A novel chitosan/polyrhodanine nanocomposite: Preparation, characterisation and application for Ni(II) ions removal from aqueous solution

Abstract

Chitosan/polyrhodanine nanocomposite has been synthesised by in situ chemical oxidation polymerisation of rhodanine in chitosan aqueous solution and characterised by scanning electron microscopy, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The FTIR measurement exhibited the existence of relevant functional groups of both polyrhodanine and chitosan in the nanocomposite. The result of TEM image showed the dispersion of polyrhodanine in chitosan matrix performed successfully and the diameter of polyrhodanine nanoparticle estimated smaller than 30 nm. This nanocomposite was used for Ni(II) removal from aqueous solution. Batch adsorption studies were carried out with various Ni(II) concentrations, amount of adsorbent, pH, contact time, and temperature. The pH 8.0 was found to be an optimum pH for Ni(II) adsorption. The Langmuir, Freundlich, and Sips adsorption isotherm model was applied to describe the isotherms. This adsorbent gave the maximum equilibrium uptakes of Ni(II) of 61:43 and 67:70 mg g-1 according to the Langmuir and Sips isotherm models, respectively. The thermodynamic data showed that adsorption processes were thermodynamically favourable, and exothermic in nature. Kinetics studies indicated that the removal of Ni(II) ions followed pseudo-second-order kinetics, suggesting that the specific interaction with surface functional groups was the major route of the removal process.