Removal of refractory organics and heavy metals in landfill leachate concentrate by peroxi-coagulation process

Landfill leachate is a complex effluent and it is difficult to deal with. Electrochemical methods have been considered as a promising alternative technology for treatment of landfill leachate with refractory organic contaminants and heavy metals. Peroxi-coagulation (PC) process with iron anode and modified graphite felt cathode was developed for efficient land-fill leachate concentrate treatment. Compared to electro-Fenton (EF) and electrocoagulation (EC) processes, the PC process was more cost-effective due to the combined action of center dot OH oxidation and iron hydroxides coagulation. A maximal TOC removal of 77.2% +/- 1.4% was obtained after 360 min at initial pH = 5.0 and current density of 10 mA/cm2. After the PC process, concentrations of all seven heavy metals in the final effluents were below the al-lowable emission limits given by the present regulatory standards. The method preference for heavy metal removal was PC > EC > EF. Based on the three-dimensional fluorescence spectroscopy coupled with regional integration analysis during the PC treatment, the florescence peaks of both humic acids and fulvic acids disappeared after treatment for 360 min. Decreasing trends were observed in the fluorescent regional standard volumes for aromatic protein I (31.4%), aromatic protein II (63.7%), fulvic acid-like (69.5%), soluble microbial by-product-like (75%) and humic acid-like regions (76.3%). The results indicate that comparing to the EF and EC process, the PC process provide a promising and more cost-effective alternative for the treatment of landfill leachate concentrate. (C) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

An efficient method based on the peroxi-coagulation (PC) process was developed for the treatment of landfill leachate concentrate. The PC process, which combines ·OH oxidation and iron hydroxide coagulation, showed higher treatment efficiency and lower cost compared to electro-Fenton (EF) and electrocoagulation (EC) processes. It achieved a high TOC removal rate and reduced the concentrations of all seven heavy metals in the final effluents below regulatory limits. Fluorescence analysis also demonstrated the effective removal of humic acids and fulvic acids by the PC process.