Dyestuff Adsorbing Natural Composites for Wastewater Treatments
119
substitution (DS) of 0.75, and 4000 cP is its maximum viscosity for 1% solution.
The viscosity of CMC increases below pH 4, due to the presence of sodium salt
of weak acid groups, when free acid is formed. If all COOH groups of CMC have
been reacted for salt formation, its pH would be 8.25. Na-CMC has higher moisture
absorption than other cellulose ethers, directly proportional to its DS, thanks to its
ionic character [34]. Thanks to its strong anionic character, Na-CMC is also used
for removal of cationic dyestuff from textile dyeing effluents, and its usefulness for
removal of various dyestuffs is presented [52, 53].
The first step is treating cotton fiber with sodium hydroxide. In this step, negatively
charged oxygen atom is produced by removing the hydrogen atom from the hydroxyl
group, and a reactive form of cellulose is produced which is called alkali or soda cellulose. These sites of cellulose are used for reaction of chloroacetate. Secondly, soda
cellulose is treated with the sodium salt of chloroacetic acid under alkaline conditions. As shown in Fig. 6, hydroxyl groups of cellulose chain are using for reaction
of chloroacetate to produce an ether linkage, and hydrochloric acid is formed at the
end of the reaction [54, 55]. The first substitution occurs on the primary alcohols,
and then, the second substitution is seen on the secondary alcohols. The substitution
will occur more rapidly in the regions where crystallinity is lower. Moreover, very
inhomogeneous carboxymethyl group distribution is seen in the early stages of the
reaction. Carboxymethyl group distribution becomes more homogeneous when the
reaction time is extended [56].
The resulting material which is carboxymethyl cellulose is very swellable and
has highly acidic carboxyl groups that enhance the values in elongation at break,
moisture regain, soil release, water retention, and tensile strength [57, 58]. CMC that
is suitable for being an adsorbent for dye removal from aqueous solution in a broader
pH range has low DS value, and it is water insoluble [59].
Salama and his friends examined the removal of methyl orange dye from
aqueous solutions by using Carboxymethyl cellulose-g-poly(2-(dimethylamino)
ethyl methacrylate) (CMC-g-PDMAEMA) in hydrogel form as an adsorbent and
finding the adsorption kinetics of CMC-g-PDMAEMA. At the study, high viscosity
CMC sodium salt is used, and FTIR spectroscopy is done to observe the structural
changes of CMC-g-PDMAEMA and CMC hydrogel, and the effect of pH on dye
adsorption is observed. As a result of the study, increase of the pH decreases the
adsorption capacity of the hydrogel, and it is seen that the adsorption process occurs
by the chemical interaction between the bioabsorbent surfaces and the dyestuff [60].
Cai et al. had research on the hydrolysis degree effect of hydrolyzed polyacrylamide grafted carboxymethyl cellulose (CMC-g-HPAM) on dye removal efficiency.
In the study, series of CMC-g-HPAM is produced and it is used as flocculants
to remove methylene blue dye from aqueous solution. As a result, using FTIRspectroscopy, characterization of CMC-g-HPAM is done. The flocculation performance of the CMC-g-PAM, CMC-g-HPAM and CMC are compared, and CMCg-HPAM made higher flocculation performance for removal of methylene blue
[61].
119
substitution (DS) of 0.75, and 4000 cP is its maximum viscosity for 1% solution.
The viscosity of CMC increases below pH 4, due to the presence of sodium salt
of weak acid groups, when free acid is formed. If all COOH groups of CMC have
been reacted for salt formation, its pH would be 8.25. Na-CMC has higher moisture
absorption than other cellulose ethers, directly proportional to its DS, thanks to its
ionic character [34]. Thanks to its strong anionic character, Na-CMC is also used
for removal of cationic dyestuff from textile dyeing effluents, and its usefulness for
removal of various dyestuffs is presented [52, 53].
The first step is treating cotton fiber with sodium hydroxide. In this step, negatively
charged oxygen atom is produced by removing the hydrogen atom from the hydroxyl
group, and a reactive form of cellulose is produced which is called alkali or soda cellulose. These sites of cellulose are used for reaction of chloroacetate. Secondly, soda
cellulose is treated with the sodium salt of chloroacetic acid under alkaline conditions. As shown in Fig. 6, hydroxyl groups of cellulose chain are using for reaction
of chloroacetate to produce an ether linkage, and hydrochloric acid is formed at the
end of the reaction [54, 55]. The first substitution occurs on the primary alcohols,
and then, the second substitution is seen on the secondary alcohols. The substitution
will occur more rapidly in the regions where crystallinity is lower. Moreover, very
inhomogeneous carboxymethyl group distribution is seen in the early stages of the
reaction. Carboxymethyl group distribution becomes more homogeneous when the
reaction time is extended [56].
The resulting material which is carboxymethyl cellulose is very swellable and
has highly acidic carboxyl groups that enhance the values in elongation at break,
moisture regain, soil release, water retention, and tensile strength [57, 58]. CMC that
is suitable for being an adsorbent for dye removal from aqueous solution in a broader
pH range has low DS value, and it is water insoluble [59].
Salama and his friends examined the removal of methyl orange dye from
aqueous solutions by using Carboxymethyl cellulose-g-poly(2-(dimethylamino)
ethyl methacrylate) (CMC-g-PDMAEMA) in hydrogel form as an adsorbent and
finding the adsorption kinetics of CMC-g-PDMAEMA. At the study, high viscosity
CMC sodium salt is used, and FTIR spectroscopy is done to observe the structural
changes of CMC-g-PDMAEMA and CMC hydrogel, and the effect of pH on dye
adsorption is observed. As a result of the study, increase of the pH decreases the
adsorption capacity of the hydrogel, and it is seen that the adsorption process occurs
by the chemical interaction between the bioabsorbent surfaces and the dyestuff [60].
Cai et al. had research on the hydrolysis degree effect of hydrolyzed polyacrylamide grafted carboxymethyl cellulose (CMC-g-HPAM) on dye removal efficiency.
In the study, series of CMC-g-HPAM is produced and it is used as flocculants
to remove methylene blue dye from aqueous solution. As a result, using FTIRspectroscopy, characterization of CMC-g-HPAM is done. The flocculation performance of the CMC-g-PAM, CMC-g-HPAM and CMC are compared, and CMCg-HPAM made higher flocculation performance for removal of methylene blue
[61].