Misconceptions about the chemistry of aqueous chlorine atoms and HClOH˙(aq), and a revised mechanism for the photochemical peroxydisulfate/chloride reaction

Abstract

It is widely considered that aqueous chlorine atoms (Cl•) convert to the species HClOH• with a half life of about 3 µs and that this species plays an important role...

Far-UVC Photolysis of Peroxydisulfate for Micropollutant Degradation in Water

“…SO 4 •– oxidizes Cl – and gets converted via one-electron transfer (eq , k = 3.00 × 10 8 M –1 s –1 ) to Cl • , at a concentration of 7.05 × 10 –14 M under the experimental conditions (Table ). Cl • reacts with H 2 O (eq , k = 2.50 × 10 5 M –1 s –1 ) to form ClOH •– , ,, which subsequently decomposes and generates HO • (eq , k = 6.10 × 10 9 M –1 s –1 ). ,, The result suggests that Cl – at 20 mg L –1 promotes the degradation of micropollutants that preferably reacts with HO • or Cl • in the UV 222 /PDS AOP, while the degradation of micropollutants that preferably react with SO 4 •– (e.g., perfluorooctanoic acid) will be inhibited. Bromide (Br – ) was also detected in surface water in some countries (e.g., Israel and Australia), and the effect of Br – in the UV 222 /PDS AOP was investigated and discussed in Text S10. SO 4 • − + Cl − → SO 4 2 − + Cl • Cl • + H 2 O → ClOH • − + H + ClOH • − → HO • + Cl − …”

“…Cl • reacts with H 2 O (eq 7, k = 2.50 × 10 5 M −1 s −1 ) to form ClOH •− , 8,49,50 which subsequently decomposes and generates HO • (eq 8, k = 6.10 × 10 9 M −1 s −1 ). 8,49,50 The result suggests that Cl − at 20 mg L −1 promotes the degradation of micropollutants that preferably reacts with HO micropollutants that preferably react with SO 4…”

Prediction of Aqueous Reduction Potentials of X•, ChH•, and XO• Radicals with X = Halogen and Ch = Chalcogen

“…11 On a more fundamental side, there are important questions about the nature of the properties of simple atomic radicals in aqueous solution. For example, Stanbury 12 has examined the properties of Cl • in aqueous solutions to provide insights into the nature of the interactions of the Cl • with H 2 O and how best to interpret the results of a broad range of experiments using the principle of detailed balancing. He has shown that it is not appropriate to describe Cl • in H 2 O as a species distinct from HClOH • .…”