Progress 07/01/03 to 06/30/09
Outputs
OUTPUTS: There is a need to develop selective synthetic clays which can potentially remediate metal contaminated soils and water. We have prepared synthetic micas with theoretical cation exchange capacities of 462, 347 and 231 meq/100g using a new method and characterized by X-ray diffraction for phase purity, scanning electron microscopy for particle size and Al-27 and Si-29 nuclear magnetic resonance (NMR) spectroscopy. We also synthesized low charge mica-type clays and characterized them. Distribution coefficients of Sr or Ba or La were obtained for these synthetic micas, which confirmed their selectivity for these metal cations. We combined Al-27, Si-29, F-19, and Na-23 magic angle spinning (MAS) NMR to characterize the structure and interlayer cation environments in a strontium-saturated mica before and after collapse of the interlayer space after heating. Sr NMR showed that the Sr nuclei in the interlayer are bound deeply in the holes as nine coordinate inner-sphere complexes, which leads to its sequestration. Cu ion exchange equilibria of synthetic clays were also determined and the results showed very high selectivity for Cu ions. Synthetic clay was found to be useful for remediation of Cu contaminated soils. Biotite, muscovite and phlogopite micas were transformed to hydrated phases by sodium tetraphenylboron and their exchange properties were investigated. Cs and Sr ion exchange isotherms indicated that K-depleted phlogopite is highly selective for both cations and it may prove useful as an exchanger for remediation of these radioactive species from soils and ground water. Kinetics of Cs exchange revealed that the 20-2 micrometer particle size fraction of the K-depleted phlogopite took up more Cs ions than the <2 micrometer particle size fraction. Cation exchange equilibria of Cs and Sr with K-depleted biotite and muscovite were determined and biotite was found to be superior. Cation exchange equilibria of Co and Ni with K-depleted biotite and muscovite were also determined and they were found to be useful for remediation of Co and Ni. It is necessary to understand the long term stability of the transformed micas before they could be used for remediation. The K-depleted biotite treated with alkali cations produced anhydrous hydroxylated phases, while the K-depleted muscovite did not significantly exchange alkali cations but dehydrated to form Na-muscovite in all cases and this dehydration fixes the cations. The alkaline earth cations, however, produced hydrous hydroxylated phases with both K-depleted micas. PARTICIPANTS: Sridhar Komarneni, Principal investigator, Department of Crop and Soil Sciences. He contributed to the ideas and overall direction for the research, supervised students and contributed in writing papers. Ramesh Ravella, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Yunchul Cho, student in Department of Crop and Soil Sciences, carried out preparation of transformed micas and cation exchange experiments and contributed towards writing in which he has authorship. Stuckey, Jason, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Carmen Enid Martinez, Department of Crop and Soil Sciences. She contributed to the procurement of EPR spectra and contributed in writing paper. Young Dong Noh, student in Department of Crop and Soil Sciences, carried out preparation of micas and contributed in writing paper. Mackenzie, K.J.D., Professor, Victoria University of Wellington, New Zealand, carried out NMR experiments of micas and contributed in writing paper. Geoffrey Bowers, student in Department of Chemistry, carried out NMR experimental work on micas and contributed towards writing in which he has authorship. Michael Davis, student in Department of Chemistry, carried out NMR experimental work on micas and contributed towards writing in which he has authorship. Karl Mueller, professor in Department of Chemistry, contributed ideas for NMR experimental work on micas and contributed towards writing in which he has authorship. Kodama, T., Professor, Department of Chemistry & Chemical Engineering, Niigata University, Japan, contributed work on micas and contributed towards writing in which he has authorship. Gokon, N., Graduate School of Science and Technology, Niigata University, Japan, contributed work on micas and contributed towards writing in which he has authorship. Park, M. Professor, Kyungpook National University, Korea, contributed towards writing in which he has authorship. Stout, S, student in Department of Crop and Soil Sciences, carried out preparation of micas and contributed in writing paper. A. Neaman, Facultad de Agronomia, P. Universidad Catolica de, Valparaiso, Centro Regional de Estudios en Alimentos Saludables, Chile, supervised Stuckey's research and contributed in writing paper. TARGET AUDIENCES: Farmers People involved in remediation Environmental consulting companies Employees of Environmental Protection Agency Employees of Nuclear Regulatory Commission PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This project deals with the development of synthetic or modified clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Co, Ni, Ba etc and radioactive species such as Cs, Sr, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with radioactive and non-radioactive toxic metals. The transformed clays i.e, potassium depleted clays showed high selectivity for Cs, Sr, Co and Ni and they are potential candidates for remediation of radioactive and non-radioactive metal contaminated soils.
Publications
- Stuckey, J. W., A. Neaman, R. Ravella, S. Komarneni, and C. E. Martinez. 2008. Highly Charged Swelling Mica Reduces Free and Extractable Cu Levels in Cu-Contaminated Soils. Env. Sci. Tech. 42:9197-9202.
- Komarneni, S., R. Ravella, Y. D. Noh, and K. J. D. Mackenzie. 2008. Synthesis and Characterization of Low Charge Sodium Fluorophlogopite Mica-type Clay Minerals. Applied Clay Sci. 43:524-528.
- Cho, Y. and S. Komarneni. 2009. Effect of particle size on cesium exchange kinetics by K-depleted phlogopite. Applied Clay Sci. 43:401-407.
- Cho, Y. and S. Komarneni. 2009. Cation exchange equilibria of cesium and strontium with K-depleted biotite and muscovite. Applied Clay Sci. 44:15-20.
- Cho, Y. and S. Komarneni. 2009. Selectivity of cobalt and nickel by K-depleted Micas. Clays Clay Minerals 57:279-289.
- Stout, S., Y. Cho, and S. Komarneni. 2006. Uptake of cesium and strontium by potassium-depleted phlogopite. Appl. Clay Sci. 31:306-313.
- Bowers, G. M., M. C. Davis, R. Ravella, S. Komarneni, and K. T. Mueller. 2007. NMR studies of heat induced transitions in structure and cation binding environments of a strontium-saturated swelling mica. Applied Magnetic Resonance 32:595-612.
|
Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: There is a need to develop highly Cu (2+) selective materials which can potentially remediate copper contaminated soils and water. We showed that several highly charged synthetic swelling mica-type clays are highly selective for copper exchange. The synthetic micas have cation exchange capacities (CECs), which are close to their theoretical values. Both Na-saturated and Mg-saturated micas were investigated for Cu ion exchange selectivity. Ion exchange isotherms and Kielland plots were constructed using the equilibrated solution analyses. From these studies it was found that Na-4-mica and Na-3-mica could selectively exchange copper at lower concentrations from solution while Na-2-mica sample performed better by showing Cu ion exchange selectivity to almost its capacity. The EPR spectra of Cu-exchanged micas coincide with the mica's charge characteristics that predict increased binding strength of exchangeable Cu in Na-4-mica and Na-3-mica than in Na-2-mica. K-depleted phlogopite and biotite were prepared from a natural phlogopite and biotite, respectively using sodium tetraphenylborate (NaTPB). The X-ray diffraction (XRD) patterns showed that interlayer potassium ions were completely replaced with exchangeable sodium ions, resulting in the expansion of the d(001)-spacing of both K-depleted phlogopite and biotite. In order to investigate the cation exchange selectivity of K-depleted phlogopite and biotite for Co (2+) and Ni (2+) , cation exchange isotherms and Kielland plots were constructed. The isotherms and Kielland plots indicated that both K-depleted phlogopite and biotite show high selectivity for Co as well as Ni. XRD patterns after both Co and Ni exchange for Na suggest that double sheets of interlayer water are present in the interlayer. These K-depleted micas are potential cation exchange materials for removal of some heavy metals such as Ni and radioactive species such as Co-60 from solution. Cation exchange selectivity for Cs and Sr with K-depleted biotite (Na-biotite) and K-depleted muscovite (Na-muscovite) was determined with equilibration for 4 weeks at room temperature. The cation exchange isotherms and Kielland plots indicated that both K-depleted micas show high selectivity for Cs at low equivalent fraction of Cs on solid. The K-depleted micas took up Cs up to approximately 50 % of their theoretical cation exchange capacities. The XRD patterns after Na to Cs exchange reactions with K-depleted biotite showed that the d(001)-spacings collapsed from ~ 12.2 to ~11.2 A with high Cs concentrations. This collapse suggests that K-depleted biotite is able to immobilize or fix Cs ion in the interlayers. In case of exchange of Na with Sr (2+), K-depleted biotite shows high selectivity for Sr ions at low equivalent fraction of Sr on solid. The XRD patterns showed that the main d(001)-spacing of the K-depleted biotite slightly increased from 12.16 A to ~12.3 A after the exchange reactions with the high Sr concentrations. These results suggest that K-depleted biotite could be used as an ion exchanger to remove radioactive Cs-137 as well as Sr-90 from groundwater. PARTICIPANTS: Sridhar Komarneni, Principal investigator, Department of Crop and Soil Sciences. He contributed to the ideas and overall direction for the research, supervised students and contributed in writing papers. Ramesh Ravella, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Yunchul Cho, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Carmen Enid Martinez, Department of Crop and Soil Sciences. She contributed to the procurement of EPR spectra and contributed in writing paper. TARGET AUDIENCES: Farmers, People involved in remediation, Environmental consulting companies, Employees of Environmental Protection Agency, Employees of Nuclear Regulatory Commission PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This project deals with the development of synthetic or modified clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Co, Ni, etc and radioactive species such as Cs, Sr, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with radioactive and non-radioactive toxic metals. The transformed clays i.e, potassium depleted clays showed high selectivity for Cs, Sr, Co and Ni and they are potential candidates for remediation of metal contaminated soils.
Publications
- Ravella, R., S. Komarneni, and C. E. Martinez. 2008. Highly charged swelling mica type clays for selective Cu exchange. Env. Sci. Tech. 42:113-118.
- Komarneni, S. and R. Ravella. 2008. Novel clays: solid-state synthesis, characterization and cation exchange selectivity. Current Applied Physics. 8:104-106.
- Ravella, R. and S. Komarneni. 2008. Synthesis of swelling micas with stoichiometric amount of fluorine, characterization and ion exchange studies. Applied Clay Sci. 39:180-185.
|
Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: We combined Al-27, Si-29, F-19, and Na-23 magic angle spinning (MAS) NMR to characterize the structure and interlayer cation environments in a strontium-saturated member of the swelling mica family before and after a heat-induced collapse of the interlayer space. The Al-27 and Si-29 MAS NMR demonstrate that the sample consists mainly of swelling mica, though the composition does not match the ideal structural formulae. Aluminum NMR also shows that a portion of the aluminum shifts from a tetrahedral to an octahedral coordination environment upon heating. Changes in the Si-29 and F-19 NMR after heating are consistent with a structural re-arrangement of the tetrahedral sheet to permit the binding of larger cations in the di-trigonal cavity. The Na-23 MAS NMR results indicate the presence of three unique sodium environments before and after heating. The heat-invariant resonance is consistent with the presence of sodium carbonate. The other two resonances are associated with
interlayer sodium and reflect a migration of sodium to a dominantly anhydrous di-trigonal binding structure with heating. Quantitative elemental analysis and NMR data presented here suggest strontium is bound deep within the ditrigonal cavity of the collapsed micas. This type of strontium binding within ditrigonal cavities by synthetic clays leads to its sequestration. It is necessary to understand the long term stability of the transformed micas before they could be used for remediation. Therefore, we have investigated the weathering stages of K-depleted biotite, K-depleted phlogopite, and natural biotite using the hydrothermal treatment with AlCl3 solution at 200 C for 12 to 72 hrs, as an accelerated test. Although there were some differences in the degree of weathering of the above K-depleted micas, all of them first transformed to hydroxy-Al interlayered vermiculite (HIV), which then altered to kaolinite. The formation of hydroxylated phases was investigated using K-depleted
biotite (Na-biotite) and K-depleted muscovite (Na-muscovite) under hydrothermal treatment with monovalent alkali cations (Li, K, NH4, Rb, and Cs), divalent alkaline earth cations (Mg, Ca, Sr, and Ba), and trivalent aluminum (Al) cations at 200 C for one and/or three days. The K-depleted biotite treated with alkali cations produced anhydrous hydroxylated phases, while the K-depleted muscovite did not significantly exchange alkali cations but dehydrated to form Na-muscovite in all cases. The alkaline earth cations, however, produced hydrous hydroxylated phases with both K-depleted micas. The degree of hydration energy of cations and the charge density of micas were found to influence the formation of anhydrous and hydrous phases from the K-depleted micas. This type of topotactic cation exchange potentially could be used for fixation and immobilization of radioactive species such as Cs, Sr, Ra, etc. in the transformed micas. The K-depleted biotite and muscovite treated with Al cations
were transformed to hydroxy-Al interlayered vermiculites (HIV) because of hydrolysis and polymerization of Al. These HIV phases could also serve as useful adsorbents for soil and groundwater contaminants.
PARTICIPANTS: Sridhar Komarneni, principal investigator, Department of Crop and Soil Sciences, contributed to the ideas and overall direction for the research, supervised students and contributed in writing papers. Yunchul Cho, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Ramesh Ravella, student in Department of Crop and Soil Sciences, carried out preparation of micas and cation exchange experiments and contributed towards writing in which he has authorship. Geoffrey Bowers, student in Department of Chemistry, carried out NMR experimental work on micas and contributed towards writing in which he has authorship. Michael Davis, student in Department of Chemistry, carried out NMR experimental work on micas and contributed towards writing in which he has authorship. Karl Mueller, professor in Department of Chemistry, contributed ideas for NMR experimental work
on micas and contributed towards writing in which he has authorship.
TARGET AUDIENCES: Farmers, people involved in remediation, environmental consulting companies, employees of Environmental Protection Agency, and employees of Nuclear Regulatory Commission.
Impacts
This project deals with the development of synthetic or modified clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Ba etc and radioactive species such as Cs, Sr, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with radioactive and non-radioactive toxic metals. One of these synthetic clays was tested on a laboratory scale for remediation of Cu contaminated soils of Chile and it showed promising results.
Publications
- Cho, Y. and S. Komarneni. 2007. Topotactic cation exchange in transformed micas under hydrothermal conditions. Clays and Clay Minerals. 55:529-534.
- Cho, Y. and S. Komarneni. 2007. Synthesis of kaolinite from micas and K-depleted micas. Clays and Clay Minerals. 55:567-573.
- Bowers, G. M., M. C. Davis, R. Ravella, S. Komarneni, and K. T. Mueller. 2007. NMR studies of heat induced transitions in structure and cation binding environments of a strontium-saturated swelling mica. Applied Magnetic Resonance (In Press).
- Cho, Y. 2007. Cation exchange selectivity and hydrothermal reactions of K-depleted micas. Ph. D. Thesis. The Pennsylvania State University, University Park, PA. 166 pp.
- Bowers, G. M., M. C. Davis, R. Ravella, S. Komarneni, and K. T. Mueller. 2007. Heat- induced structural transformations and cation re-ordering in a synthetic swelling mica. Program and abstracts of the 44 th annual meeting of the Clay Minerals Society, June 2-7, 2007, Santa Fe, NM. p. 60 (Abstract).
|
Progress 01/01/06 to 12/31/06
Outputs
The nature of strontium binding by mineral systems directly affects the environmental transport and sequestration/remediation of radioactive strontium species at sites such as the United States Department of Energy Hanford reservation. Strontium binding in minerals has seldom been explored by direct spectroscopic means to date and is not well understood. We used solid-state NMR to observe strontium directly and indirectly in a fully strontium exchanged synthetic mica of nominal composition Na4Mg6Al4Si4O20F4 dehydrated at 500C for four hours. Analysis of the strontium NMR spectrum shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. This asymmetry parameter is consistent with a highly distorted and asymmetric coordination environment that would be produced when strontium cations are bound as inner-sphere complexes deep within the di-trigonal holes. Hydrogen-strontium TRAPDOR NMR measurements
show that two different 1H environments in the mica are associated with strontium nuclei by through-space dipolar interactions, suggesting that hydrated strontium nuclei invisible to a Sr-87 NMR experiment are bound to the external surfaces and edge sites. We conclude that the strontium nuclei in the interlayer are bound deeply in the holes as nine coordinate inner-sphere complexes. Strontium nuclei are also present on external surfaces and bound as hydrated outer-sphere complexes.
Impacts
This project deals with the development of synthetic or modified clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Ba etc and radioactive species such as Cs, Sr, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with radioactive and non-radioactive toxic metals.
Publications
- Bowers, G. M., Ravella, R., Komarneni, S., and Mueller, K. T. 2006. NMR study of strontium binding by a micaceous mineral. J. Phys. Chem. B 110:7159-7164.
- Kodama, T., Gokon, N., and Komarneni, S. 2006. Novel Synthetic Clays for Cation Exchange. Advances in Science and Technology. 45:209-217.
|
Progress 01/01/05 to 12/31/05
Outputs
An eco-friendly method for synthesizing high charge density mica with an interlayer charge of 4 per unit cell is developed, keeping the fluorine content stoichiometric in the precursors. These hydrated Na-4-mica samples were characterized by XRD, SEM, and MAS NMR. Using stoichiometric fluorine has yielded mica of less than 2 micrometer particle size as revealed by scanning electron micrographs. Distribution coefficients were obtained for these micas by conducting ion exchange studies with 0.5 N NaCl solutions containing 0.0001 N Sr or Ba cations, which confirmed the selectivity of this mica for these metal cations. Cu ion exchange equilibria of synthetic clays were also determined and the results showed very high selectivity for Cu ions. Phlogopite mica was K-depleted and equilibrated with Cs and Sr cations. Cesium and Sr ion exchange isotherms indicated that K-depleted phlogopite is highly selective for both cations, the Cs exchange capacity is 1.26 meq/g or 65% of
the theoretical cation exchange capacity and the Sr exchange capacity is 1.94 meq/g or 100% of the theoretical exchange capacity of the mica. Based on the high selectivity of K-depleted phlogopite (less than 45 micrometers) for Sr and Cs, this material may prove useful as an inorganic ion exchanger for remediation of these radioactive isotopes from soils and ground water.
Impacts
This project deals with the development of synthetic or modified clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Cs, Sr, Ba, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with radioactive and toxic metals.
Publications
- Komarneni, S., Ravella, R., and Park, M. 2005. Swelling mica-type clays: synthesis by NaCl melt method, NMR characterization and cation exchange selectivity. J. Mat. Chem.15:4241-4245.
|
Progress 01/01/04 to 12/31/04
Outputs
Several novel mica-type clays of compositions, Na(x)Si(8-x)Al(x)Mg(6)O(20)F(4).yH(2)O where x = 4, 2, 1 or 0.5 were prepared using fumed silica, aluminum oxyhydroxide (boehmite), magnesium fluoride and sodium chloride at 900oC/10 or 15 hours. Another method using kaolinite as the aluminosilicate source, magnesium fluoride and oxide and sodium chloride was investigated for the synthesis of mica with x = 4 at 900oC/ 15 hours. They were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Al-27 and Si-29 solid-state magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. Powder XRD showed that all syntheses yielded water swollen micas with c-axis spacing of 1.2 nm except in the cases where x = 4 or 2, which also showed a small peak of anhydrous mica phase with a c-axis spacing of 0.96nm. Solid-state Al-27 MASNMR spectroscopy of some micas revealed that almost all the Al is present in the tetrahedral environment.
Solid-state Si-29 MASNMR spectroscopy revealed different Si(Al) nearest neighbor environments depending upon the composition of the various micas. Cation exchange studies were performed on some of these micas and selective cation exchange studies are in progress.
Impacts
New methods are being developed for cost-effective synthesis of clays with high cation exchange capacities. These synthetic clays are of relevance in remediation of soils and waters contaminated with heavy metals and radioactive species.
Publications
- No publications reported this period
|
Progress 01/01/03 to 12/31/03
Outputs
We have prepared synthetic swelling micas of high cation exchange capacity using a new method. This method utilized sodium and magnesium chlorides in the starting precursors as fluxing agents in addition to NaF and/or magnesium fluoride. The use of these chlorides led to lower temperature of crystallization and/or better crystallinity compared to the old method where only NaF was used as a fluxing agent. Synthetic swelling micas with theoretical cation exchange capacities of 462, 347 and 231 meq/100g have been synthesized and characterized by powder X-ray diffraction for phase purity, scanning electron microscopy for particle size and Al-27 and Si-29 magic angle spinning nuclear magnetic resonance spectroscopy to determine the nearest neighbor environment of Al and Si atoms in the structure. Preliminary cation exchange selectivity studies showed that these micas exhibit high selectivity for divalent cations such as Ba and Sr and trivalent ions such as La.
Impacts
This project which has just begun deals with the development of synthetic clays for the remediation of soils and water contaminated with hazardous cations such as Cu, Ni, Sr, Ba, Ra, etc. The high capacity and highly selective clays being developed are expected to be useful for remediation of soils and water contaminated with toxic metals.
Publications
- No publications reported this period
|
|