Zeolites – Chemicals for Cleaning
Molecular sieves for cleaning harmful chemicals and saving energy
With applications in laundry detergents, nuclear power and hydrogen-powered vehicles, zeolites are chemicals of the future in the present
The Chemical industry contributes to the production of many of the items and services we regard as indispensable to modern life. The drawback is that it also produces much of the contamination and waste products. The development of Zeolites, however, is a step in a cleaner direction for the chemical industry and our daily lives.
Zeolite Sieves
Zeolites are solids with an interesting molecular structure. They have microscopically small holes which are only big enough for a molecule to enter. Some are found in nature as minerals, others are synthesised by industry or in the laboratory. They are also called molecular sieves because they selectively remove molecules from mixtures.
Alumino-Silcates
They are based on alumino-silcate structures. A silicate is a structure form by alternating silicon (Si) and oxygen (O) atoms. Silicon is like carbon in being able to form four bonds in a tetrahedral arrangement, so silicate has a structure similar to diamond. Due to the presence of the oxygen atoms and the addition of aluminium ions, there is more flexibility to create tiny holes or “micropores”.
Water and Detergents
Zeolites have many applications, and more are being developed all the time. The first major use for zeolites is in the purification of water. Water can be softened by passing it through a zeolite which has pores which accept Calcium and Magnesium ions, which are the ions that make water hard. This same type of zeolite is used more and more in place of polluting phosphate chemicals in laundry detergents.
Agriculture
Other zeolites are used in agriculture. The pores are filled up with potassium, ammonium ions, fertilizer or other micronutrients. The charged zeolite is then ploughed into the fields and these nutrients are slowly released into the soil, encouraging plant growth without polluting groundwater supplies.
Nuclear Power
Some zeolites have been developed to use for nuclear reprocessing. They selectively trap some of the more radioactive products of nuclear power stations and hold them permanently. They can then be hot pressed to close the pores up and make a durable form of holding the waste product securely.
Catalysis
Another important application of zeolites is as catalysts. The pores can be made with the size, shape and properties necessary to position molecules in exactly the correct way to react. This improves the energy-efficiency of many industrial processes, especially in the hydrocarbon industry. It also removes the need to use other potentially polluting catalytic alternatives.
The Future
Recent research has developed a zeolite that can be used to store and release hydrogen effectively for use in greener, hydrogen-powered cars. It has also been suggested recently that if liquid zeolites could be developed there would be even more applications for them. This area of inorganic chemistry is becoming a vital part of the battle against pollution in the world.
