Methods of Recycling

Managing Plastic Waste─Sorting, Recycling, Disposal, and Product Redesign

“…The solvent and antisolvent are then separated for reuse at the dissolution or precipitation stage of the process. Dissolution processes have been developed for recycling PS, , PVC, , nylon, PMMA, , PE/PP, ,, cotton/PET mixed fibers, PLA/PET mixtures, and multilayer films. , Some of these technologies are in commercial operation, e.g., APK’s dissolution of the multilayer film or the Re:newcell and OnceMore technologies for recovering cellulosic pulp from textiles . Solvay’s VinyLoop process for PS purification by dissolution has been run on a commercial scale for 16 years but, eventually, closed in 2018 because of the cost of renewing the permit for handling toxic phthalate plasticizers .…”

“…Most of them are prone to opening through hydrolysis, transesterification, or transamidation. Let us illustrate the approach for PET, PA, and PUR (Figure ), which are well advanced. ,, …”

“…Depolymerization requires harsh pyrolysis conditions and generally lead to a complex mixture of hydrocarbons, i.e., a general feedstock (lower right quadrant of in Figure ). The pyrolysis of polyolefins produces paraffinic/olefinic waxes under moderate temperature (450 °C) conditions, an aromatic product at more severe conditions, and olefin-rich gas and char at the highest temperature (∼700 °C). ,,− Such a hydrocarbon product can be processed into a synthetic fuel. But fractions of aliphatic products produced under mild conditions can also be used as chemical feedstock and cracked into lower olefins, generally after removing the heaviest product and hydrotreating the desired distillate fraction.…”

Back-to-monomer recycling of polycondensation polymers: opportunities for chemicals and enzymes

“…Currently, the recycling of plastics can be conducted using various methods: primary (mechanical or closed-loop), secondary (mechanical or open-loop), tertiary (chemical or feedstock), and quaternary (energy recovery or waste valorisation). 4,5 Among these methods, primary and secondary recycling are the most commonly applied, however, chemical recycling has also received significant attention in the past decade.…”

Valorisation of plastic waste via metal-catalysed depolymerisation

“…However, materials of lower quality and economic value can be obtained [51,52]. By contrast, the term "chemical recycling" (or feedstock recycling) refers to those processes involving an alteration of the polymeric chain due to breakage of chemical bonds [53,54]. This definition may be confusing since chain scission may actually occur using either physical (heat) or chemical agents.…”