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Wikipedia

Hydrotalcite

January 25, 2023

Hydrotalcite or formerly also Völknerite[6] is a layered double hydroxide (LDH) of general formula Mg
6Al
2CO
3(OH)
16·4H
2O, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate ions exist. The easily exchanged carbonates allow for applications of the mineral in wastewater treatment and nuclear fuel reprocessing.

Hydrotalcite
Hydrotalcite with serpentine, Snarum, Modum, Buskerud, Norway. Size: 8.4 x 5.2 x 4.1 cm
General
CategoryCarbonate mineral
Formula
(repeating unit)		Mg6Al2CO3(OH)16·4H2O
IMA symbolHtc[1]
Strunz classification5.DA.50
Crystal system3R polytype: Trigonal
2H polytype: Hexagonal
Crystal class3R polytype: Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
2H polytype: Dihexagonal dipyramidal (6/mmm)
Space groupR3m
Unit cella = 3.065 Å,
c = 23.07 Å; Z = 3
Identification
ColorWhite with possible brownish tint
Crystal habitSubhedral platey crystals, lamellar-fibrous, rarely euhedral prismatic; commonly foliated, massive
Cleavage{0001}, perfect
TenacityFlexible, not elastic
Mohs scale hardness2
LusterSatiny to greasy or waxy
StreakWhite
DiaphaneityTransparent
Specific gravity2.03 - 2.09
Optical propertiesUniaxial (-)
Refractive indexnω = 1.511 - 1.531 nε = 1.495 - 1.529
Birefringenceδ = 0.016
Other characteristicsGreasy feel
References[2][3][4][5]

Structure and discovery

It was first described in 1842 for an occurrence in a serpentine - magnesite deposit in Snarum, Modum, Buskerud, Norway.[2] It occurs as an alteration mineral in serpentinite in association with serpentine, dolomite and hematite.[3] The layers of the structure stack in multiple ways, to produce a 3-layer rhombohedral structure (3R Polytype), or a 2-layer hexagonal structure (2H polytype) formerly known as manasseite. The two polytypes are often intergrown.[2][3][5]

Applications

Nuclear fuel reprocessing

Hydrotalcite has been studied as potential getter for iodide in order to scavenge the long-lived 129I (T1/2 = 15.7 million years) and also other fission products such as 79Se (T1/2 = 327,000 years) and 99Tc, (T1/2 = 211,000 years) present in spent nuclear fuel to be disposed under oxidising conditions in volcanic tuff at the Yucca Mountain nuclear waste repository. However, carbonate anions easily replace iodide anions in its interlayer and therefore the selectivity coefficient for the anion exchange is not favorable. Another difficulty arising in the quest of an iodide getter for radioactive waste is the long-term stability of the sequestrant that must survive over geological time scales.

Anion exchange

Layered double hydroxides (LDH) are well known for their anion exchange properties.[citation needed]

Medical

Hydrotalcite is also used as an antacid, such as Maalox (magnesium-aluminium oxide).[7]

Wastewater treatment

Treating mining and other wastewater by creating hydrotalcites often produces substantially less sludge than lime. In one test, final sludge reductions reached up to 90 percent. This alters the concentration of magnesium and aluminum and raises the pH of water. As the crystals form, they trap other waste substances including radium, rare earths, anions and transition metals. The resulting mixture can be removed via settling, centrifuge, or other mechanical means.[8]

See also

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Mindat.org
  3. ^ a b c Handbook of Mineralogy
  4. ^ Webmineral data
  5. ^ a b (PDF). Archived from the original (PDF) on 2013-05-24. Retrieved 2012-11-25.
  6. ^ Rammelsberg, C. (1856-05-01). "On völknerite or hydrotalkite, and the so-called steatite of Snarum". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 11 (73): 405–407. doi:10.1080/14786445608642090. ISSN 1941-5982.
  7. ^ "Hydrotalcite – Drugs.com". July 2021.
  8. ^ Hoopes, Heidi (June 12, 2014). "Wastewater that cleans itself results in more water, less sludge". www.gizmag.com. Retrieved 2016-06-11.
  • Douglas, G., Shackleton, M. and Woods, P. (2014). Hydrotalcite formation facilitates effective contaminant and radionuclide removal from acidic uranium mine barren lixiviant. Applied Geochemistry, 42, 27-37.
  • Douglas, G.B. (2014). Contaminant removal from Baal Gammon acidic mine pit water via in situ hydrotalcite formation. Applied Geochemistry, 51, 15-22.

Further reading

  • Jow, H. N.; R. C. Moore; K. B. Helean; S. Mattigod; M. Hochella; A. R. Felmy; J. Liu; K. Rosso; G. Fryxell; J. Krumhansl (2005). Yucca Mountain Project-Science & Technology Radionuclide Absorbers Development Program Overview. Yucca Mountain Project, Las Vegas, Nevada (US).
  • Jow, H. N.; R. C. Moore; K. B. Helean; J. Liu; J. Krumhansl; Y. Wang; S. Mattigod; A. R. Felmy; K. Rosso; G. Fryxell (February 2005). "Radionuclide absorbers development program overview Office of Civilian Radioactive Waste Management (OCRWM), Science and Technology Program": 13ofviewgrahs. {{cite journal}}: Cite journal requires |journal= (help)
  • Kaufhold, S.; M. Pohlmann-Lortz; R. Dohrmann; R. Nüesch (2007). "About the possible upgrade of bentonite with respect to iodide retention capacity". Applied Clay Science. 35 (1–2): 39–46. doi:10.1016/j.clay.2006.08.001.
  • Krumhansl, J. L.; P. Zhang; H. R. Westrich; C. R. Bryan; M. A. Molecke (2000). "Technetium getters in the near surface environment". Migration Conference. 99.
  • Krumhansl, J. L.; J. D. Pless; J. B. Chwirka; K. C. Holt (2006). Yucca Mountain Project getter program results (Year 1) I-I29 and other anions of concern. SAND2006-3869, Yucca Mountain Project, Las Vegas, Nevada.
  • Mattigod, S. V.; G. E. Fryxell; R. J. Serne; K. E. Parker (2003). "Evaluation of novel getters for adsorption of radioiodine from groundwater and waste glass leachates". Radiochimica Acta. 91 (9): 539–546. doi:10.1524/ract.91.9.539.20001. S2CID 97175034.
  • Mattigod, S. V.; R. J. Serne; G. E. Fryxell (2003). Selection and testing of getters for adsorption of iodine-129 and technetium-99: a review. PNNL-14208, Pacific Northwest National Lab., Richland, WA (US).
  • Moore, R. C.; W. W. Lukens (2006). Workshop on development of radionuclide getters for the Yucca Mountain waste repository: proceedings. SAND2006-0947, Sandia National Laboratories.
  • Pless, J. D.; J. Benjamin Chwirka; J. L. Krumhansl (2007). "Iodine sequestration using delafossites and layered hydroxides". Environmental Chemistry Letters. 5 (2): 85–89. doi:10.1007/s10311-006-0084-8. S2CID 98329183.
  • Stucky, G.; H. M. Jennings; S. K. Hodson (1992). Engineered cementitious contaminant barriers and their method of manufacture. Google Patents.

January 25, 2023
hydrotalcite, formerly, also, völknerite, layered, double, hydroxide, general, formula, whose, name, derived, from, resemblance, with, talc, high, water, content, multiple, structures, containing, loosely, bound, carbonate, ions, exist, easily, exchanged, carb. Hydrotalcite or formerly also Volknerite 6 is a layered double hydroxide LDH of general formula Mg6 Al2 CO3 OH 16 4H2 O whose name is derived from its resemblance with talc and its high water content Multiple structures containing loosely bound carbonate ions exist The easily exchanged carbonates allow for applications of the mineral in wastewater treatment and nuclear fuel reprocessing HydrotalciteHydrotalcite with serpentine Snarum Modum Buskerud Norway Size 8 4 x 5 2 x 4 1 cmGeneralCategoryCarbonate mineralFormula repeating unit Mg6Al2CO3 OH 16 4H2OIMA symbolHtc 1 Strunz classification5 DA 50Crystal system3R polytype Trigonal 2H polytype HexagonalCrystal class3R polytype Hexagonal scalenohedral 3 m H M symbol 3 2 m 2H polytype Dihexagonal dipyramidal 6 mmm Space groupR3 mUnit cella 3 065 A c 23 07 A Z 3IdentificationColorWhite with possible brownish tintCrystal habitSubhedral platey crystals lamellar fibrous rarely euhedral prismatic commonly foliated massiveCleavage 0001 perfectTenacityFlexible not elasticMohs scale hardness2LusterSatiny to greasy or waxyStreakWhiteDiaphaneityTransparentSpecific gravity2 03 2 09Optical propertiesUniaxial Refractive indexnw 1 511 1 531 ne 1 495 1 529Birefringenced 0 016Other characteristicsGreasy feelReferences 2 3 4 5 Contents 1 Structure and discovery 2 Applications 2 1 Nuclear fuel reprocessing 2 2 Anion exchange 2 3 Medical 2 4 Wastewater treatment 3 See also 4 References 5 Further readingStructure and discovery EditIt was first described in 1842 for an occurrence in a serpentine magnesite deposit in Snarum Modum Buskerud Norway 2 It occurs as an alteration mineral in serpentinite in association with serpentine dolomite and hematite 3 The layers of the structure stack in multiple ways to produce a 3 layer rhombohedral structure 3R Polytype or a 2 layer hexagonal structure 2H polytype formerly known as manasseite The two polytypes are often intergrown 2 3 5 Applications EditNuclear fuel reprocessing Edit Hydrotalcite has been studied as potential getter for iodide in order to scavenge the long lived 129I T1 2 15 7 million years and also other fission products such as 79Se T1 2 327 000 years and 99Tc T1 2 211 000 years present in spent nuclear fuel to be disposed under oxidising conditions in volcanic tuff at the Yucca Mountain nuclear waste repository However carbonate anions easily replace iodide anions in its interlayer and therefore the selectivity coefficient for the anion exchange is not favorable Another difficulty arising in the quest of an iodide getter for radioactive waste is the long term stability of the sequestrant that must survive over geological time scales Anion exchange Edit Layered double hydroxides LDH are well known for their anion exchange properties citation needed Medical Edit Hydrotalcite is also used as an antacid such as Maalox magnesium aluminium oxide 7 Wastewater treatment Edit Treating mining and other wastewater by creating hydrotalcites often produces substantially less sludge than lime In one test final sludge reductions reached up to 90 percent This alters the concentration of magnesium and aluminum and raises the pH of water As the crystals form they trap other waste substances including radium rare earths anions and transition metals The resulting mixture can be removed via settling centrifuge or other mechanical means 8 See also EditBarbertonite Brucite Mg OH 2 Fougerite Layered double hydroxide LDH Magnesium hydroxide StichtiteReferences Edit Warr L N 2021 IMA CNMNC approved mineral symbols Mineralogical Magazine 85 3 291 320 Bibcode 2021MinM 85 291W doi 10 1180 mgm 2021 43 S2CID 235729616 a b c Mindat org a b c Handbook of Mineralogy Webmineral data a b IMA Nomenclature Report PDF Archived from the original PDF on 2013 05 24 Retrieved 2012 11 25 Rammelsberg C 1856 05 01 On volknerite or hydrotalkite and the so called steatite of Snarum The London Edinburgh and Dublin Philosophical Magazine and Journal of Science 11 73 405 407 doi 10 1080 14786445608642090 ISSN 1941 5982 Hydrotalcite Drugs com July 2021 Hoopes Heidi June 12 2014 Wastewater that cleans itself results in more water less sludge www gizmag com Retrieved 2016 06 11 Douglas G Shackleton M and Woods P 2014 Hydrotalcite formation facilitates effective contaminant and radionuclide removal from acidic uranium mine barren lixiviant Applied Geochemistry 42 27 37 Douglas G B 2014 Contaminant removal from Baal Gammon acidic mine pit water via in situ hydrotalcite formation Applied Geochemistry 51 15 22 Further reading EditJow H N R C Moore K B Helean S Mattigod M Hochella A R Felmy J Liu K Rosso G Fryxell J Krumhansl 2005 Yucca Mountain Project Science amp Technology Radionuclide Absorbers Development Program Overview Yucca Mountain Project Las Vegas Nevada US Jow H N R C Moore K B Helean J Liu J Krumhansl Y Wang S Mattigod A R Felmy K Rosso G Fryxell February 2005 Radionuclide absorbers development program overview Office of Civilian Radioactive Waste Management OCRWM Science and Technology Program 13ofviewgrahs a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Kaufhold S M Pohlmann Lortz R Dohrmann R Nuesch 2007 About the possible upgrade of bentonite with respect to iodide retention capacity Applied Clay Science 35 1 2 39 46 doi 10 1016 j clay 2006 08 001 Krumhansl J L P Zhang H R Westrich C R Bryan M A Molecke 2000 Technetium getters in the near surface environment Migration Conference 99 Krumhansl J L J D Pless J B Chwirka K C Holt 2006 Yucca Mountain Project getter program results Year 1 I I29 and other anions of concern SAND2006 3869 Yucca Mountain Project Las Vegas Nevada Mattigod S V G E Fryxell R J Serne K E Parker 2003 Evaluation of novel getters for adsorption of radioiodine from groundwater and waste glass leachates Radiochimica Acta 91 9 539 546 doi 10 1524 ract 91 9 539 20001 S2CID 97175034 Mattigod S V R J Serne G E Fryxell 2003 Selection and testing ofgettersfor adsorption of iodine 129 and technetium 99 a review PNNL 14208 Pacific Northwest National Lab Richland WA US Moore R C W W Lukens 2006 Workshop on development of radionuclide getters for the Yucca Mountain waste repository proceedings SAND2006 0947 Sandia National Laboratories Pless J D J Benjamin Chwirka J L Krumhansl 2007 Iodine sequestration using delafossites and layered hydroxides Environmental Chemistry Letters 5 2 85 89 doi 10 1007 s10311 006 0084 8 S2CID 98329183 Stucky G H M Jennings S K Hodson 1992 Engineered cementitious contaminant barriers and their method of manufacture Google Patents Retrieved from https en wikipedia org w index php title Hydrotalcite amp oldid 1133337747, wikipedia, wiki, book, books, library,

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