Graphite is an extremely important non-metallic mineral. After purification, it can be applied in a wide range of industries—including electronics and optics, power generation, aerospace, environmental protection, and new materials—thus playing a crucial strategic role in the beneficiation plants dedicated to its purification.

Graphite deposits often occur in association with minerals such as quartz, illite, kaolinite, andalusite, sericite, as well as small amounts of hematite, limonite, tourmaline, and dolomite. These impurities must be removed through purification processes before the graphite can be utilized. The six most common graphite purification methods are selective flocculation, flotation, alkali-acid treatment, leaching, chlorination roasting, and high-temperature calcination.

1. Graphite Flotation Equipment – Selective Flocculation Method for Graphite Ore

The selective flocculation method for purifying graphite ore involves adding a polymeric flocculant to a mixed liquid containing two or more types of components. This allows the flocculant to selectively adsorb certain components in the mixed liquid and, through bridging action, induce flocculation and sedimentation, thereby achieving separation of the desired components.

The main coagulants include sodium metasilicate, sodium hexametaphosphate, cassava starch derived from木质 cellulose, hydroxymethyl cellulose, and sodium silicate as thickening agents. Cassava starch, acorn flour, sodium alginate, and polyferric sulfate are used as coagulants for the purification of graphite ore.

Selective flocculation purification method for graphite ore and Graphite flotation equipment They are relatively simple and low in cost, but their fixed carbon utilization rate is relatively low, at only around 40%.

2. Flotation of graphite ore

Flotation reagents are a commonly used method for purifying graphite ores. They work by adding a series of flotation reagents that selectively aggregate the target minerals at the gas-liquid interface, thereby separating them from the residual minerals and achieving the desired purification effect.

Graphite itself possesses excellent natural floatability and hydrophobicity, enabling conventional graphite ores to be purified efficiently through flotation processes. During the purification stage, to protect the large flake structure of the graphite, the process typically involves two-stage grinding, multiple stages of separation, and regrinding and re-selection of the rough concentrate.

Graphite flotation equipment

The flotation reagents commonly used in graphite flotation equipment are mostly medium-temperature coal tar, while emulsifiers are typically pine oil or butyl ether oil, and retarders are usually sodium silicate and sodium fluorosilicate.

Graphite flotation equipment can purify graphite to a grade of 80% to 90%, or even around 95%. This method features low reagent consumption, low energy use, and low costs. However, when graphite ores contain extremely fine clay minerals as well as classic organic substances such as potassium, calcium, sodium, magnesium, and aluminum, it becomes difficult to achieve complete dissociation during the grinding stage. Therefore, after flotation, additional processing techniques must be employed for further purification.

3. Alkaline-acid method for graphite ore

The strong acid–strong base method for purifying graphite ore is currently a relatively well-established process, which can be divided into two main stages: alkali fusion and leaching.

The entire alkali fusion process involves, under high-temperature conditions, allowing the alkali in the molten state to react chemically with acidic and basic residues present in graphite—such as aluminosilicates, silicoaluminate phosphates, and quartz—resulting in the formation of soluble salts. These salts are then removed by washing to eliminate impurities.

The entire leaching process involves using an acid to react with the hydroxide residues, converting some of the unreacted residues from the alkali fusion step into soluble salts. These salts are then removed by washing to separate them from the graphite, thereby enhancing the purity of the graphite.

The alkali-acid method for purifying graphite ore can achieve a graphite purity of up to 99.5%, and the equipment required is simple, energy consumption is low, and initial investment is relatively small. However, this method uses strong acids and strong bases, which can cause significant corrosion to the system, and the wastewater generated after purification is highly polluted. Moreover, there is also the drawback of graphite leakage.