How the sulfur dioxide in the flue gas influence microalgal carbon dioxide fixation: From gas dissolution to cells growth

Aiming at realizing efficient microalgae-based CO₂ sequestration from coal-fired power plants, this study investigated the interaction between the mass transfer of SO₂-contained flue gas and microalgae growth. The results indicate that the CO₂ dissolution in microalgae suspension and the growth of Chlorella vulgaris could be hindered by solution acidification and oxidative molecular species produced in the conversion of bisulfite to sulfate. With the SO₂ concentration increased from 0 to 400 ppm, the pH of the culture medium decreased from 7 to 2, and the SO₄²⁻ concentration reached 1 g L⁻¹, resulting in a decrement of 18.1% in the CO₂ dissolution rate. Moreover, the Chlorella cells could only maintain their growth within the SO₄²⁻ concentration of 800 mg L⁻¹ accompanied by a decrement of 58% in maximum biomass concentration. The cultivation collapsed under excessive SO₂ (over 400 ppm) as the plasmolysis and chloroplast decomposition occurred which severely inhibited the microalgal photosynthesis. This work provides a guide to cultivating microalgae using real flue gas.