Selective Removal of Nitrosamines from a Model ... - ACS Publications

Subscriber access provided by UNIVERSITY OF ADELAIDE LIBRARIES

Article

Selective Removal of Nitrosamines from a Model Amine Carbon Capture Waterwash using Low Cost Activated Carbon Sorbents Leland R. Widger, Megan Combs, Amit R. Lohe, Cameron A. Lippert, Jesse G. Thompson, and Kunlei Liu Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b02806 • Publication Date (Web): 09 Aug 2017 Downloaded from http://pubs.acs.org on August 9, 2017

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.

Environmental Science & Technology 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 31

Environmental Science & Technology

1

Selective Removal of Nitrosamines from a Model Amine Carbon Capture Waterwash using

2

Low Cost Activated Carbon Sorbents

3

Leland R. Widger1, Megan Combs1, Amit R. Lohe1, Cameron A. Lippert1, Jesse G. Thompson1,

4

and Kunlei Liu1,2*

5

1

6

Lexington, KY 40511, United States

7

2

8

Building, Lexington, KY 40506, United States

9

*To whom correspondence should be addressed, Phone: +1 (859)-257-0293, Fax: +1 859-257-

10

Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive,

Department of Mechanical Engineering, University of Kentucky, 151 Ralph G. Anderson

0302, e-mail: [email protected]

11 12

Abstract

13

Nitrosamines generated in the amine solvent loop of post combustion carbon capture systems are

14

potent carcinogens, and their emission could pose a serious threat to the environment or human

15

health. Nitrosamine emission control strategies are critical for the success of amine-based carbon

16

capture as the technology approaches industrial-scale deployment. Waterwash systems have been

17

used to control volatile and aerosol emissions, including nitrosamines, from carbon capture

18

plants, but it is still necessary to remove or destroy nitrosamines in the circulating waterwash to

19

prevent their subsequent emission into the environment. In this study, a cost-effective method for

20

selectively removing nitrosamines from the absorber waterwash effluent with activated carbon

21

sorbents was developed to reduce the environmental impact associated with amine-based carbon

22

capture. The results show that the commercial activated carbon sorbents tested have a high

23

capacity and selectively for nitrosamines over the parent solvent amines, with capacities up to

ACS Paragon Plus Environment


24

190 mg/g carbon, under simulated amine waterwash conditions. To further reduce costs, an

25

aerobic thermal sorbent regeneration step was also examined due to the low thermal stability of

26

nitrosamines. To model the effect of oxidation on the sorbent performance, thermal and acid

27

oxidized sorbents were also prepared from the commercial sorbents and analyzed. The chemical

28

and physical properties of nitrosamines, the parent amine, and the influence of the physical

29

properties of the carbon sorbents on nitrosamine adsorption was examined. Key sorbent

30

properties included the sorbent hydrophilicity/hydrophobicity, surface pKa of the sorbent, and

31

chemical structure of the parent amine and nitrosamine.

32 33

Introduction

34

Significant challenges exist in controlling the emissions of the amine solvents and amine

35

degradation products from post-combustion carbon capture systems (CCS). CCS amine

36

emissions increase solvent makeup rates and can release hazardous compounds, such as

37

carcinogenic nitrosamines, into the environment.1 Nitrosamines can form from the reaction of

38

NOx in coal combustion flue gas with secondary amines, either as the principle amine used as the

39

CO2 capture solvent, or from degradation of primary or tertiary amines that yield secondary

40

amine products which can accumulate in the amine solvent loop and waterwash sections.2-10

41 42

First identified as carcinogens in the 1950s,3 nitrosamines have been studied extensively and

43

show both carcinogenic and mutanogenic effects in animals.11-12 The US-EPA has classified

44

nitrosamines as priority toxic pollutants on the Code of Federal Regulations (40 CFR 131.36)

45

and the International Agency for Research on Cancer have listed nitrosamines as likely human

46

carcinogens.12-13 Nitrosamines are not only generated in amine-based carbon capture systems,


Page 2 of 31

Page 3 of 31


47

but are also found in food products, cosmetics, tobacco, and are detected in waste water

48

treatment processes.14-17 Several states have reported values for nitrosamines in water systems

49

including California, which has a public health goal value for NDMA in treated water of 3

50

ng/L18, and Massachusetts, with a NDMA regulatory limit of 10 ng/L.19 The US EPA has also

51

made recommendations to limit environmental nitrosamine levels in lakes and streams (NDMA

52

at 0.69 ng/L) to prevent contaminated drinking water or fish from impacting public health.12

53 54

The first report of nitrosamines in amine-based carbon capture is from Strazisar and coworkers,

55

where a total nitrosamine concentration of 2.91 µmol/mL was identified in a lean MEA

56

solvent.20 Since then, there has been significant effort to understand the source and properties of

57

nitrosamines found in amine solvents and waterwash sections of CCS systems. Voice,21 Dai,5

58

and others22 have identified a variety of nitrosamines in simulated and pilot plant studies from

59

solvents including MEA, PZ, and AMP. The concentration of nitrosamines in CCS systems can

60

vary greatly, depending on the solvent, operating conditions, and where in the process samples

61

are collected. For example, Dai and coworkers identified 6.7 µM of nitrosamines in a MEA

62

solvent and 1063 µM in a AMP/PZ solvent blend.5 Nitrosamines were also identified at 56 µM

63

in the washwater section, at the top of the absorber, in the same AMP/PZ testing campaign.

64 65

The Norwegian Institute of Public Health (NIPH) initially proposed an emission limit of 0.3

66

ng/m3, for combined nitrosamines and nitramines, in the environmental permit for the carbon

67

capture Technology Centre Mongstad as their impact assessments warn of the potential

68

environmental hazards from nitrosamine emissions at amine-based carbon capture systems.23-24



69

In order to reduce the potential environmental and health impact, significant effort has been

70

made towards the prevention or destruction of nitrosamines for a variety of applications.

71 72

Nitrite scavenging has been examined to reduce nitrosamine formation in amine solvents.

73

Previous work from our group showed that nitrite scavengers are effective at inhibiting the

74

formation of nitrosomorpholine from morpholine by removing the key nitrite reactant after it is

75

formed from NOx dissolving in the amine solvent.25 Several other additives, including ascorbic

76

acid and cysteine, can be reasonably effective at reducing the formation of MNPZ in a PZ/AMP

77

solvent.21

78 79

Destroying nitrosamines after they have formed is another mitigation strategy that has been

80

explored. Sørensen et al. reported on the photodegradation of nitrosamines in natural waters

81

environments similar to those expected in areas surrounding power plants with CO2 capture

82

systems using aqueous amines.26 Under these conditions, nitrosamine can be expected to degrade

83

when exposed to direct sunlight within 20 minutes to 2 hours, at summer and winter type

84

environmental conditions, respectively.

85

nitrosamine would only occur during daylight hours, while nitrosamines emitted at night have

86

the potential to persist in the environment.

This study did note that photodegradation of

87 88

In lab scale UV irradiation experiments, nitrosamine half-lives ranged from 4-8 minutes under

89

batch reactor conditions.27 The decomposition of the nitrosamines by UV irradiation occurred

90

through N-N bond cleavage, which was confirmed by monitoring formation of nitrate/nitrite in

91

the solvent. A similar study also showed that nitrosamines (NDMA and NDELA) can be


Page 4 of 31

Page 5 of 31


92

decomposed using UV irradiation in both water wash solutions and concentrated amine solvents,

93

such as 30% MEA and 50% DEA .28 Formation of nitrite/nitrate was also observed in these batch

94

scale experiments, further confirming the proposed UV degradation route of N-N bond cleavage.

95

Nitrosamine decomposition by UV irradiation was significantly more efficient in a simulated

96

waterwash solution than in the concentrated amine solution (33 times slower) due to competitive

97

degradation of the amine over the nitrosamine.

98 99

Using a combination of UV and UV plus ozone to decompose nitrosamines from CO2 capture

100

waterwash solutions was studied, but the effectiveness of the UV + ozone treatment was

101

impacted by ozonation byproducts formed by decomposition of residual amine as it competed for

102

photons and reduced the impact of the UV.4 Overall, the ozone treatment reduced the formation

103

of nitrosamines in the waterwash, but since this method also decomposed amines it may only be

104

applicable with multi-stage waterwashes in the 2nd or 3rd stage to minimize amine destruction.

105

In contrast to these results, Fujioka et al. showed that ozonation can actually lead to an increase

106

in nitrosamine formation at certain ozone doses.29 Other reports, including from Chuang et al.,30

107

showed that ozonation, combined with biofiltration (nitrified growth on activated carbon) was

108

able to reduce NDMA concentration formed during wastewater treatment (chloramination)

109

relative to an untreated sample. Nitrosamines can be effectively mitigated from wastewater

110

treatment facilities where activated sludge and biological activated carbon are included in the

111

treatment train, along with high dose UV combined with reverse osmosis filtration, although the

112

later approach is not favored due to it relatively high cost to remove the low concentration

113

nitrosamine pollutants.31

114



115

The catalytic reduction of nitrosamines back to their parent amines (amine recovery) has been

116

reported using palladium, nickel and iron based redox metal catalysts. In the study by Chandan et

117

al., the Ni based catalyst showed excellent activity (>95%) toward the destruction of 100 mg/L

118

nitrosopyrrolidine in 5 mol/kg MEA solution at 120 psi hydrogen pressure and 120 °C

119

temperature in 4 hours.32 Fly ash was also shown to have some activity towards catalytic

120

nitrosamine reduction with H2.33 The catalytic destruction of nitrosamines from tobacco smoke

121

using crystalline aluminosilicate zeolites has also been reported.34

122 123

Thermal decomposition of nitrosamines directly in amine solvents was reported using a batch

124

reactor and cycling system and showed that the thermal degradation of (mono-)nitrosopiperazine

125

(NPZ) at 150 °C could be fitted with a first order rate law over several days.21 The thermal

126

decomposition of NDELA, NHEGly (nitroso-2(hydroxyethyl) glycine) and NPZ in a batch

127

reactors at 150 °C was also reported.35 The nitrosamine thermal decomposition rate also showed

128

a dependence to base strength, with higher pH leading to higher decomposition rates. While

129

thermal treatment may be effective in treating concentrated amine solutions, such as in a thermal

130

reclaimer, treating a waterwash solution in the same manner may be slower and less effective

131

due to the lower nitrosamine concentration and lower pH of waterwash solutions. Nielsen et al.

132

also showed the thermal degradation of NPZ and formation of NPZ in the absorber yielded a

133

steady state concentration of near 1 mmol/kg.36 In contrast to these reports, nitrosamine

134

formation from morpholine is enhanced at higher temperatures up to 145 °C.25 Therefore, the

135

thermal degradation temperature may vary for a different of nitrosamines, and more research is

136

likely necessary to tailor this approach for different solvents and solvent blends where different

137

nitrosamines are expected to form.


Page 6 of 31

Page 7 of 31


138 139

Nitrosamines have been selectively adsorbed and separated from gases and solutions using

140

aluminosilicate zeolites.34 The zeolite structure, specifically the pore size and surface

141

hydrophobicity, can have a large impact on the adsorption of nitrosamines. A variety of

142

adsorbent materials to remove tobacco specific nitrosamines from liquid solutions including

143

zeolites, impregnated and calcinated activated carbon, acid impregnated activated carbon and

144

ion-exchange modified activated carbon have also been studied.37

145 146

While each of these nitrosamine mitigation methods has shown promise, the relative complexity

147

and/or cost of these may be prohibitive on a large industrial CCS scale, requiring simpler and

148

more cost effective approaches to be developed. There are widespread existing applications for

149

activated carbon beds in various industries, and existing units can be adapted to accept a wide

150

range of sorbent materials; including potable and wastewater treatment, decolorization of food

151

products, air purification, automotive emission control, and solvent vapor recovery.38 In this

152

study, a novel cost-effective nitrosamine removal technology that can easily retrofit onto new or

153

existing waterwash sections of carbon capture systems is described.

154 155

The vapor pressure of nitrosamines can lead to gas phase partitioning of these degradation

156

products out of the amine solvent loop where they are subsequently captured and concentrated in

157

a waterwash.39 These waterwash emission control systems, located on top of the absorber, have

158

been developed to reduce amine emissions by capturing mechanical emissions (entrainment) into

159

a separate water circulation loop.40-41 However, the removal/destruction of nitrosamines at this

160

point is still critical in order to prevent the subsequent concentration and emission of the



Page 8 of 31

161

nitrosamines into the environment. The lower concentration of solvent amine in the waterwash

162

section, as opposed to the solvent loop, makes the water-wash location a better location for the

163

selective removal of the relative low concentration nitrosamine contaminants. In a commercial

164

sized system, the carbon filter bed will be designed to receive a continuous slip of the waterwash

165

solution to maintain low levels of nitrosamines in the washing water and prevent partitioning into

166

the vapor phase and emitting from the CCS.

167 168

Regeneration and reuse of the carbon sorbent can also be utilized to extend sorbent lifetime and

169

keep the cost of this type of system low. Typical carbon regeneration is done under inert

170

atmosphere at temperatures between 700 – 1000 °C,42 while some nitrosamines can be

171

decomposed at much lower temperatures, ex. NPZ at 150 °C.7,

172

material costs and handling low, a thermal regeneration step could be applied at lower

173

temperatures and in air, further reducing cost. As part of this study, both of the commercial

174

activated carbon sorbents were thermally oxidized, characterized, and tested for nitrosamine

175

adsorption and selectivity, as a model for how these sorbents might preform after aerobic thermal

176

regeneration. In addition, an acid treated sorbent was also characterized and tested as an extreme

177

scenario to maximize differences in surface functionalization.

21

Therefore, in order to keep

178 179

Materials and Methods

180

Circulating sorbent bed apparatus

181

Adsorption of nitrosamines by the sorbents was evaluated in a circulating bed apparatus (Figure

182

1). The experimental apparatus consists of a peristaltic pump, a 1 L reservoir and a packed bed of

183

the sorbent materials. Adsorption experiments were performed with 500 mL of solution cycled


Page 9 of 31


184

through approximately 5 g of sorbent at a flow rate of 50 mL/min for 4 hours to ensure the

185

carbon bed had reached equilibrium (Figure S1). A sample of the solution was collected at the

186

beginning and end of each experiment to measure the baseline and final nitrosamine

187

concentrations, with total adsorption determined by the difference. The activated carbon sorbent

188

was pre-wetted before each experiment. The relative size of the apparatus was selected to

189

minimize the amount of nitrosamine used in these experiments while still producing scalable

190

adsorption results.

191 192

Figure 1. Schematic of circulating sorbent bed apparatus.

193 194

Commercial activated carbon (8-30 mesh, Calgon Carbon Corporation) and coconut charcoal

195

activated carbon (8-12 mesh; Aqua Solutions Inc.) were selected for their widespread

196

availability, low cost, and large particle size (lower pressure drop inside a packed sorbent bed).

197

From these commercial carbons, a series of surface-modified sorbents were produced by

198

subjecting the commercial material to thermal oxidation in air, and an acid treatment with HNO3.

199

Thermal oxidation was performed by exposing the carbon material to 300 °C for 72 hours under

200

ambient air conditions. The acid treated carbon sorbent was produced by refluxing with



201

concentrated nitric acid (69%, VWR) for 24 hours, followed by thoroughly washing with water

202

to remove any residual acid from the material.37 The pH of representative simulated washwater

203

samples was examined and shown to be constant over the range of these experiments (see

204

supporting information), therefore the impact of pH on nitrosamine adsorption can be considered

205

to be negligible.

Page 10 of 31

206 207

Nitrosamine Analyses. An Agilent 1260 Infinity high-performance liquid chromatography

208

(HPLC) coupled to a 6224 series time-of-flight mass spectrometer (TOF-MS) was used to

209

measure the concentration of nitrosamines. The HPLC was equipped with a reverse phase

210

Zorbax Eclipse Plus Phenyl-Hexyl column (3.0 mm x 100 mm x 3.5 µm). Two MS sources were

211

used to analyze the nitrosamines in these experiments. Electrospray ionization (ESI) was used

212

analyze the concentrations of nitrosopyrrolidine (NPY), nitrosopiperazine (NPZ), and

213

nitrosodiethylamine (NDEA). Atmospheric pressure chemical ionization (APCI) was used to

214

measure the concentration of nitrosodiethanolamine (NDELA). When analyzing with ESI, an

215

isocratic mobile phase of 60:40 acetonitrile (ACN; LC/MS grade, VWR) and 0.01% formic acid

216

(LC/MS grade, Fisher Scientific) in water (LC/MS grade, VWR) was used with a flow rate of 0.3

217

mL/min with a 5 µL injected volume. With APCI, a 50:50 mixture of ACN and 0.01% formic

218

acid in water with a flow rate of 0.8 mL/min and a 10 µL injection volume. Reported values are

219

from an average of 3 injections for each sample, with error bars determined as the percent

220

standard deviation from the average peak area value from these injections. A calibration curve

221

was established at the beginning of each analysis using neat nitrosamine standards including

222

NPY (99%, Sigma Aldrich), NPZ (99%, Sigma Aldrich), NDEA (> 99%, Sigma Aldrich) and


Page 11 of 31


223

NDELA (Toronto Research Chemicals, Inc). Simulated water wash solutions were prepared with

224

pure monoethanolamine (> 99%, Alfa Aesar) and piperazine (PZ) (99%, Acros Organics).

225 226

Due to the toxicity associated with the handling of concentrated nitrosamine solutions, replicate

227

experiments were minimized where possible. Select representative nitrosamine absorption

228

experiments were repeated and showed deviation < 2% (see supporting information Figure S3).

229 230

Material Characterization. Scanning electron microscopy (SEM) and energy dispersive

231

spectroscopy (EDS) was collected on a Hitachi S-4800 field-emission scanning electron

232

microscope with a voltage of 15 kV and a current of 20 µA. Brunauer–Emmett–Teller (BET) N2

233

adsorption/desorption isotherms were measured using an ASAP2020 surface area and porosity

234

analyzer (Micromeritics) with 50 mg of sample degassed at 160 °C for 12 hours. Cumulative

235

pore volume was calculated via the non-localized density functional theory (NLDFT) provided

236

by Micromeritics.

237 238

Surface pKa of the activated carbon was determined using a method adapted from Schwarz.43 In

239

a typical experiment, 500 mg of carbon material was placed in a glass vial with 20 mL of

240

degassed DI water, sealed and stirred for 48 hours. The pH of the resulting solution was then

241

measured. The surface pKa measurements of each carbon was performed in triplicate.

242 243

Boehm titrations were performed to quantify acid and base sites on the surface of the commercial

244

and modified carbon sorbents using a method adapted from Schwarz.43 In a typical procedure,

245

200 mg of the carbon sorbent was placed into a sealed vial with 20.0 mL of standardized 0.02 M



Page 12 of 31

246

HCl or 0.02 M NaOH. After stirring for 48 h, the solution was filtered and back titrated using

247

phenolphthalein as an indicator with standardized 0.02 M NaOH (to measure base sites) or 0.02

248

M HCl (to measure acid sites). The total adsorbed moles of acid/base were then determined as

249

mmol of acid/base per gram of carbon material. Each carbon was analyzed in duplicate and each

250

titration was performed in triplicate.

251 252

Isotherm Modeling. The nonlinear Langumir and Freundlich models were applied to the

253

adsorption isotherm data (vide infra). The constants for the Langumir (qm, kL) and Freundlich (n,

254

kF) isotherm models were calculated using MS Excel 2013 solver, and verified in SigmaPlot

255

(version 13.0). Weighted standard error was obtained from nonlinear regression in SigmaPlot.

256

The weighted standard error and goodness-of-fit (R2) values suggested that Langumir adsorption

257

best fit the experimental data (Table S2).

258 259

Thermal Regeneration. In order to test the possibility of regenerating the sorbents, two samples

260

of commercial coconut charcoal activated carbon were pre-saturated by exposure to a 1000 ppm

261

NPY solution for 4 hr. The sorbent was removed and placed in a 200 °C oven for 20 h to

262

decompose and remove the nitrosamine regenerate the sorbent. The carbon sorbents were then

263

re-exposed to solutions containing a high concentration (1000 ppm) and low concentration (15

264

ppm) of NPY.

265 266

Results and Discussion

267

Sorbent Characterization. The physical and chemical properties of the commercial and

268

oxidized carbon sorbents were characterized by SEM, EDS, BET, pH, and Boehm titration


Page 13 of 31


269

(Table 1). The SEM images in Figure 2 show little noticeable qualitative change to the

270

morphology of activated carbon samples upon thermal and acid treatment. Comparing the

271

surface carbon and oxygen content for the sorbent series, Table 1 shows increased oxygen

272

content and a lower corresponding carbon content, on the surface upon oxidation (see supporting

273

information, Table S1, for full EDS results). Thermal treatment increases the oxygen content of

274

coconut charcoal from 5.25 to 14.81%, while the activated carbon only increases from 6.75 to

275

8.16%. The acid treated coconut charcoal had the highest oxygen content, at 23.87%. The BET

276

results also shows changes in the surface area and pore volume upon thermal and acid treatment

277

of the coconut charcoal, but no change upon thermal treatment of the activated carbon. The

278

surface area and pore volumes of the coconut charcoal increase upon thermal treatment and

279

decrease with acid treatment, while the pore size remains constant over the series.

280

Table 1. Characterization data for activated carbon sorbents tested

Carbon Type

Commercial Coconut Charcoal C: 92.11 O: 5.25

Oxidized Coconut Charcoal C: 80.56 O: 14.81

Acid Coconut Charcoal C: 76.13 O: 23.87

Oxidized Activated Carbon C: 87.31 O:8.16

Physical Properties

Surface Content (EDS) Surface Area 848 1010 660 988 982 (m2/g) Pore Volume 0.46 0.58 0.37 0.65 0.65 (cm3/g) Pore Size (nm) 2.18 2.29 2.23 2.64 2.63 Surface pKa (±)* 10.54 (0.22) 8.25 (0.38) 3.26 (0.57) 7.90 (0.69) 6.74 (0.21) Total Acid Sites 0.19 0.62 2.0 0.30 0.55 (mmol/g) Total Base Sites 0.51 0.41 0 0.27 0.20 (mmol/g) *(±) values for pKa measurements are the standard deviation of triplicate experiments

Chemical Properties 281

Commercial Activated Carbon C: 88.48 O: 6.75

282



Page 14 of 31

283

Examination of the chemical properties shows much larger variation over the series, although the

284

activated carbon still shows less change than the coconut charcoal samples. There is an overall

285

decrease in the observed surface pKa upon exposure of both commercial sorbents to the

286

oxidative thermal, which is also reflected in the total acid/base sites from the Boehm titration

287

data. The total acid sites increase while the base sites decrease upon treatment, although the

288

effect is more dramatic in the coconut charcoal than the activated carbon.

289

290 291 292 293 294

Figure 2. SEM images of activated carbon sorbents tested in this study. (a = commercial coconut charcoal, b = oxidized coconut charcoal, c = acid coconut charcoal, d = commercial activated carbon, e = oxidized activated carbon)

295

Nitrosamine adsorption capacity and behavior from a simulated water wash. The maximum

296

nitrosamine retention capacity and the adsorption behavior of the carbon sorbents was

297

determined using a model nitrosamine (NPY) to construct adsorption isotherms in a simulated

298

CO2 capture waterwash solution containing a low concentration of amine, in these experiments

299

0.3 wt % MEA, based on published reports from pilot waterwash systems.44-45 A series of


Page 15 of 31


300

adsorption experiments were conducted where the initial NPY concentration was varied and the

301

NPY capacity (qe, in mg NPY/g sorbent) was determined. The isotherm data for each sorbent

302

was fitted to Langmuir and Freundlich adsorption models using equations (1) and (2)

303

respectively, where qe is the equilibrium adsorption capacity, qm is the maximum adsorption

304

capacity, kL/kF are the Langmuir and Freundlich constants, 1/n is an experimentally determined

305

unit less exponent, and Ce is the equilibrium nitrosamine concentration.46-47 The calculated

306

Langmuir and Freundlich constants, as well as the uncertainty associated with these fits are given

307

in the supporting information (Table S2). Based on the weighted standard error and goodness-of-

308

fit (Table S2) the carbon sorbents exhibited Langmuir adsorption behavior (Figure 3), and the

309

maximum NPY capacity (qm) for each carbon sorbent is given in Table 2. The commercial

310

coconut charcoal has the highest capacity at 191 mg NPY/g, with the oxidized coconut charcoal,

311

commercial activated carbon and oxidized commercial activated carbon all showing reduced

312

nitrosamine capacities between 113 – 133 mg NPY/g. The acid treated coconut charcoal shows

313

the lowest capacity at 18 mg/g. The maximum sorbent capacity (qm) is not necessarily the only

314

value of interest, as the kL, or affinity, is related to the slope of Langmuir curve at lower

315

concentrations. A sorbent with a higher kL would need a lower driving force at low

316

concentrations, reaching saturation faster at a lower concentration. Comparison of the affinity

317

(kL) values in Table S2 show that, and the commercial coconut charcoal has the smallest kL (and

318

the lowest slope) of the sorbents tested, with the exception of the acid coconut charcoal. This

319

suggests that different sorbents may be desirable under certain circumstances, and the sorbent

320

may be need to be tailored to the specific solvent, conditions or application.

321 322



323

324

/

Page 16 of 31

Langmuir isotherm

(1)

Freundlich isotherm

(2)

325

326 327

Figure 3. Adsorption behavior and maximum capacity of NPY (Langumir fit = solid line;

328

Freundlich fit = dotted line,) by surface-modified carbon sorbents from a simulated washwater

329

solution (0.3 wt.% MEA). ● = commercial coconut charcoal; ■ = oxidized coconut charcoal; ♦ =

330

commercial activated carbon; ▲= oxidized activated carbon; ● = acid coconut charcoal. R2

331

values for the Langumir and Freundlich fits are given in the supporting information Table S2.

332 333 334


Page 17 of 31


Table 2. Maximum NPY Capacity of Carbon Sorbents, as Calculated from Langmuir Isotherm Fits capacity, qm carbon type (mg NPY/g carbon) commercial coconut charcoal

191

oxidized coconut charcoal

133

acid coconut charcoal

18

commercial activated carbon

113

oxidized activated carbon

128

335 336

The adsorption of NPY from solution initially increases dramatically at higher NPY

337

concentrations, but levels off at a maximum, as shown in Figure 3.46 However, when the

338

adsorption capacity is converted to removal efficiency (% NPY removal, Figure 4), it is apparent

339

that better adsorption is obtained at lower concentrations. Although the data in Figure 4 is from

340

batch mode experiments with a fixed initial NPY concentration, this type of behavior will likely

341

be is advantageous for CO2 capture applications where nitrosamines, after forming in the

342

absorber, are captured and accumulate in the wash-water section at relatively low concentrations.

343

With constant treatment through a sorbent, efficient nitrosamine removal can keep

344

concentrations relatively low preventing re-emission into the environment in the scrubbed flue

345

gas from the waterwash based on their Henry’s volatility coefficient.39

346



Page 18 of 31

347 348

Figure 4. Effect of NPY concentration on removal efficiency from simulated washwater solution

349

(0.3 wt.% MEA). ● = commercial coconut charcoal; ■ = oxidized coconut charcoal; ♦ =

350

commercial activated carbon; ▲= oxidized activated carbon; ● = acid coconut charcoal.

351 352

In this study we did not find a correlation between the physical properties of the sorbent, such as

353

surface area, and NPY capacity (Figure 5a). Instead, Figure 5b shows a close linear relationship

354

(R2 > 0.99) between the surface pKa and NPY adsorption, where the more basic carbon surfaces

355

exhibit higher capacity for NPY. The relationship for total acid/base versus NPY capacity is less

356

linear, but there is still a clear trend (Figure 5c) showing base sites favor nitrosamine adsorption,

357

while acid sites decrease adsorption (Figure 5d).

358


Page 19 of 31


359

360 361

Figure 5. Relationship between sorbent surface properties and NPY capacity. (● = commercial

362

coconut charcoal; ■ = oxidized coconut charcoal; ♦ = commercial activated carbon; ▲=

363

oxidized commercial activated carbon; ● = acid coconut charcoal).

364 365

Amine adsorption & nitrosamine selectivity. When applied to a commercial CCS process, it

366

will be critical that the sorbent selectively remove nitrosamines from the circulating waterwash

367

while leaving the amine to be returned to the solvent loop during blowdown. This will serve to;

368

(1) extend the lifetime of the carbon bed, as amine concentrations in the water wash will be



Page 20 of 31

369

higher than that of nitrosamines; and (2) allow recovery of amine emissions and lower total

370

amine losses and reduce operational costs.

371 372

The affinity of each sorbent for amines was examined by circulating the simulated washwater

373

solution containing 0.3 wt% MEA, with no nitrosamines, through the same sorbent bed

374

apparatus. The adsorption of the MEA by each sorbent was measured by difference. The affinity

375

of the carbon sorbents for MEA varies widely (Figure 6), with the coconut charcoal showing the

376

lowest adsorption, and the acid treated coconut charcoal having the highest adsorption of MEA.

377

There is a general trend between surface pKa and amine adsorption (see supporting information

378

Figure S4). In this case, the acid treated sorbent (with the lowest surface pKa) showed the

379

highest absorbance of MEA, in contrast to nitrosamine adsorption.

380 381

Figure 6. Adsorption of MEA (mg MEA/g carbon) by commercial and modified sorbents from a

382

simulated washwater solution containing 0.3 wt.% MEA. Error bars are the percent standard

383

deviation from the average peak area of triplicate injections.


Page 21 of 31


384 385

While the coconut charcoal has the lowest adsorption of amine, and the highest adsorption of

386

nitrosamines, the total impact of the amines presence in the simulated waterwash solution with

387

regards to nitrosamine adsorption is not yet fully investigated. To this end, the effect of amine

388

(MEA and PZ) in the waterwash solution on the selectivity of nitrosamine adsorption was

389

determined using N-nitrosopyrrolidine (NPY) and N-nitrosopiperazine (NPZ) as representative

390

nitrosamines. The percent nitrosamine removal from both the commercial coconut charcoal and

391

oxidized coconut carbon sorbents was determined from pure water (no added MEA or PZ), and

392

then from simulated washwater solution (0.3 wt.% MEA, 1 wt.% PZ48) based on reported

393

waterwash amine concentrations.

394 395

The results in Figure 7 shows that the addition of MEA has no effect on NPY adsorption,

396

indicating that although there is the possibility for MEA adsorption by the carbon sorbent, the

397

selectivity of the coconut charcoal and oxidized coconut sorbent for nitrosamines over amines is

398

likely sufficient to maintain nitrosamine adsorption capacity under these conditions. However,

399

there is a decrease in the removal efficiency of NPZ upon the addition of 1 wt.% PZ to the

400

matrix, indicating lower selectivity for NPZ over PZ. The higher concentration of PZ in the

401

simulated waterwash may be a factor in the lower selectivity, as control experiments did not

402

show any nitrosamine production catalyzed by the carbon surface (see supporting

403

information).49-50 Additionally, the similar structures of PZ and NPZ, varying by only the nitroso

404

group, may lower the ability of the sorbent to “discriminate” between the two compounds and

405

decrease selectivity if adsorption is based on the structure/polarity of the components in solution.

406

This then raises the question of how the sorbent system would perform at removing other



Page 22 of 31

407

process-relevant nitrosamines that result from the nitrosation of secondary-amine degradation

408

products from a primary amine solvent such as MEA.

409

410 411

Figure 7. Removal of NPY and NPZ nitrosamines (%), with and without amine present in

412

simulated wash-water solutions (MEA with NPY; PZ with NPZ). Error bars are the percent

413

standard deviation from the average peak area of triplicate injections.

414 415

Degradation-relevant nitrosamine adsorption. The use of NPY as a representative nitrosamine

416

is advantageous for initial studies due to its commercial availability and low cost, however

417

testing the adsorption of process-relevant nitrosamines, those that are formed and have been

418

detected in CCS systems, is also prudent. NDEA and NDELA have been reported as potential

419

contaminants from the degradation and nitrosation of amine degradation products.22,

420

these two nitrosamines have a similar base structure, there is a dramatic difference in polarity

421

due to the alcohol groups on NDELA.


51

While

Page 23 of 31


422 423

The difference in activity of the commercial coconut charcoal towards the removal of these two

424

different nitrosamines was evaluated at a single concentration and compared to the calculated

425

NPY adsorption from the Langumir curve with commercial coconut charcoal (vide supra).

426

Figure 8 shows the adsorption of NDEA, NDELA, and NPZ relative to NPY at the same

427

concentration. NDEA, with a linear alkyl chain, has 50% higher adsorption than the slightly

428

more polar, cyclic NPY. The more polar NDELA, with two alcohol groups, showed a 30%

429

decrease in adsorption from the same solution with the same carbon sorbent. This indicates that

430

surface pKa may not be the only contributing factor to nitrosamine adsorption by these sorbents,

431

and in this case the polarity of the nitrosamine may also play a role in the observed adsorption

432

differences. Again, NPZ adsorption may be reduced due to the higher amine concentration used

433

in the simulated washwater. The relative hydrophobicity/hydrophilicity of the carbon surface

434

also appears to influence the affinity of the nitrosamine for the carbon surface. This suggests that

435

in order to optimize adsorption, the hydrophobicity/hydrophilicity (polarity) of the sorbent

436

surface may need to be matched to the nitrosamine(s) expected to form in the solvent either

437

directly, or from amine degradation products.

438



Page 24 of 31

439 440

Figure 8. Relative capacity of commercial coconut charcoal for NPY, NDEA, and NDELA,

441

from simulated MEA wash water, and NPZ from simulated PZ wash water, normalized to

442

adsorption of NPY. Error bars are the percent standard deviation from the average peak area of

443

triplicate injections.

444 445

Thermal regeneration of carbon sorbent. In order to extend the lifetime of the carbon sorbent

446

and further decrease the potential long-term operating cost of the CCS system, the possibility of

447

thermally regenerating the carbon sorbent was investigated. Typical regeneration of activated

448

carbon is accomplished at elevated temperatures (700 – 1000 °C) under inert atmosphere to

449

prevent surface oxidation.42 The thermal decomposition of some nitrosamines, including NPZ

450

and NDELA, has been reported at temperatures as low as 100 – 150 °C in industrially-relevant

451

amine solutions.35 In addition, Fine and coworkers showed that the rate of thermal nitrosamine

452

decomposition is strongly dependent on the pKa of bases that are present in solution, such as

453

parent amines, where a more basic amine solvent increases the nitrosamine decomposition rate.35


Page 25 of 31


454

Information relating to the decomposition of other nitrosamines is not readily available in the

455

open literature, but other nitrosamines are expected to have similar decomposition temperatures

456

under similar conditions. Given this information, the possibility exists of regenerating the carbon

457

sorbent at relatively low temperatures, which in turn would save on the cost of the regeneration

458

and preclude the need for an inert atmosphere.21,

459

sorbent to favor nitrosamine adsorption would also aid in nitrosamine destruction during a

460

thermal regeneration cycle.

35

In addition, the selection of a more basic

461 462

To further demonstrate this concept, a sample of coconut charcoal that had been exposed to a

463

1000 ppm solution of NPY in MEA washwater was thermally regenerated. Removal of NPY

464

from a low concentration NPY solution (15 ppm) was un-affected when compared to the initial

465

removal (Figure 9), however there is a small decrease in removal efficiency (less than a 25%)

466

when the sorbent was re-exposed to the high concentration solution (1000 ppm). This is

467

consistent with previous results showing that better removal efficiency is achieved at lower

468

nitrosamine concentrations. Although further work is needed to optimize the regeneration

469

process itself, this initial result is promising in demonstrating that the carbon can potentially be

470

regenerated and recycled under relatively mild conditions and can be used to maintain lower

471

nitrosamine concentrations in the circulating waterwash solution.



Page 26 of 31

472 473

Figure 9. Adsorption of NPY at two different concentrations from a simulated waterwash

474

solution (containing 0.3 wt.% MEA) by commercial coconut charcoal carbon, before (blue) and

475

after (red) thermal regeneration for 20 hours at 200 °C. Error bars are the percent standard

476

deviation from the average peak area of triplicate injections.

477 478

Implications. Activated carbons can be used as a solid sorbent for the selective removal of

479

nitrosamine contaminants from simulated amine-based CCS washwater conditions. Activated

480

carbon is inexpensive, widely available, and familiar to the power industry as mercury removal

481

sorbent. Furthermore, the application of a carbon bed for circulation and treatment of liquid is a

482

well-known technology, and is currently used in CCS applications to removal degradation

483

products for controlling forming in the absorber. There is a strong correlation between surface

484

pKa and nitrosamine removal, where the more basic commercial coconut charcoal exhibited the

485

highest nitrosamine capacity and the most acidic surface showed almost no activity, giving a

486

direction for the development of further sorbent modifications to further increase adsorption

487

capacity. Testing of different, industrially-relevant, nitrosamines under the same conditions


Page 27 of 31


488

showed that more hydrophobic nitrosamines have greater affinity for commercial coconut

489

charcoal, indicating that matching the hydrophobicity/hydrophilicity of the carbon sorbent and

490

expected nitrosamines may be a key feature of these systems moving forward. For applications

491

with secondary amines, such as PZ/NPZ, it may be advantageous to develop a carbon sorbent

492

functionalized with a more basic surface to increase adsorption. Regeneration of the carbon

493

sorbent under mild conditions may also be possible for further cost savings. Further work is

494

underway to quantify the hydrophobicity of the carbon sorbents, develop more effective surface

495

functionalization, and characterize/optimize the thermal regeneration process.

496 497

Supporting Information

498

The supporting information is available free of charge on the ACS publications website.

499 500

Acknowledgements

501

The authors acknowledge the Carbon Management Research Group (CMRG) members including

502

Louisville Gas & Electric (LG&E) and Kentucky Utilities (KU), Duke Energy and the Electric

503

Power Research Institute (EPRI) for their financial support. We also acknowledge Dr. Xin Gao

504

for assistance with BET characterization of the carbon sorbents.

505 506

References

507 508 509 510 511 512 513 514 515

1. Badr, S.; Frutiger, J.; Hungerbuehler, K.; Papadokonstantakis, S., A framework for the environmental, health and safety hazard assessment for amine-based post combustion CO2 capture. Int. J. Greenhouse Gas Control 2017, 56, 202-220; 10.1016/j.ijggc.2016.11.013. 2. Reynolds, A. J.; Verheyen, T. V.; Adeloju, S. B.; Meuleman, E.; Feron, P., Towards commercial scale postcombustion capture of CO2 with monoethanolamine solvent: key considerations for solvent management and environmental impacts. Environ. Sci. Technol. 2012, 46 (7), 3643-54; 10.1021/es204051s. 3. Magee, P. N.; Barnes, J. M., The production of malignant primary hepatic tumours in the rat by feeding dimethylnitrosamine. Br. J. Cancer 1956, 10 (1), 114-22; 10.1038/bjc.1956.15.



516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562

4. Dai, N.; Mitch, W. A., Controlling Nitrosamines, Nitramines, and Amines in Amine-Based CO2 Capture Systems with Continuous Ultraviolet and Ozone Treatment of Washwater. Environ. Sci. Technol. 2015, 49 (14), 8878-8886; 10.1021/acs.est.5b01365. 5. Dai, N.; Shah, A. D.; Hu, L.; Plewa, M. J.; McKague, B.; Mitch, W. A., Measurement of nitrosamine and nitramine formation from NOx reactions with amines during amine-based carbon dioxide capture for postcombustion carbon sequestration. Environ. Sci. Technol. 2012, 46 (17), 9793-801; 10.1021/es301867b. 6. da Silva, E. F.; Hoff, K. A.; Booth, A., Emissions from CO2 capture plants; an overview. Energy Procedia 2013, 37, 784-790; 10.1016/j.egypro.2013.05.168. 7. Goldman, M. J.; Fine, N. A.; Rochelle, G. T., Kinetics of N-nitrosopiperazine formation from nitrite and piperazine in CO2 capture. Environ. Sci. Technol. 2013, 47 (7), 3528-34; 10.1021/es304640f. 8. Dai, N.; Mitch, W. A., Effects of flue gas compositions on nitrosamine and nitramine formation in postcombustion CO2 capture systems. Environ. Sci. Technol. 2014, 48 (13), 7519-26; 10.1021/es501864a. 9. de Koeijer, G.; Talstad, V. R.; Nepstad, S.; Tønnessen, D.; Falk-Pedersen, O.; Maree, Y.; Nielsen, C., Health risk analysis for emissions to air from CO2 Technology Centre Mongstad. Int. J. Greenhouse Gas Control 2013, 18, 200-207; 10.1016/j.ijggc.2013.07.010. 10. Yu, K.; Reichard, M. C.; Dai, N., Nitrosamine Formation in the Desorber of Tertiary AlkanolamineBased Carbon Dioxide Capture Systems. Ind. Eng. Chem. Res. 2016, 55 (9), 2604-2614; 10.1021/acs.iecr.5b04858. 11. Straif, K.; Weiland, S. K.; Bungers, M.; Holthenrich, D.; Taeger, D.; Yi, S.; Keil, U., Exposure to high concentrations of nitrosamines and cancer mortality among a cohort of rubber workers. Occup. Environ. Med. 2000, 57 (3), 180-7; 12. Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs – N-nitrosodimethylamine, CAS #62-75-9; U.S. Department of Health and Human Services, July 1999; http://www.atsdr.cdc.gov/toxfaq.html.; 13. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Some NNitroso Compounds; Volume 17; World Health Organization, International Agency for Research on Cancer: Lyon, France, May 1978; http://pubs.acs.org/paragonplus/submission/esthag/est-citationsample.pdf. 14. Izquierdo-Pulido, M.; Barbour, J. F.; Scanlan, R. A., N-nitrosodimethylamine in Spanish beers. Food Chem. Toxicol. 1996, 34 (3), 297-9; 10.1016/0278-6915(95)00116-6. 15. Levallois, P.; Ayotte, P.; Van Maanen, J. M.; Desrosiers, T.; Gingras, S.; Dallinga, J. W.; Vermeer, I. T.; Zee, J.; Poirier, G., Excretion of volatile nitrosamines in a rural population in relation to food and drinking water consumption. Food Chem. Toxicol. 2000, 38 (11), 1013-9; 10.1016/S0278-6915(00)000892. 16. Altkofer, W.; Braune, S.; Ellendt, K.; Kettl-Gromminger, M.; Steiner, G., Migration of nitrosamines from rubber products - are balloons and condoms harmful to the human health? Mol. Nutr. Food Res. 2005, 49 (3), 235-8; 10.1002/mnfr.200400050. 17. Chon, K.; Kim, S. H.; Cho, J., Removal of N-nitrosamines in a membrane bioreactor and nanofiltration hybrid system for municipal wastewater reclamation: Process efficiency and mechanisms. Bioresource Technology 2015, 190, 499-507; 10.1016/j.biortech.2015.02.080. 18. Public Health Goals for Chemicals in Drinking Water: N-nitrosodimethylamine; Pesticide and Environmental Toxicology Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency (Cal/EPA); December 2006; https://oehha.ca.gov/media/downloads/water/chemicals/phg/122206ndmaphg_0.pdf. 19. Current regulatory limit: n-Nitrosodimethylamine; Office of Energy and Environmental Affairs, Massachusetts Department of Environmental Protection; May 2004;


Page 28 of 31

Page 29 of 31

563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610


http://www.mass.gov/eea/agencies/massdep/water/drinking/standards/n-nitrosodimethylaminendma.html. 20. Strazisar, B. R.; Anderson, R. R.; White, C. M., Degradation Pathways for Monoethanolamine in a CO2 Capture Facility. Energy Fuels 2003, 17 (4), 1034-1039; 10.1021/ef020272i. 21. Voice, A. K.; Hill, A.; Fine, N. A.; Rochelle, G. T., Nitrosamine formation and mitigation in blended amines for CO2 capture. Int. J. Greenhouse Gas Control 2015, 39, 329-334; 10.1016/j.ijggc.2015.05.030. 22. Review of Amine Emissions from Carbon Capture Systems; Version 2.01; Scottish Environment Protection Agency, 2015; https://www.sepa.org.uk/media/155585/review-of-amine-emissions-fromcarbon-capture-systems.pdf. 23. Karl, M.; Wright, R. F.; Berglen, T. F.; Denby, B., Worst case scenario study to assess the environmental impact of amine emissions from a CO2 capture plant. Int. J. Greenhouse Gas Control 2011, 5 (3), 439-447; 10.1016/j.ijggc.2010.11.001. 24. Permit for activities pursuant to the Pollution Control Act. CO2 Technology Centre Mongstad DA; Norwegian Climate and Pollution Agency; November 2011; Org. Number 994257295. 25. Chandan, P. A.; Remias, J. E.; Liu, K., Possible ways to minimize nitrosation reactions during postcombustion CO2 capture process. Int. J. Greenhouse Gas Control 2014, 31, 61-66; 10.1016/j.ijggc.2014.09.028. 26. Sørensen, L.; Zahlsen, K.; Hyldbakk, A.; da Silva, E. F.; Booth, A. M., Photodegradation in natural waters of nitrosamines and nitramines derived from CO2 capture plant operation. Int. J. Greenhouse Gas Control 2015, 32, 106-114; 10.1016/j.ijggc.2014.11.004. 27. Afzal, A.; Kang, J.; Choi, B.-M.; Lim, H.-J., Degradation and fate of N-nitrosamines in water by UV photolysis. Int. J. Greenhouse Gas Control 2016, 52, 44-51; 10.1016/j.ijggc.2016.06.009. 28. Knuutila, H.; Svendsen, H. F.; Asif, N., Decomposition of nitrosamines in aqueous monoethanolamine (MEA) and diethanolamine (DEA) solutions with UV-radiation. Int. J. Greenhouse Gas Control 2014, 31, 182-191; 10.1016/j.ijggc.2014.10.002. 29. Fujioka, T.; Khan, S. J.; Mc Donald, J. A.; Nghiem, L. D., Ozonation of N-Nitrosamines in the Reverse Osmosis Concentrate from Water Recycling Applications. Ozone: Science & Engineering 2014, 36 (2), 174-180; 10.1080/01919512.2013.866885. 30. Chuang, Y.-H.; Mitch, W. A., Effect of Ozonation and Biological Activated Carbon Treatment of Wastewater Effluents on Formation of N-nitrosamines and Halogenated Disinfection Byproducts. Environ. Sci. Technol. 2017, 51 (4), 2329-2338; 10.1021/acs.est.6b04693. 31. Gerrity, D.; Pisarenko, A. N.; Marti, E.; Trenholm, R. A.; Gerringer, F.; Reungoat, J.; Dickenson, E., Nitrosamines in pilot-scale and full-scale wastewater treatment plants with ozonation. Water Research 2015, 72, 251-261; 10.1016/j.watres.2014.06.025. 32. Chandan, P.; Honchul, S.; Thompson, J.; Liu, K., Catalyst design for mitigating nitrosamines in CO2 capture process. Int. J. Greenhouse Gas Control 2015, 39, 158-165; 10.1016/j.ijggc.2015.05.013. 33. Chandan, P.; Harrison, E.; Honchul, S.; Li, J.; Thompson, J.; Liu, K., Destroying nitrosamines in post-combustion CO2 capture. Energy Procedia 2014, 63, 808-813; 10.1016/j.egypro.2014.11.091. 34. Li, Y. Y.; Wan, M. M.; Zhu, J. H., Cleaning carcinogenic nitrosamines with zeolites. Environmental Chemistry Letters 2014, 12 (1), 139-152; 10.1007/s10311-013-0451-1. 35. Fine, N. A.; Nielsen, P. T.; Rochelle, G. T., Decomposition of nitrosamines in CO2 capture by aqueous piperazine or monoethanolamine. Environ. Sci. Technol. 2014, 48 (10), 5996-6002; 10.1021/es404949v. 36. Nielsen, P. T.; Li, L.; Rochelle, G. T., Piperazine Degradation in Pilot Plants. Energy Procedia 2013, 37, 1912-1923; 10.1016/j.egypro.2013.06.072. 37. Sun, X. D.; Lin, W. G.; Wang, L.-j.; Zhou, B.; Lv, X. L.; Wang, Y.; Zheng, S.-j.; Wang, W.-m.; Tong, Y.-G.; Zhu, J. H., Liquid adsorption of tobacco specific N-nitrosamines by zeolite and activated carbon. Microporous and Mesoporous Materials 2014, 200, 260-268; 10.1016/j.micromeso.2014.08.057.



611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650

38. Council, N. R., Disposal of Activated Carbon from Chemical Agent Disposal Facilities. The National Academies Press: Washington, DC, 2009; p 86. 39. Thompson, J. M., N.; Liu, K. Solubility and thermodynamic modeling of carcinogenic nitrosamines in aqueous amine solvents for CO2 capture. Presented at the 13th International Conference on Greenhouse Gas Control Technologies (GHGT-13), 14-18 November 2016, Lausanne, Switzerland. 40. Thitakamol, B.; Veawab, A.; Aroonwilas, A., Environmental impacts of absorption-based CO2 capture unit for post-combustion treatment of flue gas from coal-fired power plant. Int. J. Greenhouse Gas Control 2007, 1 (3), 318-342; 10.1016/S1750-5836(07)00042-4. 41. Veltman, K.; Singh, B.; Hertwich, E. G., Human and environmental impact assessment of postcombustion CO2 capture focusing on emissions from amine-based scrubbing solvents to air. Environ. Sci. Technol. 2010, 44 (4), 1496-502; 10.1021/es902116r. 42. Sheintuch, M.; Matatov-Meytal, Y. I., Comparison of catalytic processes with other regeneration methods of activated carbon. Catalysis Today 1999, 53 (1), 73-80; 10.1016/S0920-5861(99)00104-2. 43. Noh, J. S.; Schwarz, J. A., Effect of HNO3 treatment on the surface acidity of activated carbons. Carbon 1990, 28 (5), 675-682; 10.1016/0008-6223(90)90069-B. 44. Carter, T., National Carbon Capture Center: Post-Combustion. Presented at the NETL CO2 Capture Technology Meeting, 9-12 July 2012, Pittsburgh, PA, USA. 45. Morken, A. K.; Nenseter, B.; Pedersen, S.; Chhaganlal, M.; Feste, J. K.; Tyborgnes, R. B.; Ullestad, Ø.; Ulvatn, H.; Zhu, L.; Mikoviny, T.; Wisthaler, A.; Cents, T.; Bade, O. M.; Knudsen, J.; de Koeijer, G.; FalkPedersen, O.; Hamborg, E. S., Emission Results of Amine Plant Operations from MEA Testing at the CO2 Technology Centre Mongstad. Energy Procedia 2014, 63, 6023-6038; 10.1016/j.egypro.2014.11.636. 46. Li, H.; Zou, L.; Pan, L.; Sun, Z., Novel Graphene-Like Electrodes for Capacitive Deionization. Environ. Sci. Technol. 2010, 44 (22), 8692-8697; 10.1021/es101888j. 47. Li, H.; Pan, L.; Lu, T.; Zhan, Y.; Nie, C.; Sun, Z., A comparative study on electrosorptive behavior of carbon nanotubes and graphene for capacitive deionization. Journal of Electroanalytical Chemistry 2011, 653 (1–2), 40-44; 10.1016/j.jelechem.2011.01.012. 48. Cousins, A.; Nielsen, P. T.; Huang, S.; Rowland, R.; Edwards, B.; Cottrell, A.; Chen, E.; Rochelle, G. T.; Feron, P. H. M., Pilot-scale evaluation of concentrated piperazine for CO2 capture at an Australian coal-fired power station: Nitrosamine measurements. Int. J. Greenhouse Gas Control 2015, 37, 256-263; 10.1016/j.ijggc.2015.03.007. 49. Padhye, L. P.; Hertzberg, B.; Yushin, G.; Huang, C. H., N-nitrosamines formation from secondary amines by nitrogen fixation on the surface of activated carbon. Environ. Sci. Technol. 2011, 45 (19), 8368-76; 10.1021/es201696e. 50. Padhye, L.; Wang, P.; Karanfil, T.; Huang, C. H., Unexpected role of activated carbon in promoting transformation of secondary amines to N-nitrosamines. Environ. Sci. Technol. 2010, 44 (11), 4161-8; 10.1021/es903916t. 51. 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 amine-based carbon capture. Environ. Sci. Technol. 2013, 47 (6), 2799-808; 10.1021/es304893m.

651 652


Page 30 of 31

Page 31 of 31

653


For Table of Contents Only

654

655


Selective Removal of Nitrosamines from a Model ... - ACS Publications

Recommend Documents