Extraction of terephthalate from PET-derived sodium terephthalate model solution using a chitosan-based polymer inclusion membrane

Abstract

The rise of polyethene terephthalate (PET) has raised environmental concerns. Alkaline hydrolysis enables recovery of terephthalate (TP 2 − ), but efficient separation remains challenging. Thus, the separation method for TP 2 − requires further study. In this study, a chitosan-based polymer inclusion membrane (PIM) incorporating the protic ionic liquid (PIL) 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc]) and dioctyl phthalate (DOP) was developed for TP 2− extraction. The membrane was fabricated using a previously reported 3D-printed membrane caster and characterised using FTIR-ATR, SEM-EDX, XRD, TGA, BET, optical microscopy and water uptake capacity (WUC). The screened PIM achieved an extraction efficiency of (82.6 ± 0.15) % with a flux of 7.45 × 10 −6 mg cm −2 s −1 , a permeability coefficient of 1.49 × 10 −4 cm s −1 and retained over 65% efficiency after six cycles, while the recovery efficiency of TP 2- showed a gradual decrease. A small amount of DOP detected in both solutions may partially explain the decreased efficiency observed during repeated use. The extraction in Na 2 TP spiked water (tap water, lake water and seawater) demonstrates low extraction efficiency in seawater due to competing ions. Overall, the developed chitosan-based PIM with PIL carrier exhibits potential as a membrane system for extraction of TP 2− relevant to PET recycling applications.