Carbon Dioxide-Induced Separations of Terephthalic Acid from Aqueous Disodium Terephthalate Solutions for Polyester Upcycling

Depolymerization of polyethylene terephthalate (PET) with sodium hydroxide has been shown to be highly productive and selective toward disodium terephthalate (Na₂TPA). However, the traditional method to recover terephthalic acid (TPA) from aqueous solution uses strong inorganic acids. As a potential sustainable alternative, gaseous carbon dioxide (CO₂) may be used as an acid switch for the recovery of pure TPA and the capture of CO₂. TPA yields up to 94% were verified experimentally. Low temperatures and higher pressures, i.e., high CO₂ solubility, favor the recovery of terephthalic acid. A preliminary sustainability assessment indicates that the choice of CO₂ over HCl may lead to fewer environmental impacts.