ABSORPTION OF NO IN AQUEOUS-SOLUTIONS OF FE(II)NTA - DETERMINATION OFTHE EQUILIBRIUM-CONSTANT

Valid alternatives to the selective catalytic reduction (SCR) process for the removal of nitrogen oxides from waste gases (denoxing) may be found in wet scrubbing processes where the low solubility of NO in aqu eous media is enhanced by the application of chelate complexes. The mo st widely used complex for this purpose is Fe(II)EDTA (iron(II) ethyle nediaminetetra-acetic acid). Iron(II) nitrilotriacetic acid (Fe(II)NTA ) might be another candidate, with similar chemical properties as Fe(I I)EDTA but available industrially at a considerably lower price. For t he development of technical processes, a knowledge of the equilibrium data over a range of temperature is of prime importance. Therefore exp erimental investigations were carried out concerning the chemical equi librium of the reaction: NO + Fe(II)NTA reversible arrow Fe(II)NTA . N O The equilibrium constant was determined in the temperature range 22- 80 degrees C. All experimental data fit the equilibrium constant equat ion well: K-p = 3.05 x 10(-8) exp(7332/T) (bar(-1)) The equilibrium co nstant for Fe(II)NTA is approximately 25% lower than the constant for Fe(II)EDTA. However, considering the price difference between the two complexants, Fe(II)NTA is an interesting alternative to Fe(II)EDTA.