N掺杂TiO2可见光催化降解有机物机理研究
Mechanisms research on visible irradiation degradation of organics by nitrogen doped TiO2 photocatalysts
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摘要: 实验研究了掺杂N的TiO2光催化剂在可见光下对有机物的降解机理，研究方法有：加入自由基俘获剂探索对反应速率的影响、有机物降解过程TOC与脱色比较，化学探针法测定了实验中存在的HO·。结果表明，有机物在脱色的同时苯环也在断裂，说明有机物的降解是受无选择性的氧化剂攻击而完成；除亚甲基蓝以外，加入自由基俘获剂对可见光反应速率均有抑制现象，证明自由基的攻击是有机物可见光催化降解的主要途径。分别以二甲基亚砜和水杨酸为分子探针，实验结果证明了光催化反应系统中存在HO·物种，前者与HO·反应形成特定的偶氮结构有机物在425 nm处有吸收，后者与HO·反应生成2，3-二羟基苯甲酸和2，5-二羟基苯甲酸。亚甲基蓝、苯酚和水杨酸经5 h的可见光催化降解后，其TOC分别降低了62.8%、78.9％和96.0％，说明掺杂N的TiO2有较强的可见光催化降解有机物能力。Abstract: Organic model pollutants degeneration mechanisms of photocatalytic reaction by nitrogen doped TiO2 under visible irradiation were studied. Effects of several free radical capturers on rate of photocatalytic reactions were discussed. Chemistry probe methods were used in the experiments and results demonstrated that HO· existed in the visible irradiation reaction systems. Benzene ring breaking and decolorizing of the selected organic substances were simultaneously in the reaction system， which explained that the degeneration of the organisms was completed by the non-selective oxidant attack. The substances produced by HO· attack of dimethyl sulphoxide was azo dye which had maximum absorbance at 425 nm. 2，3-DHBA (dihydroxy benzyl acid) and 2，5-DHBA were the initial products of salicylic acid reaction with HO·， these substances existing in the visible reaction systems demonstrated the radical mechanisms of the reaction. After 5 h visible light photochemical catalysis degradation， TOC concentration of the methylene blue， phenol and salicylic acid reduced 62.8%， 78.9% and 96.0%， respectively， these results demonstrated that nitrogen doped TiO2 can degrade organics by visible irradiation.
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Key words:
- nitrogen doping /
- TiO2 /
- photocatalysis /
- organics /
- degradation /
- HO·
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