Calcium oxide

Calcium oxide (CAS 1305-78-8), commonly known as quicklime and approved as food additive E529, is a high-reactivity alkaline material produced by calcining limestone at high temperatures.

Where is Calcium oxide used?

• Water and wastewater treatment: raises pH and precipitates heavy metals
• In water treatment, it forms calcium hydroxide to raise pH and assist lime softening, removing hardness, heavy metals, and impurities.
• Steel and non-ferrous metals: flux that removes impurities during smelting and refining
• Used in the production of copper, zinc, lead, silver, nickel, gold, and uranium to separate impurities by flotation of the different metal salts.
• Pulp and paper: regenerates sodium hydroxide in the kraft recovery cycle
• Construction: primary input for hydrated lime used in mortars, soil stabilization and asphalt modification
• It also acts as a pH regulator, desiccant and reactive base in industrial processes.
• Used in flue gas desulfurization to remove sulfur dioxide from exhaust streams.
• Neutralizes soil acidity.

Formulation notes

• In steelmaking, 30 to 50 kg per tonne of steel is used.
• Incompatible with cellulose-based absorbents.

Typical specification

• The term high-calcium quicklime refers to a product that contains a maximum of 5% magnesium oxide.
• Available in particle sizes of 0-3 mm.
• Has a neutralizing value or calcium carbonate equivalent (CCE) of 179% compared to 100% for calcium carbonate.
• Assay is not less than 95.0%.

Regulatory status

• Classified under UN GHS for transport as UN Hazard Class 8, Packing Group III.
• The EU occupational exposure limit (EU-OEL) is 1 mg/m³ as TWA and 4 mg/m³ as STEL.
• Registered under the REACH Regulation and produced and/or imported in the European Economic Area at ≥ 10,000,000 tonnes per year.
• Approved for use as a biocide in the EEA and/or Switzerland for disinfection and veterinary hygiene.

Storage, packaging and handling

• Reacts with water, generating enough heat to ignite combustible materials.
• When exposed to moisture and carbon dioxide in the air, it reacts to gradually form a mixture of calcium hydroxide and calcium carbonate.
• Must be stored separately from strong acids, organic chemicals, water, and food and feedstuffs, in a dry place.
• Commonly supplied in big bags.

Frequently asked questions about Calcium oxide

In which applications does calcium oxide react in a sealed system to generate expansion?

It is used in rock breaking and demolition by expanding when hydrated in a sealed cartridge to fracture rock.

How is calcium oxide used in sugar refining?

In sugar refining, it is added to raw sugar juice to remove impurities, then carbon dioxide precipitates excess calcium as calcium carbonate.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.