Amino Acid-Salt-Based Complex Absorbents for CO2 Capture in a Membrane Contactor

Phosphate or borate as an activating agent was added into the aqueous glycinate to form amino acid salt-based complex absorbents. Capture of CO 2 by the complex absorbents was studied theoretically and experimentally using a hollow fiber membrane contactor. Reaction mechanism concerning the activation effect of phosphate and borate was presented theoretically. A mathematical model was developed to simulate mass transfer of the membrane contactor. The effects of absorbent and gas CO 2 concentrations on mass transfer flux and CO 2 capture efficiency were investigated. Surface tension of the complex absorbents and operational stability of the membrane contactor were also discussed in this work. Results show that the activation follows the sequence B 4 O 7 2− > PO 4 3− > HPO 4 2− > H 2 PO 4 − . The mathematical model was validated by comparing theoretical with experimental data. The mass transfer flux increased almost linearly with the increase of gas CO 2 concentration. Surface tension data revealed that the complex absorbents could not wet the membrane micropores. The flux was basically kept constant during the prolonged period of operation. The complex absorbents modified by the phosphates and borates are good potential absorbents for CO 2 capture.