Quartzite Ore Purification Methods

Currently, conventional quartzite ore purification mainly relies on hand sorting/color sorting, gravity separation, magnetic separation, flotation, and wet leaching. Other processes are difficult to apply to conventional quartz product production due to their high cost.

Hand sorting/color sorting is the fundamental method of quartz purification and is usually carried out before grinding. Color sorting allows for preliminary classification of quartz ore, enabling rational resource utilization, preventing low-quality ore from being mixed into high-grade quartz sand processing, and separating stubborn black and yellow impurities, laying the foundation for subsequent purification processes.

Gravity separation, magnetic separation, and flotation are the core processes for quartzite ore purification. Gravity separation is less commonly used, only achieving simple and efficient separation when there is a significant weight difference between quartz and gangue minerals. Magnetic separation, especially high-intensity magnetic separation, is the main purification method, effectively separating weakly magnetic gangue minerals such as hematite and epidote. In actual production, it is often used in conjunction with flotation, resulting in significant purification effects.

Flotation can separate most gangue minerals that are difficult to remove by gravity separation and magnetic separation, such as feldspar and mica. Currently, reverse flotation is the main method, while direct flotation is difficult to implement on a large industrial scale due to its low yield. Reverse flotation is divided into the separation of quartz from mica and feldspar, depending on the gangue type. For the former, dodecylamine is used as a collector, and the effect is best under acidic conditions; for the latter, there are three main methods: hydrofluoric acid + cationic collector, strong acid + polyamine, etc.

Wet leaching utilizes the difference in chemical properties between quartz and gangue minerals to achieve purification. Quartz is chemically stable and only soluble in hydrofluoric acid, while most gangue minerals can be dissolved by acids. Alkaline solutions can also expose impurities through slightly soluble quartz. Leaching is divided into atmospheric pressure and high pressure leaching. High pressure leaching is expensive and is only used for the purification of high-purity quartz sand. Conventional quartz sand uses atmospheric pressure leaching, with hydrochloric acid as the main leaching agent. When the purification effect is not good, hydrofluoric acid can be added for mixed leaching to improve the purification effect.