Decoupling the effects of additives and particle size on hydrothermal dechlorination kinetics of polyvinyl chloride
Hungwe D. Hosokawa S. Mosqueda A. Balanay M.P. Xu H. Ding L. Yamasaki Y.
December 2025Elsevier Ltd
Journal of Environmental Chemical Engineering
2025#13Issue 6
End-of-life polyvinyl chloride (PVC) poses major challenges for sustainable recycling because it releases corrosive HCl and toxic chlorinated organics during disposal or thermal processing. Hydrothermal dechlorination (HTD), which uses subcritical water to remove chlorine, offers a promising pathway to mitigate these environmental and technical risks. However, commercial PVC exhibits diverse particle sizes and complex formulations owing to additives such as stabilizers, fillers, plasticizers, and smoke suppressants that influence its behavior during HTD through interdependent pathways. We employed simplified formulations, HTD, and density functional theory (DFT) to decouple the effects of additives and particle size on PVC behavior. The filler CaCO₃ initially suppressed dechlorination by neutralizing HCl but subsequently enhanced porosity and late-stage diffusion. The plasticizer diisononyl phthalate (DINP) improved thermal equilibration and accelerated early kinetics but impeded late-stage reactivity due to diffusional resistance. ZnCl₂ derived from the stabilizer ZnSt₂ catalyzed the elimination pathway and enhanced overall dechlorination. Increasing particle size decreased transition dechlorination efficiency, indicating a shift toward thermal pathways. To capture these behaviors, a product-layer-dependent shrinking core model was applied, which accounts for the evolving product layer and its effect on diffusion and kinetic transitions, providing a more realistic description than the traditional SCM. Kinetic analysis of PVC pipe revealed activation energies of 232 ± 13.05 kJ/mol (slow substage) and 212 ± 32.85 kJ/mol (rapid substage), confirming that additives exert a cumulative inhibitory effect. These results provide an integrated description of how additives and particle size interact to control HTD kinetics, supporting the rational design of sustainable recycling strategies.
Hydrothermal dechlorination , Kinetic modelling , Polyvinyl chloride , Shrinking core model
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Research and Development Centre, Hosei University, 4342 Aihara, Machida, Tokyo, 194-0298, Japan
Department of Chemical Engineering and Technology, Mindanao State University-Iligan Institute of Technology, Iligan City, 9200, Philippines
Chemistry Department, Nazarbayev University, 53 Kabanbay Batyr Ave, Astana, 010000, Kazakhstan
Department of Transdisciplinary Science and Engineering, Institute of Science Tokyo, G5-8, 4259 Nagatsuta, Midori, Yokohama, 226-8502, Japan
Institute of Clean Coal Technology, East China University of Science and Technology, Shanghai, 200237, China
Department of Economics, Hosei University, 4342 Aihara, Machida, Tokyo, 194-0298, Japan
Research and Development Centre
Department of Chemical Engineering and Technology
Chemistry Department
Department of Transdisciplinary Science and Engineering
Institute of Clean Coal Technology
Department of Economics
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