Optimizing hydrothermal dechlorination of PVC in a SS-316 reactor: From chemistry knowledge to material considerations

Abstract

PVC remains one of the most challenging wastes for environmental activists and industrial recyclers because its decomposition products cause severe corrosion to equipment and our planet. The current study was designed to systematically investigate PVC dechlorination using the well-known Response Surface Methodology (RSM) to mature the process chemistry and assess the corrosion rate in the common SS-316 alloy. Undercover non-catalytic experiments, Cl removal, reactor wall corrosion rate, and H/C molar ratio of the products made the most argument to comprehend the chemistry and find the optimum operating condition. Based on data collected from different analytic techniques, like FESEM, SEM-EDX, TG, FT-IR, CHN, and AAS, it was found that water drove Cl removal through a combination of SN2 and Elimination pathways where the in-situ production of hydrochloric acid at high Severity Factor (SF) resulted in a desirably high dechlorination rate of 89.42%. However, significant metal leakage into the aqueous phase, e.g., 278.01 mg of Fe, in the Aqueous Phase (AP) necessitated the valorization of different approaches, including multistage dechlorination and application of various hetero and homogeneous catalysts, dealing with chloride and metal salts inside the reaction chamber. Among the solutions applied, the dual-stage and Ni-assisted dechlorination showed promising performances receptively with a corrosion rate as low as 0.034 g and the highest Cl removal efficiency of 96.18%.