Selective Sorption of Technetium-99 on Modified Tin Dioxide

A novel tin dioxide shows excellent, almost quantitative, uptake properties for technetium-99. Its distribution coefficients (Kd values) for technetium are typically over 1 000 000 in solutions near neutral pH in one molar ionic competition, and uptake remains high over a broad pH region: pH 2-11. By comparison, normal organic resins yield Kd values less than 200. The variation in technetium uptake as a function of pH indicates two types of uptake mechanisms: acidic solutions (pH 2-4) show an uptake trend typical for weakly acidic cation exchange, and near neutral to basic solutions (pH 4-11) show an uptake trend typical for weakly basic anion exchange. Here, the possible uptake mechanisms by ion exchange process are discussed, and proposals are made for elucidating the exact sorption process. (authors)