The effect of clay treatment on remediation of diethylketone contaminated wastewater : uptake, equilibrium and kinetic studies

The ability of four different clays to adsorb diethylketone was investigated in batch experiments aiming to treat wastewater with low solvent concentrations. The adsorption performance in terms of uptake followed the sequence: vermiculite > sepiolite = kaolinite = bentonite, for all the adsorbent doses tested (from 0.1 to 1.5 g) in 150 mL of ketone solution (800 mg/L). The equilibrium data in the batch systems were described by Sips and Dubinin–Raduskevich isotherms. The best fits for bentonite and kaolinite clays were obtained with the Sips isotherm and for sepiolite and vermiculite the best fits were obtained with the Dubinin–Raduskevich model. Kinetic data were described by pseudo-first and pseudo-second order kinetics models. The best fit was obtained for the pseudo-first order model which assumed that the interaction rate was limited only by one process or mechanism on a single class of sorbing sites and that all sites were time dependent. The presence of functional groups on the clay surface that might have interacted with the solvent was confirmed by FTIR. XRD analysis was also performed. This study showed that the tested clays are very effective for the removal of diethylketone from industrial effluents.The authors gratefully acknowledge the financial support by the Fundacao para a Ciencia e Tecnologia, Ministerio da Ciencia e Tecnologia, Portugal. Hugo Figueiredo thanks FCT for a PhD grant (SFRH/28201/BD/2006) and Cristina Quintelas thanks FCT for a Post doctoral grant (SFRH/BPD/32113/2006). The authors would like also to thank to Minas de Barqueiros, S.A., Prof Rui Boaventura (FEUP-Portugal) and Prof Isabel Correia Neves (Dep. Quimica, UM, Portugal) who kindly supplied the clays and to Dr. A.S. Azevedo for collecting the powder diffraction data (Dep. of Earth Sciences, UM, Portugal). Russell Paterson is thanked for language editing