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.