Groundwater in several parts of India is highly polluted with fluoride. Fluoride, although beneficial to humans in small quantities, causes dental fluorosis, brittle bones and stunted growth when consumed in larger quantities over a period of time. In the present investigation, Aluminum oxide (Al2O3) synthesized by gel combustion process was used as on adsorbent to remove fluoride from aqueous solution. The synthesized adsorbent was characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The effects of pH, initial fluoride concentration and adsorbent dosage on adsorption were studied. Maximum fluoride adsorption on Al2O3 results at lower initial fluoride concentration (1 ppm), high adsorbent dosage (2.5 g/50 mL) and in acidic medium (2 pH). Statistically based experimental designs like Central Composite Design (CCD) and Box Behnken Method (BBM) were used to study the effect of variables on adsorption. The predicted and experimental values are in good agreement with regression coefficient more than 0.9.

Fluoride pollution is widespread in several parts of India. For normal and healthy functioning of living being, less amount of fluoride is very much essential. According to World Health Organization (WHO), the maximum allowable fluoride concentration in drinking water is 1.5 ppm (Popat et al., 1994). Indian Standard (1996) has recommended that the fluoride concentration should be less than 1 ppm for drinking water. According to 1984 guidelines published by the WHO (1984),fluoride is an effective agent for preventing dental caries if taken in ‘optimal’ amounts. Fluorine is the most highly electronegative and reactive element of the halogen family (Waheed and Attar, 2008). It naturally exists in combined fluoride forms in the atmosphere, water and soils (Hang and Liu, 2007). A high percentage of fluoride, 1 to 7.4 ppm, was reported in the eastern and southeastern belt of Karnataka, covering the districts of Gulbarga, Raichur, Bellary, Chitradurga, Tumkur and Kolar, and is scattered in rest of Karnataka (Achuta Rao et al., 1992). The intake of large amounts of fluoride, whether via water or food, can cause serious health problems for human beings and animals, ranging from discolored teeth (i.e., dental fluorosis) to aching joints, brittle bones, stunted growth and deformed limbs (i.e., skeletal fluorosis).

Earlier researchers have studied several techniques like adsorption, ion exchange, precipitation, etc., to defluorinate the water. Investigations were carried using different adsorbents to remove fluoride from aqueous solution, namely, activated carbon, processed bone charpowder, activated bauxite, fly ash, granular calcite, alum, lime (Choi and Chen, 1979; and Killedar and Bhargava, 1988a and 1988b) dry powder, holly oke, neem bark powder, activated cotton, jutecarbon, leaf powder adsorbents (Jamode et al., 2004a and 2004b), hydroxide (Toyoda and Taira, 2000), aligned carbon nanotubes (Li et al., 2003), rare earth oxides (Raichur et al., 2001) and tamarind seeds (Murugan and Subramanian, 2006). Waheed and Attar (2008) used activated alumina R and D 651-X, as an adsorbent to defluorinate water by batch adsorption technique. Hang and Liu (2007) used nanometer-size zirconia to adsorb fluoride in ion exchange chromatography by dynamic adsorption method.

The objective of the present work is to synthesize Aluminium oxide (Al2O3) and to use the same as an adsorbent to remove fluoride from aqueous solution. Batch adsorption studies were conducted to study fluoride removal using synthetic sodium fluoride stock solution. The effects of adsorbent dosage, pH of the solution and initial fluoride concentration were studied. The effect of variables on adsorption was also studied using statistically based experimental designs like Central Composite Design (CCD) and Box Behnken Method (BBM).

Chemical Engineering Journal, Metal Ions Onto Eggshell Powder, Heavy Metal Contamination, Water Resources, Traditional Treatment Techniques, Aquatic System, Equilibrium Biosorption Data, Biosorption Processes, Biomass Concentration, Biosorption Equilibrium, Biosorption Isotherm, Redlich Peterson Models.