Functionalized Polyethylene Terephthalate Nanofiber Adsorbents for Prospective Metal Recovery from Spent Lithium-Ion Batteries

Abstract

The lack of economically viable and environmentally friendly recycling processes to recover valuable metals from spent lithium-ion batteries (LIBs) has resulted in an environmental pollution and a high risk of metal resource shortage. Among various approaches, adsorption using electrospun nanofiber adsorbents has attracted research interest due to several distinctive properties. This study synthesized electrospun polyethylene terephthalate (PET) nanofiber adsorbent which was functionalized with Di-2-ethylhexyl phosphoric acid (DEHPA) to recover Ni, Co, or Mn metal ions. The pristine and modified electrospun nanofibers were characterized using Fourier Transform Infrared spectroscopy (FTIR)-Attenuated Total Reflection (ATR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetric Analysis (TGA), and X-ray Diffraction (XRD). The adsorption kinetics and capacity of the modified PET-DEHPA nanofibers were obtained at optimum pH 4; 60 min of contact time and 100 mg/L initial metal concentration. The adsorption capacity of PET-DEHPA nanofibers for Ni, Co and Mn metal ions was 80 mg/g, 98 mg/g, and 118 mg/g, respectively. The selectivity of Mn over Ni and Co metal ions was also examined at pH 4 and showed that the recovery efficiencies were 5%; 11% and 58% for Ni, Co and Mn, respectively. Thus, indicating that the modified PET-DEHPA nanofiber was selective for Mn ions. The desorption and regeneration were also studied in solutions of nitric acid and Ni, Co and Mn ions, and results showed that PET-DEHPA nanofiber was able to withstand over 5 cycles, highlighting its potential in economic viability and sustainability. Overall, this study presents a new and promising approach for recycling Mn ions from solutions of spent LIBs.