Green recycling of waste PET plastic monomers by banana peel extract

Waste plastic (PET) and biomass (banana peels) are two pressing types of solid waste. In order to solve their global environmental problems, we calcined banana peel to produce alkaline banana peel extract (BPE) and successfully realized a one-pot method to achieve complete depolymerization of waste PET under mild reaction conditions (150 °C, 4 h). A series of characterization methods showed that the main active component of BPE for PET catalytic hydrolysis was K2CO3. The activation energy of BPE-promoted hydrolysis was determined to be 12.2 kJ/mol. DFT calculations demonstrated that the hydrolysis of PET over BPE followed the mechanism of random depolymerization. BPE showed high efficiency on the depolymerization of most commercial waste plastic PET bottles with almost 100% conversion. With simple treatment, the hydrolyzed product can be easily converted to be terephthalic acid (TPA) and frozen brine or additives for microbial culture. The collaborative high-value process of banana peel and waste PET not only reduced the use of fossil fuels in TPA production, but also provided a new idea for the synergetic treatment of biomass and plastics waste, which might be a good solution for waste valorization on tropical and subtropical islands.