Role of solvent in plasma-assisted peroxymonosulfate-hydrothermal process for plastic conversion

Hydrothermal processes are considered a promising strategy for the conversion of ever-growing plastic wastes. Plasma-assisted peroxymonosulfate-hydrothermal process has attracted increasing attention in enhancing the efficiency of hydrothermal conversion. However, the role of solvent in this process is unclear and rarely researched. Herein, the conversion process with different water-based solvents was investigated based on a plasma-assisted peroxymonosulfate-hydrothermal reaction. As the ratio of the solvent effective volume in the reactor increased from 20% to 53.3%, the conversion efficiency displayed an obvious decrease from 7.1% to 4.2%. The results indicated that the increased pressure caused by the solvent greatly reduced the surface reaction and forced the hydrophilic groups to shift back to the carbon chain, thereby reducing the reaction kinetics. A further increase in the solvent effective volume ratio could promote the conversion in the inner layer of the plastics to achieve an increase of the conversion efficiency. These findings can provide valuable guidance for the design of hydrothermal conversion for plastic wastes.