What are the uses of hydrated lime?

Answer 1

Hydrated lime or slaked lime is calcium hydroxide (Ca(OH)2)

Calcium hydroxide is commonly used to prepare lime mortar.

One significant application of calcium hydroxide is as a flocculant, in water and sewage treatment. It forms a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product. This application is enabled by the low cost and low toxicity of calcium hydroxide. It is also used in fresh-water treatment for raising the pH of the water so that pipes will not corrode where the base water is acidic, because it is self-regulating and does not raise the pH too much.

It is also used in the preparation of ammonia gas (NH3), using the following reaction:

Ca(OH)2 + 2 NH4Cl → 2 NH3 + CaCl2 + 2 H2O

Another large application is in the paper industry, where it is an intermediate in the reaction in the production of sodium hydroxide. This conversion is part of the causticizing step in the Kraft process for making pulp.[8] In the causticizing operation, burned lime is added to green liquor, which is a solution primarily of sodium carbonate and sodium sulfate produced by dissolving smelt, which is the molten form of these chemicals from the recovery furnace.

Food industry

Because of its low toxicity and the mildness of its basic properties, slaked lime is widely used in the food industry:

In USDA certified food production in plants and livestock[10]

To clarify raw juice from sugarcane or sugar beets in the sugar industry, (see carbonatation)

To process water for Alcoholic Beverages and soft drinks

Pickle cucumbers and other foods

To make Chinese century eggs

In maize preparation: removes the cellulose hull of maize kernels (see nixtamalization)

To clear a brine of carbonates of calcium and magnesium in the manufacture of salt for food and pharmaceutical uses

In fortifying (Ca supplement) fruit drinks, such as Orange Juice, and infant formula

As a digestive aid (called Choona, used in India in paan, a mixture of areca nuts, calcium hydroxide and a variety of seeds wrapped in betel leaves)

As a substitute for baking soda in making papadam

In the removal of carbon dioxide from controlled atmosphere produce storage rooms

Native American uses

Dry untreated maize (left), and treated maize (right) after boiling in water with calcium hydroxide (15 ml, or 1 tbsp, lime for 500 g of corn) for 15 minutes

In Spanish, calcium hydroxide is called cal. Maize cooked with cal (in a process of nixtamalization) becomes hominy (nixtamal), which significantly increases the bioavailability of niacin (vitamin B3), and is also considered tastier and easier to digest.

In chewing coca leaves, calcium hydroxide is usually chewed alongside to keep the alkaloid stimulants chemically available for absorption by the body. Similarly, Native Americans traditionally chewed tobacco leaves with calcium hydroxide derived from burnt mollusc shells to enhance the effects. It has also been used by some indigenous American tribes as an ingredient in yopo, a psychedelic snuff prepared from the beans of some Anadenanthera species.[11]

Asian uses

Calcium hydroxide is typically added to a bundle of areca nut and betel leaf called "paan" to keep the alkaloid stimulants chemically available to enter the bloodstream via sublingual absorption.

It is used in making naswar (also known as nass or niswar), a type of dipping tobacco made from fresh tobacco leaves, calcium hydroxide (chuna or soon), and wood ash. It is consumed most in the Pathan diaspora, Afghanistan, Pakistan, India and Bangladesh. Villagers also use calcium hydroxide to paint their mud houses in Afghanistan, Pakistan and India.

Answer 2

Hydrated lime is commonly used in construction as a component in mortar and plaster. It is also used in agriculture to adjust soil pH and improve crop growth. Additionally, hydrated lime is utilized in water and wastewater treatment processes for its alkalinity and ability to remove impurities.