Enhanced degradation of old landfill leachate in heterogeneous electro–Fenton catalyzed using Fe3O4 nano–particles encapsulated by metal organic frameworks

Abstract

Organic contaminants in old landfill leachate could cause large harm to human and environment without a proper treatment. In the present study, Fe3O4 nano–particles encapsulated by metal organic frameworks (Fe3O4NPs@MOF) was prepared, characterized and then applied to construct heterogeneous electro–Fenton (hetero–EF) process treating old landfill leachate. Increasing catalyst dosage, current density, plate distance and lower pH promoted the hetero–EF performance, COD removal efficiency could reach 66.67 ± 4.36% with catalyst dosage of 0.75 g/L, current density of 15 mA/cm2, plate distance of 1.5 cm and pH of 3. •OH played a more remarkable effect on organic contaminants degradation and contributed 76% of the COD removal. The MOF shell might protect Fe3O4 NPs in the core from reacting with acid solution, and mesoporous pore allowed e−, H+ and H2O2 to cross MOF shell and react with Fe3O4 NPs. Heterocycles, phenols and esters in old landfill leachate were dramatically degraded by hetero–EF, and the relative abundance of low molecular weight organics (<1 kDa) increased from 62.8% to 71.56% with BOD5/COD increasement from 0.025 to 0.39. It is suggested that heterogeneous electro–Fenton using Fe3O4NPs@MOF as catalyst would be an effective method to remove organic contaminants in old landfill leachate.