STUDY OF SORPTION EQUILIBRIA AND ADSORBENT REGENERATION IN A GAC-ETHYL BENZENE-SUPERCRITICAL CO SYSTEM

Abstract

Regeneration of activated carbon by supercritical media requires the knowledge of adsorption equilibria of the adsorbed solute on activated carbon. This work involves the experimental study of the adsorption equilibria of ethyl benzene- a pollutant commonly encountered in industrial waste streams, on activated carbon in the presence of supercritical carbon dioxide. The analysis was conducted for frontal breakthrough as well as single breakthrough saturations for a range of operating conditions of pressure (100 bar ? P ? 130 bar) and temperature (313 K ? T ? 338 K). The modelling of the adsorption process was successfully accomplished employing a three parameter model. The fitting parameters were comparable for the two types of breakthrough curves. Further, the regeneration of activated carbon adsorbed with ethyl benzene by ethanol-aided supercritical carbon dioxide was investigated. Addition of ethanol to the solvent phase increased the rate and degree of desorption to considerable extents relative to the values observed in the absence of ethanol over the entire range of operating conditions. The study of the enhancement in desorption due to the presence of ethanol suggested the predominance of displacement effect on adsorbed ethyl benzene over the salvation effect on the supercritical phase. The three-parameter model employed to simulate the adsorption breakthrough curves was used to fit the initial portions of the experimental desorption curves, while an equilibrium controlled model was used to fit the tail portions of the profiles.