Biochar-Modified Iron Tailings for Cr(VI) Removal from Acid Mine Drainage

Iron tailings, the major solid waste generated during iron ore beneficiation, possess substantial resource potential, but their utilization remains limited. Although iron tailings can adsorb Cr(VI)-containing oxyanions, their aggregation in aqueous systems restricts adsorption kinetics, resulting in only 24.4% Cr(VI) removal at an initial concentration of 30 mg/L. In this study, an economical biochar–iron tailings composite was synthesized via a one-step pyrolysis method, with biochar serving as a carbon framework to disperse iron tailings and enhance Cr(VI) removal. The composite achieved approximately 50% Cr(VI) removal at 30 mg/L, representing a significant improvement compared with raw iron tailings. In simulated acidic mine wastewater, under optimized conditions of pH 2, a dosage of 0.8 g/L, and 10 mg/L Cr(VI), the composite removed over 95% of Cr(VI) within 8 h and reached 99.95% removal after 24 h. These results demonstrate that biochar effectively alleviates iron tailings aggregation and improves adsorption performance while maintaining a relatively low treatment cost. This biochar–iron tailings composite provides a promising strategy for Cr(VI)-contaminated wastewater treatment and the high-value utilization of iron tailings.