Cathode Leachate Defluorination Using Dawsonite Selective Precipitation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for recycling lithium batteries fail to effectively remove fluorion from cathode leaching solutions, leading to poor quality of subsequent products, equipment corrosion, and wastewater treatment issues.
Innovation Solution
A method involving the addition of acid and oxidant to leach battery powder, followed by the use of dawsonite and sulfuric acid to react with the fluorion-containing solution, achieving solid-liquid separation and producing defluorinated solutions and crude sodium hexafluoroaluminate, while selectively removing fluorion without affecting nickel, cobalt, and manganese.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional extraction method is used to remove nickel, cobalt and manganese with extractant, then these metals can be recovered, but fluorion enters the solution containing these metals resulting in poor quality of precursor product
Solution Approach 1:
The process is divided into two separate stages: first extracting nickel, cobalt and manganese metals from the leaching solution, then separately removing fluorion from the remaining raffinate. This segmentation prevents fluorion from contaminating the metal-containing solution, thereby maintaining precursor product quality while effectively recovering valuable metals.
Solution Approach 2:
Calcium carbonate is introduced as an intermediary substance to remove fluorion from the raffinate. The calcium carbonate reacts with fluorion to form calcium fluoride precipitate, which can be easily separated. This intermediary approach allows fluorion removal without affecting the previously extracted metals, solving the quality issue.
2Productivity
If fluorion is not removed from raffinate, then the extraction process is simple, but fluorion impacts oil removal and COD treatment resulting in wastewater failing to meet standards
Solution Approach 1:
Fluorion removal is performed as a preliminary treatment step before the raffinate enters the wastewater treatment system for oil removal and COD reduction. By removing fluorion in advance using calcium carbonate, subsequent treatment processes are not hindered, ensuring wastewater meets discharge standards while maintaining overall process efficiency.
3Ease of manufacture
If fluorion is present in the solution, then the leaching process can proceed without additional treatment, but equipment corrosion increases and service life decreases
Solution Approach 1:
Fluorion is extracted from the raffinate solution through precipitation with calcium carbonate. The fluorion is taken out of the solution in the form of calcium fluoride solid precipitate, which is then separated by filtration. This extraction eliminates the corrosive fluorion from the system, protecting equipment and extending service life while keeping the overall process straightforward.
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 achieves a high fluorion removal rate of 99% and produces high-purity sodium hexafluoroaluminate, reducing equipment corrosion and improving wastewater quality, with potential applications in the electrolytic aluminum industry and other uses.
Implementation Method 1
adding dawsonite and sulfuric acid to the fluorion-containing solution for reaction under stirring at a certain temperature, performing solid-liquid separation to obtain a defluorinated solution
Implementation Method 2
mixing aluminum powder with a sodium hydroxide solution for reaction, performing filtering to obtain a metaaluminate solution
Implementation Method 3
2Al+2NaOH+2H2O=2NaAlO2+3H2 ↑
Implementation Method 4
introducing carbon dioxide gas into the metaaluminate solution for reaction under stirring at a certain temperature until an end-point pH value of a resulting solution is stable in a certain range
Implementation Method 5
NaAlO2+CO2+H2O=NaAlCO3(OH)2 ↓
Implementation Method 6
the oxidant is hydrogen peroxide
Data Source
AI summary
Disclosed is a method for removing fluorine in a positive electrode leachate of lithium batteries, comprising: adding acid and an oxidizing agent to battery powder for leaching, and removing impurities from the obtained leachate to obtain a fluorine-containing solution; adding dawsonite to the fluorine-containing solution, and meanwhile adding sulfuric acid, stirring for reaction at a certain temperature, and performing solid-liquid separation to obtain fluorine-removed solution and filter residues; and washing the filter residues to obtain crude sodium hexafluoroaluminate. According to the present invention, the dawsonite is used for removing fluorine from waste lithium batteries, the dawsonite has good selectivity, does not react with nickel, cobalt, manganese, lithium and the like in the solution, and only reacts with fluorine ions in the solution, so that the purpose of selectively removing fluorine is achieved, and the loss of nickel, cobalt, manganese and lithium metals in the solution is avoided.