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Calcium Hydroxide

Calcium hydroxide is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is obtained when calcium oxide is mixed or slaked with water. A suspension of Calcium hydroxide particles in water is called Milk of Lime; the particles give it the milky aspect

Synonyms
Calcium dihydroxide, Slaked lime, Hydrated lime, Lime, Milk of lime, E526
Chemical Formula
Ca(OH)2
CAS Number
1305-62-0

Characteristics

Molar Weight
74.093 g/mol
Melting Point
580 °C
Density
2.211 g/cm³ (solid)
Forms
Powder, Liquid, White, Colourless

Uses and Applications

Key applications

  • Beverage processing
  • Food and Nutrition
  • Wastewater treatment
  • Water treatment
  • Oil and Gas
  • Pulp and paper
  • Building & Construction products

Calcium hydroxide

Calcium hydroxide is the hydroxide of calcium. It is also known by names such as slaked lime and hydrated lime. In nature, the substance is relatively rare and referred to as the mineral ‘portlandite’. Due to the high demand in various industries, it is produced synthetically.

Properties of calcium hydroxide

Calcium hydroxide is a colourless and odourless solid that exists as a powder. It dissolves poorly in water. Calcium hydroxide is not soluble in ethanol. It decomposes at 580 degrees Celsius, producing calcium oxide and water.
Calcium hydroxide is produced industrially by the exothermic reaction of calcium oxide with water. This process is also known as lime slaking.
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Calcium hydroxide in the construction industry

Calcium hydroxide is used in a variety of ways in the construction industry. Due to its breathable and moisture-regulating properties, the substance is an essential component of lime mortar and lime plaster. Lime mortar enables flexible and durable bonding of building blocks and at the same time provides protection against moisture. Lime paint also protects the wall from moisture.
Calcium hydroxide is also used in the construction industry to improve the load-bearing capacity of building ground, as it binds water. Calcium hydroxide is also required for the production of sand-lime bricks, which are widely used as a building material.
In water treatment on construction sites, calcium hydroxide is used to regulate the pH level and remove pollutants.

Calcium hydroxide in agriculture

One of the most common applications of calcium hydroxide in agriculture is soil improvement. It is used to neutralise acidic soils and increase the pH value, thereby optimising soil quality.
Calcium hydroxide is used in plant care to combat certain fungal diseases. It is also used as a disinfectant in animal stables, barns and other agricultural buildings. In certain cases, calcium hydroxide is also used as an additive in animal feed.
In composting, calcium hydroxide is used to regulate the pH level ft he compost heap. It helps to accelerate the decomposition process and reduce unpleasant odours.

Calcium hydroxide in the chemical industry

Calcium hydroxide is widely used in the chemical industry, primarily due to its reactive and pH-regulating properties.
It is used to neutralise acidic waste water and industrial waste gases: Calcium hydroxide increases the pH value and neutralises harmful acids in waste water treatment and flue gas desulphurisation.
It also supports the precipitation of phosphates from wastewater and thus prevents eutrophication (nutrient enrichment). The removal of hardness formers such as calcium and magnesium ions is another task of calcium hydroxide in water treatment. This reduces water hardness and prevents deposits in pipes and appliances.
In water treatment and chemical processes, calcium hydroxide also serves as a precipitant to remove dissolved metals and impurities. It helps to convert these substances into a solid form so that they can be filtered more easily.
Calcium hydroxide is also required as a starting material in the production of various chemicals such as calcium stearate (a lubricant) and calcium chloride (for dehumidification and de-icing salt products). Last but not least, lime water is used in the chemical industry as a clear liquid for detecting carbon dioxide.

Calcium hydroxide in the oil and gas industry

Calcium hydroxide regulates the pH value in drilling fluids in order to protect the metal parts of the drilling equipment from corrosion and to stabilise the drilling fluid.
It also neutralises acid gases such as hydrogen sulphide and carbon dioxide, which can be released during oil production and processing. Calcium hydroxide is also used to purify waste water in refineries.

Calcium hydroxide in mining

In mining, calcium hydroxide is used to neutralise acid mine water (sulphate solutions) produced during mineral extraction.
In the so-called cyanide leaching process in gold extraction, calcium hydroxide is used to keep the pH value stable and thus increase the yield of gold.

Calcium hydroxide in the paper industry

In the paper industry, calcium hydroxide is used in various production steps, for example in the manufacture of precipitated calcium carbonate (PCC), a frequently used filler. PCC improves the smoothness, brightness and printability of the paper.
Calcium hydroxide is also used in the so-called Kraft pulping process to remove lignin and other undesirable components from wood.

Other areas of application for calcium hydroxide

In the polymer industry, calcium hydroxide is used as a stabiliser in the production of polyvinyl chloride (PVC).
In the rubber and caoutchouc industry, calcium hydroxide is used as an additive in the vulcanisation of synthetic rubbers such as chloroprene rubber (neoprene), which supports the cross-linking of the polymer chains and makes the material more resistant and elastic. As a filler, calcium hydroxide optimises mechanical properties such as the strength and resistance of rubber.
Calcium hydroxide is also used to neutralise acidic by-products during the manufacture of certain polymers and rubber products.
In the food industry, calcium hydroxide is added to food as an acidity regulator and is authorised in the EU as a food additive with the designation E 526. It carries no maximum quantity restriction.
In the cosmetics industry, calcium hydroxide is used as an active ingredient in hair removal products. It softens the proteins (keratin) in the hair and thus facilitates their removal. It is also used as a pH buffer to regulate the acidity of cosmetic formulations such as creams and lotions. Calcium hydroxide is used in scrubs and masks to remove dead skin cells and smooth the skin.
In the lubricant industry, calcium hydroxide is mainly used to produce calcium soaps, which are used as thickeners in lubricating greases. Calcium soaps increase the viscosity of greases and ensure that they remain stable under various conditions and do not lose their lubricating properties.
In the cleaning industry, calcium hydroxide is used to regulate the pH of cleaning agents. A higher pH value improves their effectiveness in removing grease, oil and dirt.
In dentistry, calcium hydroxide is mainly used to disinfect root canals. It is also added to certain antacids to neutralise excess stomach acid.