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By W. S. Urbanski, A. L. Devernoe, M. S. Walker

Theory and practice are described for a new processing method capable of precise mineral separations based primarily on differences in particle specific gravities at specific gravity split points from 1.5 to 21.0 and beyond. Separations are analogous to those achieved using rotating heavy media, except that the effective specific gravity of the fluid is created magnetically using a relatively dilute, low-viscosity, water-based magnetic fluid. Results reported here for a large, laboratory flow-through separator include: 1) 99% grade with 97% recovery in single pass separation of a suite of heavy minerals from quartz at I0 kg/h, 14 tph/rm2 of duct cross section, 2) 90% grade and recovery in single-pass separation of mixtures of sand-size, non-magnetic rutile (4.23 specific gravity) and zircon (4.72 specific gravity) at throughputs of 35 kg/h, 47 tph/rm2 of duct cross section, 3) partition curves having Ep90-10 transition widths 5% or less of mineral specific gravities, and 4) essential confirmation of the theory.

Jan 1, 1991

By Shujian Jia, Mingming Song, Gaoyang Song, Bo Song, Yuhou Yang

An innovative method is investigated to separate inclusion particles from liquid metal by super gravity. To make clear the characteristics of the inclusion separation, Al melt containing MgAl2O4 particles with diameters less than 150 μm has been treated under various super-gravity fields. The thickness of particle-accumulated layer formed at the bottom of the sample and the area fraction, number density and size of inclusions were measured. It is found that the thickness of the particle-accumulated layer decreases and the area fraction of particles at this location increases with the increase of super-gravity field. With the gravity coefficient G=500, time t=2 min, and temperature T=1023 K, it is hardly to find any solid particles in the upper and middle areas of the sample and the separation efficiency is up to 90%.

Jan 1, 2015

By Jin-tao Gao

In order to recover Ti resource from titanium bearing blast furnace slag, a new technology to separate perovskite phase from CaO-TiO2-SiO2-Al2O3-MgO system by supergravity is researched. In the condition of gravity coefficient of 750g, treatment temperature of 1305°C and time of 20min, the significant layers appear in samples which are obtained by means of centrifugal treatment. Along the direction of the supergravity, the volume fraction of perovskite phase increases gradually, and the equivalent diameters of perovskite phase crystals increases with the area approaching to the bottom of the sample. It is indicated that TiO2 is enriched in the bottom of sample as concentrate with a recovery ratio of 74.05% by supergravity treatment.

Jan 1, 2014

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

Spent automobile catalyst is an important secondary resource of PGMs (platinum group metals) and the recovery is significant. Various methods of recovery technology have been reported and applied in practical production, including pyro- and hydrometallurgical processes. Since the grade of PGMs in the catalysts is so low, approximately 0.5 wt. %, the present recycling technologies require high energy-consumption, it is of great significance to enrich the PGMs with some energy saving physical separation methods as a pretreatment. Automobile catalyst is usually composed of cordierite phase as a substrate and alumina phase, with PGMs, which covers the cordierite phase. We adopted the quenching pretreatment, one method of thermal shock, to generate micro-cracks between the two phases and separate the alumina phase from cordierite. Quenching was carried out by heating the catalysts in an electric furnace of different temperatures followed by rapid soaking into cold water. It was found that the phase boundary between alumina and cordierite was broken in the quenching and selective separation (detachment) of alumina from the cordierite could be achieved in the following surface grinding. The effect of quenching was checked by microscopic observation, hardness measurement, and chemical analysis. This paper figures out the stress formula of the quenching process, which is largely connected with layer thickness and temperature gradient by using an FEM (Finite Element Method) simulation and clarifies the mechanism of crack generation in the quenching process. Keywords: automobile catalyst, PGM, quenching process, FEM

Sep 1, 2012

By U. Runolinna, R. T. Hukki

Preliminary separation of precious metals by flotation can offer a simplification of the conventional method of treatment of anode slimes. Laboratory flotation experiments show that rich gold and silver concentrate can be obtained with excellent recoveries.

Jan 11, 1950

By D E. G Connelly, K Y. Wong

Gold at the Harbour Lights Mine (HLM), WA occurs principally in pyrite (Py) and arsenopyrite (AsPy) minerals rendering it inaccessible to direct cyanidation. Froth flotation produces a concentrate with low mass recovery and with high recoveries of sulfides. After investigating several alternatives, a novel flotation process has been developed to separate the concentrate into pyrite and arsenopyrite rich fractions. The pyrite fraction is finely ground and cyanide leached, while the arsenopyrite is treated off-site. This paper describes the separation process from laboratory bench scale through to commercial operation at the HLM gold plant.

Jan 1, 2005

By Bahram Rezai

Fine particles float poorly and less-selectively under normal flotation conditions. One of the promising methods for fine minerals is the utilization of the principle of Flocculation. Hydrophobic flocculation flotation (or floc flotation) was tested on a magnetite concentrate that was finely ground to be micron particles, for producing a concentrate with sulphur grade less than 0.1%. After that, slurry dispersing with water glass as dispersant, pyrite fines were subjected to hydrophobic flocculation induced by xanthate and a small amount of kerosene then the slurry was transferred to a flotation cell for recovering the hydrophobic flocs. The experiments carried out indicated that through one-step rougher and two-step cleaner flotation, sulphur grade was reduced from 1% to 0.1%. It has been found that the separation efficiency of the floc flotation process closely correlates with the main parameters of hydrophobic flocculation such as xanthate addition, conditioning time and kerosene addition.

Jan 1, 2006

By B. Mishra

The application of various bydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, eg. metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been 'investigated and suggested for dealing with some of these wastes' and scrap material. The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained? from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EMI' and decontamination and decommissioning [D&D].

Jan 1, 1996

By B. Mishra, W. A. Averill

"The application of various hydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, ego metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been investigated and suggested for dealing with some of these wastes and scrap material.The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EM] and decontamination and decommissioning [D&D].IntroductionThe high temperature carbothermic or metallothermic smelting reduction methods for metal production are associated with the generation of significant quantity of waste as slags, flue dusts, sludges, residues, effluent salts etc. Certain hydrometallurgical processes also generate lots of aqueous waste due to the inherent nature of the technique. Also, the gas-based reduction processes are not applicable to many stable metal compounds, such as alumina, titania, beryllia, lanthanide and actinide oxides, etc. due to thermodynamic considerations. All these methods cause substantial environmental hazard. There is a need to develop alternative processes which have low waste or ideally a ""zero-waste"" generation.Pyrochemical processes using molten salts provide a unique opportunity for the extraction and refining of many reactive and valuable metals either directly from the beneficiated ore (aluminum, beryllium, neodymium, plutonium, uranium, etc.) or from other process effluent that contain reactive metal compounds. The processes reduce metal compounds electrolytically (A12O 3 and BeCI2) on a carbon anode or by calciothermic reduction (Po, Nd). The by-product, in the latter case, is a calcium oxide saturated halide salt. The waste-treatment to recycle the halide has to be done as a separate step or stored as a contaminated waste. A successful separation technology can provide a new insight to the waste minimization strategy for the nuclear industry."

Jan 1, 1996

By N. S. Narayanan

Monazite, one of the major sources of rare earths, is normally opened by digestion with hot concentrated caustic soda solution. Caustic digestion dissolves phosphate and leaves a hydrated mixed metal oxides cake containing thorium, uranium and rare earths. By leaching this cake with hydrochloric acid at pH 3.0 to 3.2 bulk of the rare earths are preferentially removed and separated. The slurry left after removal of major portion of rare earths contains all the thorium and uranium present In the feed monazite. In addition this slurry also contains substantial quantities of rare earths. Solvent extraction tests were carried out to develop a process to separate rare earths, thorium and uranium present in the mixed chloride solution obtained by dissolving the above slurry in hydrochloric acid. Based on these tests a solvent extraction flow sheet was developed with di-2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester as the extractant. The details of experimental work and results obtained are discussed and a flow sheet for processing monazite Incorporating the new process is suggested.

Jan 1, 1997

By Linfeng Zhou, Rong Sun, Guanghui Li, Zhiwei Peng, Tao Jiang

The effects of microwave roasting on separation of rhenium (Re) and molybdenum (Mo) from a molybdenite concentrate have been investigated based on evaluation of the heating characteristics of the concentrate in the microwave field. The results show that a variety of operating variables, namely microwave power, sample weight, sample geometry, roasting temperature, roasting time and atmosphere significantly impact on the volatilization rates of Re and Mo. The optimum conditions for Re-Mo separation are microwave power 1300 W, sample weight 20 g, sample geometry pellets, temperature 600 oC, time 1.5 h, and atmosphere 20%O2. Under these experimental conditions, the volatilization rate of Re reaches 88.12%, while that of Mo is just 5.15%. Microwave-assisted roasting provides an alternative route to separating Re and Mo from molybdenite concentrate.

Jan 1, 2016

By A. Khoshnevisan

Molybdenum resources around the world are mainly associated with porphyry copper ores. Molybdenite (MoS2) is the main Mo mineral that has rhenium in its crystal lattice. This paper investigates the recovery of rhenium and molybdenum from a molybdenite concentrate using a hydrometallurgical treatment method. The molybdenite concentrate is leached with nitric acid and subjected to solvent extraction to recover and separate rhenium and molybdenum from the leached liquor. The effects of pH and the chemicals? concentration on extraction characteristics of Mo and Re are investigated to define the best condition for selective extraction of these metals. The tested leached liquor contained of 8.2 g/L Mo, 1.5 g/L Fe, 0.5 g/L Cu and 60 ppm Re. A good extraction efficiency, up to 94%, was achieved for Re from the leached liquor, where the extraction of other metals, such as Fe and Cu, was negligible. In particular, at very low pH, rhenium is extracted selectively from solution, while the extraction of molybdenum is less than 10%. After removing rhenium, molybdenum was extracted with LIX984N. The selectivity of molybdenum extraction over other metals in solution was significant. Nearly 94% of molybdenum can be extracted from the solution at a pH value of -0.12, without any interference from other metal ions such as copper and iron.

By Xi-Shan Li, Qian Li, Yong-bin Yang, Tao Jiang, Jie Ge

Compared with other pretreatments of sulfur & arsenic-bearing gold, double-layered pellet roasting has an advantage that sulfur dioxide and arsenic trioxide volatilizing from this refractory gold ores can be solidified into the coating without emission during the roasting. However, the separation of coating from roasted double-layered pellet should be focused on in the novel pretreatment. Based on the difference of physicochemical characteristics between roasted solidified coating and pellet core, several separation methods including grinding, drop impact and water quenching method had been systematically studied in this paper. The results showed that magnetic and gravity concentration could not obtain a satisfactory separation effect. The optimum separation rate of grinding was only 38.94% at grind time 12min, but it increased to 85.05% by drop impact under drop height 0.75m, drop times 20 and impact angle 45°, and that of water quenching taking advantage of slaking reaction of lime could approach 75.32%.

Jan 1, 2015

By Hongmin Zhu, Suning Liu, Kai Huang

"Recovery of silicon particles from the cutting slurry for the manufacturing of solar grade silicon is very important to recycle this kind of special resource. The challenge is to separate the silicon particles from the mixed abrasive particles which contain SiC. Various methods such as sedimentation, centrifugation, and flotation have been conducted, while in present work, a simple and effective novel method was proposed to study the separation of Si and coexisting SiC particles in the cutting slurry. The new process is based on the size difference between the two kinds of microparticles. And the membranes with the different pore sizes of 1µm, 2µm, 3µm and 5µm were used to test the pass ratio and separation efficiency of the suspension. Results shows that the effective separation of Si and SiC microparticles was obtained under the optimal conditions, and indicating great potential of practical enrichment of Si from the coexisting abrasive particles.IntroductionWith the development of the world economy, energy shortage and environment problem is becoming more and more seriously. Solar energy, which is regarded as one of the most important new energy in the word, has received much attention and interest from the scientists [1, 2]. More than 80% solar cells are manufactured by the high purity polysilicon as the raw material. The main process of producing silicon wafer is by multi-wire slicing. In this slice processing, large amount of slurry is produced. The slurry contains more than 30% wt silicon powder, silicon carbide powder as the abrasive, scraps of metal chips, as well as cutting abrasive suspension polyethylene glycol (PEG). The high-purified silicon powders are worth recycling and reusing as the materials for preparing solar-grade silicon though it is a big challenge [3].Most of the current studies were focusing on the recycling of the silicon carbide and PEG, while work on the recycling of the high-purified silicon is not so been focused since there is lacking of very effective separation and recovery technologies till up now. Nishijima utilized the method of superconducting magnetic to recycle the abrasive [4]. Wang applied a combinational process of chemical treatment, high-gravity centrifugation, high-temperature precipitation technique and directional solidification to enrich the silicon [5]. And other purification methods, such as centrifugation [6], froth flotation technologies [7], electrical filed separation [8] and phase-transfer process [9] have been employed. The disadvantages such as using poisonous media or complex equipments decrease the feasibility and efficiency of the above mentioned techniques."

Jan 1, 2014

By Hao Deng, Hongmin Zhu, Jichao Li, Kai Huang

"Silicon and silicon carbide mixing micropowders obtained from the saw cutting industry of polycrystalline silicon ingot is separated by a simple sequential sedimentation. The Zeta potentials of the powders in the aqueous suspension are adjusted by varying the pHs with dilute acid or alkaline reagents. The dispersion and aggregation content of the microparticles is significantly influenced by pHs, and so their settlement velocity in the same hydraulic conditions are quite different, and silicon powders tend to suspend in the upper section of the suspension for its finer size and smaller density under the stronger Zeta potential repulsion force. The original content of the cutting powders with 30%wt silicon are separated into the Si-rich and SiC-rich powder respectively, and 62%wt Si-rich powder can be obtained after 4 times of sedimentation under pH = 8.0, showing the great potential for Si and SiC powder separation and recovery in a cost-effective way.IntroductionWith the fast development of photovoltaic (PV) technology these years, the market demand for the solar-grade high pure silicon material significantly increased, making the silicon recycling and recovery from the wire sawing slurry profitable and attractive[1]. Waste silicon slurry was produced in the multi-wire sawing process of a silicon ingot by using an ethylene glycol-based solution and silicon carbide abrasives as the slicing system. During this slicing process, about 30% of the silicon ingot will become the waste as the fine particles suspended in the slurry, which mainly consists of silicon kerf-loss particles, SiC fragmental particles, tiny iron fragments from the worn sawing wire and ethylene glycol-based solution [2]. The separation of above individual component is usually easy except for Si and SiC fine particles for their quite similar properties. So the biggest challenge for the effective recovery and recycling of silicon particles from the wire sawing slurry actually lies in the mutual separation of silicon and silicon carbide particles."

Jan 1, 2012

By J. A. Bartnik

Flocculation, the process of coagulation or coalescence of finely divided particles, is commonly used in separating fine solids from fluids. Forces disposing of the particles to flocculate include: ionic forces of attraction, secondary entropic forces, and magnetism. Magnetic flocculation is due to a physical magnetizing process which affects suspended ferromagnetic particles. Such particles, after exposure to magnetic fields strong enough to cause reorientation of the particles and alignment of the induced magnetic poles, tend strongly to retain this induced magnetism, as the magnetic retentivity of ferromagnetic particles is a linear function of its specific surface.1 Thus, because they become small magnets with high residual magnetism, the particles become and remain attracted to one another, forming large agglomerates. Fine magnetic particles close to domain size can exhibit energies of the magnetization of the order of 105 ergs/cm3,2 which is many times greater than the energy affected by chemical flocculents. Therefore magnetic flocculation can be used to agglomerate particles having surfaces ionized with like charges and only a minute quantity of ferromagnetic material will be necessary to develop sufficient force to overcome the repulsive ionic forces and hold together relatively large masses of fine solid agglomerates suspended in fluids. Since flocculation occurs after the fine suspension passes through a magnetic field generated by magnets surrounding a pipe section, the simplicity of the process and economic advantage makes magnetic flocculation very attractive.

Jan 1, 1971

By C. Wen

In Huoqiu region of Anhui Province, Fe2O3 occurs mainly in the form of specularite. Besides quartz, the gangue minerals include iron-bearing silicates such as chlorite and sericite which account for about 10% of the total gangue. The separation effect of conventional collectors is poor in the flotation of the minerals, that is, the average grade of iron concentrates is only 60-62%. Using the developed amphoteric collector can successfully realize not only the separation of specularite from various gangue minerals with results of iron concentrate grade above 65% and iron recovery of above 80% but also low temperature flotation at 15°C.

Jan 1, 2012

By A. Hasbi Hassan

Stibiotantalite is a relatively rare mineral not commonly found in the major tin districts of the world, and its separation characteristics have not been documented adequately in the literature. The investigation described here has been carried out on a sample taken from a commercial tin concentrate containing a significant amount of stibiotantalite which would have to be substantially removed before the tin concentrate was smelted. The sample originated from Greenbushes, Western Australia. A mineralogical analysis was performed on the sample with the aid of the Frantz Isodynamic separator 1 and the results presented in Table 1. A screen analysis was also performed, and the results presented in Table 2. The minerals were found to be substantially liberated.

Jan 8, 1979

By A. H. Hassan

Stibiotantalite is a relatively rare mineral not commonly found in the major tin districts of the world, and its separation characteristics have not been documented adequately in the literature.

Aug 1, 1979