Bromate
Overview
 
The bromate anion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

, BrO, is a bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

-based oxoanion
Oxyanion
An oxyanion or oxoanion is a chemical compound with the generic formula AxOyz− . Oxoanions are formed by a large majority of the chemical elements. The formulae of simple oxoanions are determined by the octet rule...

. A bromate is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 that contains this ion. Examples of bromates include sodium bromate
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, mainly used in continuous or batch dyeing processes involving sulfur or vat dyes and as a hair-permagent, chemical agent, or gold solvent in gold mines when used...

, , and potassium bromate
Potassium bromate
Potassium bromate , is a bromate of potassium and takes the form of white crystals or powder.-Uses in baking:Potassium bromate is typically used as a flour improver , strengthening the dough and allowing higher rising. It is an oxidizing agent, and under the right conditions, will be completely...

, .

Bromates are formed many different ways in municipal drinking water. The most common is the reaction of ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

 and bromide
Bromide
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...

:
Br + → BrO


Electrochemical processes, such as electrolysis of brine without a membrane
Chloralkali process
The chloralkali process is an industrial process for the electrolysis of sodium chloride solution . Depending on the method several products beside hydrogen can be produced. If the products are separated, chlorine and sodium hydroxide are the products; by mixing, sodium hypochlorite or sodium...

 operating to form hypochlorite
Hypochlorite
The hypochlorite ion, also known as chlorate anion is ClO−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1.Hypochlorites are the salts of hypochlorous acid...

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

Photoactivation (sunlight exposure) will encourage liquid or gaseous chlorine to generate bromate in bromide-containing water.

In laboratories bromates can be synthesized by dissolving in a concentrated solution of potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 (KOH).
Encyclopedia
The bromate anion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

, BrO, is a bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

-based oxoanion
Oxyanion
An oxyanion or oxoanion is a chemical compound with the generic formula AxOyz− . Oxoanions are formed by a large majority of the chemical elements. The formulae of simple oxoanions are determined by the octet rule...

. A bromate is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 that contains this ion. Examples of bromates include sodium bromate
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, mainly used in continuous or batch dyeing processes involving sulfur or vat dyes and as a hair-permagent, chemical agent, or gold solvent in gold mines when used...

, , and potassium bromate
Potassium bromate
Potassium bromate , is a bromate of potassium and takes the form of white crystals or powder.-Uses in baking:Potassium bromate is typically used as a flour improver , strengthening the dough and allowing higher rising. It is an oxidizing agent, and under the right conditions, will be completely...

, .

Bromates are formed many different ways in municipal drinking water. The most common is the reaction of ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

 and bromide
Bromide
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...

:
Br + → BrO


Electrochemical processes, such as electrolysis of brine without a membrane
Chloralkali process
The chloralkali process is an industrial process for the electrolysis of sodium chloride solution . Depending on the method several products beside hydrogen can be produced. If the products are separated, chlorine and sodium hydroxide are the products; by mixing, sodium hypochlorite or sodium...

 operating to form hypochlorite
Hypochlorite
The hypochlorite ion, also known as chlorate anion is ClO−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1.Hypochlorites are the salts of hypochlorous acid...

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

Photoactivation (sunlight exposure) will encourage liquid or gaseous chlorine to generate bromate in bromide-containing water.

In laboratories bromates can be synthesized by dissolving in a concentrated solution of potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 (KOH). The following reactions will take place (via the intermediate creation of hypobromite
Hypobromite
The hypobromite ion, also called alkaline bromine water, is BrO−. Bromine is in the +1 oxidation state. Hypobromite is the bromine compound analogous to hypochlorites found in common bleaches, and in immune cells...

):
+ 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
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

. Its presence in Coca Cola's Dasani
Dasani
Dasani is a brand of bottled water from the Coca-Cola company, launched in 1999, after the success of Aquafina . It is one of many brands of Coca-Cola bottled water sold around the world....

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

Bromate usually forms when water containing bromide is purified using ozone, a method used at filtration plants. Proposals to reduce bromate formation include switching to enclosed atmospheric tank contact systems, lowering the water pH to between 5.9 - 6.3, and limiting the doses of ozone.

Reservoir pollution

On December 14, 2007, it was announced by the Los Angeles Department of Water and Power
Los Angeles Department of Water and Power
The Los Angeles Department of Water and Power is the largest municipal utility in the United States, serving over four million residents. It was founded in 1902 to supply water and electricity to residents and businesses in Los Angeles and surrounding communities...

 (LADWP) that the Silver Lake and Elysian reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s were going to be drained due to bromate contamination. At the Silver Lake and Elysian reservoirs a combination of bromide from well water, chlorine and sunlight formed bromate. The decontamination took 4 months and resulted in the discharge of over 600000000 gallon of contaminated water.

On June 9, 2008 the LADWP began covering the surface of the 10 acres (4 ha), 58000000 gallon open Ivanhoe reservoir with black, plastic balls to block the sunlight which causes the naturally present bromide to react with the chlorine used in treatment. It will require 30 million of the 40 cent balls ($12 million) to cover the Ivanhoe and Elysian reservoirs.
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