Cathode Scrap Leachate Purification via Staged pH Precipitation
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Solution Overview
Problem
The recycling process of scrap positive electrode materials from lithium batteries faces challenges in removing metal impurities like Fe, Al, Ca, Mg, and Pb, which affects the quality and performance of the recycled materials, and requires high water usage and longer filtration times, leading to reduced recycling efficiency and increased costs.
Innovation Solution
A method involving controlled temperature and pH conditions in multiple reactor stages to precipitate and separate metal ions, using alkaline solutions and complexing agents to remove impurities step-wise, including lithium ions before co-precipitation, to obtain high-crystallinity precipitates facilitating efficient filtration and washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional precipitation method is used to remove metal impurities, then impurity removal is achieved, but the precipitate is difficult to filter and wash, resulting in high impurity content in the final product
Solution Approach 1:
The patent changes the pH parameter during precipitation to control the morphology and filterability of the precipitate. By adjusting pH to specific ranges (4.5-5.5 for first precipitation, 9.0-10.0 for second precipitation), the method produces precipitates with different characteristics that are easier to filter and wash, directly resolving the contradiction between impurity removal effectiveness and filtration ease.
2Manufacturing precision
If conventional filtration process is used, then impurity removal is achieved, but more water is needed for cleaning and more time is required for filtration
Solution Approach 1:
The patent uses pH parameter changes to create precipitates with improved filtration characteristics. The controlled precipitation at specific pH values produces particles that filter faster and require less washing water, thereby reducing both time and water consumption while maintaining effective impurity removal.
3Measurement precision
If on-line pH meter is used to control pH in high concentration lithium ion solution, then precise pH control is achieved, but the pH meter is prone to lithium ion poisoning, affecting process stability
Solution Approach 1:
The patent performs preliminary removal of lithium ions through controlled precipitation at pH 4.5-5.5 before the main precipitation step. This preliminary action reduces lithium ion concentration to levels that will not poison the pH meter during subsequent operations, thereby maintaining both measurement precision and process stability.
Solution Approach 2:
The patent introduces controlled precipitation as an intermediary step that modifies the solution composition before the main process. This intermediary precipitation removes excess lithium ions that would otherwise act as harmful factors, protecting the pH meter and ensuring stable process continuation.
4Productivity
If sodium hydroxide is used as precipitant, then production efficiency is improved and equipment size is reduced, but water usage increases in the recycling process
Solution Approach 1:
The patent uses pH parameter control to optimize the precipitation process efficiency. By maintaining pH in specific ranges during precipitation with sodium hydroxide, the method achieves complete impurity removal in fewer steps, improving production efficiency while the improved filterability of the precipitate reduces water consumption during washing.
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 enhances the recycling efficiency by reducing impurity content, minimizing water usage, and improving the crystallinity of precipitates, thereby increasing the recycling rate of nickel, cobalt, and manganese while maintaining stable reaction conditions.
Implementation Method 1
controlling the flow rate of a leachate of scrap positive electrode materials of lithium batteries and a first alkaline solution at a first temperature higher than the room temperature and a constant first pH to remove, by precipitation, iron ions, aluminum ions and at least part of copper ions
Implementation Method 2
controlling the flow rate of the first filtrate, a complexing agent and a second alkaline solution at a second temperature higher than the room temperature and within a constant first pH range to remove lithium ions
Implementation Method 3
controlling the flow rate of the first solution and a fluorine-containing precipitant at a third temperature high than the room temperature and a constant concentration of fluorinion to remove, by precipitation, calcium ions, magnesium ions and at least part of lead ions
Data Source
AI summary
The present disclosure discloses a method for impurity removal and treatment in the recycling process of scrap positive electrode materials of lithium batteries. The method includes controlling a flow rate of a leachate of scrap positive electrode materials of lithium batteries and a first alkaline solution at a first temperature higher than the room temperature and a constant first pH value to remove, by precipitation, iron ions, aluminum ions and at least part of copper ions to obtain a first filtrate; controlling the flow rate of the first filtrate, a complexing agent and a second alkaline solution at a second temperature higher than the room temperature and within a constant first pH range to obtain a target substance precipitate by separating a second filtrate containing lithium ions from the first filtrate; dissolving the target substance precipitate to obtain a first solution; and controlling the flow rate of the first solution and a fluorine-containing precipitant at a third temperature high than the room temperature and a constant concentration of fluorinion to remove, by precipitation, calcium ions, magnesium ions and at least part of lead ions to obtain a target solution. By the method of the present disclosure, a precipitate with a large particle size, high crystallinity and low water content can be obtained, which facilitates washing and improves the recycling rate of nickel-cobalt-manganese from the scrap positive electrode materials of lithium batteries.