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.
