Harnessing deep eutectic solvents for upcycling waste membranes into high-performance adsorbents and energy storage materials

Polymer membranes waste management across the globe is a great concern due to the lack of advancement in upcycling methods. Herein, waste polysulfone (W-PSF) membranes, an emerging environment threat, have been converted to multi-functional carbon materials via green method using choline chloride:FeCl₃ (CC:FeCl₃) based deep eutectic solvent (DES) systems through solvothermal reaction followed by pyrolysis at 900 °C. The optimized material (Fe-WPSF-01) showed excellent adsorption capacity towards Malachite green (MG), Congo red (CR), Amoxicillin (Amo), and Bisphenol-A (BPA) with 515, 407, 216, and 322 mg/g of adsorption capacity, as calculated from the well-fitted Langmuir isotherm. Further, an easy-to-use adsorptive membrane filtration method was established to investigate the robustness of Fe-WPSF-01 in removing the above pollutants in continuous flow method. The resultant flux rate was 700–815 L.m⁻².h⁻¹ with rejection rates of 99, 98, 92, & 98 % for MG, CR, Amo, & BPA, respectively. Besides, the material showed recyclability for up to 10 cycles with 92.1 & 81.2 % of rejection rates for MG and Amo. After the potential usage of carbon material in adsorption studies, secondary materials were again pyrolyzed to use as an electrode in supercapacitors with a specific capacitance of 215 F/g at a current density of 0.1 A/g. Electrode showed capacity retention of 97.51 % even after about 20,000 cycles at an increased current density of about 5 A/g. Thus, a potential sustainable approach of upcycling the W-PSF membranes for energy and environmental applications are well-presented in this work.