Single or two-solute adsorption processes at supercritical conditions: an experimental study

The adsorption of either benzoic acid or salicylic acid and their mixture on three different matrixes (alumina, silica gel or amberlite) using supercritical carbon dioxide (SC–CO2) as a solvent was studied. Impregnation experiments with either binary (solute+SC–CO2) or ternary (solute+soluteʹ+SC–CO2) systems were performed employing a high-pressure apparatus. The time, pressure and temperature of adsorption were varied in order to analyze the influence of these parameters on the final uptake. A significant time- and temperature-dependence for the impregnation value was found. The pressure influence was only noted up to approximately twice the carbon dioxide critical pressure. Single or multicomponent adsorption led to the preparation of homogeneously impregnated materials, which could be used in controlled drug delivery, sensor technology, catalyst design, etc. Alternatively, if the aim is to fractionate a solid mixture, selective adsorption after multicomponent supercritical extraction could be used as a separation process.