The oxidation product (NO3−) of NO pollutant in flue gas used as a nitrogen source to improve microalgal biomass production and CO2 fixation

Abstract

In order to eliminate the inhibition effect of the toxic nitric oxide (NO) in flue gas on microalgal growth and CO₂ fixation, NO was converted by a wet UV/H₂O₂ method to produce nitrate (NO₃⁻), which then be used as a nitrogen source for microalgae to improve its growth. The growth ability and biomass compositions of the microalgae cultivated with the produced NO₃⁻ from NO gas were similar to those of the microalgae cultivated with equivalent moles of commercial NaNO₃. The NO₃⁻ concentration produced from NO increased with UV lamp power, H₂O₂, and NO concentrations, resulting in an improved microalgal growth. The concentration of NO₃⁻ from 500 ppm NO wet-oxidized by 6% (v/v) H₂O₂ and 55 W UV light was up to 8.8 mM. When the produced nitrate was used as supplementary nitrogen source, the maximum growth productivity of Chlorella PY-ZU1 at 15% (v/v) CO₂ reached 1.18 g L⁻¹ per day (0.97 times higher than that cultivated with the standard medium). The peak fixation efficiency of 15% (v/v) CO₂ was 69.6% (1.13 times higher than that cultivated with the standard medium).