Oxidation of substituted triazines by sulfate radical anion (SO) in aqueous medium: a laser flash photolysis and steady state radiolysis study

Abstract

Laser flash photolysis has been used to determine the bimolecular rate constants and the spectral nature of the intermediates obtained by the reaction of sulfate radical anion (SO S 4 ) with 1,3,5-triazine (T), 2,4,6-trimethoxy-1,3,5-triazine (TMT), 2,4-dioxohexahydro-1,3,5-triazine (DHT), and 6-chloro N-ethyl N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine, AT). The rate constants determined were in the range 4.6 T 10 7 -3 T 10 9 dm 3 mol S1 s S1 at pH 6. The transient absorption spectra obtained from the reaction of SO S 4 with T, TMT, DHT and AT has an absorption maximum in the region 320-350 nm and was found to undergo second-order decay. The intermediate species is assigned to N-yl C(OH) radical of T (TOH ), carbon centered neutral radical of TMT, an OH-adduct of AT and an N-centered radical in the case of DHT. The interpretations on the experimental results obtained from TMT are supported by DFT calculation using Gaussian 03. Steady state radiolysis technique has also been used to investigate the degradation of AT induced by SO S 4 . The degradation profile indicated that about 99% of AT has been decomposed after an absorbed gamma-radiation dose of 7.5 kGy. The degradation yield of AT (expressed as G(-AT)) was found to be 0.26 m mol J S1 . The degradation reactions initiated by SO S 4 may thus be employed as a potential alternative for OH-induced degradation of triazines.

Transformation of 6:2 Fluorotelomer Sulfonate by Cobalt(II)-Activated Peroxymonosulfate

“…•− and • OH very fast and at similar rates (3−8.8 × 10 9 M −1 •s −1 ) 48,49 and the presence of HPO 4 2− or the conversion of SO 4…”

Tertiary Alcohols as Radical Precursors for the Introduction of Tertiary Substituents into Heteroarenes

“…Owing to the low activation barrier for homolysis of (NH4)2S2O8, the heat generated from the blue LEDs employed in our reaction setup (~60 °C) was sufficient to cleave the O−O bond, 17 generating two highly oxidizing sulfate radical anions (SO4 •-). 18 The resulting SO4 •radicals are then capable of oxidizing 2 to generate tert-butyl radicals. Interestingly, Minisci and coworkers did not observe reactivity in the absence of AgNO3 in their previous studies with oxalic acid monoesters, likely a result of the higher potential required for oxidation these precursors.…”

Simulation and comparative study on the oxidation kinetics of atrazine by UV/H2O2, UV/HSO5− and Luo1, Ma2, Jiang3 et al. 2015Water Research3261290View full textAdd to dashboardCite

“…where f ATZ is the quantum efficiency of ATZ (0.046 mol E À1 (Hessler et al, 1993)), I 0 is the volume-based irradiance (1.291 Â 10 À7 E L À1 s À1 ), f ATZ is the fraction of UV irradiation absorbed by ATZ, b is the optical path length (4.0 cm), ε ATZ is the molar extinction coefficient of ATZ (3860 M À1 cm À1 at 254 nm (Nick et al, 1992;Manoj et al, 2007)), ε oxi: is the molar extinction coefficient of the oxidant at 254 nm (as shown in eqs (1)e(3)), and ε NOM is the molar extinction coefficient of the natural organic matter (0.11 L mgC À1 cm À1 ).…”