## what type of ores can be concentrated by magnetic separation method? - askiitians

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## concentration of ore: definition, separation of two sulphide ores

Enrichment or Concentration of Ore: Ores obtained from Earths crust are never pure. Instead, they are usually associated with earthy and siliceous impurities (in addition to the impurities of other minerals) called gangue or matrix. These impurities have to be removed from the ore before the extraction of the metal is done. In this article, we will learn about different methods of concentration of ore.

The removal of unwanted earthy siliceous impurities (i.e., gangue or matrix) from the ore is called ore-dressing or concentration of ores. The process used to concentrate an ore is called the beneficiation process.

An ore after mining from the ground contains many unwanted impurities like sand, rocky materials, etc. These unwanted impurities, including earthy materials, rocks, sandy materials, limestone, etc., are called gangue.

The first step in metallurgy is to remove these unwanted impurities from the ore, to get a concentrated ore containing a much higher percentage of the metal. The method used to remove gangue from ore depends on the physical or chemical properties of the gangue and ores. Some of the methods used in the concentration of the ore include:a. Breaking and Crushing: Big masses of rocks containing the ore must be reduced to small lump so that they may be completely exposed to the action of the subsequent operations. Machines like crushers, etc., usually do it.b. Grinding and Pulverizing: Sometimes, some ores concentration and further treatment demand their reduction into a very fine state. Machines like grinding and pulverizing mills are used for this work.c. Flotation: Here concentration of the powdered ore is effected by taking advantage of differences in the behavior towards oil or water. Sulphides, for example, do not get wet, as do silica and most oxides when treated with water. They will therefore float on the surface while silica etc., will sink.d. Hand-picking: In case the impurities are quite distinct from the ores so that the naked eye may differentiate, these may be separated by hand-picking.e. Hydraulic washing or Levigation or Gravity separation: The process by which lighter earthy particles are freed from the heavier ore particles by washing with water is called levigation. For this purpose, the powdered ore is either agitated with water or washed with a running stream of water. Thus, the lighter gangue particles are washed away while the heavier ore particles settle down. Two common methods of gravity separation are described below:(i) Hydraulic classifier: In this method, the finely powdered ore is dropped through a hopper into a conical reservoir called a hydraulic classifier from the top. A powerful stream of water is introduced from the bottom of the reservoir. The lighter gangue particles are carried up by the current water and pass out along with water through the outlet provided near the top. The heavier ore particles get collected at the base of the cone. The conical shape of the reservoir helps reduce the velocity of water and thus prevents the ore particles from being carried away along with the stream of water.

(ii) Wilfley table: The other method of gravity separation is the Wilfley table. It is a wooden table having a slanting floor with riffles or grooves or cleats fixed on it.The pulverized ore is placed on the trays provided at one end of the table, and a stream of water under pressure is passed over it. Thus, a rocking motion is given to the table. The lighter gangue particles are carried away by the stream of water while the heavy ore particles get deposited in the grooves. The ore particles deposited in the groove move towards one side of the table due to the rocking motion given to the table and are finally collected. This method is used when the ore particles are heavier than the earthy or rocky gangue particles. This method is usually concentrated by the oxide ores iron (haematite), tin (Tin stone) and native ores of $${\rm{Au,}}\,{\rm{Ag,}}$$ etc.

f. Electromagnetic separation: This method of concentration is employed when either the ore or the impurities associated with it are magnetic in nature. For example, chromite, $$\left( {{\text{FeO}}{\text{.C}}{{\text{r}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{=FeC}}{{\text{r}}_{\text{2}}}{{\text{O}}_{\text{4}}}} \right)$$ an ore of chromium, magnetite $$\left({{\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}} \right){\text{-}}$$ an ore of iron and pyrolusite $$\left({{\text{Mn}}{{\text{O}}_{\text{2}}}} \right){\text{-}}$$ an ore of manganese being magnetic in nature, are separated from non-magnetic siliceous gangue by this method. Similarly, tinstone or cassiterite, an ore of tin being non-magnetic, can be separated from magnetic impurities like those of tungstates of iron and manganese, which are generally associated with this method.In this method, the powdered ore is dropped over a conveyor belt moving around two rollers one of which has an electromagnet in it. As the ore particles roll over the belt, the magnetic particles are attracted by the magnetic roller. As a result, two heaps are formed separately. The heap collected below the magnetic roller contains the magnetic particles, while the heap formed away from the magnetic roller contains the non-magnetic impurities. In the case of tinstone, the tungstate being magnetic fall in a heap under the magnetic roller while the ore particles that is $${\text{Sn}}{{\text{O}}_{\text{2}}}$$ fall in a separate heap away from the magnetic roller.

g. Electrostatic separation: This method is used for the concentration/ separation of ores, which are good conductors of electricity, while impurities are poor conductors of electricity. The method is based upon the principle that when an electrostatic field is applied, the ore particles, which are good conductors of electricity, get electrically charged and hence are repelled by the electrodes having the same charge and thus are thrown away. This method is used for the concentration /separation of $${\text{PbS}}$$and $${\text{ZnS}}$$ores occurring together in nature. The mixture of ores is powdered and dropped over a roller subjected to an electrostatic field. $${\text{PbS}}$$ being a good conductor, immediately gets charged and thrown away from the roller, whereas $${\text{ZnS}}$$is a poor conductor, does not get charged and falls vertically from the roller.h. Froth floatation process: This process is commonly used for sulphide ores and is based upon different wetting characteristics of ore and gangue particles. The finely powdered ore is mixed with water, pine oil (frother) and ethyl xanthate or potassium ethyl xanthate(collector) in a big tank. Then, the whole mixture is agitated with air. The ore particles wetted with oil come in the froth and are taken off, while impurities wetted with water settle at the bottom.

If the mineral to be concentrated consists of sulphides of two metals, then adjusting the proportion of oil to water is often possible to separate one sulphide from the other. Additional reagents called froth depressants to prevent one type of sulphide Ore particles from forming the froth with air bubbles. For example, sodium cyanide is used as a depressant to separate lead sulphide ore from zinc sulphide ore. It is because $${\text{NaCN}}$$forms a soluble zinc complex $${\text{N}}{{\text{a}}_{\text{2}}}\left[{{\text{Zn}}{{\left({{\text{CN}}} \right)}_{\text{4}}}} \right]$$which goes into the solution thereby preventing it from forming the froth. Under these conditions, only $${\text{PbS}}$$forms a froth and hence can be separated from $${\text{ZnS}}$$ore.

The bauxite ore contains aluminium in the form of $${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}$$along with $${\text{Si}}{{\text{O}}_2},$$ iron oxides and titanium oxide as impurities. The powdered ore is heated with a concentrated solution of $${\text{NaOH}}$$at $${\text{473-523}}\,{\text{K}}$$ and $$35-36$$ bar pressure. As a result, alumina is leached out as Sodium aluminate and $${\text{Si}}{{\text{O}}_2}$$ as sodium silicate leaving behind the impurities.

$${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{ + 2NaOH + 3}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{2Na}}\left[{{\text{Al}}{{\left({{\text{OH}}} \right)}_{\text{4}}}} \right]$$$${\text{Si}}{{\text{O}}_{\text{2}}}{\text{ + 2NaOH}} \to {\text{N}}{{\text{a}}_{\text{2}}}{\text{Si}}{{\text{O}}_{\text{3}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$$

The resulting solution is filtered to remove the undissolved impurities. Then it is cooled, and its $${\text{pH}}$$ is adjusted either by dilution or by neutralization with $${\text{C}}{{\text{O}}_2}$$when aluminium hydroxide gets precipitated. In this stage, the solution is seeded with freshly prepared samples of hydrated alumina to get it precipitated, leaving behind sodium silicate in the solution.

$${\text{2Na}}\left[{{\text{Al}}{{\left({{\text{OH}}} \right)}_{\text{4}}}} \right]{\text{ + C}}{{\text{O}}_{\text{2}}} \to {\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{.x}}{{\text{H}}_{\text{2}}}{\text{O + 2NaHC}}{{\text{O}}_{\text{3}}}$$The hydrated alumina is filtered, dried and heated to 1400 K temperature to give back pure $${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{.}}$$

$${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{.x}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{ + x}}{{\text{H}}_{\text{2}}}{\text{O}}$$

Some metals like gold and silver are extracted from their concentrated ores by leaching. They are dissolved in suitable reagents like acids or bases, leaving behind insoluble impurities. Then the metal is recovered from the solution by precipitation or crystallization. For example, Silver ore is leached with a dilute solution of sodium cyanide. As a result, silver dissolves, forming a complex sodium dicyanoargentate(I). This solution is further treated with scrap zinc to get the precipitate of silver.$${\text{A}}{{\text{g}}_{\text{2}}}{\text{S + 4NaCN}} \to {\text{2Na}}\left[ {{\text{Ag}}{{\left( {{\text{CN}}} \right)}_{\text{2}}}} \right]{\text{ + N}}{{\text{a}}_{\text{2}}}{\text{S}}$$$${\text{2Na}}\left[{{\text{Ag}}{{\left({{\text{CN}}} \right)}_{\text{2}}}} \right]{\text{ + Zn}} \to {\text{N}}{{\text{a}}_{\text{2}}}\left[{{\text{Zn}}{{\left({{\text{CN}}} \right)}_{\text{4}}}} \right]{\text{ + 2Ag}}$$

Similarly, native gold is leached with a potassium cyanide solution, and it is recovered from the solution by the addition of scrap zinc.$${\text{4Au + 8KCN + }}{{\text{O}}_{\text{2}}}{\text{ + 2}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{4K}}\left[{{\text{Au}}{{\left({{\text{CN}}} \right)}_{\text{2}}}} \right]{\text{ + 4KOH}}$$$${\text{2K}}\left[{{\text{Ag}}{{\left( {{\text{CN}}} \right)}_{\text{2}}}} \right]{\text{ + Zn}} \to {{\text{K}}_{\text{2}}}\left[ {{\text{Zn}}{{\left( {{\text{CN}}} \right)}_{\text{4}}}} \right]{\text{ + Au}} \downarrow$$

All materials found on Earth are made up of chemical elements. Most elements found on Earth are metals and nonmetals. There are numerous ways to carry out the concentration of ores. The correct method is chosen based on the physical andchemical properties of the metal. This article discussed important procedures like hand-picking, hydraulic washing, magnetic separation, froth floatation method, and leaching processes for the concentration of the ores.

Q.1. Which method is used for the concentration of sulphide ore in metallurgy?Ans: Froth flotation method isusedfor theconcentrationof sulphideores. The method is based on the preferential wetting properties with the frothing agent and water. Example:Galena $$\left({{\text{PbS}}} \right).$$

Q.2. What is the concentration process for the ore?Ans: The removal of the gangue fromthe oreis known asconcentrationor dressing or beneficiation. There are numerous methods ofconcentration,and the methods are chosen based on the properties of theore.

Q.3. What is meant by the concentration of the ore, and why is it very important?Ans: Concentration of oremeans removal of impurities by physical or chemical methods. The impurities like sand, rocky materials, limestone, mica, etc., present in theoreare called gangue or matrix.Concentrationisnecessaryas it is easy to extract a metal when the impurities are removed at the beginning.

Q.4. Which type of ore is concentrated by froth flotation?Ans: Sulphide ores are concentrated by the froth-flotation process. Only sulphide ores are concentrated by this method because pine oil selectively wets the sulphide ore and brings it to the froth.

Q.6. What is the gravity separation method for the concentration of ore?Ans: Gravity separation, also called hydraulic washing, is a method of separation based on the difference in the specific gravity of the metallic ore and gangue particles.

## what is concentration of ore? definition, physical & chemical methods - biology reader

To obtain a pure metal from ore, the method of ore concentration is a very crucial step. For the extraction of metal, it is necessary to separate ore from the gangue particles. Ore found in the earth contains many impurities like sand, grit, rocks etc. which are collectedly known as Gangue.

The concentration of ore is the first step of metal extraction. There are different types of ore like native, oxidized, sulphurized and halide, which can be concentrated by various physical and chemical methods.

The ore concentration is defined as the chemical process of eliminating impurities like sand, rocks, silt, grit etc. from the ore to extract the metals. In simple words, the concentration of ore is the method of separating ore from the gangue, as the gangue or matrix particles are the valueless substances that are of no use. The ore can be concentrated or separated by both physical and chemical means. The ore obtained after the completion of the ore concentration is called concentrate.

Ore can define as a solid substance (like a rock) that contains minerals or combination of minerals, from which the metal can be extracted by a series of methods like the concentration of ore, isolation of metal and refining of the metal.

As the ore is found in the earths ground surface, it contains unwanted earthy materials like rocks, sand, silt, and many other impurities colloquially termed as gangue. The concentration is basically the separation of something useful out of worthless. Thus, by concentrating ore from such impurities, we can actually extract and refine metals. Various physical and chemical processes are employed to concentrate or separate ore from the gangue matrix.

It was the traditional method of concentrating ore directly with hands. In this method, the gangue or adhering solid matrix is separated from the ore with a hammers help. The separation and identification of gangue are made based on the differences in colour or lump shape.

It is also called Gravity separation or Levigation. In the hydraulic wash, the ore is separated from the gangue by the principle of gravitational force. The ore is first crushed into fine particles or powdered form. Then, the powdered ore is passed through the water current. As the ore is more substantial than the gangue particles, it will settle behind, and the gangue will float away through the stream of water. The process of hydraulic washing is accomplished by Hydraulic classifier or Wilfley table. This method is widely used for the concentration of oxide and carbonate ores.

The magnetic separation method separates ore from the gangue particles based on the magnetic properties of either ore or matrix. In this method, the ore is finely crushed and passed over the magnetic roller, where one is magnetic, and the other is nonmagnetic. The magnetic ore particles will attract and attach to the magnetic roller, and the non-magnetic gangue particles will repel and fall into the heap from the conveyer belt. Example: Fe (CrO2)2 (Chromite) is a magnetic ore, separated from the non-magnetic silicious gangue.

In this process, finely ground ore or we can say pulp of ore is passed into the bioreactor along with little oil. The oil which is generally used in the froth floatation process is pine oil. The bioreactor contains water onto which the mixture of ore plus oil is added through an inlet. Then, the mixture of ore, oil and water is thoroughly mixed or agitated by the rotating paddle (comprises impellers) that allows uniform mixing of all the components. There is constant airflow inside the medium, which leads to the formation of mineral froth (appears as a supernatant). Froth contains mineral particles that can be collected by transferring the mineral froth into the other bath, in which the ore free from gangue will settle down.

## how many types of magnetic separators? - jxsc machine

Magnetic separation is an effective mineral processing method to separate the minerals based on the magnetism difference. Magnetic separator machine can effectively select a large number of magnetic minerals, such as magnetite, hematite, limonite, manganese siderite, wolframite, ilmenite, manganese ore, manganese carbonate, metallurgical manganese ore, iron ore, kaolin, manganese oxide ore, rare earth ore.

Wet type? Fine particle and coarse particle? Strong magnetic? . . How many kinds of magnetic separators equipment? Frankly, there are many classification methods of magnetic separator types, join us to solve the puzzle.

According to the state of the material, the magnetic separator is divided into dry type magnetic separator and wet type magnetic separator. Dry magnetic separator refers to the material keep dry, dont need to mix with water in the magnetic separation process. The material for wet magnetic separator must be mixed with water or other media.

The dry magnetic separator generally does not need a tank for accommodating the slurry, and the material is conveyed by a vibrating feeding device, and a dustproof device is often provided. The wet magnetic separator has a tank to accommodate the slurry to maintain the fluidity of the material, and the pump is usually transported by a slurry pump.

Dry magnetic separation function for bulk, coarse particle separation, but also fine mineral separation, while wet magnetic separator can not sort large bulk minerals, most are effective for fine or even fine particles, except for a few models that can select coarse particle. HGMS (high gradient wet magnetic separator) can sort micron-sized materials using a suitable magnetically permeable medium.

Dry magnetic separator requires low water content, dry materials, good liquidity, do not adhesion, agglomeration. The wet magnetic separation operation has certain requirements on the slurry concentration. There is no obvious limit on the concentration of coarse magnetic separation, but the material concentration should not be too low to effectively control the negative fluid force during the mineral processing operation. When magnetically selecting fine particles, the concentration is required to be high to ensure the recovery of magnetic minerals.

Dry weak magnetic separators have features like a simple process, low investment, low water consumer. However, the bottleneck of the dry cylinder magnetic separator is that the dust is difficult to control, so as the environmental protection requirements become stricter, the dry type magnetic separation is gradually replaced by the wet weak magnetic separator. At present, the fine-grained dry magnetic separation machine is only used in the water shortage area and severe cold area.

According to the magnetic field strength, magnetic separator is divided into three types: weak magnetic separator (low intensity magnetic separator), medium magnetic separator and strong magnetic separator (high intensity magnetic separator). The weak magnetic separator is from several hundred to 3000 Gs; the strong magnetic separator generally refers to 3000Gs to 6000 Gs, and the medium magnetic field magnetic separator between the two.

The reason why it is classified according to the strength of the magnetic field is related to the magnetic properties of various common minerals (another post Magnetic Mineral Classification). However, it is necessary to know that there is no absolute standard for different magnetic strength and their matched equipment.

In the actual magnetic separation machine, the magnetic field strength ranges from hundreds of Gauss to 20,000 Gauss, some even exceed 20,000 Gauss, but it is rarely used in general beneficiation production. Excessive magnetic field strength will lead to weak magnetic minerals to agglomerate that is not conducive to beneficiation. So the upper limit of the magnetic field strength of the strong magnetic separator is 20000Gs.

On the working surface of various magnetic separators, the magnetic field strength varies at different points and in different ranges, and the working magnetic field is a non-uniform magnetic field. Generally, the value of the magnetic field strength expressed refers to Max. magnetic strength, some factories may list the average value.

According to the type of magnetic field, the magnetic separator is divided into permanent magnet magnetic separator and electromagnetic magnetic separator. The permanent magnet magnetic separator uses a permanent magnet material such as ferrite or neodymium iron boron to generate a working magnetic field, and the electromagnetic magnetic separator uses a magnet with a yoke, a solenoid, and a magnet to generate a magnetic field.

The magnetic field strength of the permanent magnet magnetic separator is fixed, but the different action areas in the magnetic separation working surface can be designed to have different magnetic field strengths. The electromagnetic magnetic separator can adjust the whole magnetic field, but the magnetic field strength values in the working surface are a balanced, uniform magnetic field.

The magnetic energy of the permanent magnet magnetic separator is low, while the electromagnetic separation requires high energy consumption to generate the excitation current. The energy consumption per unit of the permanent magnetic separator is much lower than that of the electromagnetic magnetic separator.

According to the structure of the main working part of the magnetic separator, it is divided into cylindrical (drum) magnetic separator, roller magnetic separator, disc magnetic separator, ring magnetic separator, in addition, have rotor magnetic separator, belt magnetic separation, conical magnetic separator, but these types of magnetic separators have been used less.

According to the way the magnetic field strength changes: 1) Constant magnetic field magnetic separator. Using a permanent magnet material and a direct current electromagnet, a solenoid, or the like as a magnetic source, the magnitude and direction of the magnetic field strength do not change with time. 2) Alternating magnetic field magnetic separator. An electromagnet that is connected to an alternating current is used as a magnetic source. The magnitude and direction of the magnetic field strength changes over time. 3) Pulsating magnetic field magnetic separator. An electromagnet that simultaneously transmits direct current and alternating current is used as a magnetic source. The magnitude of the magnetic field varies with time, but the direction does not change. And pulse Similar to the dynamic magnetic separator, the use of pulsating water flow causes the slurry to pulsate, affecting the sorting force of the magnetically selected mineral. 4) Rotating magnetic field magnetic separator. A magnet is used as the magnetic source, and the magnetic pole rotates around the axis. The magnitude and direction of the magnetic field strength changes over time.

According to whether the magnetic mineral is reversed in the magnetic field of the magnetic separator, it is divided into a mineral reversal magnetic separator and Nonreversal magnetic separator. The mineral reversal magnetic separator can effectively improve the concentrate grade, and the Non-reversal magnetic separator can select the refractory weak magnetic minerals.

According to the minerals, it also can divide into such as magnetite magnetic separator, hematite magnetic separator, manganese ore magnetic separator, quartz sand magnetic separator, NdFeB magnet, nickel, etc.

In addition to the types listed above, there are many ways to classify magnetic separators. Although each manufacturer has a self-classification method, it lacks standards. In the magnetic separator model selection stage, most prefer using mixed name, such as the hematite wet magnetic separator, actually indicate that the sorting mineral is hematite, and the ore dressing method is wet type, but does not show us whether the magnetic separator is a permanent magnet type or an electromagnetic type, and neither indicate which magnetic separation structure the equipment is.

JXSC, 35 years Chinese magnetic separators manufacturer, provides laboratory use small machine, and industry use effective magnetic separators, widely used in the mining industry around the world (Successful cases in UK, South Africa, South Korea, Uganda, Pakistan, Zambia, Tanzania, India, Thailand and so on). Contact us for more details about working principle, specification, price list, dealer and oversea supplier, troubleshooting solutions, operation and installation guidance, etc.

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