High-Purity Nickel Sulfate Production via Staged pH Precipitation
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Solution Overview
Problem
Current methods for producing high purity nickel sulfate from acidic solutions containing nickel face challenges in efficiently removing impurities like magnesium, manganese, and calcium, which are essential for battery materials, as existing solvent extraction techniques suffer from decreased efficiency and co-precipitation of valuable metals.
Innovation Solution
A method involving sulfurization, redissolution, solution purification, and solvent extraction steps using an acidic phosphoric acid ester-based extractant, with pH adjustment and oxidizing agents, to selectively separate and remove impurities, resulting in high purity nickel sulfate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature pressure leaching is used to treat low level oxide ores, then nickel extraction efficiency is improved, but impurity incorporation (magnesium, manganese, calcium) into nickel salts increases
Solution Approach 1:
The purification process is divided into multiple sequential stages: first removing iron at pH 3.0-4.0, then aluminum at pH 4.0-5.0, and finally magnesium and manganese at pH 8.0-9.0. This staged approach allows selective removal of different impurity groups without co-precipitating nickel, thereby achieving high purity nickel sulfate while maintaining efficient nickel extraction from low-grade ores.
Solution Approach 2:
The invention utilizes systematic pH adjustment as a key parameter change to control impurity precipitation. By progressively increasing pH from 3.0 to 9.0 in controlled stages and using specific alkaline agents (lime, caustic soda, soda ash), the process selectively precipitates different metal hydroxides while keeping nickel in solution, thus resolving the contradiction between extraction efficiency and product purity.
2Manufacturing precision
If conventional solvent extraction is used to purify nickel solution, then some impurities are removed, but extraction efficiency decreases and valuable metals may co-precipitate
Solution Approach 1:
Before performing solvent extraction, the invention conducts preliminary pH-controlled precipitation to remove iron, aluminum, magnesium, and manganese impurities. This preliminary purification step prevents these impurities from interfering with the subsequent solvent extraction process, thereby maintaining high extraction efficiency for nickel while ensuring thorough impurity removal. The preliminary action eliminates the need for repeated extraction cycles that would reduce productivity.
3Manufacturing precision
If electrolytic winning is used to obtain nickel metal first, then high purity nickel sulfate can be produced, but significant electric power and large scale facilities are required
Solution Approach 1:
The invention replaces the energy-intensive electrolytic winning process with a chemical purification approach using pH-controlled precipitation and solvent extraction. Instead of using electrical current to deposit and re-dissolve nickel metal, the process uses chemical reactions (hydroxide precipitation at controlled pH levels and liquid-liquid extraction) to purify nickel sulfate directly from the leach solution, dramatically reducing electric power consumption and facility requirements while achieving comparable or superior purity.
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 effectively produces nickel sulfate with low magnesium levels, suitable for battery applications, ensuring stable quality and efficient operation even with fluctuating raw material levels.
Implementation Method 1
adding a sulfurizing agent to an acidic solution containing nickel, and obtaining a precipitate of nickel sulfide
Implementation Method 2
adding an oxidizing agent to the slurry, carrying out redissolution at a temperature in a range from 60°C to 180°C, and thereby obtaining a concentrated solution of nickel
Implementation Method 3
subjecting the concentrated solution of nickel obtained in the redissolution step of (2), to neutralization by addition of an alkali as a neutralizing agent to adjust a pH to a range of from 5.0 to 6.0
Implementation Method 4
subjecting the concentrated solution of nickel after iron removal obtained in the solution purification step of (3), to solvent extraction
Data Source
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AI summary
Provided is a production method for obtaining high purity nickel sulfate having low levels of impurities, particularly low levels of magnesium and chloride, by adjusting the concentration of an extractant and the pH concentration at the time of treatment in a process of obtaining a nickel sulfate solution having a high nickel concentration by solvent extraction using an acidic organic extractant. The method includes treating an acidic solution containing nickel through at least the following steps of: a sulfurization step of adding a sulfurizing agent to the acidic solution containing nickel, and obtaining a precipitate of nickel sulfide and a solution after sulfurization; a redissolution step of preparing a slurry of the nickel sulfide obtained in the sulfurization step, adding an oxidizing agent to the slurry, and thereby obtaining a concentrated solution of nickel; a solution purification step of subjecting the concentrated solution of nickel obtained in the redissolution step to neutralization by addition of a neutralizing agent, and thereby obtaining a neutralized precipitate and a concentrated solution of nickel after iron removal thus produced; and a solvent extraction step of subjecting the concentrated solution of nickel after iron removal obtained in the solution purification step, to solvent extraction, and obtaining a stripped liquid and a nickel sulfate solution.