Electrolytic CO2 Removal Device for Ion Chromatography
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Solution Overview
Problem
In ion chromatography, carbonate-based eluents suffer from high background conductivity due to carbon dioxide contamination, which interferes with analyte detection and separation, and existing CO2 removal devices require periodic base regeneration and have limited CO2 removal capacity.
Innovation Solution
An electrolytic CO2-removal device with a basic chamber containing an aqueous cation hydroxide solution, a CO2-permeable barrier, and anion exchange membranes that allow for the efficient removal of CO2 from aqueous liquid streams by passing a current through the device, effectively reducing background conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If carbonate eluents are used for anion separation, then the ease of controlling carbonate to bicarbonate ratio for selectivity is improved, but the background conductivity increases to 10-20 μS/cm which reduces detection limits
Solution Approach 1:
The device segments the eluent stream into two paths: one through the fiber membrane where CO2 diffuses out, and another regeneration path where base solution absorbs the removed CO2. This segmentation allows simultaneous maintenance of carbonate eluent benefits while removing harmful CO2 contamination.
Solution Approach 2:
A base regenerant solution acts as an intermediary medium that absorbs CO2 diffusing through the fiber membrane. The base solution temporarily holds the removed CO2 as carbonate/bicarbonate, preventing it from re-contaminating the eluent and maintaining low background conductivity.
2Object-affected harmful factors
If hydroxide eluents are used to achieve low background conductivity, then the detection limits are improved, but contamination from ambient carbon dioxide occurs which compromises separation
Solution Approach 1:
The fiber membrane performs preliminary CO2 removal from hydroxide eluents before they enter the separation column. By pre-removing CO2 through diffusion across the membrane, the eluent is protected from ambient carbon dioxide contamination that would otherwise compromise separation quality.
Solution Approach 2:
The system uses the eluent's own flow to drive CO2 removal through the fiber membrane. The flowing eluent continuously refreshes the concentration gradient across the membrane, enabling self-sustaining CO2 removal without external intervention beyond the initial setup.
3Quantity of substance
If existing CO2 removal devices using base regenerant are used, then CO2 removal capacity is achieved, but periodic base regeneration is required which reduces productivity
Solution Approach 1:
The device enables continuous CO2 removal by maintaining a constant concentration gradient across the fiber membrane through continuous eluent flow. This eliminates the periodic interruption required for base regeneration in traditional devices, allowing uninterrupted operation and improved productivity.
Solution Approach 2:
The invention replaces the mechanical/regenerative base system with a passive diffusion-based CO2 removal mechanism. Instead of using pumped base solution that requires regeneration, the system relies on natural diffusion of CO2 through the fiber membrane driven by concentration gradients, eliminating the need for periodic regeneration operations.
4Quantity of substance
If liquid or gas flow regenerant is used to remove carbonic acid from fiber membrane, then CO2 removal is achieved, but the regenerant becomes contaminated and requires diversion to waste
Solution Approach 1:
The fiber membrane creates a localized CO2 removal zone where CO2 diffuses from the eluent through the membrane into the base regenerant. This localized action allows efficient CO2 removal at the membrane interface while the bulk regenerant solution remains relatively clean and can be recycled or disposed of minimally.
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 device achieves significant reduction in background conductivity, improving detection limits and reducing contamination, with a CO2 removal efficiency of over 90%, eliminating the need for periodic base regeneration and enhancing the reliability of ion chromatography analyses.
Implementation Method 1
a CO2-permeable barrier which substantially blocks the passage of water
Implementation Method 2
a first anion exchange membrane on one side of said basic chamber; (e) a second anion exchange membrane on the opposite side of said basic chamber from said first anion exchange membrane
Implementation Method 3
passing a current through a first anion exchange membrane on one side of said basic chamber from a cathode on the opposite side of said first anion exchange membrane from said basic chamber, said current passing through said basic chamber and a second anion exchange membrane on the opposite side of said basic chamber from said first anion exchange membrane to an anode on the opposite side of said basic chamber from said second anion exchange membrane, to regenerate said basic medium
Implementation Method 4
The CRD 200 and CRD 300 both use a liquid or gas flow stream on the outside of the fiber to remove the carbonic acid as it diffuses from the inside of the fiber to the outside
Data Source
AI summary
An electrolytic CO2-removal device for anion analysis of a liquid sample. The device includes a basic chamber and CO2-permeable tubing in the basic chamber. Anion exchange membranes are disposed on opposite sides of the basic chamber, and electrodes are disposed outside the membranes. The device can be integral with a suppressor in an ion chromatography system and/or an aqueous stream purifier. Also, methods performed by the device.