N-butyl Mercaptan Adsorption on Activated Carbon in Aqueous Phase

Adsorption of aqueous n-butyl mercaptan on Granular/Powder Activated Carbon is studied at pH 5-12.4 and 301 K/313 K. In GAC mercaptan blocks micropores and mesopores, whereas in PAC the broader mesopores remain intact providing access to micropores. Mercaptan is transformed into isomer disulfides and non-extractable sulfur forms following acid-base or oxidation-reduction reaction depending on carbon surface groups and iron, and dissolved oxygen. Adsorption obeys a Langmuir isotherm, with oxygen competing with mercaptan (<100 mg mercaptan/L), followed by a Dubinin-Raduschkevich isotherm. Mercaptan uptake increases with temperature. Free energy values suggest that the Langmuir part represents hydrogen bonds whereas the Dubinin-Raduschkevic part the van der Waals ones.