Quartz sand is made from crushed and processed quartz stones, resulting in quartz particles. Quartz sand can contain various impurities, including mica, feldspar, iron, aluminum, and apatite, among others. It's known that the higher the purity of quartz sand, the higher its market value. If impurities can be removed from quartz sand, its quality can be improved, leading to higher profits. So, how can quartz sand be purified by removing impurities? Here are some common methods.
1.Gravity Separation
Gravity separation is used to remove impurities from quartz sand based on the density differences between quartz and impurity minerals. This method is often employed to eliminate heavy mineral impurities or coarse particle impurities, such as zircon, which is heavier than quartz sand and can be easily separated using gravity separation. Common equipment used in gravity separation includes shaking tables, spiral chutes, and jig machines.
2.Magnetic Separation
Magnetic separation is used to remove impurities that exhibit magnetic properties, such as iron. Impurities in quartz sand often include various forms of iron minerals, including hematite, goethite, and magnetite. Since iron is typically magnetic while quartz sand is not, magnetic separation can effectively remove iron impurities. Common equipment used in magnetic separation includes magnetic drums, electromagnetic separators, and high-gradient magnetic separators.
3.Froth Flotation
Froth flotation is a widely used method for removing various impurities from quartz sand. It can effectively remove impurities like mica, feldspar, aluminum, and apatite, playing a crucial role in improving the purity of quartz sand. Froth flotation equipment commonly used includes flotation machines, often using combinations like XCF-KYF units or BF-JJF units to perform roughing, scavenging, and cleaning operations.
4.Scrubbing
Scrubbing is typically used to remove thin film iron or clay-like impurities from the surface of quartz sand. During the crushing and grinding of quartz ore, some impurities may become finely ground into clay or form a thin iron film on the surface of quartz sand. Scrubbing methods can effectively remove these impurities. Common scrubbing equipment includes spiral groove scrubbers, high-efficiency agitation scrubbers, and rod mills.
In practical production, physical methods are capable of removing most impurities. However, when certain impurities cannot be removed by physical methods, chemical methods may be employed to further purify quartz sand. Common chemical methods include:
1.Acid Leaching
Acid leaching is primarily used to remove impurities that are soluble in acids, such as iron oxide and some clay minerals. Common acids used in acid leaching are hydrochloric acid or sulfuric acid. A simple method to determine if acid leaching is necessary is to observe the color of the final product or the quartz sand after impurity removal. If the color is reddish, it indicates a high iron and titanium content, which may require acid leaching. The process involves washing the sand with water, followed by acid leaching and final drying.
2.Alkali Leaching
Alkali leaching is generally used to remove organic impurities or clay minerals, as these substances react with alkaline solutions and can be separated from quartz sand. Sodium hydroxide (lye) is commonly used as the alkaline solution.
3.Heat Treatment
Heat treatment involves subjecting the quartz sand to high temperatures to remove impurities. This method is typically used to remove organic substances and soluble impurities. By heating the sand to specific temperatures, volatile impurities can be removed, and some harmful impurities can be transformed into harmless forms.
In addition to the physical and chemical methods mentioned above, there are some less commonly used methods for purifying quartz sand, including:
1.High-Pressure Water Washing
High-pressure water washing involves using high-pressure water jets to strip and remove impurities from quartz sand. This method is effective at removing surface coatings, clay particles, and fine impurities.
2.Electrostatic Separation
Electrostatic separation utilizes the difference in electrical conductivity between quartz and impurities to separate them. By applying an electric field, particles can be selectively charged and separated based on their conductivity. This method can be used in the sorting of quartz sand.
3.Ultrasonic Treatment
Ultrasonic treatment employs high-frequency sound waves to agitate and remove impurities from quartz sand. This method is effective at removing surface coatings, fine particles, and stubborn impurities.
In general, physical methods can remove most impurities, and chemical methods are used when physical methods are insufficient. High-pressure water washing, electrostatic separation, and ultrasonic treatment are seldom employed due to their limited applicability and higher costs. When determining the appropriate impurity removal method for quartz sand, it's essential to consider factors such as the types of impurities present in the ore, the desired purity requirements, and other relevant factors. Typically, a combination of various techniques is used to achieve impurity removal, and preliminary ore testing is recommended to determine the most suitable method for purifying quartz sand.
