What is Zeolite?

    Zeolite is a micro- porous inorganic mineral formed from volcanic ash and sea salt over millions of years. More than 48 zeolite types occur naturally in many parts of the world and over 150 have been synthesized.
  Considerable scientific research in the last few decades has identified broad applications for natural zeolites in construction materials, soil improvements for water and nutrient retention, treatment of water and wastewater for removal of heavy metals and nutrients, dietary supplements for farm-raised animals, health care, and other beneficial uses.

Scientific Development

      First known uses of zeolite can be traced back in the B.C.E when Roman's employed the mineral in their aqua ducts.Natural occurring mineral zeolites were first identified by Cronstedt, a Swedish mineralogist in 1756. Upon rapidly heating a natural mineral, Cronstedt observed that the stones began to dance about as the water evaporated. Using the Greek words which mean "stone that boils," he called this material zeolite.
    Zeolite was not discovered in the USA until the 1950's.  In the 1970's it was used in the treating of wastewater ammonia and radioactive material. As the mineral's amazing filtration and absorption ability became more known, people started using it in pools in Europe and the USA.  Since the 1980's, Zeolite has been identified for use in many different applications and as such has become a very valuable commodity.

Zeolite Framework Structure

      Zeolites are naturally occurring aluminosilicate minerals with three-dimensional structures based on [SiO4]4 - and [AlO4]4 - polyhedra. These polyhedra are linked by their corners to produce an open structural form which has internal cavities in which molecules of various sizes can be trapped. These internal voids, engineered to have specific opening size ranges, trap and hold a variety of molecules which enter the structural matrix.

Molecular Sieve

    Zeolite is the aluminosilicate member of the family of microporous structures known as "molecular sieves". The term molecular sieve refers to a particular property of this material, i.e. the ability to selectively sort molecules based on a size exclusion process and polar properties. Zeolite molecular traps generally act as adsorbents for molecules small enough to pass into their internal cavities. The trapped molecules are held in the cavities by physical and chemical bonding. The most significant point is that the zeolites' interior cavity can be modified during fabrication to target molecules of a particular size and polarity.

Clinoptilolite
(Na3K3)(Al6Si 30O72)•24H2O

   Clinoptilolite is one of the most useful types of natural zeolite. Clinoptilolite possesses a cation-exchange capability of about 2.25 meq g-1, and is able to exchange ammonium-N with sodium (Na) and potassium (K). One gram of clinoptilolite can take in about 2.2 mg ammonium-N.
   Clinoptilolite It is used in many applications such as a chemical sieve, a gas absorber, a feed additive, a food additive, an odor control agent and as a water filter for municipal and residential drinking water and aquariums. Clinoptilolite is well suited for these applications due to its large amount of pore space, high resistance to extreme temperatures and chemically neutral basic structure.
    Clinoptilolite has been used for several years now as an additive to feed for cows, pigs, horses and chickens. It absorbs toxins in the feed that are created by molds and microscopic parasites and has enhanced food absorption by these animals. Clinoptilolite can easily absorb ammonia and other toxic gases from air and water and thus can be used in filters, both for health reasons and for odor removal.

Absorption VS Adsorption

    Absorption is a mechanical process—for example, a dry sponge responding to water by expanding and holding the water. Adsorption is the electrical process (ionic) of opposite electrical ions attracted to and clinging to each other.
    Zeolite has the ability to adsorb irritating airborne gases that attach to microscopic dust particles that exist as free air agents. By itself, zeolite has virtually no fragrance of its own. It is odorless. Nothing is released into the atmosphere to cause irritation or allergic reactions.Therefore, zeolite is the preferred approach to controlling odors.

Production

     Conventional open pit mining techniques are used to mine natural zeolites. The overburden is removed to allow access to the ore. The ore may be blasted or stripped for processing by using front-end loaders or tractors equipped with ripper blades. In processing, the ore is crushed, dried, and milled. The milled ore may be air-classified based on particle size and shipped in bags or bulk.The crushed product may be screened to remove fine material when a granular product is required, and some pelletized products are produced from fine material. Producers also may modify the properties of the zeolite or blend their zeolite products with other materials before sale to enhance their performance.
     Currently, the world’s annual production of natural Zeolite is about 3 million tons.  Only 2% of the world’s natural Zeolite is produced in North America (57,400 metric tons for 2007)
   Synthetic zeolite synthesis is based on crystallization from a gel mixture of silica and alumina mixed in water under elevated pH conditions. The exact zeolite composition is determined by the ratio of SiO2:Al2O2 in the gel mixture, the concentration of the components, the temperature and pressure under which crystallization occurs, and the time period over which the process takes place.
The attractiveness of engineering a zeolite lies in the ability to obtain specific properties in the zeolite including water repulsion, optimum internal cavity size as well as a number of other physical properties.