Industrial Uses of Calcium Hydroxide (Slaked Lime)

Calcium hydroxide, Ca(OH)₂, is a versatile and cost-effective base with wide industrial applications. Below are key sectors and typical roles:

• Water & Sewage Treatment: Used as a strong, economical alkali for pH adjustment/neutralization of acidic waters (industrial or municipal). Acts as a coagulant aid/flocculant to precipitate dissolved impurities, some heavy metals, and phosphates.
• Construction (Mortar & Plaster): Essential in traditional lime mortars and plasters. Mixed with sand to form a workable paste that cures by reacting with atmospheric CO₂ (carbonation):

 Ca(OH)₂(s) + CO₂(g) → CaCO₃(s) + H₂O(l) The formed CaCO₃ imparts strength and durability.

• Agriculture (Soil pH Management): Applied to neutralize acidic soils (“sweetening”), improving nutrient availability and enhancing crop yields. Often used alongside ground limestone (CaCO₃) depending on soil requirements.
• Food Industry: Food-grade Ca(OH)₂ is used in nixtamalization of maize (improves nutrition, texture, and milling; e.g., tortillas). Also employed in sugar refining for juice clarification (under regulated conditions and standards).
• Pulp & Paper (Kraft Process): Vital in causticizing to regenerate NaOH from sodium carbonate in the chemical recovery cycle: Ca(OH)₂(aq) + Na₂CO₃(aq) → 2 NaOH(aq) + CaCO₃(s) The precipitated CaCO₃ (lime mud) is typically reburned to CaO and recycled.
• Leather Tanning: Used in liming to swell hides and aid in hair removal during early tanning operations.
• Flue-Gas Treatment: Employed to scrub acidic gases (e.g., SO₂) in emissions control systems, reducing air pollutants.
• Soil Stabilization (Civil Engineering): Added to clays and subgrades to improve bearing strength, reduce plasticity, and enhance workability for roads and foundations.

Note: Application grades and purity specifications vary by industry (e.g., technical vs. food grade). Follow relevant standards and safety guidelines.