UVA and goethite activated persulfate oxidation of landfill leachate

In this study, UVA and goethite activated persulfate oxidation was applied to treat a synthetic (SLL) and a real landfill leachate (RLL) spiked with sulfamethoxazole (SMX). Initially, SLL was used to find the optimum landfill leachate (LL) treatment conditions in terms of total organic carbon (TOC) and SMX removal. The screening experiments were conducted using a two-level, four-factor Plackett-Burman design (PBD) to investigate the effects of UVA irradiation, time, concentrations of persulfate (PS) and goethite, on the removal of TOC and SMX. Dark experiments (PS/Goethite) yielded only a 2% TOC removal. Therefore, further experiments were conducted under UVA (365 nm) using a three-factor Box-Behnken design (BBD) in conjunction with response surface methodology (RSM). Analysis of variance (ANOVA) indicated high regression coefficients for the BBD-RSM model in the case of TOC removal (R² = 0.9755, adjusted R² = 0.9314 and predicted R² = 0.7956). In the case of SLL, RSM predicted an 84.4% TOC removal at the reaction time of 5.33 h, PS concentration of 477.4 mM, and goethite dosage of 755 mg/L under UVA. Experimentally, an 81.8% TOC removal and 100% removal of SMX were obtained under these conditions. Finally, the obtained optimum conditions were recalculated using RLL from the local municipal solid waste landfill, and 87% TOC and 100% SMX removals were obtained for PS concentration of 419.3 mM and goethite dosage of 663 mg/L after 4.68 h under UVA irradiation. Air stripping of RLL at pH 11 was complementarily applied to completely remove ammonia nitrogen after 3 hours. The results demonstrated the efficiency of the UVA/PS/Goethite system for the removal of organic matter from the LL for the first time.