RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Sorption of neptunium on naturally-occurring hematite (α-Fe₂O₃), magnetite (Fe₃O₄), goethite (α-FeOOH) and biotite (K(Mg,Fe)₃AlSi₃O₁₀(OH)₂) in 0.1 M? NaNO₃ solution was studied at 30°C for pHs between 4 and 11. The mass to volume ratio was 1 g/l.

The sorption-desorption reaction was reversible for all the minerals in the pH ranges studied. The dependence of neptunium sorption on pH differed between goethite and the other three minerals; goethite showed a strong sorption at pHs above 6 while the sorption on hematite, magnetite and biotite occurred at pHs above 9. Other oxyhydroxides, lepidocrocite (γ-FeOOH) and boehmite (γ-AlOOH), have a similar pH dependence of sorption to goethite. The sorption on hematite was similar to that on alumina (α-Al₂O₃).