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

Abstract

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 •OH and SO4•-; however, SO4•- plays a major role while •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.