Solid waste-derived biodegradable keratin sponges for removal of chromium: A circular approach for waste management in leather industry

Abstract

Abstract Sustainable consumption and production falls under UN sustainable development goal 12, which require environmentally sound management of chemicals and all wastes; and to reduce waste generation through prevention, reduction, recycling and reuse. Leather industry produce huge solid keratinous waste and chromium contaminated wastewater. In this study, a sponge is obtained from keratinous waste that is tested to remove chromium from wastewater. Removal experiments are carried out at simulated leather industry discharge conditions. Characteristics features of sponge are; its multimodal pore structure with mesopores of 3.83 nm (BET surface area 5.52 m2/g) and 66.5% of macropores as obtained by nitrogen adsorption porosimetry and volume displacement methods, respectively. Removal of chromium was optimized by multivariate method and procedure was applied for removal of chromium from synthetic and real tanning industry wastewater that showed 91% and 87.13% removal efficiency. Langmuir adsorption capacity of 270 mg/g was obtained. Desorption study showed that at pH 10 or above, sponge can be reused, and recovery of chromium is feasible. Sorption mechanism and continuous flow removal experiments were also carried out to understand the interaction and industrial viability of method. Overall finings support ‘utilization of solid waste for treatment of liquid waste’ which would add into environmentally sustainable production in leather industry.