zeolites have a much different structure than clay minerals. Aluminium, silicon and oxygen are arranged in a regular, micro-porous framework of tetrahedral units. These pores and interconnected voids contain cations and water molecules, and together with the huge surface area make zeolites extremely effective ion and cation exchangers. Cations can be exchanged by ion exchange and water can be removed reversibly by application of heat.
Below are some of the successful application areas of zeolites.
Zeolites are used as a filter media for particulate removal. Additionally, they are used to remove nitrogen, certain organic hydrocarbons (chloramines), and toxic cations such as silver, mercury, nickel, chrome, cobalt, antimony, arsenic, etc. Typical applications would include swimming pools, municipal water systems, and waste water treatment plants. Impurities in water can be divided into several groups. According to physical state there exist insoluble, colloidal and dissolved impurities. Impurities are also classified as mineral, organic, bacteria and biological. Mineral impurities include sand, clay particles, slag and ore particles, salt, alkali and acid solutions. Organic impurities comprise plant and animal tissue residues, sewage etc. Domestic and industrial effluents are the main sources of bacterial and biological impurities. Pure water used for decontamination of effluents by dilution consumes three times the volume of water required for other needs. Recently the problem of prevention of effluent contamination by using recyclable processes has attracted great attention. Introduction of highly effective methods of effluent purification in industrial plants is one of the promising trends in this field. Specific requirements are placed on water used for domestic purposes in every country. New filters for the purification of drinking water and industrial effluents are very important. Practically, water containing suspended particles is purified by percolation through quartz sand of 0.5-2 mm grain size. Quartz sand is however rather expensive and has a low fine-trapping capacity. Studies have shown that quartz sand can be successfully replaced by natural zeolites, which are superior in several ways. The advantages of using clinoptilolite based zeolite filter instead on quartz in physical filtration systems are:The high internal and external surface area of clinoptilolite exceeds that of quartz by more than 10 times Zeolite pore space permeability for water transmission through the grains or fragments is 100% compared to non-permeable quartz grains. The amount or layer thickness of zeolite in the filtration systems can be much thinner (smaller volume) than quartz sand systems – because of the high surface area and pore The density of zeolite is about half of quartz grains thus the volume of one ton of zeolite is twice that of quartz sand. Zeolites also convert calcium and magnesium salts into sodium salts which do not cause hardness. This process uses zeolites which act as a medium for the exchange of the metal ion : Calcium sulfate + sodium zeolite -> calcium zeolite + sodium sulfate The water is usually passed through a bed of the zeolites, which may be a processed sand or synthetic material. The zeolite is then regenerated by passing brine through the bed.