Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents.
Zeolites are widely used in industry for water purification, as catalysts, for the preparation of advanced materials and in nuclear reprocessing. They are used to extract nitrogen from air to increase oxygen content for both industrial and medical purposes. Their biggest use is in the production of laundry detergents. They are also used in medicine and in agriculture.
Zeolites have a porous structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+ and others. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution. Some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. An example mineral formula is: Na2Al2Si3O10•2H2O, the formula for natrolite.
Our zeolite is Australian zeolite, which is cliinoptilolite, a calcium, potassium, magnesium, aluminosilicate.
Commercial and domestic
Zeolites are widely used as ion-exchange beds in domestic and commercial water purification, softening, and other applications. In chemistry, zeolites are used to separate molecules (only molecules of certain sizes and shapes can pass through), and as traps for molecules so they can be analysed. Zeolites have also been used as a filter medium in municipal water treatment plants.
Zeolites have the potential of providing precise and specific separation of gases including the removal of H2O, CO2 and SO2 from low-grade natural gas streams. Other separations include noble gases, N2, O2, freon and formaldehyde. However, at present, the true potential to improve the handling of such gases in this manner remains unknown.
On-Board Oxygen Generating Systems (OBOGS) use zeolites to remove nitrogen from compressed air in order to supply oxygen for aircrews at high altitudes.
The largest single use for zeolite is the global laundry detergent market. This amounted to 1.44 million metric tons per year of anhydrous zeolite A in 1992.
In agriculture, clinoptilolite is used as a soil treatment. It provides a source of slowly released potassium. If previously loaded with ammonium, the zeolite can serve a similar function in the slow release of nitrogen. This can improve crop yields and reduce fertiliser consumption as the zeolite traps and holds the nutrients, preventing them from washing through the soil. Zeolites can also act as water moderators, in which they will absorb up to 55% of their weight in water and slowly release it under the plant’s demand. This property can prevent root rot and moderate drought cycles.
Synthetic zeolite is also being used as an additive in the production process of warm mix asphalt concrete. .
When added to Portland cement as a pozzolan, it can reduce chloride permeability and improve workability. It reduces weight and helps moderate water content while allowing for slower drying which improves break strength.
Domestic pet care
Zeolites are marketed by pet stores for use as a filter additive in aquariums. In aquariums, zeolites can be used to adsorb ammonia and other nitrogenous compounds. However, due to the high affinity of some zeolites for calcium, they may be less effective in hard water and may deplete calcium. Zeolite filtration is used in some marine aquaria to keep nutrient concentrations low for the benefit of corals adapted to nutrient-depleted waters.
Zeolite is an effective ammonia filter, but must be used with some care, especially with delicate tropical corals that are sensitive to water chemistry and temperature.
Non-clumping cat litter is often made of zeolite or diatomite.
Research into and development of the many biochemical and biomedical applications of zeolites, particularly the naturally occurring species heulandite, clinoptilolite and chabazite has been ongoing.
Zeolite-based oxygen concentrator systems are widely used to produce medical-grade oxygen. The zeolite is used as a molecular sieve to create purified oxygen from air using its ability to trap impurities, in a process involving the adsorption of nitrogen, leaving highly purified oxygen and up to 5% argon.
QuikClot brand haemostatic agent, which is used to stop severe bleeding, contains a calcium-loaded form of zeolite.
Synthetic zeolites are widely used as catalysts in the petrochemical industry, for instance in fluid catalytic cracking and hydrocracking.
Zeolites have uses in advanced reprocessing methods, where their micro-porous ability to capture some ions while allowing others to pass freely, allowing many fission products to be efficiently removed from nuclear waste and permanently trapped. Equally important are the mineral properties of zeolites. Their alumino-silicate construction is extremely durable and resistant to radiation even in porous form. Additionally, once they are loaded with trapped fission products, the zeolite-waste combination can be hot pressed into an extremely durable ceramic form, closing the pores and trapping the waste in a solid stone block. This is a waste form factor that greatly reduces its hazard compared to conventional reprocessing systems. Zeolites are also used in the management of leaks of radioactive materials. For example, in the aftermath of the Fukushima Daiichi nuclear disaster, sandbags of zeolite were dropped into the seawater near the power plant to adsorb radioactive caesium which was present in high levels.
The German group Fraunhofer e.V. announced that they had developed a zeolite substance for use in the biogas industry for long-term storage of energy at a density 4x more than water. Ultimately, the goal is to be able to store heat both in industrial installations and in small combined heat and power plants such as those used in larger residential buildings.
Heating and refrigeration
Zeolites can be used as solar thermal collectors and for adsorption refrigeration. In these applications, their high heat of adsorption and ability to hydrate and dehydrate while maintaining structural stability is exploited. This hygroscopic property coupled with an inherent exothermic (heat-producing) reaction when transitioning from a dehydrated to a hydrated form make natural zeolites useful in harvesting waste heat and solar heat energy. Zeolites are also used as a molecular sieve in cryosorption style vacuum pumps.