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

Abstract

• Electro/Fe 2+ /persulfate can efficiently remove diesel from soil washing effluent. • The degradation of diesel was verified by EEM fluorescence spectroscopy. • The reactive radicals formed were identified by EPR technique. • The detoxification of soil washing effluent was evaluated by soil respiration. Electrochemical process coupling with Fe 2+ /persulfate (Fe 2+ /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, Fe 2+ dosage and PDS dosage on the abatement of diesel by electro/Fe 2+ /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/IrO 2 -Ta 2 O 5 and Ti/IrO 2 -RuO 2 ) anode, and lower initial pH favors diesel decay. There exist the optimal values of electricity intensity, Fe 2+ and PDS dosages for diesel elimination. Under the conditions of pH 0 3.0, 1.0 mM Fe 2+ , 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/Fe 2+ /PDS process. Soil respiration tests were carried out to evaluate the toxicity of the soil washing effluent before and after electro/Fe 2+ /PDS process. The reactive radicals formed were identified by electron paramagnetic resonance (EPR) technique. Briefly, coupling electrolysis with Fe 2+ /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.