NOx removal in chemical absorption-biological reduction integrated system: Process rate and rate-limiting step

Biological reduction of Fe(III)EDTA is considered as the key step that limits the removal efficiency of the chemical absorption-biological reduction integrated system. In this study, the process rates of each reaction step under typical conditions (T = 50 °C, CFeII(EDTA) = 1-5 mmol/L, CNO = 0-500 ppm, CO2 = 1-10%, pH = 7) were determined. Relevant kinetic constants including rate constants of absorption part and Michaelis-Menten kinetic constants of regeneration part were also obtained. On this basis, the theoretical process rates of each reaction step were predicted and compared in a steady state. The results confirmed that the removal rate of NO in this system is limited by the biological reduction of Fe(III)EDTA. Moreover, it indicated that increasing the concentration of total iron appropriately could enhance the bioreduction of Fe(III)EDTA.