Effect of competing anions on pertechnetate adsorption by activated carbon

Activated carbon (AC) has a relatively high efficiency for retaining TcO4 (-) compared to other materials. AC is used on a vast scale in gas and water purification, metal extraction, medicine and many other applications. The TcO4 (-) adsorption mechanism on AC is not fully known, however there are assumptions of ion-exchange reaction between AC surface and TcO4 (-) anions. Adsorption and anion competitive investigation have shown that perchlorate anions have most influence on TcO4 (-) adsorption. Adsorption properties depend on standard absolute molar enthalpies of hydration. Anion competitiveness was investigated with five samples that were prepared in different ways (this was already published in previous article), we used several anions Cl-, Br-, ClO4 (-), CH3COO-, NO3 (-), HCOO- and SO4 (2-) at different concentrations. In general, the adsorption of TcO4 (-) is influenced mostly by ClO4 (-), what is explained by its similar structure with TcO4 (-); however the co-existence of Fe3+ cations in the AC structure decreases TcO4 (-) adsorption.