COLLECTION OF LOW-CONCENTRATION AMMONIA A ND NITRIC-ACID GAS-USING A DIFFUSION SCRUBBER AND ITS APPLICATION TO THE SEPARATION OF PARTICULATE MATTER

A diffusion scrubber system equipped with an ion chromatograph (IC) wa s used for the collection and determination of gaseous NH3 and HNO3 at 100 similar to 200 ppb levels. Purified water was used as the absorbi ng solution of the scrubber. The gaseous HNO3 concentration was measur ed by the impinger trap-IC method and/or the reduction (to NOx)-chemil uminescence method. The gaseous NH3 concentration was measured by the impinger trap (boric acid solution)-IC method. The determined collecti on efficiencies were more than 97.4 % for HNO3 and more than 92.3% for NH3 under a relative humidity of 0 similar to 70%. The relative stand ard deviations were less than 1.1% (n=5) for successive collection and analysis. It was confirmed that this system can determine gaseous HNO 3 and NH3 correctly even in the presence of ammonium nitrate particles .