Mineral Flotation: Process, Reagents, and Variables
Flotation in mining is a physicochemical process widely used for the separation of sulfide minerals from their concentration or the separation of different mineralized species, exploiting the properties of hydrophobicity. It is induced by chemical reagents: collector, foaming agents, and modifiers.
Objective of Flotation
The flotation process is based on the hydrophilic and hydrophobic properties of minerals. This is essentially a behavioral phenomenon of solids in water. Flotation is performed using the pulp from the mill that has already been integrated. The pulp is introduced into a container called a flotation cell, in which air is bubbled to ensure intensive contact with the particles.
Types of Flotation
- Conventional Flotation: Works with a particle size between 0.3 to 0.002 mm, depending on the specific gravity of the species.
- Columnar Flotation: Applies to particles with a much finer grain size, less than 0.02 mm.
- Collective Flotation: Separates several components into two groups, where the concentrate has two or more components.
- Selective or Differential Flotation: Separates complex compounds into products containing no more than one species individually.
Flotation Operation Technology
It consists of selectively separating the hydrophobic particles from the hydrophilic ones. This is done in machines that have mechanical agitation to keep the solid particles suspended, using an air injection device for filling and emptying the product.
Flotation Reagents
One of the most important components in the flotation process are the reagents used:
- Collectors: Heteropolar organic compounds that are selectively absorbed on the surface of the particles, causing them to become hydrophobic. Their mission is to impregnate the particles of copper sulfide and molybdenum to separate them from water.
- Foaming Reagents: Aim to produce resistant bubbles.
- Modifiers: Serve to regulate the operating conditions of the collectors and increase their selectivity, including pH regulators.
Modifiers
The modifier is based on the direct result and not the end. Modifiers can operate as:
- pH Modifiers
- Surface Modifiers
- Precipitants for Soluble Salts
pH Modifiers
The effectiveness of all types of flotation agents depends largely on the degree of alkalinity or acidity of the pulp solution.
Surface Modifications
Improve the selectivity of the flotation process. It is probably the most important and complex function carried out by modifying agents.
Foaming Agents
Surfactants: Mineralized particles that remain on the surface of the solution and play an active role in the kinetics of flotation.
Types of Foaming Agents
All foaming agents in use are heteropolar organic compounds. The nonpolar organic radical, like the molecule in a flotation collector, repels water, while the polar attraction attracts it.
Properties of Natural Buoyancy
Explained by the crystal structure of these species, being of a laminar type, exposing the solution to expensive inert materials.
Variables of the Flotation Process
- Grind: Degree of liberation. The overall trend is to grind as little as possible due to the cost of the operation. This is limited by particle size and the degree of liberation of useful species.
- Type and Dosage of Reagents: Consider the different families of collectors, foaming agents, and modifiers.
- Density of the Pulp: There is an optimal solid percentage for the process, as it affects the residence time of ore in the circuit. Primary stage: 20 to 35 percent. Cover clean: 15 to 20 percent.
- Aeration and Conditioning: Can be a key step in the process because it provides the time necessary for the reactants to operate.
- Regulation of pH: Flotation is very sensitive to pH changes, especially in selective flotation circuits.
- Residence Time: A mineral can be characterized by its flotation kinetics, and more individuals by the specified constant speed.
- Temperature: A few minerals show improved efficiency with increased temperature of the pulp.
- Water Quality: In most plants, the availability of water is a serious problem.
- Aging Pulp: It is advisable to work with aged pulp, over 8 hours of preparation, because it can cause distortions in species recovery.
- Aging of the Sample: Comes in the sample for laboratory testing and pilot plant.
Specific Reagents
- Collector: Armac, acetate which is a hydrogenated tallow amine. Its main properties are: Appearance at 25 degrees, specific gravity, specific range.
- Foaming Agent: MIBC (Methyl Isobutyl Carbinol). Its properties are: Purity 98, specific gravity 20, flash point 41.