Removal of arsenic and heavy metals from soil-washing effluents of contaminated mine sites using a novel Fe-assisted electrodeposition approach, amino-functionalized magnetic biochar, and chitosan-based column filtration systems

Arsenic contamination of environmental systems has aroused a great deal of public interest due to its toxicological properties. This study investigates the efficiency of three novel approaches including: iron-assisted electrodeposition, lime, and adsorption using biochar and chitosan-based columns for arsenic removal from highly contaminated effluents generated from pilot soil washing tests of a contaminated mine site with 32,000 mg/kg arsenic in Northwest Territories, Canada. In a first-of-its-kind approach, Fe-assisted electrodeposition achieved 99% arsenic removal from soil washing effluents within 10 h using iron(III) sulfate, concurrently yielding FeAs solids on the cathode as a potential value-added byproduct. Similarly, application of lime resulted in 99% arsenic removal with precipitation of calcium arsenates. Amino-functionalized magnetic biochar exhibited maximum adsorption capacities of 26.74 mg g −1 for As(III) and 11.31 mg g −1 for As(V). A layered column of magnetic biochar, zeolite, activated carbon, and a chitosan-enhanced sand filtration system achieved almost complete arsenic removal (99%). The results of column tests demonstrated highly effective arsenic removal, alongside substantial co-removal of other toxic metals including lead, zinc, antimony, cadmium, uranium, and cobalt by up to 99% from soil washing effluents, underscoring the practical applicability of the proposed methods in real-world remediation scenarios. The combined techniques used in this study can be employed as a novel, eco-friendly, and cost-effective solution for arsenic remediation in wastewater generated from soil washing systems in mining-impacted environments. • Fe assisted-electrodeposition removed >99% As. • Fe As solids formed via iron-assisted electrodeposition. • Amino-functionalized magnetic biochar enhances As adsorption. • Chitosan-based columns reduced As and metals by up to 99%. • Lime applications dramatically reduced As and metals.