Calcination Of Zn Research Articles

ZnO–Al2O3–CeO2–Ce2O3 mixed metal oxides as a promising photocatalyst for methyl orange photocatalytic degradation

In this research article, ZnO–Al2O3–CeO2–Ce2O3 mixed metal oxides phases were prepared by calcination of Zn–Al/Ce–CO3 layered double hydroxides (LDH) precursors, and evaluated for the photocatalytic degradation of methyl orange (MO) as a model textile dye from aqueous solution under UV irradiation. First, Zn–Al–CO3 and a series of Zn–Al/Ce–CO3 with different Ce content (5, 10, 15, 20%) were synthesized through co-precipitation method at Zn/(Al+Ce) molar ratio (r) of 3, then subjected to calcination at 500 °C for 6 h. Samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray analysis and pH point of zero charge. The experimental results of the photodegradation reveal that the photocatalyst developed from Zn–Al–Ce10%-CO3 LDH exhibits the highest photocatalytic activity, with a degradation efficiency of 99.8% after 300 min of irradiation. This performance was mainly ascribed to the presence of difference state of Ce, leading a highest separation efficiency of electrons and holes. The recycling tests suggests a much high photostability and reusability of the photocatalyst.

Photocatalytic degradation of 2,4,6-trinitrotoluene (TNT) in the presence of ZnS, NiS and ZnS/NiS supported Clinoptilolite under UV irradiation: experimental and neural network modelling

ABSTRACT The Photocatalytic degradation of 2,4,6-trinitrotoluene (TNT), catalysed by nanosized ZnS, NiS and ZnS/NiS photocatalysts, was studied under UV irradiation. ZnS, NiS and ZnS/NiS nanoparticles were incorporated onto Iranian natural Clinoptilolite (CP) zeolite by calcination of Zn+2and Ni+2 ion-exchanged Clinoptilolite. The photocatalysts were characterised by the TEM, FT-IR, XRD, DRS, UV-VIS, HPLC and COD methods. The average particle size of different photocatalysts incorporated onto CP was calculated through XRD analyzes between 70–40 µm. The degradation extent of TNT was investigated by UV–Vis spectrophotometry, COD and HPLC. The influence of pH, concentration of TNT in aqueous solution, contact time, amount of photocatalysts and concentration of ion exchange solution on the degradation efficiency has also been studied. After 160 minutes of photocatalytic degradation experiments, the highest degradation (88.5%) was recorded at a concentration of 55 mg.L−1 of TNT and the lowest degradation (37.9%) at pH = 7. It has been revealed that0.075 g ZnS7.1%/NiS2.7%nanoCP (NCP)photocatalyst at pH = 11, with 55 mg.L−1 TNT solution was the optimum parameters of the experiment. A feed-forward Artificial neural network (ANN) was employed to predict the photocatalytic degradation of 2,4,6-trinitrotoluene (TNT)based on a set of experimental tests. The results indicated that the ANN model prediction and experimental data have excellent accordance and the model can be used for prediction of photocatalytic degradation efficiency. The sensitivity analysis revealed that the concentration of TNT has a considerable effect on degradation efficiency (about 26.19%).

Intercalation of (η5‐Pentamethylcyclopentadienyl)trioxomolybdenum(VI) in a Layered Double Hydroxide

A Zn,Al layered double hydroxide (LDH) with [Cp*MoO3]– (Cp* = η5‐C5Me5) anions in the interlayer has been prepared by a direct coprecipitation method. The intercalated LDH and the mixed metal oxide (MMO) obtained after its calcination were characterized by elemental and thermogravimetric analyses, powder X‐ray diffraction (PXRD), FT‐IR and FT‐Raman spectroscopy, 13C and 27Al MAS NMR, and scanning electron microscopy. The observed basal spacing of 17.1 Å for the LDH Zn,Al‐Cp*MoO3 (corresponding to a gallery height of 12.3 Å) suggests that the guest anions self‐assemble into dimers via offset face‐to‐face Cp*···Cp* interactions, which facilitates hydrogen‐bonding interactions between the oxido ligands of the complexes and the layer hydroxyl groups, while positioning the hydrophobic aromatic rings towards the center of the galleries. Calcination of Zn,Al‐Cp*MoO3 at 550 °C under air gave an MMO comprising well‐dispersed ZnO, α‐ZnMoO4 and ZnAl2O4 (spinel) oxides in a molar of ca. 1.4:1.6:1. The MMO exhibited catalytic activity for the epoxidation of cis‐cyclooctene with tert‐butylhydroperoxide (TBHP) as terminal oxidant, with quantitative yield of the epoxide being achieved within 24 h at 85 °C.

Light irradiation enhanced triethylamine gas sensing materials based on ZnO/ZnFe2O4 composites

Light irradiation enhanced ZnO/ZnFe2O4 sensors for triethylamine gas detections have been reported in this paper. ZnO/ZnFe2O4 composites with a hexagonal nanostructure were synthesized by calcination of Zn, Fe layered double hydroxides (Zn2Fe-LDH) at certain temperatures. Focusing on the general problem that the metal oxide gas sensors for triethylamine detection often have high working temperatures around 200°C, the assistance approach of light irradiation has been conducted in our work. Under the light irradiation, the gas sensing measurement indicates that the sample calcined at 600°C shows considerable response to triethylamine at the working temperature of 80°C. For comparison, the introduction of light irradiation has lowered the working temperature markedly, which might have potential to monitor TEA in industrial production in the future.

Preparation of ZnO nanoparticles in a reverse micellar system and their photoluminescence properties

ZnO nanoparticles with spherical morphology and narrow size distribution were obtained by calcination of Zn(OH) 2 nanoparticles, which were prepared in a polyethylene glycol mono-4-nonylphenyl ether (NP-5)/cyclohexane reverse micellar system and incorporated into polyurea (PUA) via an in situ polymerization of hexamethylene diisocyanate (HDI). The resulting ZnO nanoparticles demonstrated a near-UV emission and a green emission, the intensity ratio of which depended on calcination conditions. For the nanoparticles studied, the calcination atmosphere influenced remarkably the photoluminescence properties such as intensity ratio of the near-UV emission to green emission, rather than the size, morphology, and crystallinity of the ZnO nanoparticles. The green emission decreased by calcination in O 2 flow but increased by calcination in N 2 flow, as compared with the case calcined in air flow. This finding suggests that the green emission is enhanced with the increase of the number of oxygen vacancies of the ZnO nanoparticles and thus the photoluminescence properties of the nanoparticles were successfully controlled by the calcination condition, without changing the size and morphology.

Study of the thermal dehydration of Zn 0.5Ca 0.5(H 2PO 4) 2 · 2H 2O

The dehydration and condensation reactions taking place during calcination of Zn 0.5Ca 0.5(H 2PO 4) 2 ·2H 2O have been followed by means of thermal analyses under quasiisothermal-isobaric conditions. Isothermal calcination of the starting binary dihydrogen phosphate has been carried out in an electric oven at various temperatures. The reaction products obtained were analysed by chromatography, IR spectroscopy, X-ray diffraction analysis, electron microscopy and atomic absorption spectroscopy. The compositions of the calcination products were determined by extraction with solutions of inorganic compounds and with organic reagents. The effect of water vapour partial pressure has been monitored on the course, rate, and yield of the condensation reactions and on the formation of the main and a further product, the binary cyclotetraphosphate (tetrametaphosphate) c-ZnCaP 4O 12.

Mechanism of dehydration of Zn 0.5Mg 0.5(H 2PO 4) 2 · 2H 2O

Thermal analyses under non-isothermal and under quasi-isothermal-isobaric conditions were used to follow the condensation reactions proceeding during the calcination of Zn 0.5Mg 0.5 (H 2PO 4) 2 · 2H 2O. Calcination in an electric oven under isothermal conditions was adopted for preparation of the intermediates and the main product, which were analysed by chromatography, IR spectroscopy, NMR spectroscopy, X-ray analysis, electron microscopy, and extraction experiments with solutions of water, acetone and 0.3 M HCl. The effect of water vapour pressure on the course of calcination has been monitored, in terms of the rate and yield of the condensation reactions and the formation of the main product and other products such as the new compound binary cyclotetraphosphate (tetrametaphosphate) ZnMgP 4O 12.