Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches
RESEARCH ARTICLE

Modelling proton and metal binding to humic substances with the NICA–EPN model

Andrea C. Montenegro A , Silvia Orsetti B and Fernando V. Molina A C

A Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE) and Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, C1428EGA, Argentina.

B Present address: Institut für Geowissenschaften, Zentrum für angewandte Geowissenschaften, Eberhard-Karls Universität Tübingen, D-72074 Tübingen, Germany.

C Corresponding author. E-mail: fmolina@qi.fcen.uba.ar

Environmental Chemistry 11(3) 318-332 http://dx.doi.org/10.1071/EN13214
Submitted: 26 November 2013  Accepted: 7 March 2014   Published: 10 June 2014

Environmental context. The toxicity of metals in the environment is greatly influenced by natural organic matter owing to its ability to bind metals to form complexes that can be immobile and non-bioavailable. Sound mathematical models are important to reliably predict the behaviour of such contaminants, and how they are affected by organic matter and other environmental colloids. Here a new model is discussed and compared with precedent ones.

Abstract. The mathematical modelling of metal cation–natural organic matter interactions is a fundamental tool in predicting the state and fate of pollutants in the environment. In this work, the binding of protons and metal cations to humic substances is modelled applying the Elastic Polyelectrolyte Network (EPN) electrostatic model with the Non-Ideal Competitive Adsorption (NICA) isotherm as the intrinsic part (NICA–EPN model). Literature data of proton and metal binding to humic substances at different pH and ionic strength values are analysed, discussing in depth the model predictions. The NICA–EPN model is found to describe well these phenomena. The electrostatic contribution to the Gibbs free energy of adsorbate–humic interaction in the EPN model is lower than that predicted by the Donnan phase model; the intrinsic mean binding constants for protons and metal cations are generally higher, closer to independent estimations and to the range of acid–base and complexation equilibrium values for common carboxylic acids. The results for metal cations are consistent with recent literature findings. The model predicts shrinking of the humic particles with increased metal binding, as a consequence of net charge decrease.


References

[1]  J. Ephraim, S. Alegret, A. Mathuthu, M. Bicking, R. L. Malcolm, J. A. Marinsky, A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 2. Influence of polyelectrolyte properties and functional group heterogeneity on the protonation equilibria of fulvic acid. Environ. Sci. Technol. 1986, 20, 354.
A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 2. Influence of polyelectrolyte properties and functional group heterogeneity on the protonation equilibria of fulvic acid.CrossRef | 1:CAS:528:DyaL28Xht1yrur8%3D&md5=a8e97adb3a62b54d789a57662f0d2296CAS | 22300206PubMed | open url image1

[2]  N. Senesi, E. Loffredo, Metal ion complexation by humic substances, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 563–617 (Soil Science Society of America: Madison, WI).

[3]  S. Sen Gupta, K. G. Bhattacharyya, Kinetics of adsorption of metal ions on inorganic materials: a review. Adv. Colloid Interface Sci. 2011, 162, 39.
Kinetics of adsorption of metal ions on inorganic materials: a review.CrossRef | 1:CAS:528:DC%2BC3MXitFaks70%3D&md5=8f3fb64868c600e6a9e352d35c8dcf15CAS | 21272842PubMed | open url image1

[4]  C. E. Clapp, M. H. B. Hayes, A. J. Simpson, W. L. Kingery, Chemistry of soil organic matter, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 1–150 (Soil Science Society of America: Madison, WI).

[5]  J. A. Baldock, P. N. Nelson, Soil organic matter, in Handbook of Soil Science (Ed. M. L. Sumner) 1999, pp. B75–B84 (CRC: Boca Raton, Fl).

[6]  Á. Zsolnay, Dissolved organic matter: artefacts, definitions, and functions. Geoderma 2003, 113, 187.
Dissolved organic matter: artefacts, definitions, and functions.CrossRef | 1:CAS:528:DC%2BD3sXhsF2nsL0%3D&md5=c952bfa81692041c8e230994bb2a3b76CAS | open url image1

[7]  S. Orsetti, E. M. Andrade, F. V. Molina, Application of a constrained regularization method to extraction of affinity distributions: proton and metal binding to humic substances. J. Colloid Interface Sci. 2009, 336, 377.
Application of a constrained regularization method to extraction of affinity distributions: proton and metal binding to humic substances.CrossRef | 1:CAS:528:DC%2BD1MXnslKntbs%3D&md5=7fe5722ead4e114e42c4548f0f41cc30CAS | 19477457PubMed | open url image1

[8]  A. J. Simpson, W. L. Kingery, M. H. Hayes, M. Spraul, E. Humpfer, P. Dvortsak, R. Kerssebaum, M. Godejohann, M. Hofmann, Molecular structures and associations of humic substances in the terrestrial environment. Naturwissenschaften 2002, 89, 84.
Molecular structures and associations of humic substances in the terrestrial environment.CrossRef | 1:CAS:528:DC%2BD38XivVaktbk%3D&md5=dc05875da76678045e5a885efb908ad2CAS | 12046627PubMed | open url image1

[9]  M. Hosse, K. J. Wilkinson, Determination of electrophoretic mobilities and hydrodynamic radii of three humic substances as a function of pH and ionic strength. Environ. Sci. Technol. 2001, 35, 4301.
Determination of electrophoretic mobilities and hydrodynamic radii of three humic substances as a function of pH and ionic strength.CrossRef | 1:CAS:528:DC%2BD3MXnt12qu7g%3D&md5=40508adb77c49037fa127261a6b7cc36CAS | 11718346PubMed | open url image1

[10]  J. F. L. Duval, K. J. Wilkinson, H. P. Van Leeuwen, J. Buffle, Humic substances are soft and permeable: evidence from their electrophoretic mobilities. Environ. Sci. Technol. 2005, 39, 6435.
Humic substances are soft and permeable: evidence from their electrophoretic mobilities.CrossRef | 1:CAS:528:DC%2BD2MXjvFKjs70%3D&md5=0cb37785d6eacf43bdf7ffc36464e935CAS | open url image1

[11]  J. Buffle, R. S. Altmann, M. Filella, A. Tessier, Complexation by natural heterogeneous compounds: site occupation distribution functions, a normalized description of metal complexation. Geochim. Cosmochim. Acta 1990, 54, 1535.
Complexation by natural heterogeneous compounds: site occupation distribution functions, a normalized description of metal complexation.CrossRef | 1:CAS:528:DyaK3cXltlWit7k%3D&md5=fff2db5feab66509a41d676066f27678CAS | open url image1

[12]  E. Tipping, Humic Ion-Binding Model VI: an improved description of the interactions of protons and metal ions with humic substances. Aquat. Geochem. 1998, 4, 3.
Humic Ion-Binding Model VI: an improved description of the interactions of protons and metal ions with humic substances.CrossRef | 1:CAS:528:DyaK1cXntlSjuro%3D&md5=5713777c9b890be10b9003a0b7744eadCAS | open url image1

[13]  J. P. Gustafsson, P. Pechova, D. Berggren, Modeling metal binding to soils: the role of natural organic matter. Environ. Sci. Technol. 2003, 37, 2767.
Modeling metal binding to soils: the role of natural organic matter.CrossRef | 1:CAS:528:DC%2BD3sXjsleisbw%3D&md5=b708dbd7eef51eea8e669cece1b1071bCAS | 12854717PubMed | open url image1

[14]  S. Goldberg, Equations and models describing adsorption processes in soils, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 489–518 (Soil Science Society of America: Madison, WI).

[15]  F. V. Molina, Soil Colloids: Properties and Ion Binding 2013 (CRC Press: Boca Raton, FL).

[16]  E. Tipping, S. Lofts, J. E. Sonke, Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances. Environ. Chem. 2011, 8, 225.
Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances.CrossRef | 1:CAS:528:DC%2BC3MXptVWrsL0%3D&md5=aa4916d59483661845fa4dc20916cb11CAS | open url image1

[17]  D. G. Kinniburgh, C. J. Milne, M. F. Benedetti, J. P. Pinheiro, J. Filius, L. K. Koopal, W. H. Van Riemsdijk, Metal ion binding by humic acid: application of the NICA–Donnan model. Environ. Sci. Technol. 1996, 30, 1687.
Metal ion binding by humic acid: application of the NICA–Donnan model.CrossRef | 1:CAS:528:DyaK28XhvVKgtL4%3D&md5=536da0cbf5b4a863361015222378d00eCAS | open url image1

[18]  M. F. Benedetti, W. H. Van Riemsdijk, L. K. Koopal, Humic substances considered as a heterogeneous Donnan gel phase. Environ. Sci. Technol. 1996, 30, 1805.
Humic substances considered as a heterogeneous Donnan gel phase.CrossRef | 1:CAS:528:DyaK28XisFans7Y%3D&md5=40c3e7e762ab48271f3874128ecb1828CAS | open url image1

[19]  C. J. Milne, D. G. Kinniburgh, W. H. van Riemsdijk, E. Tipping, Generic NICA–Donnan model parameters for metal-ion binding by humic substances. Environ. Sci. Technol. 2003, 37, 958.
Generic NICA–Donnan model parameters for metal-ion binding by humic substances.CrossRef | 1:CAS:528:DC%2BD3sXosVWgsQ%3D%3D&md5=cf83eea77d60eafc37b6d7ddffabaf09CAS | 12666927PubMed | open url image1

[20]  J. B. Christensen, E. Tipping, D. G. Kinniburgh, C. Grøn, T. H. Christensen, Proton binding by groundwater fulvic acids of different age, origins, and structure modeled with the model V and NICA–Donnan model. Environ. Sci. Technol. 1998, 32, 3346.
Proton binding by groundwater fulvic acids of different age, origins, and structure modeled with the model V and NICA–Donnan model.CrossRef | 1:CAS:528:DyaK1cXlvFKmu7g%3D&md5=0935c34cf8c7a4237070307c307d3de8CAS | open url image1

[21]  M. J. Avena, A. W. P. Vermeer, L. K. Koopal, Volume and structure of humic acids studied by viscometry pH and electrolyte concentration effects. Colloids Surf. A Physicochem. Eng. Asp. 1999, 151, 213.
Volume and structure of humic acids studied by viscometry pH and electrolyte concentration effects.CrossRef | 1:CAS:528:DyaK1MXhvV2nsL8%3D&md5=5be201b79c65ab831f50adc9a544bf9dCAS | open url image1

[22]  G. Chilom, J. A. Rice, Structural organization of humic acid in the solid state. Langmuir 2009, 25, 9012.
Structural organization of humic acid in the solid state.CrossRef | 1:CAS:528:DC%2BD1MXlt1GqsrY%3D&md5=c1bcf6a99dbbc2f3cab5cf02fef36011CAS | 19408899PubMed | open url image1

[23]  S. Orsetti, E. M. Andrade, F. V. Molina, Modeling ion binding to humic substances: Elastic Polyelectrolyte Network model. Langmuir 2010, 26, 3134.
Modeling ion binding to humic substances: Elastic Polyelectrolyte Network model.CrossRef | 1:CAS:528:DC%2BC3cXhvVKgsw%3D%3D&md5=4034ddc64958edf073a44b8af0d64cb6CAS | 20055366PubMed | open url image1

[24]  S. Orsetti, J. L. Marco-Brown, E. M. Andrade, F. V. Molina, PbII binding to humic substances: an equilibrium and spectroscopic study. Environ. Sci. Technol. 2013, 47, 8325.
| 1:CAS:528:DC%2BC3sXhtVWhtL7J&md5=174b568105dab964c4678912e130a5b5CAS | 23805795PubMed | open url image1

[25]  T. L. Hill, Some statistical mechanical models of elastic polyelectrolytes and proteins. J. Chem. Phys. 1952, 20, 1259.
Some statistical mechanical models of elastic polyelectrolytes and proteins.CrossRef | 1:CAS:528:DyaG3sXlslCntQ%3D%3D&md5=3c45d41cb676f06c34e3f036c3872cfeCAS | open url image1

[26]  E. Dinar, T. F. Mentel, Y. Rudich, The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles. Atmos. Chem. Phys. 2006, 6, 5213.
The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles.CrossRef | 1:CAS:528:DC%2BD2sXht1eitrc%3D&md5=1689ab35e13ad84ad49011d77940db16CAS | open url image1

[27]  C. J. Milne, D. G. Kinniburgh, E. Tipping, Generic NICA–Donnan model parameters for proton binding by humic substances. Environ. Sci. Technol. 2001, 35, 2049.
Generic NICA–Donnan model parameters for proton binding by humic substances.CrossRef | 1:CAS:528:DC%2BD3MXis1GrsLY%3D&md5=58397a135dc43f51409b0d76c10d44e2CAS | 11393987PubMed | open url image1

[28]  A. Matynia, T. Lenoir, B. Causse, L. Spadini, T. Jacquet, A. Manceau, Semi-empirical proton binding constants for natural organic matter. Geochim. Cosmochim. Acta 2010, 74, 1836.
Semi-empirical proton binding constants for natural organic matter.CrossRef | 1:CAS:528:DC%2BC3cXhvFalurw%3D&md5=544abb97b995be8ebb628cf678535ddcCAS | open url image1

[29]  P. J. Flory, Themodynamics of high polymer solutions. J. Chem. Phys. 1942, 10, 51.
Themodynamics of high polymer solutions.CrossRef | 1:CAS:528:DyaH38Xns1Gk&md5=376b185f0eb6adaaceb38c842e84fde4CAS | open url image1

[30]  P. J. Flory, Statistical mechanics of swelling of network structures. J. Chem. Phys. 1950, 18, 108.
Statistical mechanics of swelling of network structures.CrossRef | 1:CAS:528:DyaG3cXivFanuw%3D%3D&md5=6e5360c8ca0de19c160d2374c170bc23CAS | open url image1

[31]  D. G. Kinniburgh, W. H. Van Riemsdijk, L. K. Koopal, M. Borkovec, M. F. Benedetti, M. J. Avena, Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency. Colloids Surf. A Physicochem. Eng. Asp. 1999, 151, 147.
Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency.CrossRef | 1:CAS:528:DyaK1MXhvV2ns7g%3D&md5=64109cfc9410b76e41a4b38ad41bba0bCAS | open url image1

[32]  B. Pernet-Coudrier, E. Companys, J. Galceran, M. Morey, J.-M. Mouchel, J. Puy, N. Ruiz, G. Varrault, Pb-binding to various dissolved organic matter in urban aquatic systems: key role of the most hydrophilic fraction. Geochim. Cosmochim. Acta 2011, 75, 4005.
Pb-binding to various dissolved organic matter in urban aquatic systems: key role of the most hydrophilic fraction.CrossRef | 1:CAS:528:DC%2BC3MXns1Cnu78%3D&md5=11ceb7b507bc6418866cb43614000b02CAS | open url image1

[33]  E. Companys, J. Puy, J. Galceran, Humic acid complexation to Zn and Cd determined with the new electroanalytical technique AGNES. Environ. Chem. 2007, 4, 347.
| 1:CAS:528:DC%2BD2sXht1yiu7jK&md5=b7532dde9dda0c7cd9f185cc491192d2CAS | open url image1

[34]  I. Christl, Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids. Environ. Chem. 2012, 9, 89.
Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids.CrossRef | 1:CAS:528:DC%2BC38Xis1amtLc%3D&md5=679a8b042796877c66ac6fbf7b2b3318CAS | open url image1

[35]  C. W. Davies, Ion Association 1962 (Butterworths: London).

[36]  M. I. A. Lourakis, Levmar: Levenberg-Marquardt Nonlinear Least Squares Algorithms in C/C++ 2004 (Institute of Computer Science, FORTH: Heraklion, Crete, Greece).

[37]  J. P. Gustafsson, Visual Minteq. 2011 (KTH, Department of Land and Water Resources Engineering.: Stockholm, Sweden).

[38]  V. T. Athavale, L. H. Prabhu, D. G. Vartak, Solution stability constants of some metal complexes of derivatives of catechol. J. Inorg. Nucl. Chem. 1966, 28, 1237.
Solution stability constants of some metal complexes of derivatives of catechol.CrossRef | 1:CAS:528:DyaF28XktVSmtLo%3D&md5=eb6c7a0c6dac72e839713ee8e778146cCAS | open url image1

[39]  E. Furia, R. Porto, The hydrogen salicylate ion as ligand. complex formation equilibria with dioxouranium(VI), neodymium(III) and lead(II). Ann. Chim. 2004, 94, 795.
The hydrogen salicylate ion as ligand. complex formation equilibria with dioxouranium(VI), neodymium(III) and lead(II).CrossRef | 1:CAS:528:DC%2BD2cXhtVOmtLrN&md5=e7d869e4ba8df9f4544deafef3f5fcb5CAS | 15626240PubMed | open url image1

[40]  J. P. Gustafsson, Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model. J. Colloid Interface Sci. 2001, 244, 102.
Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model.CrossRef | 1:CAS:528:DC%2BD3MXot1KisLw%3D&md5=c17d1ca37696e340e9ed673f5af5ff1aCAS | open url image1

[41]  T. Lenoir, A. Matynia, A. Manceau, Convergence-optimized procedure for applying the NICA–Donnan model to potentiometric titrations of humic substances. Environ. Sci. Technol. 2010, 44, 6221.
Convergence-optimized procedure for applying the NICA–Donnan model to potentiometric titrations of humic substances.CrossRef | 1:CAS:528:DC%2BC3cXptVygsLo%3D&md5=290339532ffe81884336436adb34ca52CAS | 20704219PubMed | open url image1

[42]  M. J. Avena, L. K. Koopal, W. H. van Riemsdijk, Proton binding to humic acids: electrostatic and intrinsic interactions. J. Colloid Interface Sci. 1999, 217, 37.
Proton binding to humic acids: electrostatic and intrinsic interactions.CrossRef | 1:CAS:528:DyaK1MXltVaht7s%3D&md5=805840c7699fb7b6a74ad2a1a803aa06CAS | 10441409PubMed | open url image1

[43]  M. B. Hay, S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1. Infrared spectroscopy. Geochim. Cosmochim. Acta 2007, 71, 3518.
Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1. Infrared spectroscopy.CrossRef | 1:CAS:528:DC%2BD2sXnsVSrtb0%3D&md5=33c58391377dd11b0910b285b49d78b8CAS | open url image1

[44]  Y. B. Atalay, R. F. Carbonaro, D. M. Di Toro, Distribution of proton dissociation constants for model humic and fulvic acid molecules. Environ. Sci. Technol. 2009, 43, 3626.
Distribution of proton dissociation constants for model humic and fulvic acid molecules.CrossRef | 1:CAS:528:DC%2BD1MXkslaktbg%3D&md5=66ec3bf3159709781287591afaffda51CAS | 19544864PubMed | open url image1

[45]  A. P. Deshmukh, C. Pacheco, M. B. Hay, S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2-D NMR spectroscopy. Geochim. Cosmochim. Acta 2007, 71, 3533.
Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2-D NMR spectroscopy.CrossRef | 1:CAS:528:DC%2BD2sXnsVSrtbo%3D&md5=7dd02d58103baf9c3c681f92f299d577CAS | open url image1

[46]  A. Kirishima, T. Ohnishi, N. Sato, O. Tochiyama, Determination of the phenolic-group capacities of humic substances by non-aqueous titration technique. Talanta 2009, 79, 446.
Determination of the phenolic-group capacities of humic substances by non-aqueous titration technique.CrossRef | 1:CAS:528:DC%2BD1MXnvVClsbk%3D&md5=ccb71d0df2d54aec114f783bb34b6f2dCAS | 19559903PubMed | open url image1

[47]  N. Senesi, E. Loffredo, The chemistry of soil organic matter, in Soil Physical Chemistry (Ed. D. L. Sparks) 1998, pp. 239–370 (CRC Press: Boca Raton, Fl).

[48]  J. P. Pinheiro, A. M. Mota, M. F. Benedetti, Effect of aluminum competition on lead and cadmium binding to humic acids at variable ionic strength. Environ. Sci. Technol. 2000, 34, 5137.
Effect of aluminum competition on lead and cadmium binding to humic acids at variable ionic strength.CrossRef | 1:CAS:528:DC%2BD3cXnvFartb4%3D&md5=9c4ee02c45eb9ab86b97b1133fcfeb9cCAS | open url image1

[49]  W. H. Otto, S. D. Burton, W. Robert Carper, C. K. Larive, Examination of cadmium(II) complexation by the Suwannee River fulvic acid using 113Cd NMR relaxation measurements. Environ. Sci. Technol. 2001, 35, 4900.
Examination of cadmium(II) complexation by the Suwannee River fulvic acid using 113Cd NMR relaxation measurements.CrossRef | 1:CAS:528:DC%2BD3MXotlWiu7Y%3D&md5=dd937ace77221ef88bfdccff7723e606CAS | 11775168PubMed | open url image1

[50]  K. Xia, W. Bleam, P. A. Helmke, Studies of the nature of Cu2+ and Pb2+ binding sites in soil humic substances using X-ray absorption spectroscopy. Geochim. Cosmochim. Acta 1997, 61, 2211.
Studies of the nature of Cu2+ and Pb2+ binding sites in soil humic substances using X-ray absorption spectroscopy.CrossRef | 1:CAS:528:DyaK2sXjvFSksbY%3D&md5=1e1abd844664e446f0e1da1ec4d5982cCAS | open url image1

[51]  A. Terbouche, C. A. Ramdane-Terbouche, D. Hauchard, S. Djebbar, Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as CdII, ZnII and NiII and characterization with cavity microelectrode. J. Environ. Sci. (China) 2011, 23, 1095.
Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as CdII, ZnII and NiII and characterization with cavity microelectrode.CrossRef | 1:CAS:528:DC%2BC3MXhtVyru7nP&md5=2607418634cd3d976c48931b41a6531dCAS | 22125901PubMed | open url image1

[52]  T. Karlsson, P. Persson, U. Skyllberg, Complexation of copper(II) in organic soils and in dissolved organic matter – EXAFS evidence for chelate ring structures. Environ. Sci. Technol. 2006, 40, 2623.
Complexation of copper(II) in organic soils and in dissolved organic matter – EXAFS evidence for chelate ring structures.CrossRef | 1:CAS:528:DC%2BD28XisFWjt78%3D&md5=cb5938cb982c4e71c50f0dfa8dffe0e3CAS | 16683601PubMed | open url image1

[53]  J. Xiong, L. K. Koopal, W. Tan, L. Fang, M. Wang, W. Zhao, F. Liu, J. Zhang, L. P. Weng, Lead binding to soil fulvic and humic acids: NICA–Donnan modeling and XAFS spectroscopy. Environ. Sci. Technol. 2013, 47, 11634.
Lead binding to soil fulvic and humic acids: NICA–Donnan modeling and XAFS spectroscopy.CrossRef | 1:CAS:528:DC%2BC3sXhsVCmu7rP&md5=783f9a974f3f63820d3502dbf8eef7bbCAS | 24040886PubMed | open url image1

[54]  J. Puy, J. Galceran, C. Huidobro, E. Companys, N. Samper, J. L. Garcés, F. Mas, Conditional affinity spectra of Pb2+–humic acid complexation from data obtained with AGNES. Environ. Sci. Technol. 2008, 42, 9289.
Conditional affinity spectra of Pb2+–humic acid complexation from data obtained with AGNES.CrossRef | 1:CAS:528:DC%2BD1cXhtlKqtLjI&md5=fa913aefacf5cf7cdbac233317dc8a98CAS | 19174906PubMed | open url image1

[55]  A. Manceau, M.-C. Boisset, G. Sarret, J.-L. Hazemann, M. Mench, P. Cambier, R. Prost, Direct determination of lead speciation in contaminated soils by EXAFS spectroscopy. Environ. Sci. Technol. 1996, 30, 1540.
Direct determination of lead speciation in contaminated soils by EXAFS spectroscopy.CrossRef | 1:CAS:528:DyaK28XhvVKgt70%3D&md5=b729fe61c1c989e1633c56e70b4bc711CAS | open url image1

[56]  Y. Arai, A. R. Rick, T. Saylor, E. Faas, R. Tappero, A. Lanzirotti, Macroscopic and molecular-scale assessment of soil lead contamination impacted by seasonal dove hunting activities. J. Soils Sediments 2011, 11, 968.
Macroscopic and molecular-scale assessment of soil lead contamination impacted by seasonal dove hunting activities.CrossRef | 1:CAS:528:DC%2BC3MXhtVegtLnL&md5=5b7c16d811b40a346b2f16f8f5acc919CAS | open url image1

[57]  A. P. Robertson, Goethite/Humic Acid Interactions and their Effects on Copper(II) Binding 1996, Ph.D. Thesis, Stanford University, Stanford, CA.

[58]  P. H. Hsu, T. F. Bates, Formation of X-ray amorphous and crystalline aluminium hydroxides. Mineral. Mag. 1964, 33, 749.
Formation of X-ray amorphous and crystalline aluminium hydroxides.CrossRef | 1:CAS:528:DyaF2cXovFCqsg%3D%3D&md5=c17c006d6a80cc20d5162f8cbc56d944CAS | open url image1

[59]  B. Stolpe, L. Guo, A. M. Shiller, G. R. Aiken, Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS. Geochim. Cosmochim. Acta 2013, 105, 221.
Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS.CrossRef | 1:CAS:528:DC%2BC3sXivVKht70%3D&md5=e632ec4c6aeaba479a1f7014799f140eCAS | open url image1

[60]  W. Tan, J. Xiong, Y. Li, M. Wang, L. Weng, L. K. Koopal, Proton binding to soil humic and fulvic acids: experiments and NICA–Donnan modeling. Colloids Surf. A Physicochem. Eng. Asp. 2013, 436, 1152.
Proton binding to soil humic and fulvic acids: experiments and NICA–Donnan modeling.CrossRef | 1:CAS:528:DC%2BC3sXhs1SgurvE&md5=8a38ecac940586ceaacb5083104e6f86CAS | open url image1

[61]  B. A. Browne, C. T. Driscoll, pH-dependent binding of aluminum by a fulvic acid. Environ. Sci. Technol. 1993, 27, 915.
pH-dependent binding of aluminum by a fulvic acid.CrossRef | 1:CAS:528:DyaK3sXitF2isLw%3D&md5=211c56e8eb0532dfeac4d039149c6dcaCAS | open url image1

[62]  J. P. Pinheiro, A. M. Mota, M. F. Benedetti, Lead and calcium binding to fulvic acids: salt effect and competition. Environ. Sci. Technol. 1999, 33, 3398.
Lead and calcium binding to fulvic acids: salt effect and competition.CrossRef | 1:CAS:528:DyaK1MXlsVKltbw%3D&md5=ee52e3c8c86553c2b0cab6f7a2b1095eCAS | open url image1

[63]  S. E. Cabaniss, M. S. Shuman, Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria. Geochim. Cosmochim. Acta 1988, 52, 185.
Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria.CrossRef | 1:CAS:528:DyaL1cXhtFynt7k%3D&md5=3bf69580bdaf055496cb0e95420dc1ceCAS | open url image1

[64]  I. Christl, C. J. Milne, D. G. Kinniburgh, R. Kretzschmar, Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 2. Metal binding. Environ. Sci. Technol. 2001, 35, 2512.
Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 2. Metal binding.CrossRef | 1:CAS:528:DC%2BD3MXjtlClu7k%3D&md5=bc7797612767288484158c03379edf18CAS | 11432556PubMed | open url image1

[65]  M. F. Benedetti, C. J. Milne, D. G. Kinniburgh, W. H. Van Riemsdijk, L. K. Koopal, Metal ion binding to humic substances: application of the non-ideal competitive adsorption model. Environ. Sci. Technol. 1995, 29, 446.
Metal ion binding to humic substances: application of the non-ideal competitive adsorption model.CrossRef | 1:CAS:528:DyaK2MXivFOrs7s%3D&md5=cafbac173ab674054df7988e10560390CAS | 22201392PubMed | open url image1

[66]  A. M. Mota, A. Rato, C. Brazia, M. L. S. Gonçalves, Competition of Al3+ in complexation of humic matter with Pb2+: a comparative study with other ions. Environ. Sci. Technol. 1996, 30, 1970.
Competition of Al3+ in complexation of humic matter with Pb2+: a comparative study with other ions.CrossRef | 1:CAS:528:DyaK28XisFansLk%3D&md5=5cf257ab64267bfdd25bbc7b1c3609a9CAS | open url image1

[67]  C. Plaza, N. Senesi, A. Polo, G. Brunetti, Acid-base properties of humic and fulvic acids formed during composting. Environ. Sci. Technol. 2005, 39, 7141.
Acid-base properties of humic and fulvic acids formed during composting.CrossRef | 1:CAS:528:DC%2BD2MXntVeru7c%3D&md5=0ab8e38fd6072c9b84ea7ed62cc25ee7CAS | 16201640PubMed | open url image1

[68]  J. D. Ritchie, E. M. Perdue, Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter. Geochim. Cosmochim. Acta 2003, 67, 85.
Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter.CrossRef | 1:CAS:528:DC%2BD38XpsV2ktLY%3D&md5=b5fe89388154abbf87a8f70eb13e1886CAS | open url image1



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