Liaoning Xinda Talc Group Co., Ltd. - Jia Weidong
In the application of talcum powder, people often mention the mineral iron sulfide in a certain area, and avoid talc ores containing this impurity. What is the iron sulfide referred to? Why are minerals containing iron sulfide more resistant?
In fact, in natural talc mines, there are many areas associated with pyrite impurities, which are commonly known as iron sulfide. Even if the content is extremely low, it has a significant negative impact on the quality of talc powder.
What is pyrite? It is currently the most abundant sulfide known on Earth, mainly composed of FeS2, light brass color, strong metallic luster with metallic luster, hardness of 6-6.5, and often associated in talc ore. Due to its regular polyhedral structure, clustered form, and brass metallic luster, it is often mistaken for gold. In mineralogy, pyrite is also called "fool's gold", and high-purity pyrite is used as a cheap gemstone for viewing. How to distinguish between pyrite and natural gold? Steel needles or knives can be used for carving, natural gold can create bright grooves on its surface, while pyrite hardness cannot be scratched; Using the method of biting to distinguish authenticity, human teeth can bite natural gold but not pyrite; Scratch method, the stripe color of natural gold is yellow to reddish yellow, while the stripe color of pyrite is green black; Pyrite is brittle and fractures upon impact, while natural gold has strong ductility and undergoes plastic deformation under stress without shattering.
The easy oxidation, alteration, and weathering properties of pyrite have adverse effects on the downstream customers of talc powder.
Due to the high hardness of pyrite, there is a sharp increase in equipment wear during the processing; At the same time, pyrite is prone to surface oxidation in air, especially during the grinding process, where the surface quickly oxidizes and turns black, greatly reducing the whiteness of talc powder, which in turn affects the whiteness and glossiness of downstream plastics, papermaking, and coatings. Under surface conditions, pyrite is also prone to weathering into limonite.
The main chemical reaction equation of pyrite in humid environments is 2FeS2+7O2+2H2O=2FeSO4+2H2SO4. The generated sulfuric acid affects the chemical stability of talc powder. This is not evident in associated mines, but in pyrite mines, it is the cause of a large amount of mine acid water pollution. In anti-corrosion coatings, it will form its own acid pitting corrosion, which will affect the anti-corrosion effect; Directly disrupting the system equilibrium in alkaline papermaking; In plastics, due to the oxidation catalyst of iron ions (Fe2+/Fe3+) polymer materials (PE/PP, etc.), the aging and degradation of polymer materials during high-temperature processing can be accelerated, leading to yellowing and brittleness of plastics.
In aqueous systems, acidic substances will be generated, causing corrosion to metal pipeline equipment.
Method for removing pyrite:
1. Manual identification and selection after mining;
2. By utilizing its weak magnetism, high gradient strong magnetic beneficiation can be achieved after crushing;
3. Utilize its good floatability for flotation removal, but its floatability is similar to that of talc, requiring the use of inhibitors for system adjustment;
4. Use acid washing to remove iron, which can deeply remove iron, but wastewater treatment is a major issue. At the same time, careful research is needed on other changes that may be caused by talc powder.
In summary, the presence of pyrite is a key impurity for the high-end application of talc powder. When pyrite is present in talc ore, it needs to be treated according to its economic and technological value.
