A comprehensive review of separation technologies for waste plastics in urban mine

Plastic recycling has an obstacle from heterogeneous composition of plastic mixtures, which can be rectified by separation based on their different chemical and physical properties. Thus, it is essential to conduct a comprehensive review about separation technologies and developing trends of waste plastics. This study performed a bibliometric analysis of 2122 literatures through keywords searching based on Web of Science Core Collection database from 2000 to 2023. Then, we organized a review by selecting 144 literatures of plastic-containing mixtures and separation technologies excluding microplastics removal and plastics pyrolysis. This study summarized the liberation of waste plastics from metal, paper, pigment, plasticizer, oil contamination, and cross-linked silicone in Tetra Pak carton packaging, pharmaceutical blisters, electric cables, and printed circuit boards. Selective dissolution, hardness sorting, froth flotation, density separation, tribo-electrostatic treatment, and indirect sorting (based on spectroscopic technologies) were effective technologies to separate plastics from each other. The liberation is a premise to the subsequent separation. We stated characteristic factors of separation processes and evaluated the pros and cons of separation technologies. Separation routes of waste plastics could be divided in plastic-driven processes and commodity-driven processes. From commodity perspectives, separation after classification are endowed with robust operability (reproducibility) by avoiding uncontrollable interferences.