REMOVAL OF FLUORIDE FROM WATER BY USING METAL-LOADED ORANGE WASTE A

Abstract

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 ion is highly reactive ion 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 dm-3 protects our dental caries whereas exceeding the amount of fluoride ion (> 1.5 mg dm-3) 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 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 have been reported to be successful. The adsorption of fluoride onto the adsorbent derived from biomass waste is considered to be promising technology because feed materials used for adsorbents are waste themselves, easily available, and have functional diversity; consequently, they have high potential as adsorbents. In the present investigation, 14 different types of metal loaded orange waste adsorbents were successfully prepared from wet orange juice residue just after juicing and dried orange juice residue (DOJR) marketed as cattle food in Japan after simple chemical modification. For the preparation of the adsorbents, wet orange juice residue was treated with lime water in order to saponify the methyl ester part of orange pectin and converted into saponified orange juice residue (SOJR) whereas dried orange juice residue (DOJR) was water washed prior to metal loading reaction. After loading metal ions, adsorption behavior of fluoride ion by using modeled solution and actual plating solution were systematically investigated both in batch and column mode operation.