Foaming agent

Blowing agent means to reduce the surface tension of water to form a foam, mineral inflatable floating air bubbles in the slurry can be attached to a class of surfactants on selective floating mineral particles. In contrast, an antifoaming agent refers to an agent capable of breaking or preventing the formation of foam.
In the flotation process, the addition of the foaming agent can prevent the merger of the bubbles; it is also possible to appropriately extend the existence time of the bubbles on the surface of the slurry.
Generally, the foaming agent has the following common properties: (1) The molecular structure of the foaming agent is often an isopolar organic substance, one end is a polar group, the other end is a non-polar group; the polar group is hydrophilic, non-polar Sex-based affinity, so that the foamer molecules can be oriented at the interface between air and water. (2) The foaming agent is a surface active substance capable of lowering the surface tension of water. The term "surface activity" as used herein refers to a decrease in the surface tension due to an increase in the concentration of the unit foaming agent in the solution. Generally speaking, the surface activity of the same series of organic surfactants is increased by the "third law" (also called "Trubey law"), and the solubility is reduced by the same law. In the case of alcohols, for example, from ethanol, the surface activity of any alcohol is three times that of its nearest lower alcohol and one third of its nearest higher alcohol. The solubility is gradually reduced by the same law. (3) The general foaming agent requires a medium solubility of 0.2 to 5 g/l. As described above, the surface activity in the homologue increases as the molecular weight increases, but at the same time the solubility decreases as the molecular weight increases. The practice of flotation proves that due to the effects of these two factors, the common foaming agent is generally suitable for the number of carbon atoms in the molecule of 5 to 11.
There are many organic compounds having foaming properties, and alcohols, phenols, ketones, aldehydes, ethers and esters are commonly used in flotation processes. Good foaming agents should not be trapping at the same time. Although organic acids and amines also have foaming properties, their collectability is more prominent and is generally considered as a collector . There is also a large class of plant saponin substances in organic compounds which have strong foaming properties and are not used as a foaming agent in the flotation process due to their outstanding organic colloidal properties.
From the perspective of historical development, in the flotation process, the attention of the foaming agent is far less than that of the collector. In the early days, countries often used local conditions to obtain materials on the spot. For example, pine oil is used in China, eucalyptus oil is used in Australia, and camphor oil is used in Japan. The common features are all natural plant products of cockroaches. The disadvantage is that the ingredients vary with different manufacturing methods and seasons. In recent years, after the rapid development of the basic organic synthesis industry, synthetic foaming agents have been the trend to replace natural foaming agents, characterized by stable quality and high content of active ingredients, such as isobutylmethylbenzyl alcohol (MIBC). After the 1970s, a new type of foaming agent containing elements such as nitrogen, sulfur, phosphorus and silicon in the molecule appeared, and it is still in the experimental stage.
There are four basic methods for determining the foaming performance of an aqueous foaming agent solution:
(1) The foaming agent ice solution was stirred by hand or mechanically for several minutes, and then the volume of the foam layer was measured.
(2) Stirring in a foaming agent aqueous solution using a rotating agitator or a porous disk moving up and down, and then measuring the volume of the foam.
(3) In a glass tube with a sand core fine hole bottom plate, small bubbles of air or other gas are bubbled into the aqueous solution to be tested, and then the foam height is measured.
(4) The aqueous foaming agent solution was dropped from a certain height, and then the generated foam was measured.
The above four basic methods are all measuring the height of the foam generated within a certain period of time, or measuring the weight of the liquid contained in the foam layer. A common feature of these methods is the measurement of the volume of the foam in a two-phase system in the absence of solid particles, and is generally only suitable for testing surfactants. It is worth considering whether the advantages and disadvantages of different foaming agents are consistent with the conclusions obtained from flotation practice by the above method. In 1972, some people used the flotation method to compare with the above methods, which proved that the order of the pros and cons of the foaming agent measured by the above method is different from the order of the pros and cons measured by the direct flotation method. Only the bubble method is closest to the flotation method.
The quality of the foaming agent is determined by the foaming ability, the stability of the foam, and the speed at which the formed foam disappears. In addition, the size of the foam, the specific surface area of ​​the foam (measured by the transmission of a microscope or light), and the viscosity, elasticity, and tensile strength of the foam are also important, but are generally seldom measured.
1. Pine oil and pine oil (No. 2 oil)
Natural foaming agents, including pine oil, camphor oil, eucalyptus oil, and pine needle oil, are mainly composed of terpenoids. Among them, pine oil is still the most widely used foaming agent in the current floating mineral processing. Due to the different sources, pine oil is divided into two categories: “natural pine oil” and “synthetic pine oil”. The "natural pine oil" obtained by extracting or fractionating pine is directly changed in composition, and the content of terpineol is small. The chemical treatment of terpene in turpentine or turpentine is called "synthetic pine oil". The main components of natural pine oil and synthetic pine oil are terpene alcohols. In China, synthetic pine oil, which is directly processed with excellent grade turpentine by chemical processing, is pine oil (commonly known as No. 2 oil), and is the most important foaming agent used in China. The annual dosage is about several thousand tons, accounting for more than 95% of the total amount of foaming agent. The raw material for the production of pine oil is shown in Figure 1 [next]

Figure 1 Schematic diagram of the source of large-scale pine oil production raw materials

Since the founding of New China, Chinese scientists have conducted extensive explorations of forest resources. For example: carbonized pine root made with pine root oil having a boiling point above 160 ℃ directly as selected from the group of copper, a foaming agent selected from coal; papermaking obtained with turpentine (fraction boiling above 170 ℃, common name flotation yellow oil) PREPARATION; with Feisong pine needle oil is used as a foaming agent; it has achieved certain success by flotation of sulfide ore with the residue of oyster oil after refining the dragon's brain.
The purpose of developing pine oil (No. 2 oil) in China is to fill the gap in the production of pine oil. Its flotation effect exceeds that of natural pine oil, which is widely used in many mines. China's mineral processing pharmacy to produce pine oil oil raw materials, a superior grade turpentine oil is supplied by the provincial rosin factory.
Ministry of metallurgical industry of number YB501-65 standard, pine oil (II oil) in accordance with the content of terpene alcohols divided into the following two levels (Table 1).

In the past 20 years, the technical level of China's mineral processing pharmacy production plant has been improved. The above-mentioned 1965 ministerial standards require that the content of terpene alcohol is already low. In order to improve the mineral processing index, the concentrating plant will reduce the pollution of the tailing water to the environment. The content of terpene alcohol in the alcohol oil (No. 2 oil). At present, some domestic ore dressing pharmacies have successfully produced "concentrated 70" and "concentrated 80" pine oil oil foaming agents with high concentration of terpene alcohol (called No. 1 oil in the 1950s).
In addition, around 1982, Zhuzhou Mineral Processing Pharmacy also launched low-priced "new pine oil" products on the market. Silver White Company trial "oil dipentene" as an auxiliary blowing agent or foaming agent to obtain results.
Second, alcohol foaming agent Alcohol compounds are far less active in minerals than carboxylic acids, generally not trapping and only foaming. As for the homologues of linear alcohols, as the number of carbon atoms in the molecule increases, the solubility in water gradually decreases, and the foaming capacity increases, to pentanol, hexanol, heptanol, and octanol. Great point.
An acidic phenolic compound similar to an alcohol, "cresol oil (also known as cresol)" and a flotation foaming agent containing phenols, including wood coke oil and coal pyrocarbon oil, have been used as Foaming agents have played a large role in the flotation process. In recent years, due to the high toxicity of such agents, the pollution of river water is serious, and the amount of use has been gradually reduced or prohibited. If there is a trace amount of phenolic substances in drinking water, when the tap water is sterilized by chlorine gas, the odor of polychlorinated phenol will be produced and the water quality will be deteriorated.
The use of alcohols as foaming agents is widely used due to the rise of the modern organic chemical industry. The Beijing Research Institute of Nonferrous Metals used the distillation residue "molecular oil" of the alcohol factory to make "high-grade mixed alcohol" by alkaline catalytic condensation: [next]

The ore dressing test proves that it can be used as a substitute for pine oil for sulfide ore flotation. Liaoning Province, Institute of Metallurgy has used calcium carbide plant byproduct C ₄ ~ C ₈ alcohol is mixed feedstock is fractionated to C ₆ ~ C ₈ alcohol mix, a copper sulfide flotation, sphalerite and molybdenite. In 1972, the Kailuan Coal Research Institute directly used the by-products of the above-mentioned calcium carbide plant for coal preparation.
A by-product of 4,4-dimethyl-1,3-di-n-methane produced from isobutylene and formaldehyde. It is a kind of soluble mixed alcohol. The trade name of the Soviet Union is "T-66", which has been widely used in non-ferrous metal ore flotation. As a substitute for pine oil.
Among the alcohol foaming agents, the most prominent one is methylpentanol (also known as isobutylmethylbenzyl alcohol, MI-BC for short). The pure product is a colorless liquid with a refractive index of 1.409 and a density of δ ²⁰ ₄ 0.813 g. / cm ^3, a boiling point of 131.5 deg.] C, may be dissolved per 100 ml of water, 1.8 g of industrial mass production has, accounted for half of the total amount of blowing agent in the international market. MIBC is used as a solvent in early small-scale production in China, but as a foaming agent, the price is high.

In 1982, the Beijing Research Institute of Mining and Metallurgy and the Dalian Institute of Chemical Physics collaborated to produce a mixed hexahydric alcohol with the trade name P-MPA using propylene as a raw material, which was used in a variety of non-ferrous metal mining industry flotation. Good results have been achieved and industrial trial production is currently underway. The Changsha Research Institute of Mining and Metallurgy has also successfully produced another hexahydrin foaming agent, “Dihydroxy MI-BK, which has been used in batches for industrial beneficiation. Its composition is

Third, ether alcohol foaming agent
This type of foaming agent was first developed by American Dow Chemical Company and Cyanamide Company. They are characterized by being fully soluble in water. Initially they were used as a by-product of the production of brake fluid and then turned into a foaming agent. Such foaming agent Dow Chemical Company's trade name is "Dowfroths"; cyanamide company's trade name is "Aerofroths"; British Imperial Chemical Company's trade name is "Teefroths"; Soviet trade name is "OP C class"; China's goods It is called "ether alcohol oil". The production of ether foams and MIBC foaming agents on the international market accounts for about 90% of the total amount of metal ore flotation foaming agents.
Foaming agents of this type include diethylene glycol methyl ether (I), diethylene glycol butyl ether (II), tripropylene glycol methyl ether (III), and tripolypropylene glycol butyl ether (IV).

In China, the Beijing Research Institute of Nonferrous Metals and the Guangdong Nonferrous Metals Research Institute have conducted extensive research for a long time and have been mass-produced.
Junji as colorless liquid polyethylene glycol methyl ether, molecular weight of 120.09, density δ ²⁰ ₄ 1.0354 g / cm ^3, a boiling point of 193.2 deg.] C, to be mixed with water in any ratio, soluble in alcohol, insoluble in ether. Diethylene glycol butyl ether is also a colorless liquid with a molecular weight of 162.14, a density of δ ²⁰ ₄ 0.9553, a boiling point of 231.2 ° C, and is easily soluble in water.
Such foaming agents can be used in various types of sulfide ore flotation, characterized by a small amount, a minimum dosage of 3.5 g/ton, a maximum dosage of 75 g/ton, and an average dosage of 25 g/ton. [next]
Hunan Zhuzhou Mineral Processing Pharmacy Factory produces a kind of foaming agent called “glycine oil”, which is also a kind of ether alcohol foaming agent. It is a mixture. The main component is polyethylene glycol benzyl ether. The appearance is brownish yellow oil. The liquid is characterized by being slightly soluble in water, easily soluble in organic solvents, and used for flotation of sulfide ore. The dosage is smaller than that of pine oil, the foaming performance is strong, the flotation speed is fast, and the price is lower than that of pine oil.
4. Ether-based foaming agent The most prominent among the ether foaming agents is triethoxybutane, which has a structural formula of 1,1,3-triethoxybutane, and the abbreviation "TEB". In 1964, the Beijing Research Institute of Mining and Metallurgy was successfully trial-produced, and then the silver dressing pharmacy plant was put into production. The trade name was “butyl ether oil” and the common name was “4 ^#油”.
The pure product is a colorless transparent liquid with a density of δ ²⁰ ₄ 0.875, a refractive index of δ ²⁰ ₄ 1.4080, a boiling point of 87 ° C, industrial products contain impurities, color brownish yellow, solubility in water at 20 ° C is 0.8%, in weakly acidic medium It can be hydrolyzed to hydroxybutyraldehyde and ethanol:

Triethoxybutane is one of the least toxic in known foaming agents, has a strong foaming power, a large amount of foam, and is suitable for a wide pH. The disadvantage is that the flotation speed is too fast and sometimes difficult to control.
5. Ester Frothing Agents A number of fatty acids or aromatic acids can be useful as flotation foaming agents after simple esterification. The most prominent ones are diethyl phthalate and mixed low-carbon fatty acid ethyl esters.
The former Soviet Union used diethyl phthalate as a foaming agent, and its trade name was II-3 foaming agent. Kunming Metallurgical Research Institute successfully developed and put into production the same product, the trade name is "phenyl ethyl ester oil".
Phenyl ethyl ester oil is non-toxic and odorless, and has strong foaming power. For flotation of lead zinc, lead concentrate recoveries in the range 79 to 83% zinc concentrate recovery rate of 71 to 73%. Try it in the copper mine of Zhongtiaoshan Nonferrous Metals Co., Ltd. When the dosage is half of the pine oil and the yellow amount is reduced by 20%, it can obtain the technical index similar to the pine alcohol oil and superior to the ether alcohol foaming agent.
Foaming agents No. 56 and No. 59 produced by Shenyang Metallurgical Mineral Processing Pharmacy are esterified with different fractions of low-carbon fatty acids and ethanol. The former is a C ₅ -C ₆ mixed acid, and the latter is a C ₅ -C ₉ mixed acid. These acids are derived from the blend of low carbon fatty acid by-products of oxidized paraffin soap. It is suitable for flotation separation of lead-zinc ore, good foaming and easy to operate. The above two foaming agents have a pale yellow transparent liquid and are flammable.
6. Foaming agents containing sulfur, nitrogen, phosphorus and silicon. The foaming agents commonly used in the past are all compounds containing carbon, hydrogen and oxygen, and do not contain other heteroatoms. Only heavy pyridine contains nitrogen atoms and has a foul smell, which has been gradually eliminated. . Currently, it is only used by Zhongtiaoshan Nonferrous Metals Co., Ltd. in China.
In recent years, a new trend in the development of foaming agents in the world has been the study of synthetic foaming agents containing heteroatoms, including sulfur, nitrogen, phosphorus, and silicon. At the same time, the introduction of high molecular compounds as foaming agents has achieved varying degrees. The striking good results have opened up new varieties and new types of foaming agents. The summary is shown in Table 2.

Seven, defoamer
Foam flotation is characterized by the use of mineralized foam to separate the valuable minerals from the gangue. However, during the flotation process, too much foam often occurs in the trough; the concentrate that has emerged flows into the thickener, and the foam Too much will cause the obtained concentrate to be lost with the overflow of the foam layer. For this reason, an antifoaming agent is added when necessary to properly control the amount of foam. In the chemical industry, defoamers are used in a wider range of applications, and the industry has provided a wide variety of defoamers with different compositions. The effectiveness of defoamers is often targeted, and foams of different characteristics must be used with certain types of agents to be effective. Most defoamers are insoluble in water and are mostly used in the form of emulsifiers. Commonly used antifoaming agent has (its chemical name row): activated carbon, hydrophobic silica powder, aluminum silicate powder, sodium silicate, sodium tripolyphosphate, sodium hexametaphosphate, organic silicone, dimethyl silicone Alkane polymers, vegetable oils, animal oils, castor oil, 2-ethylhexanol, diisobutyl methanol, pine oil, fatty acids, fatty acid metal soaps, fatty acid esters (eg Spans, Span), alkyl lactate, Sulfonated tart oil, sulfonated oil, polyamide, polyether, polyalkoxy polymer, polypropylene oxide polyamine, carboxylic acid-N-alkylamide, polybutene defoamer, high Polyethylene glycol of molecular weight.

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