Boric acid is a weak, naturally occurring acid that has a variety of industrial and household applications. Some of the most common uses of boric acid include as an insecticide, preservative, antiseptic, and flame retardant. But where exactly does this versatile compound come from? There are a few different natural sources of boric acid that are mined and processed to produce the refined boric acid used commercially.
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Natural Sources of Boric Acid
Boron Ore Deposits
The most common natural source of boric acid is from boron ore deposits located in arid regions of Turkey, the United States, Argentina, and China. Boron is a metalloid element that is found in combination with other elements like sodium, magnesium, and calcium in boron ores. The most abundant boron minerals are borax, kernite, ulexite, and colemanite.
To extract pure boric acid from boron ores, the crude ore is first mined from deposits underground. The boron minerals are then refined through a process of dissolution, filtration, and recrystallization to isolate the boric acid. For example, kernite ore is crushed and treated with hot water to dissolve the boric acid. The solution is filtered, cooled, and allowed to crystallize to produce boric acid crystals that are then dried.
Geothermal Steam
Geothermal steam from volcanic areas or hot springs is another natural source of boric acid. As the steam rises through the earth, it picks up trace amounts of boron commonly found in volcanic rock and soils. When the steam condenses, the boric acid can be extracted.
For example, boric acid is collected from the geothermal steam vents at the Larderello geothermal field in Italy. The steam is channeled through condensers, and the resulting condensate water is processed to extract minerals like borates and silica. The borates are then converted into boric acid through reactions with sulfuric acid.
Seawater
Boric acid also occurs naturally in very small concentrations in seawater. Seawater contains an average of around 5 mg/L of boron. Advanced technologies like ion exchange resins can now extract and concentrate the boron content of seawater to produce boric acid. However, this is not yet a commercially viable source, since the concentrations are so low. It may become an economically important source in the future as extraction technologies continue to improve.
Industrial Production
Refinement of Boron Ores
Currently, the vast majority of boric acid is industrially produced from the refinement of boron ores. Turkey and the United States are the leading producers and exporters of refined boric acid worldwide.
The processing of boron ores like colemanite and ulexite into boric acid involves several chemical steps. First the ores are mined, crushed, and dissolved in hot water. Next, the water is treated with calcium chloride which causes calcium borate to precipitate out. The precipitate is then treated with sulfuric acid to produce boric acid crystals, which are filtered, dried and packaged.
| Country | Boric Acid Production (tons) |
|---|---|
| Turkey | 790,000 |
| United States | 650,000 |
| Argentina | 230,000 |
| Russia | 100,000 |
| China | 92,000 |
| Bolivia | 66,000 |
| Peru | 48,000 |
Chemical Synthesis
A small portion of the world’s boric acid is also produced through chemical synthesis methods rather than refinement of natural ores. The most common industrial method combines borax (sodium tetraborate) with sulfuric acid to produce boric acid and sodium sulfate as byproducts:
Na2B4O7 + H2SO4 –> 2H3BO3 + Na2SO4
The reaction is carried out in reactors and the boric acid product is then crystallized, centrifuged, and dried. This method helps supplement boric acid production in regions without significant boron ore deposits.
Laboratory Preparation
While industrial production generates nearly all the world’s boric acid, small quantities can also be synthesized in the laboratory for research purposes. Some common methods include:
– Treating borax with a mineral acid like hydrochloric acid to extract the boric acid.
– Dehydrating boric acid solutions to crystallize pure boric acid.
– Combusting boron oxide with glycerol and water to produce boric acid.
– Electrolyzing boron trifluoride in water to form tetrafluoroboric acid, and then neutralizing with sodium hydroxide to precipitate boric acid.
Though laboratory methods do not produce commercial scales of boric acid, they are important for understanding the chemical properties and reactivity of this versatile compound.
Uses of Boric Acid
Industrial Uses
– Preservative and anti-bacterial agent in wood, paper, textiles and leather
– Flame retardant additive in cellulose insulation, cotton, rayon and other materials
– Starting material to produce other boron compounds and derivatives
– Component of enamel glazes and specialty glasses like Pyrex
– Lubricating fluids and greases for high temperature applications
Pest Control
– Most common use is as an insecticide, particularly against ants, fleas, termites and other household pests
– Often used in baits, powders, gels and solutions for infestations
– Low toxicity to humans and pets but deadly to insects when ingested
Household Uses
– Cleaning agent to dissolve soap scum, calcium deposits, algae, and molds
– Preserving agent for taxidermy specimens
– Neutralizing smelly feet, drains, garbage bins, etc. due to antibacterial properties
Personal Care
– Antiseptic eyewash solution
– Topical acne treatment due to antibacterial and exfoliant properties
– Soothing, cleansing foot soaks
Other Minor Uses
– pH buffer in swimming pools
– Nuclear power plant shielding
– Gold extraction from ores
– Fiberglass production
Conclusion
In summary, boric acid is a naturally occurring compound, primarily obtained by refining boron ores like colemanite, ulexite and kernite. The leading global producers are Turkey and the United States. Minor sources include geothermal steam and seawater. In industry and households, boric acid has a wide array of applications from flame retardant to pesticide to cleaning agent, due to its diverse chemical properties. While most boric acid today is refined from mined ore deposits, future advances in seawater extraction technologies could provide a supplemental source of this useful compound.