Proper preparation of flotation reagents before use is crucial for improving their efficacy. The preparation method depends mainly on the properties of the reagent, and common methods include:
(1) Preparing an aqueous solution. This method is used for most water-soluble reagents, generally preparing a 5%–10% or even more diluted aqueous solution before addition. The solution should not be too dilute, as this results in an excessively large volume; however, it should also not be too concentrated, as excessive concentration makes it difficult to accurately control the dosage of small amounts of reagent and also hinders transportation.
(2) Preparing with a solvent. Some reagents that are insoluble or poorly soluble in water can be dissolved in a special solvent before addition. For example, dissolving oleic acid in kerosene before addition can enhance its dispersibility in the slurry and strengthen its collecting effect; bleach can be dissolved in o-toluidine before use.
(3) Emulsification. Emulsifying fatty acid collectors and diesel fuel can increase their dispersibility in the slurry and improve their efficacy. Common emulsification methods include vigorous mechanical stirring, steam introduction, or ultrasonic treatment. Adding an emulsifier can improve the effect. For example, alkyl aryl sulfonates can be added as an emulsifier to tall oil and diesel oil in water. Many surfactants can also be used as emulsifiers.
(4) Saponification. Fatty acid collectors are often prepared using this method. For example, in iron ore flotation, oxidized paraffin soap and tall oil are often used as collectors. To improve its water solubility, about 10% sodium carbonate can be added to saponify the tall oil, and then hot water is used to prepare a hot soap solution for addition. Oleic acid, for instance, has poor water solubility, but its water solubility improves after reacting with sodium carbonate to form sodium oleate.
(5) Forming suspensions or emulsions. For example, lime can be ground with water to form lime milk for addition.
(6) Acidification. When using cationic collectors (amines), due to their poor water solubility, hydrochloric acid or acetic acid must be added to prepare an amine salt before it can be dissolved in water for use.
(7) Addition of the stock solution. Some agents have very low solubility in water and are difficult to prepare into true solutions or stable emulsions, such as pine oil, cresol black powder, and kerosene. In these cases, it is not necessary to prepare a solution; the stock solution can be added directly according to the dosage.
The preparation method for water-soluble agents is generally to first dissolve the agent in a small amount of water in a container. After complete dissolution, water is gradually added to achieve the required concentration.
At the production site, for ease of preparation, a scale indicating the volume can be engraved on the mixing tank. The weighed, known amount of agent is placed in the tank, and water is added to the mark corresponding to the concentration. Stirring until completely dissolved, it is then ready for use.
Whether the agent concentration meets the standard can be determined using a hydrometer.