Graphene oxide–tannic acid nanocomposite as an efficient adsorbent for the removal of malachite green from water samples

Graphene oxide–tannic acid (GO–TA) nanocomposite was used as an efficient, green and rapid adsorbent for the removal of malachite green (MG) from water samples. GO was synthesized from graphite by Hummer method and modified by tannic acid to produce GO–TA nanocomposite. The results of Fourier Transform-Infrared Spectroscopy, atomic force microscopy and Brunner–Emmett–Teller show that the GO–TA nanocomposite with the surface area of 79.6 m2 g−1 has been synthesized successfully. The effect of pH, removal time, initial concentration of MG and stirring rate on adsorption capacity of MG were investigated and the experimental isotherm data were analyzed using the Langmuir and Freundlich equations. Also, two kinetic models including the pseudo first- and second-order equations were investigated and kinetic parameters were calculated and discussed. The results show that, the adsorption of MG onto the GO–TA nanocomposite followed by both Langmuir and Freundlich isotherms with a maximum theoretical adsorption capacity of 500 mg g−1 at 25 °C. Also, the results of kinetic models show that the adsorption of MG onto the GO–TA nanocomposite could be described by the pseudo first order kinetic model. Finally, based on the obtained results, it was concluded that GO–TA nanocomposite is very efficient and rapid adsorbent for the removal of MG from water samples.