高梯度磁过滤技术及展望

介绍一种新型分离技术——高梯度磁过滤技术 (简称 HGMF)及展望 ,并预测超导磁过滤技术是未来高梯度磁过滤技术的发展方向。     

磁性流体固定床萃取分离低浓度金离子

采用一种全新的快速萃取方法--磁性流体固定床萃取分离技术,该方法是将磁性Fe₃O₄纳米颗粒表面包覆油酸,溶于有机溶剂中,加入萃取剂三苯基氧化膦TPPO,制成磁性萃取剂。借助于高梯度磁性分离装置,对目标离子进行萃取分离。萃取完成后通过原子吸收光谱仪测定萃取后金溶液中Au³⁺的浓度。通过对铁磁导线直径、初始金溶液pH值、萃取剂体积分数和协同萃取等影响因素的考察,得出了对Au³⁺浓度为19.128 mg·L^-1的氯金酸溶液进行萃取分离的最佳工艺：采用直径为2.34 mm的铁磁导线作为磁性填充介质时萃取率较其他优越。初始金溶液的pH值和萃取剂的体积分数对萃取率影响较大。在初始金溶液pH=1,萃取剂(TPPO)体积分数达到50%时萃取率最高。使用TPPO和TBP协同萃取也能提高萃取率。采用浓度为1 mol·L^-1的硫脲进行反萃实验,振荡10 min,反萃率在90%以上。     

Diffusive Capture of Magnetic Particles by an Assemblage of Random Cylindrical Collectors

Abstract

We develop an effective medium model describing the capture of ultra-fine magnetic particles (diameter much less than 1 µm) by an assemblage of parallel magnetic cylinders, randomly distributed in static fluid. The continuity equation describing the dynamics of concentration is solved numerically to obtain the concentration in various regions around the collector. The concentration contours are generated and the saturation, accumulation, and depletion regions are indicated. The effect of varying collector packing fractions appears significantly in regions close to the outer boundary of the representative cell where the build-up features of ultra-fine particles near the collector surface are similar for packing fractions in range 5–10%.     

Theoretical Analysis of a Magnetic Separator Device for Ex‐Vivo Blood Detoxification

Abstract

The feasibility of a magnetic separator device for ex‐vivo blood detoxification was studied. This blood detoxification approach entails administering functionalized magnetic microspheres (FMMSs) into a patient's body by transdermal injection to capture and remove toxins from the blood using highly specific receptors attached to the surface of the FMMSs. These toxin‐loaded FMMSs are then removed from the body using extracorporeal blood circulation through a specially designed magnetic separator, based on high gradient magnetic separation principles. The performance of the magnetic separator, in terms of its collection efficiency (CE) of the FMMSs, was evaluated theoretically using a streamline analysis of a 2‐D model. The effects of blood velocity (1 to 20 cm/s), magnetic field strength (0.1 to 2.0 T), wire size (0.125 to 2.0 mm in radii), separator unit size at a fixed ratio of tube to wire diameter of one, tube length (2.0 to 20 cm), wire material (nickel, SS 430 and wairauite), and magnetic material comprising the FMMSs (iron, typical magnetite and weaker magnetite) on the CE were evaluated. Provided that the blood velocity was below 2 cm/s, CEs >80% could be attained under reasonable conditions, like when using FMMSs 400 nm in diameter and containing 60 wt% magnetite in a magnetic field of 0.5 T using a magnetic separator with 0.5 mm radii wire (at a fixed ratio of tube to wire diameter of close to one) that was 10 cm in length (same as the tube) and made of SS 430. CEs of between 30% and 80% could also be attained at blood velocities up to 20 cm/s without compromising the magnetic separator design. The magnetic separator performance improved by reducing the size of the unit with tubes and wires of equal radii, increasing the applied magnetic field strength, utilizing magnetic materials with the highest magnetizations, and increasing the length of the unit. Overall, the results from this study delineated the physically realistic conditions that make ex vivo blood detoxification possible with this magnetic separator device.     

pH‐reversible magnetic gel with a biodegradable polymer

Polymer gels that react to external stimuli, such as pH, temperature, and electromagnetic fields, are an important class of materials. Such materials have pharmaceutical, industrial, and biomedical applications. Our intention in this study was to synthesize a stimuli‐responsive polymer gel with a biodegradable polymer. However, the chemical crosslinker, divinyl sulfone, which is most widely used for the crosslinking of this type of material, is highly toxic in nature. To overcome this problem, a reversible magnetic gel was synthesized with hydroxy propyl cellulose (HPC) and maghemite at pH 13 without with a chemical crosslinker. With a decrease in pH from 13 to 9, the gel formed a homogeneous dispersion of HPC particles with maghemite in it. This process was a reversible physical gelation where the crosslinks of the network had a physical origin (in this case, hydrogen bonding) and, therefore, were sensitive to variations in pH. When this physically prepared gel was compared with the chemically crosslinked one, no significant differences in structural properties were noted. At higher pH values, the gel was formed due to weak intermolecular hydrogen bonding, as observed by the broadening of the IR band in both the magnetic and nonmagnetic gels. Transmission electron micrographs also showed no significant difference in the gel morphology. Differential scanning calorimetry showed an increase in melting temperature for the gel sample compared to that of pure HPC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3337–3341, 2004     

PMR-15 processing,properties and problems—a review

The frontrunner in the race to develop a high temperature resin for use in advanced composites intended for high temperature applications is the NASA developed polyimide PMR-15. One of the key factors in the success of the material is the relatively easy processing which is due mainly to the use of the PMR approach (Polymerisation of Monomeric Reactants). Prepreg and high quality composite laminates (glass or carbon) can be prepared with ease. Laminate properties compare well with conventional epoxy based systems but thermal stability is much greater. Continuous use temperatures are in the range 280-300°C, some 150-170°C higher than epoxy systems. Applications of PMR-15 composites include aero-engines, missiles, spacecraft and military aircraft. Despite being the leading system available today PMR-15, like all materials, has a number of limitations affecting its widespread use. Included in these are reliable methods of quality control, prepreg batch to batch variability, microcracking from thermal cycling, health and safety hazards and high temperature processing. This paper reviews the present status of PMR-15 development and outlines work designed to identify and where possible overcome these limitations.     

Characterization of a Prototype Compact High Gradient Magnetic Separator Device for Blood Detoxification

Abstract

A prototype compact magnetic separator device for human blood detoxification was characterized using blood-mimicking fluid (ethylene glycol-water solution) as well as whole blood. Magnetic separation at various applied magnetic fields (0.125, 0.33, and 0.44 T) and various flow rates (3.1–29.5 ml/min) showed that the device could efficiently separate magnetic spheres from blood-mimicking fluid at a moderate applied magnetic field (for example, <0.44 T) and relatively high flow rates (for example, ≤29.5 ml/min). The experiments done in flow circulation systems showed that higher flow rates might shorten the sphere recovery time and accelerate the detoxification process. In vitro separation from flowing blood showed that it is possible to use the device to efficiently recover spheres in a reasonably short time (≤60 min). Moreover, it was also demonstrated that the separator had little effect on the occurrence of hemolysis. All the results revealed that the separator could be a clinically applicable device for efficient separation of magnetic spheres from blood flow for human detoxification purpose.     

Magnetic field effect on the anodic behaviour of a ferromagnetic electrode in acidic solutions

The magnetization of a ferromagnetic electrode in an external homogeneous magnetic field leads to a stray field in front of the electrode. This stray and its gradients can alter the anodic behaviour of the electrode significantly. Potentiodynamic polarisation measurements of an iron wire in a 0.5 M sulfuric acid solution (pH 0.25) and in a 0.5 M phthalate buffer solution (pH 5) without and with applied magnetic fields up to 0.6 T in different orientations to the electrode surface were performed. In sulfuric acid solution an increase of the diffusion-limited dissolution current density and a shift of the active-passive transition potential to more noble potentials was observed when the magnetic field was applied parallel to the electrode surface. In contrast, in perpendicular field configuration the diffusion-limited current density is lowered and the active-passive transition potential is shifted to less noble values. In phthalate buffer no significant influence of the magnetic field on the current density was observed in the active region, but a shift of the active-passive transition to less noble potentials occurred irrespective of the magnetic field configuration.The observed effects of a superimposed magnetic field on the anodic behaviour of iron are discussed with respect to an increase of the mass transport due to the Lorentz-force-driven magnetohydrodynamic (MHD) effect, the magnetic field gradient force and its interaction with the paramagnetic iron ions. The results of this paper show that the effect of the field gradient force can become very important due to the high magnetic field gradient at ferromagnetic electrodes.     

Polymerization‐induced phase separations in branched poly(methyl methacrylate) synthesis

Methyl methacrylate and ethylene glycol dimethacrylate or 1,6‐hexanediol dimethacrylate (HDDMA) were copolymerized in the presence of a nonsolvent (heptane) for poly(methyl methacrylate) (PMMA) to examine the phenomenon of polymerization‐induced phase separations (PIPS) in branched PMMA synthesis. The process was dependent upon the amount of nonsolvent and crosslinker in the reaction mixture. Gel particles were obtained in the majority of phase‐separated systems, and their formation was promoted by the preferential partition of monomer and crosslinker into the precipitated polymer phase during the phase separation process. Experimental data showed that, because of its lower solubility parameter, HDDMA can be used as crosslinker to minimize gel particle formation in systems where PIPS is present. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1462–1468, 2005     

LHGC型立环高梯度磁选机及其在陶瓷原料长石矿分选中的应用

我公司开发生产的LHGC型高梯度磁选机是一种节能、环保、有强制油冷却、有脉动作用的新型立环高梯度磁选机。该磁选设备已于2011年由9位专家做了技术鉴定。专家一致认为,这是一种国内外首创的磁选设备,其技术性能达到了国际领先水平。该磁选设备可以广泛地应用于金属矿物和非金属矿物的分选,尤其适用于陶瓷原料长石矿物的除铁提纯,长石经除铁提纯后其技术指标达到优良,经济效益十分显著。     

录像机磁头中有效磁导率的实验测定

一般地,录像机磁头的磁导率仅用一个圆环状磁头材料的磁导率测定值近似代替,这一圆环并不是真正的磁头。在本文中,我们通过一个简单的缝隙因子模型和一些磁头的实际测定数据,通过一个线性回归的方法,使得录像机磁头中有效磁导率的实验测定成为可能。     

高梯度磁分离铬盐浸出浆液中的铬渣--II.实验研究

应用高梯度磁分离装置对铬盐浸出浆液中的铬渣进行了实验分离,测量了有效分离时间与流体粘度、磁场强度和流体流速之间的关系. 实验结果显示,当对理论模型作适当修正后,实验测量结果与模型计算结果基本一致.     

LHGC型立环高梯度磁选机及其在陶瓷原料长石矿分选中的应用

我公司开发生产的LHGC型高梯度磁选机是一种节能、环保、有强制油冷却、有脉动作用的新型立环高梯度磁选机。该磁选设备已于2011年由9位专家做了技术鉴定。专家一致认为,这是一种国内外首创的磁选设备,其技术性能达到了国际领先水平。该磁选设备可以广泛地应用于金属矿物和非金属矿物的分选,尤其适用于陶瓷原料长石矿物的除铁提纯,长石经除铁提纯后其技术指标达到优良,经济效益十分显著。     

Microwave material processing—a review

Microwave heating is caused by the ability of the materials to absorb microwave energy and convert it to heat. This article represents a review on fundamentals of microwave heating and their interaction with materials for various applications in a comprehensive manner. Experimental studies of single, multimode, and variable frequency microwave processing were reviewed along with their applications. Modeling of microwave heating based on Lambert's law and Maxwell's electromagnetic field equations have also been reviewed along with their applications. Modeling approaches were used to predict the effect of resonances on microwave power absorption, the role of supports for microwave heating, and to determine the nonuniformity on heating rates. Various industrial applications on thermal processing have been reviewed. There is tremendous scope for theoretical and experimental studies on the athermal effects of microwaves. Some of the unresolved problems are identified and directions for further research are also suggested. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

LHGC强制油冷立环高梯度磁选机在石英砂和长石选矿中的应用

石英砂与长石是玻璃生产中常用的两种矿物原料,氧化铁是其中的主要有害成分,磁选是去除氧化铁的主要手段。本文论述了特制立环高梯度磁选机在这两种矿物原料除铁提纯中的应用和达到的主要技术指标,并对获得的经济效益作出了简要评价。     

Recent resist developments in Japan—a review

Several kinds of resist materials for microlithography have been developed in Japan. Poly(4-vinyl phenol) sensitized with 3,3′-diazidodiphenyl sulfone has been proved to be a high resolution negative deep UV resist with high sensitivity and good resistance to dry etching. The use of this resist enables a 1:1 projection printer to replicate fine patterns with 1 micrometer (μm) minimum feature size at the rate of 90 wafers per hour. Poly(methyl isopropenyl ketone) (PMIPK) has been investigated as a positive deep UV resist. Several resists composed of PMIPK with or without sensitizers are commercially available. Dry-developable photo- and deep UV resists comprising PMIPK and aromatic bisazides have been developed. Poly(glycidyl methacrylate) having the sensitivity of 0.4 micro Coulomb (μC)/per square centimeter (cm²) is now being routinely used as a negative electron beam resist in the fabrication of chromium masks. Recently, aromatic polymers such as chloromethylated polystyrene, iodinated polystyrene, chloromethylated poly(α-methylstyrene), poly(vinylnaphthalene) and its copolymers have been investigated as dry-etching resistant electron beam resists.     

Photoresponsive optically active polymers—a review

Photoresponsive macromolecules are of interest both as novel organic materials for applications in photodevices and as models for photomodulated biological processes. The presence in polymer chains of photosensitive groups and of chiral groups capable of inducing optical activity into the polymer is very useful for the analysis of photomodulated structural variations and allows storage of the light effect in the form of chiral information. Polypeptides bearing photochromic groups in the side chains are very convenient as the chiroptical properties of the peptide chromophore can be correlated to the backbone conformation. Thus polymers of L-aspartic acid, L-glutamic acid and L-lysine with azobenzene or stilbene groups attached covalently to the side chains are discussed in terms of photoinduced conformational changes and chiroptical information storage in the spectral region of the peptide and of the photoresponsive chromophore. Optically active photochromic macromolecules with hydrocarbon backbone, such as copolymers of (—)-menthyl acrylate with vinyl or acryloyl derivatives of azobenzene, stilbene and indolinospirobenzopyran, also show in some cases photodependence of chiroptical properties with evidence of at least local conformational changes as a consequence of light irradiation which can be used for chiral information.     

The membrane emulsification process—a review

Membrane emulsification has received increasing attention over the last 10 years, with potential applications in many fields. In the membrane emulsification process, a liquid phase is pressed through the membrane pores to form droplets at the permeate side of a membrane; the droplets are then carried away by a continuous phase flowing across the membrane surface. Under specific conditions, monodispersed emulsions can be produced using this technique. The purpose of the present paper is to provide a review on the membrane emulsification process including: principles of membrane emulsification, influence of process parameters and industrial applications. Small‐scale applications such as drug delivery systems, food emulsions, and the production of monodispersed microspheres are also included. Compared with conventional techniques for emulsification, membrane processes offer advantages such as control of average droplet diameter by average membrane pore size and lower energy input. Copyright © 2004 Society of Chemical Industry     

A dynamic buildup growth model for magnetic particle accumulation on single wires in high‐gradient magnetic separation

Magnetic fluids containing nano or submicron magnetic particles and their applications to food, biological, and pharmaceutical systems have recently attracted considerable attention. Magnetic particles can be collected efficiently in magnetizable matrices (e.g., iron wires) in high‐gradient magnetic separation processes. However, capture efficiencies based on results for clean, particle‐free, wires may be seriously in error because the particle accumulation on the wire distorts the flow and the magnetic fields, and thus influences the capture efficiency. A model is developed here in which the dynamic growth process is treated as a moving boundary problem, with the growing front tracked explicitly by marker points distributed evenly over its surface. The flow field and magnetic field are calculated using a finite element method, and a particle trajectory model is used to calculate the deposition flux on the surface. The marker point distribution and the buildup shape are updated at each simulation step. Simulation results show that, for weakly magnetic particles, the accumulation exhibits a smoothly growing front, whereas for strongly magnetic particles, an instability occurs, leading to dendritic growth. The capture efficiency decreases dramatically as particle accumulation increases; and this trend is more prominent for the transverse configuration than it is for the longitudinal configuration. The simulation results show good agreement with experimental results from the literature. © 2011 American Institute of Chemical Engineers AIChE J, 2012