Detoxification and selective separation of Cr(VI) and As(III) in wastewater based on interfacial coupling in BiOBr with {110} facet under visible-light irradiation

Layered structural BiOBr with {110} facet exposure is a promising functional material for highly selective adsorption and separation of heavy metal ions in water purification. In this study, the distinct adsorption behaviors of As(III), As(V), and Cr(VI) on {110} facet were theoretically and experimentally investigated. The results suggested that uncharged As(III) was dominantly adsorbed on the [Bi2O2]2+ surface replacing the hydroxyl group, whereas Cr(VI) and As(V) oxyanions preferentially intercalated on {110} facet by exchange with Br- ions between the layers. Moreover, due to interfacial coupling configuration ([BiO-CrO4-OBi]-O-As(OH)2) between the surface and interlayer on {110} facet, the synergic removal of Cr(VI) and As(III) could be accelerated under photoexcitation to induce a direct electron transfer from surface AsIII to interlayer CrVI, forming AsV and CrIII. Subsequently, approximately 69.3% of Cr(III) and 98.6% of As(V) were readily desorbed in acidic conditions and a high concentration of Br- solution, respectively, to achieve simultaneous detoxification and selective separation.