M. Takayasu

Generalization of HGMS theory: The capture of ultra-fine particles

A generalized HGMS theory describing particle capture of ultra-fine particles is formulated and the conditions for the appearance of the dynamic and static buildup are analyzed. A particle size criterion for the generalized and conventional theories to become coincidental is established. Typical examples of capture of paramagnetic, diamagnetic and ferromagnetic particles are used to illustrate the consequences of the new theory.

Magnetic separation of submicron particles

The application of high gradient magnetic separation to the capture of submicron-sized particles is studied. The steady state solution of the diffusion equation applicable to diffusion processes taking place under the influence of external forces is obtained. The relevance of the critical particle size to the phenomena of dynamic and static capture is discussed for various materials ranging from ferromagnetic to diamagnetic. The experimental results obtained are shown to be in satisfactory agreement with the theoretical predictions.

HGMS studies of blood cell behavior in plasma

Magnetic behavior of human blood cells in plasma was studied in High Gradient Magnetic Separation (HGMS) with the single wire technique. Human venous blood was oxygenated or deoxygenated by passing it through a gas-permeable tubular membrane with oxygen or nitrogen gases on the outside. The rate of collection of red blood cells in the deoxygenated blood havinz Hematocrit 9 - 45% was determined by observing the increase in radius of cell collection on the wire. Effects of hematocrit and velocity of blood on buildup were determined. At low red cell concentration, the magnetic susceptibility of individual red blood cells was determined using trajectory analysis. Particles of unknown type were found with susceptibility values different from red blood cells. Diamagnetic behavior of white cells in plasma was confirmed. The experimental conditions of this study are more physiologic than the Saline dilution and chemical reducing agents employed by others in previous studies.

Diamagnetic capture in single wire HGMS

Collection of diamagnetic particles is shown to be made possible and practical in HGMS by dissolving a paramagnetic salt in the slurry. After a brief review of theoretical concepts it is shown that forces in diamagnetic HGMS collection can be made comparable to those in paramagnetic particle collection. Results of diamagnetic particle buildup with time on a single nickel wire in the axial configuration are shown to follow a similar law as in the paramagnetic case. Pictures of diamagnetic buildup on a single wire are given.

Application of magnetic susceptibility gradients to magnetic separation

Particle separation in a magnetic colloidal fluid with a susceptibility gradient created by means of a Frantz‐Isodynamic magnet is described. The positions where particles and fluid are in equilibrium are a function of the particle magnetic susceptibility only. This method allows magnetic separation of several materials with a wide range of magnetic susceptibilities in a single separator with multiple dividers. A model separator was constructed. The magnetic gradient of the Frantz magnet and the concentration gradient of the magnetic colloids were calibrated. Separations were carried out using fine particles of Mn2P2O7, CuO, and Al2O3. The results confirm the feasibility of this method. The experimental data agree quite well with calculations based on the calibrated concentration gradient.

Diamagnetic particle capture and mineral separation

A method has been developed to collect diamagnetic particles and to separate diamagnetic components from a critical mineral resource, in this case, aluminum minerals from alunite ore. A study of matrix design for this purpose and for enhancement of the magnetic force by the use of a paramagnetic liquid has resulted in particle collection from model diamagnetic particle slurries and separation of diamagnetic ore components.

Selective seeding for magnetic Separation

Selective seeding utilizes surface chemistry to bond a desired mineral or minerals to introduced ferromagnetic seeds. Experiments were performed using finely ground Al(OH) 3 (gibbsite), SiO 2 (quartz), and Fe 3 O 4 (magnetite). The mineral particles were screened and only those having grain sizes between 20 and 2 μm were used. The materials were dispersed in a water slurry with 5% solid contents by 100 ppm Na 2 S and/or 100 ppm NaF. Two ppm polyacrylamide-acrylate was employed to flocculate Al(OH) 3 and Fe 3 O 4 . Magnetic separation in a HGMS coarse stainless steel wool model filter removed 73% of the SiO 2 and the Al(OH) 3 was upgraded from 40% to 69% with 93% yield. Repeated dispersal both chemically and mechanically with subsequent flocculation resulted in further upgrading of Al(OH) 3 to 79% with 87% recovery after the 3rd stage. Magnetite was finally recovered at 92% purity with 83% yield.

Viscosity effects in single wire HGMS studies II

The effect of the carrier fluid viscosity on the buildup of particles in single wire HGMS was studied for the transverse and longitudinal configurations. The collection of Mn 2 P 2 O 7 particles on a nickel wire from a glycerol-water solution was observed by means of a closed-circuit television system. Experimental results for the buildup of particles with time are given and compared with calculations based on a simple model for the buildup process for the longitudinal configuration for upstream buildup. In the longitudinal configuration, increasing amounts of buildup downstream with a corresponding decrease of buildup upstream on the collecting strand, with increasing carrier fluid velocity are again reported.

The collection of strongly magnetic particles in HGMS

Abstract The process of collecting strongly magnetic particles is studied both experimentally and theoretically in a single wire arrangement of high gradient magnetic separation. It is found that for such particles the build-up consists of two regions: a compact build-up region close to the collection wire, and a region of particle chains, stretching from the compact build-up along the direction of the magnetic field. The chains are not entirely stable. The separation between them is found to depend on their length, the magnetization and size of the captured particles, and the magnetization of the HGMS collector.

Status of magnetic separation

Abstract After a brief review of high gradient magnetic separation the capture process and filter design for strongly magnetic particles—magnetite—is discussed. A method for selective capture of diamagnetic particles is described and experimental results are given.