Adsorption of glycols, sugars, and related multiple -OH compounds onto activated carbons. 2. Solvent regeneration

Solvent regeneration with acetone or methanol was explored as a means to recover adsorbed multiple -OH compounds from activated carbons. Batch-desorption experiments with thermogravimetric analysis demonstrated that regeneration can be carried out in situ, but that high-energy sites are more difficult to regenerate. When solvent regeneration is done in a fixed-bed arrangement, a focusing effect occurs where the solute concentration in the effluent rises to three to six times its initial value during the loading stage. Focusing can be maximized using adsorbents with low oxygen content (less than or equal to 3 wt. %), lower volumetric flow rate (3-15 bed volumes/h), and uniform particle size or particle-size distribution. With methanol as the regenerant, fixed-bed adsorption and regeneration could be operated over several cycles with minimal loss of bed capacity. However, capacity losses occur during acetone regeneration cycles, because acetone is more strongly held on the bed than is methanol.