Thermally activated adsorbent derived from kitchen biowaste for treatment of tannery wastewater

• Cr-adsorption studied on thermally activated kitchen biowaste adsorbent • Fortified adsorbent was characterized through SEM, EDS, FTIR, and pHpzc • At optimal environments, 99.92% Cr was adsorbed from tannery wastewater • Cr-adsorption was best fit FOR PSO kinetics and followed the Freundlich model The discharge of unprocessed tannery wastewater is a major environmental concern. It contains harmful chemicals and metals, especially chromium. This study explored the chromium adsorption on the thermally activated kitchen biowaste adsorbent (TAKBWA) from the tannery effluent. Before and after treatment, the TAKBWA were characterized through SEM, FT-IR, EDS, and pHpzc. In a batch test at optimal conditions, chromium removal was achieved at 99.92% with an adsorbent dose of 1.2 g per 50 mL wastewater, a stirring time of 10 minutes, and a relative pH of 7.9. The pHpzc indicates the adsorption worked on the positive surface of TAKBWA. The adsorption was well fitted for the pseudo-second-order kinetic model and Freundlich isotherm. The thermodynamic studies ensured that adsorption was chemically regulated, spontaneous, and exothermic. The adsorption reaction was chemisorption with a greater adsorbent-adsorbate (chromium) interaction. A reduction of biochemical oxygen demand (46.0%), chemical oxygen demand (13.5%), and chloride (20.1%) of the tannery effluent was achieved. Hence, TAKBWA can be considered to treat the tannery wastewater, especially chromium removal before discharge to the environment.