Supported ZnO Nanoparticles Research Articles

Three-Dimensional Porous ZnO-Supported Carbon Fiber Aerogel with Synergistic Effects of Adsorption and Photocatalysis for Organics Removal

A three-dimensional (3D) ZnO-supported carbon fiber aerogel (ZnO/CFA) was successfully prepared by using natural cotton with hydrophilicity as the precursor. The facile synthetic strategy includes two steps: Zn2+ exchange on the surface of cotton and thermal treatment at high temperatures. Particularly, the calcination temperature was found to greatly affect the content, dispersity, and size of supported ZnO nanoparticles, and the product obtained at 600 °C (ZnO/CFA-600) exhibited both high ZnO loading and well-dispersed ZnO nanoparticles. Therefore, ZnO/CFA-600 has superior photocatalytic activity for tetracycline (TC) degradation under UV light irradiation compared with others. Additionally, the unique 3D crosslinking network inside the ZnO/CFA generates an open channel for the rapid migration and diffusion of reactants and products. In a dynamical water-treated system, the 3D porous ZnO/CFA-600 continuously works for TC removal without any separation operation and maintains high synergistic performance of adsorption and photocatalysis for at least 8 h. Consequently, the 3D porous ZnO/CFA product, with its large adsorbability and high photoactivity, shows a lot of industrial potential in wastewater treatments.

Photocatalytic degradation of aqueous methylene blue using ca-alginate supported ZnO nanoparticles: point of zero charge role in adsorption and photodegradation.

A novel insoluble Ca-Alginate created from soluble Na-Alginate was used as a support substrate for ZnO nanoparticles producing ZnO@Ca-Alginate composite photocatalyst. Fourier Transform Infrared (FT-IR), Ultraviolet-Visible (UV-Vis), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD) analysis techniques were used in the characterization of the prepared ZnO@Ca-Alginate. The ZnO@Ca-Alginate was tested for its potential use in the photodegradation of Methylene Blue (MB) from an aqueous solution under solar-simulated light. This composite photocatalyst efficiency in MB removal was compared with naked ZnO potential considering different conditions and parameters (e.g. pH, MB concentration, amount of photocatalyst, and irradiation time). The MB concentrations were identified using UV-vis spectrophotometric methods. While, high-performance liquid chromatography (HPLC), Total organic carbon (TOC) analysis, and other elemental analyses were used to confirm the MB complete mineralization. The MB photodegradation results were performed by using UV-vis analysis., the results showed that up to 95% of MB (40 mL, 40 ppm) was removed within 30 min of irradiation using either ZnO@Ca-Alginate or naked ZnO. The pH and the zero-charge point (Pzc) values play a main role in the adsorption and photodegradation results. The Pzc values for Ca-Alginate, ZnO, and Zn@Ca-Alginate were 6.5, 8.8, and 6.8 respectively. The prepared composite catalyst showed a maximum adsorption and photodegradation in a basic to slightly basic medium, the MB completely removed at pH of 7.7 within an hour of irradiation. The complete miniralzation of MB at the end of the photodegrdation process was confirmed. Here it is proved that the ZnO@Ca-Alginate photocatalyst can be recovered and reused without any significant decrease in its effectiveness.

Preparation and characterization of zinc oxide nanoparticles supported on reduced graphene oxide and using as an effective catalyst for synthesis of l,4‐dihydropyrimidinones under solvent‐free conditions

AbstractIn this research, it was presented a simple and easy method for the preparation of graphene oxide (GO) supported ZnO nanoparticles with low cost, available precursor and their application as nanocatalyst for synthesis of l,4‐dihydropyirimidinones. When GO combines with metal oxide nanoparticles such as ZnO shows very good properties. There is a wide range of chemical methods for the attachment of various functional groups. In this protocol, the GO was synthesized through Hummer's method. The structure and morphology properties of ZnO NPs@rGO nanocomposite were investigated by Fourier‐transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscope techniques. Also, the organic compounds were identified by melting point, FT‐IR, and proton nuclear magnetic resonance analyses.

Photo-catalytic Study of Malachite Green Dye Degradation Using Rice Straw Extracted Activated Carbon Supported ZnO Nano-particles

Objective: ZnO nanoparticles were synthesized using wet impregnation method, and activated carbon from rice straw (RS) prepared through chemical route. Methods: The nano-composites ZnO-AC series were prepared with different ZnO:AC ratio of 10, 20, 50, and 70% to optimize the zinc oxide nanoparticles used. The obtained composites were characterized by FE-SEM, XRD, SBET, and optical techniques then used for the photo-degradation of Malachite green dye (MG) under visible light. Results: It was found that 10ZnO-AC exhibited excellent visible light photo-catalytic performance. The ·OH radicals’ formation is matching with photo-activity of the prepared composites. The photo-degradation efficiency of MG increased from 63% to 93%, when the 10ZnO-AC photocatalyst amount was increased from 0.5 to 6 g/L. Conclusion: The GC-MS technique was used to analyze the intermediates formed; up to 15 kinds of chemicals were identified as the degradation products.

Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size.

This study addresses the relationship between material morphology (size, growth parameters and interfaces) and optical emissions in ZnO through an experimental approach, including the effect of different material dimensions from bulk to nano-size, and different excitations, from optical sources to ionizing radiation. Silica supported ZnO nanoparticles and ligand capped ZnO nanoparticles are synthesized through a sol–gel process and hot injection method, respectively. Their optical properties are investigated by radioluminescence, steady-state and time-resolved photoluminescence, and compared to those of commercial micrometric powders and of a bulk single crystal. The Gaussian spectral reconstruction of all emission spectra highlights the occurrence of the same emission bands for all samples, comprising one ultraviolet excitonic peak and four visible defect-related components, whose relative intensities and time dynamics vary with the material parameters and the measurement conditions. The results demonstrate that a wide range of color outputs can be obtained by tuning synthesis conditions and size of pure ZnO nanoparticles, with favorable consequences for the engineering of optical devices based on this material.

Raw clay supported ZnO nanoparticles in photodegradation of 2-chlorophenol under direct solar radiations

Abstract Advanced oxidation process of the water organic contaminants is among the promising technologies for water purification. In this work, ZnO nanoparticles have been supported on natural clay particles. The prepared composite ZnO/Clay has been characterized by solid state electronic absorption spectra, X-ray diffraction and scanning electronic microscopy. It is used in photodegradation of aqueous 2-chlorophenole (2-CP) with direct solar radiation. As the catalyst surface charge and point of zero charge presumably influence adsorption uptake and photodegradation of the 2-CP molecules, these two properties have been studied here. For the composite, the optimal contaminant adsorption pH is 8.7, which is the optimal photodegradation value as well. The composite ZnO/Clay shows higher adsorption and photodegradation efficiency in 2-CP degradation compared to naked ZnO. This highlights the future practicality of using this composite catalyst under various natural conditions. Moreover, the ZnO/Clay can be easily recovered and reused for third cycle with no significant loss of efficiency. Complete mineralization of the 2-CP has been confirmed after enough time (2 h). This has been manifested by analysis for remaining organic materials inside the reaction mixture, using UV-visible spectra, high performance liquid chromatography and total organic carbon measurements.

Comments on “Enhanced removal of Cr(VӀ) from aqueous solution by supported ZnO nanoparticles on biochar derived from waste water hyacinth”

A mistake of using pseudo-first-order kinetic equation for testing kinetic parameters of adsorption has been pointed out, as well as inappropriate citations for the adsorption kinetic models. Further, this discussion gives a correct pseudo-first-order kinetic equation and makes a suggestion for citing the original papers for the pseudo-second-order and intra-particle diffusion kinetic equations.

Enhanced removal of Cr(VI) from aqueous solution by supported ZnO nanoparticles on biochar derived from waste water hyacinth

Biochar derived from waste water hyacinth was prepared and modified by ZnO nanoparticles for Cr(VI) removal from aqueous solution with the aim of Cr(VI) removal and management of waste biomass. The effect of carbonization temperature (500–800 °C), ZnO content (10–50 wt%) loaded on biochar and contact time (0.17–14 h) on the Cr(VI) removal were investigated. It was found that higher than 95% removal efficiency of Cr(VI) can be achieved with the biochar loaded 30 wt% ZnO. The adsorption kinetics of the sorbent is consistent with the pseudo-second-order kinetic model and adsorption isotherm follows the Langmuir model with maximum adsorption capacity of 43.48 mg g−1 for Cr(VI). Multiple techniques such as XRD, XPS, SEM, EDX and FT-IR were performed to investigate the possible mechanisms involved in the Cr (VI) adsorption. The results show that there is precipitation between chromium ions and Zn oxide. Furthermore, the ZnO nanoparticles acts as photo-catalyst to generate photo-generated electrons to enhance the reduction of Cr(VI) to Cr(III). The as-prepared ZnO/BC possess good recyclability and the removal ratio remained at about 70% in the fifth cycle, which suggests that both contaminants removal and effective management of water hyacinth can be achieved by the approach.

Titania versus zinc oxide nanoparticles on mesoporous silica supports as photocatalysts for removal of dyes from wastewater at neutral pH

For the photocatalytic wastewater treatment containing lower concentrations of dyes as pollutants, a suitable photocatalyst may be selected for anionic or cationic dye removal according to the photocatalyst surface charging and desired adsorption/degradation ratio. Herein, for the first time, we evaluate mesoporous silica supported TiO2 versus mesoporous silica supported ZnO photocatalysts at neutral pH and at equal conditions. The evaluation shows that model anionic dye Reactive Blue 19 (RB19) was adsorbed onto silica supported ZnO nanoparticles at neutral pH in a much higher rate than on silica supported TiO2 nanoparticles, even though the surfaces of ZnO and TiO2–silica composite catalysts were negatively charged in both cases (ca. −20mV of zeta potential). This was ascribed to the strong positive zeta potential of pure ZnO nanoparticles at neutral pH value (ca. +37mV) and consequently to more mixed oxide (spinel-like) ZnO/silica composite behaviour if compared to the physical mixture of oxide TiO2/silica composites. The highest dye adsorption (50%) and the fastest dye degradation (kapp=0.0544min−1 at 25°C) was observed on disordered ZnO/silica with Zn:Si molar ratio 1:1. Pure TiO2 or silica supported TiO2 nanoparticles were stable under UV irradiation. On the other hand, the interaction between SiO2 and ZnO resulted in increased resistance of ZnO to photocorrosion, which was proven to be an issue in pure ZnO nanoparticles.

Supported Zinc Oxide Photocatalyst for Decolorization and Mineralization of Orange G Dye Wastewater under UV365 Irradiation

To solve the environmental challenge of textile wastewater, a UV/ZnO photocatalytic system was proposed. The objective of this study was to prepare a photocatalytic system by utilizing both cold cathode fluorescent light (CCFL) UV irradiation and steel mesh supported ZnO nanoparticles in a closed reactor for the degradation of azo dye C.I. Orange G (OG). Various operating parameters such as reaction time, preparation temperature, mixing speed, ZnO dosage, UV intensity, pH, initial dye concentration, and service duration were studied. Results presented efficient color and total organic carbon (TOC) removal of the OG azo dye by the designed photocatalytic system. The optimal ZnO dosage for color removal was 60 g m−2. An alkaline pH of 11.0 was sufficient for photocatalytic decolorization and mineralization. The rate of color removal decreased with the increase in the initial dye concentration. However, the rate of color removal increased with the increase in the UV intensity. The steel mesh supported ZnO can be used repeatedly over 10 times without losing the color removal efficiency for 120 min reaction time. Results of Fourier transform infrared (FTIR) and ion chromatography (IC) indicated the breakage of N=N bonds and formation of sulfate, nitrate, and nitrite as the major and minor products. The observation indicated degradation of dye molecules.

Decolorization of C.I. Basic Yellow 28 solution using supported ZnO nanoparticles coupled with photoelectro-Fenton process

The advanced oxidation processes (AOPs), which can produce oxidizing hydroxyl radicals ( OH ) have been proven to be an efficient method for degradation of the dyes. In this work, the decolorization of a dye solution containing C.I. Basic Yellow 28 (BY28) was performed by photoelectro-Fenton (PEF) combined with photocatalytic process. Carbon nanotube–polytetrafluoroethylene (CNT–PTFE) electrode was used as cathode. The investigated photocatalyst was ZnO nanoparticles having specific surface area (BET) 32.23 m 2/g, and mean crystal size 15 nm immobilized on glass plates. A comparison of ultraviolet-C (UV-C), Electro-Fenton (EF), UV/ZnO, PEF and PEF/ZnO processes for decolorization of BY28 solution was performed. Results revealed that color removal efficiency follows the decreasing order: PEF/ZnO > PEF > UV/ZnO > EF > UV-C. The influence of the basic operational parameters including initial dye concentration, applied current, initial pH of the solution, initial Fe 3+ concentration and kind of UV light on the decolorization efficiency of BY28 was studied. The mineralization of the dye was investigated by total organic carbon (TOC) measurements that showed 94.7% mineralization of 20 mg/l dye at 6 h using PEF/ZnO process. Furthermore, identity of the produced intermediates in the course of mineralization was assessed exploiting gas chromatography–mass spectrometry (GC–MS) analysis.

Chemical Characterization of Mesoporous Material Supported ZnO Nanoparticles for Hydrogen Sulfide Capture from Gas Streams

A series of zinc oxide-modified mesoporous SBA-15 materials were synthesized. The desulphurization test with a gas mixture containing 0.1 vol % hydrogen sulfide was carried out on these materials. Materials before and after the desulphurization test were analyzed using a variety of characterization techniques. The results suggest that zinc oxide modification can accelerate the transformation from a mesoporous to a zeolitic phase. The sample with the zinc content higher than 15.5 wt % shows the highest hydrogen sulfide breakthrough capacity up to 177.3 mg S/g.

Synthesis and characterization of ZnO/MgO solids prepared by deposition of preformed colloidal ZnO nanoparticles

The ZnO/MgO solids were prepared by colloidal technique which involves the deposition of preformed colloidal ZnO nanoparticles on magnesia. The morphology of ZnO nanoparticles was investigated by transmission electron microscopy and UV–Vis absorption and diffuse reflectance spectroscopy. We found a good agreement between the average radius and the particle size distribution of the ZnO nanoparticles obtained by both methods. It was shown the ability to control the size of the supported ZnO nanoparticles (3.8–4.4nm) by varying pH of the colloidal solution.