Enhanced adsorption of antimonate by ball-milled microscale zero valent iron/pyrite composite: adsorption properties and mechanism insight

Ball-milling is considered as an economical and simple technology to produce novel engineered materials. The ball-milled microscale zero valent iron/pyrite composite (BM-ZVI/FeS2) had been synthesized through ball-milling technology and applied for highly efficient sequestration of antimonate (Sb(V)) in aqueous solution. BM-ZVI/FeS2 exhibited good Sb(V) removal efficiency (≥ 99.18%) at initial concentration less than 100 mg Sb(V)/L. Compared to ball-milled zero valent iron (ZVI) and pyrite (FeS2), BM-ZVI/FeS2 exhibited extremely higher removal efficiency due to the good synergistic adsorption effect. BM-ZVI/FeS2 showed efficient removal performance at broad pH (2.6–10.6). Moreover, the coexisting anions had negligible inhibition influence on the Sb(V) removal. The antimony mine wastewater can be efficiently remediated by BM-ZVI/FeS2, and the residual Sb(V) concentrations (< 0.96 μg/L) can meet the mandatory discharge limit in drinking water (5 μg Sb/L). Experimental and model results demonstrated that endothermic reaction and chemisorption were involved in Sb(V) removal by BM-ZVI/FeS2. The XRD and XPS analyses confirmed that the complete corrosion of ZVI occurred on BM-ZVI/FeS2 after Sb(V) adsorption, resulting in the enhanced Sb(V) sequestration. Mechanism analyses showed that the excellent removal performance of BM-ZVI/FeS2 was ascribed to the high coverage of iron (hydr)oxide oxidized from ZVI. Because of the advantages of economical cost, high Sb(V) removal capacity and easy availability, BM-ZVI/FeS2 offers a promising adsorbent for Sb(V) remediation.