Cobalt Electrowinning pH Buffering for Stable Cathode Detachment

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Solution Overview

Problem

Existing cobalt recovery methods, such as electrowinning, face issues with high processing costs and difficulty in controlling the detachability of cobalt deposits from cathodes, leading to decreased current efficiency and potential short-circuits due to pH fluctuations and adhesiveness problems.

Innovation Solution

A cobalt recovery method involving the addition of an additive with pH buffering properties, such as potassium hydrogen phthalate, to a cobalt sulfate solution to control adhesiveness and pH stability during electrowinning, ensuring easy detachment of cobalt and maintaining current efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the pH of the electrolytic solution is maintained at a high state to improve current efficiency, then current efficiency is improved, but adhesiveness between deposited cobalt and cathode deteriorates causing natural detachment and short-circuits

Engineering Contradiction:

Improvecurrent efficiencyVSAvoidadhesiveness between cobalt and cathode

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The invention changes the chemical composition parameter by introducing a specific additive (polymer containing carboxylic acid groups) that modifies the interfacial properties between cobalt and cathode. This additive maintains strong adhesiveness even at high pH levels, allowing the system to operate at optimal current efficiency without suffering from poor adhesiveness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The polymer additive acts as an intermediary substance between the deposited cobalt and the cathode surface. It forms a bonding bridge that maintains strong adhesion forces, preventing natural detachment and short-circuits while allowing high pH operation for improved current efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the pH of the electrolytic solution is kept low to prevent natural detachment of cobalt, then adhesiveness is maintained, but current efficiency decreases due to hydrogen-evolution reactions

Engineering Contradiction:

Improveadhesiveness between cobalt and cathodeVSAvoidcurrent efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention changes the chemical environment by adding a polymer additive that specifically enhances cobalt-cathode bonding. This allows the system to maintain strong adhesiveness at higher pH levels, eliminating the need to operate at low pH and thereby preventing hydrogen-evolution reactions that reduce current efficiency

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If electrode plate surface roughness is increased to ensure detachability of deposited metal, then cobalt detachability is improved, but processing cost increases

Engineering Contradiction:

Improvecobalt detachabilityVSAvoidprocessing cost

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The invention uses a chemically active polymer additive that is consumed during the electrowinning process to achieve cobalt detachability. This chemical approach is more economical than mechanical surface roughening methods, as the additive can be added in controlled amounts and does not require complex electrode manufacturing or maintenance

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention replaces mechanical methods (surface roughening) with a chemical method (polymer additive) to achieve cobalt detachability. The polymer chemically interacts with the deposited cobalt to control its bonding characteristics, providing a simpler and more cost-effective solution than mechanical surface modification

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The method enables efficient and stable cobalt recovery by controlling adhesiveness and pH, reducing short-circuit risks and maintaining high current efficiency, while allowing recovery from lithium ion battery scraps.

Implementation Method 1

when a pH of the electrolytic solution decreases to 2.0 or less, the additive is deposited on a surface of a cathode

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 2

the cobalt is electrolytically reduced and deposited on a surface of the cathode by applying a predetermined voltage between the anode and the cathode

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Implementation Method 3

the additive has a pH buffering effect in a pH range of 2.0 or more and 4.5 or less

Methodology Applied

Scientific EffectBuffering:

Data Source

PatentEP4715094A1Cobalt recovery method

Publication Date: 2026.03.25 MITSUBISHI MATERIALS CORP

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Figure 3A~3B

AI summary

A cobalt recovery method of recovering cobalt from a cobalt sulfate solution, which includes adding, to the cobalt sulfate solution, an additive in which solubility decreases at a pH of 2.0 or less, and electrowinning cobalt from the cobalt sulfate solution to which the additive is added. It is preferable that the additive has a pH buffering effect in a pH range of 2.0 or more and 4.5 or less.