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  • 1.
    Ge, Xinlei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Extraction of Metal Values: Thermodynamics of Electrolyte Solutions and Molten Salts Extraction Process2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Over the past centuries, a number of process routes for extraction of metal values from an ore or other resources have been developed. These can generally be classifiedinto pyrometallurgical, hydrometallurgical or electrometallurgical routes. In the caseof the latter two processes, the reaction medium consists of liquid phase electrolytesthat can be aqueous, non-aqueous as well as molten salts. The present dissertationpresents the work carried out with two aspects of the above-mentioned electrolytes.First part is about the electrolyte solutions, which can be used in solvent extractionrelevant to many hydrometallurgical or chemical engineering processes; the secondpart is about the molten salts, which is often used in the electrometallurgical processesfor production of a variety of many kinds of metals or alloys, especially those that arehighly reactive.In the first part of this thesis, the focus is given to the thermodynamics ofelectrolyte solutions. Since the non-ideality of high concentration solution is not wellsolved, a modified three-characteristic-parameter correlation model is proposed,which can calculate the thermodynamic properties of high concentration electrolytesolutions accurately. Model parameters for hundreds of systems are obtained foraqueous as well as non-aqueous solutions. Moreover, a new predictive method tocalculate the freezing point depression, boiling point elevation and vaporizationenthalpy of electrolyte solutions is also proposed. This method has been shown to be agood first approximation for the prediction of these properties.In the second part, a process towards the extraction of metal values from slags,low-grade ores and other oxidic materials such as spent refractories using molten saltsis presented. Firstly, this process is developed for the recovery of Cr, Fe values fromEAF slag as well as chromite ore by using NaCl-KCl salt mixtures in the laboratoryscale. The slags were allowed to react with molten salt mixtures. This extraction stepwas found to be very encouraging in the case of Cr and Fe present in the slags. Byelectrolysis of the molten salt phase, Fe-Cr alloy was found to be deposited on thecathode surface. The method is expected to be applicable even in the case of V, Mnand Mo in the waste slags.Secondly, this process was extended to the extraction of copper/iron from copperore including oxidic and sulfide ores under controlled oxygen partial pressures.Copper or Cu/Fe mixtures could be found on the cathode surface along with theemission of elemental sulphur that was condensed in the cooler regions of the reactor.Thus, the new process offers a potential environmentally friendly process routereducing SO2 emissions.Furthermore, the cyclic voltammetric studies of metal ions(Cr, Fe, Cu, Mg, Mn)in (CaCl2-)NaCl-KCl salt melt were performed to understand the mechanisms, such asthe deposition potential, electrode reactions and diffusion coefficients, etc. In addition,another method using a direct electro-deoxidation concept(FFC Cambridge method),was also investigated for the electrolysis of copper sulfide. Sintered solid porouspellets of copper sulfide Cu2S and Cu2S/FeS were electrolyzed to elemental Cu, S andCu, Fe, S respectively in molten CaCl2-NaCl at 800oC under the protection of Argongas. This direct electrolysis of the sulfide to copper with the emission of elementalsulfur also offers an attractive green process route for the treatment of copper ore.

  • 2.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Grinder, Olle
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    The salt extraction process: A novel route for metal extraction part 1 - Cr, Fe recovery from EAF slags and low grade chromite ores2010Ingår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, ISSN 0371-9553, Vol. 119, nr 1, s. 27-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work is part of an investigation towards the development of a process route for the extraction of metal values from slag, low grade ores and other oxidic materials such as spent refractories using molten salts in the temperature range 800-950uC. The present paper focuses on the recovery of metal values, primarily Cr and Fe, from electric arc furnace slag and chromite ore. The impact of different factors to the dissolution of slag, such as temperature, holding time, flux content and weight ratio of flux/slag was studied. Based on the optimised experimental factors, the salt bath containing metal values extracted from the slag/ore was electrolysed under an applied voltage of 2·8 V. The cathode deposit was subjected to SEM/EDS and XRD analyses, which confirmed the formation of CrFe alloy. The process was also extended towards the production of CrFe alloy directly from chromite ore. The results show that the molten salt extraction process offers a promising route towards the recovery of metal values from slags and low grade ores.

  • 3.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jin, S.
    Zhang, M.
    Wang, X.
    Seetharaman, Surya
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    SYNTHESIS OF CHROMIUM AND FERROCHROMIUM ALLOY IN MOLTEN SALTS BY THE ELECTRO-REDUCTION METHOD2015Ingår i: Journal of Mining and Metallurgy, Section B: Metallurgy, ISSN 1450-5339, Vol. 51, nr 2, s. 185-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we successfully applied the Fray-Farthing-Chen Cambridge electro-reduction process on the preparation of chromium from chromium oxide, and for the first time, the synthesis of ferrochromium alloy from chromium oxide and iron oxide mixture and the chromite ore in molten calcium chloride. The present work systematically investigated the influences of sintered temperature of the solid precursor, electrochemical potential, electrolysis temperature and time on the products by using a set of advanced characterization techniques, including XRD and SEM/EDS analyses. In particular, our results show that this process is energy-friendly and technically-feasible for the direct extraction of ferrochromium alloy from chromite ore. Our findings thus provide useful insights for designing a novel green process to produce ferrochromium alloy from low-grade chromite ore or stainless steel slag.

  • 4.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    The salt extraction process - A novel route for metal extraction Part 2 - Cu/Fe extraction from copper oxide and sulphides2010Ingår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, ISSN 0371-9553, Vol. 119, nr 2, s. 93-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work is Part 2 of a novel salt extraction process towards the extraction of metal values from slag, low grade ores, etc. The authors describe the extraction of copper/iron from CuO, Cu 2S and CuFeS 2, which provides a green process route to treat the copper ore including both oxides and sulphides. The dissolution properties were investigated with respect to process parameters such as weight ratio of flux/copper ore and temperature. The highest extraction ratio is found at 92% in dissolution of Cu 2S, and residue of salt melt was confirmed to be mainly Al 2O 3. A cell voltage between 1·6 and 2·2 V is introduced for electrolysis, and the cathode products are proved to be pure Cu for electrolysis of CuO/Cu 2S, and Cu/Fe mixture for CuFeS 2 by X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy analysis. Some sulphur and iron chloride were found to volatilise and were deposited in the low temperature zone. Yield of copper has been estimated to be 52·3% during electrolysis of Cu 2S.

  • 5.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    A Simple Two-Parameter Correlation Model for Aqueous Electrolyte Solutions across a Wide Range of Temperatures2009Ingår i: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 54, nr 2, s. 179-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we focused on the correlation of the thermodynamic properties of aqueous solutions across a temperature range from (273.15 to 523.15) K by a simple two-parameter model. This model is based on the modified three-characteristic-parameter correlation (TCPC) model. The two parameters, b, distance of closest approach, and S, solvation parameter, represent the interactions between ions and ions-molecules, respectively. The results show that it can adequately correlate the activity coefficient and osmotic coefficient of the single electrolyte solutions. The set of two characteristic parameters for many electrolytes was obtained. We also obtained the temperature-dependent parameters for these electrolytes. In over 70 % of the cases, six to eight parameters are necessary for an electrolyte. Compared with the Pitzer model, our model also represented a good performance.

  • 6.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    Calculations of Freezing Point Depression, Boiling Point Elevation, Vapor Pressure and Enthalpies of Vaporization of Electrolyte Solutions by a Modified Three-Characteristic Parameter Correlation Model2009Ingår i: Journal of Solution Chemistry, ISSN 0095-9782, E-ISSN 1572-8927, Vol. 38, nr 9, s. 1097-1117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method was proposed for calculating the thermodynamic properties, freezing point depression, boiling point elevation, vapor pressure and enthalpy of vaporization for single solute electrolyte solutions, including aqueous and nonaqueous solutions, based on a modified three-characteristic-parameter correlation model. When compared with the corresponding literature values, the calculated results show that this method gives a very good approximation, especially for 1-1 electrolytes. Although the method is not very suitable for some solutions with very high ionic strength, it is still a very useful technique when experimental data is scarce.

  • 7.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap. Royal Inst Technol, Dept Mat Sci & Engn, S-10044 Stockholm, Sweden..
    Wang, Xidong
    Peking Univ, Coll Engn, Beijing 100871, Peoples R China..
    Erratum to: Calculations of Freezing Point Depression, Boiling Point Elevation, Vapor Pressure and Enthalpies of Vaporization of Electrolyte Solutions by a Modified Three-Characteristic Parameter Correlation Model2013Ingår i: Journal of Solution Chemistry, ISSN 0095-9782, E-ISSN 1572-8927, Vol. 42, nr 4, s. 894-895Artikel i tidskrift (Refereegranskat)
  • 8.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    Estimation of Freezing Point Depression, Boiling Point Elevation, and Vaporization Enthalpies of Electrolyte Solutions2009Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, nr 4, s. 2229-2235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel approach is presented in this work for predicting the values of freezing point depression and boiling point elevation for electrolyte solutions at different concentrations on the basis of the Pitzer theories. This method treats the enthalpy change of the solution between the normal freezing point or boiling point and the real ones to be linear temperature dependence. Compared with the literature values, this method performs very well; also, the temperature-dependent parameters of some salts are incorporated to investigate temperature effects of this method. Furthermore, a method based on the Clausius-Clapeyron equation is derived for estimation of the enthalpy of vaporization of very high concentration solutions at different temperatures, and the predicted results are highly positive.

  • 9.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Copper extraction from copper ore by electro-reduction in molten CaCl2-NaCl2009Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 18, s. 4397-4402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sintered solid porous pellets of copper sulfide (Cu2S) and Cu2S/FeS were electrolysed at a cell voltage of 2.2-2.8 V to elemental Cu, S and Cu, Fe, S, respectively in molten CaCl2-NaCl at 800 degrees C under the protection of argon gas. The process parameters for optimal electrolysis are presented. The electrolysis products are characterized by microscopic techniques and XRD. The product characteristics are linked to the process parameters. The direct electrolysis of the sulfide to copper with the emission of elemental sulphur offers an attractive green process route for the treatment of copper ore.

  • 10.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    Zhang, Mei
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Correlation and prediction of activity and osmotic coefficients of aqueous electrolytes at 298.15 K by the modified TCPC model2007Ingår i: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 52, nr 2, s. 538-547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The modification and extension of a three-characteristic-parameter correlation model for calculating the thermodynamic properties including osmotic and mean activity coefficients of aqueous electrolytes at 298.15 K have been presented in this paper. The model can be reduced with two parameters: b, the approaching parameter, and S, the solvation parameter. Although the model adequately describes the thermodynamics with these two parameters, the third parameter, n, which is related to the distance between an ion and a solvent molecule, also can be regarded as an adjustable parameter. The two sets of parameters for 283 single salts in aqueous solutions up to saturation have been obtained from the regression of experimental values. Mean activity or osmotic coefficients of RbNO2, MgCl2, Sm(ClO4)(3), and ZnSO4, with these two sets of parameters, have been compared with the smoothed experimental data, which show good agreement. When the model with three parameters is employed, it gives a more accurate result, especially in case of high concentration. The comparison with Pitzer and the original TCPC model also illustrates the excellent performance of this modified model.

  • 11.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Xiao, S. J.
    Haarberg, G. M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Salt extraction process-novel route for metal extraction Part 3-electrochemical behaviours of metal ions(Cr, Cu, Fe, Mg, Mn) in molten (CaCl2-)NaCl-KCl salt system2010Ingår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 119, nr 3, s. 163-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work is Part 3 of a novel salt extraction process towards the extraction of metal values from slag, low-grade ores, etc. The electrochemical behaviour of different metal ions, Cr(III), Cr(II), Cu(II), Fe(III), Mg(II) and Mn(II) was studied using cyclic voltammetry (CV) at 827°C in (CaCl 2-)NaCl-KCl system with a tungsten or glassy carbon electrode. The deposition process of Cr(III) species was found to be consisted of two electrochemical steps, while, in the case of other species, the deposition only involves one step. The deposition potentials and diffusion coefficients were determined from the cyclic voltammetrys. Electrodeposition of chromium was performed using a two-electrode cell under constant voltage, and pure dendrite and nodular-like crystals of chromium were obtained. The present study provides a good understanding of the electrochemical behaviour of these metal ions in molten salts, and thus is helpful to this novel salt process for the recovery of metal values from slag or other materials.

  • 12.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Xiao, Saijun
    Haarberg, Geir Martin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    The salt extraction process-A novel route for metal extraction. Part III: Electrochemical behaviors of the metal ions(Cr, Cu, Fe, Mg, Mn) in molten (CaCl2-)NaCl-KCl salt systemManuskript (preprint) (Övrigt vetenskapligt)
  • 13.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Zhang, Mei
    Guo, Min
    Wang, Xidong
    Correlation and prediction of thermodynamic properties of nonaqueous electrolytes by the modified TCPC model2008Ingår i: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 53, nr 1, s. 149-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the modified three-characteristic-parameter correlation model was introduced to correlate and predict the thermodynamic properties, such as the mean activity coefficient, the osmotic coefficient, and the solvent activity, of different kinds of nonaqueous electrolyte solutions. Two sets of parameters, (b, S) and (b, S, n), for 46 single salts in. methanol, ethanol, and 2-propanol, etc., were regressed from literature data at 298.15 K. Results of standard deviations showed the good applicability of our model. The calculated results of the mean activity coefficient by our model and the Pitzer model have been compared with each other with good agreement. Smoothed experimental data of osmotic coefficients and solvent activities were calculated with the present model with three or two parameters, and the one with three parameters showed a better performance. We also extended this model for some nonaqueous systems at elevated temperatures, and we also found good consistency between the results calculated from our model and experimental data. Moreover, we further developed this model for calculating those in the mixed-solvent electrolyte systems. The results showed our modified model could adequately describe these complicated electrolyte solutions.

1 - 13 av 13
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