Large-scale chicken manure-derived biochar for efficient zinc removal from real zinc smelter wastewater

This study evaluated the performance of chicken manure-based biochar (CMBC), produced using a large-scale pyrolysis system (15 tons/day), for Zn removal from real zinc smelter wastewater. CMBC exhibited a maximum experimentally observed Zn adsorption amount of 36.37 mg/g. Kinetic and equilibrium data were better described by the Elovich and Langmuir models, respectively. Physicochemical characterization indicated that Zn removal involved multiple processes. Ion exchange accounted for an estimated 37.4% of Zn removal based on the release of exchangeable cations. XRD analysis and the decrease in dissolved phosphate concentration suggested the possible involvement of Zn-containing phosphate phases. FT–IR and XPS analyses further indicated possible interactions between Zn and oxygen-containing functional groups on the CMBC surface. RSM analysis identified reaction time, temperature, and CMBC dose as statistically significant factors affecting Zn removal, whereas pH was not statistically significant within the investigated range. Under the optimized conditions, the predicted Zn removal efficiency was 99.2%, and experimental validation using real zinc smelter wastewater achieved 97.3%, reducing the Zn concentration from 1,871.7 to 50.3 mg/L. These findings highlight the potential of unmodified CMBC produced using a large-scale pyrolysis system for treating highly Zn-contaminated industrial wastewater.