Cobalt-Magnesium Separation via pH-Adjusted Washing
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Solution Overview
Problem
Current liquid-liquid extraction methods struggle to effectively separate magnesium from nickel, limiting the nickel-magnesium mass ratio in feed solutions to 500, which restricts the use of magnesium-containing raw materials and bulk supplies in nickel refining processes.
Innovation Solution
A method involving liquid-liquid extraction with a cation-exchange mechanism, using bis(2,4,4-trimethylpentyl)phosphinic acid as the extraction reagent, is employed to separate cobalt, magnesium, and nickel through multiple stages of extraction, washing, and back-extraction, allowing for the isolation of magnesium from nickel and cobalt, even at low nickel-magnesium mass ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional liquid-liquid extraction methods are used to separate cobalt and nickel, then cobalt extraction efficiency is improved, but magnesium co-extraction increases and cannot be effectively separated from nickel
Solution Approach 1:
The extraction process is divided into multiple sequential stages: first extracting cobalt at pH 5-6, then washing the organic phase with acidic solution at pH 2-3 to remove co-extracted magnesium, and finally back-extracting cobalt. This segmentation allows cobalt to be extracted efficiently while magnesium is removed in the washing stage, achieving both high cobalt recovery and magnesium separation.
Solution Approach 2:
The patent utilizes pH parameter changes to control metal extraction and separation. By adjusting pH from 5-6 during cobalt extraction to 2-3 during the washing stage, the patent selectively controls which metals are extracted or remain in the organic phase, enabling effective separation of cobalt from magnesium while maintaining high cobalt extraction efficiency.
2Manufacturing precision
If the nickel-magnesium mass ratio in feed solution is increased to improve nickel product quality, then magnesium contamination in nickel product is reduced, but the use of magnesium-containing raw materials is restricted
Solution Approach 1:
The patent extracts magnesium from the organic phase during the washing stage using acidic aqueous solution. This removes magnesium that would otherwise contaminate the nickel product, allowing high-purity nickel production even when processing magnesium-containing raw materials with low Ni/Mg ratios.
Solution Approach 2:
By changing the pH parameter to 2-3 during the washing stage, the patent creates conditions where magnesium is preferentially retained in or removed from the organic phase while nickel remains pure in the aqueous phase. This enables effective magnesium removal regardless of the initial Ni/Mg ratio in the feed solution.
3Device complexity
If magnesium is allowed to co-extract with cobalt into the organic phase to simplify the process, then process complexity is reduced, but magnesium contamination in the cobalt product increases
Solution Approach 1:
The patent segments the extraction process into cobalt extraction, washing, and back-extraction stages. The washing stage specifically targets magnesium removal from the organic phase before cobalt back-extraction, ensuring high cobalt product purity while maintaining a relatively simple overall process flow.
Solution Approach 2:
The washing solution acts as an intermediary that selectively interacts with magnesium in the organic phase without significantly affecting cobalt. This intermediary step removes magnesium contamination while preserving cobalt in the organic phase for subsequent back-extraction, achieving high product purity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the separation of magnesium from nickel and cobalt, achieving nickel-magnesium mass ratios higher than 500, cobalt-magnesium mass ratios higher than 1000, and magnesium-nickel mass ratios higher than 10, thereby enabling the use of magnesium-bearing materials in nickel product manufacturing.
Implementation Method 1
liquid-liquid extraction with a cation-exchange mechanism
Implementation Method 2
liquid-liquid extraction with a cation-exchange mechanism
Data Source
Figure 1
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AI summary
A method of separating cobalt and magnesium from a nickel-bearing extraction feed solution (1) with liquid-liquid extraction, wherein a first extraction solution (2) contains cation-exchange extraction reagent insoluble or poorly soluble in said feed solution (1). The method comprises at least the following method stages enabling cobalt, magnesium and nickel to be separated into discrete aqueous solution streams: - in an extraction stage (A), the cobalt-, magnesium- and nickel-containing extraction feed solution (1) is extracted with the first extraction solution (2) for providing a cobalt-, magnesium- and nickel-loaded second extraction solution (4) and a primarily nickel-containing raffinate (3), - in a washing stage (B), the cobalt-, magnesium- and nickel-loaded second extraction solution (4) is washed in a countercurrent fashion with a primarily cobalt- and sulfuric acid-containing first washing solution (5) whose pH is 0,5-5 for providing a primarily cobalt- and magnesium-loaded third extraction solution (7) and a primarily nickel-containing first wash water (6), - in a washing stage (C), the primarily cobalt- and magnesium-loaded third extraction solution (7) is washed in a countercurrent fashion with a water-, cobalt-and sulfuric acid-containing second washing solution (8) whose pH is 0,5-5 for providing a primarily cobalt-loaded fourth extraction solution (10) and a primarily magnesium-containing second wash water (9).