H₂O₂/UV-C oxidation of potential endocrine disrupting compounds: A case study with dimethyl phthalate

This paper discusses the feasibility of the ultraviolet radiation-hydrogen peroxide (H₂O₂/UV-C) process as an advanced oxidation process (AOP) in the treatment of endocrine disrupting compounds (EDC). Dimethyl phthalate (DMP) was chosen as the model compound owing to its classification as an EDC. Experiments have been conducted at various pH values (3.5, 6.0 and 9.0) and initial H₂O₂ concentrations (0-60 mM) in a batch reactor equipped with a low-pressure mercury UV-C lamp in order to evaluate the optimal operation conditions of the H₂O₂/UV-C process. The most effective pH value for the degradation of DMP by H₂O ₂/UV-C treatment was found as 6.0. DMP abatement increased with increasing H₂O₂ concentrations from 5 to 30 mM. Further increase in initial H₂O₂ concentration, however, reduced both the rate and extent of DMP removal as well as chemical oxygen demand (COD) and total organic carbon (TOC) removals. A simple kinetic model was proposed for DMP, COD and TOC abatements confirmed pseudo-first-order reaction. The electrical energy per order (EE/O) values for DMP oxidation and TOC mineralization were calculated as 3.3 and 19 kWh m^-3 order ^-1 respectively for the optimum treatment conditions (H ₂O_2,o = 30 mM, pH_o = 6.0, DMP_o= 100 mg L^-1). Inhibition of oxygen uptake rate by activated sludge (ISO 8192) was evaluated as a tool for assessing the acute toxicity of untreated and H₂O₂/UV-C treated DMP. According to the results obtained in this work, the use of the H₂O₂/UV-C process is recommended to achieve a complete DMP oxidation and high mineralization degree of aqueous solution of DMP.