Molecular Characterization Of Dissolved Organic Matter In Industrial Wastewater Based On Solid Phase Extraction Coupled With High-Resolution Mass Spectrometry

The composition of industrial wastewaters is extremely complex.The dissolve organic matter(DOM)in wastewaters and its conversion rules in water treatment process are not clear,because of the lack of effective means to analyze the refractory DOM in wastewaters.High resolution mass spectrometry(HRMS)combined with electrospray ionization(ESI)ionization source can obtain accurate DOM molecular composition informations from the microscopic level,However,due to the ionization selectivity of the instrument for different types of compounds,the pretreatment of wastewaters DOM is necessary.In this thesis,two novel solid phase extraction(SPE)methods were applied to the DOM separation of natural water and industrial wastewaters.The separation effect was analyzed by total organic carbon(TOC)and negative-ion ESI HRMS,and the conversion rules in industrial wastewater DOM was studied during the advanced persulfate oxidation.The DOM were divided into phenols(pH = 7),fatty acids(pH = 5),aromatic carboxylic acids(pH = 3)and ketoic acids(pH = 2)according to different acidity by reverse cartridge(PPL).Fatty acids(14.7%)and aromatic carboxylic acids(11.5%)are the main body in natural hydrophobic acid of DOM.As the pH of natural water sample decreased gradually,negative-ion ESI HRMS detects that compounds in the eluent gradually moved to the high oxygen number end.Phenol(19.0%)is the main body in hydrophobic acid of biochemical effluent DOM from coal coking.But the content of organic sulfonates in the wastewater is high,and PPL cartridge will preferentially adsorb sulfonates at any pH.The higher concentration of sulfonates in the eluent would seriously affect the ionization effect on acid oxygen-containing substances during ESI HRMS analysis,which results the composition informations of oxygen-containing acid compounds in wastewaters DOM analysis are lost.A novel SPE method based on anion exchange column(PAX)was developed.The oil refining wastewater and coal coking wastewate DOM were separated into hydrophobic neutral fraction(HON),hydrophobic acidic fraction(HOA)and hydrophobic strong acidic fraction(HOSA)by adjusting the acidity of elution solvent.HON and HOA are the main parts of wastewaters DOM.Heteroatomic classes containing nitrogen-oxygen compounds and the oxygenated compounds with low oxygen number are mainly detected in HON,while oxygen-containing compounds with high oxygen number are mainly detected in HOA.The classes of compounds in HOSA are remarkably similar to PPL,and the relative abundances of oxysulfur compounds are absolutely dominant.The organic sulfonates in the wastewaters are separated into HOSA and accounted for only 11% and 2% of the TOC in the refinery wastewater and the coal coking wastewater respectively.The volatile organic compounds(VOCs)in the biochemical effluents of coal coking wastewaters account for only about 10% or less.After persulfate oxidation,the VOCs in the wastewaters are completely removed,and the relative abundances of compounds containing more oxygen atoms are increased.The relative abundances of oxysulfur compounds decreased greatly,and the organic sulfonates in wastewaters are basically removed after oxidation.Neutral nitrides with high carbon atomic number and high condensation degree are preferentially reacted.Oxygen-containing compounds are dominant in the wastewater after oxidation,mainly medium and long chain fatty acids.The DOM of industrial wastewaters are separated and enriched according to its acidity by a novel SPE method,which eliminates the strong ionization suppression between different types of compounds during ESI HRMS analysis.It could obtain the main part in wastewater DOM,and deepen the understanding of the conversion rules of wastewater DOM in water treatment process.