International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-5 Issue-3 February 2016 44 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Pvt. Ltd. Development of Iron Oxide Coated Sand (IOCS) Adsorbent for Defluoridation Technology Esayas Alemayehu, Thamineni Bheema Lingaiah Abstract - Although safe and reliable water supply is badly needed, the installation of advanced defluoridation plants in regions with low economic resources such as Ethiopia is, at present, very scarce mainly due to operational consideration and settlement characteristics of the people. In such cases the development and popularizing of low cost fluoride removal technologies, which does not demand much money and skilled manpower, is important. Therefore, this study focuses on the removal of fluoride from groundwater by using Iron oxide coated sand (IOCS), which could be used as an alternative defluoridation adsorbent. The influence of design parameters such as contact time, adsorbent dose, solution pH, and initial fluoride concentration was investigated. Basic process characteristics were determined under batch conditions. Fluoride adsorption onto IOCS was strongly pH dependent. The maximum adsorption capacity for IOCS was found to be 136 mg kg -1 . This result was obtained at optimized conditions of solution pH (4.0), contact time (8.0 h), dose (15.0 g L -1 ) and initial fluoride concentration (5.0 mg L -1 ). The uptake of fluoride slightly increased with increasing equilibrium concentration of fluoride ion in solutions. By increasing the initial concentration of fluoride from 3.0 to 10.0 mg L -1 , the adsorption capacity, increased from 90.73 mg kg -1 to 252.17 mg kg -1 . IOCS was found to be promising adsorbent for defluoridation technology. Keywords: Adsorption Technology, Batch Experiments, Defluoridation, IOCS I. INTRODUCTION Iron oxide coated sand (IOCS) is basically a by-product obtained from iron removal groundwater treatment plants i.e. sand used in filters, is coated by iron oxide during filtration process in the plant and time to time it has to be replaced by new sand. Sharma [1] analysed IOCS from twelve different groundwater treatment plants in the Netherlands and found that IOCS had a very high porosity (up to 110 times) and a very large specific surface area (5- 200 times) compared to new sand. It was also found that the iron content of the coatings ranged from 27% to 45% as well as the coating developed on a filter grain was not uniform and different regions of the coating on a sand grain could have a different elemental composition and surface characteristics. Additionally, it was observed that iron (II) adsorption capacities of the coated sand from different plants increased with the increase in the time in use and the iron content of the coating. However, the average annual increase of iron content of the coatings and the iron adsorption capacity were different for the coated sands from different plants, likely due to the difference in water quality, process conditions applied, and time in use. Revised Version Manuscript Received on February 08, 2016. Esayas Alemayehu, Assoc. Prof., at School of Civil & Environmental Engineering, Jimma Institute of Technology, Jimma University, Jimma, Ethiopia. Thamineni Bheema Lingaiah, Asst. Prof., at Jimma Institute of Technology, Jimma University, Jimma, Ethiopia. The grain size of the filter sand increased and their density decreased with the development of the coating [2]. The development of the iron oxide coating on the filter media in iron removal plants may be affected by the water quality and the treatment schemes used in the plant i.e. the ground water quality (pH and concentrations of Fe 2+ , Mn 2+ , Ca 2+ , TOC etc.); the process condition applied (filtration rate, depth of supernatant, depth of the filter media, back wash conditions, aeration efficiency); and type and characteristics of the filter media (grain size, specific surface area) [3]. The presence of such coatings as iron (hydro) oxide can remove iron as well as it can adsorb various inorganic and organic compounds [1, 4-5]. It has long been recognized that, if the adsorbent (solid surface) is chosen carefully and the solution chemistry is adjusted appropriately, adsorption-based processes are capable of removing various contaminants over a wider pH range and to much lower levels than processes based on precipitation [6-10]. In addition to offering more reliable and more efficient removal of uncomplexed pollutants, adsorption processes can often remove inorganically and organically- complexed ions that would not be removed by conventional treatment methodology [11-15]. Previous studies mentioned that IOCS could be used as adsorbent in the removal of different heavy metals from water and wastewater [1, 5, 16]. Column packed with the media (IOCS) were found to be successful in removing uncomplexed and ammonia-complexed cationic metals (Cu, Cd, Pb, Ni, Zn), as well as some oxyanionic metals (SeO 3 , AsO 3 ) from simulated and actual waste schemes over a wide range of metal concentrations [4]. The ability of IOCS to adsorb iron (II) (a common constituent of grand water), arsenic (one of the black listed contaminates) as well as cadmium, lead, nickel and cooper (some of priority pollutants) from ground water has reported [1, 5, 17]. However, the removal efficiency of this medium to adsorb fluoride (number one groundwater quality problem) has not been studied in detail. Many countries have regions where the water contains more than 1.5 mg L -1 of fluoride due to its natural presence in the earth’s crust, or discharge by agricultural and industrial activities, such as steel, aluminium, glass, electroplating. For example, in Southern California Lakeland the fluoride concentration in ground water is about 5 mg L -1 . In Mexico, 5 million people are affected by fluoride in drinking water. In 1993, fifteen of India's thirty two states were identified as endemic for fluorosis [18-21]. In some regions of Africa the fluoride concentration of ground water reaches 20 mg L -1 [22-23]. In the Great Rift Valley regions especially in the dry arid and semiarid areas of Ethiopia fluoride concentration is extremely high due to volcanic action. Research conducted in rift valley of Ethiopia revealed that over 40% of deep and shallow wells