Biochar from municipal organic waste: A low-cost adsorbent for Pb2+ and Cu2+ removal from aqueous solutions

Heavy metal contamination is a critical environmental issue, posing severe risks to human health and ecosystems. Adsorption has emerged as a cost-effective and efficient technique for heavy metal removal. This study evaluates the adsorption capacity of biochar produced in a pilot pyrolysis plant using organic waste from Machupicchu, Cusco, Peru, for the removal of lead (Pb²⁺) and copper (Cu²⁺) from aqueous solutions. The biochar was characterized using FTIR, SEM, BET analysis, ICP-MS, and TGA. Adsorption experiments were conducted at different pH values, with an optimal pH of 5. The effects of adsorbent dosage (50–100 mg), contact time (20–60 min), and agitation speed (50–150 rpm) on adsorption capacity were analyzed. ANOVA results confirmed that all factors significantly influenced adsorption. The highest adsorption capacity was obtained at 1.5 g/L biochar dosage, 40 min contact time, and 100 rpm agitation speed, with maximum adsorption capacities of 52.28 ± 1.2 mg/g for Pb²⁺ and 43.73 ± 0.30 mg/g for Cu²⁺, based on the Langmuir isotherm model. These results highlight the potential of biochar from municipal organic waste as a low-cost adsorbent for heavy metal removal.