Researchers at MIT have developed a novel approach using nanofiltration that effectively pull CO2 from the air and release it later, without the typical efficiency tradeoff of most modern methods.
By inserting a nanofiltration step between the capture and release stages, the team has boosted overall efficiency by up to six times and reduced system costs by at least 20%.
The findings, published in ACS Energy Letters, come from doctoral students Simon Rufer, Tal Joseph, Zara Aamer, and mechanical engineering professor Kripa Varanasi.
Traditional carbon capture systems typically rely on hydroxides that react with atmospheric CO2 to form carbonate. This carbonate solution is then fed into an electrochemical cell, where it reacts with acid to release pure carbon dioxide — suitable for fuel production or industrial use.
The challenge lies in the fact that both steps occur in the same liquid medium. The capture phase performs best in a hydroxide-rich environment, while the release phase needs a carbonate-rich one.
This creates a functional conflict: the system can’t operate both steps at their optimal levels simultaneously.
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To resolve this, the MIT team introduced a third step — nanofiltration. After CO2 is absorbed and converted to carbonate, the solution is passed through a membrane that separates ions by charge. Because carbonate ions have a -2 charge and hydroxide ions have a -1 charge, the membrane can effectively distinguish between them.
This separation allows the system to recycle hydroxide ions back into the capture phase, while sending carbonate ions forward for CO2 release. As a result, each stage can operate under ideal conditions, significantly improving overall performance.
This clever reengineering of the carbon capture cycle could represent a major step forward in scalable, cost-effective carbon removal technologies.
Read more: Researchers Find A New Energy-Efficient Method For Converting Captured CO2 Into CO
