Photocatalytic Cr(VI) elimination over BUC-21/N-K2Ti4O9 composites: Big differences in performance resulting from small differences in composition

Abstract A series of BUC-21/N-K2Ti4O9 composites (B1NX) were facilely fabricated from BUC-21 and N-K2Ti4O9 via ball-milling, and they were fully characterized using various techniques. The photocatalytic reduction of Cr(VI) over the B1NX composites was investigated systematically under various conditions, including different light sources, pH values, hole scavengers, and inorganic ions, in both real lake water and tap water. The BUC-21/N-K2Ti4O9 composites demonstrated remarkable photocatalytic Cr(VI) reduction performance, good reusability, and stability under both UV and white light irradiation. The introduction of N-K2Ti4O9 into BUC-21 not only broadened its light absorption region to white light, but also strongly inhibited the recombination of the photo-generated electrons and holes. Mechanisms of photocatalytic Cr(VI) reduction under both UV light and white light were proposed and verified by electrochemical measurements, active species capture experiments, and ESR measurements.