To Net Zero… and Beyond!
Tanay N -
Shoutout P.F. Chang’s at the LAX airport for the quiet spot to write this post. By the time you are likely reading this, however, I’m outside the 137-year-old Sagrada Família church in Barcelona, Spain! Regardless, carbon capture science is too exciting not to work on during a layover, so here we go!
In one of my previous blog posts, I briefly discussed an aqueous version of Lemon, one that would involve an extensive understanding of acid-base chemistry. So, I would like to give a brief summary of the intermediary reactions that would be involved in such a process, assuming Calcium hydroxide is still our sorbent.
What I’ve Learned
Calcium carbonate, the product, is a precipitate, meaning it does not dissolve in water. However, the reactant, Calcium hydroxide, does dissolve in water. This allows for a cleaner separation and easier calculation when looking at how much CO2 was removed from the air, because in the non-dissolved version of Lemon, the Calcium hydroxide and Calcium carbonate are both mixed together, so you have to do many conversions which can lead to error. Additionally, since the Calcium hydroxide sorbent is dissolved, it increases the surface area to which CO2 can react with, which can also increase yields.
Below are some notes I took on the specific strong base-weak acid titration.
Calcium carbonate is a weak base, meaning the resulting solution is alkaline (pH > 7). What’s interesting is that in my research, one paper mentioned that the rate of product formation drops sharply once the pH shifts from 12 and hits 10. This is because, as you can see in the notes, H2CO3 is created as an intermediate, which dissociates into H(CO3)- & H+, which creates a slightly acidic mixture. This increase in acidity shifts equilibrium left to favor the reactants of our intermediate reaction involving H2CO3 (this has the consequential effect of favoring the formation of Ca(OH)2 as well, but after some more time, CO2 capture begins again, albeit slowly until pH reaches around 6. The way I like to think about it is a rocking ship; in our case, the ship is almost falling over on the right side, so it must reorient itself by putting more weight (reactant) on the left, resulting in smooth sailing (CO2 capture starts again but slowly).
What I’ve been working on
I’ve also been going through the list of sorbents my faculty mentor Ms. Holtzman has given me, and to be completely honest, so far most of the potential products could lead to a myriad of health problems if not conducted safely. However, I have not lost hope, and I will continue until I have exhausted the list!
I’ve also just finished my laboratory procedural trainings, and I hope to start at the Center for Negative Carbon Emissions (CNCE) by the 17th!
Furthermore, to better understand Moisture-Swing technologies before I start at the CNCE, I’ve been reading into Ion-Exchange Resins (IER) which absorb CO2 in dry conditions and desorb in wet conditions because of a chemical structure change. The specific structure change in regard to ammonium-based sorbents is what I’m currently investigating. I’ll provide a brief summary in a later blog post.
Once again, I’d like to thank Ms. Holtzman and Dr. Green for their gracious support in guiding me through my research, helping spread environmental stewardship and further carbon capture efforts. It’s been a pleasure writing for you all these past few weeks, and I anticipate constant progress in terms of tackling any challenges that come up along the way; I’m excited to see what’s in the future, especially in regards to the final presentation and the results of my research.
I’m beyond grateful for you all taking the time to read these posts!
– Tanay 🙂
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