Electrochemical oxidation of diethyl phthalate at two dimensional graphite sheet electrodes: optimization and analysis of degradation in water with HRMS

Abstract

Concentration of phthalates in the environment has been steadily increasing due to their high utilization rate and the inability of conventional wastewater and water treatment to remove them. Electrochemical oxidation at Boron doped diamond (BDD) was effective for phthalate removal but costly and unaffordable in many situations. Hence, we carried out the electrochemical oxidation of Diethyl Phthalate (DEP) at two dimensional graphite electrodes as a low cost alternative to oxidation at BDD electrodes. Optimization studies found that high concentrations of DEP (56–112 mg/L) can be effectively removed from water with acidic pH (pH 3), 60 mA/cm2 current density, 81 cm2 anode surface area and 10 mM sodium sulfate with 60 min treatment time. At 56 mg/L DEP concentration, COD and TOC removal were 92.5% and 70% respectively. FTIR studies were conducted to find out whether any adsorption or electrosorption had taken place at the electrode surface. High performance liquid chromatography-photo diode array (HPLC-PDA) analysis of 84 mg/L DEP solution treated at optimal conditions found 97.3% removal of DEP. High resolution mass spectrometry (HRMS) studies utilizing Ultra performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-ToF-MS) were conducted for finding the degradation byproducts and possible degradation pathway was proposed with the degradation mechanism.