Polyaniline-coated reduced graphene oxide as an efficient adsorbent for the removal of malachite green from water samples

Abstract

An efficient and novel reduced graphene oxide–polyaniline (rGO–PANI) nanocomposite was used for highly rapid removal of malachite green (MG) from water samples. Graphene oxide was synthesized from graphite by Hummers’ method, and after reduction to reduced graphene oxide by sodium borohydride (NaBH4), its surface was modified by polyaniline to synthesize rGO–PANI nanocomposite. Fourier transform infrared spectrophotometry (FT-IR), electron-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) were used to characterize the synthesized rGO–PANI nanocomposite. The important parameters affecting the removal efficiency such as pH, contact time and initial MG concentration were studied and optimized. Also, kinetic models including the pseudo-first- and second-order equations were investigated and kinetic parameters of the studied dye were calculated and discussed. It was shown that the adsorption of MG by rGO–PANI nanocomposite could be described by the pseudo-first-order kinetic equation. Also, the experimental isotherms data were analyzed using the Langmuir and Freundlich equations and based on the results, the adsorption of MG by rGO–PANI nanocomposite was followed by both Langmuir and Freundlich equations. The maximum adsorption capacities for MG were calculated and equal to 666.7 mg g−1 which shows that rGO–PANI nanocomposite is a very efficient adsorbent for the removal of MG from water samples.