Efficient removal of dyes using carboxymethyl cellulose/alginate/polyvinyl alcohol/rice husk composite: Adsorption/desorption, kinetics and recycling studies.

Rapid industrialization is polluting the water resources and is becoming a serious environmental issue. In present study, the adsorption-desorption behavior of Direct Orange-26 (DO-26), Direct Red-31 (DR-31), Direct Blue-67 (DB-67) and Ever direct Orange-3GL (EDO-3) dyes on to native, modified rice husk (MRH), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and alginate (ALG) immobilized biomasses were investigated under different experimental conditions. For adsorbent modification, physical and chemical treatments were performed. The results showed that HCl pre-treatment considerably increased the sorption capacity of dyes versus native biomass. The sorption data were optimized using pseudo 1st order, intra-particle diffusion, pseudo 2nd order and Elovich models. The results revealed that the two-step rate equation was followed for the desorption kinetics of dyes. The involvement of -OH (hydroxyl), -COOH (carboxylic) and -NH (amino) groups in the adsorption of dyes onto biomasses was shown by FTIR analysis. Studies exhibited that among adsorbents employed, the MRH has the excellent potential for the dyes degradation from textile effluents.