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Chelating agents, or chelants, include a number of compounds, all having
the ability to coordinate with metal ions at a minimum of two sites. Typically
this bidentate coordination solubilizes or otherwise inactivates these metal
ions, reducing any adverse effects these metals might have on the system in
which they are used.
The chelants discussed in this product review include aminopolycarboxylic
acids and salts (EDTA, HEDTA, DTPA and NTA), hydroxycarboxylic acids and salts
(gluconic acid and salts, and sodium glucoheptonate), and organophosphonates.
Although these products perform largely as chelating agents, there are other
applications for them and when important in volume, they are briefly discussed.
The choice of a particular chelant is dependent on several factors, including
the pH and temperature range of the system, which metal ions are to be controlled,
and the overall economics of the system. As a result, the three broad classes
of chelants discussed in this report are not usually easily interchangeable
and do not usually compete with each other. However, products within the three
major groups covered are often interchangeable. Recently, products with biodegradability
have been introduced in response to environmental pressures.
Chelating agent usage spans a large number of diverse end-use markets. Important
applications include pulp and paper processing; industrial water treatment;
household, institutional and industrial cleaning compounds; metal finishing;
agriculture; photography; rubber processing; food; pharmaceuticals, cosmetics
and toiletries; and textile treatment.
The following pie chart shows consumption of the major types of chelating
agents in the major consuming regions:
Typical growth in all chemistries is forecast at 1–2% annually during
2006–2011, although end-use applications will vary.
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