Nanostructured micro particles as a low-cost and sustainable catalyst in the recycling of PET fiber waste by the glycolysis method

Abstract

Magnetic Mg-Al-O@Fe₃O₄ micro particles were synthesized by coating nanosized Mg-Al double oxides onto Fe₃O₄ micro particles. The formed hierarchical structure gave Mg-Al-O@Fe₃O₄ micro particles a high active surface area, which enabled these micro particles to work efficiently as a catalyst in the glycolysis of poly(ethylene terephthalate) (PET). The bis(hydroxyethyl) terephthalate (BHET) yield reached above 80 mol% in the presence of 0.5 wt% of Mg-Al-O@Fe₃O₄ micro catalyst in the reaction system within 90 min at 240 °C. After the reaction, Mg-Al-O@Fe₃O₄ micro catalyst was easily retrieved by a magnetic decantation and can be repetitively used for two times with a high catalytic efficiency. After that, the deactivated Mg-Al-O@Fe₃O₄ micro catalyst can be regenerated by heat treatment. The regenerated Mg-Al-O@Fe₃O₄ micro catalyst displays a comparable catalytic performance as that of the virgin catalyst. In addition, the Mg-Al double oxides and Fe₃O₄ micro particles are low-cost and environmentally benign. Therefore, the Mg-Al-O@Fe₃O₄ micro catalyst may contribute to an economically and environmentally improved large-scale circular recycling of PET fiber waste.

Keywords: Glycolysis; Nanostructured magnetic micro particles; PET fiber recycling; Poly(ethylene terephthalate) (PET); Sustainable catalyst.