The absorption of lean NO (200 similar to 1000 ppm) gases in aqueous NaClO2 solution was investigated in both a mechanically stirred vessel and a packed tower. The chemical reaction rate btween NO and NaClO2 in alkaline solution was shown to be second-order with respect to NO concentration and first-order to NaClO2 concentration. After including mass transfer considerations, the absorption rate equation established in this work (under the condition of NaClO2 concentration less than 1.0 M and temperature at 30 degrees C) is given as: R-A = P-A (682 x 10(5) + 1/2.97 x 10(-2) {[NO](i)[NaClO2](0)}(1/2))(-1) (moles/sec cm(3)) In addition, a robust design method was also used to study the performance of this de NOx process by NaClO2 solution in a packed tower. SIN analysis of the results indicated that the pH of liquor, NaClO2 concentration and NaOH concentration were the major factors in affecting both NO oxidation and absorption efficiencies.