Abstract:The co-smelting of waste printed circuit boards (WPCBs) and spent automotive catalysts (SACs) represents an innovative "waste-to-waste" strategy for resource recovery from hazardous wastes. Through metallurgical interactions, the copper in WPCBs acts as an efficient scavenger for enriching platinum group metals (PGMs), gold, and silver from SACs. Although this technology provides a sustainable treatment solution for these hazardous wastes through the synergistic recovery of metals, the transformation mechanisms of organic pollutants during the co-smelting process are not well understood. This study systematically investigated the transformation behavior of organic pollutants under the conditions for metal recovery: a smelting temperature of 1 400 ℃, a holding time of 4 hours, a scavenger proportion of 25%, and a basicity of 1.0. After the chemical composition and contents of SACs and WPCBs were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES), the liquid-phase and gas-phase products from the co-smelting of WPCBs and SACs were collected to prevent secondary pollution. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the compositional characteristics of organic substances during the co-smelting process. The weight loss characteristics and pyrolysis mechanisms of the materials were further analyzed. The Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Friedman methods were used to study the kinetic mechanisms of organic substance decomposition during co-smelting. The reaction kinetic model equations were applied to fit different conversion rate intervals to explore the decomposition mechanisms of organic substances. Additionally, an equivalent weighting method was employed to conduct a comprehensive toxicity assessment of the products in terms of toxicity, bioaccumulation, persistence, and secondary pollution risks. Analysis of organic substance composition revealed that the liquid-phase products mainly consisted of benzene derivatives (35.77%) and phenolic derivatives (37.26%), with no halogenated pollutants detected. The gas-phase products were primarily composed of small molecules such as H2, aromatics, CO, CH4, and CO2. Therefore, the co-smelting process resulted in the dehalogenation and molecular weight reduction of the products, reducing environmental risks. The metal components in the WPCBs-SACs co-smelting system catalyzed the decomposition of epoxy resins in WPCBs. In situ metals in the co-smelting system (e.g., Cu, Fe, and PGMs) significantly reduced the activation energy for organic substance decomposition, promoting the efficient cracking of complex pollutants. Within the temperature range of 600 − 800 ℃, the activation energy for organic substance decomposition decreased by 221.64 − 286.64 kJ/mol. The comprehensive toxicity assessment identified 4-phenylphenol, bisphenol A, phenol, naphthalene, and p-cresol as the organic pollutants with the highest environmental risks in the gas and liquid phases. Building on previous research on the co-smelting recovery of PGMs from WPCBs and SACs, this study comprehensively elucidated the transformation mechanisms of organic pollutants during the smelting process. Close-