Adsorption of octamethylcyclotetrasiloxane (D4) on silica gel (SG): Retention mechanism

Silica gel (SG) is an efficient adsorbent for the removal of octamethylcyclotetrasiloxane (D4) - a volatile organic silicon compound present in biogas. Complementary physicochemical characterizations of SG before and after D4 adsorption were performed: specific surface area, porosity, pH measurements, infrared spectroscopy, thermodesorption, thermogravimetry and differential scanning calorimetry. A retention mechanism, based on a combination of hydrogen bonding (at low uptake) and polymerization (at higher uptake) is proposed. This mechanism is able to explain the difficulties of siloxane thermal desorption. (C) 2015 Elsevier Inc. All rights reserved.