Super-efficient photocatalytic degradation of methylene blue, methyl orange and rhodamine B dyes using low-cost ZnO–MgO nanocomposite under natural sunlight and its bactericidal activity

A stereotypical co-precipitation method was used to prepare MgO–ZnO (MZ) nanocomposite. To improve the efficiency of the photodegradation mechanism under natural sunlight irradiation, coupling of wide band gap semiconducting materials like ZnO and MgO was chosen. Surface morphology reveals the formation of nanoplates and its thickness is around 35–100 nm which is suitable for the absorption of photons during the photocatalysis mechanism. The MZ nanocomposite’s absorption peak was obtained in the visible region and therefore the photodegradation experiment was carried out for both cationic and anionic dyes and it completely degraded after 20 min of sunlight irradiation. After 5 times of reusability over, rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) dye, the photocatalytic efficiency varied from 96.24 to 91%, 91.16–85% and 98.26–92%, respectively. These nanomaterials also exhibited excellent antibacterial activity against B.subtilis and E.coli bacteria. It was found that the antibacterial efficiency was increased with an increasing concentration of MgO, ZnO and MZ. The results clearly indicate that the prepared MZ showed improved antibacterial capabilities when compared to pure MgO and ZnO, implying that microbial growth in the ecosystem can be reduced by employing MZ. MZ nanomaterial-based photocatalysts discover a new paradigm for the industrial wastewater treatment process in future. Graphical abstract