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The sustainable resource management of end-of-life vehicles (ELVs) towards a circular economy has become an issue of concern around the world. An understanding of recycling and the quantitative flow of ELVs is important because of their potential for resource recovery as well as the environmental impacts posed by their toxic chemicals upon disposal. In this paper, the generation and recycling system of ELVs in South Korea has been discussed based on a review of the available statistics and literature and site visits to ELV-recycling facilities. A material-flow analysis (MFA) for ELVs was performed to elucidate the resource recovery from recycling, while the substance flow of polybrominated diphenyl ethers (PBDEs) in automobile shredded residues (ASR) was also determined for proper management. Approximately one million tons of ELVs in 2020 were processed by dismantling and shredding treatment for the recovery of reusable and recyclable materials (803,000 tons), resulting in 78,300 tons of ASR. Approximately 97 tons of PBDEs as flame retardants were generated mainly from ASR in 2020 and processed via combustion, either with energy recovery (59.8%) or without heat recovery (39.2%). The monitoring of brominated dioxins and furans by unintentional release during the incineration processes of ASR is required in order to prevent the dispersion of the chemicals in the environment.

This study aimed to synthesize dispersed and reactive nanoscale zero-valent iron (nZVI) with poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA), nontoxic and biodegradable stabilizer. The nZVI used for the experiments was prepared by reduction of ferric solution in the presence of PVP/VA with specific weight ratios to iron contents. Colloidal stability was investigated based on the rate of sedimentation, hydrodynamic radius and zeta potential measurement. The characteristic time, which demonstrated dispersivity of particles resisting aggregation, increased from 21.2 min (bare nZVI) to 97.8 min with increasing amount of PVP/VA (the ratios of 2). For the most stable nZVI coated by PVP/VA, its reactivity was examined by nitrate reduction in a closed batch system. The pseudo-first-order kinetic rate constants for the nitrate reduction by the nanoparticles with PVP/VA ratios of 0 and 2 were 0.1633 and 0.1395 min-1 respectively. A nitrogen mass balance, established by quantitative analysis of aqueous nitrogen species, showed that the addition of PVP/VA to nZVI can change the reduction capacity of the nanoparticles.

Photocatalytic degradation of methyl parathion was done using a circulating TiO2/UV and TiO2/solar reactor. Indoor experimental results showed that, under the photocatalysis conditions, parathion was more effectively degraded than under the photolysis and TiO2 only conditions. Parathion (38 microM) was completely degraded under photocatalysis within 90 min, and more than 80% TOC decrease after 150 minutes. The main ionic byproducts during the photocatalysis were measured, and almost complete nitrogen recovery was achieved as mainly NO3- NO2-, and NH4+, and 80% of sulfur as recovered as SO4(2)-. Organic intermediates such as nitrophenol and methyl paraoxon were also identified during the photocatalysis of parathion, and these were further degraded after 90 minutes. Microtox bioassay using Vibrio fischeri was used in evaluating the toxicity of solutions treated by photocatalysis and photolysis of parathion. The results showed that the acute toxicity expressed as EC50 almost reduced after 90 min under the photocatalysis condition whereas only 40% reduction of toxicity as EC50 was achieved in photolysis condition. The outdoor results using a TiO2/solar system were similar to the TiO2 indoor system, indicating the possibility of applying TiO2/solar system for the treatment of parathion-contaminated water.