Adsorptive-photocatalytic performance and mechanism of Me (Mn,Fe)-N co-doped TiO2/SiO2 in cyanide wastewater

Abstract

In this study, Me (Mn, Fe)-N co-doping is used to improve the treatment efficiency of TiO2/SiO2 on cyanide wastewater, and to explore the reasons for the change in the catalytic performance of the material. The characteristics of the materials are studied by field emission scanning electron microscopy (FESEM)/ energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Brunner−Emmet−Teller (BET), Thermal gravimetric analyzer (TGA) and UV–vis spectrometer, which indicate that TiO2 is anatase type with a particle size of 10–11 nm; Doping elements (Fe, N, and Mn) are well dispersed in the material; Fe or Mn doping can increase the specific surface area of TiO2, while N doping has the opposite effect. Further, the comparison of the treatment effects of cyanide wastewater by TiO2/SiO2 doped with single (N, Fe, Mn) and co-doped with Me (Mn, Fe)-N demonstrates that the materials co-doped with Mn-N possesses the most efficient photocatalytic performance. The degradation efficiency of cyanide reaches 97.09% and the adsorption removal efficiencies of copper and zinc ions reach 88.54% and 100% under light irradiation within 2 h. The mechanism of Mn-N co-doped synergistic catalysis has been studied by combining X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). This indicates that the reason for the significant improvement of the photocatalytic performance of the material is that co-doping produced a new electronic states that overlaps the valence band of TiO2, which promotes the transfer of photogenerated carriers and reduces the electron-hole recombination. This work can efficiently and cleanly decompose cyanide while adsorbing and removing heavy metals, which may be of great significance to the development of the gold industry.