Fe3O4, ZnO nanoparticles and ZnO- Fe3O4 based nanocomposites for waste water treatment: an adsorptive photocatalytic based approach

Iron and zinc based metallo nanoparticles have attracted intensive research interest due to their adsorption and photocatalytic properties. However, the practical application of using these nanoparticles individually always has problems related to selectivity, recovery and reusability. We developed a one-pot synthesis route for multifunctional (ZnO-Fe3O4) nanocomposites. In this study, synthesis and characterization of Fe3O4 NPs, different morphology of ZnO nanostructure (rods, flowers and faceted structures) and ZnO-Fe3O4 (ZF)nanocomposites was investigated and their application in removal of toxic metal ions (Pb(II) and Cu(II)) and organic dye (Methylene Blue) from contaminated water was studied. The detailed characterization of synthesized nanoparticles was carried out using X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, Vibrating Sample Magnetometer and Photoluminescence Spectroscopy. The Fe3O4 nanoparticles were decorated on the surface of ZnO. Presence of Fe3O4 in ZF nanocomposites was also confirmed using ICP-OES and the result suggested that 7.29 wt% of Fe3O4 is present in ZF nanocomposites. Photocatalytic property of ZnO nanostructures and ZF nanocomposite was tested using degradation of methylene blue (MB) dye under UV irradiation. It was observed that 50 mg L-1 of ZF nanocomposite was able to remove 89.2%. ZnO flower showed highest degradation efficiency of 98.57%. Adsorption efficiency of ZF nanocomposite was studied using adsorption of Pb2+ and Cu2+ metal ions (at pH 5.5) on the surface of ZF nanocomposite due to its high surface area. The multifunctional ZF nanocomposite demonstrated promising application in simultaneous removal of heavy metal ions and organic dye which can also be separated by magnet and can be reused multiple times. The results with ZF composites pave way to tailor the composition of the nano ZF composite adsorbent to tackle site-specific contaminations.