Enhancement of nitric oxide solubility using Fe(Ⅱ)EDTA and its removal by green algae Scenedesmus sp

A photoautotrophic cultivation of green algae Scenedesmus cells was used for the removal of nitric oxide (NO) from a model flue gas mixture. In an attempt to improve the solubility of NO in the culture broth, the addition of Fe(Ⅱ)EDTA to the cultivation was investigated. The addition of Fe(Ⅱ)EDTA greatly enhanced NO-dissolution in the culture broth and subsequently increased the algal-uptake of NO. NO was assimilated as a source of nitrogen for the growth of Scenedesmus cells since there was a steady increase in cell density with no other nitrogen source in the culture except the incoming NO. 40-45% of NO removal was maintained for more than 12 days with the addition of 5 mM Fe(Ⅱ)EDTA in a 1-L air-lift type photobioreactor system fed with 300 ppm of NO gas at a rate of 0.3 vvm. However, the NO-dissolution-enhancing capacity of Fe(II)EDTA did not reach its full potential due to its oxidation to Fe(Ⅲ)EDTA, possibly induced by molecular oxygen that evolved from algal photosynthesis, and subsequent loss of chelating capabilities.