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Adsorption of Eu(III) onto bentonite and phyllite: A comparative study
https://orcid.org/0000-0002-8270-9384
Abstract Disposal of radioactive wastes in underground repositories necessitates knowledge on adsorption and mobility of radionuclides in host rocks (geologic barrier) and in engineered barriers, including clay barrier. The batch adsorption of Eu(III) (a homologue for trivalent radionuclides) onto phyllite compared to bentonite was studied as a function of solution pH (4.5 and 7.0), solution to clay rock ratio (10:1, 100:1, 500:1 and 1000:1), and various Eu(III) concentrations (0.01–190 mg/L; 0.658 × 10−7–1.25 × 10−3 M). The experimental data were interpreted using the isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich, Tóth, and Sips. Adsorption/desorption experiments and bonding strength calculations showed that the adsorption behavior depends on the mineral composition of sorbents, solution pH, the initial concentration of Eu(III), and liquid: solution ratio (L:S). The cation exchange within the interlayer space of montmorillonite is the main adsorption mechanism in bentonite. Cation exchange on the minerals surface, chemical reactions leading to the precipitation of new phases, the electrostatic effect at a low initial concentration of Eu (III), and pH > pHPZC are adsorption mechanisms in phyllites. Solution pH has a pronounced effect on the Eu(III) adsorption onto phyllite due to surface protonation. Fe-oxides and hydroxides play a significant role in the adsorption/desorption of Eu(III) on phyllites. The best fitting was obtained for three-parameter isotherm models of Sips and Tóth. The mechanism of Eu(III) binding is complex and does not follow the ideal monolayer adsorption. While the maximum adsorption capacity of phyllite is 2.5 to 6.6 times lower than of bentonite, depending on the solution pH, it is high enough to guarantee efficacious and durable removal of actinides from the contaminated solutions, particularly at their low concentrations. Phyllites adsorption and mechanical properties make them suitable additives to bentonite in a clay barrier.
Graphical abstract Display Omitted
Highlights Eu(III) adsorption on phyllites as a function of pH, solution:clay rock phase ratio, and concentration has been investigated; The adsorption of Eu(III) on phyllites was compared with that on bentonite sorbents; The Langmuir, Freundlich, Dubinin-Radushkevich, Toth, and Sips isotherm models were applied; The main type of adsorption on phyllites and bentonite identified; pH and Fe forms are important factors affecting Eu (III) adsorption on phyllites.
Adsorption of Eu(III) onto bentonite and phyllite: A comparative study
https://orcid.org/0000-0002-8270-9384
Abstract Disposal of radioactive wastes in underground repositories necessitates knowledge on adsorption and mobility of radionuclides in host rocks (geologic barrier) and in engineered barriers, including clay barrier. The batch adsorption of Eu(III) (a homologue for trivalent radionuclides) onto phyllite compared to bentonite was studied as a function of solution pH (4.5 and 7.0), solution to clay rock ratio (10:1, 100:1, 500:1 and 1000:1), and various Eu(III) concentrations (0.01–190 mg/L; 0.658 × 10−7–1.25 × 10−3 M). The experimental data were interpreted using the isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich, Tóth, and Sips. Adsorption/desorption experiments and bonding strength calculations showed that the adsorption behavior depends on the mineral composition of sorbents, solution pH, the initial concentration of Eu(III), and liquid: solution ratio (L:S). The cation exchange within the interlayer space of montmorillonite is the main adsorption mechanism in bentonite. Cation exchange on the minerals surface, chemical reactions leading to the precipitation of new phases, the electrostatic effect at a low initial concentration of Eu (III), and pH > pHPZC are adsorption mechanisms in phyllites. Solution pH has a pronounced effect on the Eu(III) adsorption onto phyllite due to surface protonation. Fe-oxides and hydroxides play a significant role in the adsorption/desorption of Eu(III) on phyllites. The best fitting was obtained for three-parameter isotherm models of Sips and Tóth. The mechanism of Eu(III) binding is complex and does not follow the ideal monolayer adsorption. While the maximum adsorption capacity of phyllite is 2.5 to 6.6 times lower than of bentonite, depending on the solution pH, it is high enough to guarantee efficacious and durable removal of actinides from the contaminated solutions, particularly at their low concentrations. Phyllites adsorption and mechanical properties make them suitable additives to bentonite in a clay barrier.
Graphical abstract Display Omitted
Highlights Eu(III) adsorption on phyllites as a function of pH, solution:clay rock phase ratio, and concentration has been investigated; The adsorption of Eu(III) on phyllites was compared with that on bentonite sorbents; The Langmuir, Freundlich, Dubinin-Radushkevich, Toth, and Sips isotherm models were applied; The main type of adsorption on phyllites and bentonite identified; pH and Fe forms are important factors affecting Eu (III) adsorption on phyllites.
Adsorption of Eu(III) onto bentonite and phyllite: A comparative study
https://orcid.org/0000-0002-8270-9384
Abstract Disposal of radioactive wastes in underground repositories necessitates knowledge on adsorption and mobility of radionuclides in host rocks (geologic barrier) and in engineered barriers, including clay barrier. The batch adsorption of Eu(III) (a homologue for trivalent radionuclides) onto phyllite compared to bentonite was studied as a function of solution pH (4.5 and 7.0), solution to clay rock ratio (10:1, 100:1, 500:1 and 1000:1), and various Eu(III) concentrations (0.01–190 mg/L; 0.658 × 10−7–1.25 × 10−3 M). The experimental data were interpreted using the isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich, Tóth, and Sips. Adsorption/desorption experiments and bonding strength calculations showed that the adsorption behavior depends on the mineral composition of sorbents, solution pH, the initial concentration of Eu(III), and liquid: solution ratio (L:S). The cation exchange within the interlayer space of montmorillonite is the main adsorption mechanism in bentonite. Cation exchange on the minerals surface, chemical reactions leading to the precipitation of new phases, the electrostatic effect at a low initial concentration of Eu (III), and pH > pHPZC are adsorption mechanisms in phyllites. Solution pH has a pronounced effect on the Eu(III) adsorption onto phyllite due to surface protonation. Fe-oxides and hydroxides play a significant role in the adsorption/desorption of Eu(III) on phyllites. The best fitting was obtained for three-parameter isotherm models of Sips and Tóth. The mechanism of Eu(III) binding is complex and does not follow the ideal monolayer adsorption. While the maximum adsorption capacity of phyllite is 2.5 to 6.6 times lower than of bentonite, depending on the solution pH, it is high enough to guarantee efficacious and durable removal of actinides from the contaminated solutions, particularly at their low concentrations. Phyllites adsorption and mechanical properties make them suitable additives to bentonite in a clay barrier.
Graphical abstract Display Omitted
Highlights Eu(III) adsorption on phyllites as a function of pH, solution:clay rock phase ratio, and concentration has been investigated; The adsorption of Eu(III) on phyllites was compared with that on bentonite sorbents; The Langmuir, Freundlich, Dubinin-Radushkevich, Toth, and Sips isotherm models were applied; The main type of adsorption on phyllites and bentonite identified; pH and Fe forms are important factors affecting Eu (III) adsorption on phyllites.
Adsorption of Eu(III) onto bentonite and phyllite: A comparative study
Kyzioł-Komosińska, J. (author) / Janeczek, J. (author) / Krzykawski, T. (author) / Fabiańska, M.J. (author) / Matuszewska, A. (author) / Dzieniszewska, A. (author) / Teper, E. (author) / Pająk, M. (author) / Sawicka, N. (author)
Applied Clay Science ; 183
2019-10-10
Article (Journal)
Electronic Resource
English
Phyllite , Europium (III) ions , Adsorption/desorption , Radioactive waste repository barriers , B , bentonite , BCR test , the European Community Bureau of Reference procedure for the four-stage sequential extraction , BET , Braunauer-Emmett-Teller theory , BJH (Barrett, Joyner, and Halenda) method , a procedure for calculating pore size distributions from experimental isotherms using the Kelvin model of pore filling , CEC , cation exchange capacity , Fy , phyllite , L:S , solution volume to rock mass ratio , RE , removal efficacy , VDH , very deep boreholes , D<inf>e</inf> , water desorption efficacy, % , M<inf>de</inf> , the amount of desorbed Eu(III), mg/g , q , the amount of adsorbed Eu(III), mg/g
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