Atmospheric CO₂ capture for the artificial photosynthetic system

The aim of these studies is to evaluate the ambient CO₂ capture abilities of the membrane contactor system in the same conditions as leafs, such as ambient temperature, pressure and low CO₂ concentration, where the only driving force is the concentration gradient. The polysulfone membrane employed was made by a phase inversion process and characterized by ESEM micrographs which were used to determine the thickness, asymmetry and pore size. Besides, the porosity of the membrane was measured from the membrane and polysulfone density correlation and the hydrophobicity was analyzed by contact angle measurements. Moreover, the compatibility of membrane and absorbent was evaluated, in order to exclude wetting issues by meaning of swelling, dynamic contact angle and AFM analysis. The prepared membranes were introduced into a cross flow module and used as contactors between CO₂ and the absorbing media, a potassium hydroxide solution. The influence of the membrane thickness, absorbent stirring rate, solution pH and absorption time on CO₂ capture were evaluated. Absorbent solution stirring rate showed no statistically significant influence on absorption. We observed a non-linear correlation between the capture rate and the increase of absorbent solution pH as well as absorption time. The results showed that the efficiency of our CO₂ capture system is similar to stomatal carbon dioxide assimilation rate, achieving stable value of 20μmol/m²·s after 1h of experiment.