Imaging Organophosphate and Pyrophosphate ... - ACS Publications

Subscriber access provided by Fudan University

Article

Imaging Organophosphate and Pyrophosphate Sequestration on Brucite by in Situ Atomic Force Microscopy Lijun Wang, Christine V Putnis, Helen E. King, Jörn Hövelmann, Encarnacion Ruiz-Agudo, and Andrew Putnis Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b05456 • Publication Date (Web): 08 Dec 2016 Downloaded from http://pubs.acs.org on December 9, 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.

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

1

Environmental Science & Technology

Imaging Organophosphate and Pyrophosphate Sequestration on Brucite

2

by in Situ Atomic Force Microscopy

3 Lijun Wang,*,† Christine V. Putnis,*,‡,# Helen E. King,§ Jörn Hövelmann,∆ Encarnación

4

Ruiz-Agudo,ǁ and Andrew Putnis‡,┴

5 6 †

7

College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China ‡

8

#

9 §

10 11 12

Institut für Mineralogie, University of Münster, 48149 Münster, Germany

∆

Department of Chemistry, Curtin University, Perth, WA 6845, Australia

Department of Earth Sciences, Utrecht University, 3584 CD Utrecht, The Netherlands

Interface-Geochemistry, Geoforschungszentrum Potsdam,Telegrafenberg, 14473 Potsdam, Germany ǁ

Department of Mineralogy and Petrology, University of Granada, Fuentenueva s/n 18071, Spain ┴

13

The Institute for Geoscience Research (TIGeR), Curtin University, Perth, WA 6102, Australia

14 15

Corresponding authors

16

*College of Resources and Environment, Huazhong Agricultural University, 1 Shizishan St.,

17

Wuhan 430070, China. Phone/Fax: +86-27-87288382. E-mail: [email protected] (Lijun

18

Wang).

19

Institut für Mineralogie, University of Münster, 48149 Münster, Germany. Phone

20

+49-251-8333454, Fax: +49-251-8338397. E-mail: [email protected] (Christine V.

21

Putnis)

22 23

Figures: 7 figures = 7 ×300 = 2100 word eq

24

Words: max 7000-2100 = 4900

25

Total words: 4577 (the word number of references not included) 1

ACS Paragon Plus Environment


26

Page 2 of 31

ABSTRACT

27 28

In order to evaluate the organic phosphorus (OP) and pyrophosphate (PyroP) cycle and their

29

fate in the environment, it is critical to understand the effects of mineral interfaces on the

30

reactivity of adsorption and precipitation of OP and PyroP. Here, in situ atomic force

31

microscopy (AFM) is used to directly observe the kinetics of coupled dissolution-precipitation

32

on cleaved (001) surfaces of brucite [Mg(OH)2] in the presence of phytate,

33

glucose-6-phosphate (G6P) and pyrophosphate, respectively. AFM results show that the

34

relative order of contribution to mineral surface adsorption and precipitation is phytate >

35

pyrophosphate > G6P under the same solution conditions and can be quantified by the

36

induction time of OP/PyroP-Mg nucleation in a boundary layer at the brucite-water interface.

37

Calculations of solution speciation during brucite dissolution in the presence of phytate or

38

pyrophosphate at acidic pH conditions show that the solutions may reach supersaturation with

39

respect to Mg5H2Phytate.6H2O as a Mg-phytate phase or Mg2P2O7 as a Mg-pyrophosphate

40

phase that becomes thermodynamically stable before equilibrium with brucite is reached. This

41

is consistent with AFM dynamic observations for the new phase formations on brucite. Direct

42

nanoscale observations of the transformation of adsorption/complexation-surface precipitation,

43

combined with spectroscopic characterizations and species simulations may improve the

44

mechanistic understanding of organophosphate and pyrophosphate sequestration by mineral

45

replacement reactions through a mechanism of coupled dissolution-precipitation occurring at

46

mineral-solution interfaces in the environment.

47 48

INTRODUCTION

49 50

Phosphorus (P) is a major growth limiting nutrient of plants and other organisms, and 2


Page 3 of 31


51

elevated P inputs into soil solutions and aquatic environments leads to eutrophication,

52

therefore increasing the risk of environmental pollution.1 In waters and sediments, dissolved

53

or particulate organic phosphorus (OP) is found in similar amounts to inorganic P.2 Moreover,

54

OP was recently proposed as a potential pool for bioavailable P, promoting much research

55

regarding OP decomposition,3 fractionation,4,5 and characterization.6

56

OP forms include phosphonates, myo-inositol hexakisphosphate, and orthophosphate

57

mono(di)esters.7 Phosphomonoesters in supra-/macro-molecular structures were found to

58

account for the majority of soil OP across diverse soils.8 A considerable proportion of OP in

59

soils or wetlands occurs as stereoisomers of inositol hexakisphosphate (IP6).9 The most

60

abundant myo-IP6 occurs as a phosphorus storage compound in seeds.10,11 When IP6 chelates

61

metals such as Ca, Mg, or Fe it forms an insoluble phytate, for example the common cereal

62

component phytin (Ca−Mg−K phytate).12,13 Phytate has also been detected in plant root

63

exudates.14,15 Glucose-6-phosphate (G6P), a representative sugar monoester, has also been

64

detected in soils.16

65

In addition to OPs, increased amounts of pyrophosphate form after pyrolysis of raw

66

sewage sludge,17 and pyrophosphate is present in aquatic ecosystems including marine

67

particulates18

68

of pyrophosphate in terrestrial and aquatic P cycles is unclear, though it has been shown to be

69

bioavailable even in the presence of high ambient soluble reactive P.19

and estuary sediments,19 and also is common in soil samples.20 The function

70

Most inorganic phosphorus (IP) and OP in soils, eutrophic water bodies or sewage

71

sludges are present as surface adsorbed species on minerals.21,22 The concentrations of both

72

dissolved (DP) and particulate phosphorus (PP) are correlated with the organic component

73

concentration23 in sediment containing different mineral components.24 Various OP and IP

74

compounds including PyroP in these natural environments exhibit significant differences in

75

their chemical behavior with mineral surfaces, reactivity and bioavailability.25 3



Page 4 of 31

76

OP and PyroP constitute a major component of soil phosphorus and play a key role in the

77

P cycle.26 Therefore, the dynamics of OP and PyroP in the environment,27 particularly the

78

kinetics associated with OP/PyroP-mineral surface reactions, including adsorption,

79

complexation and precipitation, will play a significant role in the biogeochemistry of these

80

molecules and their fate in different ecosystems.27 Although the roles of different mineral

81

surfaces in OP and PyroP adsorption and immobilization have been widely studied, little is

82

known regarding the kinetics of dissolution and precipitation at the brucite mineral-solution

83

interface. As a model mineral, brucite was chosen because 1) it exhibits a simple composition

84

and structure and could be an analogue for brucite-like minerals such as hydrotalcite-like

85

layered double hydroxides (LDHs that include clay minerals) with a high chemical affinity for

86

both OP and PyroP; 2) dissolution and precipitation reactions at the brucite-solution interface

87

occur easily within the AFM experimental time frame. Therefore, the objective of this study

88

was to observe the kinetic processes of brucite dissolution in the presence of phytate, G6P,

89

and pyrophosphate and coupled precipitation. In addition, we aimed to determine how the

90

number of phosphate groups in molecules regulates complexation of OP/PyroP-Mg and

91

subsequent precipitation, providing insights into the fundamental mineral interfacial

92

phenomenon in controlling OP and PyroP sequestration in the environment.

93 94

EXPERIMENTAL SECTION

95 96

Brucite Dissolution. In situ dissolution experiments were performed using a Digital

97

Instruments (Bruker) Nanoscope IIIa AFM (Multimode) operating in contact mode. A natural

98

optically clear brucite crystal (Norberg, Sweden) was cleaved in order to expose a fresh

99

cleavage (001) surface. The brucite was characterized as single phase by X-ray diffraction.

100

The solutions of phytate, G6P, and pyrophosphate (0.01 to 5.0 mM) at different pH values 4


Page 5 of 31


101

(2.7-9.6), adjusted by the addition of 0.01 M NaOH or HCl, were passed over the cleaved

102

brucite crystals in the AFM fluid cell. NaCl (1.0-100.0 mM at pH 7.0) was added to the

103

phytate or pyrophosphate solutions (1.0 mM) to observe the effects of ionic strength on

104

brucite dissolution. In situ experiments were conducted at a constant flow rate of 1 mL/min to

105

ensure surface-controlled reaction rather than diffusion (transport) control. Different locations

106

of three different crystals per solution condition were imaged to ensure reproducibility of the

107

results. In the present study, the formation of precipitates followed brucite dissolution; thus

108

we used the time before the first particles (about 2.0-6.0 nm in height) were observed on the

109

brucite surface to characterize the kinetics of nucleation.

110

Ex situ dissolution experiments (0.1-1.0 mM phytate at pH 2.7-3.7, 1.0 mM

111

pyrophosphate at pH 4.3, and 5.0 mM G6P at pH 3.5) were performed following in situ AFM

112

experiments. The reacted brucite samples were removed from the AFM fluid cell and placed

113

in a beaker filled with about 10 mL of the different solutions at room temperature for 16-24 h

114

in order to observe further precipitation reactions. After 16 h or 24 h, the samples were

115

removed from the solution and quickly dried using absorbent paper and then immediately

116

imaged in the AFM.

117

Raman Spectroscopy. Raman spectra were collected using a WITec Alpha 300R confocal

118

Raman spectrometer operating with the 785 nm line of a diode laser. A 50x long working

119

distance lens (NA 0.5) was used to obtain spatially constrained information from surface

120

precipitates produced during the AFM and batch experiments. As the precipitates were

121

sensitive to the laser beam, the laser intensity was lowered until no change was observed

122

optically or in the spectrum. Depth scans of the surfaces were taken using with an integration

123

time of 3 s. The brucite spectrum was generated from an average of 4 spectra taken from 5

124

µm below the surface. After positions were identified with additional peaks not related to

125

brucite at the surface, longer collection times were used to help identify the precipitates. 5



Page 6 of 31

126

Single spectra were taken for 3 s and integrated 30 times to obtain the best signal to noise

127

ratio. All spectra were obtained using a grating of 300 grooves/mm and a pinhole of 20 µm.

128

Spectral background removal and peak fitting was conducted using the WITec Project Plus

129

software (version 4.0).

130

Scanning electron microscopy (SEM). Imaging of the phases precipitated at the brucite

131

surfaces was conducted using a FEI Helios Nanolab G3 SEM. Images of the surface

132

precipitates were taken at 10 kV acceleration voltage and 0.8 nA probe current.

133

PHREEQC Simulations. The PHREEQC program28 was used to simulate the reactions

134

between brucite and OP/PyroP solutions using the database wateq.dat. First, we calculated the

135

solution speciation using thermodynamic constants (Table S1-S7) during brucite dissolution

136

in the presence of 1.0 mM phytate at pH 2.5 and 7.0 by PHREEQC. This provided

137

simulations of brucite dissolving until equilibrium with the solution was reached. For the

138

pyrophosphate system (1.0 mM) at more acidic pH (4.3) conditions the solution reaches

139

saturation with respect to Mg2P2O7 as a Mg-pyrophosphate phase. Moreover, we made further

140

simulations for the same solutions of 1.0 mM phytate and pyrophosphate at a fixed pH of 4.3

141

or 7.0, while allowing the pH to vary as brucite dissolved.

142 143

RESULTS AND DISCUSSION

144 145

Coupled Dissolution-Precipitation at the Brucite-Solution Interface in the Presence of

146

Phytate. Following 329 s of injection of 1 mM phytate (pH 9.0), slow dissolution occurred on

147

the exposed (001) surfaces with the formation of shallow, equilateral triangular etch pits with

148

a depth of 0.5-1.0 nm (Figure 1A, B). Pit depth increased to about 1.5 nm and 2.5-3.0 nm after

149

7 min and 43 min, respectively (Figure 1C, D). The measured depth of shallow etch pits

150

(about 0.5 nm) closely resembles the thickness of one unit-cell layer (0. 47 nm) (Figure 1E). 6


Page 7 of 31


151

Moreover, according to the brucite sheet structure with edge-sharing Mg(OH)6 octahedra

152

(Figure 1E), the equilateral triangular morphology of the etch pits results from the 3-fold

153

rotation axis normal to the (001) cleavage surface.29

154

When the brucite surface was exposed to 1 mM phytate solutions with 10 mM NaCl at

155

pH 7.0, the pit depth gradually increased to about 6.0 nm after 28 min of reaction (Figure 2A,

156

B). At the same time, spherical particles (2.0-16.0 nm in height) (Figure 2A, B) and 2-D

157

plates (14.0-16.0 nm in thickness) (Figure 2A, C) formed. As the pH of the 1 mM phytate

158

solutions was further decreased to 3.0, simultaneous occurrence of shallow and deep (>10 nm)

159

dissolution pits was observed following 279 s of dissolution reactions (Figure 2D). Rows of

160

etch pits associated with linear defects were evident on areas of the surface that remained free

161

of precipitate (Arrows in Figure 2D, E). The brucite surface became heavily pitted after 360 s

162

(Figure 2E), and finally, the surface was completely covered by nanoparticles (about 40-60

163

nm in height) after 497 s of dissolution (Figure 2F, F’). Dissolution and precipitation was

164

occurring simultaneously in a coupled process at the brucite-solution interface.30,31 The

165

dissolution of brucite releases Mg2+ ions to the interfacial solution in contact with the brucite

166

surface, so that this solution boundary layer becomes supersaturated with respect to a new

167

Mg-OP phase.

168

It is apparent that phytate-mediated brucite dissolution occurs via a different process

169

depending on the pH range. Dissolution at point defects dominated at higher pH (>7.0), and at

170

linear defects (including screw defects, line dislocations, and dislocation loops) at lower pH

171

( indicates a surface

180

site).33,35 Increasing H+ activity results in enhanced protonation of >MgOH0 surface sites and

181

the formation of >MgOH2+, thus promoting brucite dissolution.33 In addition, etch pit

182

spreading is also promoted by the presence of background electrolytes such as NaHCO3 at a

183

constant pH.33

184

Step velocity in the presence of phytate perceptibly increased as pits deepened (depth >

185

10 nm in Figure 2D), although the relationship between step retreat velocity and pit depth and

186

dependence on pH could not be determined in the present AFM experiments. The increase of

187

step velocity in phytate solutions would have contributions from the shallower, slow-retreat

188

pits at point defects promoted by water and the deeper, fast-retreat pits along linear defects

189

promoted by organic ligands such as phytate. These observations are similar to those reported

190

for the case of calcite dissolution in the presence of ethylenediamine tetraacetate (EDTA).32

191

Linear defects (such as dislocations) penetrate deeply into the mineral structure, resulting in

192

deeper pits.32,36,37

193


194

Pyrophosphate. In the presence of 1 mM pyrophosphate at pH 9.6 for 23 h, scarce isolated

195

nanoparticles (about 2.0-6.0 nm) were formed along step edges on dissolving brucite surfaces,

196

where dissolution occurred through the formation of typical equilateral triangular etch pits

197

(Figures 3A, S1A’). When the pH was lowered to 7.0 and the pyrophosphate concentration

198

was raised to 5 mM, some particles of size 10-20 nm were present after 43 min of brucite

199

dissolution (Figures 3B, S1B’). When the pH was further decreased to 4.3 in 1 mM

200

pyrophosphate, the immediate formation of pits associated with linear defects (depths in 8


Page 9 of 31


201

2.0-4.0 nm) was observed after 103 s of dissolution (Figures 3C, D, and S1D’). Spherical

202

particles (about 2.0-10.0 nm in height) (Figures 3E, S1E’) and conical precipitates (about

203

40.0-120.0 nm in height) (Figures 3F, S1F’) were formed after 192 s and 37 min, respectively.

204


205

G6P. In the presence of 1 mM G6P at pH 5.9, dissolution occurred with the formation of

206

equilateral triangular etch pits on the brucite (001) surfaces, and their depth gradually

207

increased from about 4.0 nm at 13 min, to about 8.0 nm at 41 min, and 8.0-10.0 nm at 81 min

208

(Figure 4). At the same time, their sizes (width) also increased (Figure 4A’-C’). However, no

209

precipitates were observed even after 17 h of ex situ reactions (Figure S2). As the G6P

210

concentration was increased to 5 mM at pH 5.8, precipitates were formed after 18 h in ex situ

211

reactions (Figure S3). When the pH of 5 mM G6P solutions was decreased to 3.5, etch pits

212

rapidly formed (Figure 5); the brucite surfaces were completely covered by particles (Figure 5)

213

with a height of 40-50 nm (Figure S4A, B) after 16 h of dissolution reactions.

214

Dynamics of Nucleation and Growth of Mg-OP/PyroP on Brucite. The dissolving brucite

215

surfaces in the presence of OPs and pyrophosphate provided a source of Mg2+ ions, resulting

216

in supersaturation of the solution in the brucite-solution boundary layers with respect to an

217

OP/PyroP-Mg phase.38 This will drive surface-induced nucleation and growth on the brucite

218

surface. According to classical nucleation theory (CNT), the steady-state nucleation rate

219

(number of nucleation events per square meter per second), J, can be calculated as:39,40

220

exp

∆

(1)

221

where A is a kinetic constant, depending on physical parameters such as diffusional

222

barriers,39,40 ΔG* is the total free-energy cost to form a spherical crystallite, kB is Boltzmann’s

223

constant, and T is temperature.39,40 The technical difficulties involved in directly evaluating

224

crystal nucleation rates41 have led to an approach to measure the induction period (t) prior to

225

nucleation based on the equation J =1/(tV),41 where V is the volume of the entire system (i.e. 9



Page 10 of 31

226

fluid + crystal, about 50 μL). In the present study, we used the time required to observe the

227

occurrence of the first smallest particles (about 2.0-6.0 nm in height) on brucite to

228

characterize the kinetics of nucleation. Moreover, we only compared the induction times for

229

phytate and pyrophosphate solutions on brucite surfaces because a relatively longer time was

230

required to form nucleated particles for solutions containing G6P (Figure S2). The most likely

231

explanation for delayed nucleation in GP6 solutions is that G6P contains the lowest number of

232

phosphate groups 1) compared to the other two molecules tested, 2) and hence indicates a

233

lower chelation ability. The induction time significantly increased with the increase in pH for

234

both phytate and pyrophosphate solutions at 1 mM, and at the same alkaline pH, the induction

235

time for pyrophosphate (1 mM) is much longer than that of phytate (1 mM)

236

Shorter induction times were observed with increasing phytate or pyrophosphate solution

237

concentration (Figure 6B) or NaCl concentration (in 1 mM phytate or pyrophosphate) (Figure

238

6C) when the solution pH was kept constant (7.0).

(Figure 6A).

239

Mineral dissolution kinetics is complicated in the presence of inorganic/organic ligands42

240

and background electrolytes.34,43 Background electrolytes can enhance the mineral dissolution

241

rate due to the ability of salt ions to modify water structure as well as solute and mineral

242

surface hydration.43,44 The amount of released Mg2+ ions by dissolution is increased in the

243

presence of NaCl, thereby resulting in rapid nucleation of a Mg-OP/PyroP phase with shorter

244

induction times because a higher degree of supersaturation is reached within the boundary

245

layers. This phenomenon has also been observed in the calcite-G6P system.44

246

Identification of Precipitates on Brucite (001) Cleavage Surfaces. Using Raman

247

spectroscopy, the cleaved brucite surface shows two sharp, intense peaks at 281 and 446 cm-1

248

and two broad peaks with centres at 725 and 809 cm-1 (Figure 7A). This is consistent with

249

previous analysis of brucite using spectroscopic methods.45 In contrast, precipitates on the

250

brucite surface show additional peaks depending on the organophosphate present in the 10


Page 11 of 31


251

experiment solution. In experiments with G6P, the precipitates were highly reactive to the

252

laser beam and even at the lowest laser intensity were burnt during analysis. However, the

253

burnt material produced broad peaks at 1332 and 1575 cm-1 (Figure 7B) that are characteristic

254

for amorphous carbon material46 implying the original material was carbon-bearing,

255

consistent with the precipitation of an organic-C phase during the experiments. Precipitates on

256

the surface of brucite produced during the phytate experiments were stable in the Raman laser

257

and produced clear peaks in the Raman spectra (Figure 7C). Additional peaks were observed

258

as a broad peak at 544 cm-1, three sharp and one broad peak at 954, 993, 1034 and 1100 cm-1

259

and two broad bands at 1282 and 1372 cm-1. These peaks are consistent with known Raman

260

peaks for solid samples of phytate47,48 and particularly those between 950 and 1100 cm-1 are

261

related to the symmetrical stretch of the phosphate moiety within the phytate molecule.

262

However, the peaks are consistently shifted to higher wavenumbers in comparison to previous

263

studies by as much as 10 cm-1 compared to the initial sodium salt.49 Such a shift could imply a

264

difference in chemistry of the precipitates through the incorporation of Mg released from the

265

dissolving brucite, as Mg-acetate has been found to show a shift to higher wavenumbers in

266

comparison to the Na-acetate salt.50 No additional bands to those belonging to brucite were

267

observed on the pyrophosphate sample surface. This can be explained from the SEM

268

observations because the precipitate forms very thin, spread out crystals on the surface

269

(Figure S5). In this case the laser beam would not sample enough of the precipitate during

270

Raman analysis to produce bands in the spectra, precluding any possible identification of

271

other vibrational peaks from any nanometer thin precipitate layer.

272

PHREEQC Simulations. Finally, we calculated the solution speciation using thermodynamic

273

constants (Table S1-S7) during brucite dissolution in the presence of 1.0 mM phytate at pH

274

2.5 and 7.0 by PHREEQC.28 This allowed simulations of brucite dissolving until equilibrium.

275

The simulations show that for both initial pH values, the solution (volume of solution is 11



Page 12 of 31

276

equivalent to that of the AFM fluid cell, about 35-50 μL) would reach supersaturation with

277

respect to Mg5H2Phytate.6H2O as a Mg-phytate phase (Supporting Data 1 and 2). This is

278

consistent with the AFM results (Figure 2). For the pyrophosphate system (1.0 mM) at more

279

acidic pH (4.3) the solution reaches saturation with respect to Mg2P2O7 as a

280

Mg-pyrophosphate phase, that may become stable before equilibrium with brucite is attained

281

(Supporting Data 3). At pH ≥7.0, the solution is saturated with respect to brucite before

282

saturation with respect to Mg2P2O7 is attained (Supporting Data 4 and 5). This means for the

283

formation of Mg2P2O7 at higher pH more brucite would need to dissolve (to release enough

284

Mg2+) through the addition of higher pyrophosphate concentrations and/or longer reaction

285

times. These simulation results are also consistent with the AFM observations (Figure 3).

286

Moreover, we made further simulations for the same solutions of 1.0 mM phytate and

287

pyrophosphate at a fixed pH of 4.3 or 7.0, while allowing the pH to vary as brucite dissolved.

288

Results showed that both Mg5H2Phytate.6H2O and Mg2P2O7 become thermodynamically

289

stable due to the solutions reaching supersaturation with respect to these two phases

290

(Supporting Data 6-8). Because it is impossible to include all possible species in the database

291

and appropriate equilibrium constants are mostly lacking, the simulations are incomplete,

292

especially for the formation of other solid phases, for example hydrated Mg2P2O7.

293

Due to the limitation of appropriate thermodynamic data, all PHREEQC simulations were

294

an approximation to the real scenario. However the simulations predicted the fast formation of

295

a Mg-phytate phase at the pH values tested. The Mg-PyroP phase did not form at pH ≥ 7 and

296

only became significant at lower pH values when dissolution of brucite was enhanced. This is

297

in accordance with the AFM observations and Raman analyses, especially, as Raman analyses

298

for ex situ formation of precipitates on the surface of brucite verify the utility of speciation

299

modeling. The lack of equilibrium constant data did not allow for simulations with G6P.

300

In summary, from our observations a higher number of phosphate groups in a phosphate 12


Page 13 of 31


301

molecule seems to enhance the chelating ability of the molecule to sequester Mg2+. The

302

reaction rates of dissolution and subsequent precipitation followed the order: phytate (with 6

303

phosphate groups per molecule) > pyrophosphate (2 phosphate groups) > G6P (1 phosphate

304

group) at all pH values tested.

305

Implications. A fundamental challenge in the study of soil organic and inorganic phosphate

306

dynamics is to assess the relative importance of adsorption and precipitation processes on

307

mineral surfaces in the environment as this plays an important role in the global P cycle.44 In

308

this study, direct AFM observations and kinetic analyses have been applied to observe and

309

predict the behavior of OPs and PyroP on brucite mineral surfaces. Our results may provide

310

dynamic insights into how OP and PyroP can be sequestered through mineral interfacial

311

dissolution-precipitation reactions.51 The approach used in this study may readily extend to

312

further investigate the adsorption and precipitation dynamics of guest anions/cations on the

313

surfaces and in the interlayer spaces in brucite-like minerals such as hydrotalcite-like layered

314

double hydroxides (LDHs).52 These minerals are of considerable environmental relevance

315

because of their anion-exchange capacity that can affect the mobility of chemical species and

316

removal of toxic anions.52 Moreover, these materials can accommodate a wide range of

317

different cations in the interlayer spaces for use in environmental remediation of heavy

318

metals.52,53

319 320

ASSOCIATED CONTENT

321 322

Supporting Information. AFM images and depth profiles of brucite dissolution and

323

precipitation in the presence of pyrophosphate (Figure S1); ex situ reaction of 1 mM G6P with

324

brucite (Figure S2); ex situ reaction of 5 mM G6P with brucite (Figure S3); depth profile of

325

brucite substrates covered by larger nanoparticles in 5 mM G6P at pH 3.5 (Figure S4); SEM 13



Page 14 of 31

326

images of brucite with OPs under different reaction conditions (Figure S5); Protonation

327

constants for phytate (Table S1); Association constants for Mg-phytate complexes (Table S2).

328

Solubility constants of possible solid phases (Mg-phytate) (Table S3). Protonation constants

329

for pyrophosphate (PyroP) (Table S4). Association constants for Na-pyrophosphate

330

complexes (Table S5). Association constants for Mg-pyrophosphate complexes (Table S6).

331

Solubility constants of possible solid phases (Mg-PyroP) (Table S7), and PHREEQC

332

calculations (Supporting Data 1-8). This material is available free of charge via the Internet at

333

http://pubs.acs.org.

334 335

AUTHOR INFORMATION

336 337

Corresponding authors

338

*E-mail: [email protected] (Lijun Wang); [email protected] (Christine V. Putnis)

339 340

ACKNOWLEDGMENT

341

This work was supported by the National Natural Science Foundation of China (41471245

342

and 41071208), a Specialized Research Fund for the Doctoral Program of Higher Education

343

(20130146110030), and the Fundamental Research Funds for the Central Universities

344

(2662015PY206, 2662015PY116). C.V. Putnis and A. Putnis acknowledge support through

345

EU Marie Curie initial training networks (FlowTrans and CO2 React). E.R.-A. acknowledges

346

a Ramón y Cajal grant and support from the Research Group RNM-179 of the Junta de

347

Andalucía.

348 349

REFERENCES 14


Page 15 of 31

350


(1)

351 352

10, 439–454. (2)

353 354

Baldwin, D. S. Organic phosphorus in the aquatic environment. Environ. Chem. 2013,

Turner, B. L.; Frossard, E.; Baldwin, D. S. Organic Phosphorus in the Environment; CABI Publishing: Cambridge, 2005.

(3)

Dyhrman, S.; Chappell, P.; Haley, S.; Moffett, J.; Orchard, E.; Waterbury, J.; Webb,

355

E.

356

Trichodesmium. Nature 2006, 439, 68−71.

357

(4)

Phosphonate

utilization

by

the

globally

important

marine

diazotroph

Zhu, Y. R.; Wu, F. C.; He, Z. Q.; Guo, J. Y.; Qu, X. X.; Xie, F. Z.; Giesy, J. P.; Liao,

358

H. Q.; Guo, F. Characterization of organic phosphorus in lake sediments by sequential

359

fractionation and enzymatic hydrolysis. Environ. Sci. Technol. 2013, 47, 7679−7687.

360

(5)

Lu, C.; Wang, B.; He, J.; Vogt, R. D.; Zhou, B.; Guan, R.; Zuo, L., Wang, W.; Xie, Z.;

361

Wang, J.; Yan, D. Responses of organic phosphorus fractionation to environmental

362

conditions and lake evolution. Environ. Sci. Technol. 2016, 50, 5007−5016.

363

(6)

Ahlgren, J.; Tranvik, L.; Gogoll, A.; Waldebäck, M.; Markides, K.; Rydin, E.

364

Sediment depth attenuation of biogenic phosphorus compounds measured by 31P

365

NMR. Environ. Sci. Technol. 2005, 39, 867−872.

366

(7)

Cade-Menun, B. J.; Navaratnam, J. A.; Walbridge, M. R. Characterizing dissolved

367

and particulate phosphorus in water with 31P nuclear magnetic resonance

368

spectroscopy. Environ. Sci. Technol. 2006, 40, 7874−7880.

369

(8)

McLaren, T. I.; Smernik, R. J.; McLaughlin, M. J.; McBeath, T. M.; Kirby, J. K.;

370

Simpson, R. J.; Guppy, C. N.; Dooletter, A. L.; Richardson, A. E. Complex forms of

371

soil organic phosphorus-A major component of soil phosphorus. Environ. Sci.

372

Technol. 2015, 49, 13238−13245.

15



373

(9)

Page 16 of 31

Sims, J. T.; Pierzynski, G. M. Chemistry of Phosphorus in Soils. In Chemical

374

Processes in Soils; Tabatabai, M. A., Sparks, D. L., Eds.; Soil Science Society of

375

America: Madison, WI, 2005; pp 151−192.

376

(10) Turner, B. L.; Cheesman, A. W.; Godage, H. Y.; Riley, A. M.; Potter, B. V. L.

377

Determination of neo- and D-chiro-inositol hexakisphosphate in soils by solution 31P

378

NMR spectroscopy. Environ. Sci. Technol. 2012, 46, 4994−5002.

379

(11) Azeem, M.; Riaz, A.; Chaudhary, A. N.; Hayat, R.; Hussain, Q.; Tahir, M. I.; Imran,

380

M. Microbial phytase activity and their role in organic P mineralization. Arch. Agron.

381

Soil Sci. 2015, 61, 751−766.

382 383

(12) Turner, B. L.; Paphazy, M. J.; Haygarth, P. M.; McKelvie, I. D. Inositol phosphates in the environment. Philos. Trans. R. Soc., B 2002, 357, 449−469.

384

(13) Thavarajah, P.; Thavarajah, D.; Vandenberg, A. Low phytic acid lentils (Lens

385

culinaris L.): a potential solution for increased micronutrient bioavailability. J. Agric.

386

Food Chem. 2009, 57, 9044−9049.

387

(14) Tu, S. X.; Ma, L.; Luongo, T. Root exudates and arsenic accumulation in arsenic

388

hyperaccumulating Pteris vittata and nonhyperaccumulating Nephrolepis exaltata.

389

Plant Soil 2004, 258, 9−19.

390

(15) Liu, X.; Fu, J. W.; Guan, D. X.; Cao, Y.; Luo, J.; Rathinasabapathi, B.; Chen, Y. S.;

391

Ma, L. Q. Arsenic induced phytate exudation, and promoted FeAsO4 dissolution and

392

plant growth in As-hyperaccumulator Pteris vittata. Environ. Sci. Technol. 2016, 50,

393

9070−9077.

394

(16) Espinosa, M.; Turner, B. L.; Haygarth, P. M. Preconcentration and separation of trace

395

phosphorus compounds in soil leachate. J. Environ. Qual. 1999, 28, 1497−1504.

16


Page 17 of 31

396 397


(17) Huang, R. X.; Tang, Y. Z. Speciation dynamics of phosphorus during (hydro)thermal treatments of sewage sludge. Environ. Sci. Technol. 2015, 49, 14466−14474.

398

(18) Paytan, A.; Cade-Menun, B. J.; McLaughlin, K.; Faul, K. L. Selective phosphorus

399

regeneration of sinking marine particles: evidence from 31P NMR. Mar. Chem. 2003,

400

82, 55−70.

401

(19) Sundareshwar, P. V.; Morris, J. T.; Pellechia, P. J.; Cohen, H. J.; Porter, D. E.; Jones,

402

B. C. Occurrence and implications of pyrophosphate in estuaries. Limnol. Oceanogr.

403

2001, 46, 1570−1577.

404 405 406 407

(20) Cade-Menun, B. J. Organic Phosphorus in the Environment; CABI Publishing: Oxon, U.K., 2005. (21) Selig, U.; Hübener, T.; Michalik, M. Dissolved and particulate phosphorus forms in a eutrophic shallow lake. Aquat. Sci. 2002, 64, 97–105.

408

(22) Nõges, P.; Tuvikene, L.; Nõges, T.; Kisand, A. Primary production, sedimentation

409

and resuspension in large shallow Lake Võrtsjärv. Aquat. Sci. 1999, 61, 168–182.

410

(23) Shinohara, R.; Imai, A.; Kawasaki, N.; Komatsu, K.; Kohzu, A.; Miura, S.; Sano, T.;

411

Satou, T.; Tomioka, N. Biogenic phosphorus compounds in sediment and suspended

412

particles in a shallow eutrophic lake: A

413

Environ. Sci. Technol. 2012, 46, 10572−10578.

31

P-nuclear magnetic resonance study.

414

(24) Shinohara, R.; Imai, A.; Kohzu, A.; Tomioka, N.; Furusato, E.; Satou, T.; Sano, T.;

415

Komatsu, K.; Miura, S.; Shimotori, K. Dynamics of particulate phosphorus in a

416

shallow eutrophic lake. Sci. Total Environ. 2016, 563-564, 413–423.

417

(25) Condron, L. M.; Turner, B. L.; Cade-Menun, B. J. Chemistry and dynamics of soil

418

organic phosphorus. In Phosphorus: Agriculture and the Environment; Sims, T., 17



Page 18 of 31

419

Sharpley, A. N., Eds.; American Society of Agronomy: Madison, Wisconsin, 2005;

420

pp 87–121.

421

(26) Turner, B. L.; Newman, S.; Ramesh Reddy K. Overestimation of organic phosphorus

422

in wetland soils by alkaline extraction and molybdate colorimetry. Environ. Sci.

423

Technol. 2006, 40, 33493–3354.

424 425

(27) Turner, B. L., Frossard, E., Baldwin, D. S. Organic Phosphorus in the Environment; CAB International: Wallingford, 2005.

426

(28) Parkhurst, D. L.; Appelo, C. A. J. Users guide to PHREEQC (Version 3). A Computer

427

Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse

428

Geochemical Calculations: U.S. Geological Survey Techniques and Methods; U.S.

429

Geological Survey: Washington, DC, 2013.

430

(29) Kudoh, Y.; Kameda, J.; Kogure, T. Dissolution of brucite on the (001) surface at

431

neutral pH: in situ atomic force microscopy observations. Clays Clay Miner. 2006, 54,

432

598−604.

433

(30) Putnis, A. Mineral replacement reactions. In: Oelkers, E.H., Schott, J. (Eds.), Thermo-

434

dynamics and Kinetics of Water–Rock Interaction. Reviews in Mineralogy & Geoche

435

mistry 2009, 30, 87–124.

436 437

(31) Ruiz-Agudo, E.; Putnis, C.V.; Putnis, A. Coupled dissolution and precipitation at min eral–fluid interfaces. Chem. Geol. 2014, 383, 132–146.

438

(32) Perry, T. D.; Duckworth, O. W.; Kendall, T. A.; Martin, T. A.; Mitchell, R. Chelating

439

ligand alters the microscopic mechanism of mineral dissolution. J. Am. Chem. Soc.

440

2005, 127, 5744−5745.

441

(33) Hövelmann, J.; Putnis, C. V.; Ruiz-Agudo, E.; Austrheim, H. Direct nanoscale

442

observations of CO2 sequestration during brucite [Mg(OH)2] dissolution. Environ. Sci. 18


Page 19 of 31

443


Technol. 2012, 46, 5253−5260.

444

(34) Wang, L. J.; Ruiz-Agudo, E.; Putnis, C. V.; Menneken, M.; Putnis, A. Kinetics of

445

calcium phosphate nucleation and growth on calcite: Implications for predicting the

446

fate of dissolved phosphate species in alkaline soils. Environ. Sci. Technol. 2012, 46,

447

834−842.

448

(35) Pokrovsky, O. S.; Schott, J. Experimental study of brucite dissolution and

449

precipitation in aqueous solutions: surface speciation and chemical affinity control.

450

Geochim. Cosmochim. Acta 2004, 68, 31−45.

451 452 453

(36) MacInnis, I. N.; Brantley, S. L. The role of dislocations and surface morphology in calcite dissolution. Geochim. Cosmochim. Acta 1992, 56, 1113−1126. (37) Duckworth, O. W.; Martin, S. T. Dissolution rates and pit morphologies of

454

rhombohedral carbonate minerals. Am. Mineral. 2004, 89, 554−563.

455

(38) Putnis, A. Why mineral interfaces matter. Science 2014, 343, 1441−1442.

456

(39) Liu, X. Y.; Lim, S. W. Templating and supersaturation driven anti-templating:

457

Principles of biominerals architecture. J. Am. Chem. Soc. 2003, 125, 888−895.

458

(40) Nielsen, A. E. Kinetics of Precipitation; Pergamon: Oxford, U.K., 1964

459

(41) Wang, L. J.; Guan, X.; Tang, R.; Hoyer, J. R.; Wierzbicki, A.; De Yoreo, J. J.;

460

Nancollas, G. H. Phosphorylation of osteopontin is required for inhibition of calcium

461

oxalate crystallization. J. Phys. Chem. B 2008, 112, 9151−9157.

462

(42) Qin, L. H.; Zhang, W. J.; Lu, J. W.; Stack, A. G.; Wang, L. J. Direct imaging of

463

nanoscale dissolution of dicalcium phosphate dihydrate by an organic ligand:

464

Concentration matters. Environ. Sci. Technol. 2013, 47, 13365−13374.

465

(43) Ruiz-Agudo, E.; Kowacz, M.; Putnis, C. V.; Putnis, A. The role of background 19



Page 20 of 31

466

electrolytes on the kinetics and mechanism of calcite dissolution. Geochim.

467

Cosmochim. Acta 2010, 74, 1256−1267.

468

(44) Wang, L. J.; Qin, L. H.; Putnis, C. V.; Ruiz-Agudo, E.; King, H. E.; Putnis, A.

469

Visualizing organophosphate precipitation at the calcite-water interface by in situ

470

atomic-force microscopy. Environ. Sci. Technol. 2016, 50, 259−268.

471

(45) Dawson, P.; Hadfield, C. D.; Wilkinson, G. R. The polarized infra-red and Raman

472

spectra of Mg(OH)2 and Ca(OH)2. J. Phys. Chem. Solids 1973, 34, 1217–1225.

473

(46) Ferrari, A. C.; Robertson, J. Interpretation of Raman spectra of disordered and

474

amorphous carbon. Phys. Rev. B 2000, 61, 14095–14107.

475

(47) Kolozsvari, B.; Firth, S.; Saiardi, A. Raman spectroscopy detection of phytic acid in

476

plant seeds reveals the absence of inorganic polyphosphate. Molecular Plant 2015, 8,

477

826–828.

478

(48) Yang, H. F.; Feng, J.; Liu, Y. L.; Yang, Y.; Zhang, Z. R.; Shen, G. L.; Yu, R. Q.

479

Electrochemical and surface enhanced Raman scattering spectroelectrochemical study

480

of phytic acid on the silver electrode. J. Phys. Chem. B 2004, 108, 17412–17417.

481

(49) Yang, H.; Yang, Y.; Yang, Y.; Liu, H.; Zhang, Z.; Shen, G.; Yu, R. Formation of

482

inositol hexaphosphate monolayers at the copper surface from a Na-salt of phytic acid

483

solution studied by in situ surface enhanced Raman scattering spectroscopy, Raman

484

mapping and polarization measurements. Anal. Chim. Acta 2005, 458, 150–165.

485

(50) Frost, R. L.; Kloprogge, J. T. Raman spectroscopy of the acetates of sodium,

486

potassium and magnesium at liquid nitrogen temperature. J. Mol. Struct. 2000, 526,

487

131–141.

488

(51) Putnis, C.V.; Ruiz-Agudo, E. The mineral-water interface: where minerals react with 20


Page 21 of 31

489


the environment. Elements 2013, 9, 177–182.

490

(52) Sideris, P. J.; Nielsen, U.; Gan, Z.; Grey, C. P. Mg/Al ordering in layered double

491

hydroxides revealed by multinuclear NMR spectroscopy. Science 2008, 321,

492

113–117.

493

(53) Liang, X.; Zang, Y.; Xu, Y.; Tan, X.; Hou, W.; Wang, L.; Sun, Y. Sorption of metal

494

cations on layered double hydroxides. Colloids and Surfaces A: Physicochem. Eng.

495

Aspects 2013, 433, 122– 131.

496 497

Figure Legends

498 499

Figure 1. Time sequence AFM (deflection mode) images of natual brucite dissolution. (A-D)

500

Time-lapse images show equilateral triangular etch pit formation and evolution on the (001)

501

cleavage plane (the white circles in B-D) after injection of 1 mM phytate (pH 9.0) into a

502

flow-through cell. Images A-C, 3×3 μm; D, 5×5 μm. (A’-D’) Depth profile of the etch pit at

503

t =245 s, 329 s, 7 min, or 43 min, respectively, measured along the white dashed lines in

504

(A-D). (E) The brucite atomic structure projected along the b-axis (in right panel of E; 0.47

505

nm of the thickness of one Mg(OH)2 layer), and the c-axis (in left panel of E; the morphology

506

and crystallographic orientation of the edges of the triangular etch pits is indicated).

507 508

Figure 2. Time sequence AFM (deflection mode) images of brucite dissolution and

509

precipitation in the presence of phytate. (A) In situ AFM images show both etch pit formation

510

and precipitation on a brucite (001) surface in 1 mM phytate + 10 mM NaCl (pH 7.0) at t =28

511

min. (B and C) Height profiles of nucleated nanoparticles (about 2-16 nm) and 2-D nanoplates

512

(about 16 nm in thickness) along the dashed lines 1→1’ and 2→2’, respectively. (D and E) 21



Page 22 of 31

513

Time-resolved AFM images show the coexistence of point and line defects formed in 1 mM

514

phytate (pH 3.0). Pits associated with observable line defects are apparent (Arrows). (D’ and

515

E’) Depth profiles of etch pits and line defects along the dashed lines 3→3’ and 4→4’,

516

respectively. (F) After 497 s, brucite substrates were covered by larger nanoparticles (about

517

50 nm in F’). Image A, 3×3 μm; D-F, 5×5 μm.

518 519

Figure 3. Time sequence AFM (deflection mode) images of brucite dissolution and

520

precipitation in the presence of pyrophosphate. In situ AFM images show coupled dissolution

521

(by etch pit formation) and precipitation on a brucite (001) surface in (A) 1 mM

522

pyrophosphate (pH 9.6) at t =23 h and (B) 5 mM pyrophosphate (pH 7.0) at t =43 min.

523

Time-resolved AFM images show (C and D) the formation of pits associated with line defects,

524

and (E and F) spherical particles and conical precipitates in 1 mM pyrophosphate (pH 4.3).

525

Images A and C-F, 3×3 μm; B, 5×5 μm.

526 527

Figure 4. Time sequence AFM (deflection mode) images of brucite dissolution in the

528

presence of G6P. (A-C) In situ AFM images of a brucite (001) surface dissolving in 1 mM

529

G6P (pH 5.9). (A’-C’) Depth profiles of the etch pits evaluated along the white dashed lines

530

in A-C. Images A-C, 3×3 μm.

531 532

Figure 5. Time-resolved AFM (deflection mode) images of brucite dissolution and

533

precipitation in the presence of G6P. In situ AFM images show both (A-C) etch pit formation

534

and evolution, and (D) precipitation on a brucite (001) surface in 5 mM G6P (pH 3.5). After

535

16 h, brucite substrates were covered by larger nanoparticles. Images A-D, 3×3 μm.

536 537

Figure 6. Induction times for precipitate formation on the brucite (001) surfaces under 22


Page 23 of 31


538

various experimental conditions in the presence of phytate or pyrophosphate. (A) A range of

539

pH values, (B) Phytate or pyrophosphate concentrations at pH 7.0, and (C) NaCl

540

concentrations with 1 mM phytate or pyrophosphate at pH 7.0. Induction times are reported as

541

mean ± SD.

542 543

Figure 7. Raman spectra taken from (A) brucite, and surface precipitates from an AFM

544

experiment run with (B) G6P or (C) phytate. Asterisks indicate peaks unrelated to the

545

underlying brucite generated by the surface precipitates in the different organic phosphate

546

experiments.

547 548 549 550 551

23



A’

A

Page 24 of 31

3.0

Depth (nm)

2.5 2.0 1.5 1.0 0.5

~0.5 nm

0.0 0.7

B’

0.8

0.9 1.0 1.1 1.2 Distance (μm)

1.3

1.4

1.7

1.8

3.5 3.0

1 mM phytate, pH 9.0 t = 245 s

Depth (nm)

2.5

B

2.0 1.5 1.0

~1.0 nm

0.5 0.0 1.1

C’

1.2

1.3

1.4 1.5 1.6 Distance (μm)

5

Depth (nm)

4

329 s

3 2 1

~1.5 nm

0 1.0

C

1.2 1.4 Distance (μm)

1.6

D’ 7 6

Depth (nm)

5

~3 nm

4 3 2

~2.5 nm

1 0 1.4

1.6

1.8


2.6

2.8

E

7 min

0.47 nm

D

b

552 553

43 min

c

c a

b

a

Figure 1

24


Page 25 of 31


A B

2

C

25

15

~2.0 nm

10 5

2’

1

~16.0 nm

~6.0 nm 0.5


1 mM phytate + 10 mM NaCl pH 7.0 t = 28 min

2.5

3’

4

15 10 5

555

E’

1

2 3 Distance (μm)

4

5

2.5

3.0

497 s

4’

4

30 20 10

7000 6000 5000 4000 3000 2000 1000 0

0


F’ 8000

50

0

0

0.5

4’

40

20

2 0.0

360 s

Depth (nm)

Depth (nm)

25

3’

3

2’

F

1 mM phytate, pH 3.0 t = 279 s

D’ 30

18 16 14 12 10 8 6 4 2 0

3.0

E

3

554

1’

0 0.0

D

Height (nm)

20

Number of events

1’

Height (nm)

1

0

1

2 3 4 Distance (μm)

5

0

10 20 30 40 50 60 70 80 Height (nm)

Figure 2

556 557 558 559 560 561 562 563 564 565 25



A

1 mM pyrophosphate, pH 9.6 t = 23 h

B

C

H2O, pH 4.3

D

E

192 s

F

Page 26 of 31

5 mM pyrophosphate, pH 7.0 t = 43 min

1 mM pyrophosphate, pH 4.3 t = 103 s

37 min

566 567

Figure 3

568 569 570 571 572 573 574 575 576 26



A

1 mM G6P, pH 5.9 t = 13 min

10 Depth (nm)

B’ 12

4 Depth (nm)

578

41 min

A’ 5 3 2 1

0.0


2.5

3.0

10

8 6 4

0.0

81 min

12 8 6 4 2

0

0.5

C

C’ 14

2

0

577

B

Depth (nm)

Page 27 of 31

0 0.5


2.5

3.0

0.0

0.5


2.5

3.0

Figure 4

579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 27



Page 28 of 31

A

H2O, pH 6.0

B

5 mM G6P, pH 3.5 t = 109 s

C

43 min

D

16 h

594 595

Figure 5

596 597 598 599 600 601 602 603 604 605 606 607 608 28


Page 29 of 31


A 1600 1400 1200 1000 800 600 400 200 0

Induction time (min)

Pyrophosphate 1 mM Phytate or Pyrophosphate

Phytate

3

4

5

6

7

8

9

10

pH


B 250 Phytate pH 7.0

200 150 100 50 0

0.01

0.1 1 Concentration (mM)


C 180 160 140 120 100 80 60 40 20 0

610

10

1 mM Phytate or Pyrophosphate pH 7.0

Pyrophosphate Phytate

0

609

Pyrophosphate pH 7.0

20

40 60 NaCl (mM)

80

100

Figure 6

611 612 613 614 615 616 617 618 619 29


Intensity (a. u.)


*

* * ** * * * *

Page 30 of 31

Phytate on brucite

C G6P on brucite

*

B brucite

A

0 620

500 1000 1500 -1 Wavenumbers (cm )

2000

621 622

Figure 7

623 624 625 626 627 628 629 630 631 632 633 634 635 636 30


Page 31 of 31


1 mM phytate, pH 3.0

5 mM pyrophosphate, pH 7.0

1 mM pyrophosphate, pH 4.3

or 5 mM G6P, pH 3.5

637 638

TOC Graphical abstract

31


Imaging Organophosphate and Pyrophosphate ... - ACS Publications

Recommend Documents