Photocatalytic performance improvement by utilizing GO_MWCNTs hybrid solution on sand/ZnO/TiO2-based photocatalysts to degrade methylene blue dye

The removal enhancement of organic contaminations and optimization of the photocatalytic efficiency by Box-Behnken design using ZnO-TiO2/porous graphene aerogel

In this study, zinc oxide-titanium dioxide/graphene aerogel (ZnO-TiO2/GA) was successfully synthesized through a simple and cost-effective hydrothermal self-assembly process. Besides, the surface response model and the experimental design according to the Box-Behnken model were selected to determine the optimal removal efficiency for crystal violet (CV) dye and para-nitrophenol (p-NP) phenolic compound. According to the obtained results, the highest degradation efficiency for CV dye of 99.6% was obtained under the following conditions: pH 6.7, CV concentration of 23.0 mg/L, and catalyst dose of 0.30 g/L. For p-NP, the degradation efficiency reached 99.1% under the following conditions: H2O2 volume of 1.25 mL, pH 6.8, and catalyst dose of 0.35 g/L. Therewithal, kinetic models of adsorption-photodegradation, thermodynamic adsorption, and free radical scavenging experiments were also investigated to propose the specific mechanisms involving the removal of CV dye and p-NP. According to the aforementioned results, the study provided a resulting ternary nanocomposite with great removal performance for water pollutants via the synergetic effects of adsorption and photodegradation processes.

Silica sand-supported nano zinc oxide-graphene oxide composite induced rapid photocatalytic decolorization of azo dyes under sunlight and improved antimicrobial activity

Here, silica sand-supported heterojunction composite of nano zinc oxide (nZnO) and graphene oxide nanosheet (nZnO-GO@SS) was prepared, and its potential as an efficient photocatalyst for the degradation of methylene blue (MB) and Rhodamine-B (Rh-B) under sunlight was demonstrated. Transmission electron microscopy confirmed the uniform distribution of spherically shaped nZnO of average size of approximately 8 nm over graphene oxide nanosheet (GO) in the composites. Photodegradation yields of 95.3% and 97.5% for 100 ppm of MB and Rh-B dye within 150 and 220 min, respectively, were achieved under sunlight by the prepared nanocatalyst (nZnO-GO), while sand microparticle-supported nanocatalyst (nZnO-GO@SS) demonstrated faster degradation of MB and Rh-B, i.e., within 120 and 160 min, respectively. Furthermore, when the recyclability of the photocatalyst was studied, the nZnO-GO exhibited more than 80% degradation efficiency after five cycles for both the dyes and nZnO-GO@SS demonstrated 10% higher (~90%) removal capability after five cycles of reuse. Furthermore, the antibacterial assay showed complete inactivation of Escherichia coli and Staphylococcus aureus bacterial strain by nZnO-GO@SS. Hence, our proposed strategy for the removal of toxic dyes from the aquatic environment under sunlight proved that sand microparticle-supported nanocatalyst (nZnO-GO@SS) might be a superior, cost-effective, and suitable photocatalytic system for industrial applications toward toxic dye removal and decontamination from industrial wastewater.

Titanium Dioxide–Reduced Graphene Oxide Composites for Photocatalytic Degradation of Dyes in Water

Dye wastewater due to industrialization, urbanization and academic activities has become one of the most important environmental issues today. Photocatalytic degradation technology is considered as a promising technology for treating dye wastewater due to its advantages of environmental protection and low energy consumption. Herein, titanium dioxide–reduced graphene oxide composites (TiO2-RGO) were prepared by a one-step hydrothermal method to degrade different dyes (methyl orange, methylene blue and rhodamine B) in water. The structure and morphology of TiO2-RGO were characterized using various technical approaches. The degradation effect of TiO2-RGO on the dye was in accordance with a first-order kinetic reaction. The degradation rate of TiO2-6%RGO for methyl orange at 15 min was 1.67 times higher than that of TiO2, due to the strong electron transport ability and excellent adsorption properties of graphene. TiO2-6%RGO has better degradation performance for fluorescent dyes and anionic azo dyes. Notably, the degradation rate of methyl orange by TiO2-6%RGO photocatalysis for 90 min could reach 96.9%. Meanwhile, the TiO2-6%RGO showed excellent reusability, as the initial degradation rate of 93.2% was maintained after five degradation cycles of methyl orange solution. The present work provides a universal strategy for designing efficient photocatalytic materials.