Assessment of the photocatalytic transformation of pyridinium-based ionic liquids in water

Photochemical Transformation of Four Ionic Liquid Cation Structures in Aqueous Solution

“…The fact that the three other IL cations all have smaller k i ,HO • -values than the smallest imidazolium cation suggests that reactions with hydroxyl radicals might occur both at the side chain and the ring in the case of imidazolium cations. In agreement with our findings, reaction products identified for N -alkylpyridinium cations under photocatalytic conditions with TiO 2 were predominantly side-chain hydroxylations …”

“…In agreement with our findings, reaction products identified for N-alkylpyridinium cations under photocatalytic conditions with TiO 2 were predominantly side-chain hydroxylations. 32 While bimolecular reaction rate constants determined by Calza and co-workers for C 2 -imidazolium (2 × 10 10 M −1 s −1 ) 16 and C 4 -pyridinium (3 × 10 8 M −1 s −1 ) 17 with hydroxyl radicals are in agreement with our results, considering experimental uncertainties, other studies using H 2 O 2 and UV-irradiation or Fenton reactions have observed very different trends in reactivity of imidazolium toward hydroxyl radicals. Siedlecka and Stepnowski 33 and Stepnowski and Zaleska 34 have investigated the removal rates of C 4 -, C 6 -, and C 8 -imidazolium in Fenton and UV/H 2 O 2 systems, respectively, and observed increasing removal with decreasing side-chain length.…”

Photostability and photocatalytic degradation of ionic liquids in water under solar light

“…However, to the best of our knowledge, neither the stability not the photocatalytic degradation of ILs in aqueous solution under solar light have been studied in the literature so far. Recently, Calza et al 35 reported on the photocatalytic degradation of pyridinium-based ionic liquids in water but under UV irradiation. They analysed the effect of the length of the alkyl chain, the kind of inorganic anion and the type of substituents.…”

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

“…When TiO 2 P-25 is added as a photocatalyst, aqueous solutions of the ILs at 20 mg/L were degraded in 600 min by irradiation with a Xe lamp (450 W/m 2 ). Even more extended decomposition is observed when light sources with high UV power are used. − …”