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G. E. Nauer - One of the best experts on this subject based on the ideXlab platform.

  • in situ x ray diffraction study of the electrochemical reaction on Lead electrodes in Sulphate electrolytes
    Materials Chemistry and Physics, 2009
    Co-Authors: P Angerer, R Mann, A Gavrilovic, G. E. Nauer
    Abstract:

    Abstract The anodic oxidation of pure Lead in two acidic Sulphate electrolytes with identical ionic strength (pH ∼ 0 and pH ∼ −0.1) was studied by in situ grazing incidence X-ray diffraction method (GIXD). Crystalline products such as Lead Sulphate (anglesite, PbSO4, orthorhombic), α- and β-Lead dioxide (α-PbO2, orthorhombic, and β-PbO2, tetragonal), and tribasic Lead Sulphate hydrate with the stoichiometric composition 3PbO·PbSO4·H2O (triclinic) were detected at defined potentials. A method for the semi-quantitative determination of the thickness of the deposited layer from diffraction data is described. After the in situ measurement, the washed and dried working electrodes were additionally characterized ex situ by GIXD measurements at different angles of incidence. The phase litharge (Lead oxide, t-PbO, tetragonal) and Lead Sulphate were observed at the surface of the Lead substrate. The quantitative evaluation of the diffraction intensity of this measurement series enables the modelling of a qualitative depth profile of the layer generated during the electrochemical treatment. The anglesite phase is located in the uppermost layer, while the litharge phase was detected closer to the Lead substrate.

  • Vibrational spectroscopy on the PbO-PbSO4 system and some related compounds: Part 1. Fundamentals, infrared and Raman spectroscopy
    Vibrational Spectroscopy, 1993
    Co-Authors: Günter Trettenhahn, G. E. Nauer, A. Neckel
    Abstract:

    The following compounds, Lead Sulphate (PbSO4), Lead oxide (PbO), Lead dioxide (PbO2), monobasic Lead Sulphate (PbO · PbSO4), tribasic Lead Sulphate (3PbO · PbSO4 · H2O) and tetrabasic Lead Sulphate (4PbO · PbSO4) can occur during the charge and discharge reactions of Lead electrodes in Lead acid batteries. These substances can also be detected in the active mass of Lead acid battery plates throughout the different steps in the production process. The appearance of the basic Lead Sulphates and of Lead oxide is an important indication of the passivation behaviour of the mechanism of the electrodes and points to the chemical and electrochemical oxidation reactions under the passive layer. For the investigation of this sensitive passive layer, it is important to avoid all the disadvantages of the predominantly used ex situ methods (especially x-ray analysis). Therefore, it is necessary to apply an in situ technique for the characterization of the Lead electrode surfaces in contact with the commonly used aqueous sulfuric acid solution. For this reason, external reflection absorption FT-IR spectroscopy was applied to investigate Lead electrodes under different electrochemical conditions. As a prerequisite for the planned in situ work, the vibrational spectra of the above mentioned compounds in the Pb-PbO-PbSO4-H2SO4 system must be known, in order to allow the identification of these substances on the electrodes in the in situ investigations. This work presents the infrared and Raman spectroscopic characterization of PbO, Pb3O4, PbSO4 PbO · PbSO4, 3PbO · PbSO4 · H2O and 4PbO · PbSO4.

  • In-situ FTIR investigation on Lead electrodes in 5-M sulfuric acid: formation and consumption of Lead Sulphate
    8th Intl Conf on Fourier Transform Spectroscopy, 1992
    Co-Authors: Günter Trettenhahn, G. E. Nauer, A. Neckel
    Abstract:

    By external reflection-absorption in situ FTIR spectroscopy, the generation of PbSO4 on Pb-electrodes in 5 M sulfuric acid was investigated. It was possible to monitor the process of Lead Sulphate formation (oxidation) during anodic polarization and of Lead Sulphate consumption (reduction) during cathodic polarization. A correlation exists between the electric charge passed through the Lead electrode and the intensity of absorption bands of Lead Sulphate.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Paolo Spinelli - One of the best experts on this subject based on the ideXlab platform.

  • the effect of expanders on Lead Sulphate formation and reduction
    Journal of Power Sources, 2000
    Co-Authors: Carlotta Francia, M Maja, Paolo Spinelli
    Abstract:

    The influence of some organic expanders on the formation of Lead-Sulphate has been studied by means of potentiostatic transients. The experimental data have been discussed according to the theories which have been proposed in the literature for the electro-crystallisation of Lead-Sulphate and Lead. The discussion of the data obtained confirms the inhibiting effect of the expanders on Lead sulphation. In fact, the tests showed that, when the expanders are added to the electrolyte, a longer time is required to reach the current maximum of the i(t) curve and a reduction of its intensity. According to the theoretical interpretation, this finding indicates a decreasing of the kinetic constant of the solid state process. The analysis of the i(t) transients obtained during the Sulphate reduction revealed an influence of expanders only when the Sulphate layers has been formed in their presence. Thus, it seems that the adsorption of the organic expanders on Lead is of primary importance for their action while adsorption on Lead-Sulphate appears to be negligible.

Gabriel Da Silva - One of the best experts on this subject based on the ideXlab platform.

  • kinetics and mechanism of the bacterial and ferric Sulphate oxidation of galena
    Hydrometallurgy, 2004
    Co-Authors: Gabriel Da Silva
    Abstract:

    The bacterial oxidation of galena (PbS) has been studied, largely due to its relevance to the bioleaching of sphalerite (ZnS) and other sulphide minerals. Ferric Sulphate oxidation experiments were first conducted as an analog to the indirect bio-oxidation mechanism, and the process was found to be diffusion-controlled due to the presence of a product layer. The bacterial oxidation of galena by a mixed culture of iron- and sulphur-oxidising bacterium was found to proceed according to a diffusion-controlled indirect mechanism, in which the primary role of the bacteria is the re-generation of ferric iron. Using quantitative XRD analysis, it was demonstrated that the oxidation product layer consisted solely of Lead Sulphate and elemental sulphur, in a 1:1 ratio. It was proposed that elemental sulphur and Lead ions were formed in a ferric oxidation reaction, while Lead Sulphate subsequently formed via precipitation of the Lead ions, consuming Sulphate ions from solution. The galena bio-oxidation experiments demonstrated considerable acid consumption, because of occlusion of the produced elemental sulphur by precipitated Lead Sulphate. This reveals a new mechanism through which galena oxidation may hinder the bioleaching of other sulphide minerals.

A. Neckel - One of the best experts on this subject based on the ideXlab platform.

  • In situ external reflection absorption FTIR spectroscopy on Lead electrodes in sulfuric acid
    Electrochimica Acta, 1996
    Co-Authors: Günter Trettenhahn, Gerhard Nauer, A. Neckel
    Abstract:

    The oxidation and reduction reactions of Lead electrodes in 5 molar sulfuric acid were investigated in situ using the technique of external reflection absorption infrared spectroscopy in combination with standard electrochemical techniques. The generation and consumption of Lead Sulphate were measured during galvanostatic experiments at different current densities. The amount of Lead Sulphate on the electrode surface was quantitatively determined by integrating the area of characteristic vibrational bands. Different anodic current densities Lead only to a little different oxidation behaviour of the Lead electrodes, the thickness of the passive Lead Sulphate layer depends mainly on the consumed charge. An increase for the amount of Lead Sulphate on the electrode surface was found during the cathodic processes also in the region of the Lead oxide reduction. This behaviour depends on the current densities applied and can be explained by the chemical reaction of Lead oxide with sulfuric acid or of freshly produced Lead, forming Lead Sulphate.

  • In Situ IR external Reflection‐absorption Spectroscopy as a Tool for Investigations of Electrodes in Aqueous Solutions: The Reactions of Lead Electrodes in Sulfuric Acid
    Berichte der Bunsengesellschaft für physikalische Chemie, 1993
    Co-Authors: Günter Trettenhahn, Gerhard Nauer, A. Neckel
    Abstract:

    The technique of external infrared reflection absorption spectroscopy combined with classical electrochemical techniques was used for the in situ characterization of the oxidation reactions of Lead electrodes in sulfuric acid. The generation and consumption of Lead Sulphate on the Lead electrode was measured during galvanostatic and potentiodynamic experiments. The amount of Lead Sulphate was quantitatively determined by integrating the area of a characteristic absorption band. Furthermore, the break down of the passive Lead Sulphate layer on the electrode connected with an oxidation of the Lead electrode in the course of a cathodic cycle in a potentiodynamic experiment could be demonstrated.

  • Vibrational spectroscopy on the PbO-PbSO4 system and some related compounds: Part 1. Fundamentals, infrared and Raman spectroscopy
    Vibrational Spectroscopy, 1993
    Co-Authors: Günter Trettenhahn, G. E. Nauer, A. Neckel
    Abstract:

    The following compounds, Lead Sulphate (PbSO4), Lead oxide (PbO), Lead dioxide (PbO2), monobasic Lead Sulphate (PbO · PbSO4), tribasic Lead Sulphate (3PbO · PbSO4 · H2O) and tetrabasic Lead Sulphate (4PbO · PbSO4) can occur during the charge and discharge reactions of Lead electrodes in Lead acid batteries. These substances can also be detected in the active mass of Lead acid battery plates throughout the different steps in the production process. The appearance of the basic Lead Sulphates and of Lead oxide is an important indication of the passivation behaviour of the mechanism of the electrodes and points to the chemical and electrochemical oxidation reactions under the passive layer. For the investigation of this sensitive passive layer, it is important to avoid all the disadvantages of the predominantly used ex situ methods (especially x-ray analysis). Therefore, it is necessary to apply an in situ technique for the characterization of the Lead electrode surfaces in contact with the commonly used aqueous sulfuric acid solution. For this reason, external reflection absorption FT-IR spectroscopy was applied to investigate Lead electrodes under different electrochemical conditions. As a prerequisite for the planned in situ work, the vibrational spectra of the above mentioned compounds in the Pb-PbO-PbSO4-H2SO4 system must be known, in order to allow the identification of these substances on the electrodes in the in situ investigations. This work presents the infrared and Raman spectroscopic characterization of PbO, Pb3O4, PbSO4 PbO · PbSO4, 3PbO · PbSO4 · H2O and 4PbO · PbSO4.

  • In-situ FTIR investigation on Lead electrodes in 5-M sulfuric acid: formation and consumption of Lead Sulphate
    8th Intl Conf on Fourier Transform Spectroscopy, 1992
    Co-Authors: Günter Trettenhahn, G. E. Nauer, A. Neckel
    Abstract:

    By external reflection-absorption in situ FTIR spectroscopy, the generation of PbSO4 on Pb-electrodes in 5 M sulfuric acid was investigated. It was possible to monitor the process of Lead Sulphate formation (oxidation) during anodic polarization and of Lead Sulphate consumption (reduction) during cathodic polarization. A correlation exists between the electric charge passed through the Lead electrode and the intensity of absorption bands of Lead Sulphate.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Bernt O Myrvold - One of the best experts on this subject based on the ideXlab platform.

  • interactions between lignosulphonates and the components of the Lead acid battery part 2 interactions with the electrolyte and Lead Sulphate growth
    Journal of Applied Electrochemistry, 2005
    Co-Authors: Bernt O Myrvold
    Abstract:

    Several lignin based expanders underwent various physical and chemical tests. The results were compared with life time measurements for batteries with the same expanders. The aim was to gain understanding of the interactions between the expanders and the other components in the Lead acid battery, and also, if possible, to find a quick and reliable screening test for the life time of batteries. The low pH of the sulphuric acid electrolyte will give both hydrolysis of the lignins and condensation. Hydrolysis seems to be detrimental to the performance. The lignosulphonate expanders seem to promote a dissolution–precipitation mechanism for Lead Sulphate formation.

  • Interactions between lignosulphonates and the components of the Lead-acid battery: Part 1. Adsorption isotherms
    Journal of Power Sources, 2003
    Co-Authors: Bernt O Myrvold
    Abstract:

    Abstract The expander performs at least five different tasks in the battery. It is a fluidiser for the negative paste. It controls the formation stage of the battery. It controls the shape and size of the Lead Sulphate crystals formed upon discharge, and thus prevents the sintering of the active mass. It controls the rate of the Lead to Lead Sulphate oxidation during discharge. Finally, it affects the charge acceptance. To gain more understanding of these different effects the interaction between Lead, Lead(II) oxide, Lead(IV) oxide, Lead Sulphate, barium Sulphate and carbon black and the experimental lignosulphonate (LS) expander UP-414 has been investigated. We also compared with Vanisperse A and several other lignosulphonates, to elucidate the mechanisms operating. In most cases, we have studied concentration ranges that are both higher and lower than those normally encountered in batteries. There is no adsorption of lignosulphonates to pure Lead surfaces. Adsorption to Lead Sulphate is a slow process. In the presence of Lead ions lignosulphonates will also adsorb to Lead. The adsorption to Lead(II) oxide is a fast process, and a strong adsorption occurs. In all these cases, it is preferably the high molecular weight fraction that interacts with the solid surfaces. Lead ions leaching from the surface complexes with lignosulphonates to give a more hydrophobic species. This allows the normally negatively charged lignosulphonate to adsorb to the negatively charged substrates. The lignosulphonates have an ability to complex Lead ions and keep them solvated. This confirms previous observations of the lignosulphonates ability to promote the dissolution–precipitation mechanism for Lead Sulphate formation on the expense of the solid-state reaction.