Multivalent Ion Desalination via Monovalent Addition
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Solution Overview
Problem
Current desalination processes face challenges in efficiently removing multivalent ion species, such as Ca2+, Mg2+, and SO42-, which can precipitate and cause scaling issues, limiting water recovery and increasing maintenance costs due to the need for frequent ion exchange resin regeneration.
Innovation Solution
The implementation of an electrodialysis system with monovalent ion permselective ion exchange membranes and a monovalent ion species addition subsystem, which directs feed water through a stack with separate chambers for multivalent cation and anion concentrating, allowing for the conversion of sparingly soluble multivalent ion species into highly soluble monovalent-multivalent ion pairs, reducing scaling risks and improving water recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electrodialysis is used to remove multivalent ion species, then salt ions are transferred from product to concentrate chambers, but multivalent ions precipitate and cause scaling issues that limit water recovery and increase maintenance costs
Solution Approach 1:
The patent changes the chemical parameters of the concentrate stream by adding monovalent ion species to the concentrated multivalent cation or anion solutions. This converts sparingly soluble multivalent ion pairs into highly soluble monovalent-multivalent ion pairs, preventing precipitation and scaling while enabling higher water recovery rates
Solution Approach 2:
The patent introduces monovalent ion species as an intermediary substance that mediates between multivalent ions and water. The monovalent ions form soluble complexes with multivalent ions in the concentrate stream, preventing direct precipitation of multivalent ion pairs and allowing continuous operation at high water recovery
2Productivity
If ion exchange resin is used for desalination, then salt ions are removed from feed water, but frequent resin regeneration is required which increases maintenance costs
Solution Approach 1:
The patent replaces the mechanical/chemical regeneration process of ion exchange resins with an electrodialysis system that uses electrical fields and ion-exchange membranes. This substitution eliminates the need for frequent chemical regeneration operations, reducing maintenance requirements while maintaining desalination efficiency
3Productivity
If water recovery is increased in desalination processes, then more freshwater is produced, but scaling risks increase due to higher concentrate concentrations
Solution Approach 1:
The patent changes the chemical composition parameters of the concentrate stream by adding monovalent ion species. This transforms the concentrate from containing sparingly soluble multivalent ion pairs to containing highly soluble monovalent-multivalent ion pairs, allowing water recovery to be increased to >95% without increasing scaling risk
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 approach effectively desalts saltwater, achieving >95% water recovery while minimizing scaling risks and reducing maintenance costs by converting multivalent ions into non-scaling salts, thus enhancing the efficiency and reliability of the desalination process.
Implementation Method 1
the cell comprises a product chamber, a multivalent cation concentrating chamber on a cathodic side of the product chamber, and a multivalent anion concentrating chamber on an anodic side of the product chamber. The product chamber and the multivalent cation concentrating chamber are each bounded by and share a cation exchange membrane and the product chamber and the multivalent anion concentrating chamber are each bounded by and share an anion exchange membrane
Implementation Method 2
ED and EDR are water treatment processes that transfer salt ions across ion exchange membranes under the action of a galvanic potential
Implementation Method 3
allowing for the conversion of sparingly soluble multivalent ion species into highly soluble monovalent-multivalent ion pairs, reducing scaling risks
Data Source
AI summary
Processes, systems, and techniques for multivalent ion desalination of a feed water use an apparatus that has a cathode, an anode, and an electrodialysis cell located between the cathode and anode. The cell has a product chamber through which the feed water flows, a multivalent cation concentrating chamber on a cathodic side of the product chamber through which the concentrated multivalent cation solution flows, and a multivalent anion concentrating chamber on an anodic side of the product chamber through which the concentrated multivalent anion solution flows. The product chamber and the multivalent cation concentrating chamber are each bounded by and share a cation exchange membrane, and the product chamber and the multivalent anion concentrating chamber are each bounded by and share an anion exchange membrane. A monovalent ion species is added to at least one of the concentrated multivalent cation solution and the concentrated multivalent anion solution.