A STUDY ON REMOVAL OF FLUORIDES FROM WATER BY ADSORPTION ONTO ALUMINUM PHOSPHATE.

Amorphous aluminum phosphate with specific surface area 308m2/g was studied by static adsorption method to assess its capacity for the adsorption of fluoride from synthetic solutions.Influence of contact time,pH and adsorbent dose on the adsorption was investigated.The adsorbent was found to adsorb fluoride rapidly and effectively.The maximum amount of adsorption nearly reached in 30 minutes.The best percent fluoride removal at optimum condition was about 93% at 50mg/L fluoride concentration.The dependence of the adsorption of fluoride on the pH of the solution has been studied to achieve the optimum pH-value and explain the adsorption mechanism.It has been found that maximum adsorption of fluoride from aqueous solutions takes place at pH-value of 5.5.Pseudo-second-order kinetics equation was used to describe the adsorption rate of fluoride and adsorption rate constant was calculated.Adsorption isotherms have been modeled by Langmuir equations and saturated amount of adsorption was calculated as 53.5mg/g.The effect of adsorbent dose on distribution coefficient implied the surface of adsorbent was heterogeneous.