Bromine (Br) belongs to the halogen group of elements, alongside chlorine, fluorine, and iodine.
Image Credit: Jade ThaiCatwalk/Shutterstock.com
Background
Bromine was first identified as a chemical element in 1826 by French chemist Antoine Balard. He isolated it from chlorine and found that, in its elemental form, bromine is a highly volatile, reddish-brown liquid at room temperature.
Bromine does not naturally exist in its elemental form. Instead, it is found in compounds known as bromides, which are used as raw materials for commercial brominated products.
Bromine is commonly found in nature as bromide salts or organobromine compounds produced by various marine organisms. The most accessible sources of bromine are soluble salts found in seawater, salt lakes, inland seas, and brine wells. While seawater contains bromine at a concentration of approximately 65 parts per million (ppm), inland seas and brine wells have significantly higher concentrations, ranging from 2,500 to 10,000 ppm.
The world's primary bromine production sites include Israel, Jordan, China, and the United States, which extract bromine primarily from salt brines. The Dead Sea remains a major source of bromine due to its high concentration of bromide salts. Additionally, bromine is present in rock formations and the Earth's crust, further contributing to its availability.
Applications of Bromine
Water Purification
Bromine is widely used as a disinfectant and water purifier, often chosen as an alternative to chlorine. Brominated compounds are commonly added to swimming pools and hot tubs, where they remain effective even at high temperatures, unlike chlorine.
Bromine dissociates in water to form hypobromous acid (HBrO), which has powerful disinfectant properties that neutralize bacteria, algae, and viruses such as poliovirus and rotaviruses.
Beyond recreational uses, bromine is critical in industrial water treatment for applications like cooling systems in power plants, brewery pasteurizers, and pulp and paper mills. These systems rely on brominated solutions to maintain efficiency, eliminate odors, and reduce microbial buildup.
Agriculture
Bromine compounds are essential in agriculture as pesticides and soil fumigants. For example, methyl bromide has been used to control soilborne pests in fruit farming and to meet international quarantine standards for exported produce. Although its use has declined due to environmental concerns, bromine remains vital in synthesizing agrochemicals like herbicides and fungicides. These applications help protect crops from diseases and pests while improving yields.
Automotive Industry
Historically, bromine was used in leaded gasoline to prevent engine knocking; however, this application has been phased out with the adoption of unleaded fuel. Today, bromine's role in the automotive sector is more advanced. Zinc–bromine flow batteries are being developed for large-scale energy storage due to their high energy density and long lifespan. These batteries are particularly promising for stabilizing renewable energy grids and supporting electric vehicle infrastructure.
Healthcare
While bromine-based sedatives have largely been replaced by safer alternatives, bromine derivatives remain indispensable in modern medicine. They are used in antiseptics, antibacterial drugs, and the synthesis of pharmaceuticals targeting cancer and neurological disorders. For instance, brominated compounds serve as intermediates in producing certain chemotherapy drugs and treatments for epilepsy.
Photography
Bromine compounds have historically been integral to photography due to their role in creating light-sensitive silver halides used in photographic emulsions. These compounds enable film to capture images by reacting with light during exposure. Although digital photography has largely supplanted traditional methods, bromine-based emulsions are still used in specialized imaging fields such as X-ray films.
Flame Retardants
One of the largest applications of bromine is in brominated flame retardants (BFRs), which are highly effective at reducing flammability in materials like plastics, textiles, and electronics.
For instance, BFRs are commonly used in printed circuit boards, insulation foams, and back-coatings for upholstered furniture. Their thermal stability makes them suitable for engineering polymers exposed to high temperatures.
While environmental concerns have driven research into alternatives like phosphorus-based flame retardants, BFRs remain a cost-effective solution due to their recyclability and ability to maintain properties through multiple recycling cycles.