As we continuously strive to safeguard our environment, the search for efficient and sustainable solutions to diverse challenges remains paramount. One noteworthy solution is the utilization of hydrated lime within environmental treatment processes. Hydrated lime stands as an adaptable and eco-conscious material, providing a multitude of advantages to our natural world.

In this blog post, TLD Vietnam will give you the basic understanding of this mineral. Let’s get started!

What Is Hydrated Lime?

With the chemical formula Ca(OH)2 also known as calcium hydroxide, it is a powerful alkaline substance created when calcium oxide combines with water. An interesting aspect of this reaction is that it produces heat. The amount of water used during the process influences the final form of calcium hydroxide, which can range from a dry powder to a paste-like consistency, or a liquid suspension known as milk of lime or lime slurry.

The Physical Properties

Calcium hydroxide is a solid, white or slightly beige powder with a crystalline structure. Despite being slightly soluble in water, it’s also hygroscopic, meaning it actively draws moisture from the surrounding air. This can cause the powder to clump or cake over time. Calcium hydroxide is caustic, so it’s important to handle it carefully.

The Wide Range Of Uses Through Different Sectors

In history, hydrated lime, along with other lime-based products, boasts a long and rich history of agricultural and non-agricultural applications. While its use as a pesticide ingredient has largely been discontinued, its effectiveness in organic livestock production remains recognized. In this day and age, it is applied in various sectors. The lists are in the following section:

Water treatment

A significant application of this mineral lies in water treatment. It effectively adjusts water pH levels, counteracting acidity. Additionally, it removes impurities like heavy metals, fluoride, and organic pollutants. Being naturally alkaline, it acts as a powerful coagulating agent, helping to settle suspended particles in water. Water treatment facilities rely on hydrated lime to purify both drinking water and wastewater.

Steel manufacturing

Hydrated lime plays a vital role in several aspects of the steel industry. In plants where coke is a by-product, it neutralizes impurities. Steel plates are frequently given a hydrated lime coating, creating a short-term protective layer against oxygen-based corrosion.

Crucially, hydrated lime serves as a fluxing agent during the steel production process.  It reacts with silica and alumina impurities in iron ore, transforming them into slag. This slag floats on the molten iron, allowing for easy removal. Employing hydrated lime in steel production also leads to greater efficiency, reducing both energy and raw material consumption.

Chemical manufacturing

Hydrated lime serves as a fundamental factor in the manufacturing of numerous chemicals, including bromide, caustic soda, fluoride, magnesia, lactate, nitrate, oleate and stearate.  It’s also essential in the creation of various calcium salts, both organic and inorganic, such as calcium carbide, calcium hypochlorite, calcium magnesium acetate and calcium phosphate. Additionally, this kind of mineral contributes significantly to the purification process of citric acid.

Flue gas treatment

Hydrated lime acts as a catalyst in neutralizing harmful emissions from cement plants, coal-fired power plants, glass manufacturing facilities. Its anions readily capture acidic pollutants typically released into the atmosphere – like hydrogen fluoride, hydrogen chloride, sulfur dioxide, selenium and fine particulate matter. This reaction effectively converts these pollutants into calcium sulfate, a less harmful substance.

Sugar refining

Hydrated lime is essential to the production of sugar from both sugar cane and sugar beets. It is also used to purify sugar from other sources, such as maple or sorghum, although these are produced in much smaller quantities.

Sugar cane is harvested and processed with water to form raw cane juice, which has low pH and contains dissolved impurities. Hydrated lime is added to the juice to raise the pH and to react with the impurities to form insoluble calcium organic compounds that can be removed. Excess lime is removed by carbonation or by the addition of phosphoric acid. This process may be repeated several times depending on the purity of final product required.

Construction

Hydrated lime finds extensive use as a construction material due to its positive impact on workability and durability.  It’s commonly found in mortar and plaster, where it reacts with other ingredients to form calcium silicates and calcium aluminates. These compounds boost the mix’s strength and adhesion. Additionally, hydrated lime’s natural ability to inhibit mold and mildew growth makes it particularly valuable for construction in humid areas.

What Is The Difference Between Quicklime And Hydrated Lime?

Quicklime (calcium oxide, CaO) and hydrated lime (calcium hydroxide, Ca(OH)2) are closely related but differ in their chemical composition. This leads to variations in properties and uses:

• Chemical Formula: Quicklime (CaO) vs. Hydrated Lime (Ca(OH)2)
• Molar Mass: Quicklime (56.07 g/mol) is lighter than Hydrated Lime (74.09 g/mol)
• Melting/Boiling Points: Quicklime has significantly higher melting and boiling points (2,613°C and 2,850°C) compared to hydrated lime (which melts at 580°C and decomposes upon further heating)

Looking in more details about: Quicklime

The Chemical Risks That You Should Know

Unlike thermal burns caused by heat transfer, chemical burns involve a deeper process. They occur due to a direct reaction between the chemical and the body tissues it comes into contact with, such as skin, eyes, or mucous membranes. This reaction can be categorized as acid-base, oxidation-reduction (redox), or other chemical interactions. 

The 3-Step Process of Chemical Burn Formation:

• Contact: The chemical substance comes into direct contact with the body tissue.
• Diffusion: The chemical agent penetrates deeper into the tissue layers.
• Reaction: The chemical reacts with biological compounds within the affected tissue, causing damage.

The severity of a lime-related injury depends on factors like the type of lime, its concentration, temperature, and the duration of contact with the skin, eyes, or mucous membranes. Regardless of the specific form, lime is a hazardous substance due to its irritating and corrosive properties. Its widespread use increases the danger, with the potential for serious burns to the eyes, skin, and respiratory system. Exposure can occur through solid, dust, or solution forms of lime.

Contact with the eyes

Exposure of the eyes to quicklime or hydrated lime can lead to various consequences, ranging from mild irritation to severe chemical burns.  These burns can potentially cause permanent vision loss (blindness).  The powdery form of lime is particularly dangerous, as moisture in the eyes can worsen the reaction and increase the burn’s severity.

Skin contact

Lime exposure can cause burns that might not hurt right away, leading to serious injuries before you even realize there’s a problem. 

Conclusion

Hydrated lime is a remarkably versatile chemical with a wide range of uses across industries. It’s great for improving performance, making processes more efficient, and boosting sustainability.