Zeolites are widely used as catalysts and
sorbents. In chemistry, zeolites are used as
membranes to separate
molecules (only molecules of certain sizes and shapes can pass through), and as traps for molecules so they can be analyzed. 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.
Ion-exchange, water purification and softening Zeolites are widely used as
ion-exchange beds in domestic and commercial
water purification,
softening, and other applications. Evidence for the oldest known zeolite water purification filtration system occurs in the undisturbed sediments of the Corriental reservoir at the Maya city of
Tikal, in northern Guatemala. Earlier, polyphosphates were used to soften hard water. The polyphosphates form a complex with metal ions like Ca2+ and Mg2+ to bind them so that they can not interfere in cleaning process. However, when this phosphate rich water goes in main stream water, it results in
eutrophication of water bodies and hence use of polyphosphate was replaced with use of a synthetic zeolite. The largest single use for zeolite is the global laundry
detergent market. Zeolites are used in laundry detergent as water softeners, removing Ca2+ and Mg2+ ions which would otherwise precipitate from the solution. The ions are retained by the zeolites which release Na+ ions into the solution, allowing the laundry detergent to be effective in areas with hard water.
Catalysis Synthetic zeolites, like other mesoporous materials (e.g.,
MCM-41), are widely used as
catalysts in the
petrochemical industry, such as in fluid catalytic
cracking and
hydrocracking. Zeolites confine molecules into small spaces, which causes changes in their structure and reactivity. The acidic forms of zeolites are often powerful solid-state
solid acids, facilitating a host of acid-catalyzed reactions, such as
isomerization,
alkylation, and cracking.
Catalytic cracking uses a reactor and a regenerator. Feed is injected onto a hot, fluidized catalyst where large
gasoil molecules are broken into smaller gasoline molecules and
olefins. The vapor-phase products are separated from the catalyst and distilled into various products. The catalyst is circulated to a regenerator, where the air is used to burn
coke off the surface of the catalyst that was formed as a byproduct in the cracking process. The hot, regenerated catalyst is then circulated back to the reactor to complete its cycle.
Nuclear waste reprocessing examines vials of SOMS (Sandia Octahedral Molecular Sieve), a zeolite that shows potential for radioactive waste and industrial metals cleanup. Zeolites have been used in advanced
nuclear reprocessing methods, where their micro-porous ability to capture some ions while allowing others to pass freely allows many
fission products to be efficiently removed from the 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 the radioactive
cesium-137 that was present in high levels.
Gas separation and storage 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. On-board oxygen generating systems (OBOGS) and
oxygen concentrators use zeolites in conjunction with
pressure swing adsorption to remove nitrogen from compressed air to supply oxygen for aircrews at high altitudes, as well as home and portable oxygen supplies. 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. Zeolites are also used as a
molecular sieve in
cryosorption style
vacuum pumps.
Solar energy storage and use Zeolites can be used to thermochemically store solar heat harvested from
solar thermal collectors as first demonstrated by Guerra in 1978 and for
adsorption refrigeration, as first demonstrated by Tchernev in 1974. 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 (energy releasing) reaction when transitioning from a dehydrated form to a hydrated form make natural zeolites useful in harvesting waste heat and solar heat energy.
Building materials Synthetic zeolites are used as an additive in the production process of warm mix
asphalt concrete. The development of this application started in Germany in the 1990s. They help by decreasing the temperature level during manufacture and laying of asphalt concrete, resulting in lower consumption of fossil fuels, thus releasing less
carbon dioxide, aerosols, and vapors. The use of synthetic zeolites in hot mixed asphalt leads to easier compaction and, to a certain degree, allows cold weather paving and longer hauls. When added to
Portland cement as a
pozzolan, they can reduce chloride permeability and improve workability. They reduce weight and help moderate water content while allowing for slower drying, which improves break strength. When added to
lime mortars and lime-metakaolin mortars, synthetic zeolite pellets can act simultaneously as a pozzolanic material and a water reservoir. Zeolites have been studied as supplementary materials in cementitious mortars to improve mechanical performance and sustainability. Industrial waste-based zeolites, such as NaP-type and LTA-type zeolites derived from hazardous aluminum waste, can partially replace cement in mortars (5–15% substitution). The LTA-type zeolite, with smaller particle size, acts as a filler and nucleation site for cement hydrates, accelerating hydration and increasing early compressive strength. NaP-type zeolite, with higher silica content, promotes pozzolanic reactions that enhance long-term compressive strength of the mortars.
Niche uses Non-clumping
cat litter is often made of zeolite (or
diatomite). Zeolites are filter additives in
aquaria, contained zeolite granules. When in contact with blood, the granules would rapidly absorb water from the blood plasma, creating an exothermic reaction which generated heat. The absorption of water would also concentrate clotting factors present within the blood, causing the clot formation process to occur much faster than under normal circumstances, as shown
in vitro. The 2022 formulation of QuikClot uses a nonwoven material impregnated with
kaolin, an inorganic mineral activating
Factor XII, in turn accelerating natural clotting. Unlike the original zeolite formulation,
kaolin does not exhibit any thermogenic properties.
Soil treatment In agriculture,
clinoptilolite (a naturally occurring zeolite) 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. 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.
Veterinary and human use Zeolites have some veterinary applications, with
clinoptilolite approved in the EU as an additive for cattle feed. It acts primarily as a detoxifying agent in the gut, where is can absorb undesirable species via ion-exchange before being excreted. For instance, nitrate fertilisers are water soluble and prolonged exposure by dairy cattle is known to impair protein metabolism and glucose utilization. Clinoptilolite adsorbs nitrate ions with good selectivity, allowing it to reduce these ill effects. Zeolites have been studied for human medical applications, particularly for bowel conditions. There are no approved medical uses for zeolites as of 2024. Regardless, they are widely marketed as
dietary supplements. == Mineral species ==