Dyestuff Adsorbing Natural Composites for Wastewater Treatments
125
5.5 Other Polymers
Other polymers, especially biopolymers for the natural cycle, are mostly used in the
form of hydrogels, bead pellets, etc., for being an adsorbent, and they have very
advantageous usage in wastewater refinement processes of the textile industry. Some
studies are summarized below:
Ekici and Guntekin assert that low-temperature dyestuff removal can be done
with their hydrogel. They could yield 111–122 mg dyestuff adsorption per gram of
adsorbent by using polyampholytes (PAHs) hydrogels in simultaneous Remazol-type
dyestuff removal studies at 35 °C and 20 °C. They had dyestuff adsorption ability
from 94 to 98% [79].
Inal et al. studied on methylene blue dyestuff removal by using hydrogels that
are acrylamide–crotonic acid. When hydrogels which consist of only acrylamide,
adsorption can be increased by increasing pH. Maximum adsorption was yielded
with pH 9 for 300-min treatment. For acrylamide–crotonic acid hydrogels, pH 8
causes a decreased adsorption, while pH 7, 9, and 10 bring similar adsorption. When
crotonic acid amount in hydrogel structure increased, adsorption amount increased.
Desorption can be done by treating colored hydrogels at pH 2 HCl-KCl buffer solution
for one hour. Also, their hydrogel did not lose adsorption capacity when it is used
20 times repeatedly [80].
Sudarsan et al. suggested using reusable hydrogels which consist of sodium alginate for methylene blue removal procedure. Condensation of ethylene glycol and
acrylic acid and then free-radical polymerization were steps for introducing ionic
pendant functionalities on sodium alginate, and pH-tunable hydrogels were prepared.
They observed higher swelling at higher pH. Removal amount of tried hydrogels is
between 80 and 98%. Also, up to 90% desorption of hydrogels could be done at
0.1 N HCl solution, and they could be reused [81].
Ma and Zhang investigated the adsorption of alizarin red S(ARS) by Fe/Al–alginate composite hydrogel electrode electrocoagulation (EC). They added 2.0% (w/v)
sodium alginate solution with scrap iron to 5.0% (w/v) Ca
2+ (CaCl 2 · 2H 2 O) which is
hardening solution at 60 °C for 2 h and then storing at 3% (w/v) Al
3+ (AlCl 3 ) for the
dye degradation study. Initial pH 3 with O 2 is suitable for the optimal degradation of
ARS. COD is removed by the electrode application up to 90% efficiency. Maximum
color removal is 99%, and 30 min is the optimum time for electrolysis. These electrodes have better results compared to conventional ones, and they suggest using the
ultrasonic application because it accelerates electrocoagulation [82].
Ilgın and Ozay emphasized that they produced hydrogels from poly(acrylamideco-methacrylamido-4-(2-aminoethyl) morpholine) and poly(Aam-c-MAEM) with
four different molar ratios (nAam/nMAEM: 100/0, 95/5, 90/10, 80/20) by using
single-step free-radical aqueous polymerization. The produced hydrogel is used for
reactive orange (RO) removal which is anionic dyestuff. They used 0.1 mol% MBA
as a cross-linker. When the comonomer ratio and initial adsorbent amount increased,
the removal ability increased; while temperature and pH of solution increased, the
removal percent decreased. Also, maximum removal was done by distilled water.
125
5.5 Other Polymers
Other polymers, especially biopolymers for the natural cycle, are mostly used in the
form of hydrogels, bead pellets, etc., for being an adsorbent, and they have very
advantageous usage in wastewater refinement processes of the textile industry. Some
studies are summarized below:
Ekici and Guntekin assert that low-temperature dyestuff removal can be done
with their hydrogel. They could yield 111–122 mg dyestuff adsorption per gram of
adsorbent by using polyampholytes (PAHs) hydrogels in simultaneous Remazol-type
dyestuff removal studies at 35 °C and 20 °C. They had dyestuff adsorption ability
from 94 to 98% [79].
Inal et al. studied on methylene blue dyestuff removal by using hydrogels that
are acrylamide–crotonic acid. When hydrogels which consist of only acrylamide,
adsorption can be increased by increasing pH. Maximum adsorption was yielded
with pH 9 for 300-min treatment. For acrylamide–crotonic acid hydrogels, pH 8
causes a decreased adsorption, while pH 7, 9, and 10 bring similar adsorption. When
crotonic acid amount in hydrogel structure increased, adsorption amount increased.
Desorption can be done by treating colored hydrogels at pH 2 HCl-KCl buffer solution
for one hour. Also, their hydrogel did not lose adsorption capacity when it is used
20 times repeatedly [80].
Sudarsan et al. suggested using reusable hydrogels which consist of sodium alginate for methylene blue removal procedure. Condensation of ethylene glycol and
acrylic acid and then free-radical polymerization were steps for introducing ionic
pendant functionalities on sodium alginate, and pH-tunable hydrogels were prepared.
They observed higher swelling at higher pH. Removal amount of tried hydrogels is
between 80 and 98%. Also, up to 90% desorption of hydrogels could be done at
0.1 N HCl solution, and they could be reused [81].
Ma and Zhang investigated the adsorption of alizarin red S(ARS) by Fe/Al–alginate composite hydrogel electrode electrocoagulation (EC). They added 2.0% (w/v)
sodium alginate solution with scrap iron to 5.0% (w/v) Ca
2+ (CaCl 2 · 2H 2 O) which is
hardening solution at 60 °C for 2 h and then storing at 3% (w/v) Al
3+ (AlCl 3 ) for the
dye degradation study. Initial pH 3 with O 2 is suitable for the optimal degradation of
ARS. COD is removed by the electrode application up to 90% efficiency. Maximum
color removal is 99%, and 30 min is the optimum time for electrolysis. These electrodes have better results compared to conventional ones, and they suggest using the
ultrasonic application because it accelerates electrocoagulation [82].
Ilgın and Ozay emphasized that they produced hydrogels from poly(acrylamideco-methacrylamido-4-(2-aminoethyl) morpholine) and poly(Aam-c-MAEM) with
four different molar ratios (nAam/nMAEM: 100/0, 95/5, 90/10, 80/20) by using
single-step free-radical aqueous polymerization. The produced hydrogel is used for
reactive orange (RO) removal which is anionic dyestuff. They used 0.1 mol% MBA
as a cross-linker. When the comonomer ratio and initial adsorbent amount increased,
the removal ability increased; while temperature and pH of solution increased, the
removal percent decreased. Also, maximum removal was done by distilled water.