Photolysis of polyphosphate ions in alkaline aqueous solution

Abstract

Photolysis of pyrophosphate and tripolyphosphate ions in aqueous solution is proposed to produce electron detachment with formation of pyrophosphate and tripolyphosphate radicals (with quantum yields Ͻ0.1 at 266 nm), respectively. Formation of P 2 O 7 и 3Ϫ is observed after photolysis of both polyphosphate ions, because the decomposition of P 3 O 10 и 4Ϫ yields P 2 O 7 и 3Ϫ . The latter radicals further react with hydroxyl ions (k ϭ 1.4 ϫ 10 6 M Ϫ1 s Ϫ1 ) generating HOи radicals. The reaction of the solvated electrons with molecular oxygen produces O 2 и Ϫ . The rate constants for the reaction of SO 4 и Ϫ radicals with P 2 O 7 4Ϫ and P 3 O 10 5Ϫ were also measured.

Reactions of phosphate radicals with substituted benzenes. A structure–reactivity correlation study

“…The calculated wavelength independent constant b linearly increases with the substrate concentration (Fig. 1), as expected for the reaction of with the substituted benzenes [reaction (3)]. The HPO 4 ~ṽery small constant term c can be associated to the absorption of a longer lived species, mainly organic radicals, formed following phosphate radicals depletion.8…”

“…3) is coincident, within the experimental error, with the ratio of 2k/e(390 nm)/ 2k/e(300 nm), both absorption bands should correspond to the same transient species. The absorption coef-Ðcients of the transient can be estimated from experiments performed in the presence and absence of chlorobenzene under otherwise identical experimental conditions, on the assumption that the same amount of radicals are HPO 4 ~formed in all the experiments and that they are mainly consumed by reaction (3). Taking 510 nm) \ 1550 e(HPO 4 ~~, M~1cm~1,2 the concentration formed after photoly-HPO 4 ~sis for typical experiments is B(2.4 ^0.4) ] 10~7 M. Thus e(300 nm) \ 5300 ^900 M~1 cm~1 and e(400 nm) \ 1600 ^200 M~1 cm~1 are obtained for the organic transient.…”

“…(1).2 Phosphate radicals are efficient oxidants and can thus initiate the oxidative degradation of many organic substrates. 3 The study of their aqueous phase reactions is therefore of importance for the understanding of natural and industrial processes leading to the elimination of contaminants present in the aqueous systems in our environment ~~, added organic substrates was shown to yield information on the absolute rate constant for the reactions of these radicals with the substrates.3 Thus, the reactions of with HPO 4 ~phenol, Ñuorobenzene, chlorobenzene, bromobenzene, iodobenzene, benzonitrile, tert-butylbenzene and anisole were studied by Ñash-photolysis of peroxodiphosphate solutions of pH 7.1 containing variable concentrations of the aromatic substrates.…”