Dripping Acid

Now that I have your attention, I’ll sum up the past couple weeks of research:

We’ve equilibrated resin with streamwater, and collected streamwater that still needs to be equilibrated. The next step is to knock off the ions that the cation exchange resin is holding, so that we can analyze them. To do this, we drip acid through the resin, and then analyze it. Sodium is the first ion to be removed from the resin, due to its relatively weak charge, so we only need to collect the first ~350mL of post-drip. Given, the peristaltic pump goes at 1mL/min, so it’s a lengthy process.

Today, we’re performing a mini experiment to examine if acid diluted with mostly methanol removes the ions more efficiently than acid diluted with water. If it does perform more efficiently, it will speed up some parts of our research, such as the evaporation of the post-drip acid.

Maybe I’m impatient, but it’s amazing how everything in research takes a long time. For example, we have to pump 90L of water through resin at a rate of 4.3 ml/min. If you do the math, that’s two weeks. Before this summer, I was under the impression that technology is making everything that humans do move faster. And it does. However, when it comes to chemistry and Earth processes, some things can’t change. Like the hydraulic conductivity of resin. What’s impressive is that we are able to analyze the ions in streamwater, and eventually find out how old the water is. So as I sit here, watching acid drip, I realize that I’m probably one of those millenials who’s used to instantaneous results. At least I can look outside to see kids in tour groups playing Pokemon Go.


  1. kmnelsen says:

    Hi Kira! This seems like a really cool project even though it is a slow processes. Using cation exchange to date how old water is sounds interesting. It always amazes me how many applications simple chemistry that we learn in Gen Chem can have. I may have missed this in previous post but what acid are you using to run through you resin? Good luck catching all the ions!

  2. rjdirisio says:

    Hey Kira, I was wondering what the rationale for using methanol instead of water is. Methanol is a less polar solvent, about half as polar as water is. Wouldn’t you expect cations to be more attracted to water, and therefore dissolve more readily? Have you thought about using other polar solvents like acetonitrile? I would assume you must be careful not to dissolve the resin itself as well.

  3. mescreen says:

    Hello Kira! Your research sounds very exciting though it is tedious. I have also come to the same conclusion as you this summer. Even though technology helps with our methods, research takes patience and determination. It is amazing how many work hours can be boiled down into one final result.

    Your study of ions in groundwater also reminds me how connected all the sciences are. I love how all the disciplines contribute to one another and enhance understanding. Sometimes this deeper meaning is lost when one gets too isolated in their discipline. Have your results so far supported your hypothesis? How are you evaporating your post-drip acid? Good luck with your future results!

  4. kmholmes01 says:

    Hi Megan! So far we do not have any actual results, due to the speed of the process and the Millington to ISC move. As far as the evaporation goes, we have our post-drip acid in 50mL vials, and then just put them under the hood until they evaporate down. Soon we are going to start adding some heat to these samples to speed up the process.

  5. kmholmes01 says:

    Hi Ryan! So we’re not entirely sure why it is that the methanol works better. A paper from the 1950s found this result with no real explanation. The advantage that we found to it is that the Sodium comes off the resin somewhat quicker than with the water solution. However, potassium takes longer to come off the resin. This is beneficial since the potassium will mess with our results in the gamma analysis lab. Really the largest benefit is that it evaporates so much quicker than water. Given that we have to evaporate ~400ml of acid down to ~12ml for the gamma analysis, the methanol is a big help!

  6. kmholmes01 says:

    Hi! we are using 1 and 2 molar HCl.