The bromate

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

, BrO, is a

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...

-based

oxoanion An oxyanion, or oxoanion, is an ion with the generic formula (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determine ...

. A bromate is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

that contains this ion. Examples of bromates include

sodium bromate Sodium bromate, the inorganic compound with the chemical formula of NaBrO3, is the sodium salt of bromic acid. It is a strong oxidant. Uses Sodium bromate is mainly used in continuous or batch dyeing processes involving sulfur or vat dyes and as ...

, (), and

potassium bromate Potassium bromate (KBrO3), is a bromate of potassium and takes the form of white crystals or powder. It is a strong oxidizing agent. It is a toxic and carcinogenic compound. Preparation Potassium bromate is produced when bromine is passed throug ...

, (). Bromates are formed many different ways in municipal drinking water. The most common is the reaction of

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

and

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant ...

: : Br + → BrO Electrochemical processes, such as electrolysis of brine without a membrane operating to form

hypochlorite In chemistry, hypochlorite is an anion with the chemical formula ClO−. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite (a component of ble ...

, will also produce bromate when bromide ion is present in the brine solution.

Photoactivation A photoswitch is a type of molecule that can change its structural geometry and chemical properties upon irradiation with electromagnetic radiation. Although often used interchangeably with the term molecular machine, a switch does not perform wor ...

(sunlight exposure) will encourage liquid or gaseous bromine to generate bromate in bromide-containing water. In laboratories bromates can be synthesized by dissolving in a concentrated solution of

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

(KOH). The following reactions will take place (via the intermediate creation of

hypobromite The hypobromite ion, also called alkaline bromine water, is BrO−. Bromine is in the +1 oxidation state. The Br–O bond length is 1.82 Å. Hypobromite is the bromine compound analogous to hypochlorites found in common bleaches, and in immune ce ...

): : + 2 OH⁻ → Br + BrO + :3 BrO → BrO + 2 Br

Human health issues

Bromate in drinking water is undesirable because it is a suspected human

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

. Its presence in Coca-Cola's

Dasani Dasani () is an American brand of bottled water created by the Coca-Cola Company, launched in 1999. It is one of many brands of Coca-Cola bottled water sold around the world. The product is filtered and bottled. Marketing United States Coca-C ...

bottled water forced a recall of that product in the UK.

Bromate formation during ozonation

Although few by-products are formed by ozonation, ozone reacts with bromide ions in water to produce bromate. Bromide can be found in sufficient concentrations in fresh water to produce (after ozonation) more than 10 ppb of bromate—the maximum contaminant level established by the USEPA. Proposals to reduce bromate formation include: lowering the water pH below 6.0, limiting the doses of ozone, using an alternate water source with a lower bromide concentration, pretreatment with ammonia, and addition of small concentrations of chloramines prior to ozonation.

Reservoir pollution

Ivanhoe Reservoir looking northeast from west side 2015-10-11

On December 14, 2007, the

Los Angeles Department of Water and Power The Los Angeles Department of Water and Power (LADWP) is the largest municipal utility in the United States with 8,100 megawatts of electric generating capacity (2021-2022) and delivering an average of 435 million gallons of water per day to more ...

(LADWP) announced that it would drain

Silver Lake Reservoir The Silver Lake Reservoir Complex comprises two concrete-lined basins, Ivanhoe Reservoir and Silver Lake, divided by a spillway, in the Silver Lake community of Los Angeles, California. History The lower body of water was named in 1906 for Wat ...

and Elysian Reservoir due to bromate contamination. At the Silver Lake and Elysian reservoirs a combination of bromide from well water, chlorine, and sunlight had formed bromate. The decontamination took 4 months, discharging over of contaminated water. On June 9, 2008 the LADWP began covering the surface of the , open Ivanhoe Reservoir with black, plastic

shade balls Shade balls are small plastic spheres floated on top of a reservoir for environmental reasons, including to slow evaporation and prevent sunlight from causing reactions among chemical compounds present in the water. Also known as bird balls, the ...

to block the sunlight which causes the naturally present bromide to react with the chlorine used in treatment. 3 million of the 40 cent balls are required to cover the Ivanhoe and Elysian reservoirs.

Natural occurrence

Currently no bromate-bearing minerals (i.e., the ones with bromate ion being an essential constituent) are known.

References

{{Bromates Carcinogens

Human health issues

Bromate formation during ozonation

Reservoir pollution

Natural occurrence

See also

References