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Natural zeolites in water quality system

The project will focus on testing natural serbian and croatian zeolites for their use in the removal of toxic zinc, chromium, copper and arsenic from waste and drinking water. The performance of natural zeolites and synthetic zeolite a produced in slovenia will be compared.

Many toxic heavy metal ions are discharged into the environment with industrial wastes causing serious water and soil contamination. Heavy metal ions such as Cr3+, Cu2+, Zn2+ and Pb2+ are common metal ions, which accumulate in living organisms causing numerous disorders and diseases. They are also common groundwater contaminants at industrial installations. Arsenic is a well known metalloid which causes serious problems in drinking water since it is extremely poisonous. The presence of arsenic in water is due to the dissolution of minerals from subterranean strata or from an anthropogenic origin such as the leaching of arsenic compounds from smelting of metal ores, agricultural pesticides or wood preservatives. Arsenic contamination of groundwater as a source of drinking water has been a health risk for many regions around the world. The WHO (World Health Organisation) established that even a low concentration of arsenic in drinking water produces negative effects on human health, therefore the arsenic reference value for drinking water is 0.010 mg/dm3. Many wells spread all over the world exceed this value. Thus, there is still an urgent need for development of a cost-effective method for arsenic removal from groundwater and wastewater. Numerous methods exist for removing heavy metal and arsenic ions from water. Precipitation, ultra-filtration, reverse osmosis, ion exchange and adsorption are some of the commonly used techniques. As it is easy to remove the sorbent from aqueous media after treatment, sorption is generally considered to be the most suitable method. The use of alternative low-cost materials such as potential sorbents has recently been extensively studied. The processes using activated carbons or alumina as adsorbent are considered to be particularly competitive and effective, however they are not suitable in developing countries due to the high costs associated with the production and regeneration of the spent adsorbent. Accordingly, ion exchange is considered to be cost-effective only when low-cost exchangers such as natural zeolites are used. Zeolites are naturally occurring aluminosilicates. They are well known for their ion exchange, catalytic and sorption properties. The structures of zeolites consist of three-dimensional networks of SiO4 and AlO4 tetrahedra arranged in an alternating manner. This produces negatively charged lattice, where the presence of exchangeable captions such as sodium, potassium or calcium balances the net negative charge. These captions are exchangeable with the captions of heavy metals in water solutions. The arsenic is found as anionic species in water, thus it is not exchangeable by the ions from zeolite. However, the high specific area of zeolites as well as the possibility of a chemical modification of the zeolite surface, allow zeolites to be effective sorbents for anionic species also. Clinoptilolite is the most abundant natural zeolite. Its tabular morphology shows an open reticular structure of easy access exhibited by (eight- and ten-member ring) channels up to 0.7 nm in diameter. The clinoptilolite samples from various regions show different sorption and ion-exchange behaviour, the difference being mainly caused by a different composition of zeolitic tuffs. In this project, two large clinoptilolite deposits from SERBIA (Vranjska Banja and Beocin) and one from CROATIA (Donje Jesenje) will be investigated for use in heavy metal and arsenic ion removal from waste and drinking water. Ion exchange and adsorption methods will be used for the pollutant removal. The performance of natural zeolitic tuffs will be compared with the adsorption characteristics of synthetic zeolite A (4 nm channels) produced in SLOVENIA in order to evaluate their technological and economical advantages and disadvantages.
Acronym: 
PUREWATER
Project ID: 
4 208
Start date: 
01-05-2008
Project Duration: 
36months
Project costs: 
900 000.00€
Technological Area: 
Water Pollution / Treatment
Market Area: 
Water treatment equipment and waste disposal systems

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