Simonkolleite

Zinc chloride hydroxide monohydrate is a zinc hydroxy compound with chemical formula Zn₅(OH)₈Cl₂·H₂O. It is often referred to as tetrabasic zinc chloride (TBZC), basic zinc chloride, zinc hydroxychloride, or zinc oxychloride. It is a colorless crystalline solid insoluble in water. Its naturally occurring form, simonkolleite, has been shown to be a desirable nutritional supplement for animals.

Natural occurrence

The naturally occurring mineral form, ''simonkolleite,'' was described as a new mineral in 1985 for samples collected at Richelsdorf, Germany. It is a rare secondary mineral formed by weathering of zinc-bearing slag, and is associated with native zinc, hydrocerussite, diaboleite, zincite and hydrozincite. It is named after Werner Simon and Kurt Kolle, Mineral collectors of Cornberg, near Michelsdorf who submitted the samples for investigation. Simonkolleite is frequently found as a corrosion product of Zinc bearing metals.http://www.handbookofmineralogy.org/pdfs/simonkolleite.pdf Hawthorne, F. C.; Sokolova, E. "Simonkolleite, Zn₅(OH)₈Cl₂·H₂O, a Decorated Interrupted-sheet Structure of the Form φ2". ''The Canadian Mineralogist'', 2002, 40, 939.Zheng, L.; et al. "Corrosion behavior of pure zinc and its alloy under thin electrolyte layer". ''Acta Metall. Sin.'' (Engl. Lett.), 2010, 23(6), 416.

Structure

Simonkolleite is rhombohedral, space group ''R''3''m''. There are two crystallographically distinct zinc sites in Simonkolleite, both of which are fully occupied by zinc. The Zn(1) site is coordinated by six hydroxyl (OH) groups in an octahedral geometry n(OH)₆ The Zn(2) site is coordinated by three OH groups, and one Cl atom in a tetrahedral geometry n(OH)₃Cl The n(OH)₆octahedra form an edge-sharing dioctahedral sheet similar to that observed in dioctahedral micas. On each site of the vacant octahedron, a n(OH)₃Cltetrahedron is attached to three anions of the sheet and points away from the sheet. Intercalated between adjacent sheets are interstitial water (H₂O) groups. The sheets are held together by hydrogen bonding from OH groups of one sheet to Cl anions of adjacent sheets, and to interstitial H₂O groups. The n(OH)₆octahedra have four long equatorial bonds (at 2.157 Å) and two short apical bonds (at 2.066 Å). This apical shortening is a result of the bond-valence requirements of the coordinating OH groups and the connectivity of polyhedra in the structure. The equatorial OH groups (1)Hare coordinated by two Zn(1) cations and one Zn(2) cation, whereas the apical OH groups (2)Hare coordinated by three Zn(1) cations. As Zn(1) is six-coordinated and Zn(2) is four-coordinated, the local bond-valence requirements require the Zn(1)-O(1) bonds to be considerably longer than the Zn(1)-O(2) bonds. The n(OH)₃Cltetrahedron has three short Zn(2)-O(1) bonds (at 1.950 Å) and one long Zn(2)-Cl bond (2.312 Å) (Figure 1).

Properties

Simonkolleite is colorless, forms tabular hexagonal crystal up to 1 mm in diameter, and has perfect cleavage parallel to (001).

Thermal stability studies have shown that simonkolleite decomposes to ZnO at several stages upon heating (-3).Rasines, I.; Morales, J. I. "Thermal analysis of beta-Co₂(OH)₃Cl and Zn₅(OH)8Cl₂•(H₂O)". ''Thermochimica Acta'', 1980, 37, 239.Garcia-Martinez, O. et al. "On the thermal decomposition of the zinc(II) hydroxide chlorides Zn₅(OH)8Cl₂•(H₂O) and beta-Zn(OH)Cl". ''J. Mat. Sci.'' 1994, 29, 5429Hoffman, J. W.; Lauder, I. "Basic zinc chloride". ''Aust. J. Chem.'' 1968, 21, 1439Srivastava, O. K.; Secco, E. A. "Studies on metal hydroxy compounds. I. Thermal analyses of zinc derivatives e-Zn(OH)₂, Zn₅(OH)8Cl₂•(H₂O), beta-ZnOHCl, and ZnOHF." ''Can. J. Chem.'' 1967, 45, 579 The decomposition starts with loss of a single mole of the lattice water. Further dehydration at 165 ~ 210 °C produces a mixture of ZnO and an intermediate Zn(OH)Cl. At 210 ~ 300 °C, the intermediate Zn(OH)Cl decomposes to ZnO and ZnCl₂. At higher temperature, volatilization of zinc chloride occurs, leaving a final residue of zinc oxide.

The dehydrated mixture (Zn(OH)Cl and ZnO) is easily rehydrated and converted back to simonkolleite upon exposure to cool moist air ().

Simonkolleite is virtually insoluble in water and organic solvents, soluble in mineral acids yielding the corresponding zinc salts (), soluble in ammonia, amine and EDTA solutions under complex formation. It can easily be converted to zinc hydroxide by reacting with sodium hydroxide (). Its pH in water is 6.9 measured by EPA method SW846-9045.http://www.micro.net/pdf/MicroNutrients%20TBZC%20MSDS%208-22-01.pdf

Preparation

From hydrolysis of ZnCl₂

Basic zinc chloride can be prepared by hydrolysis of a ZnCl₂ solution in the presence of a base such as sodium hydroxide or ammonia (-8).Li, Y. et al. "Synthesis and characterization of simonkolleite nanodisks and their conversion into ZnO nanostructures". ''Cryst. Res. Technol.'' 2011, 1

Simonkolleite nanodisks with a width of 40 nm have been successfully synthesized via a hydrothermal method using zinc chloride and ammonia as the starting materials.

From reaction of ZnCl₂ with ZnO

Basic zinc chloride can be synthesized from the reaction of a ZnCl₂ solution with ZnO ().Ostwald, H. R.; Feitknecht, ''W. Helv. Chim. Acta.'', 1961, 44, 847Nowacki, W.; Silverman, J. H. Z. ''Kristallogr.'' 1961, 115, 21Tanaka, H.; et al. "Synthesis and characterization of layered zinc hydroxychlorides". ''J. Solid State Chem.'' 2007, 180, 2061

It can be synthesized from nano-sized ZnO particles aged in aqueous ZnCl₂ solution at 6 ~ 140 °C for 48 h. Elevating the aging temperature increases the crystallinity of basic zinc chloride.

Applications

As a feed additive and nutrition supplement for animals

Zinc is an essential trace element for all animals. It is found in all organs and tissues of the body, with bone, muscle, liver, kidney, and skin accounting for the majority of body zinc. Zinc is commonly added to diets for animals in a supplemental form, usually as inorganic feed-grade zinc oxide or zinc sulfate hydrate, or one of the organic zinc chelates and complexes. In several experiments, zinc oxide has been shown to be less bioavailable for poultry and pigs than reagent-grade or feed-grade zinc sulfate; however, the sulfate forms are highly water-soluble and thus also hygroscopic under humid conditions.Cao, J., P. R. Henry, C. B. Ammerman, R. D. Miles, and R. C. Littel. 2000. "Relative bioavailability of basic zinc sulfate and basic zinc chloride for chicks". ''J. Appl. Poultry Res.'' 9:513-517Batal, A. B., T. M. Parr, and D. H. Baker. 2001. "Zinc bioavailability in tetrabasic zinc chloride and the dietary zinc requirement of young chicks fed a soy concentrate diet". ''Poultry Sci.'' 80:87-91

Tetrabasic zinc chloride (Simonkolleite), a zinc hydroxy mineral, is a new form of zinc nutrition supplement for animals. When TBZC is made by a crystallization process (Micronutrients TBZC), it excludes contaminating ions, providing a product with greater purity and fewer dust particles than occurs with precipitation. The result is a crystalline solid that is essentially insoluble in water, non-hygroscopic, un-reactive in most foods or feedstuffs, and yet highly bioavailable.Edwards, H. M., III., and D. H. Baker. 2000. "Zinc bioavailability in soybean meal". ''J. Anim. Sci.'' 78:1017–1021Mavromichalis, I., D. M. Webel, E. N. Parr, and D. H. Baker. 2001. "Growth promoting efficacy of pharmacologic doses of tetrabasic zinc chloride in diets for nursery pigs". ''Can. J. Anim. Sci.'' 81:387–391

Since TBZC is neutral and water-insoluble, it has excellent palatability and very low interactions with other ingredients in a food mixture compared to zinc chloride, zinc sulfate or chelated forms of the metal. It also avoids the problems with caking.

It has been shown that the relative zinc bioavailability for chicks in TBZC is two to three times higher than that in Waselz-processed ZnO.

Research studies performed at universities and feed industry have all indicated that TBZC has a higher bioavailability relative to zinc sulfate, with values ranging from 102 to 111%. Four studies comparing TBZC to zinc oxide as a growth promoter all indicate improved weight gain and feed conversion at lower levels using TBZC.Hahn, J. D. and D. H. Baker. 1993. "Growth and plasma zinc responses of young pigs fed pharmacologic levels of zinc." ''J. Anim. Sci.'' 71:3020–3024Hill, G. M., G. L. Cromwell, T. D. Crenshaw, C. R. Dove, R. C. Ewan, D. A. Knabe, A. J. Lewis, G. W. Libal, D. C. Mahan, G. C. Shurson, L. L. Southern, and T. L. Veuum. 2000. "Growth promotion effects and plasma changes from feeding high dietary concentrations of zinc and copper to weanling pigs (regional study)". ''J. Anim. Sci.'' 78:1010–1016Hortin, A. E.; P. J. Bechtel and D. H. Baker. 1991. "Efficacy of pork loin as a source of zinc, and effect of added cysteine on zinc bioavailability." ''J. Food Sci.'' 56:1505–1508. Mavromichalis, I., C. M. Peter, T. M. Parr, D. Ganessunker, and D. H. Baker. 2000. "Growth promoting efficacy in young pigs of two sources of zinc oxide having either a high or a low bioavailability of zinc". ''J. Anim. Sci.'' 78:2896–2902Zhang, B.; Guo, Y. "Beneficial effects of tetrabasic zinc chloride for weanling piglets and the bioavailability of zinc in tetrabasic form relative to ZnO". ''Animal Feed Science and Technology''. 2007, 135, 75–85 Testing in vitro has shown better antimicrobial activity with TBZC than both zinc sulfate and zinc oxide.Zhang, B.; Guo, Y. "Influence of tetrabasic zinc chloride and copper sulphate on growth performance and some physiological parameters in the digestive tract of weanling piglets". ''J. Animal and Feed Sciences'', 2009, 18, 465–477 Investigation on growth performance and some physiological parameters in the digestive tract of weanling piglets has shown that TBZC stimulated the synthesis and secretion of pancreatic chymotrypsin and may promote intestinal health.

As a stabilizing agent in nutritional and fungicidal compositions

Basic zinc chloride has been used as a stabilizing agent in nutritional and fungicidal compositions for application to the foliage of growing plants.GB753251, 1956

As a Zn supplementation to metalloprotease therapy

Tetrabasic zinc chloride has been used as a Zn supplementation for increasing responsiveness to therapeutic metalloproteases, including increasing and/or maximizing responsiveness and preventing botulinum and tetanus toxin resistance due to a functional deficiency of zinc.Soparkar, C. WO2011005577A1

In oral compositions

Basic zinc chloride has been used as a therapeutically active agent in oral compositions for the care of teeth.Gibbs, C. D.; Lyle, I. G.; Smith, R. G. GB2243775A, 1991

In coating compositions

Basic zinc chloride, in combination with water-soluble alkali metal silicate, is used to coat substrates normally infested by algae, such as concrete roofing tiles and other silicate-containing building materials, to prevent or minimize algal infestation that imparts a dark, unsightly appearance.Lodge, J. R. US3998644, 1976

A Zn-based plating layer formed by basic zinc chloride and Mg has been shown to display excellent corrosion resistance.(a) Ferkous, H.; et al. "Investigation of the Ability of the Corrosion Protection of Zn-Mg Coatings". ''The Open Corrosion Journal'', 2009, 2, 26–31. (b) Hiroshi, S.; et al. JP1312081A, 1989; JP3107469A, 1991

In color development materials

Basic zinc chloride is one of the three components to prepare color development materials used for pressure-sensitive copying papers and thermo-sensitive recording papers.Osamu, F.; et al. JP55069494A

References

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Zinc minerals
Halide minerals
Nutrition