Synthesis and characterization of magnetic recyclable Fe-substituted zinc aluminate photocatalysts with enhanced sunlight-driven degradation of industrial dyes

Abstract Using the sol-gel auto combustion approach with diethanolamine (DEA) as fuel, a sequence of iron-substituted zinc aluminates, ZnFexAl2−xO4 powders, including variable Fe3+ ion concentrations (0 ≤ x ≤ 2) were effectively created. XRD, FT-IR, SEM, EDS, BET, UV-DRS, and VSM were employed to examine the structures, chemical bonds, morphologies, composition, surface area, and optical properties as well as the magnetic behavior of the collected samples. A single-phase spinel structure was gained for the calcined aluminate powders with different interplanar spacing and crystallite sizes, as revealed by the classification results. The bandgap energy (Eg) of adapted aluminates was in the range of 2.08–3.14 eV, identified as being much lower compared to the pure sample (5.60 eV). Thus, Fe3+-substituted ZnAl2O4 samples could be successfully photoexcited using both ultraviolet and visible light, as suggested by the results. Examination of how the four main pollutant types decay when irradiated by sunlight was carried out to assess the samples and establish photocatalytic activity. These contaminants included phenol rhodamine B (RhB), heteropolyaromatic methylene blue (MB), azoic methyl orange (MO) and methyl red (MR). The performance of photocatalytic degradation reached 98% after 150 minutes for all optimal samples of organic dyes. Besides, each of the altered photocatalysts could be recycled and displayed high stability. The S-shaped curve of ferrimagnetism can result from in those samples as found by the magnetic measurements, though pure ZnAl2O4 displays diamagnetic characteristics. The adapted samples show intense improvement in the remanent magnetization (Mr) when compared to pure ZnAl2O4, signifying that magnetic photocatalyst recovery by applying an external magnetic field is easy. Thus, these results offer a convincing sign that ZnAl2O4 powders replaced by Fe3+ could provide the ability to aid in the ecologically-friendly collection of solar energy.