The use of monoethanolamine and potassium glycinate solvents for CO 2 delivery to microalgae through a polymeric membrane system

Abstract

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 for membrane desorption of CO 2 , and compare these with our previous work using potassium carbonate. Enhanced growth of Chlorella sp. was observed with 20 wt% potassium glycinate at 0.5 CO 2 loading (moles of CO 2 absorbed per mol solvent), while similar growth rates to the control were observed 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 CO 2 absorption into the solvent, the improvement of microalgal growth and the system stability in case of solvent leakage, amino acids such as potassium glycinate are the ideal solvent for this application.

Enhanced CO2 bio-utilization with a liquid–liquid membrane contactor in a bench-scale microalgae raceway pond

“…With HFMs continuously delivering CO 2 from the solvent to the culture, the pH in the medium was lower than that in the other trials (Figure 4(a)) due to the CO 2 supply exceeding the demand; consistent with our earlier work [15,31]. In particular, on the first day when the biomass concentration was low, the excessive CO 2 transferred to the algae medium led to an acidic environment.…”

“…During microalgae cultivation, pH and temperature were in-situ measured by a pH meter (S220 Eqn. 9, where is the partial pressure difference between the solvent and culture medium ∆ 2 (Pa), which was determined in our previous study [31].…”

“…CO 2 molecules were released by the buffer solution and transferred across the polyethylene to promote the growth of cyanobacteria in a 50 mL flask. In our own work, we have transferred molecular CO 2 from a solvent such as potassium carbonate or potassium glycinate to a microalgae broth by using microporous hollow fibre membranes which are coated with a nonporous polydimethylsiloxane layer [15,16].…”

The effects of medium salinity on the delivery of carbon dioxide to microalgae from capture solvents using a polymeric membrane system

“…In our previous work, we modified an approach originally developed by Noel et al(Noel et al 2012;Chance et al 2015) to address these problems (Zheng et al 2016;Zheng et al 2017). In this system, CO2-loaded solvents are passed through the inside of a non-porous polymeric membrane allowing the CO2 stored in the solvents to cross the membrane, dissolve in the medium and become the carbon source for the microalgae (see Figure 1).…”

“…This approach integrates CO2 capture via chemical absorption, membrane separation and microalgae cultivation technologies, and eliminates both the energy consumption of gas compression and transportation, and the energy penalty for regeneration of the capture solvent. The system has been shown to be effective for a range of CO2 capture solvents including potassium carbonate (K2CO3), monoethanolamine (MEA) and potassium glycinate (PG) (Zheng et al 2017). However, to date the system has only been tested on a marine strain of Chlorella sp., and it is not clear how the performance will be affected by the low salinity media required for fresh water microalgae.…”