Selective Rare Earth Recovery from Waste via pH-Controlled Dissolution
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Solution Overview
Problem
Current methods for recovering rare earths from waste, such as nickel-metal hydride batteries and permanent magnets, are inefficient, costly, and pose environmental and health risks due to high acid concentrations, energy consumption, and complex processes that require dismantling and multiple steps, leading to significant effluent volumes and reprocessing costs.
Innovation Solution
A selective recovery process involving the dissolution of waste in an acidic aqueous solution at controlled pH (1.5-4.5) to selectively dissolve rare earths, followed by precipitation as double sulfates, reducing the need for dismantling and minimizing acid use, conducted at ambient temperature and atmospheric conditions to minimize energy and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high concentration acidic solutions are used for complete dissolution of waste, then dissolution efficiency is improved, but environmental and health risks increase significantly
Solution Approach 1:
The patent changes the pH parameter from highly acidic (pH < 0) to mildly acidic (pH 1.5-4.5), transforming the dissolution process to achieve adequate rare earth extraction while significantly reducing the harmful effects of high acid concentration on the environment and human health
Solution Approach 2:
The patent converts the harmful high acid concentration into a beneficial mild acid environment, where the acid is still effective for dissolving rare earths from the waste but no longer poses severe environmental and health risks, thus turning a harmful factor into a controlled beneficial process
2Productivity
If complete dissolution of waste is achieved, then rare earth recovery is improved, but nickel value is lost due to dissolution in liquid phase
Solution Approach 1:
The patent applies selective dissolution by creating local chemical conditions (pH 1.5-4.5) that are specifically suitable for dissolving rare earth compounds while leaving nickel compounds undissolved in the solid phase, thus achieving differential treatment of different materials in the waste
Solution Approach 2:
The patent extracts only the rare earth elements from the waste matrix by controlled dissolution, leaving nickel and other valuable metals in the solid phase for separate recovery, thus separating desired components from unwanted ones without complete dissolution
3Manufacturing precision
If traditional dissolution and precipitation processes are used, then rare earth separation is achieved, but effluent volumes and reprocessing costs increase significantly
Solution Approach 1:
The patent extracts rare earths directly from the waste in divided form through selective dissolution at controlled pH, bypassing the need for complete waste dissolution and subsequent complex precipitation processes, thus significantly reducing effluent generation
Solution Approach 2:
The patent applies partial dissolution action, dissolving only the rare earth-containing phases at controlled pH rather than completely dissolving all waste materials, which achieves sufficient rare earth separation while minimizing the quantity of liquid effluent that requires treatment
4Loss of time
If waste is not dismantled before treatment, then processing time is reduced, but treatment efficiency may be compromised
Solution Approach 1:
The patent creates a universal treatment process that can handle waste in divided form directly without requiring prior dismantling of batteries or separation of components, making the process applicable to various waste forms while maintaining treatment efficiency through selective pH-controlled dissolution
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 process achieves selective and efficient rare earth recovery with reduced energy consumption, lower reagent use, and lower effluent volumes, significantly reducing environmental and health risks while increasing the value of recovered nickel by maintaining it in a solid phase.
Implementation Method 1
dissolving the waste in divided form in an acidic aqueous solution to release the rare earth into the liquid phase
Implementation Method 2
precipitating the rare earth as a rare earth double sulfate by introducing a sulfate into the liquid phase collected at the end of step (b)
Data Source
AI summary
The invention relates to a method for the selective recovery of at least one rare earth element present in waste, comprising the following steps: (a) dissolving the waste in divided form in an acidic aqueous solution to release the rare earth element into the liquid phase, (b) collecting the liquid phase, (c) precipitating the rare earth element as a rare earth double sulfate by introducing a sulfate into the liquid phase collected after step (b), and (d) collecting the precipitate. Step (a) of dissolution is carried out by immersing and maintaining, for a time t, the waste in divided form in an aqueous solution S1 comprising hydrochloric acid and having a constant pH between 1.5 and 4.5 for that time t. The invention also relates to a method for recovering value from waste comprising at least one rare earth element, implementing this recovery method.