Nitrate adsorption from water on hazelnut shells

U posljednjih nekoliko godina sve se više pozornosti posvećuje problemu onečišćenja podzemnih voda nitratima. Visoka koncentracija nitrata u vodi, kako u površinskim tako i u podzemnim vodama, posljedica je geološkog sastava tla ili antropološkog djelovanja. Povećane koncentracije nitrata u vodi ozbiljan su problem za zdravlje ljudi uzrokujući rak probavnog sustava i druge anomalije. Djeca do šest mjeseci starosti hranjena dojenačkom formulom, koncentracije nitrata veće od 50 mg/L mogu dovesti do bolesti zvanom methemoglobinemija. Nadalje, prisutnost nitrata u vodonosnicima, može utjecati na eutrofikaciju što uključuje i rast algi te smanjenje otopljenog kisika. Prirodna i umjetna gnojiva koja se koriste u ishrani bilja, proizvodnja detergenata, nekontrolirani ispust otpadnih voda u okoliš te industrijski otpad, glavni su izvori nitrata u vodi. Nitrati su stabilni, dobro topivi ioni koji se teško uklanjaju konvencionalnim metodama kao što su koagulacija, flokulacija ili mekšanje vapnom. Adsorpcija pokazuje zadovoljavajuće rezultate te je iz toga razloga najčešće korištena metoda za uklanjanje nitrata.In recent years, more attention has been dedicated to the problem of groundwater pollution by nitrates. High concentrations of nitrates in water, both in surface and in groundwater, is a consequence of the geological composition of the soil or human activity. Increased concentrations of nitrate in drinking water is a serious hazard to human health, causing abnormalities such as cancerous growths in human digestion system. Children under six months of age fed with infant formula, with nitrate concentrations higher than 50 mg/L, can lead to disease called methemoglobinemia. Furthermore, the presence of nitrate in aquifers can stimulate eutrophication, which compromise the growth of algae and depletion of dissolved oxygen. Natural and chemical fertilizers in crop production, detergent manufacturing, uncontrolled land discharge of municipal wastewater, and industrial wastes have been identified as the main sources of nitrate in water sources. Nitrate is a stable, highly soluble ion that is difficult to remove by conventional water treatment methods such as coagulation, flocculation or lime softening processes. Adsorption process is the most widely employed procedure used for removing nitrate