Kinetics of europium sorption to four different aluminum (hydr)oxides: Corundum, γ-alumina, bayerite, and gibbsite. (December 2018)

• Record Type: Journal Article
• Authors: Baumer, Teresa; Hixon, Amy E.
• Is Part Of: Journal of environmental radioactivity. Volume 195(2018)
• Page Start: 20
• Page End: 25
• Publication Date: 2018-12
• Subjects: Europium -- Aluminum (hydr)oxides -- Sorption -- Pseudo-first order kinetics -- Pseudo-second order kinetics -- Rate law; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2018.09.004
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: Kinetic studies can improve our understanding of the environmental mobility of radionuclides by providing insight into sorption mechanisms occurring at the mineral-water interface. While nearly identical equilibrium europium sorption edges are obtained for gibbsite (γ-Al(OH)3 ), bayerite (α-Al(OH)3 ), corundum (α-Al2 O3 ), and γ-Al2 O3, differences in surface acidity and crystal structure result in distinct reaction rates. Batch kinetic experiments were performed to investigate europium sorption to four aluminum (hydr)oxide minerals as a function of time (10–120 min), mineral concentration (0.5–50 m 2 L −1 ), pH (5–7), and europium concentration (10 −8 –10 −6 M). Linear and non-linear pseudo-first and pseudo-second order rate equations were used to fit the data. The overall reaction rates and reaction orders with respect to proton concentration, mineral concentration, and europium concentration were determined, leading to a governing rate law for each mineral system. Europium sorption is characterized by a two-step reaction with a fast initial sorption step followed by a slower sorption or aging process. The pseudo-second order equations resulted in better model fits of the data. Using the non-linear pseudo-second order rate constants, it was observed that the reaction orders for each mineral system were similar but resulted in different overall reaction rates following the trend bayerite ∼ γ-Al2 O3 > corundum > gibbsite. However, the calculated reaction orders are similar to those previously reported for plutonium(IV/V) interactions with iron (oxyhydr)oxide minerals, suggesting that these binary systems share similar elementary reactions. Highlights: Europium sorption to aluminum (hydr)oxides follows pseudo-second order kinetics. Europium sorption is characterized by a two-step reaction. Distinct sorption rates are obtained for each Eu-mineral system. Overall reaction rates follow the trend bayerite ∼ γ-Al2 O3 > corundum > gibbsite.