Search for and Development of Kinetically Excellent Organic Adsorbents Selective to Hazardous and Non-environment-friendly Anions

Arsenate species and nitrate are hazardous anions, which cause cancer and serious diseases. Phosphate species and nitrate are non-environment-friendly anions because they trigger eutrophication in lakes and rivers. Therefore, it is important to search for and develop kinetically excellent organic adsorbents selective to these anions. In this work, we found that crosskinked polyallylamine beads (PAA) selectively took up phosphate and arsenate species in the presence of chloride and sulfate. It was also clarified that a PAA packed column could take up phosphate species under fast feed flow rates of 300～2400 h⁻¹ in space velocity (SV). Referring to these findings, weak-base anion exchange fibers (FVA) containing polyvinylamine chains were prepared by means of alkaline hydrolysis of formamide moieties on polyvinylformamide grafted fibers, which were prepared by means of electron irradiation induced graft polymerization of vinylformamide onto polyolefin fibers (PPPE). The resulting FVA selectively took up arsenate species in the presence of chloride and sulfate, and an FVA packed column also took up arsenate species under fast feed flow rates of 100～1050 h⁻¹ in SV. Furthermore, kinetically excellent nitrate selective anion exchange fibers, FTAA and FTHA, were prepared by quaternization of polychloromethylstyrene grafted polyolefin fiber (PPPE-g-CMS) with triamylamine and trihexylamine, respectively; here, the precursor, PPPE-g-CMS, was prepared by means of electron irradiation induced graft polymerization of chloromethylstyrene onto PPPE. The resulting FTAA and FTHA were able to rapidly take up nitrate in column-mode even at the high feed flow rate of 500～3000 h⁻¹ in SV. Chloride, bicarbonate and sulfate up to 5 times the nitrate molarity did not interfere with the uptake of nitrate. Three kinds of anion exchangers described here were able to be used repeatedly through adsorption-elution-regeneration operations.<br>