Investigations on the column performance of fluoride adsorption by activated alumina in a fixed-bed

In the present study, removal of fluoride ions using activated alumina (AA) was investigated in batch and continuous operations. The fluoride removal performance was investigated as a function of the fluoride concentration, flow rate, amount of adsorbent dose and pH. Sorption data have been correlated with Langmuir and Freundlich isotherms. pH was shown to be a decisive parameter on fluoride removal. Percentage fluoride removal as a function of time and uptake capacity related to flow volume were determined by evaluating the breakthrough curves. Data confirmed that early saturation and lower fluoride removal was observed at higher flow rate and at higher concentration. There was a marginal decrease in the uptake capacity after each regeneration cycle. A one-dimensional model for isothermal, axially dispersed fixed-bed adsorption has been numerically solved and compared with the experimental results. Predicted simulation results based on the assumption of pore-diffusion rate-control conditions matches with the experimental data in the initial zone of the breakthrough curve, but deviated marginally in the final tailing zone. (C) 2003 Published by Elsevier B.V.