Kinetics and Reaction Pathways of Formaldehyde Degradation Using the UV‐Fenton Method
Kinetics and Reaction Pathways of Formaldehyde Degradation Using the UV‐Fenton Method
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DOI：
10.2175/106143010x12851009156204
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发表时间：
2011-05
影响因子：
3.1
通讯作者：
Xiangxuan Liu;Jiantao Liang;Xuanjun Wang
中科院分区：
文献类型：
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作者：
Xiangxuan Liu;Jiantao Liang;Xuanjun Wang
本研究的目的是研究甲醛（HCHO）作为中间产物在许多其他有机废水降解中的反应规则。在间歇式光化学反应器中研究了 UV-Fenton 法降解低浓度 HCHO 的工艺条件。结果表明，当原始HCHO浓度为30 mg/L时，在操作温度23℃、pH=3、H2O2用量68 mg/L、H2O2与Fe2+摩尔比（H2O2:Fe2+）为5的条件下，30分钟后91.89%的HCHO被去除。 HCHO在UV-Fenton体系中的降解基本上按照指数衰减。动力学研究结果表明，体系中HCHO、Fe2+、H2O2的反应级数分别为1.054、0.510、0.728，活化能为9.85 kJ/mol。 UV/H2O2、Fenton和UV-Fenton体系对HCHO降解的比较以及铁催化剂测试结果表明，UV-Fenton降解HCHO的机理是通过Fe2+和UV光的协同作用来催化H2O2的分解。 Fenton体系引入紫外线照射大大提高了HCHO的降解速率，这主要是由于加速了Fe2+/Fe3+循环的形成。通过气相色谱-质谱法和化学需氧量（COD）分析仪对反应产物进行分析。还通过气相色谱分析排出气体。根据这些结果，提出了 HCHO 在 UV-Fenton 系统中的反应路径。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。
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°C, pH = 3, an H2O2 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.