Preparation And Photocatalytic Activity Of Modified Bismuth Tungstate

Nowadays,with the continuous deterioration of the environment,efficient management and restoration of environmental pollution has become urgent.Due to the advantages of mild conditions and high chemical stability,photocatalytic technology is widely used to solve wastewater with high color,high organic content,high toxicity and alkaline,such as printing and dyeing wastewater and industrial wastewater.As a visible light responsive semiconductor photocatalyst,bismuth tungstate is nontoxic and has unique layered structure.However,bismuth tungstate has a wide band gap and narrow light response range,resulting in low photocatalytic efficiency.In this paper,according to the physical and chemical properties of Bi₂WO₆,the morphology control and non-metallic doping were used to control the band gap structure.The three-dimensional flower-like Bi₂WO₆ and KI-Bi₂WO₆ doped photocatalytic materials were developed by using the surfactant PVP K30 and KI.The relationship between their morphology,optical properties and photocatalytic performance was investigated.The photogenerated carrier migration mechanism and photocatalytic reaction mechanism of bismuth tungstate-based materials for the degradation of target pollutants were discussed.The main research contents are as follows:（1）Optimization of preparation conditions and photocatalytic properties of self-assembled bismuth tungstate materials.PVP was used as a structural guide,and the crystal surface of Bi₂WO₆ was regulated to optimize the morphology of Bi₂WO₆ by using the characteristics of PVP that can adsorb and stabilize on the surface of nanoparticles.One-step hydrothermal method was used to optimize the morphology of bismuth tungstate by controlling the addition amount of PVP and the reaction temperature and adjusting the polarity of the solution.The photocatalytic experiment results showed that the photocatalyst prepared under the conditions of 0.04 g PVP and160°C reaction temperature showed the highest decolorization ability for rhodamine B due to its unique morphology and low recombination rate of electron-hole pairs.The reaction rate constant k was 0.0059 min^-1,5.36 times that of pure Bi₂WO₆.（2）Preparation and mechanism of iodine-doped bismuth tungstate.On the basis of using surfactant PVP to optimize the morphology of Bi₂WO₆,in order to further improve the photocatalytic performance of bismuth tungstate,non-metal element iodine was introduced to modify Bi₂WO₆ by non-metal doping,and the band structure of bismuth tungstate was controlled.The optimum preparation conditions of I-Bi₂WO₆were determined by single factor experiment and orthogonal experiment.The results showed that the charge distribution of Bi³⁺,W⁶⁺and O^2-in Bi₂WO₆ was changed when I^-entered the system,and the interlayer spacing of Bi₂WO₆ was increased.The recombination of electrons and holes was inhibited.At the same time,the absorption boundary of the composite photocatalyst was red-shifted,and the response range to visible light was expanded.The photocatalytic experiments showed that the photocatalyst prepared under the optimal preparation conditions showed the highest decolorization ability for rhodamine B under visible light irradiation,with the k value of 5.29 times that before the addition of KI and 28.36 times that of pure Bi₂WO₆.（3）Effect of I_3.00-Bi₂WO₆ photocatalyst on Rhodamine B treatment.Through a series of experiments to explore the influencing factors of photocatalysis,it is found that the initial concentration of rhodamine B is 10 mg/L,the dosage concentration of catalyst is 2.0 g/L,and the initial p H value is 7.The photocatalytic degradation of rhodamine B is the best.Within 130 min,the color removal rate of rhodamine B can reach 96.90%,and the removal rate of COD can reach 68.50%.