REGENERATION OF ACTIVATED CARBONS EXHAUSTED WITH CHLOROPHENOLS

The regeneration of two activated carbons from olive stones used in the removal process of orthochlorophenol (OCP) and metachlorophenol (MCP) has been studied. Chemical regeneration was carried out with these organic solvents: acetone, methanol, ethanol, and benzene. The best regenerant solvent in both cases was ethanol. The regeneration was dependent on both the porosity of the carbon and the chlorophenol isomer; thus, OCP was extracted in greater quantities than MCP. Thermal regeneration was followed by both TGA and TPD-MS techniques, the spent activated carbons were heated up to 1073 and 1223 K, respectively, in an inert flow. The DTG curves showed two peaks at different temperatures corresponding to the removal of physisorbed (at the lowest temperature) and chemisorbed chlorophenol (at the highest temperature). The TPD-MS data indicate that the physisorbed fraction was removed in the form of chlorophenol and/or heavy degradation products; nevertheless, the chemisorbed fraction, together with some of the oxygen surface groups present on the activated carbons, suffered degradation reactions, giving light products such as: H2O, CO, CO2 and H-2. In the case of MCP, the degradation reactions took place to a greater extent due to a greater interaction with the activated carbon surface.