Controlling Nitrosamines, Nitramines, and Amines in Amine-Based

Article pubs.acs.org/est

Controlling Nitrosamines, Nitramines, and Amines in Amine-Based CO2 Capture Systems with Continuous Ultraviolet and Ozone Treatment of Washwater Ning Dai*,† and William A. Mitch‡ †

Department of Civil, Structural and Environmental Engineering, University at Buffalo, Buffalo, New York 14260, United States Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States

‡

S Supporting Information *

ABSTRACT: Formation of nitrosamines and nitramines from reactions between flue gas NOx and the amines used in CO2 capture units has arisen as a significant concern. Washwater scrubbers can capture nitrosamines and nitramines. They can also capture amines, preventing formation of nitrosamines and nitramines downwind by amine reactions with ambient NOx. The continuous application of UV alone, or a combination of UV and ozone to the return line of a washwater treatment unit was evaluated to control the accumulation of nitrosamines, nitramines and amines in a laboratory-scale washwater unit. With model secondary amine solvents ranging from nonvolatile diethanolamine to volatile morpholine, application of 272−537 mJ/cm2 UV incident fluence alone reduced the accumulation of nitrosamines and nitramines by approximately an order of magnitude. Modeling indicated that the gains achieved by UV treatment should increase over time, because UV treatment converts the time dependence of nitrosamine accumulation from a quadratic to a linear function. Ozone (21 mg/L) maintained low steady-state concentrations of amines in the washwater. While modeling indicated that more than 80% of nitrosamine accumulation in the washwater was associated with reaction of washwater amines with residual NOx, a reduction in nitrosamine accumulation rates due to ozone oxidation of amines was not fully realized because the ozonation products of amines reduced nitrosamine photolysis rates by competing for photons.

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capture system treating a stream of 1500 m3/h flue gas using the benchmark solvent monoethanolamine, emissions of 4−57 ng/m3 nitrosamines and similar levels of nitramines were observed.4 Nitrosamines and nitramines form from the reactions between nitrogen oxides (NOx) in the flue gas and amines in the CO2 absorption solvent,5,6 and nitrosamines also form from the reactions between nitrite and amines in the desorber under high temperatures.7−9 Several nitrosamines are listed as probable human carcinogens in the U.S. EPA Integrated Risk Information System database, and are estimated to be associated with 10−6 lifetime excess cancer risk at low ng/ L levels in drinking water.10 Nitramines exhibit approximately an order of magnitude lower mutagenicity than their nitrosamine analogues11 and generally form at an order of magnitude lower concentrations in CO2 capture systems,3,6 but they are more persistent in the environment due to the lack of sunlight photolysis.12,13 Accordingly, the permit issued by the Norwegian Climate and Pollution Agency for the proposed full-scale CO2 capture facility at Mongstad limited the sum of

INTRODUCTION Amine-based CO2 absorption is the most mature technology for capturing CO2 from power plants postcombustion, as it has been used extensively for separating CO2 from natural gas and hydrogen at full-scale.1 Amine-based CO2 capture relies on the reversible reactions between amines and CO2 (e.g., reaction 1 for morpholine (MOR)). Flue gases are first passed through an absorber column, where a counter-current stream of an aqueous amine solution (solvent) absorbs CO2, removing it from the gas phase. The CO2-loaded amine solvent is then routed to a desorber where high temperatures reverse the absorption reactions, releasing high purity CO2 for compression and sequestration. The regenerated amine solvent is circulated back to the absorber for CO2 absorption. The gas leaving the absorber column is often passed through a washwater unit to remove amines and other contaminants prior to atmospheric release.

Received: March 17, 2015 Revised: June 9, 2015 Accepted: June 19, 2015

Recently, the detection of nitrosamines and nitramines in lab- and pilot-scale amine-based postcombustion CO2 capture systems has raised widespread concern.2−4 In a pilot-scale CO2 © XXXX American Chemical Society

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DOI: 10.1021/acs.est.5b01365 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology all nitrosamines and nitramines to 0.3 ng/m3 in downwind airsheds and 4 ng/L in downwind water supplies.14 In addition, this permit also limited the total emission of amines to 2800 kg per year,14 partially due to concerns for the potential of amines to form nitrosamines and nitramines via reactions with ambient NOx in the atmosphere.12,13 Several strategies have been proposed for minimizing emissions of nitrosamines, nitramines, and amines from amine-based CO2 capture systems, including selecting amines of low volatility,9 prioritizing primary and tertiary amines over secondary amines,9 employing NOx removal prior to CO2 capture,6 increasing desorber temperature to enhance nitrosamine thermal decay,15 and installing demister units to capture amine aerosol droplets.16 Alternatively, washwater units single- or multistage water scrubberscan capture the contaminants in the exhaust of the absorber units via physical absorption. However, we observed that as amines accumulated in the washwater, they could be nitrosated by residual NOx in the absorber exhaust, contributing to the accumulation of nitrosamines within the washwater unit.17 Frequent replacement of washwater is economically and environmentally undesirable. The power industry is already among the most intense consumers of freshwater, and the addition of CO2 capture units is anticipated to double their water demands.18 Treatment of washwater with oxidants to remove amines, nitrosamines, and nitramines could extend the lifetime of washwater. UV has been used for direct photolysis of nitrosamines during drinking water treatment,19,20 while ozone selectively oxidizes amines.17,21 Previously we applied ultraviolet (UV), ozone, and UV/hydrogen peroxide (H2O2) and ozone/H2O2 advanced oxidation treatments to washwater samples in batch mode.17 The low pressure UV (LP UV) fluence needed for 90% removal of specific model nitrosamines and nitramines ranged 340−4750 mJ/cm2 and 260−830 mJ/ cm2, respectively. Nitramines generally degraded faster than their nitrosamine analogues. We also observed higher efficiency of ozone than advanced oxidation processes for amine degradation. Feasibility studies of applying UV to treat waste streams and solvents from amine-based systems were also reported.22,23 These batch studies were useful for an initial assessment of the doses of each reagent needed to destroy individual target contaminants. However, they are insufficient to predict the treatment performance for recirculating washwater over long periods of time, because contaminants and their degradation products generated by the treatment processes are likely to accumulate as a result of the partial contaminant removal per treatment cycle, and may affect treatment efficiencies by altering solution characteristics. The goal of this study was to evaluate the efficacy of a labscale continuous washwater treatment system comprised of sequential UV and ozone units for controlling the concentrations of nitrosamines, nitramines, and amines in washwater, thereby minimizing their potential emissions. The UV unit was used primarily for destruction of nitrosamines and nitramines, while the ozone unit, positioned after the UV unit, targeted amine destruction. Our first objective was to experimentally evaluate the effects of different UV doses with and without ozone. Nitrosamines were the major target contaminants due to their high cancer potencies and formation rates. Considering the high potency of secondary amines to form nitrosamines,9 we evaluated three secondary amines as solvents: morpholine (MOR) as a model volatile amine, diethanolamine (DEA) as a model nonvolatile amine, and a commercial proprietary solvent

(PS). The second objective was to develop a model to predict the accumulation of nitrosamines in the washwater and the performance of the continuous treatment system in reducing nitrosamine accumulation over prolonged periods. A third objective was to understand whether ozone and UV treatments would exhibit synergy for nitrosamine control in continuous systems.

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MATERIALS AND METHODS Chemical sources are provided in the Supporting Information. Laboratory-Scale CO2 Capture and Washwater Treatment System. The CO2 capture system, comprised of an absorber and a washwater unit, is described in detail in the Supporting Information. A 2.5 M amine solution (200 mL), self-buffered without additional pH adjustment, was circulated through the absorber unit at 15 mL/min. Deionized water without buffer was used as washwater, with a circulation rate of 30 mL/min. The absorber column and solvent reservoir were maintained at 40 °C during reactor operation, while the washwater column temperature was not controlled. The synthetic flue gas consisted of 12% O2, 3.3% CO2, 15 ppmv NO, 3 ppmv NO2, 6.5% humidity, with N2 as the balance, at a total flow rate of 6 L/min. The mixture of N2, O2, and CO2 was first passed through a prewetting column containing deionized water at 40 °C to set the humidity prior to the addition of NO and NO2. Due to the lack of desorber unit, the system was preequilibrated with CO2 without NOx for 1 h, after which the NOx was turned on. The CO2 remained on throughout the experiment. The washwater treatment system included a medium pressure UV (MP UV) chamber and an ozone chamber. The washwater leaving the washwater column flowed by gravity to a cylindrical reservoir placed under a 450 W Hanovia medium pressure mercury lamp housed within a benchtop semicollimated beam reactor. An overflow outlet located at the opposite end of the reservoir to the inlet maintained the liquid volume at 400 mL and a depth of 33 mm. A magnetic stir bar constantly stirred the reservoir. The hydraulic retention time of the reservoir was 13.3 min at the 30 mL/min washwater circulation rate. A shutter was used to adjust the aperture between the UV lamp compartment and the reservoir compartment to alter the UV dose. After exiting the UV chamber, the washwater flowed by gravity to a 15 cm tall cylindrical ozone chamber. Ozone was generated by a Triogen LAB2B ozone generator from pure oxygen flowing at 0.4 L/ min, passed through a 50 mM phosphate buffer trap (pH 6) and purged through the washwater within the ozone chamber via a glass gas diffuser. Washwater was pumped from the ozone chamber back to the top of the washwater column at 30 mL/ min. The average liquid volume in the ozone chamber was 150 mL. There was approximately 30 mL liquid hold-up in the washwater column during reactor operation. In control experiments, the UV lamp and ozone generator were not turned on, but the flow path of the washwater and the purge gas (pure O2) flow rate in the ozone chamber remained the same to provide a comparable system configuration and account for contaminant losses associated with volatilization from the ozone chamber. Incident UV fluence was quantified by iodide-iodate actinometry for UV between 200 and 300 nm (see Supporting Information).24 We opted to use the incident fluence instead of average fluence in this study due to the continuous change in solution absorbance, and because the incident fluence reflects the energy inputs to the UV system. B

DOI: 10.1021/acs.est.5b01365 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Figure 1. Accumulation of (A) NMOR, (B) NO2-MOR, and (C) MOR in the washwater associated with MOR; the accumulation of (D) TONO and (E) DEA in the washwater associated with DEA; the accumulation of (F) TONO in the washwater associated with the commercial proprietary solvent. UV fluences: 1308 mJ/cm2 (UV-H), 537 mJ/cm2 (UV-M), and 272 mJ/cm2 (UV-L). Ozone dose: 0.44 mM.

formation potential. The average retention time of washwater in the ozone chamber was 5 min, and the time for the washwater to travel from the ozone chamber to the top of the washwater column was 18 s. Solvent and washwater samples collected at various times were analyzed for nitrite, nitrosamines, and nitramines. The volume of the absorber solvent reservoir was also monitored to permit the calculation of mass accumulation rates for the analytes when the solvent volume decreased due to volatilization. The increase in washwater volume over the experimental time scales was approximately 5%; the lack of condensation in the tubing connecting the absorber and washwater columns suggests that water vapor, not liquid entrainment, was responsible.

The ozone dose of the system was quantified as follows: when deionized water was used in both the absorber and washwater columns and the synthetic flue gas did not contain NOx, the steady state ozone concentration in the ozone chamber was 0.44 mM, measured by UV absorbance at 258 nm.25 Although the ozone concentration in the washwater returned to the top of the washwater column was 0.14 mM for this deionized water experiment, no ozone residual was measured when amine solvents were employed. Therefore, for washwater treated in the presence of amine solvents, the washwater received, and completely consumed, a 0.44 mM ozone dose. It is an important design criterion to achieve complete ozone depletion in the washwater return line between the ozone chamber and the washwater column to avoid the oxidation of NO to NO2 in the washwater unit, because the latter has a higher nitrosamine C

DOI: 10.1021/acs.est.5b01365 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology Sample Analysis. Detailed sample analysis procedures are available in the Supporting Information. Briefly, for experiments with MOR as solvent amine, N-nitrosomorpholine (NMOR) in the absorber solvent was analyzed directly with high performance liquid chromatography with UV detection (HPLC-UV); NMOR and N-nitromorpholine (NO2-MOR) in the washwater were analyzed by gas chromatography tandem mass spectrometry. For experiments with DEA and PS solvents, the total nitrosamine concentrations were monitored instead using a method described previously.3,9 MOR and DEA in the washwater samples were derivatized with 4-methoxybenzenesulfonyl chloride for analysis by HPLC-UV. Nitrate was measured colorimetrically using a WestCo SmartChem 200 discrete analyzer.

three low molecular weight N-nitrosamines (N-nitrosodimethylamine, N-nitrosomethylethylamine, and N-nitrosodiethylamine), which may form from the potential MOR fragmentation products, were measured in the ozonated washwater, but none was detected ( 0.93, Supporting Information Table SI-3; Figure 3). The comparison between

Combined UV-Ozone Treatment of Washwater. The anticipated synergy between UV and ozone for controlling nitrosamines in the washwater was not observed. Despite that amines were potent precursors for nitrosamine formation in the washwater, and the combined UV-ozone treatment effectively controlled amine concentrations in the washwater for both MOR and DEA solvents, ozone only slightly enhanced nitrosamine reduction in DEA washwater over 6 h, and did not show any effects in PS washwater over 10 h compared to UV alone. For MOR washwater, ozonation reduced NMOR accumulation early in the 6 h experiment, but this improvement vanished by the end of the experiment. The lack of synergy between UV and ozone was attributable to the decrease in UV efficiency as the ozonation products accumulated and competed for photons. Upon ozone treatment, MOR washwater exhibited strong absorbance in the 200−300 nm range compared to control and UV experiments. The absorbance increased rapidly within the first hour, after which only modest increases in absorbance were observed (e.g., absorbance at 254 nm increased by a factor of 3 over the first 0.85 h and only 12% from 0.85 to 4.35 h, Supporting Information Figure SI-4A). Nitrate was reported previously to be a major amine ozonation product.21,26 In the MOR washwater treated with UV-ozone, nitrate accumulated at a rate of 0.42 ± 0.014 mM/h. Considering that the MOR accumulation rate was 0.61 ± 0.012 mM/h in the control, nitrate accounted for up to 69% of the amino nitrogen. Oxidation of nitrite was not a significant source of nitrate, as the nitrite accumulation rate was only 1.5 μM/h in the control and UV experiments. Aldehydes, carboxylic acids, and amides may account for the rest of the MOR degradation products.12,21 Whereas aldehydes and carboxylic acids feature molar extinction coefficients 101−102 in the 200−300 nm UV range, nitrate and alkyl amides feature molar extinction coefficients on the order of 103−104 M−1· cm−1,28,29 and hence were likely to be the major contributors to the strong solution absorbance. The low synergy between ozone and UV can be quantitatively reflected in the model. For MOR ozone experiments, as MOR maintained a steady state concentration in the washwater (i.e., Rw_MOR = 0), eq 9 can be converted to eq 11:

Figure 3. Comparison of model prediction and experimental observation of NMOR accumulation in the washwater under UV treatment. UV fluences: 1308 mJ/cm2 (UV−H), 537 mJ/cm2 (UVM), and 272 mJ/cm2 (UV-L).

modeled and observed time profiles of NMOR accumulation is shown in Figure 3 and Supporting Information Table SI-3. The model overestimated NMOR accumulation for UV incident fluences of 1308 mJ/cm2 and 537 mJ/cm2 by 38% and 19%, respectively, and underestimated NMOR accumulation for 272 mJ/cm2 incident UV fluences by 40%. However, all estimates were within a factor of 2 of experimental observation, and the linear accumulation behavior is apparent from the experimental data. For modeling the DEA washwater with 537 mJ/cm2, kphoto was estimated to be 1.2 × 10−3 s−1, using a NDELA quantum yield of 0.23.17 Using the 5.38 × 10−4 μM·hr−2 A value calculated above from control experiments, the TONO accumulation rate in the presence of 537 mJ/cm2 MP UV was predicted to be 1.26 × 10−4 μM/h, lower than the observed 6.9 × 10−4 μM/h, but within the same order of magnitude (Supporting Information Table SI-3). The greater deviation of the modeled and experimental results for the DEA washwater may arise from the contribution of nitrosamine constituents other than NDELA (which may exhibit different kphoto values) to TONO. The conversion of quadratic to linear accumulation of nitrosamines in the washwater by UV treatment is of significance when considering the long-term operation of CO2 capture systems. For example, after 6 h operation, the difference in NMOR concentration in the washwater between the control and UV treatment with 1308 mJ/cm2 incident fluence was 70-fold, but would be 700-fold after 60 h. Although the UV dose for a given nitrosamine reduction at a pilot- or fullscale facility will vary depending on the system operating conditions, the model can serve as the basis for a preliminary design of continuous UV treatment systems. The information required to determine the design parameters include (1) plantspecific information: nitrosamine accumulation in the absorber solvent, amine accumulation in the washwater, and NOx removal by the absorber; and (2) laboratory-determined physiochemical properties of chemicals: photolysis rate constants of nitrosamines and their Henry’s Law constants.

⎛ Qg⎞ dC w ⎟⎟t + k w[MOR]ss = ⎜⎜KHks[MOR]s [NO]in [NO2 ]in dt Vw ⎠ ⎝ [NO]ex [NO2 ]ex − k photoCw

(11)

where [MOR]ss is the steady-state concentration of MOR in the washwater (approximately 0.79 mM). Solving eq 11 gives the time profile of NMOR concentration under UV-ozone treatment (eq 12): ⎛ ⎞ B′ A′ ⎟ A′ − Cw = ⎜⎜ (1 − e−k photot) + t 2⎟ k photo (k photo) ⎠ ⎝ k photo

(12)

where A′ = KHks[MOR]s[NO]in[NO2]inQg/Vw = P and B′kw[MOR]ss[NO]ex[NO2]ex. As [MOR]ss was not significantly different from [MOR]0, B′ is negligible and eq 12 can be simplified to eq 12A. Cw = − G

A′ A′ (1 − e−k photot) + t k photo (k photo)2

(12A)

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Environmental Science & Technology Similar to eq 10A (UV treatment alone), the second term in eq 12A determines the time dependence of nitrosamine accumulation under combined UV-ozone treatment. Compared to UV treatment alone, where nitrosamine accumulation was a result of both mass transfer from the absorber and formation from reactions of amines with residual NOx in the washwater (i.e., A = P + Q), ozone minimized the importance of amine reactions with NOx in the washwater (Q) by degrading amines such that only volatilization was important (i.e., A′ = P). Since P was approximately 20% of A, an 80% reduction in nitrosamine formation would be expected due to ozonation. However, the increase in UV absorbance due to ozonation reduced kphoto by 33% from 1.1 × 10−3 s−1 to 7.1 × 10−4 s−1 during the first 0.85 h, partially offsetting the gains achieved by amine destruction, such that a net decrease of only 70% in nitrosamine accumulation rates would be anticipated. Indeed, the experimentally determined initial accumulation rate of NMOR during UV-ozone treatment was 58% lower than that during UV treatment alone, agreeing reasonably well with the model prediction. The solution absorbance continued to increase, although at a slower rate, reducing kphoto to 6.6 × 10−4 s−1 after 4.35 h. The decrease in kphoto would further reduce the gains achieved by ozonation, but because the increase in solution absorbance leveled out, a constant nitrosamine accumulation rate is anticipated over longer treatment periods. Due to the constraints of the experimental setup, a single dose of ozone (0.44 mM) was tested in this study. Future work should evaluate the extent to which lower ozone doses could hinder amine accumulation while minimizing the accumulation of strongly absorbing ozonation products. Overall, for nitrosamine control, the gains of ozonation from amine removal can be offset by the decrease in UV efficiency resulting from the increase in solution absorbance. The degree to which the reduction in kphoto offsets the gains achieved by ozonation over extended reactor operation may vary among different amine solvents. Amines of lower volatility would accumulate at lower rates in the washwater and produce fewer photon-absorbing products upon ozonation than those of high volatility, as suggested by the weaker absorbance of DEA washwater than MOR washwater after 4.5 h (Supporting Information Figure SI-4). Therefore, less volatile amines would experience less of a reduction in kphoto. However, regardless of amine volatility, ozone achieved effective amine control. Amine emissions remain a concern due to the potential for them to form nitrosamines or nitramines upon reaction with atmospheric NOx.12,13 Maintaining a low steady-state amine concentration in the washwater by ozonation can increase the physical absorption efficiency for amine removal and hence significantly extend the washwater lifetime. Environmental Relevance. In this study, three secondary amines, including a volatile amine (MOR), a nonvolatile amine (DEA), and a commercial proprietary solvent (PS), were tested. Secondary amines exhibit higher reactivity toward nitrosamine formation than tertiary and primary amines,9 and hence represent challenge cases. The lab-scale UV-ozone continuous treatment systems exhibited similar effects for all three amine solvents. Although control of nitramine accumulation in the washwater was only verified for the MOR solvent, nitramines from other amine solvents likely were also effectively controlled, as previous research has indicated that UV photolysis rates often are higher for nitramines compared to nitrosamines.17

MP UV reduced nitrosamine accumulation rates in the washwater by more than 85% over 6 h with fluences of 272 mJ/ cm2 (MOR washwater) and 537 mJ/cm2 (DEA and PS washwater). Our previous batch experiments with a monochromatic low pressure (LP) mercury UV lamp (emitting at 254 nm) indicated that 90% removal of NMOR at pH 8 required 340 mJ/cm2 fluence,17 similar to the findings in the current study with a polychromatic MP UV lamp. These results agreed with previous research on N-nitrosodimethylamine indicating that quantum yields for direct photolysis were similar over the 200−300 nm wavelength range.19 The higher output of MP UV lamps may be advantageous. Modeling indicated that UV treatment converted the time dependence of nitrosamine accumulation from a quadratic to a linear function, suggesting that the benefits of employing UV treatment would be more pronounced than observed in this study when considering time scales relevant to large-scale capture systems. For example, for the MOR solvent in our reactor, if washwater were to be replaced when NMOR concentrations reached 1 mM, 537 mJ/cm2 incident UV fluence would extend the washwater lifetime from 3 days to 973 days. The UV fluence requirements were comparable to those used for drinking water treatment: UV fluence of 20−120 mJ/cm2 is typical for disinfection, but up to 300 mJ/cm2 fluence may be needed for virus removal;30 500−1000 mJ/cm2 is typical for advanced oxidation processes.31 Ozone effectively controlled amine accumulation in the washwater. Amine emissions have been a concern due to the potential formation of nitrosamines and nitramines downwind of CO2 capture plants by reactions between amines and ambient NOx. Additionally, modeling indicated that reactions of residual NOx with amines accumulating in the washwater accounted for more than 80% of the nitrosamine accumulation in the washwater for both volatile (MOR) and nonvolatile (DEA) amine solvents. Although oxidation of amines by ozone was expected to further reduce nitrosamine accumulation rates, the reduction was partially offset because the added absorbance attributed to ozone oxidation products reduced nitrosamine photolysis rates. In full-scale facilities, multistage washwater units are being considered and it is common to reclaim amines in the first-stage washwater. Therefore, ozone treatment, if employed, will likely target the second-stage washwater, which requires a lower ozone demand and hence alleviates the screening effects from ozonation products. Lastly, if ozone is included in the washwater treatment system, its dose should be carefully controlled. To avoid the oxidation of NO to NO2, complete ozone depletion should be achieved in the washwater return line between the ozone chamber and the washwater column. This was satisfied by the 0.44 mM (21 mg/L) ozone dose used in our experiments. Our previous batch study indicated that the ozone dose required for 90% amine removal in pilot-scale washwater samples was in 5 to 12 molar excess compared to the amine concentration.17 In contrast, the 0.44 mM (21 mg/L) ozone dose employed in this study was less than the MOR concentration in the washwater throughout the experiment, but was sufficient to prevent amine accumulation. Future work should evaluate the extent to which lower ozone doses could hinder amine accumulation. If successful, lower doses could minimize the increases in solution absorbance, such that the ozone would hinder the accumulation of amines without interfering with nitrosamine and nitramine destruction by UV. For comparison, ozone doses for drinking water treatment are ∼1−5 mg/L.31 H

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(16) Khakharia, P.; Kvamsdal, H. M.; da Silva, E. F.; Vlugt, T. J. H.; Goetheer, E. Field study of a Brownian Demister Unit to reduce aerosol based emission from a post combustion CO2 capture plant. Int. J. Greenhouse Gas Control 2014, 28, 57−64. (17) Shah, A. D.; Dai, N.; Mitch, W. A. Application of ultraviolet, ozone, and advanced oxidation treatments to washwaters to destroy nitrosamines, nitramines, amines, and aldehydes formed during aminebased carbon capture. Environ. Sci. Technol. 2013, 47, 2799−2808. (18) Zhai, H. B.; Rubin, E. S.; Versteeg, P. L. Water use at pulverized coal power plants with postcombustion carbon capture and storage. Environ. Sci. Technol. 2011, 45, 2479−2485. (19) Sharpless, C. M.; Linden, K. G. Experimental and model comparisons of low- and medium-pressure Hg lamps for the direct and H2O2 assisted UV photodegradation of N-nitrosodimethylamine in simulated drinking water. Environ. Sci. Technol. 2003, 37, 1933−1940. (20) Stefan, M. I.; Bolton, J. R. UV direct photolysis of Nnitrosodimethylamine (NDMA): Kinetic and product study. Helv. Chim. Acta 2002, 85, 1416−1426. (21) von Gunten, U. Ozonation of drinking water: Part I. Oxidation kinetics and product formation. Water Res. 2003, 37, 1443−1467. (22) Jackson, P.; Attalla, M. Ultra-violet treatment as a strategy for destruction of degradation products from amine based post combustion CO2 capture. Nitrosamine degradation by UV light in post-combustion CO2 capture: Effect of solvent matrix. Energy Procedia 2013, 37, 1543−1553. (23) Mercader, F. D.; Voice, A. K.; Trap, H.; Goetheer, E. L. V. Nitrosamine degradation by UV light in post-combustion CO2 capture: Effect of solvent matrix. Energy Procedia 2013, 37, 701−716. (24) Rahn, R. O.; Stefan, M. I.; Bolton, J. R.; Goren, E.; Shaw, P. S.; Lykke, K. R. Quantum yield of the iodide-iodate chemical actinometer: Dependence on wavelength and concentration. Photochem. Photobiol. 2003, 78, 146−152. (25) Huber, M. M.; Canonica, S.; Park, G. Y.; Von Gunten, U. Oxidation of pharmaceuticals during ozonation and advanced oxidation processes. Environ. Sci. Technol. 2003, 37, 1016−1024. (26) Pietsch, J.; Schmidt, W.; Brauch, H. J.; Worch, E. Kinetic and mechanistic studies of the ozonation of alicyclic amines. Ozone-Sci. Eng. 1999, 21, 23−37. (27) Royal Society of Chemistry, ChemSpider. http://www. chemspider.com (accessed March 3, 2015). (28) Ferree, M. A.; Shannon, R. D. Evaluation of a second derivative UV/visible spectroscopy technique for nitrate and total nitrogen analysis of wastewater samples. Water Res. 2001, 35, 327−332. (29) National Institute of Standards and Technology, NIST Chemistry WebBook. http://webbook.nist.gov/chemistry/ (accessed March 3, 2015). (30) Hijnen, W. A. M.; Beerendonk, E. F.; Medema, G. J. Inactivation credit of UV radiation for viruses, bacteria and protozoan (oo)cysts in water: A review. Water Res. 2006, 40, 3−22. (31) Crittenden, J. C.; Trussell, R. R.; Hand, D. W.; Howe, K. J.; Tchobanoglous, G. Water Treatment: Principles and Design, 3rd ed.; Wiley: NJ, 2012; pp 903−1032.

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.5b01365.

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AUTHOR INFORMATION

Corresponding Author

*Phone: (716) 645-4015; fax: (716) 645-3667; e-mail: ningdai@buffalo.edu. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Powerspan Corporation (Portsmouth, NH) for providing the proprietary solvent. REFERENCES

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DOI: 10.1021/acs.est.5b01365 Environ. Sci. Technol. XXXX, XXX, XXX−XXX