How to remove film iron from quartz sand?

In the sand washing plant, due to the existence of film iron, the quartz sand treated by simply washing and gravity separation process can not meet the requirements of producing qualified quartz sand. Therefore, the removal of film iron is a common problem. The methods of removing film iron mainly include scrubbing, ultrasonic and pickling.

1.Scrubbing
Scrubbing is carried out in the attrition scrubber, which is completed by the friction between the quartz sand particles caused by the violent stirring of the blades in the attrition scrubber. This method can effectively remove the clay minerals and some loose oxides adhering to the sand surface. Because the film iron are thin and strong, it is unlikely that they will be removed completely by this method. If necessary, chemical reagents can be added in the attrition scrubber.

2.Ultrasonic washing
The principle of ultrasonic washing is to introduce ultrasonic into the pulp, which produces strong cavitation effect in the pulp. The cavitation effect produces strong mechanical force to peel off the impurities attached to the surface of quartz sand. The frequency of ultrasonic vibration and the residence time of materials in the ultrasonic action zone depend on the properties of surface impurities and their bonding strength with main minerals. Under the action of ultrasonic wave, the film iron and other impurities on the surface of quartz sand are dissociated and enter the liquid phase in the form of fine mud, which is removed by washing and dewatering.

3.Chemical treatment
Acid leaching and pickling are common chemical treatment methods, which can be divided into cold acid treatment and hot acid treatment. Under static conditions, the treatment by dissolving minerals with acid is called acid leaching. Scrubbing in acid medium is called pickling. Acid leaching takes quite a long time, especially cold acid dissolution.

4.Alkaline treatment
NaOH and Na2CO3 are commonly used alkaline reagents. Its principle is to transform insoluble valuable metals into soluble metal sodium salts, so as to achieve the purpose of quartz sand purification.
5.Chlorination method
Chlorine, sodium chloride and ammonium chloride are heated together with quartz sand to make iron in the sand become FeCl3 gas and volatilize, which can also achieve the purpose of iron removal.
6.Microbiological method
The results showed that Aspergillus niger could remove iron from quartz sand, but the treatment time was longer.
Various physical mechanical and chemical methods can be used alone or in combination to remove iron from quartz sand, and their efficiency largely depends on the properties of mineral raw materials.