Ni/Co Feed Sulphidation With pH-Staged Impurity Separation
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Solution Overview
Problem
Existing processes struggle to efficiently recover high-purity nickel and cobalt from metal-containing feeds due to the formation of water-soluble compounds when using sulphuric acid without a sulphidising agent, leading to reduced recovery rates.
Innovation Solution
A method involving sulphidation at a higher pH (3 to 10) followed by acid addition to form water-soluble sulphate salts, allowing full conversion of Ni and/or Co compounds, and subsequent pH reduction to below 3.5 to dissolve impurities, with a two-stage process in a closed reactor to enhance recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sulphuric acid is used without a sulphidising agent, then the process is simpler, but water-soluble nickel and cobalt sulphates form leading to reduced recovery rates
Solution Approach 1:
The patent applies preliminary action by first adjusting the pH to 3-10 before adding sulphuric acid, which creates optimal conditions for sulphidation to occur. This preliminary pH adjustment ensures that nickel and cobalt compounds are fully converted to sulphides before acid treatment, preventing the formation of water-soluble sulphates and subsequent loss of these valuable metals.
Solution Approach 2:
The patent utilizes parameter changes by controlling the pH within a specific range of 3-10 during the sulphidation process. This parameter control is critical as it determines whether nickel and cobalt form insoluble sulphides (at pH 3-10) or soluble sulphates (at lower pH). By maintaining pH in the 3-10 range, the process ensures complete sulphidation and maximizes metal recovery while simplifying the overall process design.
2Loss of substance
If pH is kept high to ensure full sulphidation of Ni and Co, then recovery is improved, but impurities remain dissolved and separation becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the pH adjustment into two distinct stages: first adjusting pH to 3-10 for complete sulphidation of nickel and cobalt, then subsequently lowering the pH to dissolve impurities. This segmented approach to pH control allows each metal to be treated under optimal conditions at different times, achieving both high recovery and effective separation.
Solution Approach 2:
The patent implements periodic action through sequential pH adjustments - first maintaining high pH (3-10) to ensure complete sulphidation, then periodically lowering the pH to dissolve impurities. This periodic change in pH conditions enables the process to achieve both complete metal conversion and effective impurity separation in a systematic manner.
3Manufacturing precision
If conventional leaching processes are used, then impurities can be removed, but nickel and cobalt form water-soluble compounds leading to loss
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of leaching first and then attempting to precipitate metals, the process first converts nickel and cobalt to insoluble sulphides through controlled sulphidation at pH 3-10, then removes impurities by lowering pH. This inverted sequence ensures metals are protected from loss while impurities are selectively removed.
Solution Approach 2:
The patent uses sulphidation as an intermediary step that converts nickel and cobalt compounds into insoluble sulphide forms. This intermediary transformation acts as a protective mechanism, converting metals into a stable, insoluble state that prevents subsequent loss during impurity removal operations, while still allowing impurities to be dissolved and separated.
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 enables selective leaching of impurities like Mn and Mg, improving the recovery of Ni and Co by forming them as sulphides in the solid phase while impurities are collected in the aqueous phase, facilitating efficient separation and purification.
Implementation Method 1
sulphidation preferably takes place first at a relatively higher pH, such as between 3 and 10, to allow for the full conversion, more specifically of the full sulphidation of Ni and/or Co compounds
Implementation Method 2
subsequently an acid is added to further dissolve all impurities with the formation of water-soluble sulphate salts
Implementation Method 3
reducing the pH of the aqueous reaction medium to a pH below 3.5 or even below 3.0
Data Source
AI summary
The present invention provides a method for processing a metal-containing feed comprising at least one Ni compound and/or at least one Co compound, said feed further comprising one or more impurities, said method comprising the steps of: i. reacting in an aqueous medium at a pH between 1.5 and 10 said metal-containing feed with a sulphidising agent, thereby obtaining a slurry comprising a Ni- and/or Co-containing solid phase and an aqueous phase comprising one or more water-soluble salts of Mn, Mg, Al, Fe, Ca, B, Na and/or U; ii. separating said solid phase and said aqueous phase.