Sorption and desorption of uranium(VI) on silica: experimental and modeling studies

Abstract

Uranium(VI) / Sorption / Desorption / SilicaSummary. Sorption of U(VI) on silica was investigated as functions of contact time, pH, ionic strength, solid-toliquid ratio (m/V ) and U(VI) concentration by using a batch experimental method. It was found that sorption kinetics is relatively rapid and 1 h is sufficient to reach sorption steady state. The sorption of U(VI) increases from about 0 to 100% with pH over the range of 2.8 to 5.8. Sorption isotherms were collected at pH 4.3 and three ionic strengths (0.01, 0.1 and 0.5 mol/L NaCl). It was found that the sorption of U(VI) increases with decreasing ionic strength at pH 4.3 and relatively low U(VI) concentrations. The sorption of U(VI) with variable m/V at pH 4.2 and initial U(VI) concentration of 1.03 × 10 −4 mol/L indicated that the U(VI) distribution coefficient increases slightly with the increase of m/V over the range of 1 to 100 g/L. Desorption was performed by dilution of aqueous U(VI) concentration for desorption isotherms and by pH adjustment of the suspension for pH desorption edges. It was found that sorption/desorption is reversible with respect to aqueous pH values, whereas a hysteresis was found for desorption isotherms. All equilibrium data were fitted with a surface complexation model. A mononuclear inner-sphere surface complex ≡SOUO 2 + and a polynuclear surface complex ≡SO(UO 2 ) 3 (OH) 5 were used to quantitatively interpret sorption of U(VI) on silica.

Adsorption and desorption of uranium (VI) in aerated zone soil

“…As shown in Fig. 6, uranium (VI) sorption when the ionic strength varied from 0.01 to 0.1 M. Inner-sphere and outersphere mechanisms have been considered to explain the effect of ionic strength on sorption (Guo et al, 2009;Shuibo et al, 2009). Outer-sphere surface complexes are formed when sorption decreases with increasing ionic strength, whereas inner-sphere surface complexes operate when the sorption is insensitive to ionic strength.…”

Interactions between Silicon Oxide Nanoparticles (SONPs) and U(VI) Contaminations: Effects of pH, Temperature and Natural Organic Matters

“…Natural and synthetic silicon oxide exists extensively in environment and is applied in efficacious removal of heavy metals/radionuclides for several years [ 17 – 19 ]. Generally, the transportation of contaminations in environment depends on the existed contaminations types and the reversibility between contaminations [ 20 ].…”

Sorption and Speciation of Uranium on Silica Colloids

“…Both spectral studies of uranium on silica and conventional sorption techniques have been used by several research groups to provide data for the modeling. However, certain contradictions can be found and ambiguity remains concerning both the structure of surface complexes and their stability constants [5,6,9,11,13,14].…”