Treatment of refractory organics in biologically treated landfill leachate by a zero valent iron enhanced Peroxone process: Degradation efficiency and mechanism study

Abstract

A zero valent iron (ZVI) enhanced Peroxone process (ZVI/Peroxone) was used to treat biologically treated landfill leachate (BTL). The treatment efficiency of the ZVI/Peroxone process was compared to single (ZVI, O3 and H2O2) and dual (ZVI/H2O2, Fe0/O3 and Peroxone) processes. The results showed that ZVI can greatly enhance the treatment capability of the Peroxone process, and the color number (CN), absorbance at 254 nm (UV254), and total organic carbon (TOC) removal efficiencies were 98.82, 84.30 and 66.38%, respectively. In the ZVI/Peroxone process, higher O3 and ZVI dosages improved organics removal, and H2O2 could promote organics removal within a certain dosage range. However, too much H2O2 decreased treatment efficiency. The best treatment performance by the ZVI/Peroxone process was obtained under acidic conditions. The three-dimensional excitation and emission matrix analysis showed that BTL mainly contained two fluorescent substances, which were fulvic-like substances in the ultraviolet region (Ex/Em = 235–255 nm/410–450 nm) and fulvic-like substances in the visible light region (Ex/Em = 310–360 nm/370–450 nm). Fluorescent substances could be substantially degraded by the ZVI/Peroxone process during the early stages of the reaction. An analysis of ZVI morphology and element valency changes showed that the micro Fe0 particles used in this study remained highly reactive during the process. The ZVI enhanced the homogenous Fenton, heterogeneous Fenton, and coagulation-flocculation effects during the Peroxone process.