Advanced Oxidation Processes (AOPs) are designed to remove aqueous organic contaminants through their reaction with hydroxyl radicals. Due to the unselective nature of hydroxyl radicals, many organic and inorganic co-solutes react can act as scavengers, reducing the efficiency of an AOP. Here we show a probe system for testing the hypothesis that adsorptive ozonation of contaminants may yield a more selective environment that favors neutral contaminant oxidation over oxidation of co-solutes. The hydroxyl radical probe 3-nitro-α,α,α-trifluorotoluene (TFT) was examined at pH 7.8 during ozone exposure. A low thermal mass gas chromatograph with electron capture detection monitored TFT extracted from aqueous solution using MTBE. Colorimetric analysis of O3 was performed using the indigo trisulfonate assay. The rate of TFT removal was determined in the absence and presence of an added zeolite suspension, such as CBV 720 (SiO2:Al2O3 = 30, unit cell 24.3 Å and surface area = 780 m2/gram) or Magnetite. Baseline results were obtained by varying amount of zeolite in the presence of TFT. Addition of bicarbonate ion decreased TFT oxidation rates in solution, consistent with the effect of a negatively charged surface repelling carbonate from the local environment of the reaction. Theoretical hydroxyl radical steady state concentrations on the order of 1x10-16 M are modeled with time from the decrease in ozone concentration, and compared to observed losses.

Can heterogenous suspensions provide micro-environments protected from radical scavengers during ozonation?

254th National Meeting (2017)

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