The selective recycling of mixed plastic waste of polylactic acid and polyethylene terephthalate by control of process conditions

The glycolysis of postconsumer polyethylene terephthalate (PET) waste was evaluated with catalysts of zinc acetate, zinc stearate and zinc sulfate, showing that zinc acetate was the most soluble and effective. The chemical recycling by solvolysis of polylactic acid (PLA) and PET waste in either methanol or ethanol was investigated. Zinc acetate as a catalyst was found to be necessary to yield an effective depolymerization of waste PLA giving lactate esters, while with the same reaction conditions PET remains as an unconverted solid. This provides a strategy to selectively recycle mixed plastic waste by converting one plastic to a liquid and recovering the unreacted solid plastic by filtration.