Clinoptilolite is currently used in diverse applications such as drinking water purification, air filtration, plant fertilizer and as an animal feed additive. Many studies have shown that clinoptilolite absorbs toxins created by molds in animal feeds, as well as enhancing nutrient absorption by cattle, pigs, lambs and other animals.

Clinoptilolite of volcanic origin has been approved by the EU for use in the category of “Binders, anti-caking agents and coagulants” in feeding stuffs for pigs, rabbits and poultry at levels of up to 20,000 mg/kg. In the United States, clinoptilolite falls under the category of sodium aluminosilicate and has GRAS (Generally Recognized as Safe) status used primarily as an anti-caking agent (Code of Federal Regulations, Title 21, Section 182.2727).

Clinoptilolite forms the basis of the anti-diarrhea drug ‘Enterex’, which was approved by the Cuban Drug Control Agency in 1995. The large majority of toxicology studies on zeolites have been performed on clinoptilolite, chabazite and Zeolite A – the latter because of its widespread use in household detergents. No fatal case arising from the oral uptake of any of these zeolites
has been identified.

NCD Australia

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Natural zeolites were formed by the chemical reaction of volcanic ash and alkaline salt water. This chemical reaction gives natural zeolites an open three-dimensional honeycomb and porous structure. The mined zeolite ore is dried, crushed, and screened to meet USGA particle size specifications. Different natural zeolite deposits can have quite different chemical and physical characteristics. A high quality natural zeolite has a high CEC, low clay, low sodium, and high potassium.

A portion of the potassium in the natural zeolite lattice is available to the plant – more on that in a later note. A & L Laboratories determined the soluble potash by the AOAC ammonium oxalate method. The State of Florida allows ZEO to claim EcoSand as a source for potash. The infiltration rate, pore space, and water holding capacity are similar for the various zeolite and calcined clay amendments. Tifton Physical Soil Testing Laboratory determined the properties of the sand and the mixes.

On a custom basis, EcoSand can be loaded with the nutrients that the customer specifies. The zeolite can be loaded with soluble nitrogen; thus, the nitrogen will be slowly cation exchanged into the soil.

Calcined Clays

Calcined clays are produced by heating montmorillonite clays at high enough temperatures to drive out most of the water. This heating converts the clay to a hard porous material. Calcined clays with higher water content usually have higher CEC’s. The three producers of the commercially used calcined clays are located in the northern Mississippi area.

Compared to natural zeolites, the commercial calcined clays have lower CEC’s.

Cation Exchange Capacity

The standard soil laboratory cation exchange capacity test gives a good indication of the CEC of one amendment versus another. The test’s short exchange time (30 to 60 minutes) causes the natural zeolites CEC results to be lower than actual.

For more accurate zeolite CEC’s, the extraction part of the test should be allowed to continue overnight. The CEC results of the calcined clays are not affected by this short exchange time. There can be large differences in results due to lab methods and techniques.

Zeo, Inc.

The ATLAS contains an entry for each unique zeolite framework type. The term zeolite framework refers to a corner-sharing network of tetrahedrally coordinated atoms. In compliance with the changes in zeolite nomenclature recommended by IUPAC in 2001(2) the title of the Atlas had to be changed from ‘Atlas of Zeolite Structure Types’ to ‘Atlas of Zeolite Framework Types’. This is because the term ‘structure’ implies both the framework and the extra-framework constituents of a zeolite and the latter are excluded in the framework description.

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Synthetic and natural zeolites are hydrated aluminosilicates with symmetrically stacked alumina and silica tetrahedra which result in an open and stable three-dimensional honeycomb structure with a negative charge. The negative charge within the pores is neutralized by positively charged ions (cations) such as sodium. Over 150 zeolite structural types have been identified.

The simplest synthetic zeolite is the zeolite A with a molecular ration of one silica to one alumina to one sodium cation. The zeolite A synthesis produces precisely duplicated sodalite units which have 47% open space, ion exchangeable sodium, water of hydration and electronically charged pores. These properties lead to the various uses of natural and synthetic zeolites.

Biggest Differences Between Natural and Synthetic Zeolites:

• Synthetics are manufactured from energy consuming chemicals and naturals are processed from natural ore bodies.
• Synthetic zeolites have a silica to alumina ratio of 1 to 1 and clinoptilolite (clino) zeolites have a 5 to 1 ratio.
• Clino natural zeolites do not break down in a mildly acid environment, where synthetic zeolites do. The natural zeolite structure has more acid resistant silica to hold its structure together. The clino natural zeolite is broadly accepted for use in the agricultural industry as a soil amendment and as a feed additive.

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Because of their unique porous properties, zeolites are used in a variety of applications with a global market of several million tonnes per annum. In the western world, major uses are in petrochemical cracking, ion-exchange (water softening and purification), and in the separation and removal of gases and solvents. Other applications are in agriculture, animal husbandry and construction. They are often also referred to as molecular sieves.

Framework Structure

A defining feature of zeolites is that their frameworks are made up of 4-connected networks of atoms. One way of thinking about this is in terms of tetrahedra, with a silicon atom in the middle and oxygen atoms at the corners. These tetrahedra can then link together by their corners (see illustration) to from a rich variety of beautiful structures. The framework structure may contain linked cages, cavities or channels, which are of the right size to allow small molecules to enter – i.e. the limiting pore sizes are roughly between 3 and 10 Å in diameter.

In all, over 130 different framework structures are now known. In addition to having silicon or aluminum as the tetrahedral atom, other compositions have also been synthesized, including the growing category of microporous aluminophosphates, known as ALPOs.

Catalysis

Zeolites have the ability to act as catalysts for chemical reactions which take place within the internal cavities. An important class of reactions is that catalyzed by hydrogen-exchanged zeolites, whose framework-bound protons give rise to very high acidity. This is exploited in many organic reactions, including crude oil cracking, isomerisation and fuel synthesis. Zeolites can also serve as oxidation or reduction catalysts, often after metals have been introduced into the framework. Examples are the use of titanium ZSM-5 in the production of caprolactam, and copper zeolites in NOx decomposition.

Underpinning all these types of reaction is the unique microporous nature of zeolites, where the shape and size of a particular pore system exerts a steric influence on the reaction, controlling the access of reactants and products. Thus zeolites are often said to act as shape-selective catalysts. Increasingly, attention has focused on fine-tuning the properties of zeolite catalysts in order to carry out very specific syntheses of high-value chemicals e.g. pharmaceuticals and cosmetics.

Adsorption and Separation

The shape-selective properties of zeolites are also the basis for their use in molecular adsorption. The ability preferentially to adsorb certain molecules, while excluding others, has opened up a wide range of molecular sieving applications. Sometimes it is simply a matter of the size and shape of pores controlling access into the zeolite. In other cases different types of molecule enter the zeolite, but some diffuse through the channels more quickly, leaving others stuck behind, as in the purification of para-xylene by silicalite.

Cation-containing zeolites are extensively used as desiccants due to their high affinity for water, and also find application in gas separation, where molecules are differentiated on the basis of their electrostatic interactions with the metal ions. Conversely, hydrophobic silica zeolites preferentially absorb organic solvents. Zeolites can thus separate molecules based on differences of size, shape and polarity.

Ion Exchange

The loosely-bound nature of extra-framework metal ions (such as in zeolite NaA, right) means that they are often readily exchanged for other types of metal when in aqueous solution. This is exploited in a major way in water softening, where alkali metals such as sodium or potassium prefer to exchange out of the zeolite, being replaced by the “hard” calcium and magnesium ions from the water. Many commercial washing powders thus contain substantial amounts of zeolite. Commercial waste water containing heavy metals, and nuclear effluents containing radioactive isotopes can also be cleaned up using such zeolites.

Zeolites and the Environment

Zeolites contribute to a cleaner, safer environment in a great number of ways. In fact nearly every application of zeolites has been driven by environmental concerns, or plays a significant role in reducing toxic waste and energy consumption.

In powder detergents, zeolites replaced harmful phosphate builders, now banned in many parts of the world because of water pollution risks. Catalysts, by definition, make a chemical process more efficient, thus saving energy and indirectly reducing pollution. Moreover, processes can be carried out in fewer steps, minimizing unnecessary waste and by-products. As solid acids, zeolites reduce the need for corrosive liquid acids, and as redox catalysts and sorbents, they can remove atmospheric pollutants, such as engine exhaust gases and ozone-depleting CFCs. Zeolites can also be used to separate harmful organics from water, and in removing heavy metal ions, including those produced by nuclear fission, from water.

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In a similar way zeolites can absorb ions and molecules and thus act as a filter for odor control, toxin removal and as a chemical sieve. Zeolites can have the water in their structures driven off by heat with the basic structure left intact. Then other solutions can be pushed through the structure. The zeolites can then act as a delivery system for the new fluid. This process has applications in medicine, livestock feeds and other types of research.

Zeolites added to livestock feed have been shown to absorb toxins that are damaging and even fatal to the growth of the animals, while the basic structure of the zeolite is biologically neutral. Aquarium hobbyists are seeing more zeolite products in pet stores as zeolites make excellent removers of ammonia and other toxins. Most municipal water supplies are processed through zeolites before public consumption. These uses of zeolites are extremely important for industry, although synthetic zeolites are now doing the bulk of the work.

Zeolites have basically three different structural variations.

• There are chain-like structures whose minerals form acicular or needle-like prismatic crystals, ie natrolite.
• Sheet-like structures where the crystals are flattened platy or tabular with usually good basal cleavages, ie heulandite.
• And framework structures where the crystals are more equant in dimensions, ie Chabazite.

A zeolite can be thought of in terms of a house, where the structure of the house (the doors, windows, walls and roof) is really the zeolite while the furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. The chain-like structures can be thought of like towers or high wire pylons. The sheet-like structures can be thought of like large office buildings with the sheets analogous to the floors and very few walls between the floors. And the framework structures like houses with equally solid walls and floors. All these structures are still frameworks (like the true tectosilicates that zeolites are).

These variations make the zeolite group very diverse, crystal habit-wise. Otherwise zeolites are typically soft to moderately hard, light in density, transparent to translucent and have similar origins. There are about 45 natural minerals that are recognized members of the Zeolite Group. Industrially speaking, the term zeolite includes natural silicate zeolites, synthetic materials and phosphate minerals that have a zeolite like structure. The complexity of this combined group is extensive with over 120 structural variations and more are being discovered or made every year. Collecting zeolites can be very enjoyable and fulfilling.

Amethyst Galleries’ Mineral Gallery

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Clinoptilolite (a type of mineral zeolite) was discovered in the USA in the Hoodoo mountains in Wyoming in the 1930’s, but zeolites weren’t developed in the USA until synthetic zeolites (molecular sieves) were produced in the 1950’s. The first natural zeolite products produced in Arizona from 1961 to 1976. In 1962 a small quantity of Clinoptilolite mined in SE, Idaho was used by the U.S.D.O.E. in Idaho as a ground water barrier for fission product radionuclides, but full scale operation was delayed until 2001. Several other zeolite deposits have been mined in the western USA over the past decade, but mineral impurities (e.e., clays, calcium carbonates, etc.) have limited the commercial development.

Interest in natural zeolites started to take off in the 1960’s. From the late 1960’s through 2009 there was a slow, but progressive increase in zeolite mineral, mining and product development. Zeolite mining is carried out from deposits by selective, open pit mining methods, then the mined mineral is crushed and screened to the desired size. Drying is used to to activate the product. The natural zeolite products are sold as fine powders (200 mesh or finer) to granular form (14 x 40 mesh to 4 x 8 mesh) for cation exchange, water filtration, soil amendment, odor control, animal feed supplements and heavy metal removal from water. Human nutritional supplement and detox products have been commercially developed since 2005.

AdvancedBioNutritional Research

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-Descriptions and drawings of each framework type
-User-controlled animated displays of each framework type
-Crystallographic data and simulated powder diffraction patterns for representative materials
-Relevant references
-Detailed instructions for building models
-Descriptions of some families of disordered zeolite structures

Ch. Baerlocher and L.B. McCusker

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Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater. Zeolites also crystallize 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. For this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential.

Wikipedia

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