Hafnium (Hf), a silver-grey transition metal, plays an irreplaceable role in the nuclear industry, high-temperature materials and microelectronics due to its unique physical and chemical properties. The chemical properties of hafnium and zirconium (Zr) are highly similar, which makes their separation a major challenge. In nature, hafnium almost never exists alone, but coexists with zirconium in an isomorphic form, with a zirconium-hafnium mass ratio of about 50:1. Although traditional separation methods such as fractional crystallization and molten salt distillation can achieve a certain degree of separation, these methods are usually time-consuming, energy-intensive and cause serious environmental pollution. Therefore, centrifugal extraction technology has gradually become the mainstream solution for industrial separation of zirconium and hafnium due to its high efficiency, environmental protection and adaptability.

Principle of Centrifugal Extraction Technology

The centrifugal extractor uses the centrifugal force generated by high-speed rotation to accelerate the mixing and stratification of the two phases (aqueous phase and organic phase), thereby achieving the selective separation of zirconium and hafnium. Specifically, the centrifugal extractor completes this process through the following steps:

  1. Efficient mass transfer: The centrifugal force generated by high-speed rotation allows the two phases of liquid to mix quickly and fully contact, greatly shortening the single-stage extraction time to seconds.
  2. Rapid phase separation: The two phases of liquid after mixing are quickly separated under the action of centrifugal force, forming a clear interface, which is convenient for subsequent operations.
  3. Selective separation: By selecting appropriate extractants and stripping agents, the selective separation of target substances (such as hafnium) can be achieved.

Zirconium and Hafnium Extraction Process

Taking the tributyl phosphate (TBP)-nitric acid (HNO₃) system as an example, the typical process flow of zirconium and hafnium separation can be divided into three stages:

  1. Countercurrent extraction: The nitric acid solution containing zirconium and hafnium is countercurrently contacted with tributyl phosphate (TBP), and zirconium preferentially complexes with TBP and enters the organic phase, while hafnium is enriched in the aqueous phase.
  2. Washing and purification: The organic phase loaded with zirconium is washed with dilute acid to remove trace amounts of hafnium carried over, thereby further improving the purity of zirconium.
  3. Stripping: The zirconium in the organic phase is stripped with hydrochloric acid to obtain nuclear-grade zirconium dioxide; the hafnium in the aqueous phase is precipitated and calcined to obtain high-purity hafnium oxide.

Advantages of Centrifugal Extractor

Compared with the traditional mixer settler extraction technology, the CWL series centrifugal extractor has the following significant advantages:

  1. High efficiency: The single-stage extraction time is shortened to seconds, and the stage efficiency is increased by more than 50%, which greatly improves production efficiency.
  2. Environmental protection: The solvent recycling rate is as high as 90%, and the wastewater discharge is reduced by 60%, which reduces environmental pollution.
  3. Adaptability: It can handle strong acid (such as nitric acid, hydrochloric acid) systems, is compatible with a variety of extractants (such as TBP, MIBK), and is suitable for various complex working conditions.
  4. Economical: Save labor costs, detergents and extractants can be recycled, the processing volume is large, the footprint is small, and the unit cost is low.
  5. Structural optimization: The equipment adopts an upper suspension structure, without bottom bearings and mechanical seals, with high speed and stability, easy maintenance and long service life.

Zhengzhou Tiei Extraction Company's CWL series centrifugal extractor has high separation factors and strong stability, and are particularly suitable for handling strong acids, strong alkalis and highly corrosive occasions. The equipment can be made of fully anti-corrosion reinforced materials to meet a variety of extraction needs. The following are its main application features:

  1. Multi-stage series flow/cross-flow extraction: multi-stage series flow or cross-flow extraction can be realized to meet different process requirements.
  2. Intelligent control: Equipped with advanced automatic control systems, it supports single-stage multi-stage series countercurrent or cross-current washing and extraction stripping to improve the separation rate.
  3. Environmentally friendly design: fully enclosed structure, unmanned operation, meeting the application environment and GMP specifications of explosion-proof and toxic, harmful and volatile media.

The application of CWL series centrifugal extractors not only solves the technical problem of zirconium and hafnium separation, but also provides more efficient and environmentally friendly solutions for related industries, promoting the rapid development of the new materials field.
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