Influence of Textural Properties and Surface Fractal Dimensions on the Cobalt Adsorption Behavior of Rice Hull Ash Prepared via Solid Combustion

Rice hull ash was prepared via a fast chemical combustion method with ammonium nitrate, urea and milled rice hull. Urea was used as the chemical fuel. The mixture was heated to various temperatures (100 to 1000 degrees C), and the resulting products were compared with products obtained via calcination, in which samples were heated to the same temperatures for 2 hours. Changes in the structure, morphology, texture and surface fractal dimensions with respect to temperature were examined and found to be highly relevant for adsorption applications. The prepared powders were characterized physicochemically by X-ray diffraction and N-2-physisorption measurements. The surface fractal dimensions of the prepared materials were calculated from N-2-adsorptiondesorption isotherms. The results indicate that the fast combustion samples have larger surface fractal dimensions than calcined samples. A correlation between fractal dimensions and Co2+ ion adsorption was found. The present study demonstrates the importance of textural properties and surface fractal dimensions in the adsorption performance of adsorbents.