Method for producing lithium sulfate and transition metal sulfate

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Solution Overview

Problem

Current methods are inefficient and economically unfeasible for separating and recovering high-purity transition metals and lithium from aqueous sulfate solutions, particularly due to sodium contamination and the need for extensive post-treatment processes.

Innovation Solution

A two-stage crystallization process combining concentration-crystallization and cooling crystallization is employed to separate and recover lithium sulfate and transition metal sulfate, effectively preventing sodium contamination and reducing the need for additional purification steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional methods (reacting lithium sulfate with sodium carbonate or calcium hydroxide) are used to produce lithium hydroxide, then lithium hydroxide can be synthesized, but a large amount of sodium sulfate or calcium carbonate is generated as by-products and dissolved lithium carbonate is mixed with the by-product solution requiring additional post-treatment

Engineering Contradiction:

Improvepurity of lithium hydroxideVSAvoidnumber of post-treatment processes

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes sodium ions from the lithium sulfate solution using ion exchange resin or selective precipitation methods before producing lithium hydroxide, thereby eliminating the formation of sodium sulfate by-products and the need for subsequent separation processes

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent recovers valuable transition metals (nickel, cobalt) from the aqueous solution as sulfate salts while selectively removing sodium impurities, transforming waste streams into recoverable resources and eliminating harmful by-products

Inventive Principle:

Principle #34Discarding and recovering

2Manufacturing precision

If electrochemical membrane separation method is used to produce lithium hydroxide from lithium sulfate, then high-grade lithium hydroxide can be obtained, but alkali metals (sodium) cannot be separated and must be prevented from contaminating the lithium sulfate raw material

Engineering Contradiction:

Improvepurity of lithium hydroxideVSAvoiddifficulty of preventing sodium contamination

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent performs preliminary removal of sodium ions from the aqueous solution through ion exchange or selective precipitation before the electrochemical membrane separation process, ensuring that sodium contamination is prevented at the source rather than dealing with it during or after the main production process

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If solvent extraction method is used to separate transition metals, then transition metals can be recovered, but a large amount of sodium sulfate is mixed in the residual liquid requiring treatment

Engineering Contradiction:

Improvepurity of transition metal sulfateVSAvoidamount of sodium sulfate waste

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent converts the harmful effect of sodium sulfate accumulation into a beneficial outcome by using the sodium-free environment to enable direct crystallization of high-purity transition metal sulfates, while the removed sodium is disposed of as a minor stream and the main residual liquid becomes a valuable lithium sulfate source

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 high-purity lithium sulfate and transition metal sulfate recovery, enhancing the economic efficiency of the recycling process by minimizing sodium content and avoiding the generation of excess sodium sulfate, thus improving the overall recycling efficiency and reducing operational costs.

Implementation Method 1

a step of concentration-crystallization to an aqueous solution comprising at least lithium sulfate and a transition metal sulfate as main components so as to obtain a slurry comprising lithium sulfate as a solid content

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

a step of cooling crystallization to an aqueous solution comprising at least lithium sulfate and a transition metal sulfate as main components so as to obtain a solid content of crystals comprising the transition metal sulfate

Methodology Applied

Scientific EffectCooling: Cooling

Data Source

PatentUS20240286912A1Method for producing lithium sulfate and transition metal sulfate

Publication Date: 2024.08.29 TODA KOGYO CORP

AI summary

The present invention is to provide a means for efficiently and economically separating and recovering transition metals including nickel and cobalt, and lithium from an aqueous sulfate solution comprising the transition metal and lithium as major components.The present invention is a process for producing lithium sulfate comprising:a step of concentration-crystallization to an aqueous solution comprising at least lithium sulfate and a transition metal sulfate as main components so as to obtain a slurry comprising lithium sulfate as a solid content, anda step of solid-liquid separation of the slurry obtained in the step of concentration-crystallization so as to separate lithium crystals and a crystallization mother liquor.