Iodinated Products Formation In Peroxomonosulfate Oxidation System

Iodinated products have gained increasingly attentions recent years for their much more genotoxic and cytotoxic than their chlorinated and brominated analogues effects on human beings and natural lives, according to previous studies. I-, as one of the halide ions ubiquitously existed in natural environment, contributes a lot to the formation of iodinated products during regular water treatment oxidation processes.Peroxymonosulfate(PMS), as one of the oxidant of peroxygen family, has received great attentions in industrial synthesis processes, as well as the remediation of groundwater,surface water and wastewater for its relatively higher oxidation potential. PMS is able to oxidize iodide to reactive iodine species(RIS), which is likely to react with co-existed organic pollutants to form Iodinated products when applied in water treatment. This work investigated factors influencing the formation of iodinated products in PMS oxidation process, including model precursors, p H and concentrations of iodide.The rate constants between PMS and RIS were measured for the first time in this paper. The apparent second order rate constant of PMS with RIS at p H=5 was 108.29 M-1s-1, which sharply increased to 45412.495 M-1s-1 at p H=9. Rate constants between different species of PMS and HOI were well fitted by acid-base proton kinetics model. Oxidation process model was established, and the model can effectively fit iodate generation scenarioes in the process of PMS oxidizing iodide.When simple organic matter phenol and iodide were both presented in PMS conditions, competing reactions of RIS exist,i.e. comsumption of RIS by PMS or by phenol. The results showed that the oxidation ability of PMS is very strong when oxidized RIS, under the condition of PMS excess of phenol ten times, at least 40% conversion of iodine to iodate, the rest of iodine to form odinated products. LC-MS/MS results indicated that four iodinated products were formed and the corresponding structures and formation pathway were tentatively presented. Fitted reactions primary products(2-iodophenol, 4-iodophenol) generation scenarioes in model established.Various kinds of model compounds were selected as model precursors to investigate the adsorbable organic iodine(AOI) formation during PMS oxidation process, such as phenolic compounds, amino acids, olefinic compounds, carboxylic acids and three natural organic matter isolates. The results indicated that among those precursors, phenolic compounds formed the highest amounts of AOI and the formation yields were related with the substituents in the benzene ring; then followed by the olefinic compounds, whose yield increased obviously in lower p H; other model compounds formed less AOI, and their formation amounts is greatly influenced by p H. As p H increases, the AOI decreased significantly, while the sum of AOI and inorganic iodine remained constant. As for total organic carbon levels of those model compounds, no apparent changes were observed before and after PMS oxidation. Besides, iodoform was also not detected. Observed the formation of AOI under different p H conditions, and obtained the result that PMS oxidation process has lower risk to form iodinated products in alkaline water.This work proposed the competitive relation between the oxidants and organic matter when RIS transformat in PMS oxidation process, and provided the fundamental data for assessment of iodinated products formation risk in PMS application.