Sodium Sulfate Conversion to Sodium Hydroxide via Nanofiltration
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Solution Overview
Problem
Sodium sulfate waste streams from industries such as lithium processing and lithium ion battery recycling are challenging to convert into valuable products like sodium hydroxide due to the presence of impurities, which foul electrochemical processes and require high energy consumption.
Innovation Solution
A process is developed to convert sodium sulfate into sodium hydroxide by reacting it with alkaline earth compounds, separating impurities using nanofiltration, and forming low solubility salts to precipitate out alkaline earth compounds, followed by electrochemical conversion of sodium chloride to sodium hydroxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrochemical methods are used to convert sodium sulfate into sodium hydroxide, then sodium hydroxide production is achieved, but energy consumption is very high and cost is very expensive
Solution Approach 1:
The patent applies preliminary action by converting sodium sulfate to sodium chloride before electrochemical conversion to sodium hydroxide. This pre-treatment step changes the feedstock to a more electrochemically efficient substrate, reducing the energy required in the subsequent electrolysis step while maintaining reliable sodium hydroxide production.
Solution Approach 2:
The patent changes the chemical composition parameter of the feedstock from sodium sulfate to sodium chloride. This parameter change fundamentally alters the electrochemical properties of the system, enabling more efficient electrolysis with lower energy consumption while achieving the same product output.
2Manufacturing precision
If nanofiltration is used to separate impurities from sodium sulfate, then separation is attempted, but sodium sulfate is rejected by the membrane reducing separation quality
Solution Approach 1:
The patent applies preliminary action by converting sodium sulfate to sodium chloride before nanofiltration. Since sodium chloride has different molecular size and charge characteristics compared to sodium sulfate, it passes through nanofiltration membranes more efficiently, enabling effective impurity separation without rejecting the valuable sodium salt.
Solution Approach 2:
The patent changes the ionic composition parameter from divalent sodium sulfate to monovalent sodium chloride. This parameter change exploits the size-exclusion and charge-based separation mechanisms of nanofiltration membranes, allowing the smaller monovalent ions to pass through while retaining impurities, thus achieving high separation quality.
3Reliability
If electrochemical processes are used to produce sodium hydroxide from sodium sulfate, then production is achieved, but impurities foul or damage the electrochemical process
Solution Approach 1:
The patent applies preliminary action by performing nanofiltration to remove impurities before the electrochemical conversion step. This pre-purification prevents impurities from entering the electrochemical cell, eliminating fouling and damage issues while maintaining reliable sodium hydroxide production from the converted sodium chloride.
Solution Approach 2:
The patent extracts harmful impurities from the sodium sulfate stream through nanofiltration before electrochemical processing. By removing these harmful components in advance, the electrochemical process operates on purified sodium chloride, preventing impurity-related fouling and damage while maintaining production reliability.
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 efficiently transforms sodium sulfate into sodium hydroxide with reduced energy consumption and handles impurities, enabling a circular economy by reducing waste and costs.
Implementation Method 1
it may be difficult to separate or remove these impurities using, for example, nanofiltration or electrodialysis
Implementation Method 2
electrochemical conversion of sodium chloride to sodium hydroxide
Implementation Method 3
forming low solubility salts to precipitate out alkaline earth compounds
Data Source
AI summary
The application pertains to processes for producing components such as an alkali hydroxide and a carboxylic acid. The processes generally comprise reacting a component comprising calcium carbonate, or calcium sulfide, or calcium hydroxide, or calcium oxide, or calcium weak acid, or any combination thereof with a component comprising a carboxylic acid to form a component comprising a calcium carboxylate and a component comprising carbon dioxide, or hydrogen sulfide, or water, or any combination thereof. At least a portion of the formed calcium carboxylate is reacted with a component comprising an alkali sulfate to form a component comprising an alkali carboxylate and a component comprising calcium sulfate. At least a portion of the formed alkali carboxylate is electrochemically reacted to form a component comprising an alkali hydroxide and a component comprising a carboxylic acid.