大気汚染物質除去に関する研究 : (5) NaClO_2,NaOH 水溶液による希薄 NO_x の吸収

Abstract

The absorption of such lean NOx as encountered in flue gases in aqueous mixed solutions of NaClO_2 and NaOH was carried out using a stirred vessel with a plane interface at 25℃ and atmospheric pressure. The rate of NO_2 absorption was analyzed by the chemical absorption theory under the fast-reaction regime. The reaction prevailed was found to be the parallel reactions involving oxidation and hydrolydrolysis, and to be second-order with respect to NO_2. The second-order rate constant for the hydrolysis was evaluated as 3.09×(10)^8 L/mol s. The order of reaction relative to ClO^-_2 was derived unity for the chlorite concentration greater than 1.0 molar. The third-order rate constant for the oxidation was derived as 7.32×(10)^8 (L/mol)^2/s at [NaOH]=0.20 molar. For the absorption of NO, there appears a gradual jump in absorption rate at the interfacial concentration of NO ranginging from 5×(10)^<-7> to 2×(10)^<-6>mol/L. Above this transition region, the order of reaction in NO approaches 2,whereas below the transition region, the order of reaction becomes unity.