Heterogeneous Ternary Metal Oxide Nanocomposites for Improved Advanced Oxidation Process under Visible Light

Psyllium-Husk-Assisted Synthesis of ZnO Microstructures with Improved Photocatalytic Properties for the Degradation of Methylene Blue (MB)

Wastewater from the textile industry is chronic and hazardous for the human body due to the presence of a variety of organic dyes; therefore, its complete treatment requires efficient, simple, and low cost technology. For this purpose, we grew ZnO microstructures in the presence of psyllium husk, and the role of psyllium husk was to modify the surface of the ZnO microstructures, create defects in the semiconducting crystal structures, and to alter the morphology of the nanostructured material. The growth process involved a hydrothermal method followed by calcination in air. Additionally, the psyllium husk, after thermal combustion, added a certain value of carbon into the ZnO nanomaterial, consequently enhancing the photocatalytic activity towards the degradation of methylene blue. We also investigated the effect of varying doses of photocatalyst on the photocatalytic properties towards the photodegradation of methylene blue in aqueous solution under the illumination of ultraviolet light. The structure and morphology of the prepared ZnO microstructures were explored by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The degradation of methylene blue was monitored under the irradiation of ultraviolet light and in the dark. Also, the degradation of methylene blue was measured with and without photocatalyst. The photodegradation of methylene blue is highly increased using the ZnO sample prepared with psyllium husk. The photodegradation efficiency is found to be approximately 99.35% for this sample. The outperforming functionality of psyllium-husk-assisted ZnO sample is attributed to large surface area of carbon material from the psyllium husk and the synergetic effect between the incorporated carbon and ZnO itself. Based on the performance of the hybrid material, it is safe to say that psyllium husk has high potential for use where surface roughness, morphology alteration, and defects in the crystal structure are vital for the enhancing the functionality of a nanostructured material. The observed performance of ZnO in the presence of psyllium husk provides evidence for the fabrication of a low cost and efficient photocatalyst for the wastewater treatment problems.

Facile synthesis of ZnO/CuO/Ag2O ternary metal oxide nanocomposite for effective photodegradation of organic water pollutants

The current study is focused on fabrication of a ternary metal oxide nanocomposite (ZnO/CuO/Ag₂O) as an efficient and superior photocatalyst by step-wise implanting of p-type CuO and Ag₂O semiconductors onto an n-type semiconductor (ZnO) via a chemical method. The structural and textural characteristics of the manufactured samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy combined with electron dispersive spectroscopy (FESEM-EDS) and UV-visible spectroscopy. The photocatalytic performance of the fabricated ternary nanocomposite was tested against the photocatalytic degradation of crystal violet (CV) and rhodamine B (RhB) organic dyes under solar light irradiation. The ternary nanocomposite demonstrated about 99.05% and 97.38% degradation efficiency toward CV and RhB dyes under solar light irradiation in a time period of 105 min. The calculated rate constants (k, min^-1) for degradation under solar light over the ZnO/CuO/Ag₂O nanocomposite were 4.26 and 3.61 times higher than the k value obtained over ZnO nanoparticles for CV and RhB dyes, respectively. The main reactive species taking part in the photodegradation processes were •OH and ^•O₂^- over ZnO/CuO/Ag₂O photocatalysts under solar light illumination. Furthermore, the recycle experiments confirmed good reusability and photo-stability of the ZnO/CuO/Ag₂O ternary nanocomposite.