Preparation of Composite Materials from Activated Carbon, Bone Char and Pumice for Defluoridation of Drinking Water

Abstract

Excessive fluoride exposure from drinking water is a major problem in many parts of the world including Rift valley region of Ethiopia. Preparations of composite material from activated carbon (AC), bone char (BC) and pumice (PU) for fluoride removal from drinking water was studied using batch adsorption. The main focus of the research work lies on preparation of new fluoride adsorbent material having good adsorption capacity. AC, BC and PU were uniformly mixed, grinded and sieved in three different ratio (% mass) based on their fluoride removal efficiency, C1 (25:50:25), C2 (25:40:35) and C3 (25:30:45) respectively.The composites were fired in muffle furnace for at 350  C, 400  C, 450  C and 500  C, cooled down over night and grounded. The material having grain size between 250 µm – 280 µm was used for defluoridation of water. Optimum firing temperature (350 0C) and appropriate mixing ratio of AC, BC and PU by % of mass (25:50:25) respectively was found to be good condition to get the best composite for defluoridation of water. The composite is amorphous non crystalline solid with large surface area mainly composed of oxygen, calcium, carbon, phosphorus and silicon. The composite had good removal efficiency both from real water sample (94.88) and laboratory fluorinated water (95.26) at neutral pH value. The effect of pH of the solution, contact time, adsorbent dose and initial fluoride concentration on the adsorption efficiency of the composite were analyzed. The equilibrium data have been analyzed by the Langmuir and Freundlich isotherm models while the kinetics of adsorption have been investigated by the pseudo-first-order and pseudo-second-order kinetic models. The adsorption experiment best fitted with Freundlich isotherm model and pseudo second order kinetics.