The Ultimate Guide of Flotation Reagent

1. Flotation Collectors

The main function of the flotation collectors is to change the hydrophilicity of the mineral surface, enhance its hydrophobicity, and increase the adhesion of the mineral on the bubble, which can make it floatable and shorten the induction time.

Since most of the minerals in nature are hydrophilic, the flotation collector is widely used in flotation operations as a kind of flotation reagent. Generally, it can be divided into polar collectors and non-polar collectors. The commonly used collectors for flotation are mainly xanthate ,dithiophosphate and thiocarbanilide, etc.

2. Flotation Frothers

The main function of the flotation frothers is to promote the formation of uniform bubbles and enhance the elasticity of the surface of the bubble. It can also make the bubbles generated by flotation more stable and not easily deformed. Even when subjected to vibration or other external force, bubbles are less likely to rupture. In addition, the stability of the foam is also affected by the pH of the pulp, the soluble salt content, etc. The commonly used flotation frothers are mainly pine oil ,methyl isobutyl carbinol (MIBC) and so on.

3. Flotation Conditioners

The main function of the flotation conditioners is to adjust the interaction between the collector and the mineral, adjust the pH of the slurry, and promote or inhibit the floatability of the mineral. According to the effect of the conditioners, it can be divided into the following categories:

• pH modifiers: It is mainly used to adjust the pH value of the slurry, control the surface characteristics of the mineral and the chemical composition of the slurry to achieve the conditions required for flotation. Commonly used pH modifiers are lime, sodium carbonate, sulfuric acid and sodium hydroxide, etc.
• Activators: It is mainly used to enhance the floatability of minerals, change the composition of the mineral surface, and enhance the effect of the flotation collectors. The non-floating minerals can float under the action of the activators. Among the flotation reagents, commonly used activators for flotation are sulfuric acid, sulfurous acid, sodium sulfide, copper sulfate and so on.
• Inhibitors: It is mainly used to increase the hydrophilicity of minerals and to form a hydrophilic film on the surface of the ore particles. At the same time, it inhibits the action of the collectors on the mineral and reduces the floatability of the mineral. Among the flotation reagents, commonly used inhibitors for flotation are sodium thioglycolate, sodium sulfide, sodium silicate and sodium cyanide.
• Dispersants: It is mainly used to prevent the aggregation of fine-grained minerals and make them in a monomer state. The particles can be easily wetted in the medium while remaining in a dispersed state. Commonly used dispersants mainly include sodium silicate and phosphate.

Froth flotation has certain requirements on the amount of flotation reagent dosage. Insufficient or excessive flotation reagents will affect the efficiency of mineral flotation.

If the collectors is insufficient, it will result in insufficient hydrophobicity of the useful minerals and reduce the recovery rate; if the collectors is excessive, the grade of concentrate will decrease.

If the flotation frothers is insufficient, the foam is poor in stability and easily broken; if the flotation frothers is excessive, "run slot" phenomenon may occur.

If the inhibitors is insufficient, the content of impurities in concentrate will increase; if the inhibitor is excessive, the mineral which should be floated will be inhibited and the flotation recovery rate will be reduced.

Due to the difference in properties of different ores, the fluctuation range of the flotation reagent dosage is different. Even for the same ore, the content of useful minerals and gangue minerals will be different. Therefore, in actual mineral flotation, a proper flotation reagent dosage needs to be determined according to the mineral dressing test. The dosage range of commonly used flotation reagents can be referred to the following data:

Flotation Collectors: 20-1500g/t,

Flotation Frothers: 20-2000g/t,

Flotation Activators: 200-1000g/t,

Flotation Inhibitors: 100-200g/t,

Medium conditioners: 500-3000g/t

There are many methods for preparing flotation reagents. With different preparation methods, the dosage and effect of the same flotation reagents are also very different. Proper preparation of flotation reagents before use will play an important role in improving the efficiency of the flotation reagent. Next, we will introduce 6 commonly used preparation methods of flotation reagents.

1. Formulating the Flotation Reagent into Aqueous Solutions

Most water-soluble flotation reagents can be formulated in this way and are typically formulated as 5% to 10% aqueous solutions. Flotation reagents using this preparation method include xanthate, copper sulfate, sodium silicate, and the like. When preparing an aqueous solution, we often dissolve the flotation reagent in the container with a small amount of water. When the dissolution of flotation reagent is finished, more water can be gradually added to reach the desired concentration.

2. Adding Solvent to Dissolve the Flotation Reagent

For some flotation reagents that are insoluble or poorly soluble in water, a good preparing method is to dissolve them into some special solvent before use. For example, CS(NHC6H5)2 is insoluble in water, but is soluble in an aniline solution with a concentration of 10% to 20%. So it can be used after it is formulated into an aniline mixed solution.

3. Formulating the Flotation Reagent into Emulsion or Suspension

For some non-soluble solid flotation reagents, it can be formulated into an emulsion. For example, the solubility of lime in water is very small. We can grind the lime into powder, and add water to make it into a milky suspension (such as calcium hydroxide). Or it can be directly added to the ball mill as dry powder.

4. Saponification of flotation reagent

For fatty acid collectors, saponification is the most common method. In order to improve the water solubility of the mixed flotation reagent, we can add about 10% of sodium carbonate to saponify the tall oil and heat the mixture with hot water to prepare a hot soap liquid when preparing the flotation reagent.

5. Adding as the Original Solution

Some flotation reagents (such as pine oil, dithiophosphate 25, kerosene, etc.) have very low water solubility, and it is difficult to formulate a true solution or a stable emulsion. Instead of formulating it into a solution, it can be directly added into the ore pulp according to the dosage.

6. Aerosol Method

The aerosol method is a new preparation method that enhances the effect of flotation reagents. The essence of this method is to use a special spray device to directly add the flotation reagent to the flotation cell after the flotation reagent is atomized in the air medium. This method can not only improve the floatability of useful minerals, but also significantly reduce the dosage of flotation reagents.

The choice of the adding location of flotation reagents is usually related to the usage and solubility of the flotation reagents. In order to fully utilize the action of the flotation reagents, the selection of the addition location is usually the following.

• Add flotation reagents like flotation conditioners, inhibitors and part of flotation collectors to the ball mill to create a suitable flotation environment as early as possible.
• The flotation collectors and flotation frothers are typically added to the first agitation tank of the flotation process. If there are 2 agitation tanks in the flotation process, then the activators should be added to the first agitation tank and the flotation collectors and flotation frothers should be added to the second agitation tank.
• Depending on the role of the flotation reagents in the flotation cell, the adding location of the flotation reagents is different. For the three flotation reagents of copper sulfate, xanthate and pine oil, the general order of addition is that copper sulfate is added to the center of the first agitation tank, xanthate is added to the center of the second agitation tank, and pine oil is added to the outlet of the second agitation tank.

In actual production, the adding order of flotation reagents is generally:

1. Flotation for Raw Ore

pH Modifiers → Inhibitors or Activators → Flotation Frothers → Flotation Collectors

2. Flotation for Suppressed Minerals

Activators → Flotation Collectors → Flotation Frothers

The way in which flotation reagents are added is usually divided into one-time additions and phased additions.

One-time addition means that all the flotation reagents are added to the slurry at one time before the flotation is carried out, which is beneficial to increase the initial speed of the flotation process and is also a convenient adding method. However, as the flotation process progresses, the flotation speed will slowly decrease. However, the overall flotation time is still short, which can improve the efficiency of flotation to a certain extent. The adding method of flotation reagents is mainly applicable to those flotation reagents which are easily soluble in water and which are not easily carried away by the foam, and which do not fail in the slurry due to the reaction, such as xanthate, sodium bicarbonate and lime.

Phased addition means that the flotation reagents is added to the slurry multiple times during the flotation process. Generally, 60%-70% of the total amount of flotation reagents is added before the flotation, and the remaining 30%-40% of the flotation reagents is added to the appropriate place during the flotation process. Such a flotation reagents addition method is beneficial to improve the quality of the concentrate. However, due to the low speed of the initial reaction during the flotation process, the entire flotation time will increase. Phased addition is mainly applicable to the following types of flotation reagents:

• The flotation reagents that are difficult to dissolve in water and are easily carried away by mechanical foam, such as oleic acid and fatty amine collectors, which require phased additions to ensure their effectiveness.
• The flotation reagents that are easily decomposed during the reaction with the slurry, such as carbon dioxide and sulfur dioxide. If it is added only once, it will soon be ineffective with the reaction of the slurry, so it is necessary to add in batches to achieve the effect of continuous reaction.
• The flotation reagents whose dosage requires strict control, such us sodium sulfide. When the local concentration is too large, the selection effect of the flotation reagents will be weakened. Therefore, it is necessary to add in batches to ensure that the concentration of the flotation reagents is maintained to a certain level.