Pay Attention to These Key Factors When Purifying Quartz ...

01

Chunlei exports high-quality products globally, with a focus on providing our customers with superior, high value-added products. Let's work together for a better future.

The influence of quartz sand scrubbing, classification, and desludging stages

Scrubbing and classification desludging are processes designed to remove impurity minerals such as film iron, bonding agents, and soil from the surface of quartz sand. This is achieved through mechanical forces and the abrasive interactions among sand particles. In addition, these processes involve the further rubbing of unformed mineral aggregates, leading to the enhanced purification of quartz sand through classification operations.

Factors influencing the effectiveness of scrubbing and desludging include:

• The particle size of the quartz sand
• The type and content of impurity minerals present in the original ore
• The structural characteristics of the scrubbing machine
• The duration of scrubbing
• The concentration during scrubbing

It has been observed that as the quartz particle size becomes finer, the grade of SiO2 decreases while the concentrations of iron and aluminum impurities increase, especially in quartz sand with substantial amounts of clay minerals. To remove film iron and adhesive impurities on the quartz surface, various equipment such as spiral scrubbers, drum screens, hydrocyclones, desludging buckets, and hydraulic classifiers are utilized. This equipment greatly improves the treatment effect.

Research indicates that an optimal scrubbing concentration is between 50% and 60%. Scrubbing duration should be adapted to meet product quality requirements in order to prevent excessive wear on equipment and increased energy consumption. For quartz sand that lacks ideal mechanical scrubbing effects, rod scrubbing is a proven solution.

02

Factors affecting the magnetic separation stage of quartz sand

The magnetic separation process of quartz sand focuses on eliminating magnetic impurity minerals like hematite and limonite, thereby reducing iron content, enhancing product quality, and increasing usable value. Factors influencing the efficiency of magnetic separation include:

• The number of magnetic separations
• The strength of the magnetic field
• The particle size of the quartz sand

As magnetic separations increase, iron content gradually diminishes. Most iron is removeable at a specific magnetic field intensity; however, beyond a certain point, increasing this intensity yields minimal improvement in iron removal rates. Additionally, fine-grained quartz sand often contains higher amounts of iron-containing impurity minerals, making finer quartz sand particles more effective in iron removal.

03

Factors affecting the quartz sand flotation stage

The flotation method targets the elimination of non-magnetic associated impurities, including feldspar and mica, from quartz sand. The purity of the raw ore, along with the choice and dosage of chemicals, heavily influence flotation effectiveness. During the fluorine flotation process, a combination of cationic collectors and hydrofluoric acid activators are used, effectively achieving notable flotation results. However, it also produces fluorine-containing wastewater that requires treatment before disposal.

An environmentally friendly approach is employed in fluorine-free flotation, which leverages structural differences between quartz and feldspar. This method combines anionic and cationic mixed collectors, utilizing their distinctive Zeta potentials to preferentially float feldspar, facilitating efficient separation. Post-scrubbing, desliming, magnetic separation, and flotation, the quartz sand purity can reach between 99.3% and 99.9%, meeting industrial sand requirements.

04

Factors affecting the acid leaching stage of quartz sand

Acid leaching enhances quartz sand purity by exploiting the fact that quartz is insoluble in acid (except HF), while many impurity minerals are soluble. The acid leaching effect is impacted by:

• The type of acid used
• The concentration of the acid
• Duration of acid leaching
• Temperature
• Stirring of the slurry

Different acids display varying efficiency in removing metal impurities. For instance, nitric acid alone exhibits a low iron removal rate; however, dibasic acid (a combination of hydrochloric acid and hydrofluoric acid) achieves a removal rate of 58.1%. Utilizing a ternary mixed acid can elevate the removal rate to 67.7%. The synergistic effect of using mixed acids significantly enhances impurity removal efficiency. Careful management of HF concentration—kept under 10%—is crucial to prevent quartz dissolution.

While dilute acids effectively remove Fe and Al, concentrated sulfuric acid, aqua regia, or HF effectively target Ti and Cr. Combined acids such as sulfuric acid, hydrochloric acid, nitric acid, and hydrofluoric acid for removal can drastically enhance quartz sand purity. Increasing temperature accelerates both the reaction rate and iron removal, though there is an observed diminishing effect at higher temperatures. Thus, efficient purification is best achieved at reduced acid concentration, lower temperatures, and minimized acid leaching durations.

Quartz sand beneficiation and purification represent a systematic project involving several stages: scrubbing, graded desludging, magnetic separation, flotation, and acid leaching. The success of each stage relies on multiple factors, including the original ore's nature, process parameters, equipment configuration, and reagent system. By considering these elements, purification processes can be optimized, significantly enhancing quartz sand purity to meet various industrial standards and improve the economic returns of beneficiation plants.