pH对低温燃烧法合成钨酸铋光催化降解罗丹明B的影响

Effects of Solution p H on Photocatalytic Degradation of Rhodamine B Using Bismuth Tungstate Prepared by Low-temperature Combustion Method

以低温燃烧法制备钨酸铋（LCM-Bi2WO6）,并表征了其晶体结构、形貌特征、等电点及紫外漫反射谱,同时以染料罗丹明B（Rh B）为目标污染物（25 mg/L,p H=4）,考察了所制备Bi2WO6的吸附性能和光催化性能,并探讨了Rh B溶液p H（1、4、7、10）及酸度调节剂成分（盐酸和硫酸）的影响。结果表明,所制备Bi2WO6为正交相,吸收极限波长为455 nm,禁带宽度为2.72 e V,晶格粒径为14.7 nm,等电点为3.43;其对Rh B的吸附和光催化效果强于水热法制备Bi2WO6和二氧化钛（TiO2）。不同p H溶液中,LCM-Bi2WO6对Rh B的吸附过程和光催化过程分别符合准二级动力学方程和一级动力学方程式,且吸附平衡量（7.48~21.93 mg/g）和光催化速率常数（0.0197~0.1181 min-1）均随p H降低而增大。LCM-Bi2WO6对Rh B的光催化降解主要由·OH所致。光催化过程中,Rh B紫外可见光谱的蓝移现象揭示LCM-Bi2WO6可通过脱乙基-共轭显色基团断裂途径降解Rh B。以H2SO4调节酸度时,SO42-离子可被Bi2WO6强吸附,从而使得LCM-Bi2WO6对Rh B的平衡吸附量（qe为6.03 mg/g）和光催化速率（kv为0.115 min-1）远小于HCl调节（qe为21.93 mg/g,kv为0.1181 min-1）时对Rh B的平衡吸附量和光催化速率。

Bismuth tungstate（Bi2WO6） was synthesized by low-temperature combustion method（LCM） and characterized by diffuse reflectance spectroscope（DRS）, X-ray diffraction（XRD）, scanning electron microscope（SEM） and Zeta potential. The effects of solution p H and acidity regulator types on the photocatalytic degradation of Rh B by LCM-Bi2WO6 were investigated. Results showed that LCM-Bi2WO6 was an orthorhombic crystal and its wavelength of maximum absorption, forbid bandwidth, lattice size and isoelectric point were 455 nm, 2.72 e V, 14.7 nm and 3.43,respectively. Stronger adsorption and photodegradation of Rh B（25 mg/L, p H=4） using LCM-Bi2WO6 as photocatalyst was observed, compared with using Ti O2 or Bi2WO6 prepared by hydrothermal method as photocatalyst. Adsorption and photodegradation of Rh B by LCM-Bi2WO6 satisfied the pseudo-second-order kinetic equations and first order kinetic equations, respectively. Equilibrated adsorption capacity（7.48-21.93 mg/g） and photodegradation rate constants（0.0197-0.1181 min-1） of RhB by LCM-Bi2WO6 were positively related to solution p H. Photocatalytic degradation of RhB by LCM-Bi2WO6 was mainly triggered by free hydroxyl groups（·OH）. Blue shifts of Rh B ultraviolet-visible spectrum indicated its degradation through ethyl removal and conjugated groups break pathway. Weaker adsorption（qe=6.03 mg/g） and photodegradation（kv=0.115 min-1） of Rh B by LCM-Bi2WO6 using H2SO4 as acidity regulator were observed compared with using HCl（qe=21.93 mg/g, kv=0.115 min-1） as acidity regulator, because of SO2-4strong adsorption to LCM-Bi2WO6.