Thiosulfate

A water sample was collected post rapid gravity filtration from a water treatment works (WTW) in Scotland, UK. In brief, the process stream was (A) raw water inlet, (B) coagulation, (C) dissolved air flotation, (D) rapid gravity filtration, (E) chlorination, (F) storage and distribution. Disinfection experiments were performed by adding aliquots of chlorine solution to 100 mL of water in AOC-free conical flasks. Final chlorine concentrations were 0.01, 0.025, 0.05, 0.10, 0.25, 0.50, 0.75 and 1.00 mg L -1 . Samples without chlorine served as controls. The flasks were shaken for 30 minutes to allow for sufficient mixing and chlorine was subsequently quenched by addition of 1 mL of 0.1 N of thiosulfate (Acros Organics, Geel, Belgium).

AR18 (C20H11N2Na3O10S3, 80%) was obtained as powder from a Tunisian food factory and was used without further purification. Magnetite (Fe3O4, 97%), hematite (Fe2O3, 98%) nano-powders and sodium sulfate (Na2SO4, 99%) were used as catalyst and supporting electrolyte respectively and were purchased from Sigma Aldrich. DMSO (C2H6OS, 99,7%) and sodium methanesulfonate (CH3NaO3S,99%) were purchased form Sigma Aldrich as well. Thiosulfate (Na2S2O3, 98,5%) and analytical grade of sulfuric acid were used as a titrant for hydrogen peroxide quantification and pH adjustment respectively, both were purchased from Acros Organics. 1,10 phenantroline, used for the colorimetric determination of Fe ions was purchased from Alfa Aesar. All solutions were prepared with ultrapure water and all the other chemicals used for analysis were purchased from Acros and Sigma Aldrich.