Defluoridation performance and mechanism of nano-scale aluminum oxide hydroxide in aqueous solution

BACKGROUND: The present study has concentrated on investigating the fluoride removal potential of nano-scale aluminum oxide hydroxide (nano-AIOOH). A series of batch adsorption experiments were carried out to assess parameters that influence the adsorption process. The different parameters investigated include the effect of contact time, initial fluoride concentration, adsorbent dose, pH of the solution and co-existing anions. RESULTS: Most of the adsorption took place during the first 30 min and kinetic and equilibrium adsorption data show that the process obeys a pseudo-second-order kinetic equation and the Langmuir adsorption model. The fluoride removal efficiency is greater than 90% between pH 6 and 8 and decreases as pH values increase to 11. The presence of SO42- or PO43- in aqueous solution was found to reduce the fluoride uptake. Desorption studies showed that the fluoride can easily be desorbed at pH 13. CONCLUSION: Nano-AIOOH possesses a maximum fluoride capacity of 3259 mg F- kg(-1), which is comparable with that of activated alumina. Maximum adsorption occurred at around pH 7, which makes nano-AIOOH a potential adsorbent for drinking water treatment. (C) 2009 Society of Chemical Industry