Reasons for Poor Iron Removal in Quartz Sand

As an important industrial raw material in many industries such as glass, ceramics, and electronics, the purity of quartz sand directly determines the quality of the end product. In the process of quartz sand purification, iron removal is a crucial link. However, in actual industrial production, we often face the dilemma of unsatisfactory iron removal effect, which not only affects product quality, but also increases production costs. So what are the reasons for the quartz sand  iron removal poor effect ? Let's find out together!

The following analyzes the reasons for the poor iron removal effect of quartz sand from multiple dimensions such as raw material characteristics, process technology, equipment conditions, and operation management.

011. Reasons for the characteristics of quartz sand raw materials

The iron occurrence state is complex: the iron element in quartz sand exists in various forms, which brings great challenges to iron removal. Encapsulated iron refers to iron minerals tightly encapsulated by quartz crystals, such as structural iron in mica. This type of iron mineral is tightly encapsulated by quartz crystals, and conventional beneficiation methods are difficult to effectively separate it; adsorbed iron is adsorbed on the surface of quartz particles in the form of Fe³⁺, and its binding force is relatively weak, but due to its wide distribution, it is difficult to completely remove it; solid solution iron is iron atoms replacing silicon into the lattice. This form of iron is tightly bound to the quartz crystal structure and is the most difficult state of iron to remove. Conventional physical and chemical methods are difficult to separate it from the lattice.

Mineral symbiosis characteristics: Quartz sand often coexists closely with a variety of iron-containing minerals, such as hematite and limonite. These iron-containing minerals have similar physical and chemical properties to quartz sand, and it is difficult to achieve efficient separation during the beneficiation process. In addition, weathering products in quartz sand, such as clay minerals, carry colloidal iron impurities. These colloidal iron impurities are small particles with strong adsorption and are easily attached to the surface of quartz sand, further increasing the difficulty of iron removal.

022. Technical factors of quartz sand beneficiation

Defects in crushing and grinding: Crushing and grinding is an important early stage of quartz sand beneficiation, and its effect directly affects the subsequent iron removal efficiency. If the particle size is not properly controlled, the iron minerals will not be fully exposed, making it impossible for subsequent magnetic separation, flotation and other processes to effectively capture iron minerals, thereby reducing the iron removal effect. Excessive crushing will produce a large number of new surfaces, which are highly active and easily adsorb iron ions and other impurities in the air, causing secondary adsorption of iron and increasing the difficulty of iron removal.

Limitations of separation process: For example, in the magnetic separation process, the selection of magnetic separation intensity is very important. Weak magnetic separation is difficult to remove weak magnetic minerals, and it is impossible to effectively separate iron minerals with different magnetic properties, resulting in some weak magnetic iron minerals remaining, affecting the iron removal effect; in addition, improper selection or use of chemical agents in quartz sand flotation will also lead to the inability to effectively separate quartz sand and iron minerals, which not only reduces the iron removal efficiency, but also may introduce new impurities.

Problems in pickling process: Pickling is an important means to remove iron impurities in quartz sand, but there are many problems in actual operation. When the acid concentration is insufficient, for example, when the hydrochloric acid concentration is less than 5%, the reaction rate between the acid and the iron mineral will drop significantly, the dissolution efficiency will drop sharply, and the iron impurities cannot be effectively removed. In addition, a single acid cannot handle iron in various forms, and the failure to use a composite acid system will result in incomplete iron removal. At the same time, temperature control during pickling is also very critical. When the temperature is lower than 60°C, the kinetics of the chemical reaction is slow, the reaction time is prolonged, and the iron removal effect will also be affected.

033. Quartz sand beneficiation equipment factors

Improper selection of magnetic separation equipment: Different types of magnetic separation equipment are suitable for iron minerals of different particle sizes and magnetic properties. If the magnetic separation equipment is not properly selected, it will also affect the iron removal effect of quartz sand. Among them, the permanent magnetic drum magnetic separator is limited by the magnetic field strength and mode of action, and the treatment effect of fine-grained (<0.1mm) iron minerals is poor; the removal rate of fine-grained iron by the high-gradient magnetic separator can exceed 90%.

Reaction equipment defects: In chemical reactions such as pickling, the performance of the reaction equipment is very important. If the pickling tank does not have a stirring device, the acid and quartz sand will be mixed unevenly, the mass transfer efficiency will be poor, and the iron impurities in some areas will not be able to fully react with the acid, thus affecting the iron removal effect. In addition, if the acid-resistant material of the reaction equipment is corroded, impurities such as iron ions will be released, causing secondary pollution, and the iron content in the quartz sand will increase instead of decrease.

044. Quartz sand beneficiation operation management factors

Improper process control: In the entire process of quartz sand iron removal, the connection and control of each link are very critical. If the water washing is not sufficient, the residual flotation reagent will affect the subsequent magnetic separation, pickling and other treatment processes, and reduce the iron removal efficiency. During the magnetic separation process, the fluctuation of the feed concentration will also have a significant impact on the iron removal effect. The feed concentration range of magnetic separation is 25-35% solid content. Exceeding this range will lead to unstable magnetic separation effect and incomplete removal of iron impurities.

Water quality influence: The quality of flushing water has a direct impact on the quartz sand iron removal effect. If the rinsing water contains high iron content (>0.3mg/L), iron ions will be brought into the quartz sand during the rinsing process, causing pollution. In addition, if deionized water is not used for the final rinse, other impurity ions in the water may also be adsorbed on the surface of the quartz sand, affecting the purity of the quartz sand and resulting in unsatisfactory iron removal.

The above introduces the factors affecting the iron removal efficiency of quartz sand from four dimensions. In addition to external factors, technology is the main influencing factor. Therefore, choosing good technical processes and reasonable mineral processing equipment is the key. Xinhai Mining has rich experience in quartz sand purification, iron removal and impurity removal, and has participated in quartz sand mineral processing projects many times. From mineral processing tests, mineral processing process design, mineral processing equipment production and later operation management of the total engineering project, it has provided good technology to achieve high recovery rate. If you have quartz sand mineral processing or transformation projects, please consult Xinhai Mining.