Hydrolysis Precipitation Method Research Articles

Low temperature preparation of Cr-doped rutile pigments with good colour properties

Abstract Cr-doped rutile pigments were prepared by calcination of doped rutile precursors resulting from the hydrolysis-precipitation method. The pigment properties were investigated by X-ray diffraction, Thermogravimetry–differential scanning calorimetry, scanning electron microscopy, energy dispersive spectroscopy, diffuse reflection spectroscopy, Raman spectroscopy, and colourimetry. The pigments were found to have a rutile phase composition. Rutile pigments with good colour properties can be acquired by calcination from 500 °C to 900 °C. The pigment with 1.25% dopant and calcination at 700 °C presented optimal colour properties (L* = 75.46, a* = 15.24, b* = 39.46). The pigments presented high dispersion and could be dispersed directly into polyurethane paint and polyurethane epoxy resin without further modification.

Preparation of Fly Ash Hollow Glass Bead/Titanium Dioxide Composites by Chemical Precipitation

To obtain a kind of composite particles material which has the property of both fly ash glass beads (FA) and titanium dioxide (TD), chemical hydrolysis precipitation method was adopted. Each process condition was investigated and the results were characterized by titanyl sulfate hydrolysis rate and the effect of FA coated TD. Composite structure and properties were characterized by means of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and testing physical properties of FA/TD. The results show that the surface of FA has been coated with TD uniformly and compactly after titanyl sulfate hydrolysis and cladding content roasted. The optimal preparation conditions are hydrolysis cladding temperature 100°C, time 180min, matrix slurry concentration 0.5%, titanyl sulfate solution dosage 0.5g/g and titanyl sulfate solution drop way for the graded way. The hiding power and whiteness of the composite powder are respectively 35.47 g/m2 and 54.43. The results also show that the composite powder has similar pigment performances with TD and it is much whiter than material.

Preparation of Nano-Sized TiO<sub>2</sub> Supported on Granular Activated Carbon and the Photocatalytic Degradation of Methylene Blue

nanosized TiO2 were prepared using TiOSO4 as the precursor by hydrolysis-precipitation and hydrothermal method. Through dipping granular activated carbon (GAC) into the TiO2 hydrosols, The nanosized TiO2/GACs composite was obtained. The surface morphology, microstructure and element distribution of the composite were characterized by TEM, SEM, XRD, EDS respectively. The results show that the synthesized nanosized TiO2 is anatase phase with average size of 150-200 nm and can be dispersed uniformly on the surface of GACs. Photocatalytic experimental shows that when the load amount is 1.5%, the nanosized TiO2/GACs composite have the best effect of removal methylene blue,the rate up to 97.0 % in 180 min.

Characterization and mechanism analysis of Mo–N-co-doped TiO2 nano-photocatalyst and its enhanced visible activity

In this study, Mo–N-co-doped TiO2 nano-photocatalysts have been synthesized through hydrolysis-precipitation method, combined with sonication posttreatment. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). XRD showed that co-doping with Mo and N favored the formation of anatase and retarded the growth of crystallite size. XPS revealed that N was incorporated into the lattice of TiO2 through substituting oxygen atoms and coexisted in the forms of β-N and γ-N in co-doped TiO2. Meanwhile, Mo was also incorporated into the lattice of TiO2 through substituting titanium atoms and existed in the form of Mo6+. DRS indicated that the light absorbance in visible region was improved by co-doping with Mo and N, leading to a narrower band gap and higher visible light photocatalytic activity for the degradation of phenol than that of pure and N-doped TiO2. The enhanced visible light photocatalytic activity of Mo–N-co-doped TiO2 nano-photocatalyst was attributed to the small crystallite size, narrow band gap and intense light absorbance in visible region. This study provides a new method to synthesize visible light active TiO2-based photocatalyst.

Preparation of Nano-TiO<sub>2</sub>/Fly Ash Beads Composite Material and Photocatalytic Properties

Using TiCl4 as the titanium source, urea as the precipitating agent, nano-TiO2/fly ash beads composite materials were prepared by hydrolysis-precipitation method. The materials were characterized by SEM and XRD methods. SEM observation shows that the surface of beads have been loaded a uniform TiO2 film. XRD results shows that TiO2 films have the main phases of anatase and rutile mixed crystal structure. The effect of surface activation process of fly ash beads on TiCl4 solution hydrolysis rate was studied. The influence of calcination temperature on the microstructure and properties of composite materials was also discussed. The photocatalytic properties of the prepared materials was measured by using UV-1800 uv-vis spectrophotometer. The results show that: The composite which calcined at 500°C has a grain size of 15nm, anatase phase content of 90%, shows the best photocatalytic effect. The degradation rate of methyl orange solution can reach 95% after 2 hours irradiation (300W, Mercury lamp). Repeated experiments show that the degradation rate of composite materials still reach 80% after being used for 5 times .

Improved visible light photocatalytic activity of titania doped with tin and nitrogen

Tin and nitrogen co-doped titania has been prepared by a hydrolysis precipitation method and studied by X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance UV-vis absorption spectra, and photoluminescence. The surface area has been determined by using the BET method. Tin is incorporated into the TiO2 crystal lattice in substitutional mode, while nitrogen is present as surface species. The resultant energy levels of tin doping and nitrogen surface states are located inside the bandgap, which are close to the conduction and valence bands, respectively. Hence, co-doping of tin and nitrogen can greatly enhance the absorption in the visible light region and inhibit the recombination of photogenerated charge carriers, leading to a higher photocatalytic activity for the co-doped catalyst than pure TiO2 and solely doped TiO2 with nitrogen or tin for degradation of 4-chlorophenol under both visible and UV-light irradiation. This indicates that co-doping simultaneously with two foreign elements is a feasible way to improve the photocatalytic activity of TiO2.

Effect of heat treatment on crystal phase and photocatalytic activity of Tm doped TiO2 nanoparticles

Tm doped TiO2 nanoparticles have been synthesised by hydrolysis-precipitation method. The effect of heat treatment on the crystal phase and photocatalytic activity of Tm doped TiO2 nanoparticles has been studied. The prepared samples were characterised by transmission electron microscopy, X-ray diffraction, Fourier transformed infrared and diffuse reflection spectrum analysis. The results show that Tm3+ doping can effectively inhibit the phase transformation from antase to rutile and decrease the crystallite size of nano-TiO2 particles. There is an optimal Tm doping (1·4 mol.-%) after calcination at 550°C for the photocatalytic activity of methylene blue degradation.

Removal of fluoride from water using titanium-based adsorbents

Three adsorbents including TiO2, Ti-Ce, and Ti-La hybrid oxides were prepared to remove fluoride from aqueous solution. The Ti-Ce and Ti-La hybrid adsorbents obtained by the hydrolysis-precipitation method had much higher sorption capacity for fluoride than the TiO2 adsorbent prepared through hydrolysis. Rare earth (Ce and La) oxides and TiO2 exhibited a synergistic effect in the hybrid adsorbents for fluoride sorption. The sorption equilibrium of fluoride on the three adsorbents was achieved within 4 h, and the pseudo-second-order model described the sorption kinetics well. The sorption isotherms fitted the Langmuir model well, and the adsorption capacities of fluoride on the Ti-Ce and Ti-La adsorbents were about 9.6 and 15.1 mg·g−1, respectively, at the equilibrium fluoride concentration of 1.0 mg·L−1, much higher than the 1.7 mg·g−1 on the TiO2. The sorption capacities of fluoride on the three adsorbents decreased significantly when the solution pH increased from 3 to 9.5. The electrostatic interaction played an important role in fluoride removal by the three adsorbents, and Fourier transform infrared (FTIR) analysis indicated that the hydroxyl groups on the adsorbent surface were involved in fluoride adsorption.

TiO<SUB>2</SUB> Nanoparticles Co-Doped with Silver and Nitrogen for Antibacterial Application

We have prepared a series of TiO2 nanoparticles for antibacterial applications. These TiO2 nanoparticles were prepared by the hydrolysis precipitation method with Ti(OBu)4, silver nitrate and ammonia. Crystal structure, particle size, interfacial structure and UV-visible light response of the prepared nanoparticles were characterized by X-ray diffraction measurements (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRs). The XRD spectra showed that all samples were anatase structure calcined at 450 degrees C for 3 hours. The Ag doping made the peak of diffraction wider. The results of TEM showed that the nanoparticles of TiO2, N-TiO2 and 1% Ag-N-TiO2 were all spherical in shape and well distributed with a mean size of 19.8 nm, 39.2 nm and 20.7 nm, respectively. N doping caused the nanoparticle size to increase, while, when the doped amount of Ag+ increased, the TiO2 particle size decreased. The FTIR revealed that Ag and N doping of TiO2 appeared to have strong absorption by -OH group and showed the characteristic absorption band of NH4+ and Ag. The UV-Vis-DRs indicated that the absorption band of Ag-N co-doped TiO2 had red shift and that the optical absorption response (between 400 nm and 700 nm) had obvious enhancement. The antibacterial properties of nanoparticles were investigated by agar diffusion method toward Escherichia coli and Bacillus subtilis. The results indicated that both Ag- and N-doped TiO2 could increase the antibacterial properties of TiO2 nanoparticles under fluorescent light irradiation. A 1% Ag-N-TiO2 had the highest antibacterial activity with a clear antibacterial circle of 33.0 mm toward Escherichia coli and 22.8 mm toward Bacillus subtilis after cultivation for 24 hours.

Effect of the synthetic method of Pt/MgO in the hydrosilylation of phenylacetylene

This work describes the synthesis and characterization of Pt/MgO (Pt/Mg(OH)2, calcined Pt/MgO and agglomerated Pt/MgO ) catalysts. The supports of the catalysts were obtained by the hydrolysis-precipitation method and the metallic phase of platinum was incorporated by impregnation. The characterization of the synthesized materials was made by means of DRX, FTIR, TGA-DTA and TPR techniques. The catalysts were applied to the hydrosilylation of PhC≡CH with three different silanes (Ph3SiH, Ph2MeSiH and PhMe2SiH) as a model reaction. The activity of the proposed catalysts Pt/Mg(OH)2, calcined Pt/MgO and agglomerated Pt/MgO had a reaction yield of 95 %. When the catalysts Pt/Mg(OH)2 and agglomerated Pt/MgO were used in the reaction with Ph3SiH, the selectivity to the trans isomer was favored (90%). A relationship was found between the increase in the reaction time and the increase of the kinetic volume of the silane radicals. The present results were compared to the previously obtained results using as a catalyst Pt/MgO obtained by the sol-gel method.

Photo-electrochemical Lithium Insertion Characteristics of Carbon Nanotubes Modified with SrTiO3 Photocatalyst

Perovskite-type SrTiO3 nanoparticles were synthesized by direct hydrolysis-precipitation method and were employed to modify the surface of the carbon nanotubes to form a SrTiO3/CNTs composite. The photo-electrochemical lithium insertion characteristics of the SrTiO3/CNTs composite under xenon light irradiation were investigated. The results show that the light irradiation has little influence on the specific capacity of the CNTs electrode. However, for the SrTiO3/CNTs electrode irradiated by light, the lithium insertion capacity reaches about 251 mAh/g, much higher than that without light irradiation (170 mAh/g). Cyclic voltammetry test reveals that the light irradiation can remarkably increase the reaction currents of lithium insertion and extraction. This may be attributed to the photo-excited intercalation of Li-ions into the CNTs by the SrTiO3 photocatalyst when irradiated by light.

Preparation of novel titania supported palladium catalysts for selective hydrogenation of acetylene to ethylene

Novel titania supports have been designed and elaborated with the hydrolysis precipitation method, by adjusting and controlling of the main preparation parameters, such as pH value, adding rate of tetrabutyl titanate Ti(OBu)4, and calcining temperature of precursor during support preparation. The new titania supported Pd catalysts were prepared and investigated for selective hydrogenation of acetylene to ethylene. The catalyst samples have been characterized by temperature programmed reduction (TPR), XRD and BET techniques. The experimental results indicated that with MgO modification, the improved catalyst (0.5%Pd–MgO/TiO2) showed better performance of high and stable activity.

Direct synthesis of Sb 2O 3 nanoparticles via hydrolysis-precipitation method

Antimony oxide (Sb 2O 3) has wide applications as conductive materials, effective catalyst, functional filler and optical materials. Nanocrystalline Sb 2O 3 has been successfully synthesized by hydrolysis-precipitation method. The samples were characterized by means of transmission electron microscopy (TEM), high-resolution TEM (HRTEM) images, X-ray diffraction (XRD) and differential thermal analysis (DTA). The average crystal size of the Sb 2O 3 nanoparticles increases with increasing the reaction temperature. TEM image of the as-synthesized nanocrystalline Sb 2O 3 shows rod-like structure. HRTEM images indicate a preferred directional growth of the Sb 2O 3 nanoparticles. The electrochemical behaviors of Sb 2O 3 electrodes have been primarily investigated by cyclic voltammetry (CV) in lithium hexafluorophosphate (LiPF 6) solution. Sb 2O 3 nanocrystallite phase has prominent effect on the electrochemical properties. The results indicate that nanocrystalline Sb 2O 3 synthesized by hydrolysis-precipitation method shows potential application in the field of the electrode materials.

Morphological and Structural Characterization of a Titanium Dioxide System

TiO 2 was prepared by the homogeneous hydrolysis precipitation method from titanium tetraisopropoxide. The decrease of surface area observed with the thermal treatment can be related to the growth of crystallites, and there is good correlation between the surface area and the mean crystallite dimension. The coexistence of the three different crystalline TiO 2 phases is clearly evidenced by the XRD and FT-Raman measurements.