Molecular transformation of dissolved organic matter in high-temperature hydrogen peroxide oxidation of a refinery wastewater

Advanced oxidation processes have been extensively used in industrial wastewater treatment. However, themolecular transformation of dissolved organic matter (DOM) duringoxidation process is poorly known. In this study, a refinery wastewater was oxidized at high temperature using H2O2. Negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was applied to analyze the molecular changes of DOM. 68 heteroatom class species including O-x, OxS1, OxS2, N1Ox, N2Ox, N3Ox, and N1OxS1 were assigned from a single spectrum of the raw water, in which O-x and OxS1 class species were dominant. The molecular composition changed duringoxidation. Sulfur- and nitrogen-containing compounds were almost completely removed. The removal of oxygen compounds by oxidation and the new production of oxygen compounds were simultaneous. Chain scission and oxidation of O-x compounds were the major reactions. Abundant chlorinated compounds were detected in the oxidation product. These compounds areconsidered as reaction products of DOM molecules with chloride ions in the water.