UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia.
Beijing OriginWater Technology Co., Ltd, Beijing, China.
Water Res. 2020 Jun 15;177:115785. doi: 10.1016/j.watres.2020.115785. Epub 2020 Apr 8.
In the present study, radiolabelled formate was used as a probe compound in order to gain mechanistic insight into the catalytic ozonation process using a commercially available iron oxide-impregnated activated carbon catalyst. We simultaneously analysed the adsorptive and oxidative removal of formate in order to determine the contribution of the catalyst to adsorption and oxidant generation processes respectively. Our results show that the presence of the catalyst enhanced ozone decay as well as the rate and extent of formate oxidation at pH 3.0 compared to that observed in the presence of ozone alone as a result of oxidant generation via O-Fe oxide interaction. A reduction in rate and extent of formate oxidation on addition of t-butanol and Cl (known hydroxyl radical (OH) scavengers under acidic conditions) provides evidence that the oxidant generated during catalytic ozonation at pH 3.0 is OH. Moreover, the oxidation of formate during catalytic ozonation mostly occurs at the solid-liquid interface and/or in bulk solution with adsorption playing no role in the overall oxidation process with this finding supported by the exceptionally high oxidation efficiency compared to the extent of adsorption observed when no O was added. While catalytic ozonation was effective in formate oxidation at pH 3.0, the presence of the catalyst did not lead to an increase in either the rate or extent of formate oxidation at pH 7.3 and 8.5 suggesting that only protonated iron oxide surface sites generate strong oxidant(s) on interaction with O. Based on our understanding of the processes operating during the ozonation and catalytic ozonation processes, a mathematical model has been developed that adequately describes the experimental results obtained here. Overall, this study shows that systematic measurement of ozone decay, removal of the parent compound as well as formation of the oxidized products under well controlled conditions are required for unequivocal elucidation of the mechanism of catalytic ozonation.
在本研究中，使用放射性标记的甲酸盐作为探针化合物，以便深入了解使用市售氧化铁浸渍活性炭催化剂进行催化臭氧化过程的机理。我们同时分析了甲酸盐的吸附和氧化去除，以确定催化剂对吸附和氧化剂生成过程的贡献。我们的结果表明，与单独使用臭氧相比，在 pH 3.0 下，催化剂的存在增强了臭氧衰减以及甲酸盐氧化的速率和程度，这是由于 O-Fe 氧化物相互作用产生氧化剂所致。在添加叔丁醇和 Cl（在酸性条件下已知是羟基自由基 (OH) 清除剂）的情况下，甲酸盐氧化速率和程度的降低提供了证据，表明在 pH 3.0 下催化臭氧化过程中生成的氧化剂是 OH。此外，在 pH 3.0 下的催化臭氧化过程中，甲酸盐的氧化主要发生在固液界面和/或在 bulk 溶液中，吸附在整个氧化过程中不起作用，这一发现得到了支持，因为与未添加 O 时观察到的吸附程度相比，氧化效率异常高。虽然在 pH 3.0 下催化臭氧化对甲酸盐氧化有效，但催化剂的存在并没有导致在 pH 7.3 和 8.5 下甲酸盐氧化的速率或程度增加，这表明只有质子化的氧化铁表面位点在与 O 相互作用时才会生成强氧化剂。基于我们对臭氧化和催化臭氧化过程中发生的过程的理解，已经开发了一个数学模型，该模型能够很好地描述这里获得的实验结果。总的来说，这项研究表明，在明确阐明催化臭氧化机制时，需要在严格控制的条件下系统地测量臭氧衰减、母体化合物的去除以及氧化产物的形成。
