摘要：AbstractIn this work, the degradation of tannic acid (TA) by UV/H2O2process has been investigated. UV/H2O2oxidation experiments were performed by UV irradiation at 254 nm of TA aqueous solutions in a photo-reactor. Firstly, the effects of certain parameters including pH, H2O2content, and temperature on the decomposition of H2O2during UV/H2O2process were evaluated. Results obtained showed that UV-irradiation of 1 g H2O2 L−1aqueous solution achieved almost complete decomposition of H2O2(> 98%) at pH = 5 and 28 °C. H2O2decomposition follows pseudo-first-order kinetics with a rate constant of 0.0086 min−1under the optimal conditions. Secondly, the degradation of TA by UV/H2O2process was investigated. The effects of certain operating conditions including initial pH, temperature, H2O2concentration and initial total organic carbon (TOC) on the efficiency of degradation and mineralization of TA by UV/H2O2were evaluated. The results showed that UV/H2O2process achieved almost complete disappearance of the absorbance at 276 nm (> 96%) and high TOC removal (94%) from TA aqueous solutions containing 82 mg C L−1under pH = 9 using 6 g H2O2 L−1at 28 °C. The results confirmed that the degradation and mineralization of TA molecules in water occur via chemical oxidation with hydroxyl radicals produced by photo-decomposition of H2O2by UV light. Chromatography analysis revealed that the mechanism of TA degradation involves several steps including the formation of gallic acid and pyrogallol. These aromatic intermediates undergo further oxidative ring opening to form carboxylic acids (oxalic and maleic acids) that end up to be completely mineralized. The electrical energy requirement consumed under the optimal conditions was 7.9 kWh g−1TOC which is highly competitive with other advanced oxidation technologies such as ozonation and UV/O3processes. Based on these results, it can be concluded that UV/H2O2can be considered as a cost-effective method to treat wastewaters contaminated with natural organic matter.
