Low-Temperature Modified-Immersion Molten ZnCl₂-Carbonization and Activation for Continuous Production of Mesoporous Carbon from Plastic Waste

Abstract

Plastic waste pollution has emerged as a critical global issue, threatening ecosystems, human health, and sustainable economic development. Molten salt carbonization and activation (MSCA) presents a promising pathway for converting plastic waste into valuable carbon materials. However, conventional MSCA approaches face challenges such as premature degradation of carbon sources before salt melting, undesirable side reactions that lower the specific surface area, and limited potential for industrial scalability. In this study, we introduce a prototype of a continuous MSCA system employing modified-immersion zinc chloride (ZnCl₂) molten salt system at a relatively low temperature of 350 °C to convert common plastic wastes including polypropylene (PP) bowls, polylactic acid (PLA) cups, and polyethylene terephthalate (PET) bottles into high-surface-area mesoporous carbon. The type of plastic waste and the ZnCl₂-to-PET mass ratio significantly influence the formation of mesoporous structures and the development of defect sites within the graphitic carbon matrix. Among all tested samples, MSW-PET-10 (derived from a 10:1 ZnCl₂-to-PET ratio) exhibited the highest specific surface area of 976 m²·g⁻¹ and a pore volume of 0.95 cm³·g⁻¹. The resulting mesoporous carbon derived from plastic waste demonstrates excellent electrochemical performance as a supercapacitor electrode material, highlighting its potential for energy storage applications and sustainable waste management.