Application of Mixer-Settlers in Nickel-Cobalt Extraction Processes

With the explosive growth of the new energy industry, nickel and cobalt, as core strategic metals for lithium battery cathode materials, their efficient separation and purification have become a key technical bottleneck in the hydrometallurgy field. Currently, the industry generally faces pain points such as low processing efficiency of low-grade ores and waste battery slurries, insufficient nickel-cobalt separation accuracy, low metal recovery rates, and overlapping environmental protection and cost pressures. Traditional extraction equipment can hardly adapt to complex working conditions and high-purity product requirements. Mixer-settlers, with their advantages of stable structure, strong adaptability, controllable separation, and low large-scale cost, have become the core equipment in nickel-cobalt extraction processes. Through multi-stage countercurrent extraction, precise interphase regulation and system optimization, they effectively solve separation problems, improve resource utilization and product purity, and serve as a key support for promoting the green and efficient upgrading of nickel-cobalt hydrometallurgy.

1. Core Characteristics of Mixer-Settlers for Nickel-Cobalt Separation

Based on the core principle of liquid-liquid extraction interphase mass transfer, mixer-settlers rely on a standardized "mixing-mass transfer-phase separation" process, which is consistent with the process requirements of nickel and cobalt ions with similar chemical properties that require selective separation. Their mixing chambers achieve full contact between organic and aqueous phases, promoting the directional migration of nickel and cobalt ions to the organic phase; the clarification chambers realize rapid phase separation by gravity, reducing the risk of metal entrainment and emulsification, and the single-stage separation efficiency is stable and controllable.

Compared with equipment such as extraction towers and centrifugal extractors, mixer-settlers have stronger adaptability to working conditions. They can handle nickel-cobalt slurries with high viscosity, high impurities, and low concentration, and can operate stably without complex pretreatment. The modular multi-stage series design can flexibly combine extraction sections, washing sections, and stripping sections, adapting to mainstream extraction systems such as P204, P507, and C272, and realizing step-by-step separation of nickel and cobalt from impurities such as iron, aluminum, manganese, calcium, and magnesium. At the same time, the equipment has no high-speed rotating parts, ensuring strong operational stability and low maintenance costs. The extractant can be recycled, greatly reducing reagent consumption and hazardous waste output, and balancing economy and environmental protection.

2. Core Application of Mixer-Settlers in Primary Nickel-Cobalt Ore Extraction

In the hydrometallurgical treatment of primary nickel-cobalt ores (laterite nickel ores, sulfide nickel ores), mixer-settlers undertake the core functions of nickel-cobalt enrichment, separation, and impurity removal, especially suitable for the treatment of low-grade ore slurries. Laterite nickel ore leachate has low nickel grade, scarce cobalt content, and complex impurity components. The traditional process has a long separation process and serious metal loss. Through 3-10 stages of countercurrent series, mixer-settlers initially separate nickel and cobalt from impurities such as iron and aluminum in the extraction section, deeply remove impurities entrained in the organic phase in the washing section, and obtain high-purity nickel-cobalt enriched liquid in the stripping section.

For high-magnesium and low-nickel-cobalt systems, mixer-settlers enhance the selectivity of the extractant by adjusting pH value, phase ratio, and stirring parameters, retaining magnesium ions in the aqueous phase, significantly improving the nickel-cobalt separation factor, and effectively solving the problem of high magnesium interference. After process optimization, the comprehensive recovery rate of nickel and cobalt can reach more than 95%, and the product purity meets battery-grade and metallurgical-grade standards, providing a reliable technical path for the efficient utilization of low-grade primary ores.

3. Practical Value of Mixer-Settlers in Nickel-Cobalt Recovery from Spent Lithium Batteries

Under the tide of power battery retirement, the recovery of nickel and cobalt from spent ternary batteries has become a key link in resource recycling. The slurry has complex components and coexisting multi-metals, making separation more difficult than that of primary ore systems. With the advantage of fractional extraction, mixer-settlers have become the core equipment in the battery recovery process, realizing efficient step-by-step separation of nickel, cobalt, manganese, and lithium.

In practical application, impurities such as manganese, iron, and aluminum are first separated in the mixer-settler using the P204 system, then cobalt is selectively extracted through the P507 system, while nickel and lithium remain in the aqueous phase for further separation. The multi-stage series design can accurately control the migration path of each metal ion, reducing cross-entrainment. The cobalt extraction rate can reach more than 99%, and the impurity content of nickel sulfate and cobalt sulfate products is reduced to below 10ppm, meeting the requirements of high-end battery material production. At the same time, mixer-settlers realize the recycling of wastewater and extractant, with a wastewater recycling rate of more than 99%, greatly reducing environmental treatment costs and conforming to the green and low-carbon development trend of lithium battery recycling.

4. Solutions of Mixer-Settlers to Pain Points in the Nickel-Cobalt Extraction Industry

Aiming at the core pain points of the industry, mixer-settlers provide systematic solutions from four dimensions: efficiency, purity, cost, and environmental protection. In terms of separation efficiency, multi-stage countercurrent and precise parameter regulation shorten the processing cycle, with a single-stage residence time controlled at 3-8 minutes, adapting to large-scale continuous production, and the annual processing capacity is several times higher than that of the traditional batch process.

In terms of purity improvement, through fractional impurity removal and deep washing, impurities such as calcium, magnesium, copper, and manganese are effectively removed, solving the problem of excessive mutual content of nickel and cobalt in the traditional process, and meeting the strict standards of battery-grade materials. In terms of cost control, the equipment investment and operation and maintenance costs are low, the extractant loss is reduced by more than 35%, and the metal loss rate is controlled within 1%, significantly improving the economic benefits of the project. In terms of environmental protection, gravity phase separation reduces emulsification and VOCs volatilization, and the output of hazardous waste is reduced by more than 60%, helping enterprises meet emission standards and achieve the "dual carbon" goal.

5. Technological Upgrading and Application Trends of Mixer-Settlers

With the increasing complexity of nickel-cobalt resources and the continuous improvement of product standards, mixer-settlers are upgrading towards high efficiency, intelligence, and greenization. In terms of structural optimization, large-volume clarification chambers, coalescing fillers, and anti-emulsification diversion designs further shorten the phase separation time and reduce entrainment loss. Material upgrading adopts anti-corrosion materials such as glass fiber reinforced plastic and PTFE lining, adapting to extreme working conditions such as strong acid and high salt, and extending the service life of the equipment.

In terms of intelligence, online monitoring and automatic control systems realize real-time closed-loop control of pH value, phase ratio, interface, and stirring speed, improving process stability and separation accuracy. In the future, mixer-settlers will be coupled with membrane separation, electroextraction and other technologies to build a more efficient integrated nickel-cobalt separation process, further improving the processing capacity of low-grade resources and complex waste materials, and providing solid guarantee for the safety and green sustainable development of the new energy industry chain.