INTRODUCTION OF A HIGH-DENSITY CHELATING GROUP INTO A POROUS MEMBRANE WITHOUT LOWERING THE FLUX

A method by which to introduce a high-density iminodiacetate (IDA) group into a polyethylene microfiltration membrane without lowering the water flux was developed by selecting the solvents for graft polymerization and subsequent chemical modification. Grafting of glycidyl methacrylate (GMA) onto the porous hollow fiber in a methanol solvent enhanced the swelling of the matrix and thus compensated for the decrease in pore volume. Subsequently, the dimethyl sulfoxide (DMSO)/water solvent provided a higher conversion of the produced epoxide group into the IDA group. The resulting IDA-group-containing hollow fiber had a sufficient cobalt-binding capacity and maintained the water flux at a feasible level. The flux of the chelating hollow fiber, whose degree of GMA grafting was 197%, was kept at about 70%, i.e., 2.0 m3/(m2 h) of that of the starting hollow fiber. The cobalt saturation capacity of the hollow fiber was 1.9 mol/kg. When a cobalt-containing solution permeated across the chelating hollow fiber through its pores, a sharp breakthrough curve of the cobalt ion was observed.