Mineral processing professionals must know: 5 most basic mineral processing methods, the principles are easy to understa

For every practitioner or student in the mineral processing field, a deep understanding and mastery of basic mineral processing methods is the golden key to unlocking the door to professional expertise. The separation of useful minerals from gangue minerals in ore is a critical step in the entire mineral resource development and utilization process. The purpose of mineral processing is to enrich useful minerals through various methods, remove harmful impurities, and provide qualified raw materials for subsequent smelting or industrial applications. This article systematically reviews and deeply analyzes five of the most basic and widely used mineral processing methods, aiming to help readers build a clear knowledge framework, ensuring a clear understanding of the principles and straightforward application.

These five core methods are:

•       Gravity Separation
•       Flotation
•       Magnetic Separation
•       Electrostatic Separation
•       Chemical Processing (Hydrometallurgy)

01 Gravity Separation 

Gravity separation (abbreviated as gravity separation) is one of the oldest mineral processing technologies, with its application dating back thousands of years to gold mining. Today, gravity separation remains important in the processing of tungsten, tin, gold, iron ore, and coal, due to its low cost, minimal environmental impact, and high processing capacity.

Core Principle:

Gravity separation is fundamentally based on the density differences between minerals. When mineral particles are in a moving medium (primarily water or air), they are subject to the combined effects of gravity, fluid dynamics, and other mechanical forces. High-density particles settle quickly and settle in the lower layers of the equipment, while low-density particles settle slowly and settle in the upper layers. Specific equipment and process flows can separate these two density groups. Particle size and shape also influence the separation process, so strict particle size control of the incoming material is often required in practice.

Applicable conditions:

• There is a significant density difference between minerals, which is the prerequisite for the effective operation of gravity separation.
• It can handle a wide range of particle sizes and is particularly good at processing coarse-grained ores that are difficult to process with other methods. 
•  It is suitable for processing gold and tin, wolframite, hematite and coal.

Main equipment:

• Jig: It loosens the bed layer and separates it into layers according to density through periodic vertical alternating water flow. It is commonly used to process coarse and medium-sized ores and coal.
•  Shaking table: On an inclined bed, it utilizes the differential reciprocating motion of water flow and bed surface to loosen and separate the ore particles into layers and perform zonal separation. It is suitable for the separation of fine-grained ores.
• Spiral chute/spiral concentrator: It utilizes the combined effects of gravity, centrifugal force and water flow to separate the ore slurry as it flows in the spiral trough. It is suitable for processing fine-grained materials with a particle size of 0.03mm to 0.6mm. 
•  Heavy medium separator: It uses a heavy suspension with a density between useful minerals and gangue as the separation medium. Ore particles with a density less than the medium float up, while those with a density greater than the medium sink, achieving precise separation.

02 Flotation

Flotation is one of the most widely used mineral processing methods, particularly in the processing of non-ferrous metals (copper, lead, zinc), precious metals (gold, silver), and various non-metallic ores.

Core Principles:

Flotation exploits differences in the physical and chemical properties of mineral surfaces—namely, their varying floatability (hydrophobicity). By adding a series of specific flotation agents to a fully ground slurry, these surface properties can be artificially altered.

1. Regulators adjust the slurry's pH, among other factors, to create an optimal environment for other agents to function.

2. Collectors selectively adsorb onto the target mineral surface, rendering it hydrophobic (non-wettable by water).

3. Frothers reduce the surface tension of water, generating a large number of stable bubbles of optimal size.

After treatment with the reagent, the hydrophobic target mineral particles selectively adhere to the bubbles and float to the surface of the slurry, forming a mineralized foam layer. The hydrophilic gangue minerals, on the other hand, remain in the slurry. The foam is scraped off with a scraper to obtain the enriched concentrate.

Applicable conditions:

• Suitable for processing various sulfide ores with fine particle size and complex composition, such as copper, lead, zinc, nickel, molybdenum and other ores. 
• Widely used in the separation of oxide ores, non-metallic ores (such as fluorite, apatite) and precious metal ores.
• Flotation is an extremely effective method for separating minerals with similar density and no obvious difference in magnetic and electrical properties.

Key elements (reagent system):

The effectiveness of flotation depends heavily on the correct reagent system, including reagent type, dosage, order of addition, and location.

• Collectors: These agents, such as xanthates and nitroglycerins, are key to achieving hydrophobicity. 
• Frothers: These agents, such as pine oil (No. 2 oil), are responsible for creating stable foam. 
• Adjusters: These agents include activators (such as copper sulfate), inhibitors (such as lime and cyanide), and pH adjusters, used to enhance or diminish the floatability of minerals and improve separation selectivity.

03 Magnetic Separation

Magnetic separation is a physical method that uses the magnetic difference of minerals for sorting. The process is simple and usually does not cause environmental pollution. It plays an indispensable role in the selection of ferrous metal ores (especially iron ore). It is also widely used to remove iron-containing impurities or recover magnetic substances from other minerals.

Core principle:

When ore particles pass through the uneven magnetic field generated by the magnetic separator, ore particles with different magnetic properties will be subject to magnetic forces of different magnitudes. 

• Strongly magnetic minerals (such as magnetite) will be attracted by the strong magnetic force and adsorbed to the surface of the magnetic pole (such as the magnetic drum). With the movement of the magnetic pole, they are taken to the designated position, leave the magnetic field and fall to become concentrates. 
• Non-magnetic or weakly magnetic minerals (such as quartz and some gangue) are subject to little or almost no magnetic force. Under the action of gravity and centrifugal force, they move along the original path and become tailings.

Applicable conditions:

• Magnetite sorting: Magnetic separation is the most important and efficient method for processing magnetite.
• Sorting other magnetic minerals: It can also be used to sort manganese ore, chromite, ilmenite and some rare metal minerals with weak magnetism (such as wolframite).
• Iron removal: In the purification of non-metallic mineral raw materials such as ceramics and glass, it is used to remove harmful iron impurities to improve the whiteness of the product.
• Heavy medium recovery: In heavy medium coal or ore dressing, it is used to recover magnetic heavy materials such as magnetite powder.

Main equipment:

There are many types of magnetic separators. According to the magnetic field strength, they can be divided into weak magnetic field, medium magnetic field and strong magnetic field magnetic separators; according to the equipment structure, they can be divided into drum type, roller type, disc type and magnetic separation column type.

• Permanent magnet drum magnetic separator: The most widely used, often used to process strongly magnetic magnetite, and divided into co-current, counter-current and semi-counter-current types according to the slurry flow direction. 
• High gradient magnetic separator: It can generate a strong magnetic field gradient, which is used to sort weakly magnetic minerals or remove fine-grained iron impurities. • Magnetic pulley/magnetic drum: Commonly used for dry pre-selection to remove large iron pieces before the material enters the crusher to protect the equipment.

04 Electric separation

Electrostatic separation utilizes differences in the conductive properties of minerals to separate them in a high-voltage electric field. This dry separation method is particularly suitable for water-scarce areas. While not as widely used as the previous three methods, it plays an irreplaceable role in separating certain mineral combinations, such as scheelite from cassiterite and zircon from rutile.

 Core Principle:

The electrostatic separation process primarily involves two steps: charging and separation.When preheated and dried mineral particles enter the high-voltage electric field formed by corona electrodes and rotating rollers: 

• Conductive minerals (such as ilmenite and cassiterite) quickly acquire an electric charge and rapidly dissipate it due to contact with the grounded rollers. After losing their charge, they are thrown from the rollers by centrifugal force and gravity. 
• Non-conductive minerals (such as zircon and quartz) have poor conductivity and are difficult to dissipate after acquiring an electric charge. They are attracted to the roller surface by electrostatic forces, moving to the rear of the roller as the roller rotates, and then being swept away by brushes.Since the two minerals have significantly different motion paths, separation is achieved. 

Applicable Conditions:

• There must be significant differences in electrical conductivity between minerals. Common conductive minerals include magnetite, ilmenite, cassiterite, etc.; non-conductive minerals include quartz, zircon, feldspar, scheelite, etc. 
• Commonly used in the selection of non-ferrous metals, ferrous metals and rare metal ores, especially for separating associated minerals from mixed concentrates of gravity separation or magnetic separation. 
• The materials to be selected must be strictly dry, clean and of uniform particle size. 

Main equipment: 

• Roller electrostatic separator: It is the most commonly used electrostatic separation equipment, which consists of a rotating grounded roller and a high-voltage corona electrode to form a working area.
• Plate/screen plate electrostatic separator: It is used to process materials with different particle size ranges.

05 Chemical Ore Dressing / Hydrometallurgy

Chemical ore dressing, often closely associated with the concept of hydrometallurgy, utilizes chemical reactions to alter the physical phases of mineral components, thereby separating useful components from impurities. This method is particularly suitable for processing low-grade, complex, and finely impregnated ores, such as copper oxide, gold, and uranium ores, which are difficult to separate using traditional physical separation methods.

 Core Principle:

 Its core is selective leaching. Using a specific chemical solvent (leachant), under specific temperature and pressure conditions, the target metal or its compounds in the ore are selectively dissolved into a solution, while the gangue minerals remain in the solid phase (leaching residue).

The main steps include:

      1. Leaching: The ore is treated with a leaching agent such as an acid (such as sulfuric acid), an alkali (such as sodium hydroxide), or a salt solution (such as cyanide) to release the useful metal into the liquid phase. 

      2. Liquid-Solid Separation: The target metal-rich solution (leachate) is separated from the leaching residue.

      3. Solution purification and enrichment: Use precipitation, solvent extraction or ion exchange to remove impurity ions in the solution and increase the concentration of the target metal.

      4. Metal recovery: Extract the final metal product or its compound from the purified solution through electrolysis, displacement or precipitation.

Applicable conditions:

• Processing of low-grade oxide ores: For example, the acid leaching-extraction-electrolysis process for low-grade copper oxide ores. 
• Extraction of precious metals: For example, the cyanide leaching method for gold ores is the most widely used gold extraction process. 
• Processing of complex and difficult-to-separate ores: For ores with similar physical properties and complex interbedded relationships, chemical beneficiation is often the only effective way. 
• Metal recovery from waste: It has broad prospects in areas such as battery recycling and electronic waste treatment. 

Typical processes:

• Cyanide gold extraction: Use sodium cyanide solution to dissolve the gold in the ore, and then replace the gold with zinc powder.
• Acid leaching of copper: Leach the copper oxide ore with dilute sulfuric acid to obtain a copper sulfate solution, which is then extracted and electrolyzed to obtain high-purity cathode copper. 
•  Bayer process for producing alumina: Treating bauxite with sodium hydroxide solution under heated and pressurized conditions is a classic hydrometallurgical process for producing alumina.

The five fundamental methods of mineral separation—gravity separation, flotation, magnetic separation, electrostatic separation, and chemical separation—form the cornerstone of modern mineral processing technology. Each method has its own unique scientific principles and scope of application. In actual production, mineral processing engineers often need to flexibly select a single method or combine multiple methods based on the specific properties of the ore (such as mineral composition, dissemination characteristics, and physical and chemical properties), technical and economic indicators, and environmental protection requirements to develop the optimal mineral processing process, thereby achieving efficient, economical, and green development of mineral resources. A deep understanding and mastery of these fundamental principles is fundamental for every mineral processing engineer to solve practical problems and promote technological innovation.