The photocatalytic oxidation of diclofenac, which is a non-steroidal anti-inflammatory medication, with TiO₂ illuminated with UV-A light under constant flow of pure oxygen has been investigated in our laboratories to evaluate the effect of initial reactant concentration on the reaction rate. Diclofenac adsorption experiments under dark conditions were also carried out to get information about the interaction between the organic molecule and the solid catalyst. Adsorption experiments at natural pH under dark conditions confirmed that the negatively charged diclofenac molecule is easily adsorbed on the positively charged surface of titania reaching equilibrium in less than 50 min. According to the Langmuir isotherm, the adsorption constant (K_eq) and the maximum uptake of diclofenac (q_m) on the surface of commercial TiO₂ are 21.1401 L mMol⁻¹DFC and 0.04013 mMoles DFC g⁻¹ TiO₂, respectively. Experimental results also indicate that the initial reaction rate of the photocatalytic degradation of diclofenac obeys the Langmuir–Hinshelwood–Hougen–Watson model with a kinetic constant K₁ = 0.08489 min⁻¹ and an adsorption parameter K₂ = 14.12821 mM⁻¹L. Combined chemical analysis of the reaction samples by HPLC, TOC, and UV–vis spectroscopy indicated that the diclofenac is efficiently mineralized by photocatalysis via hydroxylation of the aromatic rings to form 2-aminophenol, catechol, benzene-triol, 2,6-dichloroaniline, and fumaric acid, which in turn are completely mineralized to CO₂ and water.

中文翻译：

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双氯芬酸钠盐的光催化降解：吸附和反应动力学研究

在我们的实验室中，已经研究了双氯芬酸（一种非甾体类抗炎药）的光催化氧化，在恒定的纯氧流下用UV-A光照射TiO ₂来评估初始反应物浓度对反应速率的影响。 。还进行了在黑暗条件下的双氯芬酸吸附实验，以获取有关有机分子与固体催化剂之间相互作用的信息。在黑暗条件下于自然pH下进行的吸附实验证实，带负电荷的双氯芬酸分子很容易被吸附在二氧化钛带正电荷的表面上，并在不到50分钟的时间内达到平衡。根据Langmuir等温线，吸附常数（K _eq）和商品TiO ₂表面上双氯芬酸（q _m）的最大吸收量分别为21.1401 L mMol ^-1 DFC和0.04013 mMoles DFC g ^-1 TiO ₂。实验结果还表明，双氯芬酸的光催化降解的初始反应速率服从Langmuir-Hinshelwood-Hougen-Watson模型，其动力学常数K ₁  = 0.08489 min ^-1和吸附参数K ₂  = 14.12821 mM ^-1L.通过HPLC，TOC和UV-vis光谱对反应样品进行的化学联合分析表明，双氯芬酸通过光催化芳香环的羟基化反应而有效地矿化，形成2-氨基苯酚，邻苯二酚，苯三酚，2,6-二氯苯胺和富马酸，然后又被完全矿化为CO ₂和水。