Application of a microalga, Scenedesmus obliquus PF3, for the biological removal of nitric oxide (NO) and carbon dioxide

Abstract

Nitrogen oxide (NOx) emissions from flue gas lead to a series of environmental problems. Biological removal of Nitrogen oxide (NOx) from flue gas by microalgae is a potential approach for reducing the problems caused by these emissions. However, few microalgal strains are reported to remove NOx from flue gas. Here, a microalga strain PF3 (identified as Scenedesmus obliquus), which can remove NOx and fix CO2 from flue gas is isolated. The tolerance of Scenedesmus obliquus PF3 to CO2, NO, SO2 and its adaptabilities to environmental factors (pH and temperature), and its performance in the removal of NO and CO2 are investigated. Scenedesmus obliquus PF3 showed biomass accumulation when sparged with 15% CO2 or 500 ppm NO or 50 ppm SO2, and bisulfite less than 2 mM showed no toxicity to Scenedesmus obliquus PF3. Additionally, PF3 grew well in a wide range of pH and temperatures from 4.5 to 10.5 and 15 °C–30 °C, respectively. When sparged with simulated flue gas (100 ppm NO, 10% CO2, (N2 as balance gas)), the microalgae culture system removed NO and CO2 at a rate of 2.86 ± 0.23 mg L−1 d−1 and 1.48 ± 0.12 g L−1 d−1, respectively, where up to 96.9 ± 0.03% (2.77 ± 0.08 mg L−1 d−1) and 87.7 ± 6.22% (1.29 ± 0.01 mg L−1 d−1) of the removed NO and CO2, respectively, were assimilated in algal biomass. These results suggest that Scenedesmus obliquus PF3 is a promising candidate for NOx removal and carbon fixation of flue gas.