Removal of Hexavalent Chromium from Aqueous Solution Using Iron Modified Bio chars Derived from Industrial and Municipal Waste

Abstract

Chromium (VI) contamination in water poses serious health and environmental threats. This study investigates the removal of Cr (VI) from water using brewery spent grain and sewage sludge (BSG/SS), municipal sewage sludge (MSS), and metal processing slag (MPS) collected from industrial sites in Addis Ababa. The compositions of raw, Fe-modified, and heat-treated BSG, BSS, MSS, and MPS were analyzed. Based on initial screening, Fe-modified and heat treated BSG pyrolyzed at 500 °C was further characterized using BET, FTIR, XRD, and SEM. Batch experiments optimized contact time, pH, Cr (VI) concentration, and adsorbent dose to maximize Cr (VI) removal. Under optimal conditions (7 hours, pH 3, 10 mg/L Cr (VI), 2 g/L adsorbent), Fe-BSG biochar achieved 99.88% Cr (VI) removal at 20 mg/L. The pseudo-second order model accurately described the kinetics of Cr (VI) removal (R2 = 0.98012), indicating chemisorption. The Freundlich isotherm fit the data well, with Fe-BSG biochar exhibiting an estimated adsorption capacity of 24.775 mg/g. The potential for recycling suggests that Fe BSG biochar is a valuable material for Cr (VI) removal from aqueous solution. Transforming industrial byproducts into resources benefits environmental pollution mitigation. Future research should evaluate its performance in real wastewater.