Tunable Fe-deficiency modified sodium ferric silicate for improving photo-Fenton-like activity

Photo-Fenton-like process of the Fe-based semiconductors depends on the reversible Fe(III)-Fe(II) pair strongly, which is highly sensitive to their surface structure. Herein, a facile ball-milling method was developed to obtain a novel Fe-deficient sodium ferric silicate (SFS) by facilitating the breakage of weak Fe-O bonds. The released Fe 3+ from lattice was found, leading to the formation of Fe-deficient structure at the surface of catalyst. Furthermore, the Fe-deficiency could be controlled by adjusting the milling conditions. In comparison with the pristine SFS, Fe-deficient SFS shows improved transfer efficiency of the photon-activated species and enhanced photo-Fenton-like catalytic performances. The introduced surface Fe-deficiency not only traps photogenerated electrons, but also provides more active sites in the photo-Fenton-like process. The removal rate of ciprofloxacin and Cr(VI) exhibited 5.12 and 2.83 folds superior to those of the pristine counterpart, respectively. Furthermore, Fe-deficient SFS showed an excellent photocatalytic sustainability for ciprofloxacin oxidation and Cr(VI) reduction. The possible degradation pathways and the intermediates of ciprofloxacin molecules were also investigated by liquid chromatograph-mass spectrometer. The surface Fe-deficient structure was attributed to facilitating carriers separation and active species production efficiently in this work.