Structure of polyol–ligand-containing polymer brush on the porous membrane for antimony(III) binding

A polyol–ligand-containing porous hollow-fiber membrane for the recovery of antimony(III) was prepared by radiation-induced graft polymerization of an epoxy-group-containing vinyl monomer, glycidyl methacrylate (GMA), and by subsequent functionalization with N-methylglucamine (NMG) and 3-amino-1,2-propanediol (APD), that form a coordination complex with Sb(III). The structure of NMG–Sb(III) and APD–Sb(III) complexes in aqueous solution were determined by electron ionization-time-of-flight mass spectrometer (ESI-TOF-MS), and the binding ratio of NMG or APD to Sb(III) is 2:1. An antimony(III) oxide solution (10 mg Sb/l, pH 11.4) was forced to permeate through the submicron-diameter pores of the polyol–ligand-containing porous hollow-fiber membranes. The equilibrium binding capacity for antimony(III) to the NMG–ligand-containing porous hollow-fiber membrane, 96 g Sb/kg, was 10 times higher than that of the APD membrane. In a further study of the NMG membrane, the equilibrium binding ratios for antimony(III) to NMG groups were all approximately 0.5, illustrating that the NMG–Sb(III) complex on the fibers was in the ratio of 2:1. The results of computational structural analysis of the NMG–Sb(III) complex were in agreement with the experimental results of binding ratio. It was verified that an antimony(III) ion formed a coordination complex with two adjacent hydroxyl groups of two NMG moieties. The length of a functional group and the distance between functional groups on the polymer brush were significant factors to bind antimony(III) through the computational simulation.