Synergistic effect between ternary iron–zinc–copper mixed oxides and graphene for photocatalytic water decontamination

Environment-friendly photocatalysts with wide spectral responses for water decontamination are currently in demand. Ternary iron–zinc–copper mixed oxides with various molar ratios of Fe₃O₄/CuO to ZnO and ternary mixed oxides incorporated on graphene were synthesized using sol–gel and hydrothermal methods. The physicochemical properties of these magnetically separable materials were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, infrared absorption spectroscopy, UV–Vis spectroscopy, vibrating sample magnetometry, and Brunauer–Emmett–Teller (BET) surface area analysis. Furthermore, their photocatalytic and adsorptive properties were investigated using methylene blue as a model organic pollutant. Owing to their higher specific surface area and saturation magnetization, the ternary mixed oxides incorporated on graphene served as better adsorbents and photocatalysts than those without graphene. The adsorption process followed a pseudo-second-order kinetic model and Langmuir adsorption isotherm model, with a maximum adsorption capacity of 68.03 mg/g. The ternary mixed oxide with an Fe₃O₄/CuO to ZnO molar ratio of 1:3 showed better photocatalytic activity under both UV and visible light irradiation, and the efficiency increased with increasing graphene incorporation in the photocatalyst. Moreover, the photocatalyst maintained high efficiency with repetitive use. Radical scavenging experiments revealed that holes were the predominant oxidative species involved in the photodegradation of methylene blue. Thus, these magnetically separable photocatalysts are effective for the removal of organic pollutants from wastewater.