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Solid reagents are diluted into liquids for easy addition. Reagents with poor water solubility such as yellow medicine, amine black medicine, water glass, sodium carbonate, copper sulfate, sodium sulfide, etc. are all prepared into aqueous solutions for addition, with preparation concentrations ranging from 2% to 10%. The water-insoluble agents should be dissolved in solvents first, and then prepared into aqueous solutions for addition, such as amine collectors. Some can be added directly, such as 2# oil, 31# black medicine, oleic acid, etc. For agents that are easily soluble in water and have a large amount of use, the concentration is generally 10-20%, such as sodium sulfide, which is prepared at 15% when used. For agents that are difficult to dissolve in water, they can be dissolved with the help of organic solvents, and then prepared into low-concentration solutions.
The choice of agent preparation method is mainly based on the properties, addition method and function of the agent. The same reagent has different dosage and effect due to different preparation methods. The general preparation methods are:
① Prepare into 2% to 10% aqueous solution. Most water-soluble reagents are prepared in this way (such as yellow medicine, copper sulfate, water glass, etc.)
② Prepare with solvent. Some water-insoluble reagents can be dissolved in special solvents. For example, white medicine is insoluble in water, but it can be dissolved in 10% to 20% aniline solution. It can only be used after preparing aniline mixed solution; for example, aniline black medicine is insoluble in water, but it can be dissolved in alkaline solution of sodium hydroxide. Therefore, when using aniline black medicine, you must first prepare alkaline solution of sodium hydroxide, and then add the reagent to prepare aniline black medicine solution and add it to the flotation machine.
③ Prepare into suspension or emulsion. For some solid reagents that are not easily soluble, they can be prepared into emulsion for use. If the solubility of lime in water is very small, the lime can be ground into powder and mixed with water to form an emulsion suspension (such as lime milk), or it can be directly added to the ball mill and mixing barrel in dry powder form.
④ Saponification. For fatty acid collectors, saponification is the most common method. For example, when selecting hematite, oxidized paraffin soap and tar oil are used together as collectors. In order to saponify tar oil, about 10% of sodium carbonate is added when preparing the agent, and it is heated to make hot soap solution for addition.
⑤ Emulsification. The emulsification method is ultrasonic emulsification or mechanical strong stirring. For example, after fatty acids and diesel are emulsified, their dispersion in the slurry can be increased, and the effect of the agent can be improved. Adding some emulsifiers will have a better effect. Many surfactants can be used as emulsifiers.
⑥ Acidification. When using cationic collectors, due to their poor solubility, they must be pre-treated with hydrochloric acid or acetic acid before they can be dissolved in water for flotation.
⑦ Aerosol method is a new preparation method to enhance the effect of reagents. Its essence is to use a special spray device to atomize the reagents in the air medium and then add them directly to the flotation tank, so it is also called "aerosol flotation method". This method not only improves the floatability of useful minerals, but also significantly reduces the dosage of reagents. For example, the collector is only 1/3 to 1/4 of the usual dosage, and the frother is only 1/5.
⑧ Electrochemical treatment of reagents. In the solution, direct current is used to chemically treat the flotation reagents, which can change the state of the reagents themselves, the pH value of the solution and the redox potential value, so as to achieve the purpose of increasing the concentration of the most activating reagent components, increasing the critical concentration of colloid formation, and increasing the dispersion of insoluble reagents in water.
Usually, the collector and frother are stirred for 1-2 minutes, while some reagents need to be stirred for a long time, such as potassium dichromate to inhibit lead in copper-lead separation.
In order to give full play to the effect of flotation reagents, the general practice of adding location is: adjusters, inhibitors and part of collectors (such as kerosene) are added to the ball mill to create a suitable flotation environment as soon as possible. Collectors and frothers are mostly added to the first mixing barrel of flotation. If there are two mixing barrels for flotation operation, the activator should be added to the first mixing barrel, and the collector and frother should be added to the second mixing barrel. . Depending on the role of the reagents in the flotation machine, the adding location is also different. For example, copper sulfate, xanthate, and pine oil are three reagents. The general order of adding is copper sulfate added to the center of the first mixing tank, xanthate added to the center of the second mixing tank, and pine oil added to the outlet of the second mixing tank. In general, the flotation plant first adds pH adjusters to adjust the pulp to a suitable pH value to better play the role of collectors and inhibitors. When adding reagents, pay attention to the problem that some harmful ions cause reagent failure. For example, the reaction between copper ions and hydride ions will make the hydride ineffective. When separating copper and sulfur, if there are more copper ions in the stirring tank, do not add cyanide to the stirring tank, but add it directly in the separation flotation operation.
In order to improve the efficiency of the reagent and save the amount of reagent, in recent years, many experimental research works have been carried out at home and abroad on the application of physical methods to enhance the efficiency of reagents. Among them are emulsification, heated flotation, aerosol method, electric field and magnetic field treatment, ultraviolet irradiation, and high-energy radiation to enhance the flotation process and the role of reagents.
