Decomposition of organic pollutant in waste water using magnetic catalyst nanocomposite

In this study, magnetic recyclable catalyst Fe₃O₄/CuO/ZnO/nanographene platelets (Fe₃O₄/CuO/ZnO/NGP) and Fe₃O₄/CuO/TiO₂/nanographene platelets (Fe₃O₄/CuO/TiO₂/NGP) composites were synthesized by simple hydrothermal method. Methylene blue was used as a model of textile dye to evaluate their catalytic activities. A range of analytical techniques including X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometer were employed to reveal the crystal structure, composition and property of the nanocomposites. The catalytic performance was evaluated by degradation of methylene blue in aqueous solution under UV light and ultrasonic irradiation simultaneously. X-ray diffraction results revealed that cubic spinel Fe₃O₄, monoclinic CuO, hexagonal wurtzite ZnO and graphene platelets exist in Fe₃O₄/CuO/ZnO/NGP, while in Fe₃O₄/CuO/TiO₂/NGP nanocomposites instead of hexagonal wurtzite ZnO, anatase TiO₂ is observed. These results confirmed that the nanocomposites were the desired materials. In addition, all samples exhibited ferromagnetic behavior at room temperature and could be rapidly separated from aqueous solution for repeated use under external magnetic field. From the degradation of methylene blue, it is found that the as-prepared nanocomposites exhibited excellent catalytic activity compared with nanocomposite synthesized without nanographene platelets. The nanocomposites still retain the 100% of the initial activity after it has been used four times repeatedly.