Brewery effluent may have dissolved heavy metals that remain in the receiving waters and affect both aquatic life and human health. This study explored the efficiency of the African pear seed activated carbon (APSAC) derived from Dacryodes edulis seed waste as a low-cost adsorbent for removing chromium ion (Cr2+) from brewery wastewater. APSAC was synthesized by the procedure involving drying and pulverization of the seed waste, carbonization at 600 °C for 2 h, 40% H2SO4 impregnation for 24 h, activation at 500 °C for 4 h, neutral washing, drying, and sieving into 250 \(\mu\)m fraction. Proximate analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy were employed for characterizing bulk properties, surface functional groups, and surface morphology. Batch experiments of the adsorption process were planned on the basis of central composite design to investigate the influence of contact time (15–75 min), initial Cr2+ concentration (0.005–0.025 mg L\(-1\)), and adsorbent dosage (0.5–2.5 g). The maximum Cr2+ removal observed was 96% at 0.025 mg L\(-1\), 1.5 g APSAC, and 45 min, while the maximum adsorption capacity of APSAC was 0.0048 mg g\(-1\) at 0.015 mg L\(-1\), 0.5 g APSAC, and 45 min. The developed model for the adsorption capacity response was statistically significant (\(F=13.94\), \(p=0.0049\)) and had high explanatory power (\(R^2=0.9617\)). The equilibrium data were better described by the Sips isotherm model (\(R^2=0.9849\)) indicating the heterogeneity of surface adsorption process. The kinetic and Boyd studies suggested that surface absorption and film diffusion controlled the process of chromium removal rate. The results confirm the effectiveness of APSAC as biomass-derived adsorbent for chromium removal from brewery effluent and the potential of valorization of the African pear seed waste in wastewater treatment.
