Dechlorination of polyvinyl chloride by hydrothermal treatment with cupric ion

Hydrothermal treatment (HTT) is able to remove chlorine effectively from polyvinyl chloride (PVC), however, the reaction temperature is critical in practical application. Less energy-intensive hydrothermal dechlorination condition with cupric ion (Cu²⁺) has been proposed in this study. In particular, Cu²⁺ was applied in HTT of PVC at temperature ranging from 200 °C to 240 °C. It has been found that the introduction of Cu²⁺ distinctly accelerated PVC decomposition and dechlorination at 220 °C. When Cu²⁺ concentration was increased from 0.01 mol/L to 0.20 mol/L, the dechlorination efficiency was significantly improved from 15.46 %–67.89 %. Dramatic dechlorination occurred as residence time was longer than 15 min during HTT. Besides, both elimination and substitution dominated the HTT dechlorinaton. The facilitated dechlorination after the addition of Cu²⁺ was mainly due to the enhanced dispersion and formation of micropores in hydrochar. On the whole, HTT could be a promising pretreatment technology for copper-containing PVC in electronic wastes to prepared chlorine free hydrochar for combustion or pyrolysis applications, the optimal HTT condition would be 220 °C, 60 min with 0.1 mol/L Cu²⁺.