Degradation of refractory organic matter in MBR effluent from treating landfill leachate by the UV-nZVI-H2O2 system

In this study, nano zero-valent iron (nZVI) was used as the Fe2+ source in the Fenton reaction, and a UV-nZVI-H2O2 system was constructed to efficiently degrade and mineralize refractory organic matter in landfill leachate. The results showed that under the optimal conditions (initial pH = 3, UV = 14 W, nZVI = 0.5 g/L, and [H2O2] = 30 mM), the removal efficiencies of total organic carbon, absorbance at 254 nm, and color number were 61.38%, 83.89%, and 85.79%, respectively. Control experiments show that the UV-nZVI-H2O2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H2O2 system is related to a higher H2O2 utilization rate. The H2O2 residue in the UV-nZVI-H2O2 system was the lowest, and the effective utilization rate of H2O2 was as high as 98.80%. Alcohol quenching experiments and hydroxyl radical quantitative experiments showed that the dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO center dot and the yield of HO center dot was as high as 2007.80 mu M, which was much higher than that in other systems. The results of spectra analysis showed that the low molecular weight, high fluorescence frequency organic matter, and relatively stable aromatic organic matter were significantly degraded after treatment with the UV-nZVI-H2O2 system and the aromatic degree, humification degree, molecular weight, and molecular polymerization degree of refractory organic matter were also significantly decreased. The mechanism of the UV-nZVI-H2O2 reaction includes homogeneous and heterogeneous Fenton reactions and adsorption and precipitation of organic matter by iron-based colloids. This study can provide theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate.

Automated summary

In this study, a UV-nZVI-H2O2 system was used to efficiently degrade and mineralize refractory organic matter in landfill leachate using nano zero-valent iron (nZVI) as the Fe2+ source in the Fenton reaction. The optimum conditions were found to be initial pH = 3, UV = 14 W, nZVI = 0.5 g/L, and [H2O2] = 30 mM, resulting in removal efficiencies of 61.38% for total organic carbon, 83.89% for absorbance at 254 nm, and 85.79% for color number. The UV-nZVI-H2O2 system showed the highest removal and mineralization rates compared to other systems, attributed to its higher H2O2 utilization rate of 98.80%. The dominant reactive oxygen species in the UV-nZVI-H2O2 system were HO center dot, with a yield as high as 2007.80 mu M. This study provides theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate.