Abstract
Abstract Laboratory experiments were conducted to investigate interactions between complex air mixtures and aqueous films containing hydrolysis products of hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) oxidation products. The experiments consisted of exposing aqueous films mixtures of NH 4 NO 3 , H 2 O 2 and either NaF or NaCF 3 COO on stainless steel panels to irradiated o -xylene/NO x /SO 2 /air mixtures. The complex air mixtures and exposed films were chemically analysed. Aliquots of the exposed films were then allowed to evaporate, after which the chemical composition of the remaining residual salt was determined. The data were used to determine how the chemical composition of the film influenced (1) the deposition of components of the complex air mixture to aqueous films and (2) the fate of film constituents during evaporation. For small H 2 O 2 loadings the SO 2 deposition was limited by the available oxidant. However, for the higher loadings, the uptake data were consistent with control by gas-phase mass transfer. Effective aqueous film deposition velocities for HCHO and CH 3 COCHO were 0.37 and 0.67cms −1 , respectively. The evaporative anion loss data suggest that NO3 3 − , NO 2 − , F − , HCOO − and CF 3 COO − were lost by evaporation of the corresponding acid. However, the possibility of other CF 3 COO − reactions occurring during evaporation could not be eliminated. The laboratory results show that depositions of HCFC and HFC oxidation products to acidic aqueous media that can undergo evaporation may not always serve as permanent sinks.
Published Version
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