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首页> 外文期刊>Journal of Environmental Science and Health. A, Toxic/Hazardous Substances & Environmental Engineering >Different Net Effect of TiO_2 Sintering Temperature on the Photocatalytic Removal Rates of 4-Chlorophenol, 4-Chlorobenzoic Acid and Dichloroacetic Acid in Water
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Different Net Effect of TiO_2 Sintering Temperature on the Photocatalytic Removal Rates of 4-Chlorophenol, 4-Chlorobenzoic Acid and Dichloroacetic Acid in Water

机译：TiO_2烧结温度对水中4-氯酚，4-氯苯甲酸和二氯乙酸的光催化去除率的不同净影响

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Our purpose was to show that the sintering temperature of TiO_2 can have a different net effect (thought to arise from a decrease in surface area against a decrease in recombination rate of charge carriers) on the photocatalytic removal rate of various organic pollutants in water. For that, we have chosen four chlorinated pollutants, viz. 4-chlorophenol (4-CP), 2,5-dichlorophenol (2,5-DCP), 4-chlorobenzoic acid (4-CBA) and dichloroacetic acid (DCAA). Their photocatalytic removal was studied over four TiO_2 samples (from Millennium Chemicals or affiliate) all obtained identically by TiOSO_4 thermohydrolysis with subsequent calcination at various temperatures, TiO_2 Degussa P25 was used for comparison. At equal TiO_2 mass in the slurry photoreactor, the pseudo-first-order removal rate constant k increased with the calcination temperatures for the three aromatic pollutants, whereas it was the opposite for the aliphatic acid. Results obtained with P25 were consistent with the reasoning based on the combined effects of surface area and charge recombination rate. Similar k values for 4-CP and 2,5-DCP, irrespective of the TiO_2, further illustrate the importance of the molecular structure. For 4-CBA, the possibility of decarboxylation in addition to an attack on the ring, as well as a much higher extent of adsorption, can explain a higher k with respect to the chlorophenols. The implication of these results is that the hole attack mechanism for carboxylic acids is much more sensitive to surface area variation than would be the (diffusible) OH radical mechanism for aromatics which could react in the near-surface solution-phase.
机译：我们的目的是表明TiO_2的烧结温度对水中各种有机污染物的光催化去除率具有不同的净效应（这是由于表面积的减少与电荷载流子的复合率的降低有关）。为此，我们选择了四种氯化污染物，即。 4-氯苯酚（4-CP），2,5-二氯苯酚（2,5-DCP），4-氯苯甲酸（4-CBA）和二氯乙酸（DCAA）。在通过TiOSO_4热水解并随后在不同温度下煅烧的四个TiO_2样品（均来自Millennium Chemicals或子公司）上对它们的光催化去除进行了研究，使用TiO_2 Degussa P25进行比较。在淤浆光反应器中，当TiO_2质量相等时，三种芳族污染物的伪一级去除率常数k随着煅烧温度的升高而增加，而对于脂族酸则相反。用P25获得的结果与基于表面积和电荷复合率的组合效应的推论一致。与TiO_2无关，4-CP和2,5-DCP的相似k值进一步说明了分子结构的重要性。对于4-CBA，除了对环的攻击外，脱羧的可能性以及更高的吸附程度也可以解释为相对于氯酚而言更高的k。这些结果的含义是，与可能在近表面溶液相中反应的芳香族化合物的（可扩散）OH自由基机理相比，羧酸的空穴侵蚀机理对表面积变化更为敏感。

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