Performance of Cationic Surfactant Modified Sepiolite and Bentonite in Lead Sorption from Aqueous Solutions

The remediation of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the sorption of lead (Pb) by bentonite (Bent), and sepiolite (Sep), that were modified with cetyltrimethyl ammonium (CTMA+) organic cations. The natural and surfactant modified clays (organo-clays) were characterized with some instrumental techniques including XRF, XRD, FTIR and SEM. Sorption studies were performed in a batch system, and the effects of various experimental parameters including contact time and initial Pb concentration were evaluated upon the Pb sorption onto sorbents. Maximum sorption of Pb was found to be, 83.26, 71.36, 56.25 and 37 mg g-1 for Sep, CTMA-Sep, Bent and CTMA-Bent adsorbents, respectively. The Pb sorption data were fitted to both the Langmuir and Freundlich models. The Freundlich model represented the sorption process better than the Langmuir model. Lead sorption rate was found to be considerably slower for organo-clays than that for unmodified clays. Sorption kinetics was evaluated by pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. The sorption processes of organo-clays followed intraparticle diffusion kinetics. The results showed that the cationic surfactant modified bentonite and sepiolite sorbed less Pb than the unmodified clays.