Study Of Fluoride Ion Removal Using Modified Activated Carbon/Nano-scale Aluminum Oxide Hydroxide

Fluorine is one of the essential micronutrients which sustain human physiological processes. A moderate intake of fluorine is important in maintaining healthy teeth. However, excessive intake of fluorine will lead to "fluorosis". Severely harming the human body removal of fluorine by adsorption has the advantages of effluent stability, process train simplicity and cost-effectiveness. The key to the success of removal of fluorine by adsorption is to search for a cost-effective sorbent. This thesis looks into two methods of producing novel sorbent for fluorine adsorption: to modify the surface properties of activated carbon sorbent by impregnation manganese oxide to increase the performance of adsorption of fluoride ions; to study the performance of a novel sorbent - the fluorine removal performance of nano-scale aluminum oxide hydroxideUsing a redox process, granular activated carbon (GAC) was coated with manganese oxides to enhance its ability to adsorb fluoride from an aqueous solution. Compared with plain GAC, the fluoride adsorption capacity of this new adsorbent was improved and at least three times greater than that of uncoated GAC. The surface characteristics of coated GAC were observed with scanning electron microscopy. The surface area of the new adsorbent was calculated using the Brunauer-Emmett-Teller method. X-ray diffraction revealed that manganese oxides are amorphous. X-ray photoelectron spectroscopy demonstrated that manganese existed primarily in the oxidation state +IV. Kinetic and equilibrium adsorption data showed that the adsorption process follows the pseudo-second order kinetic and Freundlich equation models. The sorption data also indicated that the removal of fluoride by adsorption is a highly complex process, involving both boundary layer diffusion and intra-particle diffusion. The pH value of solution influences fluoride removal, and the optimum equilibrium pH value of fluoride adsorption is 3.0.The present study has concentrated on investigating the fluoride removal potential of nano-scale aluminum oxide hydroxide. Series of batch adsorption experiments were carried out to assess parameters that influence the adsorption process. Different parameters of adsorption investigated include the effect of contact time, initial fluoride concentration, adsorbent dose, pH of the solution and effect of co-existing anions. The adsorption was rapid during the initial 30 min but equilibrium was attained within 6 h. Kinetic and equilibrium adsorption data showed that the adsorption process follows the pseudo-second order kinetic and Langmuir isotherm models. The removal efficiency of fluoride was increased with adsorbent dosage. The presence of SO₄^2- or PO₄^3- in aqueous solution was found to reduce the fluoride uptake...