Solvent Extraction for Nickel Cobalt Calcium Separation
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Solution Overview
Problem
Current methods for producing nickel sulfate and cobalt sulfate solutions from sulfuric acid solutions containing nickel, cobalt, and calcium are inefficient, leading to high production costs and impurity issues, particularly with calcium, which degrades battery characteristics in lithium ion batteries.
Innovation Solution
A method involving solvent extraction under specific conditions to separate calcium from nickel and cobalt, using alkylphosphonate esters as extractants, to produce high-purity nickel sulfate and a mixed solution of nickel and cobalt sulfates, allowing for efficient recovery of valuable metals and reduction of impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nickel sulfate containing cobalt and calcium is used as raw material for producing positive electrode materials, then production cost is reduced by avoiding separation processes, but battery characteristics are degraded due to calcium impurities in the electrode
Solution Approach 1:
The patent applies solvent extraction to selectively remove calcium from the nickel sulfate solution while retaining nickel and cobalt. By using specific extractants under controlled pH conditions, calcium is extracted into the organic phase and separated from the aqueous phase containing nickel and cobalt, thus eliminating the harmful impurity while preserving the valuable metals
Solution Approach 2:
The patent utilizes pH parameter control to achieve selective extraction. By adjusting the pH of the sulfuric acid solution to specific ranges (pH 1.5-3.5 for calcium extraction, pH 4.0-5.5 for cobalt extraction), the solubility and extraction behavior of different metal ions are changed, enabling selective separation based on their different chemical properties at different pH levels
2Manufacturing precision
If conventional precipitation methods are used to remove calcium, then calcium removal is attempted, but nickel and cobalt are co-precipitated at high pH conditions, reducing metal recovery efficiency
Solution Approach 1:
The patent introduces an organic solvent extractant as an intermediary substance to facilitate selective calcium removal. The extractant acts as a mediator that selectively binds calcium ions in the organic phase, allowing calcium separation without requiring high pH conditions that would cause co-precipitation of nickel and cobalt, thus maintaining high metal recovery rates
Solution Approach 2:
The patent replaces the conventional precipitation mechanism (which relies on pH adjustment and insoluble salt formation) with a solvent extraction mechanism. This substitution allows calcium removal through selective partitioning between organic and aqueous phases based on solubility differences, avoiding the co-precipitation problem inherent in precipitation methods
3Manufacturing precision
If solvent extraction is performed at high pH to remove calcium effectively, then calcium removal efficiency is improved, but cobalt is also extracted, increasing production complexity and reducing nickel sulfate purity
Solution Approach 1:
The patent divides the extraction process into distinct stages with different pH conditions: first stage at pH 1.5-3.5 for selective calcium extraction, and second stage at pH 4.0-5.5 for cobalt extraction if needed. This segmentation allows each extraction step to target specific metals, simplifying the overall process by avoiding the need for a single complex high-pH extraction step that would extract all metals
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 efficient production of high-purity nickel sulfate and a mixed solution of nickel and cobalt sulfates, reducing production costs and improving battery performance by effectively removing calcium impurities, thus enhancing the recovery rates of nickel and cobalt.
Implementation Method 1
A method involving solvent extraction under specific conditions to separate calcium from nickel and cobalt, using alkylphosphonate esters as extractants
Data Source
Figure 1
AI summary
Provided is a method for producing solutions, by which two solutions, namely a high-purity nickel sulfate solution and a mixed solution of nickel sulfate and cobalt sulfate are able to be obtained at the same time from a sulfuric acid solution containing nickel, cobalt and calcium. A method for producing solutions according to the present invention uses a sulfuric acid solution containing nickel, cobalt and calcium and performs a first step S1 for producing a mixed solution of nickel sulfate and cobalt sulfate from the sulfuric acid solution and a second step S2 for producing a solution of nickel sulfate from the sulfuric acid solution in parallel. In the first step, the sulfuric acid solution is subjected to solvent extraction by means of an extractant, thereby obtaining a first organic solvent after extraction containing calcium and a first extraction residue containing nickel and cobalt. In the second step, the sulfuric acid solution is subjected to solvent extraction by means of an extractant, thereby obtaining a second organic solvent after extraction containing cobalt and calcium and a second extraction residue containing nickel.