Synthesis and characterisation of diglycolic acid functionalised polyethylene terephthalate nanofibers for rare earth elements recovery

Abstract

The big advantage of functionalised nanofibers is their fast adsorption kinetics and considerable interest is currently devoted to developing nanofiber adsorbents for rapid sorption of metal ions. Polyethylene terephthalate nanofibers (PET-nf) functionalised with diglycolic anhydride ligand (PET-DGAnf) were prepared using a simple one-step reaction route. The surface characterisation of the synthesised PET-DGAnf adsorbents was performed using HR-SEM, XRD, TGA, BET, WCA and ATR-FTIR. The electrospinning optimisation was described by response surface methodology (RSM) and the collector distance was statistically significant to describe the production of nanofibers at optimum conditions. The average fiber diameter and the RSM analysis predicted values (113.6 nm) were in good agreement. Experiments in batch mode investigated factors such as the role of pH, solution concentration and contact time to evaluate their application for neodymium (Nd3+) and cerium (Ce3+) adsorption. The maximum PET-DGAnf adsorption capacity using the Langmuir model equation was 135.9 and 123.7 mg/g for Ce3+ and Nd3+ respectively and the equilibrium adsorption was attained within 5 min. The PET-DGAnf demonstrated good selectivity for Ce3+ in the presence of contending ions like Sr2+, Ni2+ and Co2+ ions after four successive adsorption and desorption assessments, and the desorption rate of Ce3+ and Nd3+ was maintained at more than 90% of their adsorption abilities. The PET-DGAnf nanofibers may provide a promising adsorbent for metal adsorption based on their fast binding kinetics and the high selectivity in recovering REE ions from aqueous solution.