Xi'an Research Institute of High Technology, Xi'an, PR China.
Water Environ Res. 2011 May;83(5):418-26. doi: 10.2175/106143010x12851009156204.
This study was based on the purpose of investigating the reaction rules of formaldehyde (HCHO) as an intermediate product in the degradation of many other organic wastewaters. The process conditions of UV-Fenton method for the degradation of the low concentrations of HCHO were studied in a batch photochemical reactor. The results showed that, when the original HCHO concentration was 30 mg/L, at an operating temperature of 23 degrees C, pH = 3, an H202 dosage of 68 mg/L, and an H2O2-to-Fe2+ mole ratio (H2O2:Fe2+) of 5, 91.89% of the HCHO was removed after 30 minutes. The degradation of HCHO in the UV-Fenton system was basically in accordance with the exponential decay. The kinetic study results showed that the reaction orders of HCHO, Fe2+, and H2O2 in the system were 1.054, 0.510, and 0.728, respectively, and the activation energy (Ea) was 9.85 kJ/mol. The comparison of UV/H2O2, Fenton, and UV-Fenton systems for the degradation of HCHO, and the results of iron catalyst tests showed that the mechanism of UV-Fenton on the degradation of HCHO was through a synergistic effect of Fe2+ and UV light to catalyze the decomposition of H2O2. The introduction of UV irradiation to the Fenton system largely increased the degradation rate of HCHO, mainly as a result of the accelerating effect on the formation of the Fe2+/Fe3+ cycle. The reaction products were analyzed by gas chromatography-mass spectrometry and a chemical oxygen demand (COD) analyzer. The effluent gases also were analyzed by gas chromatography. Based on those results, the reaction pathways of HCHO in the UV-Fenton system were proposed. The qualitative and quantitative analysis of the reaction products and the COD showed that the main intermediate product of the reaction was formic acid, and the further oxidation of it was the rate-limiting step for the degradation of HCHO.
本研究旨在探讨甲醛（HCHO）作为许多其他有机废水降解中间产物的反应规律。在批式光化学反应器中研究了低浓度 HCHO 的 UV-Fenton 法降解的工艺条件。结果表明，当原始 HCHO 浓度为 30mg/L、操作温度为 23℃、pH=3、H2O2 用量为 68mg/L、H2O2 与 Fe2+摩尔比（H2O2:Fe2+）为 5 时，30min 后 HCHO 的去除率达到 91.89%。UV-Fenton 体系中 HCHO 的降解基本符合指数衰减规律。动力学研究结果表明，体系中 HCHO、Fe2+和 H2O2 的反应级数分别为 1.054、0.510 和 0.728，活化能（Ea）为 9.85kJ/mol。对比了 UV/H2O2、Fenton 和 UV-Fenton 体系对 HCHO 的降解效果，以及铁催化剂的试验结果表明，UV-Fenton 体系对 HCHO 的降解机制是通过 Fe2+和紫外光的协同作用催化 H2O2 的分解。向 Fenton 体系中引入紫外光大大提高了 HCHO 的降解速率，主要是由于加速了 Fe2+/Fe3+循环的形成。通过气相色谱-质谱联用仪和化学需氧量（COD）分析仪对反应产物进行了分析，并通过气相色谱仪对流出气体进行了分析。基于这些结果，提出了 UV-Fenton 体系中 HCHO 的反应途径。通过对反应产物和 COD 的定性和定量分析，表明反应的主要中间产物是甲酸，其进一步氧化是 HCHO 降解的限速步骤。
