Functional magnetic nanoparticle/clay mineral nanocomposites: preparation, magnetism and versatile applications

• Recent advances in magnetic nanoparticle/clay mineral (MNP/CM) nanocomposites
• Coprecipitation, pillaring, intercalation, modification for the prepatations
• Distinct magnetism, reactivity and stability of MNP in MNP/CM nanocomposites
• Uses for electromagnetic devices, ferrofluids, adsorbents, catalysts, biomaterials
• Remarks on challenges and opportunities in the field of MNP/CM nanocomposites

Clay minerals and magnetic nanoparticles (MNP) combine to form a class of advanced nanocomposites that would possess exceptional magnetism, stability, adsorption, catalysis, and biocompatibility. This review summarizes and examines recent preparation strategies, properties and applications of magnetic nanoparticle/clay mineral (MNP/CM) nanocomposites. It is organized into five sections. The first section introduces the characteristics of magnetic nanoparticles, clay minerals and the scientific and technological necessity and significance of MNP/CM nanocomposites. The second section is concerned with the preparation of MNP/CM nanocomposites which involve the introduction of MNP into clay minerals via the coprecipitation of MNP and clay minerals, the combination of MNP and pillared clay minerals, the MNP-pillared clay minerals, the combination of surfactants coated MNP and clay minerals, and the intercalation of molecular magnetic compounds into clay minerals. In particular, great strides have been made in the integration of MNP with organo-clay minerals and the resultant nanocomposites can be assembled into the films of MNP/CM nanocomposite. The third focuses on discussion on the distinct magnetism, reactivity and stability of MNP/CM naanocomposites. The superparamagnetic MNP in MNP/CM nanocomposites show a fast response to external magnetic fields and allow MNP/CM nanocomposites to be readily manipulated, well functionalized and easily separated. The fourth section deals with the uses and potentials of MNP/CM nanocomposites in electromagnetic devices, magnetorheological fluids/ferrofluids, magnetic adsorbents, catalysts and biomaterials. The last section presents the view on the existing problems and challenges. Accordingly, it is suggested that future studies need place emphasis on narrowing the size distribution of the MNP/CM nanocomposites, endowing the MNP/CM nanocomposites with more functionalities, uncovering the preparation-modification-structure-magnetism-activity relationships of the MNP/CM nanocomposites, and advancing the practical applications.

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