Degradation Of Typical Emerging Contaminants By Advanced Oxidation Processes Based On Electrochemical Generation Of H₂O₂

UV photolysis combined with electrochemical induced advanced oxidation technologies have more excellent performance for the degradation of refractory organic pollutants,this paper mainly carried out the researches on mechanism and operation parameters optimizations of two novel photo-electrochemical catalytic advanced oxidation processes.Mainly includes:evaluated the elimination of Desethyl-atrazine?DEA?by an electrochemical-induced UV/H₂O₂ process which was developed based on electro-generation of hydrogen peroxone?H₂O₂?in-situ?referred to E-UV/H₂O₂?;Whereafter,compared the degradation and mineralization of 1,4-dioxane by the Photo-electroperoxone process?PEP?which combines conventional ozonation,ultraviolet?UV?,and electrochemical H₂O₂ with the single processes and their binary combinations,as well as ozonation?UV photolysis?Electrolysis,UV/O₃ and Electro-peroxone.On this basis,the effects of main operational parameters,e.g.,electrolytes,electrodes,and pH were systematically evaluated so as to optimize the sewage treatment capacity of PEP.H₂O₂ is the precursor of·OH,for E-UV/H₂O₂ and PEP peocesses,proper selection of cathodes that can effectively produce H₂O₂ in-situ is crucial to the mineralization of pollutants.Carbon polytetrafluoroethylene?Carbon-PTFE?gas diffusion electrode showed optimum performance on production of H₂O₂ in situ via the electrochemical reduction of O₂ in the 12 tested carbonaceous materials,the current efficiency was maintained at more than 80%.Results indicated that the electrode was the best choice for cathode materials during E-UV/H₂O₂ and PEP system.The E-UV/H₂O₂ process showed comparable performance between secondary effluents and synthetic solutions for the degradation of DEA.The technology significantly increased the rates of DEA degradation compared to UV.It is feasible to utilize anodically-induced O₂ as the oxygen source for cathodic H₂O₂ generation to degrade pollutant in the E-UV/H₂O₂ process,the technology is cost and energy-efficient.Attributed to the multiple ways of·OH generation in the PEP process,the PEP process achieved much stronger synergy for 200 mg/L 1,4-dioxane degradation than UV?Ozonation?UV/O₃ and Electro-peroxone process,after 45 min of treatment,the UV/O₃,EP,and PEP processes removed⁷0%,37%,and 98%TOC with a specific energy consumption?SEC?of⁰.38,0.22,and 0.30 kWh/g TOC,respectively,PEP process can improve both the kinetics and energy efficiency for 1,4-dioxane mineralization compared to the UV/O₃ and EP.Increasing ozone dose,applied current,and solution pH increased generally the rate of TOC removal during the PEP process.When sodium chloride?NaCl?was used as the supporting electrolyte,chlorine?Cl₂,formed from anodic oxidation of Cl^–?and hypochlorous acid/hypochlorite?HClO/ClO^–?would react with H₂O₂,thus diminishing its synergistic effects with O₃ and UV for pollutant degradation,especially when using anodes?ruthenium and iridium oxide coated titanium,RuO₂-IrO₂/Ti?with higher chlorine evolution activity.So that,PEP process works more efficiently with Na₂SO₄ electrolytes than with NaCl.These results indicate that careful optimizations of the operational parameters are critical to maximize the purification capacity of the PEP process for wastewater treatment.These results indicate that the E-UV/H₂O₂ and PEP process may provide a promising alternative for the current water and wastewater treatment.