Effect of Cr(VI) on photocatalytic of xanthate and synergistic mechanism
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摘要: 为进一步研究黄药和Cr(VI)共存体系中,Cr(VI)对黄药光降解性能的影响以及两者协同作用机制,本文以煤矸石/钒酸铋(CG/BiVO4)为光催化剂,黄药和Cr(VI)共存体系为研究对象,通过光催化活性测试以及紫外光谱、红外光谱、离子色谱和猝灭实验等技术手段,深入研究黄药光氧化和Cr(VI)光还原过程以及两者之间的协同作用机制。结果表明,在黄药和Cr(VI)的共存体系中,两者之间存在显著的协同效应,当黄药浓度为25 mg/L、pH=7、催化剂投加量为1.5 g/L、Cr(VI)浓度为2.0 mg/L、反应480 min时,CG/BiVO4对黄药和Cr(VI)的去除率均达最佳,分别是98.81%和88.80%;基于响应面法预测得到共存体系中黄药的降解率为94.79%,与实际降解率相差 3.82%,该响应面模型可预测共存体系下黄药的降解过程;共存体系中黄药的C=S振动优先发生变化,其次为C—O—C、S—H、S—C—S和丁基,光反应3 h形成中间产物过黄药(ROCSSO−),7 h的转化率最高为97.94%;协同作用机制研究发现,Cr(VI)光还原会迅速捕捉光生e−,黄药光降解会大量消耗h+,两者在光反应过程中不断消耗光生电子和空穴,一方面可抑制光生电子和空穴对的复合,延长光生电子空穴对的寿命;另一方面光生电子-空穴对的快速消耗,加速了光能向化学能的转化,提高了可见光利用率的同时生成大量光生电子空穴对,进而促使黄药和Cr(VI)的协同去除。Abstract: In order to further study the effect of Cr(VI) on the photodegradation of xanthate and its synergistic mechanism in the co-existing system of xanthate and Cr(VI), the photocatalyst of coal gangue/bismuth vanadate (CG/BiVO4) was used, xanthate and Cr(VI) coexisting systems were studied by photocatalytic activity test, UV, FTIR, ion chromatography and quenching experiments, the photooxidation of xanthate and photoreduction of Cr(VI) and their synergistic mechanism were explored. The results show that there is a significant synergistic effect between the photo-oxidation of xanthate and photo-reduction of Cr(VI) in the co-existence system of xanthate and Cr(VI). Then, at the xanthate of 25 mg/L and the pH value of 7, with the dosage of catalyst being 1. 5 g/L, at the Cr(VI) of 2.0 mg/L, the removal rate of xanthate and Cr(VI) by CG/BiVO4 are the best during a period of 480 min, reaching 98.81% and 88.80% respectively. The predicted degradation rate of xanthate is 94.79% by response surface methodology, lower 3.82% than the actual degradation rate, which indicates that the model can be used to predict the degradation of xanthate in the co-existing system. In the co-existing system, the vibration of C=S is changed first, followed by C—O—C, S—H, S—C—S, butyl, and the intermediate product peroxy xanthate (ROCSSO−) is formed after the visible light illumination 3 h , the highest conversion of sulfur is reached 97.94% after the visible light illumination 7 h. The synergistic mechanism analysis shows that the photogenerated e− are rapidly captured in the photo-reduction of Cr(VI) and photogenerated h+ are consumed by xanthate photodegradation. The photogenic electron and hole pairs are consumed, on the one hand, due to the inhibition of photogenerated electrons and holes recombination, the lifetime of photogenerated electron and hole pairs are prolonged, on the other hand, the rapid consumption of photogenerated electron-hole pairs accelerates the conversion of light energy to chemical energy, generating a large number of photogenerated electron-hole pairs, therefor promoting the synergistic removal of xanthate and Cr(VI) .
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Key words:
- Cr(VI) /
- xanthatet /
- photocatalysis /
- synergistic mechanism /
- degradation /
- removal
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表 1 影响CG/BiVO4光降解黄药的因素及水平
Table 1. Factors and levels affecting CG/BiVO4 photodegradation of xanthate
Factor Lever −1 0 +1 pH 7 9 11 m/(g·L-1) 1 2 3 C0/(mg·L−1) 6 8 10 CCr/(mg·L−1) 0.5 1.5 2.5 Notes: m—Catalyst dosage; C0—Initial concentration of xanthate; CCr—Concentration of Cr(VI). 表 2 共存体系中优化CG/BiVO4光降解黄药实验回归模型的方差分析
Table 2. Variance analysis of regression model in optimizing CG/BiVO4 photodegradation of xanthate in co-existing system
Source SS DF Mean square F value P value prob>F Model 22.73 14 1.62 236.55 <0.0001 A 9.36 1 9.36 1364.23 <0.0001 B 3.47 1 3.47 505.12 <0.0001 C 4.38 1 4.38 638.19 <0.0001 D 0.12 1 0.12 16.91 0.0011 AB 6.75 1 6.75 9.87 0.9527 AC 0 1 0 0 1.0000 AD 6.75 1 6.75 9.87 0.9527 BC 0 1 0 0 1.0000 BD 0 1 0 0 1.0000 CD 6.75 1 6.75 9.87 0.9527 A2 2.12 1 2.12 309.12 <0.0001 B2 2.12 1 2.12 309.03 <0.0001 C2 0.072 1 0.072 10.55 0.0058 D2 0.066 1 0.066 9.56 0.0080 Residual 0.096 14 18.63 Lack of fit 0.089 10 24.06 4.74 0.0736 Pure error 20.3 4 5.05 Cor total 22.83 28 Notes: A—Initial pH of the reaction; B—Catalyst dosage; C—Initial concentration of xanthate; D—Cr(VI) concentration; SS—Sum of squares; DF—Degree of freedom; F value—Ratio of the mean square to the residual term; P value prob—Influence degree value of each factor. -
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