Enhanced degradation of refractory organics in concentrated landfill leachate by Fe0/H2O2 coupled with microwave irradiation

To study the treatment effect and mechanism of a combined microwave (MW)-Fe0/H2O2 Fenton-like process on concentrated landfill leachate, the effects of initial pH, Fe0 dosage, H2O2 dosage, MW power and reaction time on the removal of organic substances were investigated. The phase change of Fe0 before and after reaction and its catalytic mechanism were investigated using multiple analytical techniques. Results showed that the removal efficiencies of chemical oxygen demand, UV254 and color number were 58.70%, 85.69% and 88.30%, respectively, at initial pH of 2.0, Fe0 dosage of 0.5 g/L, H2O2 dosage of 20 mL/L, MW power of 400 W and reaction time of 14 min. Comparison of different Fenton-like processes indicated that the MW-Fe0/H2O2 Fenton-like process was the most efficient and significantly decreased the aromaticity degree, molecular weight and condensation degree of organic substances in the leachate. The fluorescence peak of concentrated leachate exhibited a blue-shift in the MW-Fe0/H2O2 process, further indicating that the condensation degree of humic substances declined and molecular weight remarkably decreased. The mechanism exhibited an advanced oxidation effect of a heterogeneous Fenton reaction between iron oxide and H2O2, as well as of adsorption and precipitation effects of iron-based colloids, on organic substances. Moreover, thermal and non-thermal effects of MW accelerated these reactions, achieving fast removal of organic pollutants in the concentrated landfill leachate. Overall, the results of this study showe that the MW-Fe0/H2O2 process is an effective and promising method to handle concentrated landfill leachate.