Study of linear and nonlinear isotherm and kinetic parameters of hexavalent chromium adsorption onto reduced graphene oxide coated iron oxide

The present research outlines a procedure for the treatment of municipal wastewater by utilizing reduced graphene oxide/Fe₃O₄ (rGO@Fe₃O₄) magnetic nanocomposites to effectively remove hexavalent chromium through adsorption process. rGO@Fe₃O₄ nanocomposites were synthesized through a conventional procedure and applied for Cr (VI) removal from wastewater. The nanocomposites were characterized using techniques including Fourier Transform Infrared Spectroscopy, X-Ray Diffraction Analysis, Scanning Electron Microscopy, Brunauer–Emmett–Teller surface area analysis, and Raman spectroscopy. The batch adsorption process was optimized by conducting response surface methods for assessing primary variables affecting the adsorption process. Adsorption equilibrium mechanism was analyzed through the application of Langmuir and Freundlich isotherm models, utilizing both linear and nonlinear regression approaches. Furthermore, multiple error functions were employed to assess the validity of models. Results revealed that adsorption mechanism exhibited heterogeneous adsorption, aligning well with the Freundlich isotherm model, which accurately corresponded to experimental data. Moreover, the sorption kinetics were well described by the pseudo-second order kinetic model. The results obtained indicated that adsorption of Cr(VI) onto surface of rGO@Fe₃O₄ nanocomposites is affected by multi-site interactions. The correlation between experimental data and isotherm models further supports the suitability of this material in environmental remediation, offering a promising approach for sustainable wastewater treatment.