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Spring 1999 - Article 7

From The Lab
How Chelating Agents Work

Soil removal is a complex process that is much more involved than just adding soap or detergents to water. One of the major concerns we have in dealing with cleaning compounds is water hardness. Water is made "hard" by the presence of inorganic ions such as calcium, magnesium, iron and manganese. These metal ions interfere with the cleaning ability of detergents since they act like dirt to the surfactants of a cleaner. These metal ions "use up" the surfactants, making them unavailable to clean the desired surface properly.

A chelating (pronounced keylating) agent is nothing more than an internal water softener. It combines itself with disruptive metal ions in the cleaner solution. The ions are surrounded by
a claw-like chemical (chelating agent) which alters its charge and disables its ability to act "like soil" and disrupt cleaning
(see diagram below).

Some common chelating agents used within the cleaning industry include EDTA (ethylene diamine tetra acetate), NTA (nitrolo tri acetic acid), sodium citrate and zeolite compounds. Phosphates are not technically considered chelating agents, but they do function extremely well at softening water.