Quaternary ammonium salt assisted removal of genistein and bisphenol S from aqueous solution by nanozeolite NaY: Equilibrium, kinetic and thermodynamic studies

In this work nanozeolite NaY (NZY) was synthesized with an assistance of quaternary ammonium salt and applied as an adsorbent for the removal of two endocrine disrupting compounds genistein (GSN) and bisphenol S (BPS). The successful synthesis of NZY was confirmed by XRD, SEM, EDS, TEM, FT-IR and BET. The batch adsorption process was used to study various parameters such as pH (2-12), temperature (20-45 degrees C), adsorbent dose (0.1-2 g/L), stirring time (15-420 min) and initial adsorbate concentration (10-30 mg/L) for GSN and BPS removal by NZY. Results revealed that the maximum adsorption was achieved in approximate 5 h at pH 2 and 4 for GSN and BPS, respectively. The adsorption behavior was analyzed by Langmuir and Freundlich models and probable mechanisms involved in adsorption of GSN, BPS onto NZY were also investigated. The kinetic study shows that adsorption process of GSN and BPS follows pseudo-second order and intra-particle diffusion models respectively. The thermodynamic parameters such as changes in Gibbs.free energy (Delta G degrees), entropy (Delta S degrees) and enthalpy (Delta H degrees) in the current adsorption process indicated that the adsorption was spontaneous and exothermic in nature. The comparative study shows that the synthesized NZY exhibited very high adsorption capacity than commercial zeolite NaY. (C) 2016 Elsevier B.V. All rights reserved.