Defluoridation of water using calcium aluminate material

A new calcium aluminate (CA) type material has been synthesized using combustion method, which offers formation of smaller particles with open pores. The material thus synthesized has been studied for its fluoride uptake properties in simulated and actual drinking waters, containing fluoride as well as other co-anions. The adsorbent shows high adsorption capacity for fluoride and it is possible to effectively remove fluoride to the tune of 85% from initial concentration of 8.9 mg L−1 and using a dose of 3 g L−1. Kinetics of the adsorption system has been studied indicating that the intra-particle diffusion contributes to the rate determining step. The experimental data fitted well into Langmuir adsorption isotherm and follows pseudo-second-order kinetics. The thermodynamic parameters suggest the complex nature of fluoride uptake reaction, dominated by chemisorption. These studies also infer that fluoride adsorption on CA is spontaneous and an endothermic process. The effective regeneration was achieved by treating the fluoride loaded material by NaOH and H2SO4. CA show potential for defluoridation of water, especially in presence of other anions, when selectivity for fluoride is of prime importance. This class of material suggest the possibility of tailoring of their properties and therefore, likely to attract for attention for defluoridation of water.

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► Calcium aluminate (CA) has no significant effect of pH on fluoride adsorption.
► CA synthesized by combustion method has high adsorption capacity and affinity.
► CA shows petal like hexagonal shape structure and can be regenerated up to 84%.