During the lithium extraction process from ores such as spodumene and lepidolite, lithium precipitation mother liquor is often regarded as “waste liquid” or a low-value by-product. However, hidden in this seemingly ordinary alkaline mother liquor are two rare alkali metals whose value is far higher than lithium itself—rubidium (Rb) and cesium (Cs).

With the rapid growth of demand for lithium resources driven by the new energy industry, the volume of lithium precipitation mother liquor generated has also increased significantly. How to efficiently and economically extract rubidium and cesium from lithium precipitation mother liquor has become a key challenge for lithium extraction enterprises worldwide to extend their value chains. As a core equipment of liquid-liquid extraction and separation, the CWL-M series centrifugal extractor developed by Zhengzhou Tiei Extraction Technology Co., Ltd. is providing an efficient and reliable industrial solution for this highly challenging separation application.

Solvent Extraction: The Only Industrially Feasible Route for Rubidium and Cesium Recovery

Among various separation technologies, solvent extraction is currently the only proven technology capable of achieving efficient and selective recovery of rubidium and cesium from lithium precipitation mother liquor on an industrial scale.

The core principle is to utilize the highly selective complexation ability of specific extractants (such as t-BAMBP, 4-tert-butyl-2-(α-methylbenzyl)phenol, etc.) toward rubidium and cesium ions under alkaline conditions. The target ions are transferred from the aqueous phase into the organic phase, and then stripped by acid washing to obtain enriched rubidium and cesium solutions. Finally, rubidium salts or cesium salts are produced through evaporation and crystallization.

However, the solvent extraction process for rubidium and cesium recovery from lithium precipitation mother liquor faces several practical challenges:

1.The organic-to-aqueous phase ratio is relatively low, requiring the equipment to maintain high mass transfer efficiency under low phase ratio conditions.
2.The density difference between the two phases is small, making phase separation difficult for traditional gravity settling extraction equipment (such as mixer settlers), with a risk of third-phase formation.
3.Fluctuating alkalinity and suspended solids impose high requirements on equipment materials and operational stability.
4.The process usually requires 6–12 stages of counter-current extraction, washing, and stripping, making equipment footprint and energy consumption important considerations.

CWL-M Centrifugal Extractor: A “High-Efficiency Separator” Specifically Designed for Rubidium and Cesium Extraction

To address these challenges, the CWL-M series centrifugal extractor independently developed by Zhengzhou Tiei Extraction Technology Co., Ltd. has become a key piece of equipment in rubidium and cesium solvent extraction processes, thanks to its unique structural design and outstanding separation performance.

Working Principle

The CWL-M centrifugal extractor utilizes the strong centrifugal field generated by a high-speed rotating drum to complete the mixing, mass transfer, and separation of two immiscible liquids with different densities (aqueous phase and organic phase) within a very short time. The two phases enter the mixing zone through the feed inlet. Under the action of the turbine disc and impeller, the liquids are fully dispersed into fine droplets, allowing efficient transfer of solutes between the two phases. The mixed liquid then enters the separation zone of the rotating drum, where the centrifugal force rapidly separates it into a clear light phase (organic phase) and heavy phase (aqueous phase), which are discharged separately through their respective collection chambers.

Key Advantages of CWL-M Centrifugal Extractor

1.Highly Efficient Mass Transfer Under Extremely Low Phase Ratios
Rubidium and cesium extraction processes usually require the organic-to-aqueous phase ratio to be controlled below 1:3 or even 1:5. Under such low phase ratio conditions, traditional mixer settlers struggle to achieve sufficient mixing. The CWL-M centrifugal extractor adopts a forced vortex mixing mechanism, ensuring extremely high mass transfer efficiency even under low phase ratio conditions. The single-stage extraction efficiency can consistently exceed 95%.

2.Phase Separation Speed Increased by Dozens of Times
Benefiting from the centrifugal field, the phase separation time is reduced from dozens of minutes in gravity settling to only a few seconds. The separation performance is also less affected by small density differences between the two phases. This feature enables the CWL-M centrifugal extractor to easily handle difficult-to-separate systems such as lithium precipitation mother liquor, effectively preventing emulsification and third-phase entrainment.

3.Fully Enclosed System Suitable for Strongly Alkaline Conditions
The equipment adopts a fully enclosed structure, effectively preventing organic phase volatilization and odor release while improving the working environment. Meanwhile, wetted components can be manufactured using high-quality stainless steel materials (such as 316L and 2205 duplex stainless steel) or special alloys, providing excellent corrosion resistance against strongly alkaline mother liquor with pH >13 and various extractant systems.

4.High Stage Efficiency with Only 1/5 of the Footprint of Traditional Processes
In multi-stage counter-current rubidium and cesium extraction processes, the single-stage efficiency of the CWL-M centrifugal extractor can reach 90%–98%, reducing the number of required stages under the same separation requirements. With its compact structure, the complete extraction-washing-stripping production line requires significantly less space compared with mixer-settler solutions, making it highly suitable for upgrading and retrofitting existing lithium extraction plants.

5.Stable Operation and Easy Maintenance
The CWL-M centrifugal extractor adopts a vertical structure with bottom feeding and top discharge. The rotating drum is directly driven by an upper-mounted motor without complicated transmission mechanisms. Bearings and sealing components are designed for long service life, with continuous operating cycles exceeding 8,000 hours. Routine maintenance only requires regular inspection of lubrication and sealing conditions, significantly reducing operation and maintenance costs.

Rubidium and Cesium Extraction Process Flow

In industrial applications for recovering rubidium and cesium from lithium precipitation mother liquor, CWL-M centrifugal extractors are typically operated in multi-stage counter-current configurations. The standard process consists of three sections:

Extraction Section (4–6 stages): Lithium precipitation mother liquor (aqueous phase) contacts the organic phase containing extractant in counter-current flow. Rubidium and cesium ions are selectively extracted into the organic phase, while the raffinate (rubidium- and cesium-depleted mother liquor) is returned to the main process or discharged.

Washing Section (1–2 stages): The loaded organic phase is washed with dilute alkaline solution to remove co-extracted impurity ions such as potassium and sodium.

Stripping Section (3–4 stages): Dilute acid (such as hydrochloric acid or nitric acid) is used for stripping. Rubidium and cesium ions transfer from the organic phase into the aqueous phase, producing a high-concentration rubidium and cesium enriched solution. The regenerated organic phase is recycled for reuse.

This process route has been successfully industrialized in several lithium extraction projects. The comprehensive recovery rate of rubidium can reach 85%–92%, while cesium recovery can reach 80%–88%. After further impurity removal, concentration, and precipitation, the enriched solution can be used to produce high-purity rubidium salts and cesium salts.

Zhengzhou Tiei Extraction Technology Co., Ltd. has been deeply engaged in liquid-liquid extraction and separation technology for more than ten years. The company possesses comprehensive service capabilities covering extraction process development, centrifugal extractor manufacturing, and complete process automation control system integration. The CWL-M series centrifugal extractor has been widely applied in hydrometallurgy, chemical engineering, pharmaceutical industries, environmental protection and water treatment, and other fields.

If you are focusing on the recovery and utilization of rubidium and cesium resources from lithium precipitation mother liquor, or looking to improve the operating efficiency of your existing extraction section, please contact the Zhengzhou Tiei Extraction technical team. We will provide customized separation solutions tailored to your specific requirements.
Email: sales@tieiextraction.com
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