What types of metals and minerals can a magnetic separator attract, and which materials will pass through?

Yes. Magnetic separation can reduce iron-bearing impurities in silica sand, helping manufacturers meet the raw-material purity requirements of glass, ceramics and other industrial applications. The achievable result depends on the type of iron contamination and the separation process. 🏭

Which impurities can be removed?

Magnetic separators may capture magnetite, certain iron-bearing mineral grains and other magnetically responsive contaminants.

However, iron can occur in different forms:

• Discrete magnetic particles: Often suitable for conventional magnetic separation.

• Weakly magnetic minerals: May require high-intensity or high-gradient separation.

• Iron coatings on quartz grains: Removal may require additional washing or surface-treatment steps.

• Iron incorporated within mineral grains: Magnetic separation alone may not achieve the required reduction.

High-intensity magnetic separation is used in some industrial-mineral applications to remove weakly magnetic impurities from otherwise non-magnetic products.

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How should a silica sand plant select equipment?

First establish the feed particle-size distribution, moisture content, throughput and current iron level. Clarify whether the customer's specification is expressed as total Fe or Fe₂O₃ equivalent, because these are different reporting bases.

Then test a representative sample using the appropriate dry or wet magnetic separation method.

For example, if the feed contains magnetite, a low-intensity separator may remove much of the strongly magnetic fraction. If the remaining iron is associated with weakly magnetic minerals, a higher-intensity stage may be required.

What should the plant measure?

Record feed and product iron content, product yield, throughput and operating conditions. Use consistent sampling and laboratory methods before comparing results.

A separator should not be considered successful simply because visible iron particles are captured. The final product must meet the buyer's chemical specification while maintaining an acceptable recovery rate.

The required magnetic field strength depends on the magnetic susceptibility of the impurity, particle size, feed characteristics, separation distance and target product quality. There is no single field-strength value suitable for every mineral-processing application. ⚙️

Low-intensity versus high-intensity separation

Low-intensity magnetic separation (LIMS) is commonly used to recover strongly magnetic minerals such as magnetite and remove ferrous contamination.

High-intensity magnetic separation (HIMS) is used when the target includes more weakly magnetic minerals, such as certain iron-bearing impurities in silica sand, feldspar and other industrial minerals.

High-gradient magnetic separation can be useful for fine, weakly magnetic particles when the equipment provides the necessary field gradient and capture conditions.

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Which parameters should you check?

• Magnetic field strength, measured in tesla (T) or gauss (G).

• Field gradient, which affects the magnetic force acting on susceptible particles.

• Working gap between the material and magnetic assembly.

• Particle size and degree of mineral liberation.

• Feed rate and material-layer thickness.

• Required iron content in the final product.

For unit conversion, 1 tesla = 10,000 gauss.

A field reading alone does not guarantee good separation. The reading location, operating distance, magnetic circuit and material flow all influence performance.

Practical selection example

If a silica sand plant needs to reduce iron contamination, first test a representative sample and determine which iron-bearing minerals are present. Then compare suitable magnetic separator configurations and operating conditions.

Measure the feed and product iron content using the same analytical method. Also record throughput, product yield and the amount of material rejected.

Do not select a machine solely because its advertised gauss value is higher. The best configuration is the one that achieves the required separation performance at a practical throughput and operating cost.