A zeolite is any member of the hydrated aluminosilicate minerals containing alkali and alkaline-earth metals. They are characterized by lability toward ion exchange and reversible dehydration.
The basic framework is a three-dimensional tetrahedral structure consisting of oxygen, aluminum, and silicon atoms. If only silicon is present, the tetrahedron is neutral; if aluminum is substituted for the silicon atoms, a positive metal ion is required to maintain a charge balance.
A zeolite is a crystalline, hydrated aluminosilicate of alkali and alkaline earth cations with an infinite, open, three-dimensional structure. It can lose and gain water reversibly and exchange extraframework cations without changing crystal structure.
It is also able to adsorb heavy metals and other dissolved pollutants in water. It is used in wastewater treatment to remove a wide range of contaminants.
The pore size in a zeolite is smaller than the particle size of an organic molecule, allowing small molecules to pass through them quickly, but larger ones cannot. This is why they are sometimes called molecular sieves.
Zeolites are natural minerals that occur on the earth. They are found in a variety of places around the world. They can be extracted and mined for their uses, or they can be made into synthetic zeolites.
Zeolites are crystalline solids consisting of an aluminosilicate framework in which silicon and aluminum cations are tetrahedrally coordinated. These cations are enclosed by four oxygen anions (O2-).
In this system, open cavities in the form of channels and cages can be generated where water molecules and exchangeable extra-framework cations can be inserted/exchanged. They can also be used as adsorbents for gases.
They are mainly found naturally, but synthetic zeolites are also available. Synthetic zeolites are made from various elements, including alumina and silica.
They are a good detoxifier, preventing many harmful toxins from entering the human body. They also support healthy liver function and help prevent inflammation, which may lead to depression, fatigue, autoimmune disorders, and other serious health issues.
Zeolites are widely used for water treatment, filtration, and separation. They are effective in removing turbidity, hydrocarbons, ammonia, nitrates and phosphates, oils, and other pollutants from wastewater.
The pore structure of zeolite allows it to act as a molecular sieve that filters molecules based on their size. The negatively charged surface binds minerals like sodium, potassium, and calcium.
Some zeolites can also be modified with acids to increase their adsorption capacity for various pollutants. The types and concentrations of the reagents can affect the results.
Natural zeolites are also being studied for their biological properties, as they can reduce turbidity, chromium, and other elements from water. They can also act as soil amendments for nutrient retention and water retention on turf farms and golf courses, especially in drought areas.
Synthetic zeolites have been extensively used since 1950 to improve insulated windows, automobile air-conditioning systems, refrigerators, air brakes on trucks, laundry detergents, and more. They have large internal pore volumes, molecular-size pores, and regular crystal structures that are easily tailored to desired properties and applications.
A key challenge is minimizing the energy consumption of the manufacturing process to ensure a low CO2 footprint per kilogram of zeolite produced. A number of strategies are currently in development and employed to reduce the energy requirements of synthesis gels.
In particular, increasing the solid content in a synthesis gel, adjusting the feeding slurry, introducing heat recovery during the drying step, and using electrical heating during calcination contribute to reducing overall energy consumption. Calcination is typically performed by belt calciners or rotary kilns under oxidizing conditions. This approach is accompanied by significant energy savings due to lower firing temperatures and lower emissions from the exhaust gas after-treatment system.