Optimization of the Fenton treatment of 1,4-dioxane and on-line FTIR monitoring of the reaction

Removal of 1,4-dioxane from industrial wastewaters: Routes of decomposition under different operational conditions to determine the ozone oxidation capacity

“…No EGDF could be detected along the reaction, but EG was identified as the primary reaction intermediate by both ConcIRT software and chromatography, simultaneously with the increment of oxalic acid as its final decomposition product [32,35]. EG is most likely produced by the hydrolysis of its formate esters [31,32,35], implicating the same initial mechanism of the EGCF formation as in the case of pH<5.7. However, like proposed in a previous study on Fenton oxidation [35], EGDF is not detected, as it is quickly hydrolyzed to EG.…”

“…In the experiments with FTIR monitoring, synthetic solution with a substantially higher initial 1,4-dioxane concentration of 6168 mgL -1 was used, according to Merayo et al [35]. Instead of using NaOH, the basic conditions with the pH above 9 were maintained by a one-time addition of 23.8 mM of NaHCO3 as a buffer to ensure a constant background for the FTIR measurements.…”

“…Detailed description of the equipment and the data adquisition is published elsewhere [35]. Real-time component analyses were run using ConcIRT software (Mettler-Toledo, Columbia, USA), which calculates the associated component spectra, and relative concentration profiles.…”

“…EGDF is generated by an oxidative ring opening mechanism through peroxyl radical [32,35]. In addition, a parallel route occurs through the formation of methoxyacetic acid [32], but in a lesser extent, since the chromatography analysis detected metoxyacetic acid only in the first quarter of the experiment.…”

“…Recently, Merayo et al [35] demonstrated the advantages of on-line FTIR spectroscopy to monitor the evolution of reaction intermediates during the Fenton oxidation of aqueous 1,4-dioxane, showing that a good calibration could provide valuable information in situ, avoiding expensive and time-consuming sample preparation and analyses. For ozonation process, this online method presents an appealing opportunity to track the different reaction pathways under varying process conditions, as different degradation by-products of 1,4-dioxane could be expected to dominate depending on the reaction pH [31].…”