Reductive Transformation of 2,4-Dinitrotoluene: Roles of Iron and Natural Organic Matter

Appendix A

Reductive Transformation of 2,4-Dinitrotoluene: Roles of Iron and Natural Organic Matter

Minori Uchimiya

Environmental Laboratory,U.S. Army Engineer Research and DevelopmentCenter,Vicksburg, MS 39180

Corresponding author fax: (504) 286-4363, phone: (504) 286-4356, email: . Present address:USDA-ARS, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124

Revisedmanuscript submitted on November 18, 2009

Number of pages:8

Number of tables:3

Number of figures: 1

Appendix A. Supplementary Material

Chemicals and preparation of stock solutions, stability constants for iron, speciation diagram of Fe(II) in the presence of caffeic acid, and electron transfer capacity and carboxyl content of humic substances investigated in this study.

I.Chemicals and preparation of stock solutions

All chemical reagents were of the highest purity available and were used as received. 2,4-Dinitrotoluene, 2,4-diaminotoluene, 2-methyl-5-nitroaniline, 4-methyl-3-nitroaniline, oxalic acid, citric acid, caffeic acid, L-ascorbic acid,N-(2-Hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA), 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (tiron), ferrous chloride tetrahydrate,and goethite were purchased from Sigma-Aldrich (Milwaukee, WI). Standard Elliot soil humic acid (1S102H, ESHA), referencePahokee peat humic acid (1R103H, PPHA), and reference SuwanneeRiver naturalorganic matter (1R101N, SRNOM) were obtained from International Humic Substances Society (St. Paul,MN). In order to minimize Fe(III)contamination, Fe(II)stock solutions were prepared by acidifyingfiltered (Anatop 25-Plus inorganic 0.2 m membrane filter; Whatman Scientific, Maidstone, England) neutral FeCl2 solution with HCl for the final concentration of 1.0 M FeCl24H2O (Aldrich) in 1.0 mM HCl.

For selected experiments, dissolved Fe(II) concentration (Fe(II)dissolved) was determined using Ferrozine colorimetric method (Stookey, 1970). Ferrozine (Aldrich) stock solution (1.0 gL-1) was prepared in 50 mM MOPS buffer (pH 7.0) outside the glove box. Known volume of filtered (0.2 m Anatop) samplewas added to 5.0 mL ferrozine solution within the glove box and was analyzed for the absorbance at 562 nm (A562ferrozine) using UV-visible spectrophotometer (Shimadzu, Kyoto, Japan). Standards for spectrophotometric measurements at 562 nm were prepared daily by adding known volume of 1.0 mM FeCl2 stock solution (in 0.50 M HCl) to 5.0 mL of ferrozine solution. For selected reactions in the presence of goethite, 2.0 mL of reaction suspension was added to 5.0 mL of ferrozine solution, equilibrated for 24 hours, and then filtered (0.2 m Anatop) for analysis at 562 nm to determine total Fe(II) concentration (Fe(II)total) (Smolen et al., 2003). Sorbed Fe(II) concentration was determined as the difference of Fe(II)total and Fe(II)dissolved.

II.Stability constants for iron

Table A1. Stability constantsa for FeII and FeIII hydrolysis reactions
Equilibrium expression / log Kb
Fe2+ + H2O - H+ = FeIIOH+ / -9.397
Fe2+ + 2 H2O - 2 H+ = FeII(OH)20 / -20.494
Fe2+ + 3 H2O - 3 H+ = FeII(OH)3- / -28.494
Fe2+ + 4 H2O - 4 H+ = FeII(OH)42- / -45.988
Fe3+ + H2O - H+ = FeIIIOH2+ / -2.187
Fe3+ + 2 H2O - 2 H+ = FeIII(OH)2+ / -4.594
Fe3+ + 3 H2O - 3 H+ = FeIII(OH)30 / -13.600
Fe3+ + 4 H2O - 4 H+ = FeIII(OH)4- / -21.588
2 Fe3+ + 2 H2O - 2 H+ = FeIII2(OH)24+ / -2.854
3 Fe3+ + 4 H2O - 4 H+ = FeIII3(OH)45+ / -6.288
Solubility product constants
Fe2+ + 2 H2O - 2 H+ = FeII(OH)2(s,amorphous) / (-12.844c
Fe3+ + 3 H2O - 3 H+ = FeIII(OH)3(s,amorphous) / (-3d
aCorrected to zero ionic strength using the Davies Equation (Stumm and Morgan, 1996).

bFrom (Martell et al., 2004)

cFrom (Cornell and Schwertmann, 1996)

dFrom Stumm and Morgan, 1996

Table A2. Stability constantsa for FeII and FeIII complexes with organic ligands

Equilibrium expression / log Kb
Citric acid
H+ + L3- = HL2- / 6.396
2 H+ + L3- = H2L- / 11.157
3 H+ + L3- = H3L0 / 14.285
Fe2+ + L3- = FeIIL- / 6.086
Fe2+ + L3- + H+ = FeIIHL0 / 14.285
Fe2+ + L3- + 2 H+ = FeIIH2L+ / 12.734c
Fe2+ + 2 L3- + H+ = FeIIHL23- / 13.343c
2 Fe2+ + 2 L3- + 2 OH- = FeII2(OH)2L24- / (-4.583c
Fe3+ + L3- = FeIIIL0 / 13.129
Fe3+ + L3- + H+ = FeIIIHL+ / 14.382
Fe3+ + L3- + OH- = FeIII(OH)L / 10.214
2 Fe3+ + 2 L3- + 2 OH- = FeIII(OH)L- / 24.414d
Na+ + L3- = NaL2- / 1.393
Oxalic acid
H+ + L2- = HL- / 4.266
2 H+ + L2- = H2L0 / 5.518
Fe2+ + L2- = FeIIL0 / 3.865
Fe2+ + 2 L2- = FeIIL22- / 5.895
Fe2+ + 3 L2- = FeIIL34- / 5.220e
Fe3+ + L2- = FeIIIL+ / 8.803
Fe3+ + 2 L2- = FeIIIL2- / 15.441
Fe3+ + 3 L2- = FeIIIL33- / 19.823
Na+ + L3- = NaL2- / 0.900
EDTA
H+ + L4- = HL3- / 10.948
2 H+ + L4- = H2L2- / 17.221
3 H+ + L4- = H3L- / 20.340
4 H+ + L4- = H4L0 / 22.554
5 H+ + L4- = H5L+ / 24.054
6 H+ + L4- = H6L2+ / 23.840
Fe2+ + L4- = FeIIL2- / 16.014
Fe2+ + L4- + H+ = FeIIHL- / 19.054
Fe3+ + L4- = FeIIIL- / 27.671
Fe3+ + L4- + H+ = FeIIIHL0 / 29.186
2Fe3+ + 2L4- + 2OH- = FeIII2(OH)2L24- / 41.3
Na+ + L4- = NaL3- / 2.717
HEDTA
H+ + L3- = HL2- / 10.4
2 H+ + L3- = H2L- / 16.2
3 H+ + L3- = H3L0 / 19.02
4 H+ + L3- = H4L+ / 20.62
Fe2+ + L3- = FeIIL- / 13.5
Fe2+ + L3- + H+ = FeIIHL0 / 16.4
Fe3+ + L3- = FeIIIL0 / 21.7
Fe3+ + L3- + OH- = FeIII(OH)L- / 17.6
Fe3+ + L3- + 2 OH- = FeIII(OH)2L2- / 8.3
Fe3+ + L3- + 3 OH- = FeIII(OH)3L3- / -2.3
2 Fe3+ + 2 L3- + 2 OH- = FeIII2(OH)2L22- / 37.3
Caffeic acid
H+ + L3- = HL2- / 11.8
2 H+ + L3- = H2L- / 20.91
3 H+ + L3- = H3L0 / 25.53
Fe2+ + L3- = FeIIL- / 7.4
Fe2+ + L3- + H+ = FeIIHL0 / 14.8
Fe2+ + 2 L3- + H+ = FeIIHL23- / 23.10
Fe2+ + 3 L3- + H+ = FeIIHL36- / 29.82
2 Fe2+ + L3- + H+ = FeII2HL2+ / 17.65
Ascorbic acid
H+ + L2- = HL- / 11.8
2 H+ + L2- = H2L0 / 16.0
Fe2+ + L2- + H+ = FeIIHL+ / 12.1
Fe3+ + 2 L2- + 2 H+ = FeIII(HL)2+ / 30.9
Tiron
H+ + L4- = HL3- / 13.36
2 H+ + L4- = H2L2- / 21.62
Fe2+ + L4- = FeIIL2- / 10.63f
Fe2+ + L4- + H+ = FeIIHL- / 17.85f
Fe2+ + 2 L4- = FeIIL26- / 15.33f
Fe3+ + L4- = FeIIIL- / 22.89
Fe3+ + L4- + H+ = FeIIIHL0 / 24.91
Fe3+ + 2 L4- = FeIIIL25- / 36.95
Fe3+ + 3 L4- = FeIIIL39- / 43.28

aCorrected to zero ionic strength using the Davies Equation (Stumm and Morgan, 1996).

bFrom(Martell et al., 2004) unless otherwise noted.

cDetermined at 37oC.

dDetermined at 20 oC.

eFrom (Schaap et al., 1954).

fFrom (Naka et al., 2006).

III. Speciation diagram of Fe(II) in the presence of caffeic acid

Figure A1.Speciation diagram for 500 M Fe(II) in the presence of 5 mM caffeic acid. Concentrations of FeII(OH)2o, FeII(OH)3-, and FeII(OH)42-aretoo low to be seen.

IV. Electron transfer capacity and carboxyl content of humic substances investigated in this study

Table A3. Chemical properties of humic substance samplesa

Sampleb / Catalogue / C content / Aromatic C / (-COOHc / Chemical reducing capacityc
number / gkg-1 / % / mol COOHkg-1 / molkg-1
ESHA / 1S102H / 581 / 50 / 3.38 ± 0.29 / 0.560 ± 0.110
PPHA / 1R103H / 568 / 47 / 4.05 ± 0.35 / 0.615 ± 0.005
SRNOM / 1R101N / 525 / 23 / 4.87 ± 0.42 / 0.205 ± 0.004

aData obtained from International Humic Substances Society website ( unless otherwise noted.

bAbbreviation for standard Elliot soil humic acid (ESHA), reference Pahokee peat humic acid (PPHA), and reference SuwanneeRiver natural organic matter (SRNOM).

cFrom (Rakshit et al., 2009).

References

Stookey, L.L. (1970) Ferrozine-A New Spectrophotometric Reagent for Iron. Analytical Chemistry 42: 779 - 781.

Smolen, J.M., McLaughlin, M.A., McNevin, M.J., Haberle, A. and Swantek, S. (2003) Reductive dissolution of goethite and the subsequent transformation of 4-cyanonitrobenzene: Role of ascorbic acid and pH. Aquat Sci 65: 308-315.

Stumm, W. and Morgan, J.J. (1996) Aquatic Chemistry, Wiley-Interscience, NY.

Martell, A.E., Smith, R.M. and Motekaitis, R.J. (2004) Critically Selected Stability Constants of Metal Complexes Database, U. S. Department of Commerce, National Institute of Standards and Technology, Gaithersburg, MD.

Cornell, R.M. and Schwertmann, U. (1996) The Iron Oxides: Structure, Properties, Reactions, Occurrence and Uses, VCH Publishers, Weinheim.

Schaap, W.B., Laitinen, H.A. and Bailar, J.C. (1954) Polarography of Iron Oxalates, Malonates and Succinates. Journal of the American Chemical Society 76: 5868-5872.

Naka, D., Kim, D. and Strathmann, T.J. (2006) Abiotic reduction of nitroaromatic compounds by aqueous iron(II) - Catechol complexes. Environ. Sci. Technol. 40: 3006-3012.

Rakshit, S., Uchimiya, M. and Sposito, G. (2009) Iron(III) bioreduction in soil in the presence of added humic substances. Soil Sci. Soc. Am. J. 73: 65-71.

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