Calcium chloride (CaClâ‚‚), a salt, consists of one calcium ion and two chloride ions. At room temperature, it is a white crystalline solid. It is highly soluble in water, releasing heat as it dissolves (exothermic). It is also hygroscopic and deliquescent, readily absorbing moisture from the air and dissolving into a liquid brine.
Natural Sources and Geological Deposits
Calcium chloride occurs naturally in various geological formations, often as a dissolved salt in subterranean water sources. Deep well brines represent a significant natural reservoir, where calcium chloride is present in higher concentrations compared to typical seawater. These brines are primary raw materials for commercial extraction. Ancient sea beds, evaporated over geological timescales, also contain calcium chloride as mineral deposits. While present in seawater, its concentration is lower than in brines, making brines a more economically viable source.
Manufacturing and Industrial Byproducts
Calcium chloride is produced through several industrial processes, often as a byproduct. One significant source is the Solvay process, primarily used for soda ash (sodium carbonate) production. In this process, it is generated from ammonium chloride and quicklime, making it a co-product of soda ash synthesis. Another method involves neutralizing hydrochloric acid with limestone (calcium carbonate), producing calcium chloride, carbon dioxide, and water. It is also recovered from natural brines.
Diverse Commercial and Industrial Applications
Calcium chloride finds extensive use across numerous industries due to its unique chemical properties. Its ability to depress water’s freezing point makes it widely employed for de-icing roads and sidewalks, melting ice and preventing its formation even at very low temperatures. As a de-icing agent, it also releases heat upon dissolution, enhancing its melting capability.
It serves as an effective dust control agent on unpaved roads, drawing moisture from the air to keep surfaces damp. This moisture helps bind fine gravel particles together, creating a more stable and compact road surface and reducing airborne dust. It is also a desiccant, absorbing moisture in industrial processes and packaging to prevent humidity-related damage.
In the oil and gas industry, calcium chloride is incorporated into drilling fluids to control density and stabilize shale formations. It prevents wellbore collapse by inhibiting water-sensitive clay swelling and lowers drilling fluid freezing points in cold environments. As an accelerator in concrete, it speeds up cement hydration, allowing faster setting times and improved early strength, especially in colder weather.
It is also used in wastewater treatment, aiding in the removal of contaminants such as phosphates, fluorides, and heavy metals. It functions as a coagulant or precipitant, causing impurities to clump together and settle out of the water. This helps produce clearer water and improves filtration efficiency.
Presence in Consumer Products and the Environment
Calcium chloride is found in various consumer products. In the food industry, it acts as a firming agent, maintaining the texture of canned vegetables and aiding curd formation in cheese. It is also found as an electrolyte in sports drinks, helping to replenish minerals.
Beyond food, it is the active ingredient in many household moisture absorbers, reducing humidity in enclosed spaces. In medical applications, injectable forms treat conditions such as hypocalcemia (low calcium levels), certain cardiac issues, or electrolyte imbalances.
After widespread industrial use, particularly in de-icing, calcium chloride enters the environment. Runoff from roads treated with calcium chloride contributes to its presence in local water bodies and soil. While generally acceptable in typical concentrations, its accumulation can impact local ecosystems by increasing freshwater salinity.