- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting point
- Boiling point
- Density
- Solubility
- pH
- Chemical properties
- Obtaining
- Applications
- In the absorption of CO
- In the removal of H
- In chemistry laboratories
- In the cleaning products industry
- In the food industry
- In fertilizers
- In various applications
- References
The potassium carbonate is an inorganic compound consisting of two potassium ions K + and a carbonate ion CO 3 2-. Its chemical formula is K 2 CO 3. It is a hygroscopic white solid, that is, it easily absorbs water from the environment. For this reason, in laboratories it is used to absorb water from other substances.
It is very soluble in water, forming alkaline solutions, which are rich in OH ions - and therefore with a high pH value. Its aqueous solutions, being alkaline, are used in various industrial processes to absorb acid gases such as carbon dioxide CO 2 and hydrogen sulfide H 2 S, as it easily neutralizes them.
Solid potassium carbonate K 2 CO 3. Ondřej Mangl. Source: Wikimedia Commons.
K 2 CO 3 is used to prepare soaps, cleaning products, laundry detergents and dishwashing mixes. It is also used in the processing of some textile fibers such as wool.
It is widely used in chemistry laboratories, for example to absorb water from other compounds or to alkalize mixtures of chemical reactions and also in chemical analysis.
It is also added to some foods, for example, to eliminate the bitter taste of cocoa beans during the production of chocolate.
Structure
Potassium carbonate is made up of two K + potassium cations and a CO 3 2- carbonate anion. The carbonate anion has a flat and symmetric structure, while the three oxygen atoms surround the carbon forming a flat triangle.
Structure of potassium carbonate K 2 CO 3. User: Edgar181. Source: Wikimedia Commons.
Nomenclature
- Potassium carbonate
- Potassium carbonate
- Dipotassium carbonate
- Potash
- Potassium salt of carbonic acid.
Properties
Physical state
Colorless to white crystalline solid.
Molecular weight
138.205 g / mol.
Melting point
899 ° C.
Boiling point
It decomposes.
Density
2.29 g / cm 3
Solubility
Very soluble in water: 111 g / 100 g of water at 25 ° C. Insoluble in ethanol and acetone.
pH
An aqueous solution can have a pH of 11.6, that is, it is quite alkaline.
Chemical properties
Potassium carbonate is deliquescent or hygroscopic, that is, it absorbs moisture from the environment. It has a stable hydrate, K 2 CO 3.2H 2 O.
K 2 CO 3 in aqueous solution hydrolyzes, that is, it reacts with water, releasing OH groups - which are what give solutions alkalinity:
CO 3 2- + H 2 O ⇔ OH - + HCO 3 -
HCO 3 - + H 2 O ⇔ OH - + H 2 CO 3
Obtaining
It can be obtained from the ashes that remain from burning plants. Also by carbonation of potassium hydroxide KOH, that is, adding excess carbon dioxide CO 2 to KOH:
KOH + CO 2 → KHCO 3
2 KHCO 3 + heat → K 2 CO 3 + H 2 O
Another way to obtain it is by heating the potassium chloride KCl with magnesium carbonate MgCO 3, water and CO 2 under pressure. A hydrated double salt of magnesium and potassium MgCO 3.KHCO 3.4H 2 O is first obtained, called Engels's salt:
2 KCl + 3 MgCO 3 + CO 2 + 5 H 2 O → MgCO 3.KHCO 3.4H 2 O ↓ + MgCl 2
Engels' hydrated double salt precipitates and is filtered out of solution. Then it is heated and the potassium carbonate K 2 CO 3 is formed, which dissolves when adding water while the magnesium carbonate MgCO 3 remains insoluble and is removed by filtration.
MgCO 3.KHCO 3.4H 2 O + heat → MgCO 3 ↓ + 2 K + + CO 3 2- + CO 2 ↑ + 9 H 2 O
Applications
In the absorption of CO
Potassium carbonate solution is the classic treatment for the removal of carbon dioxide CO 2 in various processes, especially in high pressure and temperature applications.
K 2 CO 3 solutions are used to absorb CO 2 in various industrial processes. Author: Nicola Giordano. Source: Pixabay.
The removal of CO 2 occurs according to the following reaction:
K 2 CO 3 + CO 2 + H 2 O ⇔ 2 KHCO 3
This method is used for example to treat natural gas. Also in power generation plants, to avoid the emission of CO 2 into the atmosphere, and in the production of dry ice.
K 2 CO 3 solutions are used to obtain CO 2 that is used to make dry ice. ProjectManhattan. Source: Wikimedia Commons.
The K 2 CO 3 solution can be regenerated thermally, that is, by heating to temperatures around 100 ° C.
So that the potassium carbonate solution can absorb the CO2 at a good speed, promoters are added that speed up the process such as diethanolamine (DEA).
In the removal of H
Potassium carbonate solutions are also used to remove H 2 S hydrogen sulfide gas from process streams. Sometimes potassium triphosphate K 3 PO 4 is added to speed up the process.
In chemistry laboratories
K 2 CO 3 makes it possible to carry out organic syntheses, for example, in condensation reactions and to neutralize. It is used to remove water from organic liquids, as a dehydrating agent or desiccant in the laboratory.
It is also used in analytical chemistry reactions and for alkalization in the pharmaceutical industry.
In the cleaning products industry
K 2 CO 3 is used to make soap, cleaning formulas, laundry and dishwashing products, and also to prepare shampoo and other personal care products.
K 2 CO 3 is used in the preparation of soap. Lacrimosus. Source: Wikimedia Commons.
In the food industry
Potassium carbonate is added to various foods for various purposes.
For example, it is added to cocoa beans to remove their bitter taste and use them in the production of chocolate. It is added to the grapes in the drying process to obtain raisins.
The cocoa beans are treated with K 2 CO 3 to decrease their bitter taste when making chocolate. Author: Magali COURET. Source: Pixabay.
In pastry it is used as a leavening agent (which acts as a yeast) for flour to prepare baked goods.
K 2 CO 3 can be used as a leavening agent in cakes, as they release CO 2 during cooking and increase their volume. Author: Pixel1. Source: Pixabay.com
In fertilizers
K 2 CO 3 is used to fertilize acidic soils, since the carbonate ion CO 3 2- in contact with water produces OH - ions that increase the pH of the soil. In addition, potassium K + is a nutrient for plants.
Potassium carbonate has also been used to make slow-release fertilizers.
A slow-release fertilizer slowly releases or releases nutrients so that they are not dissolved and washed away by the water. Thanks to this, they will be able to spend more time available to the roots of the plant.
In various applications
Potassium carbonate K 2 CO 3 is also used to:
- Raw wool dyeing, bleaching and cleaning processes and other activities of the textile industry
- Obtaining other organic and inorganic potassium salts, such as KCN potassium cyanide.
- To function as a regulator of acidity in various processes.
- Manufacture ceramics and pottery.
- Engraving and lithography processes.
- Tanning and finishing of leathers.
- Prepare inks for printing, pigments.
- Manufacture glasses especially for television, since K 2 CO 3 is more compatible than sodium carbonate Na 2 CO 3 with the oxides of lead, barium and strontium that these glasses contain.
- Water treatment.
- Retarding the fire (in the form of aqueous solutions).
- Inhibit corrosion and as an antifouling agent in process equipment.
References
- US National Library of Medicine. (2019). Potassium carbonate. Recovered from pubchem.ncbi.nlm.nih.gov.
- Steele, D. (1966). The Chemistry of the Metallic Elements. Pergamon Press Ltd. London.
- Mokhatab, S. et al. (2019). Natural Gas Treating. The Potassium Carbonate Solution. In Handbook of Natural Gas Transmission and Processing (Fourth Edition). Recovered from sciencedirect.com.
- Kakaras, E. et al. (2012). Pressurized fluidized bed combustion (PFBC) combined cycle systems. Pressurized fluidized bed combustion with carbon capture and storage. In Combined Cycle Systems for Near-Zero Emission Power Generation. Recovered from sciencedirect.com.
- Speight, JG (2019). Hydrogen Production. Wet Scrubbing. In Heavy Oil Recovery and Upgrading. Recovered from sciencedirect.com.
- Branan, CR (2005). Gas treating: Chapter updated by Chris Higman. Hot Carbonate Processes. In Rules of Thumb for Chemical Engineers (Fourth Edition). Recovered from sciencedirect.com.
- Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Fourth Edition. John Wiley & Sons.
- Ullmann's Encyclopedia of Industrial Chemistry. (1990). Fifth Edition. VCH Verlagsgesellschaft mbH.
- Li, Y. and Cheng, F. (2016). Synthesis of a novel slow-release potassium fertilizer from modified Pidgeon magnesium slag by potassium carbonate. J Air Waste Manag Assoc, 2016 Aug; 66 (8): 758-67. Recovered from ncbi.nlm.nih.gov.