Effect of Acids on Water Vapor Uptake by Pyrogenic Silica

✍ Scribed by Anatoli Bogdan; Markku Kulmala

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 167 KB
• Volume: 191
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.4920

✦ Synopsis

dispersion of volcanic debris or other eolian soil dust (5). Effect of gaseous HCl and HNO 3 on the water vapor uptake The particles formed from combustion processes represent by pyrogenic silica was studied at different relative humidities agglomerates of the ultimate globular amorphous silica parti-( RH ) for pure water and different compositions of binary and cles (pyrogenic or fumed silica, SiO 2 ) with dehydrated hyternary vapor mixtures. Experiments showed that the ability of drophobic surface (6-9).

silica to uptake water strongly depends on RH and on the type

In the past decades interest in the atmospheric acids has of acids and their concentration in the vapor mixtures. At low grown considerably. Strong acids HCl and HNO 3 are inacid concentration in the binary mixtures the influence of acids volved in a number of environmental problems, ranging from is probably small. Water uptake by silica does not change monotonically with acid concentration: at first it decreases and then the ecosystem acidification to the stratospheric ozone deplestarts to grow. However, the presence of acids promotes water tion (10-12). The rates and mechanisms of scavenging reuptake, and the effect is very significant at low RH. HCl seems moval of acids are conditioned by complex microphysicoto be more effective acid to enhance water uptake than HNO 3 . chemical processes involving vapor acid concentration, In the case of ternary mixtures the adsorbed weight of water is cloud water and aerosol particles, that has important consea bit larger than that adsorbed from the binary mixtures. Acids quences for receiving ecosystem and waters (13). Unfortuare accumulated by silica surface, and the accumulation is larger nately, little is known how the fine aerosol particles adsorb for nitric acid.