Question

Currently, I am working on a project where we are using pressure degassing. The idea is to make a test setup where we lower the pressure in a flask to 'degas' the solution. The solution is just distilled water, but we plan on doing other water samples later on. The background of this project is associated with carbon capture from seawater, so we want to lower the pressure to a point where a lot of the carbon dioxide concentration in the water is moved to the gas part of the flask.

Given that we start at room temperature, and we don't want to remove ALL the carbon from the solution (due to marine life), what minimal pressure (or pressure drop in comparison with ambient pressure) would be recommended for this experiment?

Relevant papers are also very much welcome,

Thanks in advance!

Answer 1

The minimal pressure recommended for degassing a solution while preserving some carbon dioxide for marine life is slightly above 0.03 atm, considering the equilibrium vapor pressure of water at room temperature. The vapor pressure will vary based on temperature and the solution's salinity, requiring adjustments to maintain ecological balance. Dalton's Law of partial pressures is important for accurate measurement of gas concentrations.

Step-by-step explanation:

To determine the minimal pressure for degassing a solution without removing all of the carbon dioxide, particularly in the context of a project related to carbon capture from seawater, one needs to consider the properties of the gases and the solution involved.

Since we are discussing lowering the pressure in a flask to move carbon dioxide from the solution (distilled water initially, but seawater in the future) into the gas phase.

We need to find a pressure low enough to significantly reduce the dissolved carbon dioxide but not so low as to harm marine life by removing too much CO2.

According to available data, at approximately 0.03 atm (22.6 mmHg) we have an equilibrium of water vapor at room temperature. As carbon dioxide has a higher solubility than nitrogen or oxygen in water.

Reducing the pressure to somewhat above 0.03 atm may encourage the release of carbon dioxide while maintaining enough for aquatic organisms. However, the exact pressure may vary based on temperature and the saline content of the water.

It is important to consider the vapor pressure of water when degassing solutions. The vapor pressure of pure water at 25°C is 23.8 mmHg.

With seawater containing salts like NaCl, which lower the vapor pressure of water, degassing would require adjustments based on the vapor pressure at the given temperature and solution concentration.

Remember that application of Dalton's Law of partial pressures is crucial when determining the concentration of gases after the degassing process.

Increased accuracy in measurements can be achieved by accounting for the vapor pressure of water in your gas collection method.

Moreover, it is essential to continuously monitor and control the pressure applied to ensure that the desired balance between gas removal and ecological considerations is maintained.