Synthesis of a magnetic iron oxide/zinc oxide engineered nanocatalyst for enhanced visible-light photodegradation of Cartasol brilliant violet 5BFN in aqueous solution

Engineered nanocomposites combine the physicochemical properties of different materials, increasing the applicability for environmental remediation. Cartasol brilliant violet (5BFN) is an organic and toxic compound that pollutes water sources due to the widespread use in the industry. In this study, a novel engineered nanocomposite was fabricated using magnetic iron oxide (IO-NPs) and zinc oxide (ZnO-NPs) nanoparticles and used for 5BFN photodegradation in aqueous solutions. The IO-NPs and ZnO-NPs were synthesized via the co-precipitation and green methods, respectively. A crystalline structure was confirmed for both nanoparticles with an average crystallite size of about 50 nm for IO-NPs and 29 nm for ZnO-NPs. The IO-NPs’ surface was modified using a silica matrix, allowing the encapsulation, accumulation, and formation of the ZnO-NPs shell. Although a superparamagnetic behavior is predominant, the ZnO-NPs promoted low spin coordination and decreased the saturation magnetization from 66.8 to 17.5 emu/g. A sterical stabilization with the siloxane and silanol groups of the silica matrix also decreases the magnetic response. The 5BFN photodegradation was evaluated varying the IO:ZnO weight ratio, initial pH, and nanocatalyst dose. A maximum photodegradation performance of 89.2% was achieved using 0.4 g/L of IO@ZnO-NPs and pH 6.8. The IO:ZnO weight ratio plays an important role, increasing the photocatalytic performance through the reduction of the bandgap. This enhances the visible light adsorption on the IO@ZnO-NPs, allowing a higher 5BFN photodegradation and extending their application for other organic dyes in water sources.