Reduction kinetics of Fe(III)NTA chelate by sulfite

Kinetics of the reduction of Fe(III)NTA (ferric ion coordinated to nitrilotriacetic acid) by sulfite were studied experimentally in aqueous solutions at 40-60°C and pH = 3.8-8.3. The reaction had been claimed to be a regeneration step of Fe(II) in the absorption of nitric oxide into aqueous solutions containing Fe(II)NTA and sulfites. The reaction rate could be expressed as first-order with respect to the concentration of Fe(III)NTA and of order minus one with respect to the concentration of Fe(II)NTA. The order of reaction with respect to HSO^?₃ was determined to be unity when the molar ratio of Na₂SO₃ to Fe(III)NTA was less than 5.