Inorganic carbon formation in rotating thin liquid films to support algal growth

Abstract

This paper presents the results of testing a novel gas-to-liquid mass transfer unit for enhancing the transfer of carbon dioxide (CO2) into liquid media by reducing the mass transfer resistance through the formation of a thin liquid film on a rotating membrane. The initial (maximum) mass transfer rate of inorganic carbon into liquid was quantified when operating the mass transfer unit under three different CO2 concentrations in air (1%, 2%, and 10%), two membrane rotational speeds (70 rpm and 90 rpm), and two liquid media (deionized (DI) water and BG-11 algal growth media.) Results indicated that increasing CO2 concentration in the gas increased the inorganic carbon transfer rate into the liquid film as expected, but not linearly. Increasing the membrane's rotational speed resulted in increasing the inorganic carbon mass transfer rate as well. The use of BG-11 algal media as a liquid film instead of DI water increased the inorganic carbon mass transfer rate. CO2 volumetric mass transfer coefficients (kLa) were calculated and compared with conventional CO2 supply systems. Results indicated that the mass transfer unit can be used to supply inorganic carbon to the microalgal cultures with relatively high transfer rates.