Chemical recycling of various PET plastic waste under alkaline hydrolysis via the LSR method

Wastes plastics have caused serious environmental pollution due to their difficult degradation, therefore, there is an imperious demand for their recycling. It is known that waste polyethylene terephthalate (PET) can be degraded into sodium terephthalate (Na2TP) and ethylene glycol (EG) in alkaline aqueous solution, which could be utilized as the raw material for the manufacture of new PET. However, there are some obstacles in the recycling of waste plastics, such as low degradation efficiency, and complicated separation. Here, we report a novel method to degrade waste PET completely at 200 ℃ in 6 h, based on less solvent solid-state reaction (LSR) of PET and NaOH in the presence of a little amount of water and equivalent EG to terephthalate, the obtained product is sodium terephthalate (Na2TP) and EG. The kinetic of waste PET degradation fits to D2 or D1 model. Furthermore, into the reaction mixture is a stoichiometric concentrated H2SO4 added to obtain terephthalic acid (TPA) at room temperature. This work provides a strategy with practical application value for efficient and selective degradation of plastics, easy product separation, and recycling of raw materials, and also affords a promising scheme for the recycling economy of other ester-based waste polymers.