Solvent regeneration of spent activated carbon in wastewater treatment

Ethanol regeneration was applied to spent activated carbon which had adsorbed an organic compound in aqueous solutions, including an industrial wastewater. High regeneration efficiency was achieved except for aromatic compounds substituted by electron-donating groups. In the case where ethanol regeneration was not effective, efficient regeneration was possible using an electron-donating solvent such as N,N-dimethylformamide. From the viewpoint of practical use, the solvent regeneration of carbon which had adsorbed phenol was studied using fixed-bed runs. It was found that ethanol and toluene showed high regeneration efficiency. The column desorption of phenol was simulated and gave good agreement with observed results. The regeneration efficiency of ethanol and toluene fell to 80% after five regeneration cycles. The influence of phenol concentration in solvent on the regeneration efficiency was experimentally determined, and the results suggested that the amount of solvent can be minimized by using countercurrent multistage operation.