Adsorbent Derived fromPinus pinasterTannin for Cationic Surfactant Removal

Abstract Pinus tannin gel (PTG) has proven to be an effective adsorbent for removing various cationic pollutants including heavy metals, dyes, and surfactants. The form of obtaining these condensed tannins from Pinus pinaster bark was conventional aqueous extraction using 5.0% ethanol as additive. The present study focused on the removal of the surfactant hexadecyltrimethylammonium bromide (CTAB) from aqueous solutions using PTG. Kinetic studies showed that the Lagergren, Ho, and Elovich models all adequately explained the kinetics of CTAB adsorption onto PTG, with r2 correlation coefficients of around 0.98. The influences of pH and temperature were found not to be critical, and the CTAB-PTG system was modeled theoretically according to the Langmuir hypothesis using linear, nonlinear, and multiparametric forms, obtaining the values of the activation energies and such system constants as k l . Keywords: Pinus pinaster tanninCTABsurfactant removalnatural adsorbentsgelation Acknowledgments This research was supported by the Comisión Interministerial de Ciencia y Tecnología (CICYT) CTQ 2010-14823/PPQ project and the Junta de Extremadura under project PRI-07A031. I. J. Seabra and M. E. M. Braga acknowledge the Fundação para a Ciência e Tecnologia (FCT-MCTES) for, respectively, the doctoral studentship (SFRH/BD/29133/2006) and the postdoctoral fellowship (SFRH/BPD/21076/2004).