Preparation and adsorption properties of a novel interpenetrating polymer network (IPN) containing carboxyl groups for basic dye from aqueous media

A novel hybrid hydrogel of interpenetrating polymer networks (IPNs) was synthesized by the graft copolymerization reaction among cellulose (Cell), polymethacrylic acid (PMAA) and bentonite (Bent), in the presence of N,N'-methylenebisacrylamide (MBA) as a cross linker and potassium peroxydisulphate (K2S2O8) as an initiator. The structural and morphological characterizations of this IPN, polymethacrylic acid grafted cellulose/bentonite composite (PMAA-g-Cell/Bent), were done using FTIR, XRD, and TGA. The resulting IPN was used as an adsorbent for studying the effectiveness in the removal of methylene blue (MB), which is having a wide range of use in different fields such as biology and chemistry. The effects of contact time, initial sorbate concentration, pH, dose of adsorbent and temperature were studied to optimize the adsorption capacity. The batch sorption technique employed, revealed a maximum adsorption of 99.9% at pH 6.5. Three kinetic models including pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were selected to follow the adsorption processes. The adsorption of MB onto PMAA-g-Cell/Bent could be best described by the pseudo-second-order equation. Adsorption isotherm of MB onto PMAA-g-Cell/Bent was determined and correlated with common isotherm equations such as Langmuir, Freundlich and Sips isotherms. The equilibrium data for MB adsorption well fitted to the Sips adsorption isotherm having R-2 value 0.999 and 1/n, 0.33. Thermodynamic parameters explain that the adsorption process is exothermic in nature and it is a spontaneous process. This novel IPN exhibited excellent performance in MB adsorption. Desorption of MB was studied using 0.1 M HCl. Adsorption/desorption experimental results further proved that the material has sustainable stability over repeated MB loading and stripping. The investigations demonstrated that the PMAA-g-Cell/Bent can be based as an efficient adsorbent for the removal of MB from water and wastewater. (C) 2011 Elsevier B.V. All rights reserved.