General
- Zeolites are minerals
that have a micro-porous structure. Natural zeolites form where
volcanic rocks and ash layers react with alkaline groundwater.
Zeolites also crystallized in post-depositional environments over
periods ranging from thousands to millions of years in shallow marine
basins. Naturally occurring zeolites are rarely pure and are
contaminated to varying degrees by other minerals, metals, quartz or
other zeolites.
- The zeolites are
framework silicates consisting of interlocking tetrahedrons of SiO4
and AlO4. In order to be a zeolite the ratio (Si +Al)/O
must equal 1/2. The alumino-silicate structure is negatively charged
and attracts the positive cations that reside within. Unlike most
other tectosilicates, zeolites have large vacant spaces or cages in
their structures that allow space for large cations such as sodium,
potassium, barium and calcium and even relatively large molecules and
cation groups such as water, ammonia, carbonate ions and nitrate ions.
Physical/Chemical
Properties of Zeolite
- The particular
affinity a species has for an internal zeolite cavity depends on
electronic considerations. The strong electrostatic field within a
zeolite cavity results in very strong interaction with polar molecules
such as water. Non-polar molecules are also strongly adsorbed due to
the polarizing power of these electric fields.
- The heat of water
adsorption for zeolites is high. They also possess high adsorption
capacity, undergo reversible adsorption/desorption, and are
structurally stable. These properties enable zeolite to be used in
solar-powered refrigerators and to store energy during off-peak
periods and release it during peak periods.
Applications
- It is widely been
used as ion-exchange beds in both domestic and commercial water
purification, softening, and other applications. In chemistry, it
separates molecules, only of certain sizes and shapes can pass
through, as traps for molecules so that they can be analyzed, or as
catalysts by confining molecules in small spaces that causes changes
in their structure and reactivity.
- Clinoptilolite, a
naturally occurring zeolite, is used as a soil treatment in
agriculture. It provides a source of slowly released potassium. If the
zeolite is previously loaded with ammonium, it can serve a similar
function in the slow release of nitrogen. Cuban studies even suggests
that some crops may be grown in 100% zeolite or zeolite mixtures,
where the zeolite is previously loaded or has been coated with
fertilizer and micronutrients.
- Zeolite-based oxygen
generation systems are used in producing medical grade oxygen. It is
used as a molecular sieve for extracting oxygen from air, in a process
which involves adsorption of atmospheric nitrogen. The usage of
zeolite is also being explored for a quick clotting of severe
bleeding.
Market and
Report
- Zeolites and
molecular sieves are widely used in a variety of highly important
industrial applications. Zeolites can be of synthetic or natural
origin, with synthetic products dominating commercial markets. The
world synthetic zeolite market totaled approximately $ 1.5 billion in
1994, with catalysts representing the largest sector on a value basis
and detergent zeolites the largest on a volume basis. The largest
utilization for zeolites is in catalysts, principally for petroleum
and petrochemical cracking processes.
-
Worldwide
production of natural zeolites was estimated to be more than 3 million
tons. Estimates for individual countries were Bulgaria, 45,000 tons;
China, 2.5 million tons; Cuba, 500,000 to 600,000 tons; Hungary,
10,000 to 20,000 tons; Italy, 4,000 tons; Japan, 80,000 to 100,000
tons; South Africa 10,000 to 15,000 tons; the United States, 46,800
tons; and the former U.S.S.R., 10,000 tons. Small amounts of natural
zeolites also were produced in Argentina, Australia, Germany,
and Indonesia.
Entrepreneur
who want the information on Production Process,
Technology, Applications, Patent, Consultants, Company Profiles, Reports,
Market can E- Mail us to
informer@eth.net,
primaryinfo@gmail.com
|