Nanoscale size effects on uranium(VI) adsorption to hematite.
U(VI) adsorption on aerosol-synthesized hematite particles ranging in size from 12 to 125 nm was studied to explore nanoscale size effects on uranium adsorption. Adsorption on 70 nm aqueous-synthesized particles was also investigated to examine the effect of the synthesis method on reactivity. Equilibrium adsorption was measured over pH 3-11 at two U(VI) loadings. Surface complexation modeling, combined with adjustment of adsorption equilibrium constants to be independent of site density and surface area, provided a quantitative reaction-based framework for evaluating adsorption affinity and capacity. Among the aerosol-synthesized particles, the adsorption affinity decreased as the particle size increased from 12 to 125 nm with similar intermediate affinities for 30 and 50 nm particles. X-ray absorption fine structure spectroscopy measurements suggest that the differences in adsorption affinity and capacity are not the result of substantially different coordination environments of adsorbed U(VI).
Departments of Energy, Environmental and Chemical Engineering and of Earth and Planetary Sciences and Center for Materials Innovation, Washington University, St. Louis, Missouri 63130, USA.
Hui
H
Zeng
Abhas
A
Singh
Soubir
S
Basak
Kai-Uwe
KU
Ulrich
Manoranjan
M
Sahu
Pratim
P
Biswas
Jeffrey G
JG
Catalano
Daniel E
DE
Giammar
D000143:Acids / Q000737:chemistry; D000327:Adsorption; D000468:Alkalies / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013057:Spectrum Analysis; D013499:Surface Properties; D017186:Titrimetry; D014501:Uranium / Q000737:chemistry*
D000143:Acids; D000468:Alkalies; D005290:Ferric Compounds; C000499:ferric oxide; D014501:Uranium