Disclosing the influence mechanism of facet-dependent pyrite photo-activation and photo-dissolution processes on the reduction of Cr(VI).

The photo-activation and photo-dissolution processes of pyrite (FeS) can affect the environmental behavior of the co-existing hexavalent chromium (Cr(VI)). But the photochemical performance of FeS is intimately dependent on its exposed facets. Herein, FeS nanosheets (FeS NS) and FeS nanocubes (FeS NC) with the dominant exposed facets of (001) and (210)/(100) respectively are prepared. The more Fe, Fe, and SO are released in the FeS NS system than the other system due to its more excellent generation ability of photogenerated electrons and reactive oxygen species. The higher surface energy on (001) facet leads to the faster dissolution rate of FeS NS. Due to the optimal production ability of photogenerated electrons and Fe of (001) facet, the much higher Cr(VI) elimination efficiency in the FeS NS system is observed than that in the FeS NC (72.8%) system within 120 min. This work could help to unveil the influence of FeS on the fate of Cr(VI) in surface environment, and offer a theoretical support to clarify the influence of heavy metal ions on the iron sulfide minerals.