remazol yellow GR, and remazol turquoise blue G at different temperatures and
pressures. DK membrane showed highest permeate flux at higher temperatures with
acidic to neutral pH and 100% color removal of the synthetic wastewater
(Hildebrand et al. 2014). Poly(m-phenylene isophthalamide)-based nanofiltration
membranes were used to remove Eriochrome Blue Black B, Eriochrome Black T,
and alizarin red dyes. The designed nanofiltration membrane showed 98% rejection
with a high flux at 0.4 MPa (Huang and Zhang 2011). The nanofiltration membranes
were prepared by polyethersulfone-based hollow fibers and employed for the
removal of indigo carmine. The obtained results endorsed the efficacy of the
nanofiltration membranes by showing 96.4% rejection of dye with
12.8 L m
À2 h
À1 bar
À1 (Gao et al. 2017). Similar study was carried out for indigo
carmine using nanofiltration membranes prepared for polyethersulfone-based hollow fibers. Nanofiltration membrane possessed a molecular weight cut-off of
1500 Da, the pore diameter of %1.96 nm, high pure water permeability of 13.2
LMH/bar, and 94.9% rejection of the dye (Thong et al. 2018).
Sulfonated polyphenylene sulfone-based positively charged nanofiltration membranes are reported. Membranes having 1.13–1.2 nm diameter, molecular weight
cut-off of 1627–1674 Da, and highly positive surface charge led to the 99.98%
rejection of Safranin O (Zhong et al. 2012). In a similar study, a positively charged
nanofiltration membrane showed rejection of 99.8, 99.8, and 99.2% of brilliant
green, victoria blue B, and 7, respectively (Zheng et al. 2013). A novel composite
nanofiltration membrane was prepared using plant polyphenols and achieved elevated permeability of 76.3 L/(m
2 h MPa) and 99.0% rejection for 1 (Zhao et al.
2018). The synthesized membrane was further cross-linked with FeCl 3 . The negatively charged membrane was used to remove dyes such as Sunset Yellow, 6, and
1 and exhibited rejection rates of 82.2, 99.7, and 99.9%, respectively (Yu et al.
2012).
Low-pressure nanofiltration membranes were fabricated having hydroxyl groups
ended hyperbranched polyester with polysulfone ultrafiltration membrane as the
porous support. Nanofiltration membranes possessed the 100 and 98.4% rejection
of the nanofiltration membrane to 9 and xylenol orange, respectively (Wei et al.
2012). Positively charged nanofiltration membranes were prepared from crosslinking polyimide substrate with polyethylenimine, with molecular weight cut-off
of 458 Da with a high rejection (>95%), and high fouling resistance against basic
dyes was reported (Wang et al. 2018). Table 17.2 shows different parameters for the
adsorbents mentioned in the above section.
17.2.3 Coagulation-Flocculation
Coagulation-flocculation could be applied as a primary treatment or even before and
after the major process. Unfortunately, a lot of commercially available coagulants,
including aluminum chloride, aluminum sulfate, and polyacrylamide-based materials, are reported to have bad impacts on human health. The dilemma led to the
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R. S. Ashraf et al.
pressures. DK membrane showed highest permeate flux at higher temperatures with
acidic to neutral pH and 100% color removal of the synthetic wastewater
(Hildebrand et al. 2014). Poly(m-phenylene isophthalamide)-based nanofiltration
membranes were used to remove Eriochrome Blue Black B, Eriochrome Black T,
and alizarin red dyes. The designed nanofiltration membrane showed 98% rejection
with a high flux at 0.4 MPa (Huang and Zhang 2011). The nanofiltration membranes
were prepared by polyethersulfone-based hollow fibers and employed for the
removal of indigo carmine. The obtained results endorsed the efficacy of the
nanofiltration membranes by showing 96.4% rejection of dye with
12.8 L m
À2 h
À1 bar
À1 (Gao et al. 2017). Similar study was carried out for indigo
carmine using nanofiltration membranes prepared for polyethersulfone-based hollow fibers. Nanofiltration membrane possessed a molecular weight cut-off of
1500 Da, the pore diameter of %1.96 nm, high pure water permeability of 13.2
LMH/bar, and 94.9% rejection of the dye (Thong et al. 2018).
Sulfonated polyphenylene sulfone-based positively charged nanofiltration membranes are reported. Membranes having 1.13–1.2 nm diameter, molecular weight
cut-off of 1627–1674 Da, and highly positive surface charge led to the 99.98%
rejection of Safranin O (Zhong et al. 2012). In a similar study, a positively charged
nanofiltration membrane showed rejection of 99.8, 99.8, and 99.2% of brilliant
green, victoria blue B, and 7, respectively (Zheng et al. 2013). A novel composite
nanofiltration membrane was prepared using plant polyphenols and achieved elevated permeability of 76.3 L/(m
2 h MPa) and 99.0% rejection for 1 (Zhao et al.
2018). The synthesized membrane was further cross-linked with FeCl 3 . The negatively charged membrane was used to remove dyes such as Sunset Yellow, 6, and
1 and exhibited rejection rates of 82.2, 99.7, and 99.9%, respectively (Yu et al.
2012).
Low-pressure nanofiltration membranes were fabricated having hydroxyl groups
ended hyperbranched polyester with polysulfone ultrafiltration membrane as the
porous support. Nanofiltration membranes possessed the 100 and 98.4% rejection
of the nanofiltration membrane to 9 and xylenol orange, respectively (Wei et al.
2012). Positively charged nanofiltration membranes were prepared from crosslinking polyimide substrate with polyethylenimine, with molecular weight cut-off
of 458 Da with a high rejection (>95%), and high fouling resistance against basic
dyes was reported (Wang et al. 2018). Table 17.2 shows different parameters for the
adsorbents mentioned in the above section.
17.2.3 Coagulation-Flocculation
Coagulation-flocculation could be applied as a primary treatment or even before and
after the major process. Unfortunately, a lot of commercially available coagulants,
including aluminum chloride, aluminum sulfate, and polyacrylamide-based materials, are reported to have bad impacts on human health. The dilemma led to the
618
R. S. Ashraf et al.