Synthesis of new sustainable polyester‐type hydrogels from chemical recycled poly(ethylene terephthalate) products applied on the removal of indigo carmine dye

Abstract

Large amounts of plastic waste are daily generated, becoming a global issue that needs to be addressed. Thus, new recycling alternatives have been explored, such as the depolymerization of poly(ethylene terephthalate) waste (wPET). These reactions can lead to the formation of oligomers and monomers, which can then be employed in new synthetic processes. The aim of this work is to use the products of the chemical recycling of wPET on the synthesis of hydrogels and evaluate the capacity of these materials to adsorb dyes aiming a wastewater treatment. The depolymerizations were done through glycerolysis reactions catalyzed by zinc (II) acetate under microwave radiation. Afterwards, the obtained oil was crosslinked with citric acid (CA) under tin (II) chloride catalysis to obtain the hydrogels. The water uptake capacity of the hydrogels ranged from 310% to 1442%, depending on the CA content. When placed in an indigo carmine solution, the hydrogels showed high adsorption capacity, removing up to 97% of the dye. The kinetic study revealed a physicochemical mechanism for the removal process, corroborated by Temkin isotherms. These results indicate that the chemical recycling of PET via glycerolysis is a viable alternative for producing hydrogels, reducing plastic waste while creating new tools for wastewater treatment.