High-gravity Reactive Precipitation Method Research Articles

Monodispersed ZnO Nanoparticle-Poly(methyl methacrylate) Composites with Visible Transparency for Ultraviolet Shielding Applications

The inorganic–organic nanomaterials with high visible light transmittance have shown great potential in applications. However, it is difficult to disperse nanoparticles uniformly in organic matrices, resulting in an obvious decrease in transparency. This article reports a method to prepare ZnO-poly(methyl methacrylate) (ZnO-PMMA) nanocomposites with high transparency and excellent properties. First, a highly transparent nanodispersion of ZnO in methyl methacrylate (MMA) monomer is synthesized by the high-gravity reactive precipitation method. Then, ZnO-PMMA nanocomposites are prepared by the in situ bulk polymerization method. ZnO nanoparticles are about 6 nm with narrow size distribution, which monodisperse in MMA with the surface modifier containing C═C double bonds, contributing to the uniform dispersion of ZnO nanoparticles in PMMA matrices. Therefore, it ensures that the prepared ZnO-PMMA nanocomposites keep a high visible transmittance without any Rayleigh scatter. Moreover, ZnO-PMMA nanocomposites achieve multiple function applications of UV-shielding and anti-photo-aging, due to good thermal stability and high toughness and stiffness, which is attributed to the good dispersion of ZnO nanoparticles. After 200 h of UV radiation, pure PMMA obviously turns yellow and has a remarkable decrease in mechanical properties, whereas the nanocomposite is colorless and still keeps high visible transmittance and mechanical performances, which has great potential applications in the fields of optical materials and equipment.

Preparation of CoFe2O4 nanoparticles based on high-gravity technology and application for the removal of lead

The aim of this paper is to explore a simple method for the preparation of magnetic bimetallic oxides with high production efficiency and high adsorption capacity of Pb(II). In this work, the CoFe2O4 nanoparticles were continuously synthesized through a high-gravity reactive precipitation method using an impinging stream-rotating packed bed reactor with a theoretical production rate of 0.704kgh−1. The samples were characterized by XRD, TEM, N2 adsorption-desorption technique and VSM. The obtained results show that the as-prepared CoFe2O4 nanoparticles have higher surface area (89.15m2g−1) and saturation magnetization (75.43Am2kg−1) than that of single metal oxides (Fe2O3 and Co3O4). The adsorption data of Pb(II) onto CoFe2O4 nanoparticles fit well to pseudo-second order kinetic model and Langmuir isotherm model. The maximum adsorption capacity of Pb(II) onto CoFe2O4 was 326.79mgg−1, while for Fe2O3 and Co3O4 nanoparticles were 140.84 and 284.90mgg−1, respectively. Moreover, the proposed adsorbent exhibited good reusability for up five adsorption-desorption cycles. Hence, the high-gravity technology could prepare high adsorption adsorbent with high production efficiency, which brings good prospects in wastewater treatment.

Facile and scalable preparation of α-Fe2O3 nanoparticle by high-gravity reactive precipitation method for catalysis of solid propellants combustion

A facile and scalable route, using the high-gravity reactive precipitation method which was carried out in a rotating packed bed (RPB) reactor, was proposed to synthesis α-Fe2O3 catalyst which is used to catalyze the decomposition of solid propellants. The effect of high-gravity level (G) of RPB reactor on the particle size and its distribution of α-Fe2O3 was explored. It was found that increasing the G of RPB is beneficial for the formation of α-Fe2O3 with smaller particle size and narrower size distribution. The α-Fe2O3 nanoparticles around 85 nm with narrow size distribution could be synthetized when G is higher than 120. The catalytic performance of the as-synthesized α-Fe2O3 on the thermal decomposition of ammonium perchlorate (AP) was performed by differential scanning calorimetric (DSC) method. DSC results show that adding 2 wt% as-prepared 84 nm α-Fe2O3 can decrease the temperature of low-temperature decomposition (LTD) and high-temperature decomposition (HTD) of AP by 14.4 °C and 53.4 °C respectively, and increase the heat released of AP's thermal decomposition process from 864 J/g to 1235 J/g. Besides, result of DSC test and kinetic analysis indicated that the catalytic performance of α-Fe2O3 on the thermal decomposition of AP increased with lessening the average particle size of α-Fe2O3.

Removal of heavy metal ions by magnetic chitosan nanoparticles prepared continuously via high-gravity reactive precipitation method

This study aimed to provide a continuous method for the preparation of magnetic Fe3O4/Chitosan nanoparticles (Fe3O4/CS NPs) that can be applied to efficient removal of heavy metal ions from aqueous solution. Using a novel impinging stream-rotating packed bed, the continuous preparation of Fe3O4/CS NPs reached a theoretical production rate of 3.43kg/h. The as-prepared Fe3O4/CS NPs were quasi-spherical with average diameter of about 18nm and saturation magnetization of 33.5emu/g. Owing to the strong metal chelating ability of chitosan, the Fe3O4/CS NPs exhibited better adsorption capacity and faster adsorption rates for Pb(II) and Cd(II) than those of pure Fe3O4. The maximum adsorption capacities of Fe3O4/CS NPs for Pb(II) and Cd(II) were 79.24 and 36.42mgg−1, respectively. In addition, the Fe3O4/CS NPs shown excellent reusability after five adsorption-desorption cycles. All the above results provided a potential method for continuously preparing recyclable adsorbent with a wide prospect of application in wastewater treatment.

Preparation of amorphous drug nanoparticles by high-gravity reactive precipitation technique

For many water insoluble acidic or alkaline drugs, amorphization and nanonization represent an effective bioavailability enhancement strategy. Cefixime (CFX) was chosen as a model drug, and amorphous nanoparticles were prepared via a typical process intensification technology: high-gravity reactive precipitation (HGRP). The effects of temperature, rotating speed, overall flow rate, and drug concentration on the particle size and size distribution were investigated. Under the optimum conditions, spherical nanoparticles with a mean size of 45nm could be precipitated. After filtration, redispersion and spray-drying processes, the obtained CFX nano-powder showed a good stability and exhibited a tremendously enhanced saturation solubility, reaching ∼11 times higher than that of raw CFX. Furthermore, CFX nano-powder achieved 100% drug dissolution within 2min while raw CFX did not dissolve completely after 45min. Since the production capacity of lab-scale RPB reached 2.3kg/h, HGRP method might offer a general platform for mass production of drug nanoparticles without the use of organic solvents and pharmaceutical additives.

Continuous preparation of Fe3O4 nanoparticles combined with surface modification by L-cysteine and their application in heavy metal adsorption

L-cysteine functionalized Fe3O4 magnetic nanoparticles (Cys–Fe3O4 MNPs) were continuously fabricated by a simple high-gravity reactive precipitation method combined with surface modification through a novel impinging stream-rotating packed bed with the assistance of sonication. The obtained Cys–Fe3O4 MNPs was characterized by XRD, TEM, FTIR, TGA and VSM, and further used for the removal of heavy metal ions from aqueous solution. The influence of pH values, contact time and initial metal concentration on the adsorption efficiency were investigated. The results revealed that the adsorption of Pb(II) and Cd(II) were pH dependent process, and the pH 6.0 was found to be optimum condition. Moreover, the adsorption kinetic for Cys–Fe3O4 MNPs followed the mechanism of the pseudo-second order kinetic model, and their equilibrium data were fitted with the Langmuir isothermal model well. The maximum adsorption capacities calculated from Langmuir equation were 183.5 and 64.35mgg−1 for Pb(II) and Cd(II) at pH 6.0, respectively. Furthermore, the adsorption and regeneration experiment showed there was about 10% loss in the adsorption capacity of the as-prepared Cys–Fe3O4 MNPs for heavy metal ions after 5 times reuse. All the above results provided a potential method for continuously preparing recyclable adsorbent applied in removing toxic metal ions from wastewater through the technology of process intensification.

Synthesis and application of nanoparticles by a high gravity method

Synthesis and application of nanoparticles by a high gravity method

Preparation and characterizations of uniform nanosized BaTiO 3 crystallites by the high-gravity reactive precipitation method

A novel method for the preparation of uniform nanosized crystalline particles of barium titanate (BaTiO 3) at a low temperature (<100°C) by the high-gravity reactive precipitation (HGRP) technique is described. On the basis of the analysis of key engineering factors predominating in a reactive precipitation process, several experimental parameters, including the flow rate, reaction temperature, reactant concentrations, and effect of high gravity level were varied in order to establish the optimum conditions for the preparation of uniform nanosized BaTiO 3 crystallites. The BaTiO 3 powders, produced by the HGRP technique, show a cubic structure at room temperature and a quasi-spherical morphology. The stoichiometry of the BaTiO 3 particles can be controlled precisely and reproducibly. The reactants, barium and titanium salts can be used in high concentrations and the yield is quantitative. BaTiO 3 particles, in purely cubic phase as synthesized, underwent a phase transition to tetragonal phase by calcination over 1000°C. The lattice constant, a, decreased with an increase in the calcined temperature. These abnormal crystallographic features are assumed to result from lattice defects caused by OH incorporated in perovskite lattice as well as the grain growth in BaTiO 3 particles. The results of sintering tests and dielectric performance on the dry pressed titanate powders showed that the sintered body had a high permittivity and a low dissipation factor. The process has potential application in industry.

Assistant effect of nano-CaCO3particles on the dispersion of TiO2pigment in polypropylene composites

TiO2 is extensively used in materials-coloring field as an excellent white pigment. An increasing interest focuses on the surface coating modification of TiO2 in order to improve the application performance in polymer matrix [1–3]. Martin Arellano et al. studied the surface modification of TiO2 powder and presented an evaluation method [1]. Noman S. Allen et al. investigated the photochemical and thermochemical behavior of TiO2 pigments [2]. Nano-CaCO3 is an important inorganic material whose toughening and strengthening functions in plastics have been verified [4–6]. In this paper, nano-CaCO3 synthesized by a high gravity reactive precipitation method was employed as a new pigment dispersant, blending with TiO2 and other additives to prepare complex master batches for use in the coloring of polypropylene (PP). The influence of the synergism of CaCO3 and TiO2 on the performance of colored PP products is discussed. Nano-CaCO3, TiO2 and other additives were stirred uniformly in a high speed mixer followed by blending in a double roll plasticator. The blended sample was crushed and extruded in a single screw extruder to prepare nanosized complex color masterbatch, which was subsequently blended with PP resin in a plastic jetting-molding machine to yield colored products. Whiteness measurements were performed by a TC– P II G Auto Color Difference Meter (Beijing Optical Instrument Factory, China, Hunter’s L, a, b color space, 0/d geometrical conditions, 10 ◦ field of view, TW whiteness formula). Ultraviolet (UV) absorption characteristics of the samples were determined by a UV2501-PC Spectrometry (Shimadzu, Japan). The dispersion extent of TiO2 in PP was observed by a H-800 transmission electron microscope (TEM) (Hitachi, Japan). The rheology of the samples was examined by a PLV-151 Brabender torque rheometer (Brabender, Germany, temperature = 210 ◦C, rotating speed = 30 rpm). Fig. 1 shows the TW whiteness index of the composites with a fixed total amount of nano-CaCO3 and TiO2 added, while TiO2 is partially replaced by nanoCaCO3 at different doses. It can be seen from Fig. 1 that a partial substitution of nano-CaCO3 for TiO2 can raise the whiteness of colored PP. The whiteness index of the materials reaches a maximum when 10% of TiO2 is replaced by nano-CaCO3, which is 4.3% higher than those without any replacements of TiO2 by nanoCaCO3. This is because nano-CaCO3 can prompt the dispersion of TiO2 particles in the matrix and boost the coloring effects of the materials. The doses of TiO2 also reduce accordingly. Fig. 2 shows the UV absorbency (Abs.) curves of TiO2 and nano-CaCO3 powders. It can be seen from Fig. 2 that TiO2 exhibits a very strong absorbency for the UV light in the wavelength of 290–400 nm, while the absorbency of nano-CaCO3 is notably lower than that of TiO2 in this wavelength range. Fig. 3 shows that UV absorbency curves of colored PP. The UV absorbency of colored PP changes little when TiO2 is partially replaced by nano-CaCO3. Because nano-CaCO3 can improve the dispersion of TiO2 in PP matrix, the UV absorptance of TiO2 remains unchanged even if its concentration is lowered. This result is favorable for the reduction of the product cost while maintaining a good aging resistance performance. Fig. 4 shows the TEM pictures of PP/TiO2/CaCO3 composites. Fig. 4a is the TEM picture of PP/TiO2, without any addition of nano-CaCO3. It is obvious that large aggregates form in this system. Fig. 4b is the TEM picture of PP/TiO2/CaCO3, while the concentration of TiO2 keeps unchanged and the dose of nano-CaCO3 accounts for 10% of the dose of TiO2. Fig. 4c is the TEM picture of PP/TiO2/CaCO3, while the total concentration of TiO2 and nano-CaCO3 combined remains

Fabrication of Nanoporous Silica Nanospheres and Nanotubes by Inorganic and Organic Double Templates

AbstractInorganic and organic double templates were used to fabricate silica nanospheres and nanotubes with nanochannels perpendicular to the shells. Sphere and needle like CaCO3 nanoparticles, synthesized by a high gravity reactive precipitation method, were used as inorganic templates and C16H33N(CH3)3Br (C16-CTAB) was used as an organic surfactant template. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to characterize the nanoporous structure. The nanochannels were found perpendicular to the surface of nanospheres and nanotubes. The size of nanochannels is about 3~5 nm. The size of hollow nanosphers and nanotubes can be controlled by the inorganic CaCO3 nanoparticle templates and the nanochannels in the shells can be tuned by different surfactant micelles. The nanospheres and nanotubes with nanochannels perpendicular to the shells have a potential application in chemical bio-catalyst, bio-separation, and drug delivery.