Flotation method is one of the main methods of mineral processing . As long as it is the process of selecting mineral particles by utilizing the difference of physical and chemical properties of mineral surface, it is called the most widely used mineral processing method. Almost all ore can be sorted by flotation. Such as gold ore, a silver ore, galena, sphalerite, yellow copper ore, chalcocite, molybdenite, nickel sulphide minerals like pyrite, malachite, white lead, calamine, and hemimorphite sorting oxide minerals hematite, cassiterite, wolframite, titanium, iron, beryl, spodumene mineral and rare earth metals, uranium and the like. Graphite, sulfur, diamond, quartz, mica, feldspar and other non-metallic minerals and silicate mineral fluorite, apatite, baryte and other non-metallic minerals potassium salt, rock salt and other minerals soluble salts selected from do not.

Another important use of flotation is to reduce ash in fine coal and to remove fine pyrite from coal. There are billions of tons of ore and materials that are processed by flotation every year in the world. The large ore processing plant processes 100,000 tons of ore per day. The production index and equipment efficiency of flotation are high. The recovery rate of selected sulfide ore is above 90%, and the concentrate grade can be close to the theoretical grade of pure mineral. The use of flotation to treat polymetallic symbiotic minerals, such as copper, lead, zinc and other polymetallic ores can be separated from copper, lead, zinc and pyrite, and can obtain high selection indicators. Flotation is suitable for the treatment of fine-grained and fine-grained materials. It is difficult to recover fine ore particles of less than 10 μm by other beneficiation methods, and it can also be treated by flotation.

Some flotation technologies that specialize in the treatment of very fine particles have a lower particle size lower limit. Ultra-fine flotation and ion flotation technology can recover various substances from colloidal particles to molecular and ionic states. Flotation also selects intermediate products of pyrometallurgy, useful components in volatiles and slag, processes hydrometallurgical leaching slag and displaced precipitated products, and recovers chemical products (such as pulp, surface active substances, etc.) and wastewater. Inorganic and organic matter.

Before 1949, there were only a few flotation plants in China. After 1949, hundreds of modern flotation plants were built to handle various ores. Achievements have been made in the fields of separation flotation of polymetallic ores, comprehensive utilization of complex ores, iron ore flotation, and flotation of non-metallic ores and coal. Flotation Process The theoretical basis of various flotation processes is generally the same, that is, the mineral particles may be in liquid-gas or water-oil due to the hydrophobic nature of their surface or the hydrophobic (affinity or oil) properties obtained by the action of flotation agents. The interface is clustered. Currently the most widely used is the froth flotation method. The ore is broken and ground to dissociate various minerals into monomer particles, and the particle size is in accordance with the flotation process requirements. Various kinds of flotation reagents are added to the milled pulp and stirred and blended to act with mineral particles to expand the difference in floatability between different mineral particles. The adjusted slurry is sent to the flotation tank and stirred for aeration. The ore particles in the slurry contact and collide with the bubbles, and the floatable particles selectively adhere to the bubbles and are carried to rise into a mineralized foam layer composed of gas-liquid-solid three-phase, mechanically scraped or The slurry surface overflows, then dehydrates and dries into a concentrate product. Mineral particles such as gangue that cannot be floated are discharged as tailings products from the bottom of the flotation tank with the slurry. Sometimes, the useless mineral particles float out, and the useful mineral particles remain in the slurry, called reverse flotation, such as floating quartz from iron ore.

Conventional froth flotation is suitable for sorting ore particles of 0.5 mm to 5 μm, depending on the particular mineral. A special flotation method is required when the selected particle size is less than 5 μm. For example, flocculation-flotation is to use flocculant to flocculate the useful minerals of the fine particles into larger particles, and then remove the coarse-grained gangue after the fine mud is removed. The carrier flotation is carried out by using the ore particles having a particle size suitable for flotation as a carrier, so that the fine ore particles adhere to the surface of the carrier and are then floated and sorted. There are also oil agglomeration flotation and emulsification flotation which use oil to agglomerate fine ore particles for flotation; and separation flotation which utilizes high temperature chemical reaction to convert metal minerals in ore into metal and then float. When the metal ions in the aqueous solution are recovered by froth flotation, they are first chemically precipitated or adsorbed by an ion exchange resin, and then the precipitate or resin particles are floated. The materials in the size of molecules, ions and colloids are treated and separated by floating foam. It is characterized by the hydrophobicity of certain materials, slow agitation and a small amount of aeration, so that the floating foam gathers on the surface of the water to scrape. Such as the recovery of oil, protein, pulp and chemical products from the water. Ion flotation is the separation of the reaction product into the floating foam under the action of a surfactant capable of precipitating or complexing with ions. The non-foaming flotation is to separate the flotation material after water-gas, organic liquid-water, water-oil interface (or surface) extraction and aggregation. For example, early film flotation, full oil flotation; developing liquid-liquid extraction flotation. Oil pellet sieving is the formation of selective pellets of hydrophobized useful mineral particles with oil followed by sieving. The bubbles required for flotation are firstly produced by boiling slurry or chemical reaction; currently, mechanical agitation is used to inhale air or introduce compressed air to foam, and decompression or pressurization followed by decompression foaming and electrolytic foaming. There are many factors related to the flotation effect. In addition to the nature of the ore, the flotation agent, flotation machine and flotation process are the most important. Various flotation agents are used to adjust the physicochemical properties of the flotation material and the flotation medium in order to expand the difference of hydrophobic-hydrophilic (ie, buoyancy) between the flotation materials and improve the flotation efficiency. Commonly used flotation reagents are divided into three categories: collectors , foaming agents and conditioners. In the natural world, collectors such as coal, graphite, sulfur, talc and molybdenum are hydrophobic and have natural floatability. The surface of most mineral particles is hydrophilic. In order to improve the floatability, it is necessary to add a collector which makes the mineral particles hydrophobic, that is, a polar collector and a non-polar collector. The polar collector consists of a polar group that interacts with the surface of the mineral particles and a non-polar group that acts as a hydrophobic. When such a collector is adsorbed on the surface of the mineral particles, the molecules or ions are oriented, the polar groups are oriented toward the surface of the mineral particles, and the non-polar groups are formed outward to form a hydrophobic film, so that the ore particles are floatable.

When sorting copper, lead, zinc, iron, nickel and antimony sulfide minerals, various organic thio compounds used as collectors. Representative: 1 alkyl (ethyl, propyl, butyl, pentyl, etc.) sodium dithiocarbonate (or potassium), such as CH ₃ CH ₂ OCSSNa, also known as xanthate, commonly known as xanthate; 2 alkane A thiophosphoric acid or a salt thereof, such as (RO) ₂ PSSH, wherein R is an alkyl group, commonly known as a black drug. Alkyl dithiocarbamate and ester derivatives of xanthate are also commonly used collectors for sulfide minerals. Non-sulfided mineral collectors are mostly various organic oxyacids and salts thereof, such as fatty acids and their soaps (usually oleic acid, tal oil, oxidized paraffin soap) and sodium hydrocarbyl sulfonate. Used for flotation of iron ore, apatite and fluorite. When flotation of tungsten or tin ore, a collector such as toluic acid or styrene phosphate is used. The above agents are all ionic compounds, and the effective part is an anion, which is called an anion collector. Commonly used cationic collectors are fatty amines and etheramines, which are used for flotation of minerals such as zinc oxide ore and silicates. Non-ionic polar collector molecules do not dissociate, such as sulfur-containing esters, non-polar collectors are hydrocarbon oils (also known as neutral oils), such as kerosene, diesel, etc., used in natural floatable minerals Such as the flotation of graphite, molybdenite and coal; shared with the polar collector, can further increase the hydrophobicity of the mineral particles. The foaming agent has a hydrophilic group and a hydrophobic group surface active molecule, and is adsorbed to the water-air interface to reduce the surface tension of the aqueous solution, so that the air filled in the water is easily dispersed into bubbles and a stable foam is produced. The foaming agent and the collector have a combined action to adsorb on the surface of the mineral particles and promote the floating of the mineral. Commonly used foaming agents are pine oil (commonly known as No. 2 oil), cresol acid, mixed fatty alcohol, isomeric hexanol or octanol, ether alcohols and various esters.

The adjuster is divided according to the use: 1 pH adjuster. By adjusting the pH of the slurry, controlling the surface characteristics of the mineral, the chemical composition of the slurry and the action conditions of various chemicals, the flotation effect is improved. Commonly used are lime, sodium carbonate, sodium hydroxide and sulfuric acid. 2 activator. It can enhance the ability of minerals to interact with the collector, so that the non-floating minerals are activated and floated. For example, if the zinc sulphide which is difficult to treat with xanthate is treated with copper sulfate, a copper sulfide coating film is formed on the surface of the mineral, which can be collected and floated; or activated with sodium sulfide to activate lead and copper oxidized ore, and then floated with yellow medicine. . 3 inhibitors. Improve the hydrophilicity of the mineral or prevent the mineral from interacting with the collector, so that its floatability is inhibited. For example, lime is used to inhibit pyrite, zinc sulfate and cyanide are used to inhibit sphalerite, and water glass is used to inhibit silicate gangue. The use of organic substances such as starch and tannin (tannin) as inhibitors can separate a variety of mineral flotation. 4 flocculant. Mineral fine particles are aggregated into larger particles to accelerate the sedimentation rate in water; flocculation-de-sludge and flocculation-flotation can be carried out by selective flocculation. Commonly used flocculants are polyacrylamide and starch. 5 dispersant. It prevents the fine ore particles from accumulating and is in the state of monomer dispersion. The effect is opposite to that of the flocculating agent. Water glass, phosphate and the like are commonly used. The amount of flotation agent varies with the type of agent, the nature of the ore, the flotation conditions and the characteristics of the process. Generally, only a few grams, tens of grams to hundreds of grams per ton of ore, and up to several kilograms. The flotation machine is the main equipment for the flotation process. It consists of a single tank or a multi-tank series. The agitation of the flotation slurry, the adhesion of the bubbles to the ore particles, the rise of the bubbles and the formation of the foam layer being scraped or overflowed are all carried out in the flotation tank.

According to the different methods of stirring and inflation, it can be divided into five types: 1 mechanical stirring type. Stirring and aeration are achieved by a mechanical stirrer. There are centrifugal impellers, star rotors and rod rotors. The agitator rotates at a high speed in the flotation tank to drive the slurry to flow, generating a negative pressure in the impeller chamber to draw in air. 2 inflatable mechanical stirring. In addition to mechanical agitation, low pressure air is charged into the flotation cell. 3 inflatable. Stirring is carried out by injecting air and generating bubbles, such as a flotation column and a foam separation device. 4 gas precipitation type. The dissolved air in the slurry is precipitated by a pressure reduction method or a method of first pressing down to normal pressure to form microbubbles. 5 pressure dissolved gas type. The charged air is pre-dissolved in water by high pressure, and then precipitated in a flotation cell under normal pressure to form a large amount of microbubbles. The flotation process includes roughing, selection, and sweeping operations for grinding, grading, slurrying, and flotation. There is a period of grinding and floating process; stage grinding-flotation stage grinding process; concentrate or medium mine re-grinding process. The operation of flotation to produce coarse concentrate is called rough selection; the refining operation of coarse concentrate is called selection; the tailings re-election operation is called sweeping. When recovering a variety of useful minerals in ore, the process of successive flotation of different minerals is called preferential flotation or flotation; the process of first separating all useful minerals and then separating them is called mixing-separation flotation. Industrial production must be based on the nature of the ore and the requirements of the product, using different prescriptions and flotation processes. Copper ore flotation copper sulfide minerals are commonly used in the treatment of xanthate (collector), pine oil (foaming agent) and lime (adjusting agent), and are floated to separate from gangue and symbiotic iron sulfide minerals. . Most of them use priority flotation. Copper oxide ore is generally activated by sodium sulfide and then added with xanthate flotation, or directly using fatty acid as a collector for flotation. When the lead-zinc ore flotation adopts the preferential flotation process, the zinc blende is inhibited by zinc sulfate and cyanide, and the galena is floated with xanthate; then the copper sulfate is activated and the xanthate floatation is added to the sphalerite. When the mixed flotation process is adopted, the lead and zinc minerals are first floated out together with the xanthate; then the zinc ore is inhibited by the mixed concentrate with zinc sulfate and cyanide, and the lead mineral is floated. Many concentrators now use sulphurous acid and its salts instead of cyanide. Iron ore flotation commonly used oleic acid, tal oil, oxidized paraffin soap or petroleum sulfonate as collector (also foaming agent), flotation of hematite, limonite and other minerals, said iron ore is floating; Or flotation of quartz with a cationic amine collector, or flotation of calcium-activated quartz with an anionic collector, called iron ore reverse flotation. The fine-grained iron ore can be treated by a flocculation-de-sludge-reverse flotation process. Tungsten and tin slime flotation is used for the fine mud containing wolframite or cassiterite, using oleic acid or toluic acid or styrene phosphate as a collector, and water glass is used as a gangue inhibitor for flotation recovery. Lead nitrate or the like is sometimes used as an activator. Fluorite and apatite flotation are commonly used as tarnish or oxidized paraffin soap or tar oil as collectors, and water glass, tannin extract, sulfonated crude phenanthrene and the like are used as gangue inhibitors for flotation.

Coal slime and graphite flotation generally use alcohol as a foaming agent, and a neutral oil such as kerosene is used as a collector flotation. The development trend is due to the lower and lower content of useful components in the ore that needs flotation treatment, the finer particle size, the more complex and difficult to select ingredients, and the expanding flotation field, including the difficulty of other mineral processing methods. Treatment of mud materials, reprocessing of tailings in old ore dressing plants, recycling of various scrap metal materials, treatment and utilization of various waste materials, and purification of sewage. Therefore, we must pay attention to the following four problems: 1 continue to develop new flotation process and large-scale high-efficiency flotation equipment ; 2 study strong force, good selectivity, low dosage, non-toxic or less toxic flotation agent; 3 research Flotation mathematical model and automatic control of the process to optimize the process to achieve the best sorting effect to improve economic efficiency; 4 further from mineral technology, chemistry, physics, surface chemistry, fluid dynamics, probability statistics In the other aspects, the flotation mechanism is studied in depth to guide the flotation production practice and further develop the flotation theory system.

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