Collection of low-concentration ammonia and nitric acid gas using a diffusion scrubber and its application to the separation of particulate matter

Abstract

A diffusion scrubber system equipped with an ion chromatograph (IC) was used for the collection and determination of gaseous NH₃ and HNO₃ at 100200 ppb levels. Purified water was used as the absorbing solution of the scrubber. The gaseous HNO₃ concentration was measured by the impinger trap-IC method and/or the reduction (to NO_x)-chemiluminescence method. The gaseous NH₃ concentration was measured by the impinger trap (boric acid solution)-IC method. The determined collection efficiencies were more than 97.4% for HNO₃ and more than 92.3% for NH₃ under a relative humidity of 070%. The relative standard deviations were less than 1.1% (n = 5) for successive collection and analysis. It was confirmed that this system can determine gaseous HNO₃ and NH₃ correctly even in the presence of ammonium nitrate particles.