Milk of Lime
What is Milk of Lime?
Milk of lime, also known as lime milk or lime slurry, is a suspension of calcium hydroxide (Ca(OH)2) particles in water. These particles give the solution its characteristic milky appearance.
It is produced through the process of lime slaking, where calcium oxide (quicklime) reacts with water, resulting in a highly alkaline material. Milk of lime is manufactured industrially in stirred reactor vessels, either from quicklime or from hydrated lime, in the presence of excess water.
Properties of milk of lime:
- Appearance: White milky appearance
- Chemical Formula: Ca(OH)2
- pH: Highly alkaline, with a pH of approximately 12.5 at 25°C (77°F)
- Density: Around 2.3-2.4 g/cm3 (Boynton)
- Solubility: Reacts with water to form calcium hydroxide (slaked lime), which has a solubility of 1.33 g CaO/L at 10°C (Boynton)
Applications of milk of lime:
Milk of lime is widely used in various industrial applications.
- Water and wastewater treatment: Utilized for adjusting pH levels, removing contaminants, and softening water.
- Civil engineering: Used for stabilizing and modifying soil, especially in clay-rich areas.
- Flue gas treatment: Serves as a ‘washing liquid’ to reduce pollutants from flue gases.
- Agriculture: Neutralizes acidic soils resulting in improved crop yield and enhanced soil health.
- Food production: Helps purify raw sugar juice in sugar refining.
- Specialty applications: Serves as a primary supplement of calcium and alkalinity in reef aquariums, as a fresh plaster in some specific fresco painting techniques, as a color solvent, and in the preparation of maize-based food like corn tortillas.
Frequently Asked Questions (FAQs)
How is milk of lime produced, and what chemical reaction is involved?
Milk of lime is produced through the lime slaking process, where calcium oxide (quicklime) reacts with water. The reaction forms calcium hydroxide (Ca(OH)2), which is suspended in water to create the characteristic milky solution.
What are the primary physical and chemical properties of milk of lime?
Milk of lime has a white, milky appearance, a highly alkaline pH of around 12.5 at 25°C (77°F), and is composed of calcium hydroxide (Ca(OH)2).
How does milk of lime benefit water and wastewater treatment?
In water and wastewater treatment, milk of lime adjusts pH levels, removes contaminants such as heavy metals, and softens it by precipitating excess of magnesium and calcium.
What role does milk of lime play in civil engineering?
In civil engineering, milk of lime is used for soil stabilization and modification, particularly in dry clay-rich areas. It improves soil strength and reduces its plasticity, making it suitable for construction projects.
How is milk of lime utilized in flue gas treatment?
Milk of lime acts as a washing liquid in flue gas treatment, neutralizing acidic pollutants like sulfur dioxide (SO2) and removing other contaminants from industrial emissions, thus reducing environmental pollution.
What agricultural benefits does milk of lime provide?
Milk of lime neutralizes acidic soils, improving their pH balance. This enhances crop yield, boosts soil health, and provides essential calcium for plants which is beneficial for agriculture.