The use of monoethanolamine and potassium glycinate solvents for CO2 delivery to microalgae through a polymeric membrane system

- The performance of a membrane system for delivering CO2 to microalgae was tested.
- CO2 was delivered to microalgae from monoethanolamine (MEA) and potassium glycinate.
- At low CO2 loading MEA permeated across the membrane and inhibited algae growth.
- Permeation of potassium glycinate across the membrane was less than that of MEA.
- Unlike MEA, permeated potassium glycinate did not appear to inhibit algal growth.

We have previously shown that a combined system involving solvent absorption, membrane desorption and microalgal cultivation can provide an effective approach to carbon dioxide capture and utilisation (Energy Environ. Sci., 2016, 9, 1074). In this article, we evaluate aqueous solutions of monoethanolamine (MEA) and potassium glycinate (PG) for membrane desorption of CO2, and compare these with our previous work using potassium carbonate (K2CO3). Enhanced growth of Chlorella sp. was observed with 20 wt% PG at 0.5 CO2 loading (moles of CO2 absorbed per mol solvent) relative to a baseline control in which carbon dioxide was only available from atmospheric diffusion. Similar growth rates to the control were observed for PG at 0.2 loading. For MEA, algal growth was accelerated at 0.5 loading but was inhibited at 0.2 loading. This was related to the volatile MEA crossing the membrane and poisoning the algae. Considering the kinetics of CO2 absorption into the solvent, the improvement of microalgal growth and the system stability in case of solvent leakage, amino acids such as PG are the ideal solvent for this application.

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