| 1. |
- Du, Qing, et al.
(författare)
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Acid-base properties of aqueous illite surfaces
- 1997
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 187:1, s. 221-231
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Tidskriftsartikel (refereegranskat)abstract
- 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 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.
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| 2. |
- Du, Qing, et al.
(författare)
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Adsorption of copper at aqueous illite surfaces
- 1997
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 187:1, s. 232-242
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Tidskriftsartikel (refereegranskat)abstract
- 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, Cu2(OH)2CO3(s), rather than a copper hydroxide precipitate. The existence of Cu2(OH)2CO3(s) in the carbonate-containing illite suspensions was identified by FT-IR analysis.
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| 3. |
- Du, Qing, et al.
(författare)
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Complexations in illite–fulvic acid–Cu2+ systems
- 1999
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Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 33:3, s. 693-706
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 4. |
- Dyer, Chris D., et al.
(författare)
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The Raman spectroscopy of cement minerals under 1064 nm excitation
- 1993
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Ingår i: Spectrochimica Acta. Part A, Molecular Spectroscopy. - 0584-8539. ; 49:5-6, s. 715-722
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Tidskriftsartikel (refereegranskat)abstract
- The prospects for near-IR-excited Raman scattering from cement minerals are discussed, and a very unusual result concerning the intensity of the spectra is presented.
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| 5. |
- Dyer, Chris, et al.
(författare)
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Surface hydration of aqueous γ-Al2O3 studied by Fourier transform Raman and infrared spectroscopy—I. Initial results
- 1993
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Ingår i: Spectrochimica Acta. Part A, Molecular Spectroscopy. - 0584-8539. ; 49:5-6, s. 691-705
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Tidskriftsartikel (refereegranskat)abstract
- The hydration of γ-Al2O3 has been studied by Fourier transform (FT) Raman and infrared (IR) spectroscopy, and by X-ray diffraction (XRD). The initial findings are presented, along with a discussion of the possible causes for the major spectral changes that occur after hydration. The aims of the study and ongoing research are described.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Forsling, Willis, et al.
(författare)
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Surface complexation at hydrous fluorapatite
- 1993
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Ingår i: Aquatic Sciences. - 1015-1621 .- 1420-9055. ; 55:4, s. 336-346
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of H+, OH- and ARS (Alizarin Red S) onto hydrous fluorapatite surfaces and Ca2+-ARS complexation in solution were studied by means of combined potentiometric and spectrophotometric titrations, as well as zeta potential and FT-IR measurements. Corresponding equilibrium constants of surface and solution reactions are determined. The application in flotation processes is discussed.
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| 10. |
- Forsling, Willis, et al.
(författare)
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Use of surface complexation models in sulphide mineral flotation
- 1997
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 51:1-4, s. 81-95
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Tidskriftsartikel (refereegranskat)abstract
- Surface complexation modelling is introduced to investigate the surface reactions in a mixed galena and sphalerite flotation system. Computer-assisted calculations based on surface complexation modelling (SCM) are performed to obtain the mineral surface distribution of ethyl xanthate as well as carbonate and excess sulphide ions as a function of pH. The significance of pe is demonstrated by computing the mineral surface speciation in a flotation system with xanthate and excess of sulphide ions. The results are used to evaluate the influences of pH, pe, the concentration of xanthate, sulphide or carbonate ions to the mineral flotability. The flotation mechanisms in galena-sphalerite system are discussed based on SCM.
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