Removal of fluoride from water by using metal-loaded orange waste

摘要

Fluoride pollution in water is a result of natural leaching of fluoride from various fluoride containing mineral or induced anthropogenic activities, such as mining, metal plating, metal refining, semiconductor production and fertilizer manufacture. Fluoride ions are highly reactive ions which has high affinity with bone tissue, so that it can be accumulated easily in bone tissue once we have ingested through food, drinks or cosmetics. Fluoride ion concentration less than 1 mg/l protects our dental caries whereas exceeding the amount of fluoride ion (＞1.5 mg/l) changes the chemical constituent in our bone tissue by replacing hydroxyl ions from hydroxyappatite of our bone tissue and converts it into fluoappatite. Such a change in our bone tissue causes a serious health hazards in severe case known as skeletal fluorosis. In order to remove the excessive level of fluoride from water many defluoridation method such as precipitation, ion exchange, membrane and adsorption were reported to be successful.