Functionalized and reusable polyethylene fibres for Au(iii) extraction from aqueous solution with high adsorption capacity and selectivity

Abstract

A new chelating polyethylene fibre was synthesised by the radiation-induced graft copolymerisation of glycidyl methacrylate (GMA) onto ultrahigh-molecular-weight polyethylene (UHMWPE) fibres and subsequent ring-opening reaction with 4-amino-1,2,4-triazole. The chemical structure and surface morphology of the modified fibres were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The adsorption behaviour of the fibrous sorbent for Au(III) was investigated in terms of aqueous-solution pH, contact time, initial metal concentration and competition of coexisting metal ions. Resultant fibres exhibited much higher affinity and selectivity for Au³⁺ ions than all other metal ions (Mg²⁺, Fe³⁺, Cu²⁺, Ca²⁺, Ni²⁺ and Cr⁶⁺). The affinity coefficient obtained was as high as 97.5–99.9%. The maximum adsorption amount for Au³⁺ was 429.4 mg g⁻¹. The adsorption of Au(III) followed the pseudo-second-order kinetics model controlled by chemical adsorption. The equilibrium data fitted the Langmuir isotherm model well. In particular, this fibrous adsorbent can be regenerated by treatment in 0.5 M thiourea and 0.5 M H₂SO₄ solution. The high adsorption capacity can be maintained after at least five adsorption–desorption cycles.