Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation

Abstract

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min−1, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability.

Influence of the Alcohols on the ZnO Synthesis and Its Properties: The Photocatalytic and Antimicrobial Activities

“…Comparing the results with literature reports, we can observe that high values of k app at 81•10 −3 min −1 [116], 58•10 −3 min −1 [114], or 39.26•10 −3 min −1 [117] are reported for the sample under UV irradiation but are still lower than the best value obtained in this study for ZnO nanoparticles obtained in 1-butanol or 1-pentanol, under visible light irradiation. The photocatalytic reports in the literature are hard to compare, as there is no standard method related to the light used (UV or visible), light intensity, distance from light source, dye concentration, addition of H 2 O 2 or photocatalyst quantity used.…”

“…MB was chosen because it is a phenothiazine dye and has the tendency to form dimers. Therefore, the photocatalytic activity is investigated against both the monomer and the dimer, with their absorption maxima at 664 nm and 614 nm, respectively [112][113][114][115]. There are some literature reports that doped ZnO nanoparticles are capable to photo-decompose the monomer quicker than the dimer [14], the decomposition of the dimer being stronger only after the monomer is completely decomposed.…”

Band-gap engineering of zirconia by nitrogen doping in reactive HiPIMS: a step forward in developing innovative technologies for photocatalysts synthesis

“…Indeed, while the optical band gap energy of the ZrO 2-x N x photocatalyst plays a significant role in determining the degradation efficiency, it is important to consider that other factors can also influence the overall photocatalytic performance. Morphology, size, and crystallinity of the photocatalyst are additional factors that can impact photocatalytic activity ( Tiron et al, 2022 ). These factors affect the specific surface area, surface reactivity, charge carrier mobility, and light absorption properties of the material, all of which contribute to the overall photocatalytic performance.…”

Recent advances in removal of pharmaceutical pollutants in wastewater using metal oxides and carbonaceous materials as photocatalysts: a review

“…: 0.015 μM) in aqueous solution under a UV lamp as a light source. 440 Finčur et al 441 undertook comparative studies by examining the photocatalytic properties of TiO 2 , ZnO and MgO nanopowders prepared by a sol-gel method in the removal of ciprofloxacin from water under UV/simulated sunlight. The corresponding efficiencies of 93.4%, 86.9% and 59.6% suggested TiO 2 to be most efficient nanopowder for this.…”

“…The presence of ciprofloxacin in water acts as pollutant and can be removed by means of a photocatalytic approach. 425–524…”