Purification of high purity quartz sand

As one of the important industrial raw materials, quartz can be widely used in glass, building materials, plastics, electronic materials and other industries. Among them, the fields of electronic technology, aerospace, optical fiber communication and military industry have higher requirements on the purity of quartz sand. 

In industrial production, ordinary quartz sand is usually pretreated first, and then purified into high-purity quartz sand. The purification methods mainly include physical purification, chemical purification and biological purification.

1. Physical purification of high-purity quartz sand

The common physical purification methods of high-purity quartz sand can include water washing-classification desliming, scrubbing, gravity separation, magnetic separation and flotation, etc. Through one or more combination forms, the impurity minerals in the quartz sand are removed to meet the purification requirements.

(1) Water washing - graded desliming/scrubbing

In the beneficiation process of quartz sand, the particle size less than 0.1mm is usually called slime. As its particle size becomes finer, the grade of silica will be lower and lower, and the impurity ore will be relatively more. Therefore, impurity minerals can be removed and the grade of quartz concentrate can be improved by water washing-grading desliming or scrubbing.

(2) Gravity separation

The main use of the relative density, particle size, and shape differences between the particles of the minerals is to cause them to produce different speeds of movement and distribute in different directions under the action of water and centrifugal force to separate the minerals.

(3) Magnetic separation

Mainly use the magnetic separation difference between quartz and impurity ores to remove hematite, limonite, biotite and other magnetic minerals in the minerals to the greatest extent through magnetic separation equipment.

(4) Flotation

Use reagents and flotation equipment to change the difference in surface properties between minerals. Select high-purity quartz sand from other places under acidic conditions to remove fine-grained hematite, biotite, garnet and aluminum minerals in the minerals. 

2. Chemical purification of high purity quartz sand

The chemical purification methods of high-purity quartz sand mainly include acid leaching and alkali leaching, and the purification effect of high-purity quartz sand is better.

(1) Pickling

Commonly used acids are mainly sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid and so on. When the acid is relatively dilute, it has a better effect on removing impurities such as iron, aluminum, and magnesium. When the acid is relatively concentrated, it has a good effect on removing impurities such as titanium and chromium.

(2) Alkaline leaching

Alkaline solutions such as sodium hydroxide or sodium carbonate are commonly used to dissolve aluminum-containing silicate impurity minerals to achieve the purpose of purifying quartz sand.

3. High-purity quartz sand biological purification

The biological purification method of high-purity quartz sand mainly adopts microbial leaching purification. Utilizing the physiological functions of microorganisms and their metabolites, through oxidation, dissolution and decomposition, the impurities on the surface of the quartz sand are separated from the quartz matrix to achieve the purification of the quartz sand.