Calcium Oxide

Calcium Oxide, also known as quicklime, has been used since the dawn of civilization in construction as plasters and mortars.  As an inexpensive commodity, it is used in a variety of industries, including water treatment, glass manufacturing, soil treatment, and the production of cement and mortar, steel, paper, and sugar.

Since ancient times, Calcium Oxide has been produced by heating limestone (Calcium Carbonate, CaCO3) to temperatures around 900° Celsius.  This releases carbon dioxide (CO2) gas, leaving quicklime (Calcium Oxide, CaO).  This is called calcination.  Over time, exposure to air will convert the Calcium Oxide back into Calcium Carbonate unless it is slaked with water.  Slaked lime (Calcium Hydroxide Ca(OH)2) is basic, or alkaline.  Both quicklime and slaked lime are essential to a variety of industries.

Slaked lime is widely used across various industries due to its chemical properties. In the paper industry, it plays a key role in the kraft pulping process, where it helps regenerate caustic soda in a cyclic reaction involving sodium carbonate and quicklime. In water and wastewater treatment, slaked lime adjusts pH levels, precipitates out harmful ions, and aids in flocculation to remove suspended solids. It also prevents bacterial growth. In sugar refining, it reduces acidity, causing impurities to coagulate or precipitate, which improves the sugar’s clarity and shelf life. In glass manufacturing, quicklime (Calcium Oxide) stabilizes soda-lime-silica glass by replacing sodium ions with Calcium, increasing the glass’s strength and softening temperature. The steel industry uses lime in both electric arc and basic oxygen furnaces to remove impurities like sulfur, silica, and phosphorus, forming slag that can be separated from molten metal. Finally, lime enhances soil in construction by stabilizing and strengthening the foundation, and in agriculture, it neutralizes acidic soils, improves nutrient absorption, and provides essential Calcium.

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