Macroporous Carbon Supported Zerovalent Iron for Remediation of

Subscriber access provided by Olson Library | Northern Michigan University

Article

Macroporous carbon supported zerovalent iron for remediation of trichloroethylene Michael Lawrinenko, Zhuangji Wang, Robert Horton, Deyny Mendivelso-Perez, Emily A Smith, Terry E. Webster, David A Laird, and J. (Hans) van Leeuwen ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b02375 • Publication Date (Web): 26 Dec 2016 Downloaded from http://pubs.acs.org on December 29, 2016

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.

ACS Sustainable Chemistry & Engineering 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 26

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

ACS Sustainable Chemistry & Engineering

1

Macroporous carbon supported zerovalent iron for remediation of trichloroethylene

2

Michael Lawrinenko,a Zhuangji Wang,a Robert Horton,a Deyny Mendivelso-Perez,b Emily A.

3

Smith,b Terry E. Webster,c David A. Lairda, and J. (Hans) van Leeuwend*

4 5

a

Department of Agronomy, Iowa State University, 2505 Agronomy, 716 Farm House Ln Ames, IA 50011-1051

6 7

b

8

c

9 10 11

d

The Ames Laboratory, U.S. Department of Energy, and Department of Chemistry, Iowa State University, 0706 Gilman Hall, 2415 Osborn Dr, Ames, IA 50011-1021 Des Moines Water Works, 2201 George Flagg Pkwy, Des Moines, IA 50321

Departments: Civil, Construction & Environmental Engineering; Ag & Biosystems Engineering; Food Science & Human Nutrition, Iowa State University, 476 Town Engng, 813 Bissell Rd, Ames, IA 50011-1066

12 13

*

14

Abstract

15

Groundwater contamination with chlorinated hydrocarbons has become a widespread

16

problem that threatens water quality and human health.

17

(PRBs) which employ zerovalent iron are effective for remediation, however a need exists

18

to reduce the economic and environmental costs associated with constructing PRBs. We

19

present a method to produce zerovalent iron supported on macroporous carbon using only

20

lignin and magnetite. Biochar-ZVI (BC-ZVI) produced by this method exhibits a broad

21

pore size distribution with micrometer sized ZVI phases dispersed throughout a carbon

22

matrix. X-ray diffraction revealed that pyrolysis at 900°C of a 50/50 lignin-magnetite

23

mixture resulted in almost complete reduction of magnetite to ZVI and that compression

24

molding promotes iron reduction in pyrolysis due to mixing of starting materials. High

25

temperature pyrolysis of lignin yields some graphite in BC-ZVI due to reduction of

26

carbonaceous gases on iron oxides. TCE was removed from water as it passed through a

27

column packed with BC-ZVI at flow rates representative of average and high

corresponding author: [email protected]

ACS Paragon Plus Environment

Permeable reactive barriers


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

28

groundwater flow.

One-dimensional convection-dispersion modeling revealed that

29

adsorption by biochar influences TCE transport and that BC-ZVI facilitated removal of

30

TCE from contaminated water by both adsorption and degradation.

31 32

Key words:trichloroethylene, biochar, zerovalent iron, macroporous carbon, permeable reactive barrier

33 34

1. Introduction

35

Permeable reactive barriers (PRBs) have been widely used to remediate groundwater

36

contaminated with chlorinated hydrocarbons.1,2 Zerovalent iron (ZVI) is most commonly

37

employed in PRBs as an electron source to reductively dechlorinate the parent molecule

38

to residual hydrocarbon and chloride. While effective, PRBs are costly because of

39

expensive raw materials.

40

concentrations limit the kinetics of remediation, particularly affecting performance during

41

high groundwater velocities. Expected service lives of PRBs was originally estimated at

42

around 25 years, however a recent lifecycle analysis reported that most PRBs only

43

operate for about 10 years. This is due to declining reactivity of the permeable barrier

44

material and declining hydraulic conductivity due to illuvial deposition of soil materials.1

45

These challenges call for a need to improve reactive barrier material to increase reliability

46

and service life. Improved PRB material and construction methods would have positive

47

impacts on the economics and performance of this technology. Further, alternate PRB

48

media with lower global warming impact would more comprehensively benefit the

49

environment than material produced by conventional means.3 Ideally, new technologies

50

designed to produce PRB media with improved reliability and performance characteristics

Poor adsorption affinity and low contaminant solution


Page 2 of 26

Page 3 of 26

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


51

should also employ production practices that consume less energy and emit less

52

greenhouse gases than current manufacturing processes.

53

Various approaches to improving reaction kinetics of PRB media have recently been

54

reported: co-mixing activated carbon (AC) with ZVI,4 catalyst enhanced ZVI such as

55

palladized ZVI,5-7 and development of biochar-ZVI (BC-ZVI),8-10 and AC-ZVI

56

composites.11 Both BC-ZVI and AC-ZVI composites demonstrate increased degradation

57

kinetics of TCE over ZVI, due to adsorption of the contaminant on the C phase. Despite

58

promising performance reports, the high costs of activated carbon, binding agents, and

59

rare-earth metals render options that employ these

60

Furthermore, leaching of certain catalyst metals poses other environmental risks; adding

61

to the incumbent problem of the contaminant. All of these approaches lead to materials

62

designed to be mixed with sand, as PRBs have been traditionally constructed, offering no

63

solution to prevent pore clogging and decreasing hydraulic conductivity caused by soil

64

illuviation. Production of reactive media reported in most of these studies employed

65

borohydride reduction which is also costly,12 energy-intensive, and offers no way to

66

reduce the climate impact of ZVI production.13

67

materials cost-prohibitive.

Pyrolysis of biomass pretreated with iron salts has been demonstrated to produce ZVI.8,10,14

68

In pyrolysis, organic materials are heated under low-oxygen conditions, thermally transforming

69

the organic material into charcoal, also known as biochar, while oxidized iron is simultaneously

70

reduced to ZVI and other crystalline forms of iron. Biochar production can be C neutral as the

71

amount of atmospheric C sequestered in soil may equate to C released from fossil fuel utilized

72

for harvesting and processing of biomass.15,16 The carbon sequestered in soil with biochar

73

application and replacement of fossil fuel with biorenewable C to produce ZVI both reduce



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

74

carbon dioxide released to the atmosphere, thus lowering the climate impact associated with the

75

manufacture of PRB material.3 Previous work revealed that pyrolysis at 700 °C and 900 °C of

76

various biomass feedstocks pretreated with FeCl3 yielded biochars containing significant

77

amounts of reduced Fe as magnetite and ZVI, respectively; however feedstock chemistry and

78

pyrolysis temperature influenced the reduction of iron.14 Pyrolysis based production of ZVI is

79

potentially beneficial to the environment and more cost-effective than current production

80

methods as biorenewable organic materials and low-cost iron oxides can be used for feedstocks.

81

Permeable reactive barriers require hydraulic conductivities greater than that of surrounding

82

soil in order to perform. Pyrolysis-based ZVI previously reported8,10,14 were small particulates

83

which would be subject to eluviation and displacement in a PRB. One way to possibly overcome

84

this challenge is to produce large particle BC-ZVI for use as media in PRBs. This innovation

85

would eliminate the need for sand matrices in PRB construction. Biochars produced from most

86

biomass feedstocks resemble precursor materials by size and shape characteristics. Even the

87

anatomical structure of plant materials is preserved.17 Frangibility and low crushing strength of

88

charcoals and biochar contribute to rapid physical deterioration in production and handling, thus

89

even sizing of feedstock could only produce an ideal biochar size fraction of limited yield. For

90

this reason, granular activated carbons cost several times more than powders. Producing large

91

particle size biochar is thus challenging and processes that utilize whole plant materials could at

92

best be optimized with low yield to produce large particle BC-ZVI.

93

We sought to address the need for low-cost but effective PRB media with a minor climate

94

impact, by producing biochars from mixtures of lignin and magnetite. Lignin is an abundant and

95

low-cost plant biopolymer that is available as a byproduct from paper pulp processing, sugarcane

96

processing, and second generation ethanol production; lignin is biorenewable, and is often


Page 4 of 26

Page 5 of 26

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


97

burned for process heat or landfilled. We previously employed ferric chloride to produce BC-

98

ZVI, however we found that significant chlorine is volatilized in high temperature pyrolysis,

99

potentially creating hazardous gas in pyrolysis effluent.14 Magnetite (Fe3O4) is abundantly

100

available as an iron ore, can be obtained at low-cost in bulk quantities in a powdered form, and

101

reduces problematic discharge of noxious gases in pyrolysis effluent. We hypothesized that

102

pyrolysis of mixtures of lignin and powdered magnetite would yield BC-ZVI materials that

103

possess appropriate physical and chemical properties for PRB use.

104

2. Materials and Methods

105

2.1 Biochar Preparation

106

The conditions used in biochar preparation were learned in our earlier research;14

107

specifically, pyrolysis temperature, heating time, and selection of a low-ash biomass

108

feedstock. Biochars were prepared by slow pyrolysis of lignin (control biochar) or lignin-

109

magnetite mixtures in a stainless steel box contained in a muffle furnace and heated from

110

ambient temperature to 900 °C over 4 h. During pyrolysis and throughout cool-down,

111

samples were purged under 200 mL min-1 N2 gas. Lignin was supplied by Archer Daniels

112

Midland Corporation. This lignin was a co-product of their Acetosolv process, a

113

modified organosolv process, which is used to extract cellulose from corn stover for fuel-

114

ethanol production. Magnetite was ore grade powder obtained from the Division of

115

Lands & Minerals, Minnesota Department of Natural Resources and was dried in a

116

convection oven prior to use. Lignin was ground in a mortar and pestle. Lignin and

117

magnetite mixtures of 50/50 or 30/70 gravimetric ratios were mixed in a beaker and

118

immediately pyrolyzed (unpressed sample). Pressed samples were prepared by

119

compression molding of lignin-magnetite mixtures in a 4-inch ID cylindrical aluminium



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

120

compression mold preheated to 180 °C under 20 tonne pressure (about 239 MPa), after

121

which the resulting pellet was pyrolyzed (pressed samples). As pyrolysis yielded large

122

intact solid loaves, resulting biochars were diced on a cutting board and screened between

123

#4 and #12 screens (1.68 to 4.76 mm). This granule fraction was utilized for all analyses.

124

Samples were stored in plastic bags after production.

125

2.2 X-ray Diffraction (XRD) Analysis

126

Diffraction patterns of biochar samples were collected from 10 to 90° 2θ with a Siemens

127

D5000 x-ray diffractometer using Cu Kα radiation generated at 40 kV and 30 mA in step

128

scan mode with a step size of 0.05° 2θ and a dwell time of 7 s per step. Fixed 1.0°

129

divergence and 3.0° anti-scattering slits were used with a scintillation counter. Random

130

powder mounts of biochars ground in an agate mortar were analyzed at ambient

131

temperature and humidity. The XRD patterns were analyzed using JADE v9.0.

132

2.3 Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDS) Analysis

133

Microscopy was performed with an FEI QUANTA FEG 250 scanning electron microscope using

134

a 10 kV beam of about 1nA. Images were collected using secondary electrons. Elemental maps

135

were obtained by energy dispersive x-ray analysis using an Oxford Aztec EDS. Granular

136

samples were mounted to the top of a 12.5 mm carbon stub using double-sided graphite tape by

137

compressing the taped stub against a subsample of biochar. For elemental analysis, 1 g samples

138

of biochar were ground in an agate mortar, transferred to a sample cup, and dosed with several

139

drops of hexane which was used to extract adhesive from tape. The adhesive was necessary to

140

hold biochar particles in place to avoid microscope contamination. With volatilization of

141

hexane, the small amount of C added to the samples by the adhesive likely did not alter the bulk

142

sample composition. Elemental analysis was performed by averaging triplicate EDS spot


Page 6 of 26

Page 7 of 26

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


143

analyses. Thermal combustion analysis using an Elementar Vario Micro Cube was also

144

performed to more accurately determine C, H, N, and S contents.

145

2.4 Raman Spectroscopy

146

Raman measurements were performed at ambient temperature using an XploRa Plus confocal

147

Raman microscope (Horiba Scientific/JY, France) equipped with a 532-nm laser excitation

148

source, operated at 25mW. An objective with a 0.9 numerical aperture (Olympus, Melville, NY)

149

was used to collect the Raman signal. Biochars were ground in a ball mill for 2 minutes to a fine

150

powder. Graphite standards (UCAR SP-1, Graphite Standard I, Lot# B74, Union Carbide;

151

Sigma-Aldrich synthetic graphite, Graphite Standard II, Lot# 08017EH) were analyzed as

152

received. Approximately 20 mg of sample was pressed onto a glass slide forming a dense layer

153

about 1mm thick, and placed on the microscope sample holder for analysis. This was repeated 6

154

times for each sample. Reported spectra were averaged from 6 subsamples acquired in triplicate,

155

for a total of 18 spectra, with a 10s acquisition time for each spectrum.

156

2.5 Miscible-Displacement Experiment

157

Breakthrough curves of aqueous TCE were measured using stainless steel 22 mm ID x 100 mm

158

columns (Alltech) packed with biochar granules using a modified influent pulse method

159

described by Casey et al. (2000).18 The pressed 50/50 BC-ZVI and the biochar control materials

160

were used for this study. Because BC-ZVI was three months old when breakthrough curve

161

measurements were performed, ZVI was assessed prior to analysis using XRD in which the

162

{110} reflection of ZVI was measured and intensities of 3 months old to fresh were compared.

163

Two flow rates were employed, representative of high (12.2 mm min-1) and average (5.6 mm

164

min-1) groundwater pore water velocities.18 These flow rates are reported as “fast” and “slow” in



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

165

the results. Milli-Q water was used for preparation of TCE (>99% Alfa-Aesar, Lot# X17A014)

166

solutions and breakthrough curve measurements. Water was delivered by peristaltic pump and

167

one-pore volume of pulses ~50 mg L-1 TCE were injected by a programmable syringe pump

168

equipped with a stainless steel syringe (Cole Parmer). Assay of pulse samples taken prior to and

169

after pulse was averaged to determine influent TCE concentration. Both pumps were calibrated

170

to deliver equal flow rates. Columns were initially purged with five pore volumes of water to

171

thoroughly displace air from biochar prior to breakthrough curve measurements. Particle density

172

of biochars was measured by helium pycnometry and bulk density was determined from the mass

173

of biochar contained in the columns.

174

and sequential samples were collected in 1.2 mL gas chromatographic (GC) sample vials and

175

immediately sealed without headspace using vial caps equipped with Teflon seals. Aliquots

176

were withdrawn from these sample vials and diluted into 40 mL glass vials containing about 35

177

mL water, 250 mg ascorbic acid, and six drops of 50% HCl, filled with water to eliminate

178

headspace, and capped with plastic caps equipped with pierceable Teflon septa. TCE and

179

degradation byproducts were assayed in accordance with EPA Method 524.219 using a purge and

180

trap GC (Varian CP 3800) equipped with a Tekmar Dorhmann 25 mL purge vessel, Varian

181

Saturn 2200 mass spectrometer, and Restek RTX VMS 60 m x 0.32, 0.32 mm ID GC column.

182

Restek 502.2 Cal 200 Mega Mix, 502.2 Calibration Mix 1, and 524 Internal Standard Surrogate

183

Mix were used for calibration. Data were processed using a Saturn GC/MS workstation v5.52.

184

2.6 Mathematical Model

185

A convection-dispersion chemical transport model was fitted to the measured column effluent

186

breakthrough curve data. CXTFIT v2.120 was used to estimate the retardation factor (ܴ) and

187

combined first order adsorption / degradation rate coefficient (ߤ). In this model, ܴ implies the

Column effluent was passed through stainless steel tubing


Page 8 of 26

Page 9 of 26

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


188

empirical distribution of TCE between the adsorbed and liquid phases. Since BC-ZVI adsorbs

189

and actively degrades TCE, an empirically regressed coefficient ߤ is chosen to represent the

190

efficiency of TCE reduction in comparing BC-ZVI to control biochar. Therefore, the measured

191

TCE breakthrough curves at two flow rates for BC-ZVI and control were fitted with the

192

convection-dispersion equation (CDE) for one dimensional transport of TCE, subject to

193

equilibrium adsorption and first-order degradation kinetics:

194

ܴ

డ௖ೝ డ௧

=‫ܦ‬

డ మ ௖ೝ డ௭ మ

−‫ݒ‬

డ௖ೝ డ௭

− ߤܿ௥

(1)

195

where ܿ௥ is the resident concentration of TCE, ‫ ݒ‬is the average pore-water velocity, ‫ ݐ‬is time, ‫ݖ‬

196

is distance from the influent end of the column, and ‫ ܦ‬is the dispersion coefficient, which relates

197

to the dispersivity (ߣ) and ‫ݒ‬, i.e., ‫ݒߣ = ܦ‬. ܴ is given by

198

ܴ =1+

199

200

ఘ್ ௄೏ ఏ

(2)

and ߤ is given by the first order rate in the liquid, ߤ௟ , and adsorbed phases, ߤ௦ ; ߤ = ߤ௟ +

201

ఘ್ ௄೏ ఓೞ ఏ

(3)

202

ߩ௕ is the bulk density of the packed biochar granules, ‫ܭ‬ௗ is the distribution coefficient, and ߠ is

203

the volumetric water content. A nonlinear least-squares optimization method21 is used in

204

CXTFIT to determine the optimal values of R and ߤ. In this model, the values of ߣ were

205

determined from the fast breakthrough curves and applied to fit the slow breakthrough curves for

206

respective control and BC-ZVI treatments.

207

3. Results and Discussion

208

3.1 Biochar Characterization



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 10 of 26

209

Lignin and magnetite employed in this study were fairly clean raw materials, with the lignin

210

having an ash content of 0.43% and overnight loss on drying at 105 °C and XRD analysis (not

211

shown) of the magnetite revealed 7% moisture content and evidence of both magnetite and

212

maghemite, though magnetite was the dominant crystalline structure detected in the sample.

213

Elemental analysis of the resulting BC-ZVI and control biochar (pyrolyzed lignin without

214

magnetite) presented in Table 1 reveal that the control biochar was well carbonized with

215

approximately 8% O content, measured by the difference of N, C, H, S, and ash fractions

216

determined by thermal combustion from unity, which is in good agreement with 10.47% O

217

determined by SEM-EDS analysis. The low H content of this biochar is consistent with

218

extensive condensed aromatic character of C.22 Though the 30/70 lignin-magnetite mixtures

219

were prepared and pyrolyzed under the same conditions, lower C yield is observed in BC-ZVI

220

produced from unpressed materials, suggesting that compression molding causes higher char

221

yield. More production replicates would be necessary to better understand the effect of

222

compression molding on C yield. The N, C, H, and S contents determined by thermal

223

combustion are more veritable than determined by SEM-EDS analysis, because of better

224

representative sampling and the fact that particle settling in the sample cup used in the EDS

225

analysis can cause bias as lighter particles can redistribute to the top of the sample during

226

preparation. The major elements detected in these biochars by EDS are C, O, and K likely as

227

K2O due to the lack of other anions, and additionally Fe for BC-ZVI.

228

Table 1: Elemental analysis of BC-ZVI and lignin control biochar. Element Na Ca Ha Sa Cb

50 / 50 pressed 0.02 16.69 0.00 0.66 57.46

30 / 70 pressed 0.02 9.73 0.00 0.39 48.00

30/70 unpressed 0.00 4.06 0.00 0.15 36.50


Control 0.96 88.82 0.83 1.25 86.09

Page 11 of 26

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

229 230


Nb 0.00 0.00 0.00 b O 7.88 12.04 14.70 Mgb 0.24 0.25 0.33 b Si 2.05 1.92 2.36 b S 0.14 0.07 0.18 Kb 0.52 0.22 0.18 b Ca 0.66 0.55 0.89 Feb 31.07 36.95 44.86 a Data from thermal combustion. b Data from SEM-EDS analysis.

0.00 10.47 0.03 0.14 0.16 2.92 0.13 0.06

Scanning electron microscopy revealed a broad pore size distribution in both control biochar

231

and BC-ZVI ranging from microns to several millimeters (Fig. 1). Large pores promote

232

hydraulic conductivity23 and are necessary for PRBs to function effectively. Some pores

233

observed in BC-ZVI may be continuous and allow for intraparticle transport, but interparticle

234

pore size can be designed by particle sizing. Thus, BC-ZVI production using lignin and

235

magnetite could be employed to create any size fraction or desired shape of the product material.

236

Elemental analyses presented in Table 1 reveal that C, Fe, and O predominantly constitute BC-

237

ZVI. Lighter regions in the 5000x micrographs of BC-ZVI correspond to metal phases as

238

reflecting more electrons back to the detector due to large differences in atomic mass between

239

any possible metals and carbon. As the only metal dominating is iron, Fe (56.45) reflects more

240

electrons back to the detector. These iron phases ranged from nanometers to several microns in

241

size. No differences were observed in the distribution or size of Fe phases in BC-ZVI produced

242

from different feedstock ratios. Iron phases in BC-ZVI were separated by regions of C,

243

suspended by the solid foam matrix of biochar C. This physical structure was owed to the

244

physical properties of the particular lignin selected for this study which flowed under pressure.

245

Gas expansion during pyrolysis expanded lignin as it pyrolyzed, resulting in a solid porous foam.

246

We evaluated several sources of lignin for this study, however, only the ADM lignin yielded the

247

desired physical structure of BC-ZVI upon pyrolysis; water soluble lignins yielded powder



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

248

biochars (unreported data from this study). The lignin employed to produce biochars for this

249

study was water and hexane insoluble material of frangible nugget consistency which exhibited

250

decreased viscosity upon heating. Plasticity of lignin was crucial to successful melt processing

251

as the lignin was used to suspend magnetite particles in a thermoplastic matrix which

252

transformed to char and gases upon pyrolysis.

253


Page 12 of 26

Page 13 of 26

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


254

Fig. 1: SEM micrographs of pressed BC-ZVI and control biochar. Lighter regions in the 5000x

255

micrographs are Fe phases.

256 257

XRD patterns of BC-ZVI and control biochar produced from lignin are depicted in Fig. 2. D-

258

spacings and relative intensities for XRD peaks of mineral phases detected in the biochars are

259

provided in Table 2 to facilitate interpretation of the diffraction patterns. Thermal transformation

260

of lignin and magnetite mixtures heated to 900 °C yielded biochar composited with ZVI and

261

residual magnetite and wüstite. Silicon in lignin transformed to quartz with pyrolysis. Evidence

262

for wüstite was observed in XRD patterns of biochars prepared from the 30/70 lignin-magnetite

263

mixtures. The relative intensity of wüstite to α-Fe (ZVI) and magnetite peaks was greater for

264

BC-ZVI produced from the pressed versus the unpressed mixture. Phase transformation of

265

magnetite to ZVI during pyrolysis was a reduction process10 that proceeded through an

266

intermediate wüstite phase at high temperature and low oxygen fugacity.24-26 Wüstite was a

267

metastable phase that eventually decomposed to ZVI and magnetite after cooling. Greater

268

relative intensities of wüstite reflections observed in the XRD pattern of 30/70 pressed biochar

269

indicated that more Fe was in this phase after pyrolysis, illustrating an effect of compression

270

molding on Fe transformation. Compression molding caused better mixing of lignin and

271

magnetite particles during the melt processing step and facilitated more Fe conversion to wüstite.

272

No evidence for wüstite was observed in BC-ZVI produced from the 50/50 mixture, with greater

273

relative intensities of α-Fe to magnetite reflections indicating more transformation of magnetite

274

to ZVI in this mixture. While residual magnetite was observed in all BC-ZVI, the 50/50 mixture

275

yielded the most reduction of Fe to ZVI. This greater reduction of Fe observed in the 50/50

276

mixture was due to reduction by solid C10 and reducing gases produced at high pyrolysis



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

277

temperatures,27,28 however observed residual magnetite suggested that the ratio of feedstock

278

materials could be optimized by greater lignin content and that longer heating times would allow

279

more wüstite conversion to ZVI.

280

The control biochar (c) exhibited a diffraction pattern typical of biochar,29 with broad

281

amorphous carbon reflections centered at 22, 44, and 80 °2Ө.30 While C in these biochars was

282

dominantly amorphous, evidence for graphite was observed in BC-ZVI, with greater intensity

283

observed in the BC-ZVI produced from 50/50 lignin-magnetite.

284


Page 14 of 26

Page 15 of 26

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

285 286 287 288 289


Fig. 2: XRD patterns of BC-ZVI produced from lignin and magnetite and control biochar produced from lignin. Letter identifiers describe feedstock preparation: a = 50% lignin / 50% magnetite (pressed), b = 30% lignin / 70% magnetite (pressed), c = control biochar from lignin, d = 30% lignin / 70% magnetite (unpressed). Peak labels represent crystalline structures found in biochar: α-Fe = Zerovalent iron, G = graphite, M = Magnetite, Q = Quartz, W = Wüstite.

290 291 292

Table 2: d-spacing (d) and relative intensity (I) for XRD peaks of mineral phases found in the biochars (JADE v9.0). Graphite ° 2Ө d(Å) 26.506 3.36 44.6 2.03 54.652 1.678 77.4 1.232 83.394 1.158 86.907 1.12 101.6 0.994

I(f) 100 50 80 30 50 20 40

° 2Ө 20.86 26.644 36.542 39.474 42.444 50.137 59.982

Quartz d(Å) 4.255 3.343 2.457 2.281 2.128 1.818 1.541

I(f) 20 100 10 10 10 10 10

Magnetite ° 2Ө d(Å) 30.095 2.967 35.423 2.532 43.059 2.099 53.379 1.715 56.936 1.616 62.539 1.484 73.929 1.281

I(f) 30 100 20 10 30 40 10

ZVI (α-Fe) ° 2Ө d(Å) 44.67 2.027 65.033 1.433 82.352 1.17 99.001 1.013 116.47 0.906 137.142 0.8275 -

I(f) 100 20 30 10 10 10 -

Wüstite ° 2Ө d(Å) 36.267 2.475 42.091 2.145 61.121 1.515 73.197 1.292 77.029 1.237 91.871 1.072 103.19 0.983

293 294

Raman spectroscopy was performed on biochars to obtain information regarding the structure

295

of carbon in these materials. All data were processed using Igor Pro 6.37 scientific analysis and

296

graphing software (Wavemetrics, Lake Oswego, OR, USA). Spectra were fitted to a Gaussian

297

function with a linear baseline using the multi-fit peak function in order to extract peak intensity

298

(height) and center position (Table 3). Graphitic material exhibits characteristic Raman bands

299

around 1580 cm-1 (E2g, G band) and 1360 cm-1 (A1g, D band). The D band is attributed to the

300

presence of structural defects. The intensity ratio ID/IG between the D and G band has been

301

widely used as a measure of defects in graphite-based materials.31 The overtone of the D band

302

around 2700 cm-1 (2D or G’) exhibits a strong intensity in highly ordered graphitic material.

303

Fig. 3 shows the Raman spectra of two graphite standards, lignin control biochar, and BC-

304

ZVI produced from feedstock with different lignin/magnetite ratios. The D band and G band are

305

present in the Raman spectra of the biochar materials, illustrating the graphitic character of the

306

samples. However, the biochar samples present broader G and D bands compared to the highly


I(f) 50 100 60 20 20 10 10


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

307

ordered graphite standards, which indicates a highly disordered structure in the biochar

308

samples.32 The ID/IG intensity ratios provided in Table 3 also reveal a highly disordered graphitic

309

character of C in the BC-ZVI and control biochar, with the graphite standards exhibiting one to

310

two orders of magnitude lower ID/IG ratios compared to the spectra of biochars. ID/IG ratios in

311

BC-ZVI at different lignin/magnetite ratios are statistically greater (p ≤ 0.0266) than the lignin

312

control biochar, suggesting that the presence of magnetite during the pyrolysis of lignin induces

313

some level of disorder within the biochar structure, giving C in BC-ZVI samples a greater level

314

of disorder that detected in control biochar.

315

Graphitic reflections observed in the XRD patterns of BC-ZVI (Fig. 2) indicate crystalline

316

character of graphite in BC-ZVI. This difference between graphitic C in BC-ZVI and the control

317

was likely caused by better crystalline ordering of C that deposited as graphite on wüstite and

318

magnetite surfaces by the reduction of carbonaceous pyrolysis gases at high temperatures.33,34

319

Thus, graphite in these biochars formed by two mechanisms: graphitization of lignin in

320

pyrolysis and reduction of carbonaceous gases on Fe oxide surfaces; the latter contributing to

321

increased graphite content in BC-ZVI versus control.


Page 16 of 26

Page 17 of 26

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


322 323

Fig. 3: Raman spectra of graphite standards, lignin control biochar, and BC-ZVI.

324 325

Table 3: Raman shifts of D and G bands of graphite standards, lignin control biochar, and BCZVI. D/G height ratio reported as mean ± standard deviation. Sample

D Band Graphite Standard I 1335 cm-1 Graphite Standard II 1326 cm-1 Lignin Control Biochar 1330 cm-1 Unpressed 30/70 BC-ZVI 1321 cm-1 Pressed 50/50 BC-ZVI 1324 cm-1 Pressed 30/70 BC-ZVI 1324 cm-1

G Band D/G Height Ratio 1562 cm-1 0.013 ± 0.002 1554 cm-1 0.19 ± 0.01 -1 1573 cm 1.18 ± 0.02 -1 1566 cm 1.29 ± 0.03 1563 cm-1 1.28 ± 0.03 -1 1568 cm 1.21 ± 0.02

326 327

3.2 Removal of TCE by BC-ZVI

328

Characterization results indicate that the 50/50 lignin-magnetite feedstock produced

329

macroporous biochar with zerovalent iron phases dispersed throughout the material.



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

330

Breakthrough curves of TCE through a column packed with BC-ZVI and control biochar were

331

used to evaluate interactions between BC-ZVI and a model chlorinated hydrocarbon, TCE. BC-

332

ZVI was 3 months old when breakthrough curve measurements were performed therefore we

333

assessed ZVI quality in BC-ZVI by comparing intensities of the {110} reflection of 3 months old

334

to fresh subsamples and found little evidence of change as this ratio was about 1. The relative

335

concentration maxima in the breakthrough curves of BC-ZVI (Fig. 4) were significantly smaller

336

than the relative concentration maxima of the control. Compared to the control biochars,

337

substantially less TCE transported through the BC-ZVI material, with 96% and 99% removal

338

achieved at the fast and slow flow rates. As BC-ZVI has little C relative to the control biochar

339

(Table 1), we can deduce that degradation rather than adsorption is the main cause for the low

340

relative concentrations in the BC-ZVI breakthrough curves. The relative TCE concentrations in

341

the fast-flow breakthrough curve are larger than those in the slow-flow breakthrough curve for

342

both control and BC-ZVI treatments. Fast flow rates reduce the available time for TCE to

343

interact with the biochar granules, which limits adsorption and degradation. At slower flow rates,

344

TCE transport has a larger diffusion component which promotes adsorption and degradation.

345

The equilibrium adsorption model was fitted to the control and BC-ZVI breakthrough curves

346

under slow and fast flow rates. The regression coefficients of determination (‫ ݎ‬ଶ ) were all greater

347

than 0.95. Values for ߤ (Fig. 4) of BC-ZVI were significantly larger than those of control

348

biochar for fast (p < 0.0001) and slow (p < 0.0001) flow rates, indicating that TCE removal from

349

water BC-ZVI is largely due to degradation. Though degradation dominantly accounts for the

350

value of this coefficient in breakthrough curves of BC-ZVI, significant differences in values of ߤ

351

(p = 0.0309) are associated with flow rate, indicating the need to design PRB width based on

352

expected groundwater flow rates. Values of ߤ for control biochars were not significantly


Page 18 of 26

Page 19 of 26

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


353

different (p = 0.0502), indicating that adsorption of TCE to biochar also influences transport.

354

Consistent with kinetics studies,8,11 adsorption of TCE to biochar may promote degradation by

355

increasing its local concentration near reactive iron surfaces. Trace concentrations of ethylene

356

chloride and chloroethane were detected in BC-ZVI effluent samples, while no evidence of TCE

357

degradation products was observed with control measurements. The presence of these

358

degradation products indicated that TCE reacted with ZVI, however mass recovery was not

359

possible due to volatilization losses during sampling. While analyte (TCE and degradation

360

products) volatilization likely occurred during sample collection, comparison of BC-ZVI to

361

control at identical flow rates reveal significant differences in relative concentration maxima and

362

ߤ, indicating that TCE was indeed removed by BC-ZVI. These results indicate that biochar C

363

contributes to adsorption of TCE and when composited with ZVI, together can effectively

364

remediate water contaminated with TCE.

365



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

366 367

Fig. 4: TCE Breakthrough curves of control and BC-ZVI and model parameters.

368

3.3 Environmental Implications

369

BC-ZVI produced in this study can effectively degrade aqueous TCE. Particle size may have

370

to be adjusted to increase diffusion in order to optimize TCE removal from water, which could

371

be easily adapted by cutting and sizing or even extrusion. Some potential applications are use of

372

BC-ZVI as a media in PRB and as a granular reactive carbon material for pump and treat

373

applications. The particle density of the 50/50 BC-ZVI is 5.67 g mL-1, thus this material would

374

not be subject to floating. PRBs are generally constructed with ZVI mixed with sand. One

375

major cause for decreased PRB service life using this construction approach is pore-clogging by


Page 20 of 26

Page 21 of 26

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


376

the deposition of clay and silt.1 Elimination of sand from PRB construction would reduce the

377

global warming impact of PRB construction methods associated with mining, processing, and

378

transportation. Large (3 mm) intraparticle pore diameters observed in BC-ZVI produced in this

379

study and the fact that BC-ZVI could potentially be sized in production indicate that BC-ZVI

380

could be designed to exhibit greater saturated hydraulic conductivities than sand-ZVI mixes, thus

381

would be resistant to soil deposition within the PRB, extending service life, and eliminating the

382

need for a sand matrix. For these reasons, column experiments were performed using only

383

packed granules to reveal how BC-ZVI without sand would perform as a PRB. Further research

384

is needed to assess this BC-ZVI as a PRB to understand 3-dimensional spacial and time

385

dependent transport of chlorinated hydrocarbon contaminants and to evaluate service life of PRB

386

constructed entirely of BC-ZVI.

387 388

3.4 Cost implications

389

BC-ZVI offers advantages over ZVI in that contaminant adsorption increases local contaminant

390

concentration near the reactive surface. AC-ZVI would perform similarly if not better, however,

391

comes at much higher cost as AC is inherently expensive, with PAC starting at around $750/ton

392

and GAC exceeding $2000/ton. NZVI exhibits rapid decontamination, however, production is

393

costly due to the cost and environmental impacts associated with production of borohydride

394

which is used to reduce aqueous Fe+2,3 to NZVI. NZVI can be introduced to contaminated soil as

395

a colloid and has a short service life. This approach can be effective for rapid mitigation of

396

contaminant plumes, however is not viable for long-term in-situ remediation. ZVI is probably

397

the lowest cost approach to in-situ groundwater remediation, however is also expensive, starting

398

at $500/ton for iron filings and exceeding $1500/ton for micrometer size fractions. BC-ZVI can



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

399

be produced from low-cost iron sources, biorenewable waste materials, offering a low-cost

400

alternative to producing ZVI for water remediation, sequesters some atmospheric carbon as

401

charcoal, and lowers the environmental impact of current ZVI production.

402

4. Conclusions

403

Macroporous carbon supported ZVI was successfully produced by pyrolysis of lignin and

404

magnetite at 900 °C. A 50/50 mixture of these materials yielded almost complete reduction of

405

magnetite to ZVI. Compression molding promoted iron reduction due to mixing of feedstock

406

materials achieved with melt processing. Residual magnetite and wüstite in fresh BC-ZVI

407

suggested that longer pyrolysis times and greater lignin ratio could optimize production.

408

Pyrolysis of lignin yielded carbon in control biochar and BC-ZVI that was both amorphous arene

409

C and disordered graphite. Pulse breakthrough curves revealed that adsorption and degradation

410

of TCE both influenced transport of this contaminant and that BC-ZVI produced from lignin and

411

magnetite successfully degraded TCE. The production of BC-ZVI from lignin and magnetite

412

would be very effective both in terms of cost and environmental impact. Further testing of space

413

and time scales should be performed to evaluate use of this BC-ZVI as a PRB.

414

Acknowledgements

415

Funding for this research was provided by the Agriculture and Food Research Initiative

416

Competitive Grant no. 2011-68005-30411403 from the USDA National Institute of Food and

417

Agriculture, by the Global Climate and Energy Project, Stanford Subaward Agreement 404 No.

418

60413992-112883-A, and by the National Science Foundation under Grant Number EPS-

419

1101284. We also extend appreciation to Des Moines Water Works, Des Moines, IA for

420

providing material and analytical support for this research, ADM for the lignin, and Peter T.

421

Clevenstine of the Division of Lands & Minerals, Minnesota Department of Natural Resources


Page 22 of 26

Page 23 of 26

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


422

for supplying the magnetite. The Raman measurements were supported by the U.S. Department

423

of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and

424

Biosciences through the Ames Laboratory. The Ames Laboratory is operated for the U.S.

425

Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358.

426

References

427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464

(1) Henderson, A. D.; Demond, A. H. Long-term performance of zero-valent iron permeable reactive barriers: a critical review. Environ. Eng. Sci. 2007, 24(4), 401-423. (2) Scherer, M. M.; Richter, S.; Valentine, R. L.; Alvarez, P. J. Chemistry and microbiology of permeable reactive barriers for in situ groundwater clean up. Critical Rev. Microbiol. 2008, 26(4), 221-264. (3) Higgins, M. R.; Olson, T. M. Life-cycle case study comparison of permeable reactive barrier versus pump-and-treat remediation. Environ. Sci. Technol. 2009, 43(24), 9432-9438. (4) Zhou, Y.; Gao, B.; Zimmerman, A.R.; Chen, H.; Zhang, M.; Cao, X. Biochar-supported zerovalent iron for removal of various contaminants from aqueous solutions. Bioresour. Technol. 2014, 152, 538-542. (5) Siantar, D. P.; Schreier, C. G.; Chou, C. S.; Reinhard, M. Treatment of 1, 2-dibromo-3chloropropane and nitrate-contaminated water with zero-valent iron or hydrogen/palladium catalysts. Water Res. 1996, 30(10), 2315-2322. (6) Lien, H. L.; Zhang, W. X. Transformation of chlorinated methanes by nanoscale iron particles. J. Environ. Eng. 1999, 125(11), 1042-1047. (7) Kim, Y. H.; Carraway, E. R. Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons. Environ. Sci. Technol. 2000, 34(10), 2014-2017. (8) Su, Y. F.; Cheng, Y. L.; Shih, Y. H. Removal of trichloroethylene by zerovalent iron/activated carbon derived from agricultural wastes. J. Environ. Manag. 2013, 129, 361-366. (9) Oh, S. Y.; Seo, Y. D.; Ryu, K. S. Reductive removal of 2, 4-dinitrotoluene and 2, 4dichlorophenol with zero-valent iron-included biochar. Bioresour. Technol. 2016, 216, 10141021. (10) Liu, Z.; Zhang, F.; Hoekman, S. K.; Liu, T.; Gai, C.; Peng, N. Homogeneously dispersed zerovalent iron nanoparticles supported on hydrochar-derived porous carbon. Simple, in situ synthesis and use for de-chlorination of PCBs. ACS Sustainable Chem. Eng. 2016, 4 (6), 3261– 3267. (11) Tseng, H. H.; Su, J. G.; Liang, C. Synthesis of granular activated carbon/zero valent iron composites for simultaneous adsorption/dechlorination of trichloroethylene. J. Hazard. Mater. 2011, 192(2), 500-506. (12) Marrero-Alfonso, E. Y.; Beaird, A. M.; Davis, T. A.; Matthews, M. A. Hydrogen generation from chemical hydrides. Ind. Eng. Chem. Res. 2009, 48, 3703–3712. (13) Wu, Y.; Kelly, M.; Ortega, J.; Review of Chemical Processes for the Synthesis of Sodium Borohydride; Department of Energy Cooperative Agreement DE-FC36-04GO14008; Department of Energy: Washington, D.C.; 2004. https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/review_chemical_processes.pdf (Accessed September, 2016) (14) Lawrinenko, M.; van Leeuwen, J.; Laird, D. A. Sustainable pyrolytic production of zerovalent iron. ACS Sustainable Chem. Engng. 2016, DOI 10.1021/acssuschemeng.6b02105



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

465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509

(15) Gaunt, J. L.; Lehmann, J. Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. Environ. Sci. Technol. 2008, 42(11), 41524158. (16) Woolf, D.; Amonette, J. E.; Street-Perrott, F. A.; Lehmann, J.; Joseph, S. Sustainable biochar to mitigate global climate change. Nature Commun. 2010, 1, 56. DOI 10.1038/ncomms1053 (17) Chia, C. H.; Gong, B.; Joseph, S. D.; Marjo, C. E.; Munroe, P.; Rich, A. M. Imaging of mineral-enriched biochar by FTIR, Raman and SEM–EDX. Vib. Spectrosc. 2012, 62, 248-257. (18) U.S. Environmental Protection Agency; Method 524.2: Measurement of purgeable organic compounds in water by capillary column gas chromatography/mass spectrometry; 1996. https://www.epa.gov/sites/production/files/2015-06/documents/epa-524.2.pdf (19) Casey, F. X.; Ong, S. K.; Horton, R. Degradation and transformation of trichloroethylene in miscible-displacement experiments through zerovalent metals. Environ. Sci. Technol. 2000, 34(23), 5023-5029. (20) Toride, N.; Leij, F. J.; van Genuchten, M. T. The CXTFIT code for estimating transport parameters from laboratory or field tracer experiments version 2.1. In: Research Report Vol. 137 of US Salinity Laboratory; Agricultural Research Service, US Department of Agriculture; Riverside, CA, USA; 1999. (21) Marquardt, D. W. An algorithm for least-squares estimation of nonlinear parameters. J. Soc. Ind. Appl. Math. 1963, 11(2), 431-441. (22) Brewer, C. E.; Hu, Y. Y.; Schmidt-Rohr, K.; Loynachan, T. E.; Laird, D. A.; Brown, R. C. Extent of pyrolysis impacts on fast pyrolysis biochar properties. J. Environ. Quall. 2012, 41(4), 1115-1122. (23) Amer, A. M. M.; Logsdon, S. D.; Davis, D. Prediction of hydraulic conductivity as related to pore size distribution in unsaturated soils. Soil Sci. 2009, 174(9), 508-515. (24) Pouyan, S.; Bassett, W. A.; Lin-Gun, L. Experimental determination of the effects of pressure and temperature on the stoichiometry and phase relations of wüstite. Geochim. Cosmochim. 1983, Acta. 47(4), 773-778. (25) Hazen, R. M.; Jeanloz, R. Wuestite (Fe/1-x/O)- A review of its defect structure and physical properties. Rev. Geophys. Space Phys. 1984, 22(1), 37-46. (26) Ketteler, G.; Weiss, W.; Ranke, W.; Schlögl, R. Bulk and surface phases of iron oxides in an oxygen and water atmosphere at low pressure. Phys. Chem. Chem. Phys. 2001, 3(6), 11141122. (27) Dominguez, A.; Menéndez, J. A.; Pis, J. J. Hydrogen rich fuel gas production from the pyrolysis of wet sewage sludge at high temperature. J. Anal. Appl. Pyrolysis 2006, 77(2), 127132. (28) Jie, S.; De-Ren, W.; Ye-Dong, H.; Hui-Bin, Q.; Gao, W. Reduction of oxide scale on hotrolled strip steels by carbon monoxide. Mater. Lett. 2008, 62(20), 3500-3502. (29) Lawrinenko, M.; Laird, D.A. Anion exchange capacity of biochar. Green Chem. 2015, 17(9), 4628-4636. (30) Li, Z. Q.; Lu, C. J.; Xia, Z. P.; Zhou, Y.; Luo, Z. X-ray diffraction patterns of graphite and turbostratic carbon. Carbon 2007, 45(8), 1686-1695. (31) Demir, M.; Kahveci, Z.; Aksoy, B.; Palapati, N. K.; Subramanian, A.; Cullinan, H. T.; ElKaderi, H. M.; Harris, C. T.; Gupta, R. B. Graphitic biocarbon from metal-catalyzed hydrothermal carbonization of lignin. Ind. Eng. Chem. Res. 2015, 54(43), 10731-10739.


Page 24 of 26

Page 25 of 26

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

510 511 512 513 514 515 516 517 518


(32) Dieing, T.; Hollricher, O.; Toporski, J. Confocal Raman Microscopy; New York: Springer Science & Business Media, 2011. Online access. 20 Sep. 2016 (33) Ehrensberger, K.; Palumbo, R.; Larson, C.; Steinfeld, A. Production of Carbon from Carbon Dioxide with Iron Oxides and High-Temperature Solar Energy. Ind. Eng. Chem. Res. 1997, 36 (3), 645–648. (34) Zhang, C. L.; Li, S.; Wang, L. J.; Wu, T. H.; Peng, S. Y. Studies on the decomposing carbon dioxide into carbon with oxygen-deficient magnetite: II. The effects of properties of magnetite on activity of decomposition CO2 and mechanism of the reaction. Mater. Chem. Phys. 2000, 62(1), 52-61.



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

TCE TCE

Page 26 of 26

Adsorption enhances reductive dechlorination

+ TCE

e-

0 Fe

+ TCE

e-

Cl

10 μm Macroporous carbon supported zerovalent iron for remediation of trichloroethylene ACS Paragon Plus Environment Michael Lawrinenko, Zhuangji Wang, Robert Horton, Deyny Mendivelso-Perez, Emily A. Smith, Terry E. Webster, David A. Laird, and J. (Hans) van Leeuwen

Fe+3 Pyrolytic method for production of zerovalent iron on biochar from lignin and magnetite developed and successfully tested on labscale TCE removal from water

Macroporous Carbon Supported Zerovalent Iron for Remediation of

Recommend Documents