Original Articles

• Published in: Ozone: science & engineering Vol. 37; no. 5; pp. 393 - 404
• Main Authors: Reisz, Erika, Naumov, Sergej, Schmidt, Winfried, Sonntag, Clemens von
• Format: Journal Article
• Language: English
• Published: 01-01-2015
• ISSN: 0191-9512; 1547-6545
• DOI: 10.1080/01919512.2015.1041583

Ozone reacts slowly with Ag super(+) (circumneutral pH, k = (11 plus or minus 3) 10 super(-2) M super(-1) s super(-1)). After some time, ozone decay kinetics may suddenly become faster with the concomitant formation of silver sol. As primary process, an O-transfer from O sub(3) to Ag(I) is suggested, whereby Ag(III) is formed [Ag super(+) + O sub(3) + 2 H sub(2)O arrow right Ag(OH) sub(3) + O sub(2) + H super(+)]. This conproportionates with Ag(I), which is in large excess, leading to Ag(II) [Ag super(+) + Ag(OH) sub(3) [rlarr2] 2 Ag(OH) super(+) + HO super(-)]. Further, Ag(II) reacts with ozone in a high exergonic reaction [Ag(OH) super(+) + O sub(3) arrow right Ag + 2 O sub(2) + H super(+)], where ozone acts as a reducing agent. Thereby, a single silver atom, Ag, is formed that can be oxidized by O sub(2) and O sub(3) or can aggregate to a silver sol. Aggregation slows down the rate of oxidation. When Ag super(+) is complexed by acetate ions, ozone decay and silver sol formation are speeded up by enhancing Ag(II) formation [Ag(I)acetate + O sub(3) arrow right Ag(III)acetate arrow right Ag(II) + CO sub(2) + times CH sub(3)]. In the presence of oxalate, the formed complex reacts faster with ozone than Ag super(+), and Ag(III)oxalate decarboxylates rapidly [Ag(I)oxalate + O sub(3) arrow right Ag(III)oxalate arrow right Ag super(+) + 2 CO sub(2)]. This enhances ozone decay but prevents silver sol formation. Quantum chemical calculations have been carried out for substantiating mechanistic suggestions.