Preparation of a coated Z-scheme and H-type SrTiO3/(BiFeO3@ZnS) composite photocatalyst and application in degradation of 2,4-dichlorophenol with simultaneous conversion of Cr(VI)

A novel coated Z-scheme and Heterojunction-type (Z-scheme and H-type) SrTiO3/(BiFeO3@ZnS) composite photocatalyst is prepared by isoelectric point and successive ionic layer adsorption and reaction methods. The coated Z-scheme and H-type SrTiO3/(BiFeO3@ZnS) composite photocatalyst is characterized. Some influence factors such as irradiation time, initial concentration, solution pH, sacrificial agents and recycling times on the photocatalytic activity of the coated Z-scheme and H-type SrTiO3/(BiFeO3@ZnS) composite photocatalyst under solar-light irradiation are considered in the degradation of 2,4-dichlorophenol with simultaneous conversion of Cr(VI). The possible photocatalytic reaction mechanism caused by the coated Z-scheme and H-type SrTiO3/(BiFeO3@ZnS) composite photocatalyst and photocatalytic degradation pathway of 2,4-dichlorophenol are proposed. The experimental results display that the coated Z-scheme and H-type SrTiO3/(BiFeO3@ZnS) composite photocatalyst has an excellent photocatalytic activity. Under optimized conditions, the degradation rate of 2,4-dichlorophenol and the conversion ratio of Cr(VI) are 91.32% and 97.87%, respectively. The high photocatalytic activity is attributed to the combination of Z-scheme and Heterojunction-type photocatalytic systems, which is beneficial to separate the photo-generated electrons and holes and accelerate the transfer of photo-generated electrons. The coated structure provides a relatively large oxidation surface, which is conductive to degrade organic pollutants and promote conversion of inorganic ions. It can be expected that this study may be helpful to design a promising photocatalyst for simultaneous degradation of organic pollutants and conversion of inorganic pollutants.