Synthesis of iminodi(methylphosphonic acid)-type chitosan resin and its adsorption behavior for trace metals

A chitosan-based resin possessing the iminodi(methylphosphonic acid) moiety (IDP-type chitosan resin) was synthesized by using cross-linked chitosan as a base material. The adsorption behavior of trace metal ions on the IDP-type chitosan resin was systematically investigated using a mini-column (1 ml of the resin) packed with the resin. The concentrations of metal ions in the effluents were measured by ICP-MS and ICP-AES. The resin could, adsorb four metals, such as In(III), Sn(II), Th(IV), and U(VI), by almost 100% over a wide pH range (1 similar to 7). Uranium (VI) and thorium could not be eluted with nitric acid and hydrochloric acid (1 similar to 6 M); other metal ions were easily and readily eluted with 1 M nitric acid. The IDP-type chitosan resin synthesized in this work can be applied to the separation of U(VI) and Th (IV) from other metal ions.