Natural iron ore as a novel substrate for the biosynthesis of bioactive-stable ZnO@CuO@iron ore NCs: a magnetically recyclable and reusable superior nanocatalyst for the degradation of organic dyes, reduction of Cr(vi) and adsorption of crude oil aromatic compounds, including PAHs

For the first time, stable ZnO@CuO@iron ore nanocomposites (NCs) were green synthesized using magnetic iron ore as a natural substrate through an eco-friendly, simple and cost-effective method. The biosynthesized nanocatalyst was characterized using the SEM, EDS, elemental mapping, point analysis, XRD, FT-IR, polarized microscopy and UV-vis analytical techniques. The XRD and SEM methods confirmed the excellent stability of the nanocatalyst, even for 6 months. Also, the antioxidant ability of the green-synthesized NCs using a DPPH method was assessed per gallic acid and in contrast with ascorbic acid. Furthermore, their antibacterial activities against the common pathogenic bacteria of Pseudomonas aureus, Staphylococcus aureus and Escherichia coli were evaluated at different concentrations compared to chloramphenicol as a positive control. Moreover, the superior catalytic activity of the ZnO@CuO@iron ore NCs was investigated during a series of reactions, including the adsorption of polycyclic aromatic hydrocarbons (PAHs) of heavy crude oil (HCO) obtained from the Shaikhan oil field, the destruction of some organic dyes at room temperature, including methylene blue (MB) and methyl orange (MO), thymol blue (TB), bromothymol blue (BTB), phenol red (Ph.R), methyl red (MR), solochrome black T (SBT) and eriochrome black T (EBT) and finally the reduction of Cr(vi) at ambient temperature using UV-vis spectroscopy. Finally, the magnetic NCs could be simply recovered and reused several times without considerable loss of catalytic activity.