In the beneficiation process, the mineral enrichment process from the grinding and grading overflow slurry is called flotation by utilizing the difference in the natural hydrophobicity of the mineral. In the flotation operation, in order to effectively separate the various minerals of the ground ore, it must be treated with a chemical agent, and stirred and aerated in the slurry, and the mineral which is easy to adhere to the bubble floats with the bubble and does not adhere to the bubble. The mineral remains in the pulp for the purpose of mineral enrichment. The various agents used in the flotation process, collectively referred to as flotation reagents, are referred to as regulators in addition to the collector and foaming agent in the flotation reagent. The role of the modifier is to adjust the action of the collector and the mineral, to promote or inhibit the floatability of the mineral, to adjust the pH of the slurry and the composition of the ions. According to the action effect of the adjusting agent, it can be roughly divided into a pH adjusting agent, an activator, an inhibitor, a dispersing agent, a flocculating agent and the like.

First, the pH adjuster

(1) pH adjusting agents include: lime, sodium carbonate, sulfuric acid, sulfur dioxide, caustic soda, and the like.

1. Lime: Limestone (CaCO3) is calcined and decomposed into quicklime (CaO) and carbon dioxide at a high temperature of 1200 °C. The quicklime is referred to as lime, and the quicklime is easily absorbed into slaked lime (Ca(OH)2). The slaked lime is a white powdery substance, which is not easily dissolved in water. It is usually added directly to the ball mill or the agitation tank before flotation in the flotation operation. It can also be adjusted into lime milk with water during stirring, and then added to the flotation machine. Calcium oxide is a strong base, and the calcium hydroxide dissolved in water is completely ionized, making the solution strongly alkaline.

Lime is the cheapest slurry pH adjusting agent, in a multi-metal sulphide deposits, the use of flotation, the pH of the pulp used to improve the lime, so that pyrite is suppressed. Lime is a typical inhibitor of pyrite. Generally, some pyrite can be floated in weakly acidic pulp, and some can also be floated in neutral or alkaline pulp. After the surface of the pyrite is oxidized, it will not float well when the pH is greater than 7. The addition of lime pyrite is inhibited.

The reason why lime inhibits pyrite is the formation of a hydrophilic film of Fe(OH)2 and Fe(OH)3 on the surface of the mineral.

Pyrite lime is suppressed, can be neutralized with sodium carbonate and copper sulphate, or sulfuric acid was added to the slurry was adjusted to a pH of 6-7, the flotation of pyrite can again.

2, sodium carbonate: soda's scientific name is sodium carbonate, industrially called soda ash, is a weak acid and strong alkali salt, colorless solid, soluble in water. Electrolysis is carried out in aqueous solution to sodium ions and carbonates.

Na2CO3=2Na++CO32-

Carbonate re-hydrolysis to make the solution alkaline

The aqueous sodium carbonate solution is weakly alkaline and has a pH between 8 and 10. When using flotation selected from zinc, lead sulfide ore selected from galena inhibition sphalerite, pyrite, the slurry pH was adjusted to between 8-10. The use of sodium carbonate instead of lime not only maintains the pH stability of the slurry, but also prevents the inhibition of lead minerals by Ca2+.

3, sulfuric acid

The sulfuric acid used in the industry is brown, and the common concentrated sulfuric acid contains H2SO496% to 98% and dilute sulfuric acid 63% to 65%.

Sulfuric acid is the most commonly used acid regulator in flotation operations, and concentrated sulfuric acid can be miscible with water. Sulfuric acid is a strong acid that ionizes a large amount of hydrogen ions in an aqueous solution.

H2SO4=2H++SO42-

When diluting and using, pay special attention to slowly inject sulfuric acid into the water, avoiding a large amount of heat to boil the added water, causing the sulfuric acid splash to cause a burn accident.

Second, the activator

The act of increasing the floatability of the mineral during the flotation process is called activation. The agent used to change the surface composition of the mineral and promote the action of the collector and the mineral surface is called an activator.

Activation can be roughly divided into: 1, spontaneous activation; 2, pre-activation; 3, reactivation; 4, vulcanization.

(1) Spontaneous activation: When dealing with colored polymetallic ores, the spontaneous action of the mineral surface and some soluble salt ions during the grinding process, such as the sphalerite and copper sulfide minerals, when oxidized after the ore is mined The effect is that a small amount of copper sulfide mineral is oxidized to copper sulfate. The Cu2+ ion and the zinc blende surface act to activate it in the slurry, which makes it difficult to separate copper and zinc. It is necessary to add lime or sodium carbonate to adjust the precipitate. Activated "inevitable ions".

(2) Pre-activation means that in order to select a certain mineral, an activator is added to activate it. When the pyrite is heavier in oxidation, the oxide film on the surface of the pyrite is dissolved by sulfuric acid before the pyrite is selected to expose the fresh surface to facilitate flotation.

(3) Revitalization refers to a mineral that has been previously suppressed, such as sphalerite suppressed by cyanide, which can be revived by adding copper sulfate.

(4) Vulcanization means that the metal oxide ore is first treated with sodium sulfide to form a metal sulfide mineral film on the surface of the oxidized ore, and then floated with xanthate.

The ore dressing agents used as activators are:

Sulfuric acid, sulfurous acid, sodium sulfide, copper sulfate, oxalic acid, lime, sulfur dioxide, lead nitrate, sodium carbonate, sodium hydroxide, lead salt, barium salt, and the like.

Third, the inhibitor

Common inhibitors are: sodium sulfide, zinc sulfate, sodium cyanide, potassium chromium weight, water glass, lime, ferrocyanide, tannin, starch (dextrin), carboxymethyl cellulose and the like.

(a) sodium sulfide

Sodium sulfide is an activator of non-ferrous metal oxide ore and is an inhibitor of sulfide ore when added in a sufficient amount.

The preparation of sodium sulfide is the reduction of sodium sulfate (Na2SO4) by combustion of coal , wood carbon or the like as a reducing gas.

The reaction formula is: Na2SO4+2C=Na2S+2CO2↑

Sodium sulfide is used as an inhibitor of sulfide ore in flotation operations. In the production practice of molybdenum , sodium sulfide is used to inhibit pyrite, and kerosene is used as a collector to float molybdenum ore. The floatability is not inhibited by sodium sulfide, and the sodium sulfide inhibits the pyrite. After several selections, qualified molybdenum concentrate is obtained.

When sodium sulfide is added to the slurry, the slurry is alkaline, and a hydrophilic film of hydrophilic hydroxide is formed on the surface of the sulfide mineral to be hydrophilic, so that the sulfide mineral is inhibited.

(2) Zinc sulfate

The preparation of zinc sulfate is carried out by using zinc flakes from a metal processing plant and dilute sulfuric acid. Zinc sulphate is an inhibitor of sphalerite. The effect of using it alone is not very obvious. When it is used together with alkali, sodium cyanide or sodium sulfite, the inhibitory effect is strong. The higher the pH value of the pulp, the better the inhibition effect.

(3) Sodium cyanide (potassium)

When the polymetallic deposit adopts the preferential flotation process, sodium cyanide is used to suppress sulfide minerals such as pyrite, sphalerite, chalcopyrite, etc. The combination of sodium cyanide and zinc sulfate has a good inhibitory effect on sphalerite. When the amount of sodium cyanide is small, the pyrite can be inhibited. When the amount is slightly increased, the sphalerite can be inhibited, and when the amount is increased, various copper sulfide minerals can be inhibited.

In the production practice, since sodium cyanide is toxic, it is often replaced by sulfur dioxide or sodium sulfite. Sulfur dioxide and sodium sulfite have a weaker inhibitory effect than sodium cyanide. However, since the toxicity is small and it is easily oxidized by air, the wastewater is easily treated and often used. Another advantage is that minerals inhibited by sulfur dioxide and sodium sulfite are more susceptible to activation by copper sulfate, while minerals inhibited by sodium cyanide are more difficult to activate.

(four) lime

Lime inhibition of pyrite: Lime inhibition of pyrite is due to the formation of hydrate films of calcium sulfate, calcium carbonate and calcium oxide on its surface.

To activate pyrite-reduced pyrite, sodium carbonate and copper sulfate may be used, or sulfuric acid may be added to lower the pH of the slurry to 6-7, and butyl xanthate is floated to remove pyrite.

(5) Phospho Knox

Phonon Knox is prepared by using phosphorus pentasulfide and sodium hydroxide as raw materials. Sodium hydroxide was formulated into a 10% aqueous solution, followed by the addition of phosphorus pentasulfide. After stirring for 20 minutes, the prepared solution was diluted to 0.5% to 1%, and it was put into use. The ratio of sodium hydroxide to phosphorus pentasulfide is 1:1.

(6) Water glass

Water glass is an inorganic colloid that is the most commonly used inhibitor in flotation operations. Waterglass have a good inhibition of silica, silicate minerals and aluminosilicate minerals (e.g., mica, feldspar, garnet, etc.), as inhibitors of gangue heavy use.

The water glass is a water glass agglomerate which is melted by quartz sand and sodium carbonate, and the sintered block is dissolved in water to form a paste colloid. Its composition is complex, containing sodium metasilicate Na2SiO3, sodium orthosilicate Na2SiO4, sodium disilicate sodium Na2SiO5 and SiO2 rubber particles. It is usually expressed by Na2SiO3.

Boiled water glass quartz and sodium carbonate, the water glass properties are different due to the different proportions of the application materials. The ratio of Na2O to SiO2 is usually used to represent the composition of water glass. The ratio of mNa2O·nSiO2 is n/m. The modulus, floating water glass, mold n / m = 2.0 ~ 3.0, the common water glass quality standard modulus is 2.2. Water with a small modulus is strong in alkalinity, and it is difficult to dissolve and has a strong inhibitory effect.

The inhibition of water glass is mainly HSiO3- and H2SiO3, the silicic acid molecule H2SiO3 and the silicate acid HSiO3- have strong hydration, and are a kind of hydrophilic particles and ions, HSiO3- and H2SiO3. Silicate minerals have the same acid radicals and are easily adsorbed on the surface of quartz and silicate minerals to form a hydrophilic film, which increases the hydrophilicity of the mineral surface and inhibits it.

(7) Sodium thioglycolate

Sodium thioglycolate is used for the selective operation of molybdenum. When the copper content of molybdenum concentrate is relatively high, sodium thioglycolate is added to inhibit copper. The copper content of the molybdenum concentrate can be reduced from 0.5% to less than 0.17%.

(eight) oxalic acid

The molecular formula of oxalic acid is (COOH)2

It is a saturated dibasic acid called oxalic acid and is an organic inhibitor. Oxalic acid is a potent inhibitor of barite and garnet. Oxalic acid is commonly used in fluorite flotation to inhibit gangue minerals to ensure that the grade containing CaF2 is 95% fluorite concentrate.

(9) Carboxymethyl cellulose

Carboxymethyl cellulose, industrial products are light yellow flocculents, chemically stable, soluble in water.

Carboxymethylcellulose are potent inhibitors of the magnesium-containing silicate minerals pyroxene, serpentine, amphibole, Ling-high soil chlorite. It also inhibits quartz, carbonaceous gangue, muddy gangue (silicate mineral weathering products). Nickel ore floatation uses carboxymethyl cellulose to inhibit pyroxene and hornblende, which is better than water glass.

Fourth, flocculant, dispersant

(1) Flocculant

The flocculant is widely used in the flotation process. For example, in order to prevent the loss of concentrate, the sedimentation of concentrate fine particles is accelerated in the concentrate thickener, and flocculant is added when necessary to reduce the loss of concentrate in the overflow of the thickener, and some concentrates are difficult to filter. The addition of flocculant can increase the filtration speed, reduce the moisture in the filter cake, and more importantly, the purification of tailings water, prevent the tailing water from polluting the surrounding environment, and also create conditions for the recycling of tailing water.

Flocculants which have been put into use include polyacrylamide, polyoxyethylene and the like. The most widely used is polyacrylamide called coagulant No. 3.

No. 3 coagulant is a synthetic polymer compound. The production steps are divided into hydrolysis, neutralization, filtration, ion exchange, polymerization and other processes. The shaping process for preparing polyacrylamide is sulfuric acid hydration, aqueous monomer solution polymerization, and the content of finished polyacrylamide is 7% to 8%.

Concentrated filtration of scheelite using polyacrylamide agents can reduce concentrate loss in the overflow. The ore contains 0.3% to 0.6% of WO3, the solid content in the overflow is 50-60g/L, and the WO3 contains 0.6%-0.8%.

The polyacrylamide agent can also greatly accelerate the sedimentation rate of iron hydroxide, gypsum , scheelite and barite.

In short, polyacrylamides are widely used and have good effects. They can be used as inhibitors of gangues , selective collectors for clays , and good flocculants.

(2) Dispersing agent

The most commonly used dispersant in flotation operations is water glass. Water glass has a dispersing effect on the slime, which has a significant effect on improving the concentrate grade of valuable metals. The same agent often has different effects under different flotation conditions. The dispersing effect of water glass on the slime is a dispersing agent. The inhibitory effect on quartz is an inhibitor, and the pH value of the pulp can also be adjusted. Therefore, the classification of pharmaceuticals has its flexibility. As far as water glass is concerned, it can be used as both a dispersant and an inhibitor.

pH regulators, inhibitors, activators, flocculants, and dispersants are generally referred to as modifiers. In general, flotation reagents can be divided into three categories: collectors, foaming agents and conditioners.

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