Anion exchange fibres derived from chloromethylstyrene grafted POLYOLEIN FIBRES for rapid column-mode removal of nitrate in water

Go, Yasuhiro*; Yoshida, Hiromi*; Jo, Akinori*; Tamada, Masao; Katakai, Akio

Proceedings of 2008 Conference on Ion Exchange Technology (IEX 2008), p.353 - 361, 2008/07

Although granular anion exchange resins are useful for column-mode removal of nitrate in water, sizes of granular resins used in industrial scale columns are ca. 0.5 mm to reduce pressure loss in column operations. Since large granular resins bring down adsorption kinetics, it is difficult to supply water polluted with nitrate to granular resin packed columns at extremely high flow rates more than 1000 h in space velocity (SV). In this work, we have prepared an anion exchange fiber named FBDA, which rapidly takes up nitrate in column-mode even at the flow rate of feed of 3000 h in SV. FBDA was prepared by electron beam irradiation induced liquid phase graft polymerization of chloromethylstyrene (CMS) onto polyethylene-coated polypropylene fiber (PPPE; 1.5 denier) and the subsequent quaternization of the CMS-grafted fiber with n-butyldimethylamine (BDA). The resulting BDA-fixed fiber (FBDA) has anion exchange capacity of 2.2 meq/g. To the column (i.d. 1.3 cm) containing 2.0 mL wet FBDA, 1 mM nitrate feeding solutions in the absence and presence of a competing anion was fed to the column at given flow rates. In the absence of a competing anion, shapes of breakthrough profiles of nitrate are independent of the flow rates from 1000 to 3000 h in SV, giving the constant breakthrough capacity for nitrate as high as 1.1 mmol/g. Effect of chloride and sulfate was tested at the flow rate of 1000 h. In the presence of 1 mM and 5 mM chloride, breakthrough capacities for nitrate were reduced to 0.83 and 0.48 mmol/g, respectively. However, equimolar sulfate reduced the breakthrough capacity down to 0.43 mmol/g. Thus, the presented FBDA is useful for rapid purification of water contaminated with low concentration levels of nitrate, so long as concentrations of chloride and sulfate are nearly equal orders as those in most river waters. Almost the same results were also obtained in case of the triethylamine-fixed fiber named FTEA.