Impregnation of a neutral extractant to hydrophobic/hydrophilic groups introduced into the polymer chain grafted onto a porous membrane

Sawaki, Kenta*; Asai, Shiho; Watanabe, Kazuo; Sugo, Takanobu*; Saito, Kyoichi*

TOPO, tri-n-octylphosphine oxide, as a neutral extractant was impregnated to the hydrophobic group of the polymer chain grafted onto a porous hollow-fiber membrane for an efficient metal-ion collection. A diol group,i.e., adjacent hydroxyl group was introduced into poly-glycidyl methacrylate(GMA) chain grafted onto the porous hollow-fiber membrane via the epoxy-ring-opening reaction with water, followed by a reaction of the remaining epoxy group with octadecanethiol (CHSH) to form an octadecanethiol group. The diol group reduced the amount of TOPO coagulatedon the graft chain, whereas the interaction of the octadecanethiol group of the graft chain with the hydrophobic part of TOPO enabled the impregnation of TOPO to the graft chain. A 1 mmol-Bi/L bismuth chloride solution was forced to permeate through the pores of the TOPO-impregnated porous hollow-fiber membrane with a density of TOPO impregnated of 1.3 mol/kg of the GMA-grafted porous hollow-fiber membrane and the pure water flux of 0.7 m/h at 0.1 MPa and 298 K. The equilibrium binding capacity of the membrane for bismuth ions was 0.22 mol/kg of the TOPO-impregnated porous hollow-fiber membrane, which was equivalent to a binding ratio of bismuth ion to impregnated TOPO of 1.0.