in the TBBC-activated
peroxide system, but also resulted in no apparent increase in pH
with an excessive amount. As shown in Fig. 5, a 1:1 molar ratio of
NaHCO3 to TBBC was adequate for use in the TBBC-activated per-
oxide system which provided cotton fabric a maximum degree of
whiteness, and an excessive amount of NaHCO3 had no apparent
effect on bleaching performance.
The TBBC-activated peroxide system could thus be established
by incorporating TBBC, H2O2 and NaHCO3, of which a molar ratio
of 1:1.2:1.25 was suggested for the purpose of ensuring a complete
conversion of TBBC into CPBDC for cotton bleaching at low temper-
atures. As shown in Fig. 6, such an established TBBC/H2O2/NaHCO3
system exhibited a rapid bleaching performance at a temperature
as low as 50 ◦C.
The TBBC/H2O2/NaHCO3 system was compared with the hot
alkaline H2O2/NaOH system in terms of the degree of white-
ness, degree of polymerization and water absorbency of bleached
Fig. 4. Performance of various alkaline agents for use in the TBBC-activated peroxide
system: (a) pH before and after bleaching and (b) degree of whiteness of cotton
fabric after bleaching. Note: bleaching was carried out at 50 ◦C for 60 min by adding
30 mmol/L TBBC, 36 mmol/L H2O2 and 50 mmol/L alkaline agent.

76
C. Xu et al. / Carbohydrate Polymers 119 (2015) 71–77
considered that the water absorbency of cotton fabric bleached
with the TBBC/H2O2/NaHCO3 system would be adequate for further
dyeing.
4. Conclusions
An activated peroxide system was established by using TBBC
as a bleach activator for cotton bleaching at a low temperature.
Experimental results showed that the TBBC-activated peroxide sys-
tem was most effective for bleaching in a pH range of 6–8 which
was slightly affected by temperature. The bleaching performance
was reduced either below this pH range where the perhydroly-
isis of TBBC and the cotton bleaching with CPBDC were most
likely decelerated or eventually terminated, or above this pH range
where CPBDC could undergo extensive alkali-catalyzed bimolec-
ular and H2O2-attacked decompositions. NaHCO3 was preferably
selected as an alkaline agent for use in the TBBC-activated per-
oxide system for its capacity of maintaining pH in the desired
range of 6–8. An effective activated peroxide system was resulted
from a combination of TBBC, H2O2 and NaHCO3, of which a molar
ratio of 1:1.2:1.25 was applicable for rapid cotton bleaching at
a temperature as low as 50 ◦C. In compared to the hot alkaline
H2O2/NaOH system, the TBBC/H2O2/NaHCO3 system provided cot-
ton fabric with an equivalent degree of whiteness, higher degree
of polymerization and slightly lower water absorbency. The new
activated peroxide system may provide an alternative approach to
cotton bleaching that can be carried out under much mild con-
ditions such as near-neutral pH, low temperature and rapid time
period.
Fig. 5. Effects of the molar ratio of NaHCO3 to TBBC on pH before and after bleaching
(a), and on degree of whiteness of cotton fabric after bleaching (b). Note: bleaching
was carried out at 50 ◦C for 60 min by adding 30 mmol/L TBBC and 36 mmol/L H2O2.
Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (Grant no. 21276106), and Cotton Incorporated, US
(Grant no. 09-635).
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DP
WA (s)
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a
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b
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C
for 40 min.

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