Removal of diesel from soil washing effluent by electro-enhanced Fe2+ activated persulfate process

Electrochemical process coupling with Fe2+/persulfate (Fe2+/PDS) oxidation was applied to treat soil washing effluent containing diesel and surfactant Tween 80. The influence of several important parameters including anode material, initial pH, current density, Fe2+ dosage and PDS dosage on the abatement of diesel by electro/Fe2+/PDS process was investigated. The results show that the platinum anode (Ti/Pt) could achieve higher removal of diesel in comparison with the tantalum or ruthenium-based (Ti/IrO2-Ta2O5 and Ti/IrO2-RuO2) anode, and lower initial pH favors diesel decay. There exist the optimal values of electricity intensity, Fe2+ and PDS dosages for diesel elimination. Under the conditions of pH0 3.0, 1.0 mM Fe2+, 10 mM PDS and 27.8 mA/cm(2) current density, 88.6 % of diesel removal efficiency was obtained while almost 70.0 % of Tween 80 could be recovered. The excitation emission matrix (EEM) fluorescence spectroscopy further verified the degradation of diesel in the electro/Fe2+/PDS process. Soil respiration tests were carried out to evaluate the toxicity of the soil washing effluent before and after electro/Fe2+/PDS process. The reactive radicals formed were identified by electron paramagnetic resonance (EPR) technique. Briefly, coupling electrolysis with Fe2+/PDS oxidation is demonstrated to be an effective method for the abatement of diesel from soil washing effluent with the recovery of surfactant Tween 80.

Automated summary

Electrochemical process coupling with Fe2+/persulfate oxidation was applied to treat soil washing effluent containing diesel and surfactant Tween 80. The platinum anode (Ti/Pt) showed higher removal of diesel compared to tantalum or ruthenium-based anodes. Lower initial pH and optimal values of electricity intensity, Fe2+ and PDS dosages favored diesel decay. The process achieved 88.6% diesel removal efficiency and 70% Tween 80 recovery.