硅藻土/BiVO_(4)复合光催化剂的制备及性能研究

Synthesis and properties of the diatomite/BiVO_(4) composite photocatalysts

采用液相沉淀法制备了不同硅藻土含量(5%~80%)的硅藻土/BiVO_(4)复合材料,利用XRD和UV-Vis对样品进行了表征。结果表明,复合材料为单斜BiVO_(4)、四方BiVO_(4)和SiO_(2)混合相。升高煅烧温度可使BiVO_(4)向单斜相转化,且在较高煅烧温度时,增大硅藻土的含量,有助于BiVO_(4)进一步转化为单斜相。硅藻土含量为5%~30%的样品的光降解率比BiVO_(4)有不同程度的提升,硅藻土的最佳含量为10%。在煅烧温度450℃,光催化时间2 h,罗丹明B浓度10 mg/L的条件下,复合材料的去除率和光降解率分别高达100%和60.41%。空穴是材料光降解罗丹明B的主要活性物种,复合材料光催化性能提升可归因于硅藻土良好的吸附性、对BiVO_(4)的分散性以及形成的单斜相BiVO_(4)/四方相BiVO_(4)/SiO_(2)混相p-n异质结,其提升了材料对罗丹明B的吸附,增大了表面活性位点和比表面积,加速了光生载流子的分离与传输,在有机污染物废水处理方面具有较好的应用前景。

The diatomite/BiVO_(4)composite materials with different diatomite content(5%~80%) were prepared by liquid precipitation method. The samples were characterized by XRD and UV-Vis. The results show that the composite consists of monoclinic BiVO_(4), tetragonal BiVO_(4)and SiO_(2). BiVO_(4)can be transformed into monoclinic phase by increasing the calcination temperature, and at a higher calcination temperature, the increase of diatomite content is conducive to the further transformation of BiVO_(4)into monoclinic phase. Compared with BiVO_(4), the photodegradation efficiencies of the composites with the diatomite contents of 5%~30% are improved in different degrees, and the optimum content of the diatomite is 10%. Under the conditions of calcination temperature of 450 ℃, photocatalytic time of 2 h,rhodamine B concentration of 10 mg/L, the removal and photodegradation efficiencies of the sample for rhodamine B can reach 100% and 60.41%, respectively. Holes are the main active species for the photodegradation of rhodamine B. The enhanced photocatalytic performance of the composite materials can be attributed to the good adsorption of the diatomite, the good dispersion of BiVO_(4)and the formation of monoclinic BiVO_(4)/tetragonal BiVO_(4)/SiO_(2)miscible p-n heterojunctions, which improve the adsorption for rhodamine B, increase the surface active site and specific surface area, and accelerate the separation and transmission of photoinduced carriers, with promising application for the treatment of organic pollutant wastewater.