A novel magnet-driven rotary mixing aerator (MDRMA) was proposed to reduce the diameter and rising rate of bubbles while improving CO2 mass transfer during microalgae growth in a column photobioreactor. Visualization results showed that the bubble number density increased significantly with the increasing rotation rate of MDRMA. As the rotation rate increased from 0 to 300 r min-1, the average bubble diameter decreased from 3.8 mm to 2.0 mm (47.4% reduction), while the corresponding average bubble rising rate decreased from 0.32 m s-1 to 0.22 m s-1 (31.3% reduction). Notably, when the rotation rate of MDRMA exceeded 300 r min-1, a significant number of microbubbles with diameters below 0.5 mm were generated. When synthetic flue gas containing 12% CO2 (v/v) was supplied for microalgae cultivation, a maximum biomass concentration of 1.75 g L-1 was obtained with rotating MDRMA at 200 r min-1, showing a 57.7% increase compared to the control aerated with a silicone tube aerator. Meanwhile, the pigment content reached 14.48 mg L-1, 22.7% higher than that of the control.
Keywords: Bioreactor; Carbon fixation; Gas bubble; Magnet-driven rotary mixing aerator; Microalgae.
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