Turbidimetric detection method in flow-assisted separation of dispersed samples

Characterization of dispersed samples is an outstanding trend in analytical science. Among flow-assisted separation techniques for dispersed samples, size exclusion chromatography, hydrodynamic chromatography, and field-flow fractionation are the most widely applied. With dispersed analytes separated by these techniques, the UV/vis spectrophotometric detectors work as turbidimeters. To directly convert the analytical signal for quantitative analysis, the extinction properties of the dispersed analyte must be known. A new method is proposed to experimentally obtain-by single-run, flow-assisted separation with UV/vis diode-array detectors-the mass-size (or number-size) distribution function of the analytes when a retention-to-size relationship is either theoretically or empirically available for the chosen separation technique. This approach needs neither standards nor reliance on a method to predict the optical properties of the analytes. Theory and original algorithms are presented. Algorithms are then tested to optimize the numerical routines. Accuracy and robustness of the method are evaluated by simulation, and limitations for the application to experimental data are described. Finally, first application to field-flow fractionation shows validity of the method when applied to a few real cases.     

Some results of an investigation of the kinetics of separation and mixing of dispersed materials

This paper gives the results of an investigation of the kinetics of separation and mixing of dispersed materials due to vibration or a flow of liquid or gas in application to mineral enrichment and screen separation of grain products and other materials.     

Mathematical study of hydrocyclone dispersed phase separation in clearing viscoplastic drilling fluids

On the basis of rheodynamic equations, a numerical investigation of the flow structure of a viscoplastic fluid and dispersed phase separation in a hydrocyclone has been carried out. The proposed mathematical model will make it possible to calculate the separation indices and the velocity, pressure, and particle density fields in the apparatus.     

Effect of the concentration and size of droplets of the dispersed phase of an emulsion on the character of heat exchange in a boiling emulsion

Heat transfer from thin platinum wires to emulsions with a low-boiling dispersed phase has been studied experimentally. The appearance, growth, and separation of vapor bubbles at boiling on horizontal and vertical heated surfaces were demonstrated. The dependence of the delay of the beginning of boiling on the concentration of the emulsion and the size of droplets of the dispersed phase were considered.     

Electrical properties of V2O5-PbO-GeO2 glasses

Glasses in the V₂O₅-PbO-GeO₂ system containing 55 mol% V₂O₅ were found to undergo a droplet-type phase separation. The dispersed phase is rich in GeO₂. The volume percent of this phase increases with increasing GeO₂/PbO ratio in the glass. When the volume percent of dispersed phase is small, the direct current conductivity depends mainly on the continuous phase. When the dispersed phase reaches about 42 vol%, a second kind of phase separation appears in the continuous phase and thus alters the conductivity dramatically. Providing that the heterogeneity is taken into consideration, all the conductivities of phase-separated glasses can be explained by the theory proposed by Mott.     

Effects of polymer viscosity on the polymerization switching and electro-optical properties of unaligned liquid crystal/UV curable polymer composites

Polymer dispersed ferroelectric liquid crystal composite films consisting of varying polymer viscosities were prepared by polymerization induced phase separation (PIPS) technique. It was found that polymer viscosity influences the polarization switching and optical responses. A polymer dispersed ferroelectric liquid crystal film of low polymer viscosity shows faster switching, however a higher optical transmission at ~ 70% was observed in a higher polymer viscosity film.     

溶剂法制备聚合物分散液晶膜

用溶剂法制备了聚合物分散液晶膜。采用偏光显微镜、扫描电子显微镜和电光仪对相分离和聚合物分散液晶材料的电光性能作了初步探讨。研究结果表明，升温速度和聚合物含量对PDLC膜的相分离结构和响应电压有显著的影响。     

正交设计在溶胶-凝胶法制备单分散球形SiO_2中的研究

通过正交试验设计,用L9(43)正交表安排实验,在醇氨反应体系中采用溶胶-凝胶(sol-gel)法制备单分散球形SiO2,运用直观图和极差分析确定各主要原料对制备不同粒径SiO2的影响,优化配比。研究表明:对单分散球形SiO2的平均粒径的影响次序为:用水量、醇用量、氨水和正硅酸乙酯(TEOS)用量。通过控制反应条件,可实现在一定范围内获得尺寸均一、不同粒径、分散性好的球形SiO2。制备出的单分散球形SiO2颗粒形态完整,粒径140～500nm,分布窄、单分散性好。     

Pulmonary dispersion formulations: The impact of dispersed powder properties on pressurized metered dose inhaler stability

Suspension-type metered dose inhaler formulations characteristically have a high degree of dispersion instability. This may occur as the result of any of a large number of formulation issues including phase separation, particle growth, agglomeration/flocculation, moisture ingress, and particle interactions with both the canister material and other particles. Many of these undesirable instabilities may arise as a result of the physical and chemical properties of the dispersed powder in the liquid propellant system. As such, this review provides a detailed understanding of the characteristics of the dispersed phase in the liquid propellant system necessary to ensure stability of the final formulation.     

聚合物分散液晶的相行为

针对聚合物分散液晶(PDLC)二元体系进行了研究，主要包括外加直流电场下制备的PDLC的相图研究以及PDLC形成过程中相分离情况。在PDLC制备过程中由于外加直流电场对小分子液晶的作用，使液晶在此二元结构中的清亮点发生变化。结果表明，直流电场的引入导致PDLC中液晶清亮点升高。相分离行为主要是跟踪PDLC形成过程中由于小分子液晶与高分子链段之间的排斥作用而引起的相分离，研究了不同条件下PDLC相分离的快慢。     

DNA-assisted dispersion and separation of carbon nanotubes

Carbon nanotubes are man-made one-dimensional carbon crystals with different diameters and chiralities. Owing to their superb mechanical and electrical properties, many potential applications have been proposed for them. However, polydispersity and poor solubility in both aqueous and non-aqueous solution impose a considerable challenge for their separation and assembly, which is required for many applications. Here we report our finding of DNA-assisted dispersion and separation of carbon nanotubes. Bundled single-walled carbon nanotubes are effectively dispersed in water by their sonication in the presence of single-stranded DNA (ssDNA). Optical absorption and fluorescence spectroscopy and atomic force microscopy measurements provide evidence for individually dispersed carbon nanotubes. Molecular modelling suggests that ssDNA can bind to carbon nanotubes through pi-stacking, resulting in helical wrapping to the surface. The binding free energy of ssDNA to carbon nanotubes rivals that of two nanotubes for each other. We also demonstrate that DNA-coated carbon nanotubes can be separated into fractions with different electronic structures by ion-exchange chromatography. This finding links one of the central molecules in biology to a technologically very important nanomaterial, and opens the door to carbon-nanotube-based applications in biotechnology.     

聚丁二烯型聚氨酯弹性体微相分离结构研究

本文用现代测试手段,探讨了聚丁二烯型聚氨酯弹性体的微相分离结构形态。结果表明该种弹性体的微相分离非常接近于完全,聚氨酯硬段基本呈“卵石”结构分散在聚丁二烯软段连续相中,硬段存在有1～1000nm的不同层次的超尺寸结构。DSC的定量测试表明硬段在软段中的溶解量仅为3.2％。此外,还探讨了弹性体内存在的不同长度的刚性链段及两相界面层结构。     

Dispersion of micelle-encapsulated fluorophores in a polymer matrix for control of color of light emitted by light-emitting diodes

In the present study, we demonstrated that fluorescent dyes could be nanoscopically dispersed in a polymer matrix that was immiscible with the dyes; the dyes were encapsulated in micelles. Using a model polymer composite, we also showed that the color of light emitted by light-emitting diodes (LEDs) could be controlled by coating fluorescent polymer composites onto the LEDs. For this purpose, fluorophores that were insoluble in toluene were solubilized into a solution of block copolymer micelles in toluene by the selective incorporation of fluorescent dyes into micellar cores. Because the micelles could be dispersed well in the polymer matrix without the formation of aggregates, fluorescent dyes encapsulated in the micelles were also effectively dispersed in the polymer matrix without macroscopic separation. The polymer composite can be evenly coated onto most substrates, regardless of their surface characteristics. Thus, light-emitting devices with well-controlled emission wavelengths and emission intensities can be fabricated by coating the polymer composite onto the surface of the device.     

Aggregation of silver nanoplates in the presence of L‐cysteine and the application for separation

A facile method was investigated to fabricate the aggregated silver nanoplates as products for separation materials. Initially, ageing of L‐cysteine capped silver nanoplates in ethanol solvent led to fast aggregation. Then, the as‐formed aggregates were easily prepared as powder due to the highly volatile properties of ethanol. Interestingly, the aggregated powder would be soluble again after the dispersion in water and the re‐dispersed nanoplates could be obtained. Furthermore, the heavy metal ions such as Cu²⁺, Pb²⁺ and Hg²⁺ would soon accelerate the aggregation of the dispersed silver nanoplates again. The reversible aggregation process could be employed for separation applications in the future.Inspec keywords: silver, nanoparticles, aggregation, nanofabrication, organic compounds, separation, dissolving, copper, lead, mercury (metal)Other keywords: aggregation, L‐cysteine, separation materials, ageing, L‐cysteine capped silver nanoplates, ethanol solvent, aggregated powder, heavy metal ions, Ag, Cu, Pb, Hg     

Effect of fibrous filter properties on the oil-in-water-emulsion separation and filtration performance

Separation of secondary emulsions of dispersed droplet size less than 10 μm, by means of fibrous medium is a very complex but important process. The study investigates the influence of thin fibrous filter properties, i.e. surface energy, pore size and porosity on the separation performance of an isooctane in water emulsion (0.2%, mean drop size 2 μm). Experiments were carried out on five different filter media with a wide variation in their pore size (2-51 μm), surface energy (14-46 mN/m) and porosity (0.46-0.87) at similar process conditions. Filter media with different wettability are obtained by applying various hydrophobic and hydrophilic coatings. All the used coatings contain nanoparticles (25 nm) to impart nanoscale surface roughness at the single fiber surface. Besides emulsion properties and operating conditions, the phase separation mechanism and performance highly depends on pore size, surface energy and porosity of the filter media. More complete coalescence takes place at reduced pore size and at a surface preferentially wetted by the dispersed phase. Whereas when the pore size equals to the influent droplet size, then the surface wettability of filter is less effective and the separation mechanism is governed by inflow velocity. The emulsion inflow velocity and pressure drop are significantly affected by the filter media air permeability but do not depend on filter surface energy.     

Entrainment phenomenon in gas–liquid two-phase flow: A review

The gas–liquid separation equipments are aimed to be designed for maximum efficiency of phase separation. In order to maximize their capacity the flow rates are required to be optimized for the capital cost of equipment. This leads to the situation where the gas phase leaves the separation interface with high velocities and carry liquid phase along with it in the form of droplets reducing the equipment efficiency. This is known as entrainment or carryover. Depending on the nature of the separation interface i.e., turbulence intensity, bubble dynamics, the size and velocity distribution of liquid fragments, droplets at the separation interface varies. This is the main source of empiricism involved in the analysis of such equipments. The mechanics of motion of the dispersed liquid phase in bulk of gas is relatively well studied. In the present paper the various experimental, analytical and numerical investigations carried out to address the issues of entrainment/carryover are carefully analyzed. Further, a critical review has been presented for bringing out a coherent theme and a current status of the subject under reference.     

Direct Synthesis of MOF‐Derived Nanoporous Carbon with Magnetic Co Nanoparticles toward Efficient Water Treatment

Nanoporous carbon particles with magnetic Co nanoparticles (Co/NPC particles) are synthesized by one‐step carbonization of zeolitic imidazolate framework‐67 (ZIF‐67) crystals. After the carbonization, the original ZIF‐67 shapes are preserved well. Fine magnetic Co nanoparticles are well dispersed in the nanoporous carbon matrix, with the result that the Co/NPC particles show a strong magnetic response. The obtained nanoporous carbons show a high surface area and well‐developed graphitized wall, thereby realizing fast molecular diffusion of methylene blue (MB) molecules with excellent adsorption performance. The Co/NPC possesses an impressive saturation capacity for MB dye compared with the commercial activated carbon. Also, the dispersed magnetic Co nanoparticles facilitate easy magnetic separation.     

微米金刚石对电子绝缘封装胶导热性的改进

本文采用微米金刚石的掺杂改进电子绝缘封装胶的导热性能,制备了高导热的电子绝缘封装胶微米复合材料.用扫描电镜对微米金刚石复合材料的截面进行了表征.结果表明微米金刚石的掺杂能够很好的和电子绝缘封装胶进行结合,没有产生明显的两相分离,在电子绝缘封装胶中形成了良好的导热网络.用HOT DISK热常数测试仪对所制备的微米复合材料进行了导热系数的测量,结果表明,随着微米金刚石掺杂量的增加,复合材料的导热系数k有明显的提高.与纯电子绝缘封装胶的导热系数为0.24W/m*K相比,当微米金刚石掺杂量的质量百分比为12.5%时,复合材料的导热系数比纯电子绝缘封装胶的导热系数提高了29.2%.     

微过氧化物酶-11在碳纳米管/壳聚糖修饰电极上的直接电化学及电催化(英文)

采用一步法于室温下有选择性地将小管径的单壁碳纳米管(SWCNTs)分散于生物相容性的聚合物--壳聚糖的水溶液中,并将其滴涂于玻碳电极表面,制备出微过氧化物酶-11(MP-11)修饰电极.循环伏安结果表明SWCNq、促进了MP-11在电极表面的直接电子传递,在pH=7.2的磷酸缓冲溶液中,MP-11的式电位为-0.36 V(vs.SCE),MP-11在电极表面的直接电子转移表观速率常数和覆盖度分别为78 s-1和8.76×10-10mol·cm-2.进一步的研究结果显示,固定在SWCNT表面的MP-11能保持其对氧气和过氧化氢还原的生物电催化活性,适合用作生物燃料电池的阴极和过氧化氢传感器.氧气在该修饰电极上的还原经历一个四电子过程;该过氧化氢生物传感器对过氧化氢还原的检测具有响应灵敏度高(响应时间小于4 S),检测线性范围为2.5×10-6～7.0×10-3vM,检测限为0.8 μM,相应的米氏常数和检测灵敏度分别为1.0 mM and 22.4μA/mM.     

Particle Separation in an Annular Converging Channel with an Inner Rotating Permeable Baffle

The relation between the separation efficiency of solid particles and the stability of the helical flow of a viscous fluid in a converging channel with an inner rotating permeable cylindrical baffle has been studied. The profiles of the axial and tangential velocities and the separation efficiency of solid particles have been calculated based on the numerical solution of a system of equations describing the hydrodynamics of two-phase media. Analysis of the obtained solutions shows that vortices having an effect on particle separation can appear in the converging channel. Moreover, the larger the size of the converging annular channel, the earlier a loss of stability occurs. It has been found that the formation of vortices is impossible for some flow regimes and, as a result of fluid flow stabilization, the fraction of particles settled on the permeable cylindrical baffle decreases. It has been shown that those regime parameters at which a helical flow exists should be selected for the development of combined action units involving filtering and the separation of the solid dispersed phase.