Flotation reagents are chemical reagents used in mineral flotation processes that modify mineral surface properties,increase or decrease mineral floatability, and make ore pulp properties and foam stability more favorable for mineral separation. The flotation reagent first used as mineral dressing agent, with maximum variety and obvious performance.
There are as many as 8,000 kinds of flotation reagents in application, among which 100 kinds are commonly used. Flotation reagents are generally classified into flotation collectors, foaming agents, activators,inhibitors, and conditioners depending on their use.
Classification and Application of Flotation Reagents:
Purpose: To change the hydrophobicity of the mineral surface so that the floating mineral particles adhere to the bubbles.
There are many kinds of flotation collectors, which can be divided into anionic, cationic, amphoteric and nonionic according to their ionic properties; and it can be also divided into sulfide ore flotation collector, oxidized ore flotation collector, non-polar mineral flotation collector and deposited metal flotation collector, according to its application.
Commonly used sulfide ore flotation collectors are xanthate, xanthate derivatives, black medicine, white medicine, benzothiazole thiol, benzimidazole thiol, benzoxazole thiol and the like.
Oxidized ore flotation collectors mainly include fatty acids and their sodium soaps, alkyl sulfonates, alkyl sulfates,phosphates, arsenates, fatty amines and their salts, rosin amines, quaternary ammonium salts, diamines and polyamines compound, an amphoteric surfactant, or the like.
The roles of the flotation collectors on the mineral surface are physical adsorption, chemical adsorption and surface chemical reactions. The adsorption of flotation collectors is closely related to mineral flotation capacity.
With in a certain flotation collector concentration range, as the concentration of the reagent increases, the amount of adsorption increases, and the flotation recovery rate increases significantly. When the concentration reaches a certain value, the recovery rate still increases with the increase of the concentration and the adsorption amount, but the increasing range is lower. When the concentration is too high, the amount of adsorption can continue to increase, but the recovery rate of flotation does not increase, or even decreases. Therefore, in the flotation process, the amount of flotation collectors should be properly mastered to obtain the best benefit.
The formation of foams in the flotation ore slurry depends mainly on various types of aeration stirring devices in the flotation equipment and the addition of an appropriate amount of foaming agent to the ore slurry.
The foaming agent is generally a surfactant whose molecular structure is composed of a non-polar oleophilic (hydrophobic) group and a polar hydrophilic(oleophobic) group, which forms "parent structure" molecule with ahydrophilic and lipophilic type. The oleophilic groups may be aliphatic, alicyclic and aromatic, or aliphatic, alicyclic and aromatic with O and Natoms. Hydrophilic groups generally contain carboxylic acid groups, hydrocarbon groups, sulfonic acid groups, sulfuric acid groups, phosphonic acid groups, amino groups, mercaptan groups, halogen groups, and ether groups and so on.
Common foaming agents are hydroxyl compounds, ethers and ether alcohols, pyridines and ketones.
As a kind of flotation agents, the activation of activators can be roughly divided into spontaneous activation, pre-activation, revitalization and vulcanization.
Spontaneous activation: When processing non-ferrous metal ores by grinding, the mineral surface reacts spontaneously with some soluble salt ions. For example, when zinc blende co-exists with copper sulfide, because of the oxidation after ore mining, there is always a small amount of copper sulfide oxidized to copper sulfate. Cu2+ ions in pulp interact with the surface of sphalerite to activate itself, which makes it difficult to separate copper and zinc. So adding regulators such as lime or sodium carbonate precipitates certain "unavoidable ions" that may cause activation.
Pre-activation: It refers to the activation of a certain mineral in advance by adding an activator. When the pyrite is heavier oxidized, the oxide film of the pyriteon the surface is dissolved by sulfuric acid before the pyrite is processed to expose the fresh surface to facilitate flotation.
Revitalization: It refers to a mineral that has been previously suppressed. For example, sphalerite suppressed with cyanide can be revived by copper sulfate.
Vulcanization: It means that the metal oxide ore is first treated with sodium sulfide to form a film of metal sulfur mineral on the surface of the oxidized ore, and then floated with xanthate.
Inhibitors is a kind of flotation agents which can increase the wettability of mineral particles in flotation so that the minerals do not adhere easily to air bubbles. This flotation agent may be an inorganic compound such as lime, cyanide, etc., or an organic compound such as starch, gum, etc.
Regulators is a kind of flotation agents which is used to change the surface properties of minerals and the characteristics of pulp (such as liquid phase composition, foaming properties, foam properties, etc.). And this flotation agent can not only improve the selectivity of the flotation process,but also improve flotation conditions. So according to its main role in the flotation process, regulators can be divided into inhibitors, activators, acid-base regulators and flocculants.
Note: The classification of flotation reagents in the table is conditional and relative. A certain flotation reagent may belong to different categories under different conditions. For example, sodium sulfide (Na2S) is an inhibitor when flotation of non-ferrous sulfide ore, but an activator (vulcanizing agent) when flotation of non-ferrous oxide ore. However, if it is used in excess, it becomes an inhibitor of flotation oxidized ore.
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According to the effect of the agents, the flotation reagents are mainly divided into three categories: foaming agent, collecting agent and metabolic modifier.
(1) Foaming agent: the organic surface active substance distributed on the air-water interface, such as pine oil, cresol oil, alcohol, etc. The function is to create a foam layer that floats minerals.
(2) Collecting agent: Its function is to collect the targeted minerals. The floating mineral particles adhere to the bubbles by changing the hydrophobicity of the mineral surface. According to the nature of the agents, they can be divided into non-polar collector, an ion collector and cation collector. Common collecting agents are dithiophosphate, xanthate, thiodiphenylurea, fatty acid, aliphaticamine, mineral oil, etc.
(3) Metabolic modifier: Its function is to change the surface properties of mineral particles and the chemical or electrochemical properties of aqueous medium. It can adjust the Ph and the state of collecting agent by affecting the effect of minerals and collecting agent.
④ Flocculant: Polyacrylamide, polyoxyethylene, etc.
⑤ Other: wetting agent, floating agent, solubilizer, etc.
1. Flotation Reagent Consumption
The type and quantity of the agent must be determined by ore flotation test and then verified under industrial conditions. When the amount of collecting agent and foaming agent increases with in a certain limit, the flotation speed can be increased to achieve a better flotation effect. Excessive amount will reduce recovery and concentrate quality. Inhibitors and activators should also be moderate, excessive or insufficient will lead to a bad effect on flotation performance. The amount of flotation reagents should be accurate, since the insufficient or excessive amount will have an impact on the beneficiation index. What’s more, excessive amount will increase the beneficiation cost. The relationship between the amount of various agents and the flotation index is:
Flotation Reagent Type
Insufficient hydrophobicity of minerals causes reducing recovery rate.
The quality of the concentrate is degraded, bring difficulty to flotation extraction process.
Poor foam stability
"Running slot" phenomenon occurs.
The selectivity of the flotation process is destroyed.
Low concentrate grade
The floating minerals are inhibited and the recovery rate is reduced.
2. Flotation Reagent Dosing Point
Dosing points have a great effect on the flotation reagent utility. The flotation pH adjuster and the flotation inhibitor are commonly added to the mill. The insoluble flotation collector can also be added to the mill. The different flotation reagents that can react with each other and cause bucking effects are required to be added separately. Generally, the second flotation reagent is added after the former agent plays its full role.
3. Flotation Reagent Dosing Sequence
The general dosing sequence of the flotation reagent in flotation plant is as follows:
For raw ore flotation process, the dosing sequence of the flotation reagent should be: pH adjuster, inhibitor or activator, foaming agent, flotation collector;
For the inhibited minerals flotation process, the dosing sequence of the flotation reagent should be: activator, flotation collector, foaming agent.
4. Flotation Reagent Dosing Method
There are two dosing methods of flotation reagent. One is to add flotation reagents in once time, and the other is to add flotation reagent in batches. The method of adding flotation reagents in once time is often used, because the concentration of the flotation reagent is locally high, the intensity of action is large, and the addition is convenient. The dosing method of adding flotation reagent in batches or adding flotation reagent points by point can maintain the same concentration of the flotation reagent along the flotation line.
For flotation reagent that are easily removed by the foam, the flotation reagents that are susceptible to reaction in the pulp and the flotation reagents that require strict control of the dosage should be added in batches. The same kind of flotation reagent is used differently, and the dosage and effect are different. This is especially true for flotation reagents that are less soluble or insoluble in water. For example, neutral oils, which are thicker in water, do not require adjustment measures, not only have poor effects, but also increase in dosage.
In order to improve the efficiency of the flotation reagent, the following measures can be taken:
(1) Some water-insoluble flotation reagents can be dissolved in a special solvent;
(2) A solid flotation reagent that is not easily soluble and can be formulated into an emulsion;
(3) For fatty acid flotation collectors,saponification is the most common method;
(4) After emulsification of fatty acids and diesel oil, they can increase their dispersion in the slurry and improve their effectiveness;
(5) Electrochemical treatment and aerosol method can also be used to enhance the action of the flotation reagent. For flotation collectors, foaming agents, flotation inhibitors, flotation flocculants, etc., the different structures of the flotation reagents are mixed in proportion, often better than the use of any of them alone, the mixed use has been widely adopted in various minerals flotation process.
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