Biocomposite adsorbent (cross-linked chitosan + algae + montmorillonite) for methyl violet 2B dye removal: statistical modelling and optimisation

Herein, a biocomposite of crosslinked chitosan polyethylene glycol diglycidyl ether (CS-PEDGE), montmorillonite (MMT), and food-grade algae (FGA) was successfully prepared by a hydrothermal technique. The resulting absorbent (CS-PEDGE/FGA/MMT) was assessed for its adsorption property with methyl violet 2B (MV 2B) a toxic cationic dye. The physicochemical properties of CS-EDGE/FGA/MMT were assessed via various analytical techniques, including BET, Elemental analysis, pHpzc, and spectroscopy (FTIR, XRD, SEM-EDX). The influence of three adsorption variables, namely adsorbent dose (A: 0.02–0.1 g/100 mL), solution pH (B: 4–10), and contact time (C: 10–420 min) on the rate of MV 2B dye removal was examined using the Box-Behnken design (RSM-BBD). The findings from the equilibrium isotherm and kinetic analyses suggest that the MV 2B dye adsorption onto the biocomposite surface follow the Freundlich model and pseudo-second-order kinetic models. The biocomposite adsorbent exhibits a maximum dye adsorption capacity (qmax) of 94.2 mg/g. The proposed MV 2B dye adsorption mechanism involves hydrogen bonding, n-π stacking, and electrostatic forces. This research demonstrates the unique structure and outstanding adsorption properties of CS-EDGE/FGA/MMT, which offers a viable solution for removal of detrimental MV 2B dyes from aqueous media.