Electro-Fenton approach in oxidative degradation of dimethyl phthalate - The treatment of aqueous leachate from landfills

Highlights: • The removal efficiency of 95.6% achieved for the treatment of landfill site leachate • The kinetic of the developed treatment model follows a first-order reaction. • EF-generated hydroxyl radicals were the principal components of the degradation process. Herein, the dimethyl phthalate (DMP) contamination, as an emerging pollutant, has been cost-effectively removed from landfill leachate through an advanced oxidation process, that is the electro-Fenton (EF) process. For this purpose, a quadratic polynomial model was developed via response surface methodology (RSM). Furthermore, the analysis of variance (ANOVA) was performed for evaluating the significance of the proposed assumptions. The actual removal rate of 99.1% was obtained with optimal values of 4 mg L⁻¹ of initial DMP concentration, 50 mM Na₂SO₄, 600 μL L⁻¹ H₂O₂, 8-minute electrolytic time, solution pH 3 and 6 mA cm⁻² current density for the process variables and was consistent with the expected 99.6% removal rate. Satisfactory correlation coefficients were obtained, and a non-significant value of 0.0618 for model mismatch confirmed that the proposed model is extremely important and can successfully predict the effectiveness of DMP removal. The kinetics of the process and the effect of the presence of some radical scavengers were studied to understand the exact mechanism of DMP degradation. Therefore, it was observed that the reaction of hydroxyl radicals with DMPs followed the first-order kinetics model. Moreover, it was established that the optimal ratio of H₂O₂/Fe²⁺ mole was 1.6 and the electricity consumption was 0.157 kWh m⁻³. The elaborated treatment model used to remove DMP from landfill leachate showed that DMP contamination was effectively removed with a 95.6% removal efficiency in the investigating process.