Effect of coal slime on lead-zinc ore flotation process

01 Effect of coal slime on lead-zinc ore flotation

(1) Reduce vulcanization

In the process of oxidized ore flotation, lead oxide minerals are often sulfated in alkaline slurry (usually sodium sulfide), so that the surface of the lead oxide minerals is coated with a sulfide film, and then xanthate-type collectors are used for flotation. However, lead oxide minerals will be seriously affected by sludge during the sulfurization process: ① Slime consumes a large amount of sulfurizing agent. ② Mucus affects the hydrolysis rate of the vulcanizing agent.

(2) Reduce flotation recovery rate

Coal slime often pollutes the surface of oxidized ores, especially zinc oxide ores, which are easily contaminated by iron hydroxide and lose their original floating properties. Sludge covering the surface of coarse-grained minerals will hinder the adhesion of the coarse-grained target minerals to the collector and the reaction of the collector with bubbles on the surface of the coarse-grained minerals, thereby reducing the flotation recovery rate.

(3) Reduce the grade of flotation concentrate

Fine particles tend to adhere to the liquid-gas interface, while fine-grained sludge in coal gangue adheres to the interface. Both will enter the concentrate product along with the foam, reducing the concentrate grade.

The physical and chemical properties of the surface of fine-grained minerals are different from those of coarse-grained minerals. The fine particles have a large surface area and high surface free energy, which reduces the separation and adsorption performance of the collector. Regardless of the surface electrochemical properties and double electric layer properties, the agent can be adsorbed and float non-target minerals such as pomegranate seeds and calcite, affecting the concentrate grade.

02 Solution

(1) Separation and processing of coal slime and minerals

In order to reduce the impact of slime on lead-zinc ore flotation, the slime can be separated first and then the flotation process can be carried out. Commonly used methods mainly include the following:

Selective flocculation and flotation. After adding the collector, the particles flocculate and float through high-intensity stirring under the action of hydrophobic association.

Carrier flotation. Using floating minerals of appropriate particle size as carriers, the fine particles attached to them float. Reunion flotation. Also known as emulsion flotation, it refers to the clumps formed by the interaction of fine-grained minerals with collectors and neutral oil.

Microbubble flotation. Fine particles are flotated using air pressure method and variable pressure (pressure, pressure reduction) method.

In addition to the above four methods, there are also electrolytic flotation, electric flotation, electromagnetic flotation, etc.

(2) Ore pretreatment - desliming

In order to reduce the impact of sludge on mineral processing, desludge can be carried out before mineral processing. The staged desliming method (usually a cyclone) is commonly used, but excessive desliming will reduce the recovery rate of zinc.

(3) Add mucus dispersant

Slime dispersants can disperse coal slime and eliminate the harmful effects of fine slime covering the surface of other minerals. Commonly used dispersants include sodium silicate, sodium carbonate, sodium hexametaphosphate, etc.

(4) Add in batches

In order to maintain the effective concentration of the agent in the slurry, the agent can be added in batches to avoid being adsorbed by the coal slime at once.

(5) Maintain slurry concentration

The use of slurry concentration can disperse the coal slime, reduce the viscosity and surface coverage of coarse particles, and also reduce the pollution of the concentrated foam by the coal slime.

The above is the impact of coal slime on the lead-zinc ore flotation process and its solutions. Lead-zinc oxide ore often contains a variety of primary mud (kaolin, sericite, limonite, etc.) and secondary mud (mud produced during crushing, grinding, and transportation), which will seriously affect the flotation process of lead-zinc ore. In actual production, an appropriate desliming process can be selected according to actual conditions to reduce the impact of coal slime on flotation.