Preparation Of Bi-doped TiO₂/montmorillonite Composites And Their Photocatalytic Degradation Of Rhodamine B

Dye wastewater is characterized by high chroma,high organic content,complex and toxic ingredients,which cause serious harm to the environment and human health.Efficient treatment of dye wastewater has always been the focus of environmental governance.In recent years,photocatalytic technology has become an emerging method for treating dye wastewater due to its low cost,high efficiency,and no secondary pollution.Semiconductor photocatalysts represented by TiO₂ have been extensively studied.However,the large band gap,poor adsorption,high photogenerated carriers recombination rate,and recycling difficulty make TiO₂ subject to many restrictions in practi-cal applications.Therefore,in this paper,Bi was doped into the TiO₂ lattice by the solgel method to improve the band gap and the separation of photogenerated carriers.And the photocatalyst was loaded on montmorillonite with a large specific surface area and layered structure to enhance the adsorption and recyclability.Finally,Bidoped TiO₂/montmorillonite composite was prepared,and the structural characteristics and optical properties of the composite were studied.Moreover,the photocatalytic performance of the composite under visible light was explored through the photocatalytic degradation tests with rhodamine B as the simulated dye wastewater.The research results showed that Bi-doped TiO₂/montmorillonite composite had the highest photocatalytic activity when the Bi/Ti molar ratio was 7%,the mass fraction of montmorillonite suspension was 2%,the calcination temperature was 600?,and the calcination time was 3 h.TiO₂ in the composite was mainly anatase phase,and Bi was doped into the TiO₂ lattice by replacing Ti⁴⁺with Bi³⁺.After doping,the specific surface area of the composite was increased to 123.62 m²/g,the band gap was reduced to 2.80 e V,and the separation of photogenerated carriers was also enhanced.In the experiment of photocatalytic degradation of rhodamine B by the composite under visible light,it was found that Bi-doped TiO₂/montmorillonite composite had a greater ad-sorption capacity than TiO₂,sodium montmorillonite,and TiO₂/montmorillonite com-posite.The adsorption equilibrium could be reached at 25 min,and the adsorption process conformed to the pseudo-second-order kinetic equation.The degradation rate of Rhodamine B could be improved by an acidic environment and a suitable concentration of solution.The degradation effect was best when the pH of the rhodamine B solution was 2.1,the initial concentration was 10 mg/L,and the composite dosage was 0.5 g/L.After 30 min of dark adsorption and 150 min of light,the degradation rate could reach97.12%.And the photocatalytic process could be described by the Langmuir-Hinshlwood first-order kinetic equation.The active species that played a major role in the reaction system were holes and superoxide radicals,which underwent redox reactions with rhodamine B.In addition,reusing experiments showed that the Bi-doped TiO₂/montmorillonite composite had excellent stability.