Effect of grain size on uranium(VI) surface complexation kinetics and adsorption additivity.
Environ Sci Technol
; 45(14): 6025-31, 2011 Jul 15.
Article
in En
| MEDLINE
| ID: mdl-21648458
ABSTRACT
The contribution of variable grain sizes to uranium adsorption/desorption was studied using a sediment from the US DOE Hanford site. The sediment was wet sieved into four size fractions coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.053-0.2 mm), and clay/silt fraction (<0.053 mm). For each size fraction and their composite (sediment), batch and flow-cell experiments were performed to determine uranium adsorption isotherms and kinetic uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. One important implication of this study is that grain-size distribution may be used to estimate uranium adsorption site and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.
Full text:
1
Database:
MEDLINE
Main subject:
Particle Size
/
Uranium
/
Geologic Sediments
/
Models, Chemical
Type of study:
Prognostic_studies
Country/Region as subject:
America do norte
Language:
En
Journal:
Environ Sci Technol
Year:
2011
Type:
Article
Affiliation country:
United States