Arsenic removal using foundry dust: Characterization, adsorption mechanisms, and application in acid mine drainage treatment

This study investigated the removal of arsenic (As) using foundry dust (FD) generated from metal casting processes. FD is primarily composed of Si, Fe, and Ca, and possesses magnetic properties that facilitate separation and recycling. It demonstrated effective adsorption capabilities for both As(III) and As(V), with maximum adsorption capacities of 5.15 mg/g for As(III) and 9.34 mg/g for As(V) using the Langmuir equation. FD can remove As within a pH range of 3–9, with adsorption capacity increasing as pH rises. The As removal mechanism involves complex processes including ligand exchange, surface precipitation, redox reactions, and hydroxyl radical (•OH) generation. Notably, FD can act as either an oxidant or reductant depending on the surrounding environment and As species, resulting in different removal pathways for As(III) and As(V). In experiments using actual acid mine drainage (AMD), FD effectively reduced As concentrations below the Korean regulatory standard (0.05 mg/L). FD is easily recoverable and recyclable due to its magnetic properties, and is effective for arsenic removal under various environmental conditions through a composite adsorption/oxidation-reduction mechanism.