In-situ grown magnetic nanoparticles on graphene oxide for removal of hexavalent chromium from wastewater

Hexavalent chromium (Cr(VI)) is one of the highly polluting and toxic heavy metals in wastewater, making its removal a pressing concern. This study provides a simple method to prepare a magnetic nanoparticle/graphene oxide (MGO) nanocomposite with the in-situ growth method and high-temperature annealing method to remove Cr(VI) from wastewater. After evaluation of influencing parameters on Cr(VI) removal, the result shows that the removal percentage (RP%) of Cr(VI) could reach 83.27 % when the mass ratio of GO to Fe3O4 is 1:1 at the calcination temperature of 723 K with a holding time of 45 min. In addition, the RP% of Cr(VI) is increased with increasing the dosage of MGO and decreased with the increase in the initial Cr(VI) concentration. The Cr(VI) removal kinetics by MGO follows a pseudo-second-order kinetic model. The multilayer adsorption for the Freundlich isotherm model fits better than the Langmuir isotherm model. The positive value of Delta H degrees and negative value of Delta G degrees affirm that the Cr(VI) removal process by MGO is endothermic, thermodynamically achievable, and spontaneous. After adsorption process, MGO can be efficiently separated from the wastewater using a permanent magnet. MGO exhibits an excellent recyclability and reusability with a 10.77 % decrease in RP% of Cr(VI) after five regeneration cycles.