Synthesis of magnetic zincoxysulfide core/shell nanocomposites (Ni@ZnO0.6S0.4) for COD photocatalytic degradation in oil refinery wastewater

In this work, magnetic Ni@ZnO0.6S0.4, Ni@ZnS and Ni@ZnO a core/shell nanocomposites were prepared through the facile two-step precipitation process as photocatalysts for COD degradation in refinery wastewater. Multiple analysis methods were used to describe the morphology, phase structure and magnetic characteristics of the synthesized photocatalysts such as field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The COD degradation efficiency from ZnO0.6S0.4 nanocatalyst has been investigated as a function of photocatalyst dose, pH and an irradiation time. The Ni@ZnO0.6S0.4 photocatalyst could efficiently degrade the COD content (89%) under visible light irradiation (LED lamp) within 3 hr. The as-acquired Ni@ZnO0.6S0.4 having magnetic properties was readily collected via a simple magnet. More significantly, nearly no lowering of photocatalytic degradation was noticed even after five sequential reaction cycles suggestive of Ni@ZnO0.6S0.4 photocatalyst show perfect stability to reuse.