Microwave-assisted synthesis of cross-linked chitosan-metal oxide nanocomposite for methyl orange dye removal from unary and complex effluent matrices.

Textile/Dyeing industries have been considered as one of the intense water-consuming units, resulting in the generation of a large volume of dye(s) contaminated effluent posing a heavy burden on the receiving water bodies. Therefore, the identification of methods to synthesize bulk quantity of adsorbent(s) and further their evaluation for the efficient treatment of effluent is one of the most prominent topics. Hence, microwave-assisted method was proposed for the rapid synthesis of nanocomposite (C-CS@ZnO) from natural biomolecule (chitosan-CS), a well-known crosslinker (tripolyphosphate) and metal-oxide (ZnO) nanoparticles. Detailed characterization was performed to identify the structure (SEM, XRD) and composition (FT-IR, XPS) of the sorbent. Sorption experiments with methyl orange (MO) dye solution were carried out under different pH (2.0-12.0), dye concentrations (150-350 mg L), reaction times (0-210 min) and temperature (25-45 °C) to establish the adsorbent at the lab-scale. The maximum sorption capacity (185.2 mg g) was obtained because of the ligand-exchange, Yoshida H-bonding and electrostatic interactions and was best elucidated by Freundlich (R ≥ 0.99) and pseudo-second-order (R ≥ 1) models. To simulate the field conditions, the effects of co-existing ions (anions/cations), cocktail dyes/ions mixture and regenerant were also studied. The obtained results suggest its promising applicability at a large scale for textile effluent treatment.