(21b) Polymeric Chelating-Adsorbents and Their Use in the Adsorption of Arsenic Ions from Aqueous Solutions

In this work we present adsorption studies of the use of new arsenic adsorbents based on binding to chelating polymers. The method based on IMAC technology is unique among existing purification methods since it generates very small amounts of waste products in form of non-bulky concentrated arsenicals. The adsorbents can, in principle, be regenerated indefinitely and the small amounts of chemicals needed can be converted to common salt or other harmless chemicals. In this approach polyethyleimine-grafted-agar gels are used to bind metal ions of strong arsenic affinities. These immobilized metal ions in turn function as adsorption sites for arsenates and arsenites. According to this concept, arsenic in the form of arsenate or arsenite can be removed from the water samples by adsorption on polymer-immobilized metal ions. Arsenite in order to be adsorbed is first oxidized to arsenate and subsequently removed Arsenic is concentrated 104-106 times (or more) before being displaced from the solid phase. Collected effluent or supernatant is further concentrated. Arsenic can be subsequently eluted as concentrated soluble alkali arsenate and subsequently precipitated e.g., as insoluble copper arsenate and then further processed to a final stage for its safe disposal in compact form.