Efficient Fabrication Of Magnetic Functional Graphene/MnFe₂O₄ Hybrids And Their Applications For Wastewater Treatment

Graphene,a rising star in the family of carbon materials,has shown great potential in the field of wastewater environmental remediation thanks to its unique two-dimensional structure and excellent physical and chemical properties.In this thesis,two kinds of modified graphene materials such as magnetic reduced graphene oxide/MnFe₂O₄（RGO/MnFe₂O₄）nanocomposites and three-dimensional（3D）graphene oxide（GO/MnFe₂O₄）mini-motors have been fabricated through low-cost and environment-friendly routes.RGO/MnFe₂O₄ as heterogeneous Fenton-like catalysts for the degradation of organic dyes and GO/MnFe₂O₄ as absorbent for the adsorption of heavy metal ions were investigated.The main contents are briefly summarized as follows:1.RGO/MnFe₂O₄ hybrids have been synthesized using an environmentally benign method where MnSO₄ derived from the modified Hummers method and additional FeSO₄were in situ transformed into MnFe₂O₄ via the hydrothermal process.The preparation process of RGO/MnFe₂O₄ not only avoids the tedious purification of GO as well as the environmental pollution,but also contributes to highly atom-economic synthesis.The as-prepared RGO/MnFe₂O₄ hybrids show good catalytic performance towards the decomposition of methylene blue（MB）dye in the presence of H₂O₂.As a result,MB dye can be 100%decolorized in 130 min by RGO/MnFe₂O₄ hybrid at room temperature and can be magnetically recycled and reused in the Fenton-like reaction.The outstanding catalytic performance of the RGO/MnFe₂O₄ hybrids is not only attributed to the synergetic interactions between RGO and MnFe₂O₄,but also related to the redox couples of Fe/Mn ions during the reaction.2.3D graphene oxide/MnFe₂O₄（GO/MnFe₂O₄）bowl-shaped mini-motors have been constructed by mediating GO suspension with aniline and MnFe₂O₄ via the combination of shear-driven aggregation and capillary force induced procedure.The GO/MnFe₂O₄mini-motor demonstrates high efficiency as the novel adsorbent for heavy metals(i.e.,Pb²⁺and Cd²⁺)and subsequent recovery for recycling purposes.As a result,the material perfectly integrates the adsorption potential of GO and the magnetic and catalytic properties of MnFe₂O₄.On the one hand,GO which is rich in oxygen-containing groups can help to capture heavy metals.Typically,the GO/MnFe₂O₄ adsorbent can thoroughly remove 100 mg L^-1 Pb²⁺and Cd²⁺in 150 min and 180 min,respectively.Furthermore,after chemical detachment of Pb²⁺and Cd²⁺with 0.2 M HCl from the surface of the adsorbent,it can be reused and remains 99.8%adsorption efficiency in the fifth cycle.On the other hand,MnFe₂O₄ enables external magnetic control and functions as the engine to decompose H₂O₂fuel for bubble-driven movement of the mini-motors in the target area,showing promising application prospect in water treatment.