Bipolar Membrane Electrodialysis for Scale-Free Ocean Alkalinity
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Solution Overview
Problem
Existing electrochemical systems for ocean alkalinity enhancement face issues with scaling due to divalent cations like calcium and magnesium, leading to increased energy consumption and membrane disruption, necessitating expensive pretreatments to remove these cations.
Innovation Solution
A method for bipolar membrane electrodialysis that allows direct input of brine streams containing divalent cations without pretreatment, by maintaining a higher flow rate through the base compartment relative to the brine compartment to keep pH below the precipitation threshold, thereby preventing scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If CO2 is captured and stored in deep geological formations, then atmospheric CO2 levels are reduced, but the cost and energy requirements become prohibitively high
Solution Approach 1:
The patent converts the harmful effect of CO2 dissolution in oceans (ocean acidification) into a beneficial process by introducing alkaline materials that neutralize acidity while simultaneously sequestering CO2. The CO2 that would normally harm marine ecosystems is instead transformed into stable carbonate minerals through alkalinity enhancement, turning an environmental problem into a solution for both carbon storage and ocean health restoration
Solution Approach 2:
The patent introduces alkaline materials (such as olivine, serpentine, or engineered alkaline compounds) as intermediary substances that facilitate CO2 sequestration. These intermediaries react with CO2 in seawater to form bicarbonate and carbonate ions, which then precipitate as stable minerals. This intermediary approach reduces the direct energy burden of CO2 compression and transport required in geological storage methods
2Quantity of substance
If CO2 is dissolved directly in oceans to form carbonic acid, then CO2 is sequestered, but ocean acidification harms marine life
Solution Approach 1:
The patent directly addresses ocean acidification by introducing alkaline materials that neutralize the acidity caused by CO2 dissolution. The alkaline substances react with H+ ions produced by carbonic acid formation, shifting the chemical equilibrium and converting harmful acid into beneficial carbonate buffers. This process maintains CO2 sequestration while protecting marine ecosystems from acidification damage
Solution Approach 2:
The patent changes the chemical parameters of seawater by introducing alkaline substances that increase pH and alkalinity. This parameter modification allows the ocean to absorb CO2 without experiencing dangerous acidification, as the alkaline buffer capacity prevents excessive drops in pH. The system maintains optimal chemical conditions for both CO2 storage and marine life survival
3Productivity
If chemical additives are used to enhance alkalinity, then CO2 absorption is improved, but harmful chemicals may damage the environment
Solution Approach 1:
The patent employs naturally occurring alkaline materials such as olivine and serpentine that can be mined and applied to ocean surfaces. These materials are abundant, inexpensive, and biodegradable, breaking down into harmless minerals over time. They provide effective alkalinity enhancement without the persistence and toxicity concerns of synthetic chemical additives, offering a sustainable solution that maintains high CO2 absorption rates while minimizing environmental harm
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 enhances ocean alkalinity efficiently and cost-effectively, reducing the need for pretreatment and extending membrane lifespan while producing high-quality negative emission carbon removal.
Implementation Method 1
an electrochemical cell that uses sunlight to split water into hydrogen and oxygen
Implementation Method 2
The photoanode is any material or structure that absorbs photons and uses that energy to drive a chemical reaction or generate electrical energy
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
The disclosure relates to enhancing alkalinity of brine, e.g. seawater, using bipolar membrane electrodialysis (BPMED) without removing divalent cations that otherwise cause scaling. In one embodiment, a BPMED is employed wherein the brine volumetric flow rate through a basification compartment is greater at a given current density than that through a brine compartment which increases the pH of the brine output while keeping it below the precipitation pH. In one embodiment, the spacer located in the basification compartment is thicker than spacers elsewhere in the BPMED so as resist membrane distortion due to the increased hydrostatic pressure in the basification compartment given the greater volumetric flow. The brine output having increased alkalinity can be returned to the ocean to mitigate acidification and enable capture of atmospheric carbon dioxide.