Photoinduced Transformation of Pyridinium-Based Ionic Liquids, and Implications for Their Photochemical Behavior in Surface Waters

Paola Calza, Giorgio Noè, Debora Fabbri, Valentina Santoro, Claudio Minero, Davide Vione, Claudio Medana

Water Res. 2017 Oct 1;122:194-206.

PMID: 28601032

Abstract:

The photochemical reactivity of three ionic liquids (1-ethylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium tetrafluoroborate, and 1-(3-cyanopropyl)pyridinium chloride) was studied by combining laboratory experiments and photochemical modeling, to get insight into the possible behavior in surface-water environments. Among the studied compounds, phototransformation in sunlit surface waters could be an important attenuation pathway for 1-butyl-4-methylpyridinium tetrafluoroborate (BMPOTFB). In this case the reaction with the carbonate radicals (CO3-) would prevail at low values of the dissolved organic carbon (DOC), while the direct photolysis would be important at intermediate to high DOC values. The sensitization by the triplet states of chromophoric dissolved organic matter could play a significant role at high DOC, especially in the presence of a considerable fraction of highly photoreactive pedogenic organic matter derived from soil runoff. The main processes that account for the phototransformation of BMPOTFB and produce the main detected transformation products (TPs) are hydroxylation, detachment/shortening of the butyl chain and double bond formation. Interestingly, there is a considerable overlap between the TPs formed by direct photolysis and those produced by indirect photochemistry. Some of the TPs formed from BMPOTFB are more toxic than the parent compound towards Vibrio fischeri bacteria, and account for the increase in toxicity of the irradiated mixtures. Differently from BMPOTFB, in the case of the other two studied ionic liquids the photodegradation would play a negligible role in environmental attenuation, with the possible exception of very shallow waters with low DOC.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP350481	1-Ethylpyridinium tetrafluoroborate		350-48-1	Price
AP820972347	1-(3-Cyanopropyl)pyridinium chloride		820972-34-7	Price