The recycling and reuse of waste plastics mainly involve physical (mechanical) recycling and chemical recycling. Whether it is physical or chemical recycling, a certain degree of pretreatment, including impurity removal, cleaning, crushing, and sorting, is required for waste plastics. Among these steps, sorting waste plastics is relatively complex and challenging, representing a core step in the pretreatment process.

Waste plastics exhibit a complex composition, and for physical recycling, they need to be separated into components as single as possible before independent recycling based on the properties of different types of plastics. For chemical recycling, especially with the widely applied pyrolysis technology, it is necessary to pre-remove halogen-containing plastics from waste plastics to ensure product quality and reduce safety hazards in production equipment. This requirement emphasizes the need for thorough separation and sorting of waste plastics.

Traditional sorting methods primarily rely on manual sorting, which demands high qualifications from sorting personnel in terms of experience. Manual sorting tends to be less efficient, with higher labor costs. Although manual sorting cannot be entirely replaced at present, scientists have made continuous efforts to advance waste plastic sorting technologies. Methods such as magnetic separation, supercritical fluid sorting, and others have been developed.

This article provides a detailed introduction to widely researched waste plastic sorting technologies. It systematically reviews the research progress in density-based sorting, optical sorting, electrostatic sorting, and solvent-based sorting. The article compares and discusses the advantages and shortcomings of different sorting technologies and offers recommendations for future research and development. The aim is to provide support for the research and application of waste plastic sorting technologies.