Sodium Zeolite A, used as a water softener in detergent powder
The loosely-bound nature of extra-framework metal ions (such as in zeolite NaA, right) means that they are often readily exchanged for other types of metal when in aqueous solution. This is exploited in a major way in water softening, where alkali metals such as sodium or potassium prefer to exchange out of the zeolite, being replaced by the "hard" calcium and magnesium ions from the water. Many commercial washing powders thus contain substantial amounts of zeolite. Commercial waste water containing heavy metals, and nuclear effluents containing radioactive isotopes can also be cleaned up using such zeolites.
Zeolites and the Environment
Zeolites contribute to a cleaner, safer environment in a great number of ways. In fact nearly every application of zeolites has been driven by environmental concerns, or plays a significant role in reducing toxic waste and energy consumption.
In powder detergents, zeolites replaced harmful phosphate builders, now banned in many parts of the world because of water pollution risks. Catalysts, by definition, make a chemical process more efficient, thus saving energy and indirectly reducing pollution. Moreover, processes can be carried out in fewer steps, miminising unecessary waste and by-products. As solid acids, zeolites reduce the need for corrosive liquid acids, and as redox catalysts and sorbents, they can remove atmospheric pollutants, such as engine exahust gases and ozone-depleting CFCs. Zeolites can also be used to separate harmful organics from water, and in removing heavy metal ions, including those produced by nuclear fission, from water.
Zeolites in the UK
Zeolite science and technology has traditionally been very strong in the UK. Partly this has been due to the scientific legacy of the late Professor Richard Barrer, the "father of zeolite science" who, during a career of over 50 years in various British universities, laid the foundations for the study of zeolites and discovered many of their important properties. The prominence of the UK has also been associated with the strength of its chemical industry, particularly in areas where zeolites have applications, such as petrochemicals, detergents, fine chemical synthesis and nuclear processing. Many British companies continue to have major R&D projects in these areas.