Carbon Dioxide-Induced\nSeparations of Terephthalic\nAcid from Aqueous Disodium Terephthalate Solutions for Polyester Upcycling

Depolymerization of polyethylene terephthalate (PET)\nwith sodium\nhydroxide has been shown to be highly productive and selective toward\ndisodium terephthalate (Na<sub>2</sub>TPA). However, the traditional\nmethod to recover terephthalic acid (TPA) from aqueous solution uses\nstrong inorganic acids. As a potential sustainable alternative, gaseous\ncarbon dioxide (CO<sub>2</sub>) may be used as an acid switch for\nthe recovery of pure TPA and the capture of CO<sub>2</sub>. TPA yields\nup to 94% were verified experimentally. Low temperatures and higher\npressures, i.e., high CO<sub>2</sub> solubility, favor the recovery\nof terephthalic acid. A preliminary sustainability assessment indicates\nthat the choice of CO<sub>2</sub> over HCl may lead to fewer environmental\nimpacts.