Metal ion imprinted polymers for effective radioactive waste segregation in nuclear industry

Selectivity in metal ion sorption can lead to major benefits in nuclear industry as it can lead to segregation of radioactive waste. This will in turn facilitate cost-effective and safe waste treatment procedures. While dealing with a large concentration of non-radioactive metal ion present along with very low (sub ppb) concentration of highly radioactive metal ions, any useful separation should enable complete segregation, meaning exclusion of one of the ions by the sorbent. Conventional ion-exchange resins do not offer such high selectivity. On the other hand, metal ion imprinting, a technique that involves designing polymeric sorbents with pre-determined selectivity, has the potential to yield sorbents with high orders of selectivity as required in the nuclear industry. We have earlier reported an imprinted polymer that could sorb ppb levels of cobaltous ions while completely rejecting ferrous ions present in large excess. The resin has the potential to significantly reduce the volume of radioactive waste generated due to cobaltous ions during nuclear reactor decontaminations. Using this technique, we have also succeeded in changing the selectivity of chitosan, a cheap biosorbent. Chitosan, which is generally selective towards ferrous ions, could be tuned to be selective towards cobaltous ions using metal ion imprinting, thus offering a scope for using bio-sorbents for selective sorption of radioactive metal ions.(author)