Dissolved organic matter (DOM) in petroleum refinery wastewater was an extremely complex mixture with countless individual compounds. Molecular compositional characterization of DOM is necessary for a comprehensive understanding of its transformation in treatment processes. In recent years, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been widely applied to the characterization of DOM from different aquatic environments. However, most of the studies used negative ion electrospray ionization (ESI) as the ionization source, which selectively ionize acidic compounds in the complex matrix.<br/>In this paper, DOM was enriched by solid phase extraction and characterized by use of positive-/negative-ion ESI and positive-ion atmospheric pressure photoionization (APPI) FT-ICR MS.<br/>The molecular weight distributions of DOM varied from 150 to 500 m/z. In negative-ion ESI analysis, the acdic oxygenated compounds were predominant. The O2-4 class species were the most abundant and likely naphthenic acids. The relative abundance of NxOy and OxSy class species was lower than that of Ox class species, containing N1, N1O1-5, N2, N2O1-4, and O1-7S1 heteratom classes. In positive-ion ESI analysis, detected class species include N1O0-5, N1O1-4S1, N1S1-2, N2O1-3, N2O1S1, N2S1, O1-4, and O2-5S1. The N1O0-2 class species were the most abundance and likely basic nitrogen compounds. The O1-4, and O2-5S1 were likely ketons and sulfoxides, respectively, which can be ionized under the positive-ion ESI.<br/>The mass spectrum of APPI analysis was more complex than that from ESI analysis. In positive-ion APPI analysis, detected class species include CH, N1O0-3, N1O1S1, N1S1, N2O0-3, O1-4, O1-2S1, and S1. The HC class species were predominant. The results shows that the refinery wastewater contains a considerable amount of hydrocarbons, which was neglected in ESI analysis. Except the CH class species, the relative abundance of N1O0-3 and O1-4 class species were quite higher than other class species, which was consistent with the positive- and negative-ion ESI analysis.<br/>The results of mass spectrometry and elemental analysis show that the refinery wastewater DOM have the higher sulfur and nitrogen content and the lower oxygen content than that of natural organic matter. The compounds in DOM have a lower degree of condensation.

Molecular characterization of Dissolved Organic Matter (DOM) in petroleum refinery wastewater by FT-ICR MS with ±ESI and +APPI ionization

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.