Evaluation of polymer-agglomerated granular tri-calcium phosphate for fluoride removal from drinking water

Abstract

<span style="mso-bidi-font-weight:bold" lang="EN-GB">The powder and granular forms of tri-calcium phosphate have been used as adsorbents in batch studies for removal of fluoride from aqueous synthetic fluoride solutions. The effects of different operational parameters like <i style="mso-bidi-font-style:normal">p</i>H, adsorbent dose, and contact time have been studied for their optimization. Results show that the fluoride removal is maximum and nearly constant in the <i style="mso-bidi-font-style: normal">p</i>H range 3.0-8.0. The efficiency of fluoride removal increases with the increase in adsorbent dose and contact time. Surface morphology of the adsorbent has been examined with the scanning electron microscope. Experimental equilibrium adsorption data obtained is found to be fitted well with both Langmuir and Freundlich isotherm models. Adsorption kinetic study reveals that the adsorption process follows pseudo second – order kinetics. Column experiments are performed using granular tri-calcium phosphate (GTCP) to find out the optimum flow rate, bed height and the effect of co-existing anions in water. The optimum fluoride removal capacity in column study is found to be 2.1005 mg of fluoride per gram of GTCP. Regeneration of the adsorbent for repeated use has also been studied in column operation and it is established that complete regeneration could be achieved with 0.5% aluminium sulphate solution for 8 cycles without loss of efficiency.

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