Sorption of uranyl by humic acids

Abstract

Sorption of (UO 2) 2+ from a UO 2Cl 2 solution was carried out on a substrate of humic acids complexes extracted from the peat bog of Mirochov (Bohemia). The ash-free substrate of the acids contained 53.44% C, 5.37% H, 39.68% O and 1.51% N. The ash content was 0.4%. The total acidity was 7.61 mequiv./g, the content of carboxyl 4.20 mequiv./g and that of phenolic hydroxyls 3.35 mequiv./g. The sorption capacity of (UO 2) 2+ by humic acids at 20.00 ± 0.03°C depends on the acidity of the environment, and decreases with decreasing pH value. The accumulation of U on humic acids takes place mostly by an exchange of hydrogen ions for uranyl cations. The sorption rate is independent of the acidity of the environment. Within the concentration range from 10 −5 to 2·10 −3 mol (UO 2) 2+/l, the uranyl sorption obeys Langmuir's equation.