Waste based chitosan membranes for dye removal

Abstract

Water contamination is an important global issue. This study explores dye removal potential of chitosan-based membranes with lemon waste and , selected based on circular economy and green chemistry. Lemon waste and chitosan were used to recover . Membranes were produced by solvent casting, with some treated in NaOH 1 M for structural modification and others in (ac) for crosslinking. ATR-FTIR and XPS revealed chemical structure modifications. Hydrated membranes exhibited a two-order magnitude decrease in elastic modulus versus dried ones. pH of point zero charge diminished by incorporation of and increased by NaOH treatment. Lemon extract and NaOH treatment increased sorption from 500 mg/g to 1800-2500 mg/g, with minimum 3 cycles of sorption-desorption. Dye removal was studied at different concentration, times, pH and temperatures. Lemon extract boosted crystal violet sorption but reduced methyl orange sorption, while diminished crystal violet sorption without affecting methyl orange. Methyl orange (minimum 72 % removal) could be desorbed with NaOH for at least 5 cycles. Hence, sorption of dyes cannot be explained by coulombic interactions alone. Conclusively, chitosan with lemon peel extract or are a sustainable alternative, using biopolymers, waste and for sorption from wastewater. Scaling-up would be possible for -chitosan membrane.