Treatment of stabilized landfill leachate using pyrite-activated persulfate oxidation process

Landfill leachate is a major hazard for the surrounding ambience as it detrimentally contaminates the soil and groundwater. In the present study, sulfate radical based advanced oxidation process (SR-AOP) was adopted for the treatment of stabilized/mature landfill leachate (SLL) using pyrite (FeS2) as a heterogeneous catalyst. The FeS2 catalyst was characterized using XRD, FT-IR, SEM and EDX spectroscopy techniques to evaluate its structural, functional groups, morphological features, and chemical composition, respectively. The effect of various operating parameters on SR-AOP such as initial pH, FeS2 dosage, Na2S2O8 concentration, and temperature on COD and TOC removal was also studied. The FeS2 (1000 mg/L), Na2S2O8 (1000 mg/L) concentrations at pH 8.8 were found optimal, and COD and TOC removals were found as 78.5% and 74.2%, respectively. After the treatment of SR-AOP, BOD5,20/COD ratio of landfill leachate was improved from 0.023 to 0.41. Scavenging tests revealed that the primary oxidative species in SR-AOP are center dot OH and SO4 center dot-; however, SO4 center dot- plays a major role while center dot OH is also involved in the process. Intriguingly, no significant change in the catalytic efficiency and characteristic nature of FeS2 was observed even after four sequential treatments of the same FeS2 catalyst.

Automated summary

In this study, sulfate radical based advanced oxidation process (SR-AOP) using pyrite (FeS2) as a heterogeneous catalyst was used to treat stabilized/mature landfill leachate (SLL). Optimal conditions for COD and TOC removal were found to be 1000 mg/L FeS2, 1000 mg/L Na2S2O8 at pH 8.8, with removal rates of 78.5% and 74.2%, respectively. The primary oxidative species in the SR-AOP were found to be •OH and SO4•-, with SO4•- playing a major role. Interestingly, no significant change in the catalytic efficiency and characteristic nature of FeS2 was observed even after four sequential treatments.