Salar brine is rich in a variety of valuable minerals, among which boron is an important resource. At present, the methods for extracting boron from salar brine include precipitation, adsorption, ion exchange and extraction. Each method has its own characteristics and scope of application, but the extraction method has become the preferred method for extracting boron due to its advantages such as short process flow, low production cost and no three wastes.

The basic principle of extracting boron by extraction method

The extraction method is to generate boric acid esters by esterification reaction between boric acid and hydroxyl functional groups. Boric acid esters are insoluble in water, but can be miscible with organic solvents such as kerosene, thereby achieving the purpose of extracting and separating boron. This method is suitable for brine with a boric acid mass concentration in the range of 2 g/L to 18 g/L.

Four different methods for extracting boron from salar brine

Precipitation method

  • Advantages: simple process flow, small equipment investment, easy operation.
  • Disadvantages: only can remove 50% to 60% of the boron in the solution, suitable for brine with high boron content.

Adsorption method

  • Advantages: The process is relatively mature and the adsorption capacity is high.
  • Disadvantages: The process is complex, the production cost is high, the regeneration time is long, and the adsorption capacity will decrease after long-term use.

Ion exchange method

  • Advantages: The recovery rate of boron can reach more than 90%, which is suitable for the extraction of low-concentration boron.
  • Disadvantages: The boric acid content in the eluent is low, the evaporation volume is large when the eluent is processed, and a large amount of resin will be consumed during repeated elution and regeneration.

Extraction method

  • Advantages: short process flow, low production cost, no three wastes, suitable for brine of different concentrations.
  • Disadvantages: need to select appropriate extraction agent and process conditions.

Boron Extraction Equipment From Salar Brine

According to the working principle and mechanical structure of the extraction equipment, it is mainly divided into three types: centrifugal extractor, mixer settler and extraction column.

Centrifugal Extractor

  • Features: A new generation of fast and efficient liquid-liquid extraction and separation equipment. It accelerates stratification with the help of centrifugal force generated by high-speed rotation to complete the separation of liquid-liquid phases with different specific gravity.
  • Advantages: It can quickly establish phase equilibrium, easily realize single-stage or multi-stage series countercurrent or cross-current extraction, has high extraction efficiency, small machine volume, low consumption of extractant or detergent, and saves solvent investment costs.
  • Application: It has been proved through the practice of the CWL-M centrifugal extractor that under the best process conditions, after five-stage extraction and four-stage stripping, the extraction rate and stripping rate are both above 97%.

Mixer Settler

  • Structure: It is mainly composed of a mixing chamber and a clarification chamber. The liquid feed and the solvent are fully contacted and transferred in the mixing chamber through stirring, and then enter the clarification chamber to complete mass transfer and phase separation under the action of gravity.
  • Advantages: strong adaptability, simple scale-up, and strong operability.
  • Disadvantages: large liquid feed retention, large floor space, and easy contamination of materials.

Extraction Column

  • Types: Mainly divided into packed column and screen plate column, mass transfer separation and phase separation are completed at different positions of the column.
  • Advantages: Suitable for large-scale production.
  • Disadvantages: Low mass transfer efficiency, severe backmixing, and large scale limit its application.

The centrifugal extractor has obvious advantages in extracting boron from salar brine. The use of centrifugal extractors is conducive to the mechanization and industrialization of extraction equipment and the realization of automatic control. The centrifugal extractor provides reliable technical support for the industrialization of boron extraction from brine.
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