Cobalt Sulfate Solution pH Adjustment via Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing cobalt sulfate solutions struggle to achieve a pH of at least 4, which is crucial for reducing disruptive elements in lithium-ion batteries, and often result in solutions with high residual sulfuric acid content or contamination with sodium salts.
Innovation Solution
A two-step process involving the dissolution of metallic cobalt in aqueous sulfuric acid under a hydrogen or nitrogen/oxygen atmosphere, followed by treatment with oxygen or oxygen-containing gases to adjust the pH and minimize disruptive ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metallic cobalt is dissolved in sulfuric acid to produce cobalt sulfate solution, then cobalt sulfate can be obtained for further processing, but the solution has low pH (1.5-1.8) which makes purification difficult and allows disruptive elements to remain
Solution Approach 1:
The patent applies preliminary action by adjusting the pH of the cobalt sulfate solution to at least 4 immediately after dissolution, before purification steps. This preliminary pH adjustment enables subsequent easy removal of disruptive elements like copper, aluminum, chromium, and iron, which would be extremely difficult to separate at low pH values of 1.5-1.8
Solution Approach 2:
The patent changes the pH parameter from the naturally low value (1.5-1.8) obtained during dissolution to a higher value of at least 4. This parameter change fundamentally alters the chemical environment, enabling effective purification by precipitation of disruptive elements while maintaining cobalt sulfate solubility
2Temperature
If strong bases such as alkali metal hydroxide are used to adjust pH, then pH can be increased, but sodium salts contaminate the solution
Solution Approach 1:
The patent uses calcium oxide or calcium hydroxide instead of alkali metal hydroxides. Calcium-based reagents are cheaper and, when used in controlled amounts, do not introduce disruptive sodium salts into the solution. The calcium reagents can be easily removed or do not interfere with subsequent battery manufacturing processes
Solution Approach 2:
The patent introduces calcium oxide or calcium hydroxide as an intermediary substance to raise pH. These reagents serve as a bridge between the acidic cobalt sulfate solution and the desired higher pH state without introducing harmful contaminants like sodium ions that would compromise purity
3Temperature
If ammonia is used to increase pH, then pH can be adjusted, but copper complexes form which are difficult to separate from cobalt
Solution Approach 1:
The patent replaces ammonia with calcium oxide or calcium hydroxide as the pH adjustment reagent. This substitution avoids the formation of stable copper-ammonia complexes that would be extremely difficult to separate from cobalt. The calcium-based reagents achieve the same pH adjustment goal without introducing complexation side reactions
Solution Approach 2:
The patent converts the potential harm of pH adjustment (which could lead to unwanted complex formation) into a benefit by selecting reagents that raise pH without forming stable complexes with copper or other disruptive elements. The calcium-based reagents provide pH adjustment while leaving copper, iron, and chromium in forms that are easily removable through precipitation
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
The process effectively produces cobalt sulfate solutions with a pH of at least 4, reducing the presence of disruptive elements like copper, iron, and chromium, while maintaining a low sulfuric acid content and avoiding sodium contamination.
Implementation Method 1
dissolving metallic cobalt in aqueous sulfuric acid
Implementation Method 2
the so treated acidic cobalt sulfate solution with oxygen, oxygen-containing gas or with a substance that can split off oxygen
Data Source
AI summary
The invention relates to a method for producing an aqueous cobalt sulphate solution having a pH value of at least 4, characterised in that (a) metallic cobalt dissolves in aqueous sulfuric acid in an atmosphere which is low in oxygen, hydrogen or inert gas, and (b) the thus produced acidic cobalt sulphate solution is treated with oxygen, oxygen-containing gas or a substance which can eliminate the oxygen in an aqueous medium.