Removal of Cr(VI) by magnetic graphene oxide: Synthesis, mechanism, and mass-balance

The reduction of Cr(VI) toxicity and mitigation of secondary pollution from engineered nanomaterials in wastewater treatment have become critical challenges. To address these issues, we developed a highly efficient, stable, and rapidly separable magnetic graphene oxide (MGO) via hydrothermal synthesis for effective Cr(VI) removal. Particularly, the MGO exhibited exceptional adsorption performance in the Cr(VI) removal process. Experimental and theoretical results revealed that the adsorption process could be described by the pseudo-second-order kinetic and Langmuir isotherm models. Mechanistic studies revealed that Cr(VI) removal occurred through synergistic surface sorption and chemical reduction. For MGO2, the percentage of Cr(VI) removed by chemical reduction and surface sorption was 69.6 % and 30.4 % respectively at the initial Cr(VI) concentration of 20 mg/L. SEM analysis revealed that the particle size of MGO grew up with hydrothermal time increasing. Besides, the time of hydrothermal treatment significantly influenced the surface functional groups of MGO, consequently determining Cr(VI) removal efficiency. This work demonstrated that MGO is a promising adsorbent for sustainable and efficient Cr(VI) remediation in aqueous environments.