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Hongxiao Tang - One of the best experts on this subject based on the ideXlab platform.
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Complexations in Illite-fulvic acid-Cu2+ systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous Illite surfaces and the complexation of heavy metal copper(II) in Illite-FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2-FA and montmorillonite-FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in Illite-FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA-Cu2+ and Illite-Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various Illite-FA-Cu2+ systems.
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Complexations in Illite-fulvic acid- Cu(II) Systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:Abstract�As part of an extended project to illustrate how heavy metals are complexed by natural\naquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqu-\neous Illite surfaces and the complexation of heavy metal copper(II) in Illite�FA bi-complexant systems.\nBy analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of\nFA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2�\nFA and montmorillonite�FA systems described by other researchers, (ii) it is possible to e?ectively\nsimulate the complexation of Cu2+ ions in Illite�FA bi-complexant systems by taking it to be an addi-\ntive complexation of two mono-complexant systems (FA�Cu2+ and Illite�Cu2+) and (iii) FA can inhi-\nbit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The\nabove results and conclusions are supported by FT-IR analysis of various Illite�FA�Cu2+ systems.
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Adsorption of copper at aqueous Illite surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Hongxiao TangAbstract:In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in Illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous Illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free Illite suspensions can be explained by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, and a multinuclear surface complex, =SOCu2(OH)(+)(2), followed by the formation of a bulk precipitate, Cu(OH)(2)(s), or a surface precipitate, =SOCu2(OH)(3)(sp). For the Illite suspensions containing carbonates, we propose that the copper-Illite interaction can be depicted by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu-2(OH)(2)CO3(s), rather than a copper hydroxide precipitate. The existence of Cu-2(OH)(2)CO3(s) in the carbonate-containing Illite suspensions was identified by FT-IR analysis. (C) 1997 Academic Press.
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Acid – Base Properties of Aqueous Illite Surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid�base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site�one pKamodel, ?SOH ? ?SO?+ H+, pKaint= 4.12�4.23; (2) two sites�two pKas model, ?SIOH ? ?SIO?+ H+, pKintaI= 4.17�4.44, and ?SIIOH ? ?SIIO?+ H+, [dipKintaII= 6.35�7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site�one pKamodel can be considered as a simplification of the two sites�two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
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Acid-Base Properties of Aqueous Illite Surfaces
Journal of colloid and interface science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid-base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
Qing Du - One of the best experts on this subject based on the ideXlab platform.
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Complexations in Illite-fulvic acid-Cu2+ systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous Illite surfaces and the complexation of heavy metal copper(II) in Illite-FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2-FA and montmorillonite-FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in Illite-FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA-Cu2+ and Illite-Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various Illite-FA-Cu2+ systems.
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Complexations in Illite-fulvic acid- Cu(II) Systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:Abstract�As part of an extended project to illustrate how heavy metals are complexed by natural\naquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqu-\neous Illite surfaces and the complexation of heavy metal copper(II) in Illite�FA bi-complexant systems.\nBy analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of\nFA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2�\nFA and montmorillonite�FA systems described by other researchers, (ii) it is possible to e?ectively\nsimulate the complexation of Cu2+ ions in Illite�FA bi-complexant systems by taking it to be an addi-\ntive complexation of two mono-complexant systems (FA�Cu2+ and Illite�Cu2+) and (iii) FA can inhi-\nbit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The\nabove results and conclusions are supported by FT-IR analysis of various Illite�FA�Cu2+ systems.
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Adsorption of copper at aqueous Illite surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Hongxiao TangAbstract:In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in Illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous Illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free Illite suspensions can be explained by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, and a multinuclear surface complex, =SOCu2(OH)(+)(2), followed by the formation of a bulk precipitate, Cu(OH)(2)(s), or a surface precipitate, =SOCu2(OH)(3)(sp). For the Illite suspensions containing carbonates, we propose that the copper-Illite interaction can be depicted by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu-2(OH)(2)CO3(s), rather than a copper hydroxide precipitate. The existence of Cu-2(OH)(2)CO3(s) in the carbonate-containing Illite suspensions was identified by FT-IR analysis. (C) 1997 Academic Press.
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Acid – Base Properties of Aqueous Illite Surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid�base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site�one pKamodel, ?SOH ? ?SO?+ H+, pKaint= 4.12�4.23; (2) two sites�two pKas model, ?SIOH ? ?SIO?+ H+, pKintaI= 4.17�4.44, and ?SIIOH ? ?SIIO?+ H+, [dipKintaII= 6.35�7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site�one pKamodel can be considered as a simplification of the two sites�two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
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Acid-Base Properties of Aqueous Illite Surfaces
Journal of colloid and interface science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid-base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
Z. J. Sun - One of the best experts on this subject based on the ideXlab platform.
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Complexations in Illite-fulvic acid-Cu2+ systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous Illite surfaces and the complexation of heavy metal copper(II) in Illite-FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2-FA and montmorillonite-FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in Illite-FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA-Cu2+ and Illite-Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various Illite-FA-Cu2+ systems.
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Complexations in Illite-fulvic acid- Cu(II) Systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:Abstract�As part of an extended project to illustrate how heavy metals are complexed by natural\naquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqu-\neous Illite surfaces and the complexation of heavy metal copper(II) in Illite�FA bi-complexant systems.\nBy analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of\nFA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2�\nFA and montmorillonite�FA systems described by other researchers, (ii) it is possible to e?ectively\nsimulate the complexation of Cu2+ ions in Illite�FA bi-complexant systems by taking it to be an addi-\ntive complexation of two mono-complexant systems (FA�Cu2+ and Illite�Cu2+) and (iii) FA can inhi-\nbit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The\nabove results and conclusions are supported by FT-IR analysis of various Illite�FA�Cu2+ systems.
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Acid – Base Properties of Aqueous Illite Surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid�base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site�one pKamodel, ?SOH ? ?SO?+ H+, pKaint= 4.12�4.23; (2) two sites�two pKas model, ?SIOH ? ?SIO?+ H+, pKintaI= 4.17�4.44, and ?SIIOH ? ?SIIO?+ H+, [dipKintaII= 6.35�7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site�one pKamodel can be considered as a simplification of the two sites�two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
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Acid-Base Properties of Aqueous Illite Surfaces
Journal of colloid and interface science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid-base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
Willis Forsling - One of the best experts on this subject based on the ideXlab platform.
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Complexations in Illite-fulvic acid-Cu2+ systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous Illite surfaces and the complexation of heavy metal copper(II) in Illite-FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2-FA and montmorillonite-FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in Illite-FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA-Cu2+ and Illite-Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various Illite-FA-Cu2+ systems.
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Complexations in Illite-fulvic acid- Cu(II) Systems
Water Research, 1999Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:Abstract�As part of an extended project to illustrate how heavy metals are complexed by natural\naquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqu-\neous Illite surfaces and the complexation of heavy metal copper(II) in Illite�FA bi-complexant systems.\nBy analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of\nFA by Illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2�\nFA and montmorillonite�FA systems described by other researchers, (ii) it is possible to e?ectively\nsimulate the complexation of Cu2+ ions in Illite�FA bi-complexant systems by taking it to be an addi-\ntive complexation of two mono-complexant systems (FA�Cu2+ and Illite�Cu2+) and (iii) FA can inhi-\nbit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The\nabove results and conclusions are supported by FT-IR analysis of various Illite�FA�Cu2+ systems.
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Adsorption of copper at aqueous Illite surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Hongxiao TangAbstract:In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in Illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous Illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free Illite suspensions can be explained by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, and a multinuclear surface complex, =SOCu2(OH)(+)(2), followed by the formation of a bulk precipitate, Cu(OH)(2)(s), or a surface precipitate, =SOCu2(OH)(3)(sp). For the Illite suspensions containing carbonates, we propose that the copper-Illite interaction can be depicted by the formation of mononuclear surface complexes, =SOCu+ and =SOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu-2(OH)(2)CO3(s), rather than a copper hydroxide precipitate. The existence of Cu-2(OH)(2)CO3(s) in the carbonate-containing Illite suspensions was identified by FT-IR analysis. (C) 1997 Academic Press.
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Acid – Base Properties of Aqueous Illite Surfaces
Journal of Colloid and Interface Science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid�base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site�one pKamodel, ?SOH ? ?SO?+ H+, pKaint= 4.12�4.23; (2) two sites�two pKas model, ?SIOH ? ?SIO?+ H+, pKintaI= 4.17�4.44, and ?SIIOH ? ?SIIO?+ H+, [dipKintaII= 6.35�7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site�one pKamodel can be considered as a simplification of the two sites�two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
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Acid-Base Properties of Aqueous Illite Surfaces
Journal of colloid and interface science, 1997Co-Authors: Qing Du, Willis Forsling, Z. J. Sun, Hongxiao TangAbstract:In this paper, the acid-base properties of Illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of Illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous Illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different Illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the Illite surfaces, they suggest that the surface behavior of the Illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
Chris Marone - One of the best experts on this subject based on the ideXlab platform.
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comparison of smectite and Illite rich gouge frictional properties application to the updip limit of the seismogenic zone along subduction megathrusts
Earth and Planetary Science Letters, 2003Co-Authors: D. Saffer, Chris MaroneAbstract:Abstract Along plate boundary subduction thrusts, the transformation of smectite to Illite within fault gouge at temperatures of ∼150°C is one of the key mineralogical changes thought to control the updip limit of seismicity. If correct, this hypothesis requires Illite-rich gouges to exhibit frictionally unstable (velocity-weakening) behavior. Here, we report on laboratory experiments designed to investigate the frictional behavior of natural and synthetic clay-rich gouges. We sheared 5-mm-thick layers of commercially obtained pure Ca-smectite, a suite of smectite–quartz mixtures, and natural Illite shale (grain size ranging from 2 to 500 μm) in the double-direct shear geometry to shear strains of ∼7–30 at room humidity and temperature. XRD analyses show that the Illite shale contains dominantly clay minerals and quartz; within the clay-sized fraction ( 40 MPa). Our data, specifically the velocity-strengthening behavior of Illite shale under a wide range of conditions, do not support the hypothesis that the smectite–Illite transition is responsible for the seismic–aseismic transition in subduction zones. We suggest that other depth- and temperature-dependent processes, such as cementation, consolidation, and slip localization with increased shearing, may play an important role in changing the frictional properties of subduction zone faults, and that these processes, in addition to clay mineralogy, should be the focus of future investigation.
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Comparison of smectite- and Illite-rich gouge frictional properties: Application to the updip limit of the seismogenic zone along subduction megathrusts
Earth and Planetary Science Letters, 2003Co-Authors: D. Saffer, Chris MaroneAbstract:Along plate boundary subduction thrusts, the transformation of smectite to Illite within fault gouge at temperatures of ∼150°C is one of the key mineralogical changes thought to control the updip limit of seismicity. If correct, this hypothesis requires Illite-rich gouges to exhibit frictionally unstable (velocity-weakening) behavior. Here, we report on laboratory experiments designed to investigate the frictional behavior of natural and synthetic clay-rich gouges. We sheared 5-mm-thick layers of commercially obtained pure Ca-smectite, a suite of smectite-quartz mixtures, and natural Illite shale (grain size ranging from 2 to 500 μm) in the double-direct shear geometry to shear strains of ∼7-30 at room humidity and temperature. XRD analyses show that the Illite shale contains dominantly clay minerals and quartz; within the clay-sized fraction (40 MPa). Our data, specifically the velocity-strengthening behavior of Illite shale under a wide range of conditions, do not support the hypothesis that the smectite-Illite transition is responsible for the seismic-aseismic transition in subduction zones. We suggest that other depth- and temperature-dependent processes, such as cementation, consolidation, and slip localization with increased shearing, may play an important role in changing the frictional properties of subduction zone faults, and that these processes, in addition to clay mineralogy, should be the focus of future investigation. © 2003 Elsevier B.V. All rights reserved.
