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Nienhuis ET, Pouvreau M, Graham TR, Prange MP, Page K, Loring JS, Stack AG, Clark AE, Schenter GK, Rosso KM, Pearce CI, Wang HW. Structure and reactivity of sodium aluminate complexes in alkaline solutions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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2
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Wang Y, Song D, Zhou Y, Cheng C, Zhang Y, Pearce CI, Wang Z, Clark SB, Zhu J, Rosso KM, Zhu Z, Zhang X. Molecular Examination of Ion-Pair Competition in Alkaline Aluminate Solutions Using In Situ Liquid SIMS. Anal Chem 2020; 93:1068-1075. [DOI: 10.1021/acs.analchem.0c04070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Yining Wang
- Nanjing University of Science and Technology, 200 Xiaolingwei Street, Xuanwu
District, Nanjing 210094, China
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Duo Song
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Yadong Zhou
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Cuixia Cheng
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Yanyan Zhang
- Institute of Chemistry, Chinese Academy of Sciences, No. 2, North First Street, Zhongguancun, Haidian District, Beijing 100190, China
| | - Carolyn I. Pearce
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Zheming Wang
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Sue B. Clark
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Junwu Zhu
- Nanjing University of Science and Technology, 200 Xiaolingwei Street, Xuanwu
District, Nanjing 210094, China
| | - Kevin M. Rosso
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Zihua Zhu
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
| | - Xin Zhang
- Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, Washington 99354, United States
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3
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Dembowski M, Graham TR, Reynolds JG, Clark SB, Rosso KM, Pearce CI. Influence of soluble oligomeric aluminum on precipitation in the Al-KOH-H 2O system. Phys Chem Chem Phys 2020; 22:24677-24685. [PMID: 33103701 DOI: 10.1039/d0cp04820h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The role of oligomeric aluminate species in the precipitation of aluminum (Al) phases such as gibbsite (α-Al(OH)3) from aqueous hydroxide solutions remains unclear and difficult to probe directly, despite its importance for developing accurate predictions of Al solubility in highly alkaline systems. Precipitation in this system entails a transition from predominantly tetrahedrally coordinated aluminate (Al(OH)4-) species in solution to octahedrally coordinated Al in gibbsite. Here we report a quantitative study of dissolved Al in the Al-KOH-H2O system using a combination of molecular spectroscopies. We establish a relationship between changes in 27Al NMR chemical shifts and the relative intensity of Raman vibrational bands, indicative of variations in the ensemble speciation of Al in solution, and the formation of unique contact ion pair interactions with the aluminate dimer, Al2O(OH)62-. A strong correlation between the extent of Al oligomerization and the amount of solvated Al was demonstrated by systematically varying the KOH : Al molar ratio. The concentration of dissolved oligomeric Al in solution also directly impacted the particle size and morphology of the precipitated gibbsite. High concentrations of dimeric Al2O(OH)62- yielded smaller and more numerous anhedral to subhedral gibbsite particles, while low concentrations yielded fewer and larger euhedral gibbsite platelets. The collective observations suggest a key role for the Al2O(OH)62- dimer in promoting gibbsite precipitation from solution, with the potassium ion-paired dimer catalyzing a more rapid transformation of Al from tetrahedral coordination in solution to octahedral coordination in gibbsite.
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Affiliation(s)
- Mateusz Dembowski
- Pacific Northwest National Laboratory, Richland, Washington, 99352, USA.
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4
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Sadergaski LR, DePaoli DW, Myhre KG. Monitoring the Caustic Dissolution of Aluminum Alloy in a Radiochemical Hot Cell Using Raman Spectroscopy. APPLIED SPECTROSCOPY 2020; 74:1252-1262. [PMID: 32441109 DOI: 10.1177/0003702820933616] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Chemical processing of highly radioactive materials commonly takes place in heavily shielded hot cells. The remote, real-time monitoring of chemical processing streams via optical spectroscopic techniques in hot cells may be particularly useful. Here, we describe the implementation of Raman spectroscopy and chemometric analysis to monitor the dissolution of aluminum-clad targets containing irradiated aluminum-neptunium oxide cermet pellets in caustic solutions in a hot cell environment. Partial least squares regression analysis was used to generate calibration models to quantify the concentration of dissolved aluminum, nitrate, and hydroxide in solutions within the radiochemical hot cell. This work explored a systematic approach to optimize a matrix of calibration standards using a D-optimal experimental design. The Design of Experiments-based regression model, in comparison to more traditional analytical approaches, was found to be the more practical method for building calibration models, with fewer samples, to obtain informative analytical data from Raman spectra.
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5
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Guo J, Wang Z, Cao J, Gong X. Structures of solvated tetramethylammonium aluminate species and its transformation mechanism by DFT and Raman spectra. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.07.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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6
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Guo J, Liu S, Wang Z, Cao J, Wang D. Polymerization of aluminate monomer in its initial nucleation stage of organic alkali solution revealed by ReaxFF molecular dynamics simulation. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2019.136979] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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7
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Pouvreau M, Dembowski M, Clark SB, Reynolds JG, Rosso KM, Schenter GK, Pearce CI, Clark AE. Ab Initio Molecular Dynamics Reveal Spectroscopic Siblings and Ion Pairing as New Challenges for Elucidating Prenucleation Aluminum Speciation. J Phys Chem B 2018; 122:7394-7402. [PMID: 29936837 DOI: 10.1021/acs.jpcb.8b04377] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The characterization of prenucleation species is essential to understand crystallization mechanisms across many chemical systems and often involves the use of vibrational spectroscopy. Nowhere is this more evident than in the development of "green" aluminum processing technologies, where detailed understanding of the speciation of aluminum and its polynuclear analogues in highly alkaline, low water solutions is elusive. The aluminate anion Al(OH)4- predominates in alkaline conditions, yet equilibrium with dimeric species, either μ-oxo Al2O(OH)62- or di-μ-hydroxo Al2(OH)82-, can be assumed. Using ab initio molecular dynamics with full solvation and the presence of counterions, this work reconciles previous contradictory studies that had concluded only a single species under relevant solution conditions. We reveal that the two dimers are energetically separated by 2 kcal/mol in pure water but that the stability of each can be reversed by ion pairing expected in saturated salt solutions. Simulated Raman and IR spectra for each species (accounting for anharmonicity and the fluctuating solvating environment) provide the first proof that the considered species are "spectroscopic siblings", whose multiple overlapping bands prevent definitive assertions in terms of speciation when compared to the experimental spectra. These observations are likely to hold in higher order aluminate oligomers and as such present a massive challenge toward understanding the crystallization mechanisms relevant to aluminum processing.
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Affiliation(s)
- Maxime Pouvreau
- Department of Chemistry , Washington State University , Pullman , Washington, D.C. 99164 , United States
| | - Mateusz Dembowski
- Pacific Northwest National Laboratory , Richland , Washington, D.C. 99352 , United States
| | - Sue B Clark
- Department of Chemistry , Washington State University , Pullman , Washington, D.C. 99164 , United States.,Pacific Northwest National Laboratory , Richland , Washington, D.C. 99352 , United States
| | - Jacob G Reynolds
- Washington River Protection Solutions, LLC , Richland , Washington, D.C. 99352 , United States
| | - Kevin M Rosso
- Pacific Northwest National Laboratory , Richland , Washington, D.C. 99352 , United States
| | - Gregory K Schenter
- Pacific Northwest National Laboratory , Richland , Washington, D.C. 99352 , United States
| | - Carolyn I Pearce
- Pacific Northwest National Laboratory , Richland , Washington, D.C. 99352 , United States
| | - Aurora E Clark
- Department of Chemistry , Washington State University , Pullman , Washington, D.C. 99164 , United States
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8
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Graham TR, Dembowski M, Martinez-Baez E, Zhang X, Jaegers NR, Hu J, Gruszkiewicz MS, Wang HW, Stack AG, Bowden ME, Delegard CH, Schenter GK, Clark AE, Clark SB, Felmy AR, Rosso KM, Pearce CI. In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite. Inorg Chem 2018; 57:11864-11873. [PMID: 30036042 DOI: 10.1021/acs.inorgchem.8b00617] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Trent R. Graham
- The Voiland School of Chemical and Biological Engineering, Washington State University, Pullman, Washington 99164, United States
| | - Mateusz Dembowski
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Ernesto Martinez-Baez
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Xin Zhang
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Nicholas R. Jaegers
- The Voiland School of Chemical and Biological Engineering, Washington State University, Pullman, Washington 99164, United States
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Jianzhi Hu
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | | | - Hsiu-Wen Wang
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Andrew G. Stack
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mark E. Bowden
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | | | - Gregory K. Schenter
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Aurora E. Clark
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Sue B. Clark
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Andrew R. Felmy
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - Kevin M. Rosso
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Carolyn I. Pearce
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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9
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Li N, Hu C, Fu X, Xu X, Liu R, Liu H, Qu J. Identification of Al 13 on the Colloid Surface Using Surface-Enhanced Raman Spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:2899-2906. [PMID: 28187253 DOI: 10.1021/acs.est.6b05721] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Al13 is the most active polymeric Al species responsible for coagulation at the solid-liquid interface, whereas the detection techniques for Al13 at the interface are currently limited. In this study, for the first time, the identification of Al13 on the silicon dioxide-based colloid surface was realized by using surface-enhanced Raman scattering (SERS), which is an ideal surface method sensitive for single-molecule detection. The high purity Al13 salts were prepared by an electrolysis procedure followed by precipitation or metathesis. Al13-Cln was determined to be feasible for the Raman detection as it exhibited more noticeable signals in comparison to Al13-(SO4)p and Al13-(NO3)m. The peak of Al13-Cln at 635 cm-1 could be the major characteristic peak of Al13, and the other two peaks at 300 and 987 cm-1 could be accessorial evidence for the identification. Further, the identification of Al13 adsorbed on the surface of Ag and gold-core/silica-shell colloids was confirmed by the SERS response at the above three wavenumbers with a higher signal-to-noise ratio than the normal Raman scattering. According to the least-squares fitting computed Raman spectra, each of the characteristic peaks was associated with specific vibrational modes.
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Affiliation(s)
- Ning Li
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | | | - Xiaoning Fu
- Department of Chemistry, Nankai University , Tianjin 300071, P.R. China
| | - Xiufang Xu
- Department of Chemistry, Nankai University , Tianjin 300071, P.R. China
| | | | - Huijuan Liu
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Jiuhui Qu
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
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10
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Goudarzi N. Investigation of aluminum complexes in alcoholic tetraoctylammonium (TOA) aluminate solutions using aluminum-27 NMR spectroscopy. J Mol Struct 2013. [DOI: 10.1016/j.molstruc.2013.04.052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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11
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Lu BM, Jin XY, Tang J, Bi SP. DFT studies of Al–O Raman vibrational frequencies for aquated aluminium species. J Mol Struct 2010. [DOI: 10.1016/j.molstruc.2010.07.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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13
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The Structure of Gallium in Strongly Alkaline, Highly Concentrated Gallate Solutions—a Raman and 71Ga-NMR Spectroscopic Study. J SOLUTION CHEM 2008. [DOI: 10.1007/s10953-008-9314-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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14
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27Al NMR and Raman spectroscopic studies of alkaline aluminate solutions with extremely high caustic content – Does the octahedral species Al(OH)63− exist in solution? Talanta 2006; 70:761-5. [DOI: 10.1016/j.talanta.2006.02.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 01/31/2006] [Accepted: 02/07/2006] [Indexed: 11/24/2022]
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15
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Chen Y, Feng Q, Liu K, Chen Y, Zhang G. Study on the structure of Bayer liquor with spectroscopy and MD simulation. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.03.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Sipos P, May PM, Hefter G. Quantitative determination of an aluminate dimer in concentrated alkaline aluminate solutions by Raman spectroscopy. Dalton Trans 2006:368-75. [PMID: 16365651 DOI: 10.1039/b508838k] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Raman spectra of concentrated alkaline aluminate solutions in various M'OH media (M'(+) = Na(+), K(+), Cs(+) and (CH(3))(4)N(+)) have been investigated systematically as a function of concentration and water activity, a(w). All spectra at [Al(III)](T) < or = 1 M and at 0.1 < or = [M'OH](T)/M < or = 5 (where the square brackets denote concentrations and the subscript T totals) exhibit one significant Raman mode in the low frequency region, at ca. 620 cm(-1), due to the symmetric Al(OH)(4)(-) stretch. At higher [Al(III)](T) and [M'OH](T) new modes appear at 530-550 and 700-720 cm(-1). The intensities of these new bands depend on [Al(III)](T) and a(w) but are independent of [OH(-)](T) and are only slightly cation-dependent. All three bands shift towards higher wavenumbers at [M'OH](T) > 10 M, probably due to ion-pairing. Spectra at [M'OH](T) < 10 M have been interpreted quantitatively by assuming that the integrated peak area of the 620 cm(-1) mode is linearly proportional to [Al(OH)(4)(-)] at constant a(w) and that the only significant equilibrium in these systems is the formation of a dimer that can be represented as (Al(OH)(4))(2)(2-)(aq), although it may exist in an oxo-bridged form such as [(HO)(3)Al-O-Al(OH)(3)](2). The (aquated) species Na(+), OH(-), Al(OH)(4)(-), the dimer, and their ion-pairs, were sufficient to interpret all the Raman observations. No evidence was found for various other species that have been claimed to exist in concentrated alkaline aluminate solutions.
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Affiliation(s)
- Pál Sipos
- Chemistry-DSE, Murdoch University, WA, Australia.
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17
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Johnston CT, Agnew SF, Schoonover JR, Kenney JW, Page B, Osborn J, Corbin R. Raman study of aluminum speciation in simulated alkaline nuclear waste. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2002; 36:2451-2458. [PMID: 12075803 DOI: 10.1021/es011226k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The chemistry of concentrated sodium aluminate solutions stored in many of the large, underground storage tanks containing high-level waste (HLW) at the Hanford and Savannah River Nuclear Reservations is an area of recent research interest. Not only is the presence of aluminate in solution important for continued safe storage of these wastes, the nature of both solid and solution aluminum oxyhydroxides is important for waste pretreatment. Moreover, for many tanks that have leaked high aluminum waste in the past, little is known about the speciation of Al in the soil. In this study, Raman spectroscopy has been used to investigate the speciation of the aqueous species in the Al2O3-Na2O-H2O system over a wide range of solution compositions and hydration. A ternary phase diagram has been used to correlate the observed changes in the spectra with the composition of the solution and with dimerization of aluminate that occurs at elevated aluminate concentrations (>1.5 M). Dimerization is evidenced by growth of new Al-O stretching bands at 535 and 695 cm(-1) at the expense of the aluminate monomer band at 620 cm(-1). The spectrum of water was strongly influenced by the high concentrations of Na+ and OH- (>17 M). Upon increasing the concentration of NaOH in solution, the delta-(H-O-H) bending band of water (v2 mode) increased in frequency to 1663 cm(-1), indicating that the water contained in the concentrated caustic solution was more strongly hydrogen bonded at the higher base content. In addition, the sharp, well-resolved band at 3610 cm(-1), assigned to the v(O-H) of free OH-, increased in intensity with increasing NaOH. Analysis of the v(O-H) bands in the 3800-2600 cm(-1) region supported the overall increase in hydrogen bonding as evidenced by the increase in relative intensity of a strongly hydrated water band at 3118 cm(-1). Taking into consideration the activity of water, the molar concentrations of the monomeric and dimeric aluminate species were estimated using the relative intensities of the Al-O stretching bands from the Raman spectra. A constant apparent log Kdimer value was obtained at aluminate concentrations >1.5 M with a value of 0.97+/-0.04 at approximately 25 degrees C. This study represents the first spectral-based estimation of a thermodynamic equilibrium constant for the Al2O3-Na2O-H2O system.
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Affiliation(s)
- Cliff T Johnston
- Environmental Sciences and Engineering Institute (ESEI), Purdue University, West Lafayette, Indiana 47907-1202, USA.
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18
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Fleming SD, Rohl AL, Parker SC, Parkinson GM. Atomistic Modeling of Gibbsite: Cation Incorporation. J Phys Chem B 2001. [DOI: 10.1021/jp003136s] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sean D. Fleming
- A. J. Parker Cooperative Research Centre for Hydrometallurgy, School of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia, and Department of Chemistry, University of Bath, Bath BA2 7AY, U.K
| | - Andrew L. Rohl
- A. J. Parker Cooperative Research Centre for Hydrometallurgy, School of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia, and Department of Chemistry, University of Bath, Bath BA2 7AY, U.K
| | - Steve C. Parker
- A. J. Parker Cooperative Research Centre for Hydrometallurgy, School of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia, and Department of Chemistry, University of Bath, Bath BA2 7AY, U.K
| | - Gordon M. Parkinson
- A. J. Parker Cooperative Research Centre for Hydrometallurgy, School of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia, and Department of Chemistry, University of Bath, Bath BA2 7AY, U.K
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19
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Bodor A, Tóth I, Bányai I, Szabó Z, Hefter GT. 19F NMR study of the equilibria and dynamics of the Al3+/F- system. Inorg Chem 2000; 39:2530-7. [PMID: 11197006 DOI: 10.1021/ic991248w] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A careful reinvestigation by high-field 19F NMR (470 MHz) spectroscopy has been made of the Al3+/F- system in aqueous solution under carefully controlled conditions of pH, concentration, ionic strength (I), and temperature. The 19F NMR spectra show five distinct signals at 278 K and I = 0.6 M (TMACl) which have been attributed to the complexes AlFi(3-i)+(aq) with i < or = 5. There was no need to invoke AlFi(OH)j(3-i-j)+ mixed complexes in the model under our experimental conditions (pH < or = 6.5), nor was any evidence obtained for the formation of AlF6(3-)(aq) at very high ratios of F-/Al3+. The stepwise equilibrium constants obtained for the complexes by integration of the 19F signals are in good agreement with literature data given the differences in medium and temperature. In I = 0.6 M TMACl at 278 K and in I = 3 M KCl at 298 K the log Ki values are 6.42, 5.41, 3.99, 2.50, and 0.84 (for species i = 1-5) and 6.35, 5.25, and 4.11 (for species i = 1-3), respectively. Disappearance of the 19F NMR signals under certain conditions was shown to be due to precipitation. Certain 19F NMR signals exhibit temperature- and concentration-dependent exchange broadening. Detailed line shape analysis of the spectra and magnetization transfer measurements indicate that the kinetics are dominated by F- exchange rather than complex formation. The detected reactions and their rate constants are AlF2(2+) + *F- reversible AlF*F2+ + F- (k02 = (1.8 +/- 0.3) x 10(6) M-1 s-1), AlF3(0) + *F- reversible AlF2*F0 + F- (k03 = (3.9 +/- 0.9) x 10(6) M-1 s-1), and AlF3(0) + H*F reversible AlF2*F0 + HF (kH03 = (6.6 +/- 0.5) x 10(4) M-1 s-1). The rates of these exchange reactions increase markedly with increasing F- substitution. Thus, the reactions of AlF2+(aq) were too inert to be detected even on the T1 NMR time scale, while some of the reactions of AlF3(0)(aq) were fast, causing large line broadening. The ligand exchange appears to follow an associative interchange mechanism. The cis-trans isomerization of AlF2+(aq), consistent with octahedral geometry for that complex, is slowed sufficiently to be observed at temperatures around 270 K. Difference between the Al3+/F- system and the much studied Al3+/OH- system are briefly commented on.
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Affiliation(s)
- A Bodor
- Department of Inorganic and Analytical Chemistry, Lajos Kossuth University (KLTE), H-4010 Debrecen, Pf. 21, Hungary
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20
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Li J, Prestidge CA, Addai-Mensah J. The Influence of Alkali Metal Ions on Homogeneous Nucleation of Al(OH)(3) Crystals from Supersaturated Caustic Aluminate Solutions. J Colloid Interface Sci 2000; 224:317-324. [PMID: 10727342 DOI: 10.1006/jcis.1999.6700] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homogeneous nucleation of Al(OH)(3) crystals from synthetic, optically clear, caustic aluminate solutions and the influence of alkali metal ion (Na(+) versus K(+)) have been investigated under isothermal, batch crystallization conditions. The nucleation kinetics showed a seventh-order dependence upon Al(III) relative supersaturation and a strong temperature effect. Activation energy of 160 kJ mol(-1) and interfacial energy of 33 mJ m(-2) were estimated and found to be independent of alkali ion, as was the Al(OH)(3) equilibrium solubility. The nucleation rate, however, was faster in aging sodium than in potassium aluminate solutions. It appears that Na(+) ions provide greater stability for the formation and densification of Al(III)-containing, supramolecular clusters which grow more rapidly into Al(OH)(3) crystallites than do K(+) ions. The development of the Al-OH octahedral structure of Al(OH)(3) nuclei is an alkali metal ion-mediated, chemical reaction-controlled condensation process, displaying specific gibbsite (gamma-Al(OH)(3))-bayerite (alpha-Al(OH)(3)) dimorphism. Furthermore, significant differences in the level of alkali ion incorporation, reflecting in the purity and morphology of the crystalline product, were observed. Copyright 2000 Academic Press.
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Affiliation(s)
- J Li
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia
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21
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The dissolution and interactions of gibbsite particles in alkaline media. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0167-4528(00)80039-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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