MnFe-layered double hydroxides grown on spherical SiO₂ to construct core-shell heterostructures for enhanced simultaneous photocatalytic redox Reactions of Cr(VI) and As(III)

Synergic oxidation and reduction of As(III) and Cr(VI) offer unique advantages for wastewater treatment. Herein, we report the fabrication of MnFe layered double hydroxide (LDH) nanoplatelets arranged on the surface of a SiO₂ nanosphere to form a novel visible-active LDH@SiO₂ core-shell photocatalyst. The activity of the samples was evaluated by observing the simultaneous oxidation of As(III) and reduction of Cr(VI) under visible light irradiation. The remarkably enhanced photocatalytic activity of LDH@SiO₂ can be elucidated in terms of efficient charge carrier generation, transport, and separation owing to the well-contacted core/shell interface, high surface area, mesoporous surface, and surface hydrophilicity. The composites exhibited considerably high activities for oxidation of As(III) and reduction of Cr(VI) when they coexisted, which were approximately 2 and 2.2 times higher than the presence of As(III) or Cr(VI) along. The photocatalytic mechanism was investigated using radical scavenger studies. The result supported that the redox reactions can be performed simultaneously via a synergistic oxidation-reduction mechanism in the presence of LDH@SiO2 core-shell photocatalyst under visible light irradiation. This work provides new paths for simultaneous mitigation of As(III) and Cr(IV) contamination by employing LDH-based photocatalyst and proves its bright potential to treat wastewater.