A novel magnet-driven rotary mixing aerator for carbon dioxide fixation and microalgae cultivation: Focusing on bubble behavior and cultivation performance

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. •A magnet-driven rotary mixing aerator was proposed to enhance CO2 fixation.•The aerator can reduce the bubble diameter and rising rate by rotating flow field.•The bubble diameter and rising rate decreased by 47.4% and 31.3% at 300 r min−1.•Microalgal biomass production and pigment cumulation increased by 57.7% and 22.7%.