Granulation of Boehmite without a Binder and its Capacity for Phosphate Adsorption in Aqueous Solution

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In this study, GA (granulated aluminum oxyhydroxide) was prepared from aluminum oxyhydroxide without a binder, and its phosphate adsorption capacity was investigated. Scanning electron microscopy images, specific surface area, pore volume, mean pore diameter, and solution pH of GA were analyzed. The amount of phosphate adsorbed was studied using batch techniques, and was shown to increase at higher temperatures. Moreover, adsorption isotherms were fitted to both the Freundlich equation (correlation coefficient: 0.866 - 0.972) and the Langmuir equation (correlation coefficient: 0.993 - 0.999). Adsorption equilibrium was reached within 24 h. The kinetic data for adsorption was best described by a pseudo-first-order rate equation. A pH of about 3 was the most suitable for phosphate adsorption. Moreover, the adsorption mechanism of phosphate onto GA could be related to the specific surface area and surface hydroxyl groups on GA. Both adsorption and desorption could be performed on GA using NaOH at different concentrations. These results suggest that the GA prepared in this work is appropriate for practical applications.