Aqueous Solution Of Zinc Acetate Research Articles

Synthesis of MeOH and DME From CO2 Hydrogenation Over Commercial and Modified Catalysts.

Growing concern about climate change has been driving the search for solutions to mitigate greenhouse gas emissions. In this context, carbon capture and utilization (CCU) technologies have been proposed and developed as a way of giving CO2 a sustainable and economically viable destination. An interesting approach is the conversion of CO2 into valuable chemicals, such as methanol (MeOH) and dimethyl ether (DME), by means of catalytic hydrogenation on Cu-, Zn-, and Al-based catalysts. In this work, three catalysts were tested for the synthesis of MeOH and DME from CO2 using a single fixed-bed reactor. The first one was a commercial CuO/γ-Al2O3; the second one was CuO-ZnO/γ-Al2O3, obtained via incipient wetness impregnation of the first catalyst with an aqueous solution of zinc acetate; and the third one was a CZA catalyst obtained by the coprecipitation method. The samples were characterized by XRD, XRF, and N2 adsorption isotherms. The hydrogenation of CO2 was performed at 25 bar, 230°C, with a H2:CO2 ratio of 3 and space velocity of 1,200 ml (g cat · h)−1 in order to assess the potential of these catalysts in the conversion of CO2 to methanol and dimethyl ether. The catalyst activity was correlated to the adsorption isotherms of each reactant. The main results show that the highest CO2 conversion and the best yield of methanol are obtained with the CZACP catalyst, very likely due to its higher adsorption capacity of H2. In addition, although the presence of zinc oxide reduces the textural properties of the porous catalyst, CZAWI showed higher CO2 conversion than commercial catalyst CuO/γ-Al2O3.

Integrated modifying zinc-containing additive for construction silicate compositions

Sodium silicate binders are a promising binder base for obtaining effective granular thermal insulation materials. Increasing water resistance, first of all, will expand the scope of their application in construction. At the same time, the features of the modification of sodium silicate binders by compounds of polyvalent metals have not been fully studied, the interaction with which leads to the formation of hardly soluble silicates. The purpose of this work was to develop a modifying complex based on a zinc-containing compound - zinc acetate to increase the water resistance and thermal characteristics of the porous granular material. The proposed modifying additive is a complex consisting of zinc acetate and an organic alcohol solvent. It is shown that the properties of porous granular material can be controlled by changing the composition of the zinc acetate solvent. Qualitative and quantitative dependences of the properties of porous granules (strength, water resistance, density, thermal conductivity) on the type of zinc-containing solution and its content in the compositions have been obtained. The concept of the mechanism of formation of sparingly soluble complexes during the modification of sodium silicate binders with zinc-containing aqueous-alcoholic solutions has been developed. X-ray phase analysis showed that the sodium silicate system modified with an aqueous alcohol solution of zinc acetate, in contrast to an aqueous solution of zinc acetate, is completely in an amorphous state. We believe that compounds of the Zn2SiO4H2O, ZnSiO3 type are in the amorphous state. The obtained research results made it possible to determine the rational composition of granular heat-insulating material with increased operational and functional characteristics (ρ = 200-280 kg / m3, λ = 0.052-0.063 W / (m °C), R = 1.3-1.8 MPa, Kr = 0.89-0.92, W = 16- 18 %).

In Ukrainian

The aim of the work was to synthesize nanocomposites based on pyrogenic silica and zinc phosphate by a simple method without using a large amount of solvent and to study the characteristics and properties of the obtained materials. The dual systems of zinc phosphate/pyrogenic silica with the different ratio of components were synthesized via mechanical grinding in a porcelain drum ball mill of fumed silica (Orysyl A-380), zinc acetate (Zn(CH3COO)2·2H2O) and phosphoric acid with distilled water, followed by air-drying in an oven at 125 °C (2 h) and calcination in a muffle oven at 450 °C for 2 h. The zinc phosphate content was 0.1, 0.2, and 0.3 mmol per 1 g of SiO2. The control sample (ZP-K) was synthesized by thermal treatment of the precipitate, formed after mixing on a magnetic stirrer an aqueous solution of zinc acetate with the addition dropwise of phosphoric acid, without the use of SiO2. X-ray diffraction studies of the nanocomposites confirmed the formation of the crystalline phase of Zn3(PO4)2·4H2O (orthorhombic modification) both in the silica-containing and control ZP-K samples after air drying at 125 °C, while heat treatment at 450 °C leaded to the formation of the anhydrous monoclinic Zn3(PO4)2 phase. The content of the zinc phosphate in the dual composites was 0.1, 0.2, and 0.3 mmol per 1 g of SiO2. The IR spectra of the nanocomposites indicated the presence of absorption bands in the range of 3760-3600 cm-1, which were attributed to the unequal structural ‒OH groups of silicon and phosphorus atoms. It was found that the presence of zinc phosphate on the SiO2 surface does not cause the chemical interaction with silica during heat treatment of composites in air even at 900-1000 °C. It was shown that the ability of Zn3(PO4)2/SiO2 composites to adsorb water vapor decreases with increasing amount of modifying compound. The effect of the obtained phosphorus-containing nanocomposite on the thermal stability of an alkyd polymer matrix was considered.

In Situ Synthesis of ZnO Nanorods/Graphene Oxide Composite and Its Photocatalytic Property.

Graphene oxide (GO) was firstly synthesized from natural graphite powders based on a modified Hummers' method, and then large area GO film was formed by a self-assembly mechanism. Zinc oxide (ZnO) nanorods array was synthesized on the GO film using a facile hydrothermal method in an aqueous solution of zinc acetate [Zn(CH₃COO)₂·2H₂O] and hexamethylenetetramine (C6H12N₄) to form the ZnO nanorods/GO composite. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectrum and X-ray diffractometer (XRD). The photocatalytic activity of the ZnO nanorods/GO composite was investigated using the methylene blue (MB) in aqueous solution under ultraviolet (UV) light irradiation. It was indicated that the ZnO nanorods/GO composite exhibited significantly better photocatalytic property, which can be attributed to the high specific surface of the ZnO nanorods, the enhanced light absorption of the composite and the strong decrease in charge carrier recombinations originating from the association of ZnO nanorods with GO film.

Synthesis of ZnS nanoparticles of required size by precipitation in aerosol microdroplets

ABSTRACTZinc sulphide (ZnS) nanoparticles were prepared by an aerosol method from zinc acetate and sodium sulphide (Na2S) aqueous solutions. Aqueous solution of zinc acetate was dispersed into the form of microdroplets, which were introduced by airflow to vigorously stirred aqueous solution of Na2S, which was in excess. Microdroplets served as microreactors, so the reaction took place only in limited volume. Particle size distribution was studied by transmission electron microscopy and by dynamic light scattering measurements. In this work, the equation that allows us to predict the final size distribution of ZnS nanoparticles using exact concentration of zinc acetate was derived and ZnS nanoparticles with predicted mean particle diameter around 50 and 70 nm were successfully synthetised.

ZnO Nanoclusters Supported on Dealuminated Zeolite β as a Novel Catalyst for Direct Dehydrogenation of Propane to Propylene

AbstractSmall ZnO nanoclusters supported on dealuminated β zeolite were prepared and evaluated for catalyzing direct dehydrogenation of propane to propylene (PDH), exhibiting high catalytic performance. N2 sorption, XRD, TEM, 27Al and 28Si MAS NMR, IR, XRF, DR UV‐vis, XPS, and NH3‐TPD techniques were employed to characterize the physicochemical properties of this novel catalyst system. It is found that the Zn species can be accommodated in the vacant T‐atom sites of dealuminated β zeolite due to the reaction of aqueous zinc acetate solution with silanol groups, and thus, producing massive small ZnO nanoclusters as active phases in PDH. Additionally, dealuminated β zeolite can greatly depress side reactions attributable to the absence of strong acid sites, thereby guaranteeing high catalytic activity, propylene selectivity and stability. As a result, the optimal catalyst of 10 wt% Zn loaded on dealuminated β zeolite exhibits a high initial propane conversion of around 53 % and a superior propylene selectivity of about 93 % at a space velocity of 4000 cm3 gcat−1 h−1, together with the high stability and satisfactory reusability. This study may open a new way to design and synthesize highly active PDH catalysts with high selectivity and stability.

Growth of ZnS Thin Films using Chemical Spray Pyrolysis Technique

Abstract It is well acknowledged that thin films of zinc sulfide (ZnS) can be successfully synthesised via spray pyrolysis of an aqueous solution of zinc acetate and thiourea onto a glass substrate at a temperature of 200°C. However, the effect of spray rate on the structural and optical properties of ZnS thin films has not been considered deeply. Therefore, this study synthesized ZnS thin films on glass substrates under different spray rate (1, 2, 3 and 4 mlmin-1). The films were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis-NIR spectrometry, and photoluminescence (PL) spectroscopy. The X-ray diffraction of all the samples confirmed the characteristic cubic structure of ZnS thin films. On the other hand, the morphology and crystallinity seemed to be depended on the spray rate. It was found that the value of bandgap of ZnS films slightly increased when the spray rate was increased. Furthermore, the variations observed in the 3.35–3.80 eV range are most likely related to the Zn (S, O) formation within the solid solution. PL analysis specified the presence three peaks (2.38, 2.98 and 3.5 eV) at spray rate of 3 ml min-1, which are attributable to Zn vacancies, S vacancies, interstitial sulfur and interstitial zinc.

Mechanical strength of cold-sintered zinc oxide under biaxial bending

Zinc oxide is densified to 97% by the cold sintering process using an aqueous zinc acetate solution as the secondary transport phase. The mechanical response of the cold-sintered zinc oxide ceramics is investigated through the ball-on-three-balls biaxial bending technique. The analysis demonstrates that ZnO cold-sintered samples follow a Weibull distribution with a characteristic strength (σ0 ~ 65 MPa) and Weibull modulus (m ~ 8). Phase purity and residual secondary phases were analyzed via X-ray diffraction and Raman spectroscopy. This report provides an initial demonstration of the mechanical properties of cold-sintered parts in the as-pressed and unmodified state and serves for comparison with conventionally prepared ceramics.

Sol-gel synthesis and characterization of ZnAl2O4 powders for transparent ceramics

The sol-gel synthesis of ZnAl2O4 ceramic powders from alkoxide and acetate sources of metals, as well as the microstucture and the hardness of the hot-pressed ZnAl2O4 specimens were considered. ZnAl2O4 powders were prepared by the hydrolysis of an alcohol solution of aluminium isopropoxide using an aqueous solution of zinc acetate followed by heat treatment. The thermal evolution of the ZnAl2O4 precursor was investigated. The effect of calcination temperature on the morphology and the specific surface area of ZnAl2O4 powders were also studied. The sintering of the resultant powders to the high transparent ceramic using a hot pressing with 1 wt% ZnF2, as a sintering additive was successfully demonstrated. The in-line transmittance of ZnAl2O4 ceramics (1 mm thickness) achieved 80% in the visible region and 85% at 5 µm; Vickers hardness was 11.6 GPa.

Reversible CO2 capture by ZnO slurry leading to formation of fine ZnO particles

ZnO powders were synthesized by heating precursors, prepared by the addition of ethylene diamine tetraacetate to an aqueous solution of zinc acetate, at 500 °C in air. A ZnO slurry was prepared by adding distilled water to the synthesized ZnO powder. X-ray diffraction studies confirmed that the ZnO slurry adsorbed CO2 at 25 °C under a CO2 gas flow to produce Zn5(CO3)2(OH)6. The CO2 adsorption ratio of the ZnO slurry was influenced by the amount of added water. When the weight ratio of water/ZnO was 1, the ZnO slurry had the largest CO2 adsorption ratio. Scanning electron microscopy and thermal gravimetry showed that the plate-like Zn5(CO3)2(OH)6 particles thermally decomposed at 300 °C in air leading to a single-phase ZnO powder consisting of nanoparticles with approximately 20 nm in diameter. The specific surface area of the reformed ZnO powder increased to approximately 82 m2/g through the thermal decomposition of Zn5(CO3)2(OH)6. The ZnO slurry was capable of adsorbing CO2 under a CO2 flow at 25 °C and desorbing CO2 under an air flow at 300 °C. The CO2 adsorption ratio of the ZnO slurry reached 80%–90% at 25 °C even after the fifth CO2 adsorption and desorption cycle.

Facile method to immobilize ZnO particles on glass spheres for the photocatalytic treatment of tannery wastewater

In order to apply the photocatalytic processes on a real scale for the treatment of industrial wastewaters, the use of slurry reactors employing suspended photocatalysts is not suitable due to the need for an uncomfortable and expensive separation phase of photocatalyst. To overcome this disadvantage, the photocatalyst particles must be immobilized on a transparent support: our work proposes, for this reason, a simple and cost effective method for the deposition of ZnO photocatalyst on glass spheres in order to formulate a structured photocatalyst effective in the treatment of aqueous solutions containing various organic dyes, commonly used in the tannery industries and in the treatment of a real wastewater at high COD content (11 g/L) coming from the refining unit of the tanning process. In particular, ZnO was immobilized on glass spheres (ZnO/GS) with a simple dip coating method, starting from zinc acetate aqueous solution, without using complexing agent and strong basic compounds. The optimization of ZnO amount on glass spheres was evaluated employing Acid Blue 7 dye, as model pollutant. In particular, it was found that best performances in terms of discoloration and mineralization of the target dye were obtained using the photocatalyst with a ZnO loading equal to 0.19 wt% (ZnO_ac1), prepared through only one dip-coating step. Moreover, the ZnO_ac1 photocatalyst can be easily separated from the reaction mixture, maintaining excellent photocatalytic activity and durability even after several reuse cycles. Finally, ZnO_ac1 showed a high photocatalytic activity in the treatment of the real wastewater, obtaining a COD removal equal to 70% after 180 min of UV light irradiation.

Synthesis of ZnO nanoparticles from water-in-oil (w/o) microemulsions

Water-in-oil, w/o, microemulsions, human and environmentally friendly, were used to synthesize zinc oxide, ZnO, nanopowders based on a simple process. The synthesis route consisted in using w/o microemulsions, where the continuous phase was emu oil, whereas the discontinuous phase was a 0.5 M zinc acetate aqueous solution, both stabilized by a layer of surfactant molecules of a 1:1 Span 80 and Tween 80 mixture. The precipitation is reached with the addition of a 1.0 M aqueous solution of sodium hydroxide. The resultant precipitates were dried at 100 °C in air and then calcined at 800 °C during 2 h. The procedure allowed the obtaining of nanoparticles with an average size of around 31.2 nm, with reduced polydispersity and pseudo-spherical morphology. The zinc oxide powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, confirming the hexagonal wurtzite phase of ZnO.

Bulk Heterojunction Solar Cell Devices Prepared with Composites of Conjugated Polymer and Zinc Oxide Nanorods

ZnO nanorods (Nrods) with ~20–50 nm lengths were synthesized using an aqueous solution of zinc acetate and glacial acetic acid. Bulk heterojunction solar cells were fabricated with the structure of indium tin oxide (ITO)/polyethylenedioxythiophene doped with polystyrene-sulfonic acid (PEDOT:PSS)/ZnO-Nrods + polymer/electron transport layer (ETL)/Al. Current density-voltage characterization of the resulting cells showed that, by adding an ETL and using polymers with a low band gap energy, the photoactive layer surface morphology and the device performance can be dramatically improved.

Bio-medically active zinc oxide nanoparticles synthesized by using extremophilic actinobacterium, Streptomyces sp. (MA30) and its characterization

The present study describes the synthesis of zinc oxide nanoparticles (ZnO-NPs) using an extremophilic actinobacterial cell-free extract, supplied with aqueous zinc acetate solution. Crystalline nature, morphological features, and polydispersed nanoparticles size (15–30 nm) were identified by X-ray diffraction (XRD), atomic force and electron microscopic analysis with dynamic light scattering (DLS) study. The interaction between biomolecules and ZnO-NPs was analyzed using Fourier transform infra-red spectroscopy (FT-IR). Furthermore antibacterial, antioxidant activities, and cell viability test of ZnO-NPs were systematically evaluated. The present study opens a new avenue for the actinobacterial synthesis of oxide nanoparticles.

Influence of the spray distance to substrate on optical properties of chemically sprayed ZnS thin films

In this study, zinc sulfide (ZnS) nanostructures with different morphologies were effectively fabricated on glass substrates at 200 °C via spray pyrolysis. The Zn2+ and S2− ions were sourced from aqueous solutions of zinc acetate and thiourea, respectively. The samples were deposited at different spray distances (15, 20, 25, 30 and 35 cm) in order to examine the effect of spray distance on the optical and structure properties of synthesized ZnS nanostructures. Following the deposition procedure, the films were characterized using X-ray diffraction, UV–Vis–NIR spectrometry, photoluminescence (PL) spectroscopy and field emission scanning electron microscopy. The crystallinity and morphology of the cubic ZnS films were found to vary with spray distance, where the average particle size appears to increase with the increasing spray distance. The highest absorption values were obtained for ZnS films crystallized at a spray distance of 30 cm. The PL analysis specified the presence of violet and green emissions, which are attributable to Zn and S vacancies. The band gap of the ZnS films was observed to decrease slightly from 3.82 to 3.30 eV with the increasing spray distance. The results indicate that the spraying distance affects the characteristics of ZnS nanostructures.

Nanostructured ZnO thin film with improved optical and electrochemical properties prepared by hydrothermal electrochemical deposition technique

Zinc oxide (ZnO) thin films were grown on fluorine-doped tin oxide coated glass substrate by the hydrothermal electrochemical deposition (HTED) route using slightly acidic aqueous zinc acetate solution at 80°C and were characterised by various techniques. The deposited films showed n-type behaviour with improved carrier concentration. The steady state photocurrent densities were found to be 0.4 mA/cm2 (under UV irradiation) and 8 µA/cm2 (under visible light illumination) at zero bias potential. Significant improvement of optical, electrochemical and photoelectrochemical properties of deposited films could be achieved using HTED technique.

Efficiency Enhancement of ZnO Nanocrystalline Dye-Sensitized Solar Cells by Post-Treatment

In this paper, ZnO nanocrystalline photoanodes were treated by zinc acetate aqueous solution. The effect of surface chemical modification processing on the photovoltaic performance and electrochemical properties of ZnO nanocrystalline dye-sensitized solar cells (DSSCs) were studied systematically. The SEM results revealed that the surface of the ZnO photoanode films were rough and some aggregations were formed after the surface chemical modification processing. The number of aggregations increased with increasing processing time, and showed wide grain size distribution simultaneously, which effectively increased the light scattering and decreased the grain boundaries to suppress the electron recombination. Moreover, the surface of these photoanode films were filled with micropores, which was benefit to the infiltration of electrolyte solution. The short circuit current density increased from 7.20 mA•cm-2 to 8.61 mA • cm-2 when post-treatment 20 min, and the maximum energy conversion efficiency reached 3.61%, which enhanced 43% compared with that without post-treatment.

(Invited) Metalation of Porphyrins on Surfaces in Liquid and Vacuum

Adsorption and metalation of porphyrins on metal single-crystal surfaces under ultrahigh vacuum has been studied extensively, but less is known about the adsorption behavior of porphyrins on oxide surfaces. On metal surfaces porphyrin molecules will react with coadsorbed metal atoms or the surface itself, producing the metalated molecules and coadsorbed hydrogen atoms, which subsequently combine and desorb as hydrogen molecules. Examples will be given of 5,10,15,20-tetraphenylporphyrin (2HTPP) on Cu(111). A similar reaction is also possible for oxide surfaces. As 2HTPP is adsorbed on MgO an ion-exchange reaction happens already at room temperature and the two aminic protons of the porphyrin molecule are exchanged with a Mg2+ ion from the oxide surface, producing MgTPP and, locally, Mg(OH)2. Examples will be given of adsorption on both single-crystal MgO(100) substrates and nanostructured powders. Examples will also be given of metalation of 2HTPP adsorbed on a Au(111) surface immersed in an aqueous zinc acetate solution, metal-exchange reactions with Cu2+ and unsuccessful attempts to demetalate the adsorbed metalloporphyrins in acidic solutions.

ELECTRODEPOSITION OF ZnO NANOROD ARRAYS FOR APPLICATION IN PEROVSKITE BASED SOLAR CELLS

We report a low-cost, free-hole conductor methylammonium lead iodide CH3NH3PbI3 (perovskite)/ZnO nanorods (NR) heterojunction solar cell. ZnO nanorod arrays were obtained electrochemically onto transparent conducting oxide (fluor doped tin oxide, FTO) from an aqueous solution of zinc acetate. The ZnO NR were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical transmittance. Solar cell was fabricated forming the perovskite material onto the ZnO thin film. Spin coating of an equimolar mixture of CH3NH3I and PbI2 in γ-butyrolactone solution (perovskite precursor solution) leads to CH3NH3PbI3 formation on ZnO NR. A graphite-covered FTO/glass was used as a back contact. The photovoltaic performance of the solar cell was characterized at full sun intensity of 100 mW/cm2 obtaining a shortcircuit current of 1.5 mA/cm2, an open circuit voltage of 0.47 V and energy conversion efficiency of 0.16 %.

Influence of surface modification of zinc oxide nanoparticles on thermal behavior and hydrophilic property of PET–PEG composites

Zinc oxide (ZnO) nanoparticles were successfully prepared by a one‐step precipitation reaction in an aqueous solution of zinc acetate and sodium hydroxide with stearic acid (SA) as the modifying agent. Hydrophilic composites of poly(ethylene terephthalate) (PET), poly(ethylene glycol), and ZnO nanoparticles were prepared further by in situ polymerization. The surface modification of ZnO and the microstructure and properties of prepared nanoparticles were investigated by relative contact angle measurements (CA), Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy, and thermogravimetric analysis (TGA). Measurements of CA and XRD indicated that the surface‐treated ZnO was hydrophobic and had a significant improvement in crystallinity with SA. Compared with the nanocomposites filled with the pure ZnO, the modified ZnO exhibits a better dispersion in PET–PEG matrix. TGA results showed that the presence of modified ZnO nanoparticles can improve the thermal stability of PET–PEG matrix. CA and low field nuclear magnetic resonance methods were used to investigate the hydrophilic behavior of nanocomposites. The results revealed that modified nanoparticles had a positive effect on the bound water absorption. A simple model for the interactions between ZnO, SA, and PET–PEG matrix was proposed. POLYM. COMPOS., 37:1830–1838, 2016. © 2015 Society of Plastics Engineers