Treatment of landfill leachate using magnetically attracted zero-valent iron powder electrode in an electric field

Abstract

This study combined electro-oxidation (EO) and electrocoagulation (EC) process (EO/EC) to treat landfill leachate by using RuO2-IrO2/Ti plate and microscale zero-valent iron powder composite anode. EO was achieved by direct oxidation and indirect oxidation on RuO2-IrO2/Ti plate, whereas EC was achieved using iron powder to lose electrons and produce coagulants in situ. The influences of variables including type of anode material, applied voltage, zero-valent iron dosage, interelectrode gap, and reaction temperature on EO/EC were evaluated. Results showed that at an applied voltage of 10 V, zero-valent iron dosage of 0.2 g, interelectrode gap of 1 cm, and non-temperature-controlled mode, the removal efficiencies were 72.5 % for total organic carbon (TOC), 98.5 % for ammonia, and 98.6 % for total phosphorus (TP). Some heavy metals and hardness were also removed. Further analysis indicated that the removal of TOC, ammonia, and TP followed pseudo-first order, pseudo-zero order, and pseudo-second order kinetic models, respectively. Other characteristics were examined by scanning electron microscopy–energy dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. Overall, our results showed that EO/EC can be used to efficiently remove organic matter, ammonia, TP, and heavy metals from landfill leachate.