Microwave assisted synthesis of karaya gum based montmorillonite nanocomposite: Characterisation, swelling and dye adsorption studies.

A polymer-clay hybrid composite material, (KG-g-PMETAC/MMT) has been synthesised by microwave assisted free radical polymerisation using modified karaya gum and clay mineral and was characterised by various techniques. The karaya gum has been modified by grafting with (2-methacryloyloxy ethyl) trimethyl ammonium chloride prior to making the clay composite. Montmorillonite was used as the clay component. The nanocomposite exhibited pH responsive swelling behaviour. The maximum swelling of 42.23 g/g was observed at pH 7.0 and minimum of 17.28 g/g was noticed at pH 9.2. The water transport mechanism was Fickian in nature and followed second order kinetic model. The adsorption capacities of the nanocomposite for the chosen cationic dyes, methylene blue (MB), toluidine blue (TB), crystal violet (CV) and azure B (AB) were found to 155.85, 149.64, 137.77 and 128.78 mg/g respectively. The dye adsorption was found to be a pseudo-first order kinetic process. The adsorption data is found to best fit with Freundlich isotherm model indicating heterogeneous adsorption and possibility of multilayer formation. Negative value of ΔG indicated the spontaneous nature of adsorption process at the temperatures under study. The reusability studies indicated that desorption of about 70% of the adsorbed dyes can be achieved after two consecutive cycles.