直接大红4BE的磷钨酸均相光催化还原脱色

以磷钨酸(H3PW12O40,PW12)为光催化剂,异丙醇(Isopropanol)作为电子给体的条件下对偶氮染料直接大红4BE进行均相光催化还原脱色研究,考察PW12用量、IS浓度、直接大红4BE和盐浓度等因素的影响,结果表明杂多蓝(PW1-2)对直接大红4BE具有明显的还原脱色作用.pH=2.0,直接大红4BE初始浓度50 mg·L-1,PW12浓度为600 mg·L-1,IS浓度为0.13mol·L-1,50 min直接大红4BE的脱色率可达到90.39%.4BE的光催化还原脱色速率随PW12和IS浓度的增加而增加,最后趋于恒定;直接大红4BE初始浓度增加,其光反应一级速率常数降低;PW12、IS和4BE浓度之间存在交互影响.离子强度增加,4BE脱色速率减小,表现为负的盐效应,推测4BE与光反应生成的杂多蓝(PW1-2)进行复合,然后发生电子转移引起偶氮染料还原脱色和杂多蓝氧化复原.本研究结果表明PW12/IS/UV能够有效用于偶氮染料直接大红4BE的还原脱色处理.

Photocatalytic Reductive Degradation of Direct Red 4BE by Posphotungstic Acid

The photoreductive degradation of Azo-dye Direct Red 4BE (4BE) in aqueous solution was studied in a batch photoreactor, with phosphatotungstic acid (H₃PW₁₂O₄₀, PW₁₂) as the homogeneous catalyst and isopropanol as the electron donor. The parameters such as concentrations of PW₁₂, isopropanol and 4BE, ionic strength were carefully evaluated. The results showed that 4BE could be reductively decolorized by heteropoly blue, which was produced by phosphatotungstic acid in the presence of isopropanol under UV irradiation. The decolorization rate reached 90.39% within 50 min at a pH value of 2.0, a 4BE initial concentration of 50 mg·L^-1, a PW₁₂ and IS concentration of 600 mg·L^-1 and 0.13 mol·L^-1, respectively. The decolonization rate of 4BE increased with the increase of PW₁₂ and isopropanol concentrations until reaching a constant value. However, the first-order rate constants k for the degradation of 4BE decreased with the increase of the 4BE initial concentration. Mutual effects were found between the concentration of isopropanol and PW₁₂ on the photocatalytic degradation of 4BE. Moreover, the concentration of salt showed a negative effect on the photoreductive degradation of 4BE. It was assumed that the charge-transfer occurred within the complex formed by heteropoly bule and 4BE, which led to the reduction of 4BE and regeneration of heteropoly bule. This study indicates that PW₁₂/isopropanol/UV system could be used for the reductive degradation of azo dyes.