The treatment of polyvinyl chloride (PVC) waste has received wide concern due to the high chlorine content of and the presence of toxic plasticizer such as diethylhexyl phthalate (DEHP). The chromium-containing wastewater is also an important environmental issue due to the toxic heavy metal Cr(VI). In this study, a synergistic treatment strategy for PVC waste and Cr(VI)-containing wastewater was developed by using subcritical water (SubCW) process. The strong reducing properties of polyol and polyene structures in situ formed from PVC dechlorination and subcritical water molecules synergistically promoted the significant detoxification/reduction of Cr(VI), and the Cr(VI) in turn had an enhancement effect on the dechlorination and conversion of PVC waste. The PVC dechlorination was significantly influenced by SubCW temperature, treatment time, solid-liquid ratio, and Cr(VI) concentration. Optimal conditions of 250 ℃, 60 min, a solid-liquid ratio of 1:15 g/mL, and a Cr(Ⅵ) concentration of 200 mg/L resulted in a PVC dechlorination efficiency of 95.42 % and a Cr(Ⅵ) removal ratio of 99.55 %. Cr(Ⅵ) exhibited an enhancement effect on PVC dechlorination between 200 ℃ and 300 ℃. In the SubCW system including Cr(Ⅵ), PVC dechlorination pathway involved direct HCl removal and hydroxyl substitution reactions. Hydrolysis of plasticizer DEHP at 250 ℃ resulted in the formation of phthalic acid crystals with a yield of 60.45 %. The oil product mainly included benzoic acid with a GC-MS relative peak area abundance of 94.41 % due to the decomposition and conversion of DEHP. The proposed subcritical chromium-containing wastewater (SCCW) process could be a promising technology for the synergistic treatment of the DEHP-rich PVC waste and chromium-containing wastewater.
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