Molecular Characterization of Dissolved Organic Matter and Its

Subscriber access provided by OAKLAND UNIV

Article

Molecular Characterization of Dissolved Organic Matter and Its Sub-fractions in Refinery Process Water by FT-ICR MS Yongyong Li, Chunming Xu, Keng H. Chung, and Quan Shi Energy Fuels, Just Accepted Manuscript • Publication Date (Web): 20 Apr 2015 Downloaded from http://pubs.acs.org on May 3, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Molecular Characterization of Dissolved Organic Matter and Its Sub-fractions in Refinery Process Water by FT-ICR MS Yongyong Lia, Chunming Xua, Keng H Chunga,b, and Quan Shia*

a

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China b Liaoning Huajin Tongda Chemicals Co. Ltd., Panjin, Liaoning 124021, China

ABSTRACT Dissolved organic matter (DOM) in oil refinery process water was fractionated by XAD-8 resin techniques into four sub-fractions: hydrophobic acids (HOA), hydrophobic bases (HOB), hydrophobic neutrals (HON), and hydrophilic substances (HIS) fractions. Negative and positive electrospray ion (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the composition of DOM and its sub-fractions. Compounds with multi-oxygen atoms were found to be predominant in DOM by either negative or positive ESI analysis, which are similar in composition to most other treated water samples. The DOM in HOA fraction had a similar molecular composition to that of raw process water by negative ESI analysis. The DOM in HOB fraction had low molecular weight when analyzed by positive ESI, and basic nitrogen compounds such as N1 class species were found to be predominant. The DOM in HON fraction were predominantly O2 class species. The DOM in HIS fraction had a relatively wide molecular weight (MW) distribution. All the compounds of DOM in HIS fraction 1

ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

exhibited low double bond equivalents (DBE) and low carbon numbers. The results showed that the use of the XAD-8 resin fractionation technique is valuable for characterizing trace quantities DOM components in process water as their spectral peaks would otherwise be obscured by other abundant peaks. The origin and the determination of chlorine-containing compounds which are abundant in the negative ESI mass spectra of HOB were discussed.

Keywords: Process Water; DOM; Chemical characterization; XAD-8 resin fractionation; ESI; FT-ICR MS

2


Page 2 of 28

Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1. Introduction To enhance environmental protection and sustainable resource development in the past two decades, increasing stringent environmental regulations have been imposed on industrial emissions and water discharges.[1] Oil refining operations use a large amount of water and, as a result, generate a significant volume of treated waste water.[2] With economic expansion, it is expected that increased amount of industrial waste water will be generated from chemical, petroleum and mining industries.[2-4] Dissolved organic matter (DOM) is a major organic component of process water and is refractory to biodegradation. DOM in process water are primarily comprised of natural organic matter (NOM) from surface water, refractory compounds, residual degradable substrates and soluble microbial products.[1] Although tremendous efforts have been devoted to water treatment, some organic matter are resistant to remove[5]. Also, the molecular composition of many organic species is not well defined, making it aimless to optimize water treatment processes. Hence, a comprehensive analytical method is needed to better understand the refractory DOM in process and waste water. Isolation and fractionation of DOM can enhance the analysis, such as adjustments to increased ionic strength and concentration levels. A resin adsorption chromatographic technique can separate and concentrate the complex water organic compounds into more specific, physico-chemically analogous sub-groups. This can facilitate the subsequent research on DOM, such as the formation of disinfection by-products during treatment.[6] Since the development of resin adsorption chromatographic techniques to isolate DOM 3


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

into sub-fractions for natural water and waste water treatment systems in 1970s,[7, 8] the Amberlite XAD resin method has been widely used in many applications.[9-13] Using resin adsorption fractionation, the characteristics of the isolated DOM fraction can be determined by various analytical techniques such as elemental analysis (EA),[14] ultraviolet-visible spectroscopy (UV/Vis),[13, 15, 16] Fourier transform infrared spectroscopy (FT-IR),[11, 13, 15] nuclear magnetic resonance spectroscopy (NMR),[11, 17] and fluorescence excitation/emission matrix spectroscopy (EEM).[12, 13] However, while these analytical methods are useful in understanding the nature of DOM and its fractions in various aquatic environments, they are inadequate to provide information on the molecular composition. Recently, electrospray ionization (ESI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was successfully applied to characterize DOM in various water samples.[18-27] Due to ultrahigh resolution (>200 000) and mass accuracy (error < 1 ppm), ESI FT-ICR MS can unambiguously assign an elemental composition to each DOM molecule.[20] In addition, soft ionization of macromolecules is feasible, which makes ESI suitable for analyzing the polar components of DOM and its fractions. Nevertheless, it is expected that a certain amount of analyte may not be or poorly ionized by ESI for ion suppression. In this study, a treated refinery process water was fractionated using XAD-8 resin. DOMs in raw water and its fractions were characterized by negative and positive-ion ESI FT-ICR MS analysis. The objective of this work was to better understand the molecular 4


Page 4 of 28

Page 5 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

composition of DOM in refinery process water.

2. Materials and methods 2.1 Materials Refinery process water samples were obtained from a water treatment plant in a PetroChina refinery. The technique is commonly used for refinery wastewater treatment, which including deoiling, floatation, biochemical degradation, bio-aeration, and sedimentation. The water discussed in this study was the final effluent after sedimentation. Another water sample labeled “Water II” was the feed to the biochemical degradation. The water samples were filtered through a 0.45 Pall Supor filter membrane and stored in the dark at 4°C. 2.2 Fractionation and preparation of DOM fractions The fractionation of DOM in process water was performed according to the method described by Wang[12] and as shown in Figure S1 (See Supporting Information) to yield four sub-fractions: hydrophobic acids (HOA), hydrophobic bases (HOB), hydrophobic neutrals (HON) and hydrophilic substances (HIS) fractions. The Amberlite XAD-8 resin (20-60 mesh) was packed in a glass chromatography column. Resin activation was carried out following the procedure developed by Leenheer.[7] Two liters of filtered water sample was pumped through the XAD-8 resin packed column. The eluted water (sample #1) was collected for further separation. The hydrophobic bases (HOB) fraction was obtained by back-flushing the resin column with 5


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

50 mL of 0.1 M hydrochloric acid (HCl). The eluted water collected (sample #1) was acidified to pH=2 and re-circulated through the resin column to obtain the hydrophilic substances (HIS) fraction. The hydrophobic acids (HOA) fraction was obtained by back-flushing the resin column with 50 mL of 0.1 M sodium hydroxide. The resin was subsequently air-dried for 12 h and subjected to Soxhlet extraction with LC-MS grade methanol to obtain the hydrophobic neutrals (HON) fraction. The excess methanol was removed by vacuum rotary evaporation at 45°C. 2.3 Organic carbon analysis A total organic carbon (TOC) analyzer (TOC-5000A, Shimadzu, Japan) was used to determine the dissolved organic carbon (DOC) in the raw process water and its sub-fractions. Prior to DOC analysis, the pH of each fraction was adjusted to 7.0 ± 0.2 and LC-MS grade water was added to dilute each fraction to 2 L. 2.4 Mass Spectrometry Prior to ESI FT-ICR MS analysis, the sample was acidified with HCl to pH=2 and pumped through a Sep-pak C18 (1 g) solid-phase extraction cartridge (6 mL, Waters, USA) at 5 mL/min. Prior to this, the cartridge was rinsed with methanol followed by acidified (pH=2) water. Before elution, the cartridges were rinsed with 20 mL acidified water to remove the salt. The salt-free sample was eluted with 20 mL methanol. The eluted samples were stored at -18°C in the dark. The mass spectrometry analyses were performed using a Bruker Apex Ultra FT-ICR mass spectrometer equipped with a 9.4 T superconducting magnet and Apollo II 6


Page 6 of 28

Page 7 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

electrospray ion source. The test sample was dissolved in methanol at a concentration of 0.2 mg/mL and directly injected into the electrospray source at 180 µL/h using a syringe pump. The operating conditions for negative-ion formation consisted of 4.0 kV emitter voltage, 4.5 kV capillary column introduced voltage, and -320 V capillary column end voltage. The operating conditions for positive-ion formation consisted of -3.0 kV emitter voltage, -3.5 kV capillary entrance voltage, and 320 V capillary column end voltage. The mass range was set to m/z 150−1000. The 4 M word size was selected for the time domain signal acquisition. A number of 128 scan FT-ICR data sets were accumulated to enhance the signal-to-noise ratio and dynamic range. Methodologies for FT-ICR MS mass calibration, data acquisition, and processing have been described elsewhere.[28, 29] Baseline scans for methanol and blank C18 extraction elute were performed to ensure the instrument was clean prior to analyzing the samples. While it was determined that only a few mass spectral peaks of blank C18 extraction elute overlapped with those of test sample, all the spectral peaks of blank C18 extraction elute were removed from the test sample peak list. It should be noted that, in this study, C18 solid phase extraction was used to desalt and concentrate the DOM from the raw water and its fractions. Therefore, for all samples, the results are for C18 extractable DOM molecules instead of the whole fractions.

3. Results and discussion 3.1 DOC distribution in DOM-fractions 7


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Based on the DOC analysis, the yields of HIS, HOA, HOB, and HON were 57%, 34%, 6%, and 3%, respectively. It should be noted that the separation by resin fractionation is not discrete and is dependent on experimental conditions such as the amount of eluting solvent. As a result, the chemical composition of each sub-fraction will not be discrete. For example, the HIS fraction may not be a distinct organic water fraction as it was a residual water that had hydrophobic materials removed. Also, the distribution of DOM in sub-fractions is likely to vary depending on the operating parameters of water treatment process.[11] Hence, the results on DOM composition obtained from this study may not be representative for all refinery process water. 3.2 Molecular Characterization of DOM by negative-ion ESI FT-ICR MS. Figure 1 shows the broad-band negative-ion ESI FT-ICR mass spectra for the C18 extracts of DOM in the raw water and its sub-fractions. In negative-ion ESI analysis, acid compounds and neutral nitrogen compounds can be selectively ionized.[30] The molecular weight (MW) distributions of DOM in the raw water and its sub-fractions varied from 150 to 550 Da. The HOA fraction exhibited a relative wide MW range, and had a similar mass spectral range as the raw water. This is expected, since negative ESI can selectively ionize the acidic compounds. Compared to raw water, the spectral peaks at high MW exhibited higher relative abundances in the HOA fraction. It is likely that these large molecules were relatively more hydrophobic and enriched in the HOA fraction. The spectra of DOM sub-fractions were different from each other, indicating varied molecular composition among the sub-fractions. Abundant peaks of the DOM in 8


Page 8 of 28

Page 9 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

raw water and HOA fraction were predominantly odd mass ions with a mass spacing pattern of 14.0156 Da for CH2-groups and an increment of 36.4 mDa for substitution of O by CH4. This indicates that DOM in process water was comprised of molecules with chemically related families, or homologous series, which is consistent with the results of previous studies.[31-33] Figures 2 and 3 show the scale-expanded views of negative-ion ESI FT-ICR mass spectra (resolving power >400 000) for the DOM in raw process water and its sub-fractions at an odd mass of m/z 285 and an even mass of m/z 286, respectively. The elemental composition of these DOM compounds can be accurately identified by the distinct MW and corresponding homologue series. Figure 2 shows the molecules containing C, H, and O, and those that contained sulfur in the DOM of the raw process water. These compounds consisted of O2-O7 and S1O3-S1O6 class species. The chemical compositions of C, H and O-containing molecules were similar to those found in NOM samples.[18, 31-34] The HOA fraction had a similar mass spectrum pattern compared to the raw process water. However, the C, H, and O-containing molecules in DOM of the HOA fraction had less O2-O3 containing molecules and had abundant molecules containing more than 3 oxygen atoms. It has been reported that the mass peaks of chlorinated products of NOM from drinking water chlorination processes have relatively low intensities which were suppressed by those of other class species. This is consistent with the findings of this study since the chlorine-containing molecules in the raw process water presented 9


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

relatively low mass peak intensities.[26] By contrast, the DOM of HOB fraction had a high abundance of chlorine-containing molecules and the intensities and relative abundances of chlorine-containing molecules were amplified in this fraction. To verify these results, a similar process of fractionation and characterization, as described above were performed on the “Water II” sample (feed water to the biochemical water treatment process). Figure 4 shows the scale-expanded view of negative-ion ESI FT-ICR mass spectra for the Water II and its HOB II fraction at an odd mass of m/z 313. The chlorine-containing molecules of the Water II sample had much higher peak intensities than those of raw process water as shown in Figure 3. Also shown in Figure 5, in the HOB II fraction, the intensities of C, H, and O-containing molecules and those contained sulfur were significantly reduced in the presence of chlorine-containing molecules, especially for molecules contained more oxygen atoms. This suggests that the detection of chlorine-containing molecules in HOB fraction was enhanced, regardless of the chlorine content. The chlorinated species also could be formed in the fractionation process, because the HOB fraction was obtained by hydrochloric acid flushing from the resin column, and most samples were acidified to PH=2 for resin fractionation and C18 extraction. Since the ESI results are non-quantitative, it is unable to conclude that the chlorine-containing molecules were enriched in HOB fraction by XAD-8 resin fractionation so far. However, these findings are potential for developing quantitative characterization methods for chlorine-containing species in water samples. The HON fraction exhibited an abundant O2 peak at m/z 285. Since these O2 class 10


Page 10 of 28

Page 11 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

species were detected by negative ESI, they are likely carboxylic acids. These large molecular acids with one carboxyl are hydrophobic and have strong affinity to the XAD-8 resin.

C, H, and O-containing molecules with more than 5 oxygen atoms and

atoms containing chlorine were identified in the HIS fraction. These were the most hydrophilic components of DOM and had the strongest affinity to XAD-8 resin. The mass peaks of nitrogen containing molecules were abundant in DOM of the raw water as shown in Figure 3. Nitrogen compounds with similar composition have also been found in NOM samples.[18, 31-34] The N1O2-N1O6 class species were identified in the raw water, HOA, and HIS fractions at m/z 286. The N1O2-N1O3 class species were less abundant in the HOA fraction than those in the raw process water. Figure 5 shows the double bond equivalents (DBE) distribution in various molecules as a function of the class species in DOM of the raw water and its sub-fractions. The C, H, and O-containing molecules were predominantly O1-O13 class species with 1-18 DBE and carbon numbers of 5-40. The raw process water, HOA, and HOB fractions had the highest relative abundance of O4 class species. The highest relative abundance of C, H, and O-containing molecules in the HON and HIS fractions were O2 and O6 class species, respectively. N1O2~11 and S1O2~9 class species were identified in the raw water and all of its sub-fractions. Figure 6 shows the iso-abundance plots of DBE versus carbon number of O2, N1O4 and S1O4 class species to allow comparison of molecular composition of DOM in the raw water and its sub-fractions. The size of the circle in each iso-abundance plot is correlated 11


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

to the relative abundance of each type of molecule. Figure 6 shows that the dominant species in each iso-abundance plot spread over relative low DBE and carbon number ranges. The carbon number was less than 30, indicating that the acidic DOM compounds consisted of small molecules. Although heavy petroleum fractions have large molecules with MWs more than 1000,[35] these large molecules were not detected in the process water samples. The DBE values of species in process water samples were higher than those detected in most petroleum fraction,[28] indicating that the aromatic structure units of DOM in the process water were higher than those of molecules in petroleum fractions. Even though the molecular structures cannot to be assigned based on DBE and carbon number, nevertheless some structural information could be speculated from the pattern of iso-abundance plot. For example, the most abundant compounds of O2 class species in DOM of the raw water have 7 DBE; these could be diols of naphthalene or naphthalenol with a methoxy group.[28] 3.3 Molecular Characterization of DOM by Positive-ion ESI FT-ICR MS Since the DOM were rich in acids, negative ESI is an appropriate ionization technique for MS analysis Positive ESI has rarely been used for characterizing DOM. [18-21] However, theoretically, basic species can be ionized by positive ESI.[30] Figure S2 (see Supporting Information) shows the broad-band positive ESI FT-ICR mass spectra of the C18 extracts in DOM of the raw water and its sub-fractions. The MW range of DOM in the raw water and its sub-fractions varied from 150 to 750 Da, which was a slightly wider range than that detected by negative ESI. The HOB fraction, by definition 12


Page 12 of 28

Page 13 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

a basic fraction, had a strong mass peak intensity (not shown). It enriched small molecular basic species in the process water. These peaks may represent the strong basic nitrogen compounds in the HOB fraction. Unlike the predominant even mass ions exhibited by negative ESI, mass peak intensities were irregular for DOM in the raw water and its sub-fractions, indicating a complex structural composition of basic species. Figures 7 shows the close-up view of expanded positive ESI FT-ICR mass spectra for DOM in the raw water and its sub-fractions at an even mass of m/z 256 (similar odd mass of m/z 257 are shown in Figure S3 (see Supporting Information). A total of seven class species were assigned for the DOM of the raw water and its sub-fractions. The relative abundance of each class species is shown in Figure S4 (see Supporting Information). All of the assigned nitrogen containing species can be described with a general formula N1Ox (where x=0-6). These compounds had 1-18 DBEs and carbon numbers of 5-40. The raw water and HIS fraction had the highest relative abundance of N1O2 class species. The highest relative abundant species in HOA, HOB, and HON were N1O4, N1, and N1O1, respectively. As shown in Figure 7, while the HOA fraction contained N1O2 and N1O3 class species, no N1 and N1O1 class species were found. This suggests that all of the compounds detected in the DOM of the HOA fraction were basic nitrogen compounds with acidic function groups. These nitrogen containing compounds were enriched in the “acidic fraction”. The HOB fraction had a high abundance of N1 class species, containing the most basic nitrogen compounds in DOM. Although oxygen-containing nitrogen compounds such as N1O1 and N1O2 were found in the HOB fraction, the mass spectrum 13


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

intensities of these compounds were low. In the HON fraction, Na+ adducts of N1Ox (x=1-4) were dominant. Since C18 solid phase extraction was used to desalt the process water, theoretically the Na+ adducts detected by positive ESI cannot be completely eliminated. The Na+ adducts could also derived from the ionization. The Na+ adducts of O1-O6 species were detected in the HON fraction (also shown in Figure S4 in the Supporting Information). The iso-abundance plots of DBE versus carbon number for selected N1 and N1O2 class species in DOM was shown in Figure S5 (see Supporting Information). The most abundant N1 species in the raw water had DBE values of 3-8. The N1 class species were separated into various sub-fractions using the XAD-8 resin fractionation. The compounds exhibited high DBE values in the HOB fraction, but had low DBE values in the HON and HIS fractions. The HIS fractions contained N1 class species with lower carbon numbers than those in the HON fraction. No N1 class species were found in the HOA fraction, indicating that the HOA fraction was free of basic nitrogen compounds. Basic nitrogen compounds are often found in petroleum fractions, which can be easily analyzed by positive ESI.[36] Since the process water samples were obtained from a refinery, it is conceivably that the basic nitrogen compounds in the process water were related to contamination by petroleum compounds. However, the DBE distribution patterns of DOM shown in Figure S5 were different from those of petroleum fractions; the lowest DBE value of most abundant species in N1 class was 3 instead of 4. The latter corresponds to pyridines which are common nitrogen compounds in petroleum 14


Page 14 of 28

Page 15 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

fractions.[36] Even though there is no prior discussion on the nitrogen compounds with 3 DBE, these nitrogen compounds are likely pyrrole derivatives. Pyrrole is a non-basic nitrogen compound, nevertheless its homologs with multi- or long- side chain substitutes could result in ionization by positive ESI. Since these compounds were weakly basic, they were would be eluted into the HON and HIS fractions rather than the HOB fraction. The molecules with 4 and 7 DBE series are likely pyridine derivatives and quinoline derivatives, respectively. Oxygen-containing nitrogen compounds were detected by positive ESI, in which the N1O2 class species were most abundant. These are basic nitrogen compounds with phenol or carboxyl groups. The patterns of the iso-abundance plot of N1O2 class species were similar to the oxygen-containing nitrogen compounds detected by negative ESI (not shown). The most abundant series of N1 and N1O2 class species had 7 DBE, corresponding to the structure of quinolines with hydroxyl or ether linkages. The N1Ox class species could be the oxidized products from N1 class species, or derived from the humic matters in the water. Compounds with multi-oxygen atoms were found to be predominant in DOM by either negative or positive ESI analysis, which are similar in composition to most other treated water samples. Although similar molecular composition does not means the DOMs have identical chemical structure. The similar composition results imply important information for the wastewater process: if the composition of the treated refinery wastewater is similar to other wastewaters, the further purification could adapt common 15


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

processing techniques instead of a special one. The origin of the compounds from wastewaters is important and should be investigated for better designing and improving treatment processes. For better understanding of the origin, degradation pathway and mechanism of DOM in refinery wastewaters, a stream by stream comparative study of refinery wastewaters is expected in future study.

4. Conclusions The DOM in refinery process water was separated into four sub-fractions using XAD-8 resin; HOA, HOB, HON and HIS fractions. The DOM of the raw water and its subfractions were characterized by both negative and positive ESI FT-ICR MS. The DOM in HIS and HOA fractions accounted for most of DOC in the raw process water. Heteroatoms such as O1-O13, N1O2-N1O11, and S1O2-S1O9 were identified by negative ESI analysis, whereas N1 and N1O1-N1O6 were by positive ESI analysis. In general, oxygen containing compounds are the major organic compounds found in the process water. The resin fractionation technique combined with ESI FT-ICR MS enabled a detail molecular composition characterization of DOM. Further study should focus on developing quantitative analysis of these complex materials and molecular structure identification of DOM.

Acknowledgements We are grateful to Dr. Haifeng Zhang of the Eco-Environmental Sciences, Chinese 16


Page 16 of 28

Page 17 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Academy of Sciences for desalting the water samples. This work was supported by the National Natural Science Foundation of China (NSFC, 21236009, 21376262).

Appendix A. Supplementary data Supplementary data related to this article can be found at: http://pubs.acs.org.

Author Information Corresponding Author * Quan Shi, Telephone: +86 10-8973-3738. E-mail: [email protected]

17


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

REFERENCES

1.

Yang, W., Li, X., Pan, B., Lu, L., and Zhang, W., Effective Removal of Effluent Organic Matter (Efom) from Bio-Treated Coking Wastewater by a Recyclable Aminated Hyper-Cross-Linked Polymer. Water research, 2013.

2.

Coelho, A., Castro, A. V., and Dezotti, M., Treatment of Petroleum Refinery Sourwater by

3.

Diya’uddeen, B. H., Daud, W. M. a. W., and Abdul Aziz, A., Treatment Technologies for

Advanced Oxidation Processes. Journal of hazardous materials, 2006. 137(1): 178-184. Petroleum Refinery Effluents: A Review. Process Safety and Environmental Protection, 2011. 89(2): 95-105. 4.

Doggett, T. and Rascoe, A., Global Energy Demand Seen up 44 Percent by 2030. Reuters News Agency, 2009.

5.

Quaranta, M. L., Mendes, M. D., and Mackay, A. A., Similarities in Effluent Organic Matter Characteristics from Connecticut Wastewater Treatment Plants. Water research, 2012. 46(2): 284-294.

6.

Marhaba, T. F., Pu, Y., and Bengraine, K., Modified Dissolved Organic Matter Fractionation

7.

Leenheer, J. A., Comprehensive Approach to Preparative Isolation and Fractionation of Dissolved

Technique for Natural Water. Journal of hazardous materials, 2003. 101(1): 43-53. Organic Carbon from Natural Waters and Wastewaters. Environmental Science & Technology, 1981. 15(5): 578-587. 8.

Thurman, E. M. and Malcolm, R. L., Preparative Isolation of Aquatic Humic Substances. Environmental Science & Technology, 1981. 15(4): 463-466.

9.

Lara, R. J. and Thomas, D. N., Isolation of Marine Dissolved Organic Matter: Evaluation of Sequential Combinations of Xad Resins 2, 4, and 7. Analytical Chemistry, 1994. 66(14): 2417-2419.

10.

Li, L., Yan, S., Han, C., and Shan, G., Comprehensive Characterization of Oil Refinery Effluent-Derived Humic Substances Using Various Spectroscopic Approaches. Chemosphere, 2005. 60(4): 467-476.

11.

Kim, H.-C. and Yu, M.-J., Characterization of Natural Organic Matter in Conventional Water Treatment Processes for Selection of Treatment Processes Focused on Dbps Control. Water research, 2005. 39(19): 4779-4789.

12.

Wang, L.-S., Hu, H.-Y., and Wang, C., Effect of Ammonia Nitrogen and Dissolved Organic Matter Fractions on the Genotoxicity of Wastewater Effluent During Chlorine Disinfection. Environmental science & technology, 2007. 41(1): 160-165.

13.

Zhang, H., Qu, J., Liu, H., and Zhao, X., Characterization of Isolated Fractions of Dissolved Organic Matter from Sewage Treatment Plant and the Related Disinfection by-Products Formation Potential. Journal of hazardous materials, 2009. 164(2): 1433-1438.

14.

Mcdonald, S., Bishop, A. G., Prenzler, P. D., and Robards, K., Analytical Chemistry of Freshwater Humic Substances. Analytica Chimica Acta, 2004. 527(2): 105-124. 18


Page 18 of 28

Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

15.

Minor, E. and Stephens, B., Dissolved Organic Matter Characteristics within the Lake Superior Watershed. Organic Geochemistry, 2008. 39(11): 1489-1501.

16.

Li, C.-W., Benjamin, M. M., and Korshin, G. V., Use of Uv Spectroscopy to Characterize the Reaction between Nom and Free Chlorine. Environmental Science & Technology, 2000. 34(12): 2570-2575.

17.

Cook, R. L., Coupling Nmr to Nom. Analytical and bioanalytical chemistry, 2004. 378(6): 1484-1503.

18.

Zhang, H., Zhang, Y., Shi, Q., Hu, J., Chu, M., Yu, J., and Yang, M., Study on Transformation of Natural Organic Matter in Source Water During Chlorination and Its Chlorinated Products Using Ultrahigh Resolution Mass Spectrometry. Environmental Science & Technology, 2012. 46(8): 4396-4402.

19.

D’andrilli, J., Chanton, J. P., Glaser, P. H., and Cooper, W. T., Characterization of Dissolved Organic Matter in Northern Peatland Soil Porewaters by Ultra High Resolution Mass Spectrometry. Organic Geochemistry, 2010. 41(8): 791-799.

20.

Reemtsma, T., These, A., Linscheid, M., Leenheer, J., and Spitzy, A., Molecular and Structural Characterization of Dissolved Organic Matter from the Deep Ocean by Fticr-Ms, Including Hydrophilic Nitrogenous Organic Molecules. Environmental Science & Technology, 2008. 42(5): 1430-1437.

21.

Gonsior, M., Zwartjes, M., Cooper, W. J., Song, W., Ishida, K. P., Tseng, L. Y., Jeung, M. K., Rosso, D., Hertkorn, N., and Schmitt-Kopplin, P., Molecular Characterization of Effluent Organic Matter Identified by Ultrahigh Resolution Mass Spectrometry. Water research, 2011. 45(9): 2943-2953.

22.

Bae, E., Yeo, I. J., Jeong, B., Shin, Y., Shin, K.-H., and Kim, S., Study of Double Bond Equivalents and the Numbers of Carbon and Oxygen Atom Distribution of Dissolved Organic Matter with Negative-Mode Ft-Icr Ms. Analytical Chemistry, 2011. 83(11): 4193-4199.

23.

Zhang, F., Harir, M., Moritz, F., Zhang, J., Witting, M., Wu, Y., Schmitt-Kopplin, P., Fekete, A., Gaspar, A., and Hertkorn, N., Molecular and Structural Characterization of Dissolved Organic Matter During and Post Cyanobacterial Bloom in Taihu by Combination of Nmr Spectroscopy and Fticr Mass Spectrometry. Water Research, 2014. 57(0): 280-294.

24.

Fukushima, T., Hara-Yamamura, H., Urai, M., Kasuga, I., Kurisu, F., Miyoshi, T., Kimura, K., Watanabe, Y., and Okabe, S., Toxicity Assessment of Chlorinated Wastewater Effluents by Using Transcriptome-Based Bioassays and Fourier Transform Mass Spectrometry (Ft-Ms) Analysis. Water Research, 2014. 52(0): 73-82.

25.

Mesfioui, R., Love, N. G., Bronk, D. A., Mulholland, M. R., and Hatcher, P. G., Reactivity and Chemical Characterization of Effluent Organic Nitrogen from Wastewater Treatment Plants Determined by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Water Research, 2012. 46(3): 622-634.

26.

Zhang, H., Zhang, Y., Shi, Q., Ren, S., Yu, J., Ji, F., Luo, W., and Yang, M., Characterization of Low Molecular Weight Dissolved Natural Organic Matter Along the Treatment Trait of a Waterworks Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Water Research, 2012. 46(16): 5197-5204. 19


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

27.

Podgorski, D. C., Mckenna, A. M., Rodgers, R. P., Marshall, A. G., and Cooper, W. T., Selective Ionization of Dissolved Organic Nitrogen by Positive Ion Atmospheric Pressure Photoionization Coupled with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Analytical Chemistry, 2012. 84(11): 5085-5090.

28.

Shi, Q., Hou, D., Chung, K. H., Xu, C., Zhao, S., and Zhang, Y., Characterization of Heteroatom Compounds in a Crude Oil and Its Saturates, Aromatics, Resins, and Asphaltenes (Sara) and Non-Basic Nitrogen Fractions Analyzed by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy & Fuels, 2010. 24(4): 2545-2553.

29.

Liu, P., Shi, Q., Chung, K. H., Zhang, Y., Pan, N., Zhao, S., and Xu, C., Molecular Characterization of Sulfur Compounds in Venezuela Crude Oil and Its Sara Fractions by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy & Fuels, 2010. 24(9): 5089-5096.

30.

Zhang, L., Xu, Z., Shi, Q., Sun, X., Zhang, N., Zhang, Y., Chung, K. H., Xu, C., and Zhao, S., Molecular Characterization of Polar Heteroatom Species in Venezuela Orinoco Petroleum Vacuum Residue and Its Supercritical Fluid Extraction Subfractions. Energy & Fuels, 2012. 26(9): 5795-5803.

31.

Witt, M., Fuchser, J., and Koch, B. P., Fragmentation Studies of Fulvic Acids Using Collision Induced Dissociation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Analytical chemistry, 2009. 81(7): 2688-2694.

32.

Flerus, R., Lechtenfeld, O., Koch, B. P., Mccallister, S., Schmitt-Kopplin, P., Benner, R., Kaiser, K., and Kattner, G., A Molecular Perspective on the Ageing of Marine Dissolved Organic Matter. Biogeosciences, 2012. 9(6): 1935-1955.

33.

Kujawinski, E. B., Hatcher, P. G., and Freitas, M. A., High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Humic and Fulvic Acids: Improvements and Comparisons. Analytical chemistry, 2002. 74(2): 413-419.

34.

Sleighter, R. L., Liu, Z., Xue, J., and Hatcher, P. G., Multivariate Statistical Approaches for the Characterization of Dissolved Organic Matter Analyzed by Ultrahigh Resolution Mass Spectrometry. Environmental Science & Technology, 2010. 44(19): 7576-7582.

35.

Qian, K., Edwards, K. E., Siskin, M., Olmstead, W. N., Mennito, A. S., Dechert, G. J., and Hoosain, N. E., Desorption and Ionization of Heavy Petroleum Molecules and Measurement of Molecular Weight Distributions. Energy & fuels, 2007. 21(2): 1042-1047.

36.

Shi, Q., Xu, C., Zhao, S., Chung, K. H., Zhang, Y., and Gao, W., Characterization of Basic Nitrogen Species in Coker Gas Oils by Positive-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy & Fuels, 2009. 24(1): 563-569.

20


Page 20 of 28

Page 21 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure Captions

Figure 1 - Negative-ion FT-ICR MS broadband spectra of DOM in the raw water and its sub-fractions. Figure 2 - Mass scale-expanded segments (m/z 285) of negative-ion FT-ICR mass spectra for the raw water and its sub-fractions. Figure 3 - Mass scale-expanded segments (m/z 286) of negative-ion FT-ICR mass spectra for the raw water and its sub-fractions. Mass peaks with asterisk denote molecules with one 13C atom. Figure 4 - Mass scale-expanded segments (m/z 313) of negative-ion FT-ICR mass spectra for the Water II and its HOB fraction. Figure 5 - Relative abundance of O1-O13, N1O2-N1O11 and S1O2-S1O9 class species in DOM of the raw water and its sub-fractions. Figure 6 - Iso-abundance plots of DBE versus carbon numbers for O2, N1O4 and S1O4 class species in the raw water and its sub-fractions. Figure 7 - Mass scale-expanded segments (m/z 256) of positive-ion FT-ICR mass spectra for the raw water and its sub-fractions.

21


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 28

Figure 1

Raw water 150

200

250

300

350

400

450

500

m/z

HOA

150

200

250

300

350

400

450

500

m/z

HOB

150

200

250

300

350

400

450

500

m/z

HON 150

200

250

300

350

400

450

500

m/z

HIS 150

200

250

300

350

400

22


450

500

m/z

Page 23 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 2

C13H17O5S1 C12H13O6S1 285.00

C16H13O5

285.05

C17H17O4

C14H21O4S1 C14H21O6

C13H17O7 285.10

C18H21O3 C19H25O2 C15H25O3S1 C15H25O5

285.15

C16H29O4 285.20

Raw water C17H33O3 285.25

m/z

HOA

285.00

285.05

285.10 285.15 C15H22Cl1O3

285.20

285.25

m/z

HOB C16H16Cl1O2 C14H18Cl1O4 285.00

285.05

285.10

285.15

285.20

285.25

m/z

HON

285.00

285.05

285.10

285.15

285.20

285.25

m/z

HIS C11H22Cl1O6

285.00

285.05

285.10

285.15

285.20

23


285.25

m/z

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 28

Figure 3 C17H20N1O3 C18H24N1O2 C19H25O2* C16H16N1O4 C18H21O3* C15H12N1O5 C17H17O4* C16H13O5*

C14H8N1O6 286.00

286.05

286.10

286.15

286.20

Raw water

m/z

286.25

HOA

286.00

286.05

286.10 286.15 C15H22Cl1O3*

286.20

m/z

286.25

HOB C14H18Cl1O4*

286.00

286.05

286.10

C16H16Cl1O2* 286.15

C16H29O4* 286.20

C17H33O3* m/z

286.25

HON

286.00

286.05

286.10

286.15

286.20

m/z

286.25

HIS

286.00

286.05

286.10

286.15

286.20

24


286.25

m/z

Page 25 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 4 C14H17O6S1 C15H21O5S1

C19H21O4

C18H17O5

Raw water II

Int：2.0×108

C15H21O7 C16H25O4S1

C14H17O8

C16H25O6 C17H13O6 C20H25O3 C17H29O5 313.04

313.06

313.08

313.10

313.12

313.14

313.16

313.18

313.20

m/z

C17H26Cl1O3 C16H22Cl1O4

HOB II

313.04

C15H18Cl1O5

313.06

313.08

313.10

C18H30Cl1O2

313.12

313.14

313.16

25


313.18

313.20

m/z

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 28

Figure 5 Raw water

HOA

HOB

HON

HIS

26


DBE 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18

Page 27 of 28

Figure 6 22

22

O2

Raw water

N1O4

20

16

16

16

14

14

14

12

12

12

10

DBE

18

10

8

6

6

6

4

4

4

2

2

2

0 10

15

20

25

30

35

0 5

40

10

15

O2

HOA

30

35

40

5

HOA

18

16

16

16

14

14

14

12

12

12

10

DBE

18

10 8

8

6

6

6

4

4

4

2

2

0

0 15

20

25

30

35

22

HOB

15

20

25

30

35

5

40

22

HOB

N1O4

20

16

14

14

14

12

12

12

DBE

16

DBE

18

16

10 8

8

6

6

6

4

4

4

2

2

0

0 15

20

25

30

35

22

HON

15

20

25

30

35

40

5

HON

N1O4

20

20

16

16

14

14

14

12

12

12

DBE

16

DBE

18

10 8

8

6

6

6

4

4

4

2

2

0

0

15

20

25

30

35

40

10

15

20

25

30

35

40

5

22

HIS

14

14

14

12

12

12

DBE

16

16

DBE

18

10 8

8

6

6

6

4

4

4

2

2

2

0

0

20

25

Carbon Number

30

35

40

35

40

HON

10

15

20

25

30

35

40

HIS

10

8

15

30

S1O4

20

18

16

10

25

Carbon Number

N1O4

20

10

20

0

22

HIS

18

5

15

Carbon Number

O2

20

10

2

5

Carbon Number

22

40

10

8

10

35

HOB

S1O4

22

18

5

30

Carbon Number

18

10

25

0 10

Carbon Number

O2

20

20

2

5

40

Carbon Number

22

15

10

8

10

10

S1O4

20

18

5

40

Carbon Number

18

10

35

HOA

Carbon Number

O2

20

30

0 10

Carbon Number

22

25

2

5

40

20

10

8

10

15

S1O4

20

18

5

10

Carbon Number

N1O4

20

DBE

DBE

20

25

22

22

22

20

Carbon Number

Carbon Number

DBE

10

8

8

5

Raw water

S1O4

20

18

0

DBE

22

Raw water

18

DBE

DBE

20

DBE

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0 5

10

15

20

25

30

35

40

5

Carbon Number

27


10

15

20

25

Carbon Number

30

35

40

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 28

Figure 7 C17H22N1O1

C15H14N1O3

C18H26N1

Raw water

C16H18N1O2

256.06

256.10

256.14

256.18

256.22

m/z

HOA

256.06

256.10

256.14

256.18

256.22

m/z

HOB

256.06

256.10 C13H15N1O3Na

256.06

256.10

256.14 C14H19N1O2Na

256.18

256.22

C15H23N1O1Na

256.14

256.18

m/z

HON

256.22

m/z

HIS

256.06

256.10

256.14

256.18

28


256.22

m/z

Molecular Characterization of Dissolved Organic Matter and Its

Recommend Documents