A Size-Controllable Precipitation Method to Prepare CeO₂ Nanoparticles in a Membrane Dispersion Microreactor

A membrane dispersion-based microreactor was used to prepare ceria nanoparticles using cerium nitrate and ammonia–water as the raw reagents. The traditional precipitation process makes it difficult to control crystal size in a stirred tank reactor; therefore, a new membrane dispersion microreactor was used, which was able to easily control the crystal size. Most importantly, the size of ceria nanoparticles was significantly reduced because of the enhanced mixing performance of the membrane dispersion microreactor. The crystal size of the prepared ceria in this new procedure reached 8.2 nm in comparison to ∼16.7 nm from the traditional precipitation process under identical conditions. The effects of supersaturation, pH value, mixing intensity, and reaction temperatures were also investigated in detail. Therefore, ceria nanoparticles with average sizes of 7–12 nm can be controllably obtained. Furthermore, the reaction time to reach 90% AO7 degradation rates was improved by ∼89.2% using the ceria prepared in the membrane dispersion microreactor compared to that in a stirred tank reactor with an initial AO7 concentration of 60 ppm and H₂O₂ concentration of 80 mmol/L. To conclude, this study provides a size-controllable preparation method for ceria nanoparticles, particularly with smaller particle sizes and superior catalytic activity

Preparation of Large-Pore-Volume γ‑Alumina Nanofibers with a Narrow Pore Size Distribution in a Membrane Dispersion Microreactor

A coprecipitation method was developed to synthesize fibrous γ-Al₂O₃ with a large pore volume using a membrane dispersion microreactor with NaAlO₂ and Al₂(SO₄)₃ as reactants. The pore size distribution was controlled because of the high mixing intensity and relatively homogeneous saturation in the membrane dispersion microreactor. The influences of the pH and concentration of the NaAlO₂ aqueous solution and of the two-phase flow rates were investigated. By controlling the pH to be around 9 and the concentration of NaAlO₂ aqueous solution to be 0.50–1.25 mol/L, we obtained γ-Al₂O₃ nanofibers with pore volume of 0.95–1.52 mL/g. Under the maximal pore volume (1.52 mL/g), the specific surface area was 403.8 m²/g and the pore size distribution was 3–50 nm with a distribution variance of 0.2020. The length and diameter of the nanofibers were about 27.3 and 3.4 nm, respectively. This study provides a simple, economical method for preparing fibrous γ-Al₂O₃ with both a large pore volume and a narrow pore size distribution, which could be used as an excellent catalyst support for the petroleum-refining industry

Ultrafast, Continuous and Shape-Controlled Preparation of CeO₂ Nanostructures: Nanorods and Nanocubes in a Microfluidic System

Ceria nanorods enclosed with {110}/{100} planes and ceria nanocubes with {100} planes have been successfully prepared using a homemade microfluidic system in a continuous, ultrafast and shape-controllable manner. Only 8 min of reaction time are needed rather than days to synthesize ceria nanostructures in the traditional batch hydrothermal method. During the synthesis, reaction temperatures and base concentration have been demonstrated as the key factors responsible for the shape evolution. Accordingly, a morphological phase diagram was determined. In addition, polyvinylpyrrolidone was introduced to realize the transformation from ceria nanorods to nanocubes under unfavorable hydrothermal conditions. Catalytic performance of different CeO₂ architectures was also examined in decomposing hydrogen peroxide and a reactivity trend (nanoparticles < nanorods < nonocubes) was observed. This is assumed to be related with different surface oxygen vacancy amounts as a result of {110}/{100} preferential planes, as confirmed by X-ray photoelectron spectroscopy and Raman analyses as well as density functional theory (DFT+U) calculations

Controllable Preparation and Catalytic Performance of Heterogeneous Fenton-like α‑Fe₂O₃/Crystalline Glass Microsphere Catalysts

Highly dispersed α-Fe₂O₃ nanoparticles were immobilized onto crystalline glass microspheres for the first time to be heterogeneous Fenton catalysts (FeCG) with favorable activity. The average particle size of the supported iron oxides ranges from 2.6 to 6.5 nm and can be achieved controllably with great ease. Typically, through hydrothermal treatment, it was found that an amorphous glass support develops into mixed crystals of primitive SiO₂, CaSi₂O₅, and Ca₂MgSi₂O₇, with ∼180% improvement in specific surface areas. Most importantly, after Fe loading, not only OH· but also HO₂· radical species with high intensity were generated for FeCG, while OH· alone was produced for commercial α-Fe₂O₃ in the presence of H₂O₂, thus accelerating the redox recycling between Fe­(II) and Fe­(III) and presenting much superiority in the azo dye AO7 decoloration. The pseudo-zero-order reaction constant was determined to be 0.384 mg/(L·min), an ∼65.5% improvement over that of commercial α-Fe₂O₃ under the same experimental conditions. Only 1.26 mg/L Fe leaching was detected under optimum conditions in addition to simple catalyst recovery by gravity. No remarkable decrease in the AO7 decoloration efficiency was observed after six cycles, indicating the favorable stability

Preparation of Au Nanocolloids by in Situ Dispersion and Their Applications in Surface-Enhanced Raman Scattering (SERS) Films

The size uniformity and dispersity of inorganic nanoparticles are important when they are dispersed in organic phase and serve as the precursor for particle-deposited nanosensors. However, most of the nanoparticles are dispersed into coating solutions right after surface modification, where the natural tendency of nanoparticles to agglomerate reduces the monodispersity and size uniformity during the coating process. By initiation of microdroplet coalescence, a method for in situ dispersion of surface-modified Au nanoparticles is presented in this study. Under optimal conditions, about 88% of the modified Au nanoparticles with an average size of 19 nm could be in situ dispersed. On the basis of dip-coating of the monodispersed Au nanocolloids, a SERS (surface-enhanced Raman scattering) film was fabricated by uniformly depositing particles onto the surface and tremendous enhancement of Raman scattering was achieved. The SERS film could be used to detect a representative contaminant, <i>trans</i>-1,2-bis­(4-pyridyl)­ethylene (BPE), with a detection limit of down to 10 ppb

Precipitation Preparation of High Surface Area and Porous Nanosized ZnO by Continuous Gas-Based Impinging Streams in Unconfined Space

Using the precipitation method, we propose a new process for the preparation of high specific surface area and large pore volume ZnO nanoparticles in unconfined space with NH₄HCO₃ and ZnSO₄·7H₂O as the reactants. The mixing performance of the reaction system was improved by gas atomization and continuous gas-based impinging streams before the precipitation reaction. By virtue of the gas environment and gas division, the obtained nanoparticles have a very good dispersion performance. Under optimal conditions, the ZnO nanoparticles were synthesized with a surface area of 88.89 m²/g, an average diameter of 7 nm, and a pore volume of 0.68 cm³/g. The influences of ZnSO₄ concentration, pressure, and gas–liquid ratio on the properties of the synthesized nanoparticles were studied. This study aims to provide a feasible and economical way to produce better properties in nanosized ZnO particles, which are widely applied as a new, multifunctional material

A Comparison of New Gemini Surfactant Modified Clay with its Monomer Modified One: Characterization and Application in Methyl Orange Removal

New gemini surfactant, glycol bis-<i>N</i>-tetradecyl nicotinate dibromide (designated E_G), and the corresponding monomer, methyl <i>N</i>-tetradecyl nicotinate bromide (E_S), were synthesized and utilized to modify sodium bentonite (Na-Bt). E_G-Bt and E_S-Bt, the surfactant modified bentonites, were then used for methyl orange (MO) removal from the dye solution. E_G was more effective than E_S at expanding the interlayer space of Na-Bt. The adsorption of E_G, E_S and MO obeyed well the pseudo-second-order kinetic model and Langmuir isotherms on Na-Bt or on the modified bentonite. However, the adsorption of E_G was more spontaneous than that of E_S, and E_G replaced more small particles, such as Na⁺ and water, than E_S did during the adsorption on Na-Bt. The elevated temperature impairs the adsorption of the surfactants, but enhances that of MO. MO absorbed more easily on E_G-Bt than on E_S-Bt. When the dosage of the surfactants used goes beyond a certain amount, the uptake of MO by E_G-Bt/E_S-Bt decreases slowly owing to desorption of the surfactants. E_G and E_S formed a complex with MO on the modified bentonite as evidenced by UV–vis spectra, and E_G exhibited the stronger interaction with MO

Coprecipitation Synthesis of Large-Pore-Volume γ‑Alumina Nanofibers by Two Serial Membrane Dispersion Microreactors with a Circulating Continuous Phase

A coprecipitation method was developed for the synthesis of fibrous γ-alumina using serial membrane dispersion microreactors with a circulating continuous phase and high concentrations of NaAlO2 and Al2(SO4)3 as reactants. Owing to the ultra-high mixing intensity and reduction of supersaturation due to the large circular phase ratio, a large pore volume and specific surface area and an extremely narrow pore diameter distribution were realized using the high-concentration and high-viscosity precipitation system. The influence of the phase ratio, dispersion order of reactants, Al2(SO4)3 residence time, and the precipitation reaction pH and time were investigated, and the nanofiber formation mechanism was explored employing theoretical calculations. By controlling the Al2(SO4)3 residence time of 3 s, phase ratio of 16, and pH of 8.0, γ-Al2O3 nanofibers with a pore volume of 1.36 cm3/g, a specific surface area of 376 m2/g, and a length/diameter ratio in the range of 30–54 were obtained without any organic reagents. This study provides an economical and readily scalable method for the synthesis of fibrous γ-Al2O3 with excellent pore properties and a large specific surface area, which can potentially be applied as an excellent catalyst support for diesel and bio-oil hydrogenation

Fate of As(III) and As(V) during Microbial Reduction of Arsenic-Bearing Ferrihydrite Facilitated by Activated Carbon

Microbial reduction of arsenic (As)-bearing Fe­(III)-(oxyhydr)­oxides is one of the major processes for the release of As in various environmental settings such as acid mine drainage, groundwater, and flooded paddy soil. Pyrogenic carbon has recently been reported to facilitate microbial extracellular reduction of Fe­(III)-(oxyhydr)­oxides. The aim of this study was to investigate the important hot topic regarding the fate and transformation of As during activated carbon (AC) facilitated microbial reduction of As-bearing ferrihydrite. Our results show that the rate and extent of Fe­(III) reduction in As-bearing ferrihydrite by <i>Shewanella oneidensis</i> MR-1 were accelerated by AC. The AC facilitated reduction caused the release of As­(III) into the solution, whereas it caused the preferential immobilization of As­(V) on the solid phase. Furthermore, AC accelerated the precipitation of vivianite and siderite in sequence during microbial reduction processes. Both of the formed vivianite and siderite had an insignificant capacity for capturing As­(III); however, As­(V) was selectively immobilized by vivianite compared to that of siderite. Taken together, our findings provide crucial insights into understanding the role of AC on the redox and immobilization of Fe and As in suboxic and anoxic environments and thus their environmental fate when pyrogenic carbons are employed for agronomic and environmental applications

sj-xlsx-4-tct-10.1177_15330338221124658 - Supplemental material for In Vitro and in Vivo Study of the Effect of Osteogenic Pulsed Electromagnetic Fields on Breast and Lung Cancer Cells

Supplemental material, sj-xlsx-4-tct-10.1177_15330338221124658 for In Vitro and in Vivo Study of the Effect of Osteogenic Pulsed Electromagnetic Fields on Breast and Lung Cancer Cells by Mike Y. Chen, Jing Li, Nianli Zhang and Erik I. Waldorff, James T. Ryaby, Philip Fedor, Yongsheng Jia, Yujun Wang in Technology in Cancer Research & Treatment</p