Abstract

This study explores the removal of malachite green (MG); as examples of hazardous cationic dye pollutants, from aqueous solution by a novel lignosulfonate–graphene oxide–polyaniline (LS-GO-PANI) nanocomposite. LS-GO-PANI consist of three dimentional graphite polymer structure decorated with a number of oxygen containing functionalities such as carboxyl, epoxy, ketone, and hydroxyl groups, and a secondary amine negative charge Q -N-Q-N- Q where Q represents the benzenoid ring from the polyaniline which impart a negative charge density to it in aqueous solution at a wide range of pH. The kinetics of the adsorption data were analyzed using various adsorption models such as Langmuir, Freundlich, and Tempkin were used for the experimental isotherms data. Kinetic and isotherm studies revealed that the Langmuir adsorption isotherm data fit well with the experimental adsorption data compared to the other two models. The adsorption capacity of LS-GO-PANI nanocomposite for MG was found to be 345.4 mg/g, the adsorption maximum was reached after 120 min and follows the linear form of pseudosecond-order kinetics. The adsorption isotherm of adsorption has been investigated in the pH range of 2 to 9 at 298K. Various thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) change were also evaluated. The negative value of ΔG indicates spontaneity of the adsorption process of the malachite green (MG) on LS-GO-PANI nanocomposite.