Removal Of Fluoride From Aqueous Solution Using Activated Alumina And Its Regeneration Study

Alumina is the most commonly used adsorbent of defluoridation in industry.In recent years,research was focused on increasing the adsorption capacity by modifying the adsorbent and changing the adsorption conditions.However,few people have focused on studying the regeneration process of alumina.?-alumina,with boehmite(AlOOH)as a precursor,calcined at 500,600 and 700 ?,was employed for the removal of fluoride from aqueous solution.The adsorbent was characterized by XRD,SEM,BET analysis and isoelectric point measurement.Breakthrough curves demonstrated that the adsorption capacity of activated alumina(AA)was affected by the calcination temperature of adsorbent and the initial fluoride concentration.The regeneration of the activated alumina calcined at 500,600,and 700? and the adsorption effect of regenerated activated alumina are main focus of our study.It was found that sodium hydroxide solution of pH of 13.0 was suitable for regeneration of activated alumina.The specific surface area and isoelectric point of activated alumina calcined at 500,600 and 700 ? were increased after regeneration.The Ai3+ dissolution rate was decreased gradually during the five regenerations.The breakthrough curve shows that the activated alumina calcined at 500,600 and 700?,of which adsorption capacities were increased after first regeneration and regeneration rates after first and second regenerations were all greater than 90%,were suitable for reuse.The adsorption capacity of activated alumina calcined at 500,600,and 700? during five regenerations is gradually reducing and the regeneration rate of activated alumina calcined at 500 ?was the best,which is related to the amount of hydroxyl groups in the adsorbent after each regeneration.