Abstract
Xanthan gum (XG) grafted polyaniline@zinc oxide nanocomposite (XGP@ZnO) was synthesized by an oxidative free-radical graft copolymerization reaction. The synthesized nanocomposite was approved by different analytical processes such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The material was further employed for efficient remediation of aqueous solutions contaminated by Cr(VI) and 2,4-dinitrophenol (2,4-DNP) under batch operations. Solution pH values of 2.0 and 4.0 were found to be optimum pH for the adsorption of Cr(VI) and 2,4,-DNP, respectively. On the basis of higher R-2 value and lower chi(2) value, equilibrium data was found to be best fitted by the Langmuir model followed by the Redlich-Peterson model using nonlinear regression analysis. The maximum monolayer adsorption capacity was found to be 346.18 mg g(-1) for Cr(VI) and 123.15 mg g(-1) for 2,4-DNP. With a higher R-2 and low chi(2) value, pseudo-second-order model was established as the best model to describe the equilibrium data suggesting the chemical adsorption to be the rate-determining step. The value of Delta H degrees (+13.06 kJ mol(-1)) for Cr(VI) and (+10.28 kJ mol(-1)) for 2,4-DNP and negative value of Delta G degrees (-1.56 to -3.00 kJ mol(-1)) for Cr(VI) and (-1.75 to -2.94 kJ mol(-1)) for 2,4-DNP in the temperature range of 30-60 degrees C indicated the overall adsorption process to be endothermic and spontaneous in nature. The mechanism involved in the removal of Cr(VI) and 2,4-DNP was electrostatic adsorption coupled reduction which is also evident from EDX analysis.