Department of Chemical and Environmental Engineering, Escuela Universitaria de Ingeniería Vitoria-Gasteiz University of the Basque Country UPV/EHU, Nieves Cano, 12, 01006, Vitoria-Gasteiz, Spain.
Environ Sci Pollut Res Int. 2017 Jan;24(2):1105-1112. doi: 10.1007/s11356-016-7245-5. Epub 2016 Jul 28.
This paper deals with the changes of turbidity that are generated in aqueous solutions of phenol when they are oxidized by using different Fenton technologies. Results revealed that if the Fenton reaction was promoted with UV light, the turbidity that was generated in the water doubled. Alternatively, the use of ultrasonic waves produced an increase in turbidity which initially proceeded slowly, reaching intensities eight times higher than in the conventional Fenton treatment. As well, the turbidity showed a high dependence on pH. It is therefore essential to control acidity throughout the reaction. The maximum turbidity was generated when operating at pH = 2.0, and it slowly decreased with increasing to a value of pH = 3.0, at which the turbidity was the lowest. This result was a consequence of the presence of ferric ions in solution. At pH values greater than 3.5, the turbidity increased almost linearly until at pH = 5.0 reached its maximum intensity. In this range, ferrous ions may generate an additional contribution of radicals that promote the degradation of the phenol species that produce turbidity. Turbidity was enhanced at ratios R = 4.0 mol HO/mol CHO. This value corresponds to the stoichiometric ratio that leads to the production of turbidity-precursor species. Therefore, muconic acid would be a species that generate high turbidity in solution according to its isomerism. Also, the results revealed that the turbidity is not a parameter to which species contribute additively since interactions may occur among species that would enhance their individual contributions to it. Analyzing the oxidation of phenol degradation intermediates, the results showed that meta-substituted compounds (resorcinol) generate high turbidity in the wastewater. The presence of polar molecules, such as muconic acid, would provide the structural features that are necessary for resorcinol to act as a clip between two carboxylic groups, thus establishing directional hydrogen bonds that would generate an adduct in the 2:2 ratio. In addition, some similarity is observed between the turbidity and the presence of dihydroxybenzoquinone. This molecule has a structure that could establish hydrogen bond links with the carboxylic groups in 1:2 ratio. Such supramolecular structures would possess high molecular weight and robustness that would hinder the passage of light through the water, generating high turbidity.
本文研究了不同芬顿技术氧化水溶液中苯酚时产生的浊度变化。结果表明，如果芬顿反应在紫外光的促进下进行，水中生成的浊度将增加一倍。相反，使用超声波会导致浊度缓慢增加，最终达到传统芬顿处理的 8 倍以上。此外，浊度对 pH 值有很高的依赖性。因此，有必要在整个反应过程中控制酸度。当 pH 值为 2.0 时，浊度最大，当 pH 值增加到 3.0 时，浊度缓慢下降，达到最低值。这一结果是由于溶液中存在三价铁离子。在 pH 值大于 3.5 时，浊度几乎呈线性增加，直到 pH 值为 5.0 时达到最大强度。在这个范围内，二价铁离子可能会产生额外的自由基贡献，促进产生浊度的苯酚物种的降解。在 R=4.0 mol HO/mol CHO 的比例下，浊度增强。这个值对应于产生浊度前体物质的化学计量比。因此，根据其异构体，马来酸可能是一种在溶液中产生高浊度的物质。此外，研究结果表明，浊度不是各物质按比例贡献的参数，因为各物质之间可能会发生相互作用，从而增强它们对浊度的各自贡献。分析苯酚降解中间产物的氧化结果表明，间位取代化合物（间苯二酚）会在废水中产生高浊度。极性分子（如马来酸）的存在为间苯二酚提供了作为两个羧基之间的夹子的结构特征，从而建立了定向氢键，生成 2:2 比例的加合物。此外，浊度和二羟基苯醌的存在之间存在一些相似性。这种分子的结构可以与 1:2 比例的羧基形成氢键。这种超分子结构具有高分子量和坚固性，会阻碍光线通过水，从而产生高浊度。
