Search

In the present work, phenol was used as a model molecule to the photocatalytic evaluation of TiO2 impregnated with iron sulphide and chlorine on a visible-light reactor. The iron–chlorine catalyst was prepared by incipient impregnation with the metal precursors, Fe (NO3)3 and NaCl on previously calcined TiO2. The catalyst was sulphurized with H2S at 300 °C for 1 h. The catalysts were prepared at different chlorine concentrations using HYDRA chemical equilibrium diagrams to obtain different fractions of FeCl+. The oxide catalysts were characterized with diffuse reflectance (DRS UV–Vis) and temperature programmed reduction analysis (TPR). Sulphurized catalysts were characterized with Raman spectrometry and X-ray photoelectron spectrometry (XPS). The FeS–2Cl/TiO2 catalyst presented 8.35 times higher photodegradation than TiO2 and 6.4 times higher compared to the FeS–0.25Cl/TiO2 catalyst. DRS and XPS showed similar results of band gap, proving that the catalyst remain stable after sulphurisation. The TPR results of FeS–2Cl/TiO2 showed an increment of 86.29% in Fe2+/Fe3+ compared to FeS–0.25Cl/TiO2. XPS and Raman results for oxide and sulphated iron species relation suggested that FeS–2Cl/TiO2 decreased 4.45% compared to FeS–0.25Cl/TiO2 catalyst. XPS semiquantitative for S/Fe results showed that the FeS–2Cl/TiO2 catalyst increased 73.17% in comparison to FeS–0.25Cl/TiO2. These results suggested the increment of sulphurisation degree for FeS–2Cl/TiO2. In this regard, the catalyst characterization results showed that the presence of FeCl+ (0.85 fractions) in solution before impregnation promoted the active sulphide species maintaining the band gap and improved the degradation of phenol on visible light.

In recent years, the search for solutions for the treatment of water pollution by toxic compounds such as phenols and chlorophenols has been increasing. Phenols and their derivatives are widely used in the manufacture of pesticides, insecticides, paper, and wood preservers, among other things. Chlorophenols are partially biodegradable but not directly photodegradable by sunlight and are extremely toxic—especially 2,4,6-trichlorophenol, which is considered to be potentially carcinogenic. As a viable proposal to be applied in the treatment of water contaminated with 2,4,6-trichlorophenol, this paper presents an application study of the thermally activated Mg/Fe layered double hydroxides as photocatalysts for the mineralization of this contaminant. Activated Mg/Fe layered double hydroxides were characterized by X-ray diffraction, thermal analysis, N2 physisorption, and scanning electron microscopy with X-ray dispersive energy. The results of the photocatalytic degradation of 2,4,6-trichlorophenol in aqueous solution showed good photocatalytic activity, with an efficiency of degradation of up to 93% and mineralization of 82%; degradation values which are higher than that of TiO2-P25, which only reached 18% degradation. The degradation capacity is attributed to the structure of the MgO−MgFe2O4 oxides derived from double laminate hydroxide Mg/Fe. A path of degradation based on a mechanism of superoxide and hollow radicals is proposed.