School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Chemosphere. 2018 Nov;210:224-231. doi: 10.1016/j.chemosphere.2018.07.006. Epub 2018 Jul 4.
Fe(III) and carboxylic acids are ubiquitous in surface water and atmospheric water droplets. Numerous documents have reported the photochemistry of Fe(III)-carboxylate complexes, typically including Fe(III)-oxalate and Fe(III)-citrate. Our previous study preliminarily showed that oxalate enhances the photoreactivity of Fe(III)-citrate system. Here, we further investigate the synergistic effect of Fe(III)-citrate-oxalate binary system at different conditions with pharmaceutical amitriptyline (AMT) as the model pollutant. In the Fe(III)-oxalate system, the photodegradation of AMT decreased with increasing pH from 3.0 to 8.0. In the Fe(III)-citrate system, the optimal pH for AMT degradation is around 5.0 in the same pH range. For the Fe(III)-citrate-oxalate system, the photodegradation of AMT decreased with increasing pH, indicating the combined effect of both oxalate and citrate on the photoreactivity. The addition of oxalate to the Fe(III)-citrate system markedly accelerated the photodegradation of AMT. The Fe(III)-carboxylate binary system exhibited excellent photoreactivity and up to 90% AMT was removed after 30 min at pH 6.0 with Fe(III)/citrate/oxalate ratio of 10:150:500 (μM). Synergistic effect was observed in Fe(III)-citrate-oxalate binary system in the pH range of 5.0-8.0. The presence of oxalate promoted the depletion of citrate in the Fe(III)-citrate system. The higher concentration ratios of oxalate to citrate facilitated the synergistic effect in the Fe(III)-citrate-oxalate system. By LC-MS analyses, a possible pathway of AMT degradation was proposed based on hydroxyl radicals (OH) mechanism. This finding could be helpful for the better understanding of synergistic mechanism of Fe(III)-citrate-oxalate binary complexes, which will be of great potential application in environmental photocatalysis at near neutral pH.
三价铁和羧酸在地表水和大气水滴中无处不在。许多文献报道了三价铁-羧酸盐配合物的光化学性质，通常包括三价铁-草酸盐和三价铁-柠檬酸盐。我们之前的研究初步表明草酸盐增强了三价铁-柠檬酸盐体系的光反应性。在这里，我们进一步研究了三价铁-柠檬酸盐-草酸盐二元体系在不同条件下的协同作用，以药物阿米替林（AMT）为模型污染物。在三价铁-草酸盐体系中，随着 pH 值从 3.0 增加到 8.0，AMT 的光降解减少。在三价铁-柠檬酸盐体系中，在相同的 pH 范围内，AMT 降解的最佳 pH 值约为 5.0。对于三价铁-柠檬酸盐-草酸盐体系，随着 pH 值的增加，AMT 的光降解减少，表明草酸盐和柠檬酸盐对光反应性都有综合影响。在三价铁-柠檬酸盐体系中加入草酸盐显著加速了 AMT 的光降解。三价铁-羧酸盐二元体系表现出优异的光活性，在 pH 值为 6.0 时，三价铁/柠檬酸盐/草酸盐的比例为 10:150:500（μM），30 分钟后 AMT 的去除率达到 90%。在 5.0-8.0 的 pH 范围内观察到三价铁-柠檬酸盐-草酸盐二元体系的协同效应。草酸盐的存在促进了三价铁-柠檬酸盐体系中柠檬酸盐的消耗。草酸盐与柠檬酸盐的浓度比越高，三价铁-柠檬酸盐-草酸盐体系中的协同效应越明显。通过 LC-MS 分析，提出了基于羟基自由基（OH）机制的 AMT 降解可能途径。这一发现有助于更好地理解三价铁-柠檬酸盐-草酸盐二元配合物的协同机制，这对于近中性 pH 值环境光催化具有很大的潜在应用价值。
