Lead-zinc Ores Flotation Factors Affecting: Reagents

Lead-zinc ore flotation is a common ore dressing method used to separate lead, zinc minerals, and other associated minerals. The effect of the flotation process is affected by many factors. We have previously described the six factors that affect lead-zinc ore flotation, including grinding fineness, slurry concentration, reagents, foam adjustment, temperature influence, and influence of water quality. In addition to the reagents, we have introduced the other 5 factors in detail in the previous blog post. Today we will ask you to introduce the factors affecting the flotation of lead-zinc ore in detail – reagents.

Flotation Reagents

Flotation reagents are a type of chemical used in the flotation process to change the surface properties of minerals, adjust the pulp environment, and enhance the interaction between minerals and bubbles. They act on minerals or bubbles in the pulp to promote the combination or separation of minerals and bubbles, thereby achieving the separation and enrichment of minerals.

Flotation reagents interact with the mineral surface, chemical components, or bubbles in the slurry, change the hydrophobicity or hydrophilicity of the mineral surface, control whether the mineral can combine with bubbles, and then achieve mineral sorting. Its main mechanism of action includes:

• Adsorption: Collectors change the surface properties of minerals by adsorbing on the mineral surface, making them hydrophobic.
• Chemical reaction: Some reagents change the surface chemical properties of minerals and affect their flotation behavior by chemically reacting with the mineral surface.
• Charge regulation: pH regulators adjust the charge properties of the mineral surface by changing the acidity and alkalinity of the slurry, thereby affecting the effect of flotation reagents.

Reagents Adjustment

The adjustment of reagents in the flotation process includes exerting efficacy, reasonable addition, mixed-use, adjusting the concentration of reagents in the slurry, and controlling the pH value. 

1. Exerting the efficacy

The dosage and effect of the same reagent are different when used in different ways. This is especially obvious for reagents that are insoluble in water or have low solubility in water. The main measures to exert the efficacy are:

• Preparation with solvent
  Neutral oil collectors that are insoluble in water appear as larger droplets in water, which not only have poor effects but also increase the dosage. If they are dissolved in special solvents, such as oleic acid dissolved in kerosene, the collection effect can be improved.
• Prepared into emulsions
  Some solid reagents that are not easily soluble can be prepared into emulsions For example, lime has a very low solubility in water, so it can be ground to 0.1~0. 01mm, mixed with water to form lime milk and added.
• Saponification
  For fatty acid collectors, saponification is the most commonly used method. For example, in iron ore flotation, when preparing tall oil (collector), in order to saponify it, about 10% sodium carbonate is added, and it is heated to make a hot soap solution before addition.

2. Mixed use of drugs

Mixed use of drugs has been widely used in practice. The mixed-use of various collectors is based on the unevenness of the mineral surface and the synergistic effect between the drugs. For example, the mixed-use of xanthate with different warp chain lengths improves its efficacy. When different types of collectors are mixed, one collector is often used as the main one, and the other is used as an “auxiliary collector” or “enhancer”. The mixed-use of inhibitors is even more common. For example, hydride is mixed with zinc sulfate, sulfite is mixed with zinc sulfate, sulfur dioxide is mixed with starch, etc. The purpose is to enhance the inhibitory efficiency of these agents. Mixing frothers can also improve their efficacy.

3. Reasonable addition of reagents

The purpose of reasonable addition of reagents is to ensure that the optimal concentration of reagents is maintained in the slurry. According to the characteristics of the ore, the properties of the reagents, and the requirements of the process, appropriate dosing points can be selected, and different dosing methods can be used to achieve the purpose of maintaining the optimal reagent concentration in the slurry. There are often many types of flotation reagents added to the slurry, plus the various original components of the slurry. The interactions between them are very complex and mutually restrictive. When a reagent system is selected, it is often when these interactions reach a certain balance. Improper use of reagents, sometimes as long as one reagent is added more or less, it may break the balance and cause chaos in the entire process.

• Selection of dosing points
  The dosing point has a great relationship with the effectiveness of the reagents. PH adjusters and inhibitors are mostly added to the mill. Some relatively insoluble collectors can also be added to the mill. Reagents that can react and offset each other are required to be added separately. Generally, the second reagent is added after the first reagent is fully effective. For example, the addition of copper sulfate and xanthate, calcium chloride, and oleic acid, all require a certain order.
• Dosing method
  The reagent can be added at once or in batches. In the case of one-time addition, the reagent concentration is higher at one point, which can increase the initial flotation speed and is convenient to add, so it is often used. In batches or point by point, the reagent concentration along the flotation line can be consistent. For the following situations, batch addition is adopted: First, the reagent that is easily carried away by foam. For example, when oleic acid is used as a collector, it has foaming properties. If it is added at one point, it is easy to be carried away by foam; second, the reagent that is easy to react in the slurry, such as carbon dioxide, sulfur dioxide, etc., will quickly react and fail if it is only added at one point. Third, the reagent that requires strict control of dosage, such as sodium sulfide, will lose its selectivity if the local concentration is too large, so it should be added in batches.

4. Slurry pH control

The slurry pH value is an important factor in the flotation process. On the one hand, it affects the flotation properties of the mineral surface; on the other hand, it affects the effects of various flotation reagents. Each ore has a more suitable pH range for flotation.

The addition and adjustment of reagents are important process factors in the flotation process, which significantly impact the efficacy of reagents and improve flotation indicators. Especially for single-tank flotation machines, flotation workers need to add reagents more accurately according to the concentration and particle size of the ore. Flotation reagents are vital in the flotation of lead and zinc ores. Their reasonable addition and use directly affect the efficiency of flotation and the effect of mineral separation.