Development of gum acacia based magnetic nanocomposite adsorbent for wastewater treatment.

The present work reports development of a magnetic hydrogel adsorbent material based on the polysaccharide, gum acacia. This graft copolymer nanocomposite hydrogel of gum acacia and poly(3-chloro-2-hydroxypropylmethacrylate) has been made using microwave assisted technique. Magnetite nanoparticles have been generated by in-situ method and trapped in the network structure. The parent hydrogel and the hybrid nanocomposite were evaluated as adsorbents for sequestration of cationic dyes and metal ions from aqueous solution. The FTIR, XRD, SEM, TGA, VSM and BET studies have been performed to characterize the samples with respect to their physical and chemical structure, surface nature, thermal stability and magnetic property. The nanocomposite displayed super-paramagnetic nature owing to the presence of magnetite nanoparticles which also influenced the adsorption characteristics favourably as evident from the comparative studies performed with the non-magnetic parent gel. The nanocomposite exhibited larger surface area of 2.524 m2g−1 compared to the parent hydrogel with surface area of 0.481 m2g−1. The adsorption capability of the parent hydrogel towards methylene blue, rhodamine 6G, Cu(II) and Hg(II) are 224.4, 283.5, 282.4 and 275.3 mgg−1, respectively, were enhanced to 265.2, 344.4, 307.5 and 292.8 mgg−1, respectively, in the case of nanocomposite. The adsorption isotherm and kinetic studies indicated fit of Freundlich isotherm model and pseudo-second-order kinetic model, respectively. The adsorption has been shown to be a multistep process involving boundary layer diffusion and intra-particle diffusion playing major roles. The thermodynamic analysis manifested the adsorption as an exothermic and spontaneous process. The adsorption–desorption process studied in three cycles indicated excellent reusability characteristics of the nanocomposite making it a promising adsorbent material for wastewater treatment. [ABSTRACT FROM AUTHOR]