What do DMS powders do? An in-depth guide to Dense Media Separation

December 18, 2025 •

4 min read

In the mineral processing industry, over a century of proven application has established Dense Media Separation (DMS) as a highly efficient method for sorting materials. DMS powders are the core ingredient in this process, creating a liquid medium with a precisely controlled density to differentiate valuable minerals from waste rock.

Quick Summary

DMS powders, such as ferrosilicon or magnetite, are used to create high-density liquid suspensions for separating minerals and other materials based on their specific gravity in a sink-float process.

Key Points

Density Separation: DMS powders, mainly ferrosilicon or magnetite, are mixed with water to form a heavy liquid, separating materials by density.
Sink-Float Principle: Heavier materials sink in the heavy liquid medium, while lighter materials float, allowing for precise separation.
Diverse Applications: DMS technology is used for recovering diamonds, washing coal, beneficiating iron ore, and separating materials in recycling.
Particle Shape Matters: Atomized ferrosilicon provides more spherical particles resulting in a lower viscosity medium, while milled ferrosilicon has angular particles with higher viscosity.
Magnetic Recovery: Both ferrosilicon and magnetite are magnetic, allowing for easy and cost-effective recovery and recycling of the medium.
A Different DMS Exists: In organic chemistry, Dimethyl Sulfide (DMS) is a distinct, volatile liquid used for chemical synthesis, unrelated to DMS powders.
Safety Precautions: Fine dust should be handled with ventilation, and long-term wet storage of ferrosilicon requires oxygen precautions due to potential hydrogen generation.

Understanding the Core Function of DMS Powders

DMS powders are not a single substance but a class of finely ground, high-density materials, most commonly ferrosilicon (an iron-silicon alloy) or magnetite (an iron oxide). Their fundamental purpose is to be mixed with water to form a liquid suspension, often called a 'heavy medium' or 'heavy liquid,' that has a specific gravity higher than water. The density of this liquid can be precisely controlled by adjusting the ratio of water to powder. This custom-engineered density is key to the entire Dense Media Separation process.

The Dense Media Separation (DMS) Mechanism

The separation mechanism hinges on the principle of buoyancy and gravitational force. When a mixture of crushed materials (an ore, for example) is introduced into the dense medium, particles will behave in one of two ways:

Sinks: Particles with a density higher than the surrounding heavy medium will sink to the bottom. These are typically the valuable minerals being recovered.
Floats: Particles with a density lower than the medium will float on the surface. These are typically the lighter waste materials, or 'gangue.'

This simple, yet highly effective 'sink-float' method allows for an extremely sharp and efficient separation. The magnetic properties of ferrosilicon and magnetite also allow for easy recovery of the powder from the separated products using magnetic separators, which is essential for recycling the medium and reducing operational costs.

Key Applications Across Industries

DMS technology, powered by these specialized powders, has a wide range of applications in modern industry. Its use is prevalent where the efficient separation of materials based on density is required.

Diamond Recovery: One of the most famous applications is in the diamond mining industry, where DMS is used to separate diamonds (with a density of approximately 3.52 g/cm³) from lighter host rock like kimberlite (with a density of 2.6-2.8 g/cm³).
Coal Preparation: To improve combustion efficiency and reduce ash content, raw coal is washed using DMS to separate clean coal from heavier impurities like rock and pyrite. Magnetite powder is commonly used for this lower-density separation.
Iron Ore Beneficiation: In the steel industry, DMS helps upgrade lower-grade iron ore by removing waste materials like silica and alumina, reducing energy consumption during smelting.
Recycling: The process is used to separate valuable non-ferrous metals from scrap materials, including plastics, glass, and electronic waste.
Industrial Minerals: DMS is employed to process a variety of other industrial minerals, such as fluorspar, barite, and magnesite, from associated waste.

Milled vs. Atomized Ferrosilicon Powders

DMS powders come in different grades and forms, with ferrosilicon being produced in both milled and atomized forms. The manufacturing process directly affects the powder's physical properties, which in turn impacts the performance of the dense medium suspension.

Milled Ferrosilicon: Produced by crushing and milling the alloy, resulting in more angular, irregularly shaped particles.
Atomized Ferrosilicon: Created by casting molten ferrosilicon into a high-pressure water jet, producing spherical particles with a finer, more consistent size distribution.

Comparison Table: Milled vs. Atomized Ferrosilicon


Feature	Milled Ferrosilicon	Atomized Ferrosilicon
Particle Shape	Angular, irregular	Spherical, uniform
Particle Size	Varies, can be less consistent	Narrower, more predictable distribution
Viscosity	Higher viscosity for a given density	Lower viscosity for a given density
Medium Stability	Good, but can be influenced by irregular shapes	Very high stability and medium fluidity
Abrasion/Wear	Can cause more wear on pumps and equipment due to angularity	Causes less wear on plant equipment
Recovery	Excellent magnetic recovery	Excellent magnetic recovery

The Other 'DMS': Dimethyl Sulfide

It is important to note that a different chemical, Dimethyl Sulfide, also uses the acronym DMS. This is a colorless, flammable organic compound used in a completely different context, primarily in organic chemistry for synthesis and as a reducing agent in reactions like ozonolysis. It is a volatile liquid and is not used in the form of a high-density powder for physical separation applications. Confusion between these two distinct uses of the acronym should be avoided, especially in an industrial or laboratory setting where safe handling is paramount.

Handling and Safety Precautions

While DMS powders like ferrosilicon are generally considered safe, proper handling is necessary, particularly in an industrial environment. When stored correctly in a dry, well-ventilated area, they pose minimal risk. However, there are considerations for wet storage and dust handling:

Dust: Fine metallic dust generated during handling can, under extreme conditions, become flammable. Proper ventilation and personal protective equipment (PPE) like respirators are crucial to prevent inhalation.
Wet Storage: Storing ferrosilicon slurry under depleted oxygen for prolonged periods can generate small amounts of hydrogen gas. Equipment containing slurry should be well-ventilated before maintenance. Additionally, moisture can cause corrosion of metal components.
Waste Disposal: Spent medium and contaminated materials should be disposed of in accordance with local regulations.

Conclusion

DMS powders serve a critical function in the industrial world, enabling the efficient and cost-effective separation of materials based on density. By forming a controllable heavy liquid medium, these powders, primarily ferrosilicon and magnetite, allow industries like mining and recycling to purify valuable resources from waste. The choice between different powder types, like milled or atomized ferrosilicon, is based on specific process requirements concerning viscosity, stability, and equipment wear. While the acronym DMS also refers to a different chemical in organic synthesis, the powder form is exclusively linked to the density-based separation process that underpins many modern industrial operations. The success of DMS lies in its simplicity and versatility, making it an enduring and fundamental technology in mineral processing.

For more technical insight into the dense medium process, the Southern African Institute of Mining and Metallurgy offers valuable resources on its application, such as their article [The art and science of dense medium selection](https://www.saimm.co.za/Journal/v114n07p529.pdf).

Frequently Asked Questions

The primary function of DMS powders is to create a high-density liquid suspension when mixed with water. This heavy liquid acts as the medium in the Dense Media Separation process, separating materials based on their specific gravity.

DMS powders are most commonly made from either finely ground ferrosilicon (an alloy of iron and silicon) or magnetite (an iron oxide).

In the DMS process, crushed ore is introduced into the heavy liquid medium created with DMS powders. Particles that are denser than the liquid sink, while lighter particles float. These separated streams are then collected for further processing.

Advantages include high separation efficiency, the ability to control the exact separation density, and the magnetic properties that allow for excellent recovery and recycling of the medium, which reduces operating costs.

Milled ferrosilicon has more angular, irregular particles, while atomized ferrosilicon has spherical, more uniform particles. Atomized powder generally produces a lower-viscosity, more stable medium.

After separation, the DMS powders are magnetically recovered from the separated products using magnetic separators. This allows for efficient recycling and reuse of the expensive medium.

Yes. While not highly hazardous, proper handling is needed. This includes using PPE to avoid inhaling dust and ensuring good ventilation when storing wet slurry to prevent potential hydrogen gas buildup.