Fe-C micro-electrolysis-electrocoagulation based on BFDA in the pre-treatment of landfill leachate: Enhanced mechanism and electrode decay monitoring

Highlights: • Blast furnace dust ash is applied to treat landfill leachate. • Combination effect of Fe-C micro-electrolysis and electrocoagulation. • An optimal reversal time is determined based on the UTDR. In this research, a composite electrode for blast furnace dust ash (BFDA) was proposed in landfill leachate pre-treatment by Fe-C micro-electrolysis and electrocoagulation. To verify the effect of Fe-C micro-electrolysis, EC and Fe-C-EC systems were established respectively. When the voltage was 0.5 V–15 V and the electrode distance was 1 cm, the removal rates of COD and NH₄⁺-N in the landfill leachate by the composite system were 18.74%–43.6% and 5.48%–13.8%, respectively, which were 12.18%–5.3% and 3.03%–1.1% higher than the electrocoagulation system. By making a comparison between the two anode passivation layers' compositions, the mechanism of Fe-C micro-electrolysis was determined. The continuous supply of Fe²⁺ results in an increase on Fe₃O₄ and reduction in the harmfulness of the passivation layer. With the ultrasonic time-domain reflectometry(UTDR) analysis, the formation process of the anode passivation layer in the composite system was under monitoring, thus clarifying the best polarity reversal start time (PRST) and polarity reversal operational time (PROT) for the next polarity reversion measures. In this study, a new method for BFDA reclamation together with an efficient way for electrode passivation recovering were proposed.