ZnO Photocatalyst Revisited: Effective Photocatalytic Degradation of Emerging Contaminants Using S-Doped ZnO Nanoparticles under Visible Light Radiation

Abstract

Zinc oxide (ZnO) nanoparticles were synthesized by the hydrothermal method and incorporated with diverse amounts of the nonmetal element sulfur (0.5, 0.8, 1.1, 1.3, 2.1, 2.5, 3.2, 6.8, 7.8, 11.9, 12.3, and 17.4 wt %). The physicochemical properties of all nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and N2 adsorption/desorption isotherms, as well as Fourier transform infrared, diffuse reflectance, ultraviolet–visible absorption, and photoluminescence (PL) emission spectra. Pure ZnO and 12 S-containing ZnO nanoparticles were examined as photocatalysts for the degradation of the rhodamine B (RhB) contaminant. Among the S-containing samples, 0.10 g of the sample doped with 0.5 wt % S could degrade 100% of RhB (5 ppm) at pH = 5 in 90 min. It was also found that the 0.8 and 1.1 wt % S-doped ZnO samples could degrade 99 and 97% of RhB in 150 min, respectively. The photocatalytic property of the 0.5 wt % S-doped ZnO was improved by adding a small quantity of ammonium persulfate (0.005 g), so that it could degrade 100% of RhB in 60 min but 10 ppm RhB in 210 min. Moreover, the pure ZnO and the optimal 0.5 wt % S-doped ZnO photocatalysts displayed 2 and 53% degradation of the phenol pollutant in 180 min at pH = 5, respectively. The reusability of the 0.5 wt % S-doped ZnO optimal photocatalyst was tested under optimized conditions (catalyst dosage = 0.10 g, pH = 5, and RhB concentration = 5 ppm) for the RhB degradation exhibiting the degradation efficiency was slightly decreased from 100 to 92% after five successive reactions. Thus, such a photocatalyst could be used as a promising material for application in industrial wastewater treatment processes.

Nickel and sulfur codoped TiO2 nanoparticles for efficient visible light photocatalytic activity

“…Because the semiconductor-based materials have a suitable band structure with the illuminated appropriate light source, the electrons, and holes are generated which can potentially produce hydroxyl radicals ( • OH) and superoxide radicals ( −• O 2 ) through various light-driven chemical reactions. Thus the widely-studied semiconductor photocatalysts are CeO 2 , ZnO, TiO 2 , CdS, Ta 3 N 5 , PbWO 3 , NiO, and BiFeO 3 are proved to be an effective photocatalyst [1][2][3][4][5][6][7][8][9]. Among the several semiconducting photocatalysis, TiO 2 has been considered a promising product in the photocatalytic process due to its high photocatalytic activity, chemical stability, non-toxicity, relatively inexpensive, and showing substantial UV light absorption.…”

Effect of SnO Composition in SnO/SnO2 Nanocomposites on the Photocatalytic Degradation of Malachite Green under Visible Light

“…[8,9] Recently, semiconductor metal oxides have received a lot of attention as potential photocatalysts for dye decontamination due to low-cost methods with high removal efficiency and eco-friendly properties. Although, many semiconductor metal oxides such as TiO 2 , [10] WO 3 , [11] ZnO, [12] ZnS, [13] Fe 2 O 3 , [14] CdS, [15] and SnO 2 [16] have been used for decomposition of organic pollutants under UV and visible light irradiation, it still requires some modifications to enhance its photocatalytic performance. The large bandgap, which allows it to be activated only under UV irradiation, and the fast recombination of photo-induced charge carriers, which impaired photocatalytic activities, are two major disadvantages of using semiconductor metal oxide-based photocatalysts.…”

Metal Oxide-Based Photocatalytic Paper: A Green Alternative for Environmental Remediation

“…TiO 2 is the most investigated metal oxide photocatalyst [81]; however, the use of other metal oxides in photocatalysis, such as ZnO, has been growing lately [30,31,118]. At the nanoscale, these materials can assume several structures, with direct influence on their photocatalytic activity.…”

“…ZnO has also restrictions to its widespread use in photocatalysis under solar radiation as previously mentioned. Thus, several approaches have been suggested to overcome this limitation, including nonmetal and metal doping for reducing the band gap and improving the charge carrier separation, which shifts the absorption range of ZnO to the visible region [118]. Moreover, the surface functionalization of ZnO also has an impact on the final photocatalytic performance due to the narrowing of the material's surface band gap [201].…”