- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting point
- Density
- Solubility
- Chemical properties
- Obtaining
- Applications
- In medical treatments
- In veterinary applications
- As a flame retardant
- In dental treatments
- To separate dangerous minerals from arsenic
- In obtaining other zinc compounds
- In the recovery of zinc from waste effluents
- Other apps
- Risks
- Effects on the environment
- References
The zinc carbonate is an inorganic compound consisting of the elements zinc (Zn), carbon (C) and oxygen (O). Its chemical formula is ZnCO 3. Zinc has an oxidation state of +2, carbon +4 and oxygen -2.
It is a colorless or white solid that is found in nature, forming the mineral smithsonite, in which it can be alone or with other elements such as cobalt or copper, which give it a violet or green color respectively.
Smithsonite, ZnCO 3 mineral. Rob Lavinsky, iRocks.com - CC-BY-SA-3.0 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0). Source: Wikimedia Commons.
ZnCO 3 is almost insoluble in water, but it dissolves easily in dilute acids, as the carbonate ion in an acid medium forms carbonic acid (H 2 CO 3), which then becomes CO 2 gas and water.
It is used as an antiseptic in animal wounds and is sometimes supplied in the diet to prevent diseases caused by zinc deficiency.
It serves to delay the burning of certain fibers, plastics and rubber when they come into contact with fire. It allows to separate toxic arsenic minerals from other rocks safely.
It has been used in toothpastes to restore dentin on teeth undergoing whitening.
Structure
ZnCO 3 is made up of a Zn 2+ cation and a CO 3 2- anion. The carbon in the carbonate ion has an oxidation state of +4. This ion has a flat structure with the three oxygen atoms surrounding the carbon atom.
Chemical structure of zinc carbonate. Unknown author / Public domain. Source: Wikimedia Commons.
Nomenclature
- Zinc carbonate
- Zinc Monocarbonate
- Carbonic acid zinc salt
- Smithsonite
- Zinc spar
Properties
Physical state
Colorless or white crystalline solid. Rhombic crystals.
Zinc carbonate. Ondřej Mangl / Public domain. Source: Wikimedia Commons.
Molecular weight
125.4 g / mol
Melting point
At 140 ºC it decomposes without melting.
Density
4.398 g / cm 3 at 20 ° C.
Solubility
Practically insoluble in water: 0.000091 g / 100 g of H 2 O at 20 ° C. Soluble in dilute acids, alkalis and ammonium salt solutions. Insoluble in ammonia, alcohol and acetone.
Chemical properties
Reacts with acids forming carbon dioxide:
ZnCO 3 + 2 H + → Zn 2+ + H 2 O + CO 2 ↑
It dissolves in bases forming the hydroxide, which partially dissolves forming a zincate ion:
ZnCO 3 + 2 OH - → Zn (OH) 2 + CO 3 2-
Zn (OH) 2 + H 2 O + OH - → -
It is not flammable. When it is heated to decomposition it produces zinc oxide and carbon dioxide, but it can even emit carbon monoxide (CO).
ZnCO 3 + heat → ZnO + CO 2 ↑
Obtaining
It is obtained by grinding the mineral smithsonite, formerly called zinc spar.
It can also be prepared by mixing a sodium carbonate solution with a zinc salt, such as zinc sulfate. The sodium sulfate remains dissolved and the zinc carbonate precipitates:
ZnSO 4 + Na 2 CO 3 → ZnCO 3 ↓ + Na 2 SO 4
Applications
In medical treatments
This compound makes it possible to obtain some pharmaceutical products. It is applied to inflamed skin as a powder or lotion.
In veterinary applications
ZnCO 3 serves as an astringent, antiseptic, and topical wound protector in animals.
It also helps prevent diseases caused by zinc deficiency, so it is used as a supplement in the diet of some animals, provided that the amounts administered are within the standards established by health agencies.
Zinc carbonate is sometimes given as a micronutrient to prevent disease in pigs. Unknown author / CC0. Source: Wikimedia Commons.
In outbreaks of parakeratosis in pigs, it is added to their diet. This disease is an alteration of the skin in which the horny layer is not formed correctly.
As a flame retardant
It is used as a fireproof filler for rubbers and plastics that are exposed to high temperatures. Protects textile fibers from fire.
In the case of cotton textiles, it is applied to the fabric along with some alkali. This directly attacks the primary hydroxyl groups (–CH 2 OH) of cellulose and converts them to sodium cellulose (–CH 2 ONa).
The breaking of cellulose bonds by alkali favors a greater penetrability of the chains of the compact cellulosic structure, so that more ZnCO 3 manages to enter the amorphous zone of this and its dispersion is facilitated.
Some cotton fabrics may contain ZnCO 3 in their fibers to make them fire resistant. Socken_farbig.jpeg: Scott Bauerderivative work: Socky / Public domain. Source: Wikimedia Commons.
As a result, the amount of flammable gas that could be produced by fire is reduced.
In dental treatments
Certain toothpastes based on zinc carbonate nanocrystals and hydroxyapatite applied regularly to the teeth reduce hypersensitivity more effectively than those based on fluoride.
ZnCO 3 and hydroxyapatite nanocrystals have a size, shape, chemical composition and crystallinity similar to that of dentin, so the dentinal tubules can be closed with the application of these materials.
ZnCO 3 -hydroxyapatite nanoparticles have been successfully tested to decrease sensitivity in bleached teeth. Author: Photo Mix. Source: Pixabay.
This type of toothpaste proved useful after teeth whitening processes.
To separate dangerous minerals from arsenic
Methods of separating arsenic minerals from sulfide rocks (such as galena, chalcopyrite and pyrite) using ZnCO 3 have been tested. The mineral rich in arsenic must be separated from the others because this element is a very toxic and poisonous pollutant for living beings.
To achieve this, the mixture of ground rocks is treated with a solution of zinc sulfate and sodium carbonate at a pH of 7.5-9.0 and a xanthate compound.
Arsenopyrite. This mineral must be separated from others because it contains the toxic arsenic. Separation can be achieved with zinc carbonate. James St. John / CC BY (https://creativecommons.org/licenses/by/2.0). Source: Wikimedia Commons.
The effectiveness of the formula is attributed to the formation of small ZnCO 3 particles on the surface of the arsenopyrite, making it hydrophilic (similar to water), so it cannot adhere to air bubbles and cannot float, precipitating and separating of the other minerals.
In obtaining other zinc compounds
Zinc carbonate has been used to obtain hydrophobic zinc borate nanostructures of the formula 3ZnO • 3B 2 O 3 • 3.5H 2 O. This material can be used as a flame retardant additive in polymers, wood and textiles.
In the recovery of zinc from waste effluents
Synthetic waters rich in zinc ions discarded by electrodeposition processes can be treated by fluidized bed technology using sodium carbonate to precipitate ZnCO 3.
When Zn 2+ is precipitated in the form of carbonate, its concentration decreases, the solid obtained is filtered and the waters can be disposed of safely. The precipitated ZnCO 3 is of high purity.
Other apps
It allows to prepare other zinc compounds. It is used in cosmetics. It serves as a pigment and is used in the manufacture of porcelains, ceramics and pottery.
Risks
Inhalation of ZnCO 3 dust can cause a dry throat, cough, chest discomfort, fever, and sweating. Its ingestion causes nausea and vomiting.
Effects on the environment
The main risk is its effect on the environment, so it should be avoided that it is spread in it. It is very toxic to aquatic life with consequences that persist in living organisms.
References
- US National Library of Medicine. (2019). Zinc carbonate. Recovered from pubchem.ncbi.nlm.nih.gov.
- Lide, DR (editor) (2003). CRC Handbook of Chemistry and Physics. 85 th CRC Press.
- Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.
- Sharma, V. et al. (2018). Synthesis of zinc carbonate nanoneedles, a potential flame retardant for cotton textiles. Cellulose 25, 6191-6205 (2018). Recovered from link.springer.com.
- Guan, Y. et al. (2020). Colloidal ZnCO3 as a Powerful Depressant of Arsenopyrite in Weakly Alkaline Pulp and the Interaction Mechanism. Minerals 2020, 10, 315. Recovered from mdpi.com.
- Diseases of the Skin, Eye, Conjunctiva, and External Ear. (2017). In Veterinary Medicine (Eleventh Edition). Recovered from sciencedirect.com.
- Hannig, M. and Hannig, C. (2013). Nanobiomaterials in Preventive Dentistry. In Nanobiomaterials in Clinical Dentistry. Chapter 8. Recovered from sciencedirect.com.
- Tugrul, N. et al. (2015). Synthesis of hydrophobic nanostructures zinc borate from zinc carbonate, and characterization of the product. Res Chem Intermed (2015) 41: 4395-4403. Recovered from link.springer.com.
- de Luna, MDG, et al. (2020). Recovery of zinc granules from synthetic electroplating wastewater using fluidized-bed homogeneous crystallization process. Int. J. Environ. Sci. Technol. 17, 129-142 (2020). Recovered from link.springer.com.