Photocatalytic reduction of Cr(VI) over cinder-based nanoneedle in presence of tartaric acid: Synergistic performance and mechanism.

Cr(VI) is a common heavy metal ion, which will seriously harm human body and environment. Therefore, the removal of Cr(VI) has become an attractive topic. In this work, cinder was used as a raw material to synthesize a nanoneedle material: γ-(AlOOH@FeOOH) (γ-Al@Fe). The physicochemical properties of γ-Al@Fe were thoroughly characterized, and its effectiveness as a catalyst for photocatalytic reduction of Cr(VI) was evaluated. The results showed that Cr(VI) could be efficiently reduced by γ-Al@Fe in the presence of tartaric acid (TA) under visible light. The variable factors on the reaction were investigated in detail, and the results showed that under optimal conditions (γ-Al@Fe 0.4 g/L, TA 0.6 g/L, pH 2), Cr(VI) was completely reduced within 7 min. Besides, scavenger experiments and EPR proved that O and CO played a significant role in the photocatalytic reduction of Cr(VI). TA acts as a sacrificial agent to trap the holes and generate strong reducing free radicals: CO. Dissolving O could react with electrons to generate O. This work discussed the performance and mechanism of photocatalytic reduction of Cr(VI) in detail, which provided a new idea for the resource utilization of solid waste and the treatment of heavy metal sewage.