Treatment of mature landfill leachate using chemical and electrical Fenton with novel Fe-loaded GAC heterogeneous catalysts

Abstract

In this study, heterogeneous Fenton catalysts were prepared by loading iron oxides on granular activated carbon (GAC), with which as heterogeneous Fenton catalysts, mature landfill leachate (MLL) was treated by chemical and electrical Fenton method. For chemical Fenton treatment of MIL, the optimum conditions were optimised by orthogonal experiments and the removal of COD, NH3-N and colour reached 93.7 %, 65.5 % and 84 % respectively for static experiments, whereas the heterogeneous Fenton fluidized bed reactor removed >90 % of COD in all the 12 h of continuous operation. For electrical Fenton treatment of MIL, the removal rates of COD, colour, NH3-N, and TN were 97.4 %, 99 %, 100 %, and 94.2 %, respectively under the optimum treatment conditions of pH = 5, the GAC/α-FeOOH catalyst dosage of 13.3 g L−1, and the applied voltage of 8 V with the energy consumption of only 0.23 kWh (g COD)−1. Upon characterization, humic acid, fulvic acid and xanthohumic acid in the MLL were completely degraded and the complex macromolecules such as polycyclic aromatic hydrocarbons and heterocyclic rings were reduced and converted to simple small molecules such as alkanes. The quenching experiments verified that the ·OH produced in the heterogeneous electrical Fenton system plays an important role in the degradation of MLL, while the removal of NH3-N also relies on indirect oxidation with the active chlorine produced by the electrochemical system. GAC-based heterogeneous Fenton catalysts with high catalytic capacity and easy recycling have good application prospects in treating MLL.