SIMULTANEOUS ABSORPTION AND OXIDATION OF NO AND SO2 BY AQUEOUS SOLUTIONS OF SODIUM CHLORITE

Abstract

Complete and simultaneous removal of NO and SO2 is achieved in a laboratory bubble column reactor at about room temperature using aqueous solutions of NaClO2 buffered with Na2HPO4and KH2PO4The influence of reaction medium chemistry (pH and concentrations of buffer and NaOH) on NOx and SO2 removal efficiencies was also evaluated. The buffered NaClO2 solution is determined to be more effective in absorbing NOx and SO2 and in controlling chlorine dioxide (ClO2) leakage. The presence of SO2 greatly reduces the scrubbing solution absorption rate for NO as evidenced by shorter breakthrough times, irrespective of the absorbent solution used. The scrubbing solution pH is determined to be very critical in the simultaneous absorption and oxidation of NO and SO2. NO2 control is enhanced significantly as the buffer concentration increases from 0.1 M to 0.5 M, with no NO2 detected in the effluent gas at buffer concentration levels ≥ 0.5 M. Optimal removal efficiencies were observed at the following conditions: 6 < pH < 7; NaClO2 concentration < 0.1 M; and buffer concentration > 0.1 M. Material balances, determined using ion chromatograph, show that the only anions in solution at NOx and SO2 breakthroughs are NO3 −, SO4 2−, PO4 3− and Cl− and account for all nitrogen and sulfur that entered the scrubber as NO and S02.