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  • 1. Degueldre, C.
    et al.
    Favarger, P. Y.
    Rosse, R.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry2006In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 68, no 3, p. 623-628Article in journal (Refereed)
    Abstract [en]

    Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of all titanium Colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (U-238(+), U-235(+) or 254[(UO)-U-238-O-16](+)) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.

  • 2. Degueldre, C.
    et al.
    Favarger, P. Y.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode2006In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 555, no 2, p. 263-268Article in journal (Refereed)
    Abstract [en]

    Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions (197)An(+) by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.

  • 3. Degueldre, C.
    et al.
    Raabe, J.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Investigations of clay colloid aggregates by scanning transmission X-ray microspectroscopy of suspensions2009In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 24, no 10, p. 2015-2018Article in journal (Refereed)
    Abstract [en]

    The environmental behaviour of colloidal clay in aquatic systems is linked to the properties of their aggregates. Earlier investigations of clay colloids were performed with electron microscope techniques which caused de-hydration of the particles. Information on the structure of colloid aggregates is needed for understanding their sedimentation behaviour, as well as colloid contaminant transport properties in natural systems. Scanning transmission X-ray microspectroscopy successfully produced images of montmorillonite colloid aggregates in a pseudo-equilibrium state in 1 mM NaCl suspensions equilibrated for more than a year. These clay aggregates were revealed at photon energies below the O absorption edges of clay and water. They were spherical or ellipsoidal with diameters of the order of 100-800 nm. The aggregates are porous and gel like with lower densities than the clay mineral. These investigations are important for modelling the occurrence of clay aggregates in aqueous environments.

  • 4.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Degueldre, Claude
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Frick, Sabrina
    Determining pseudo-equilibrium of montmorillonite colloids in generation and sedimentation experiments as a function of ionic strength, cationic form, and elevation2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 335, no 1, p. 54-61Article in journal (Refereed)
    Abstract [en]

    Colloid generation and sedimentation experiments were carried out on Na- and Ca-montmorillonite in order to verify whether pseudo-equilibrium concentrations are reached at the same level in both types of experiments. The size and concentration of colloidal Na- and Ca-montmorillonite particles were monitored as a function of time and distance from the colloid bed in different ionic strength solutions. A stable pseudo-equilibrium concentration was reached after time in generation and sedimentation experiments. The colloid concentration decreased sharply at distances near to the colloid source. Na-montmorillonite concentration at pseudo-equilibrium (roughly quantified at distances ≥7 cm from the colloid source) was 5.2 ± 0.5, 0.5 ± 0.1, and 0.2 ± 0.1 mg L-1 in 0.001, 0.01, and 0.1 M NaCl solution, respectively, while the Ca-montmorillonite concentration was 0.4 ± 0.2 mg L-1 in 0.001 M NaCl.

  • 5.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Temperature effect on the stability of bentonite colloids in water2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 298, no 2, p. 694-705Article in journal (Refereed)
    Abstract [en]

    The stability of natural bentonite suspensions has been investigated as a function of temperature at pH 9 and ionic strength 10-3 M. The sedimentation rate of the particles is directly related to their stability. The sedimentation kinetics was determined by examining the variation of particle concentration in solution with time. The observed kinetics for sedimentation is discussed quantitatively in terms of the potential energy between particles. The ζ-potential of the particles was measured and the DLVO theory was used to calculate attractive and repulsive potentials. Experimental observations are consistent with DLVO model predictions and show that the stability of bentonite colloids increases with temperature. Differences with other colloidal systems can be attributed to the temperature dependence of the surface charge of bentonite particles.

  • 6.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effects of temperature on the stability of colloidal montmorillonite particles at different pH and ionic strength2009In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 43, no 1, p. 21-26Article in journal (Refereed)
    Abstract [en]

    The effect of temperature at different pH and ionic strengths on the aggregation kinetics of colloidal montmorillonite particles in aqueous dispersions was investigated. For a given temperature and pH, the rate constant for aggregation increased with increasing ionic strength. At pH:54 the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH 10 the aggregation rate constant decreased with increasing temperature as a general trend. In the intermediate pH interval, the aggregation rate constant apparently decreased with increasing temperature except at the highest ionic strength, where it increased with increasing temperature. The aggregation rate constant decreased at alkaline pH compared with the acidic pH range. This effect became more pronounced at higher ionic strengths and higher temperatures but could not be observed at 4 degrees C. These observations are in qualitative agreement with DLVO calculations taking temperature, pH and ionic strength into account.

  • 7.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Kinetic determination of critical coagulation concentrations for sodium- and calcium-montmorillonite colloids in NaCl and CaCl2 aqueous solutions2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 315, no 2, p. 512-519Article in journal (Refereed)
    Abstract [en]

    The stability of the sodium and calcium forms of montmorillonite was studied at different NaCl and CaCl2 concentrations. The aggregation kinetics was determined from the decrease in particle concentration with time at different electrolyte concentrations. The DLVO theory defines the critical coagulation concentration (CCC) value as the electrolyte concentration that balances the attractive and repulsive potential energies between the particles, making aggregation diffusion-controlled. Therefore CCC values were obtained by extrapolation of the aggregation rate constants measured as a function of ionic strength to conditions where the rate constant value is determined by diffusion only. When the electrolyte was CaCl2, the CCC value was found to be approximately two orders of magnitude lower than the CCC values obtained using NaCl as electrolyte.

  • 8.
    Hedberg, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lowe, Troy
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Interactions between surfactants and silver nanoparticles of varying charge2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 369, no 1, p. 193-201Article in journal (Refereed)
    Abstract [en]

    The interaction between silvernanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant–Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.

  • 9.
    Hedberg, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Skoglund, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Karlsson, Maria-Elisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hedberg, Yolanda
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sequential Studies of Silver Released from Silver Nanoparticles in Aqueous Media Simulating Sweat, Laundry Detergent Solutions and Surface Water2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 13, p. 7314-7322Article in journal (Refereed)
    Abstract [en]

    From an increased use of silver nanoparticles (Ag NPs) as an antibacterial in consumer products follows a need to assess the environmental interaction and fate of their possible dispersion and release of silver. This study aims to elucidate an exposure scenario of the Ag NPs potentially released from, for example, impregnated clothing by assessing the release of silver and changes in particle properties in sequential contact with synthetic sweat, laundry detergent solutions, and freshwater, simulating a possible transport path through different aquatic media. The release of ionic silver is addressed from a water chemical perspective, compared with important particle and surface characteristics. Released amounts of silver in the sequential exposures were significantly lower, approximately a factor of 2, than the sum of each separate exposure. Particle characteristics such as speciation (both of Ag ionic species and at the Ag NP surface) influenced the release of soluble silver species present on the surface, thereby increasing the total silver release in the separate exposures compared with sequential immersions. The particle stability had no drastic impact on the silver release as most of the Ag NPs were unstable in solution. The silver release was also influenced by a lower pH (increased release of silver), and cotransported zeolites (reduced silver in solution).

  • 10. Henry, Christophe
    et al.
    Norrfors, K. Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Karlsruhe Institute of Technology, Germany.
    Olejnik, Michal
    Bouby, Muriel
    Luetzenkirchen, Johannes
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Karlsruhe Institute of Technology, Germany.
    Minier, Jean-Pierre
    A refined algorithm to simulate latex colloid agglomeration at high ionic strength2016In: Adsorption, ISSN 0929-5607, E-ISSN 1572-8757, Vol. 22, no 4-6, p. 503-515Article in journal (Refereed)
    Abstract [en]

    This study is focussed on the simulation of particle agglomeration at relatively high ionic strength using a refined stochastic algorithm developed in the context of parcel-tracking approaches. For that purpose, experimental data of both diffusion-limited and reaction-limited aggregation of latex particles were obtained using dynamic light scattering techniques for different initial particle sizes (diameters ranging from 24 to 495 nm) and at various chemical conditions (ionic strength between 0.5 and 2 M with NaCl or CaCl2 solutions). The experimental data collected have been compared to numerical results obtained with the refined parcel-tracking algorithm for particle agglomeration which has been developed. Results show that the evolution of the aggregate diameters over time can be properly captured by the present model with the value of the aggregate fractal dimension that is extracted from experimental data.

  • 11.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Influence of γ-radiation on the reactivity of Montmorillonite towards H2O22012In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 81, no 2, p. 190-194Article in journal (Refereed)
    Abstract [en]

    Compacted and water saturated bentonite will be used as an engineered barrier in deep geological repositories for radioactive waste in many countries. Due to the high dose rate of ionizing radiation outside the canisters holding the nuclear waste, radiolysis of the interlayer and pore water in the compacted bentonite is unavoidable. Upon reaction with the oxidizing and reducing species formed by water radiolysis (OH•, e-(aq), H•, H202, H2, H02•, H30+), the overall redox properties in the bentonite barrier may change. In this study the influence of γ-radiation on the structural Fe(II)/Fe(III) content in montmorillonite and its reactivity towards hydrogen peroxide (H2O2) was investigated in parallel experiments. The results show that under anoxic conditions the structural Fe(II)/FeTot ratio of dispersed montmorillonite are increased from ≤ 3 to 25-30% after γ-doses comparable to repository conditions. Furthermore, a strong correlation between the structural Fe(II)/FeTot ratio and the H2O2 decomposition rate in montmorillonite dispersions was found. This correlation was further verified in experiments with consecutive H2O2 additions, since the structural Fe(II)/FeTot ratio was seen to decrease concordantly. This work shows that the structural iron in montmorillonite could be a sink for one of the major oxidants formed upon water radiolysis in the bentonite barrier, H2O2.

  • 12.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Norrfors, Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Effect of γ-radiation on Radionuclide Retention in Compacted Bentonite2011In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 80, no 12, p. 1371-1377Article in journal (Refereed)
    Abstract [en]

    Compacted bentonite is proposed as an engineered barrier in many concepts for disposal of high level nuclear waste. After the initial deposition however, the bentonite barrier will inevitably be exposed to ionizing radiation (mainly gamma) under anoxic conditions. Because of this, the effects of gamma-radiation on the apparent diffusivity values and sorption coefficients in bentonite for Cs(+) and Co(2+) were tested under different experimental conditions. Radiation induced effects on sorption were in general more noticeable for Co(2+) than for Cs(+), which generally showed no significant differences between irradiated and unirradiated clay samples. For Co(2+) however, the sorption to irradiated MX80 was significantly lower than to the unirradiated clay samples regardless of the experimental conditions. This implies that gamma-radiation may alter the surface characteristics contributing to surface complexation of Co(2+). With the experimental conditions used, however, the effect of decreasing sorption was not large enough to be reflected on the obtained D. values.

  • 13.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Colloid diffusion in compacted bentonite: microstructural constraints2010In: Clays and clay minerals, ISSN 0009-8604, E-ISSN 1552-8367, Vol. 58, no 4, p. 532-541Article in journal (Refereed)
    Abstract [en]

    In Sweden and in many other countries, a bentonite barrier will be used in the repository for spent nuclear fuel. In the event of canister failure, colloidal diffusion is a potential, but scarcely studied mechanism of radionuclide migration through the bentonite barrier. Column and in situ experiments are vital in understanding colloid diffusion and in providing information about the microstructure of compacted bentonite and identifying cut-off limits for colloid filtration. This study examined diffusion of negatively charged 2-, 5-, and 15-nm gold colloids in 4-month diffusion experiments using MX-80 Wyoming bentonite compacted to dry densities of 0.6–2.0 g/cm3. Breakthrough of gold colloids was not observed in any of the three diffusion experiments. In a gold-concentration profile analysis, colloid diffusion was only observed for the smallest gold colloids at the lowest dry density used (estimated apparent diffusivity Da 5x10–13 m2/s). The results from a microstructure investigation using low-angle X-ray diffraction suggest that at the lowest dry density used, interlayer transport of the smallest colloids cannot be ruled out as a potential diffusion pathway, in addition to the expected interparticle transport. In all other cases, with either greater dry densities or larger gold colloids, compacted bentonite will effectively prevent diffusion of negatively charged colloids due to filtration.

  • 14.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Free porosity investigation of compacted Bentonite using XRDIn: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053Article in journal (Other academic)
    Abstract [en]

    Many countries intend to use compacted bentonite as abarrier in their deep geological repositories for nuclearwaste. In order to describe and predict hydraulicconductivity or radionuclide transport through thebentonite barrier, fundamental understanding of themicrostructure of compacted bentonite is needed. Thisstudy examined the interlayer swelling and overallmicrostructure of Wyoming Bentonite MX-80 and thecorresponding homo-ionic Na+ and Ca2+ forms, usingXRD with samples saturated under confined swellingconditions and free swelling conditions. For thesamples saturated under confined conditions, theinterparticle, or so-called free porosity was estimatedby comparing the experimental interlayer distancesobtained from one-dimensional XRD profile fittingagainst the maximum interlayer distances possible forthe corresponding water content. The results showedthat interlayer porosity dominated total porosity,irrespective of water content, and that free porositywas lower than previously reported in the literature. Atcompactions relevant for the saturated bentonitebarrier (1.4-1.8 g/cm3), the free porosity was estimatedto ≤ 3%.

  • 15.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Free Porosity of Compacted Saturated MX-80 Bentonite and Na-montmorillonite as a Function of Dry Density2009Article in journal (Refereed)
  • 16.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Porosity investigation of compacted bentonite using XRD profile modeling2012In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 128, no 1-4, p. 19-32Article in journal (Refereed)
    Abstract [en]

    Many countries intend to use compacted bentonite as a barrier in their deep geological repositories for nuclear waste. In order to describe and predict hydraulic conductivity or radionuclide transport through the bentonite barrier, fundamental understanding of the microstructure of compacted bentonite is needed. This study examined the interlayer swelling and overall microstructure of Wyoming Bentonite MX-80 and the corresponding homo-ionic Na+ and Ca2+ forms, using XRD with samples saturated under confined swelling conditions and free swelling conditions. For the samples saturated under confined conditions, the interparticle, or so-called free or external porosity was estimated by comparing the experimental interlayer distances obtained from one-dimensional XRD profile fitting against the maximum interlayer distances possible for the corresponding water content. The results showed that interlayer porosity dominated total porosity, irrespective of water content, and that the interparticle porosity was lower than previously reported in the literature. At compactions relevant for the saturated bentonite barrier (1.4-1.8 g/cm(3)), the interparticle porosity was estimated to <= 3%.

  • 17.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    García García, Sandra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Effects of gamma-irradiation on the stability of colloidal Na+-Montmorillonite dispersions2009In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 43, no 1, p. 86-90Article in journal (Refereed)
    Abstract [en]

    In many concepts for final storage of spent nuclear fuel bentonite will be used as an engineered barrier, mainly due to its inertness, plasticity and ability to retard transport of radionuclides by adsorption. In the event of water-bearing fractures making contact with the bentonite barrier, generation and transport of colloidal particles will strongly depend on groundwater composition and the surface properties of the colloidal particles. The bentonite barrier will unavoidably be exposed to ionizing radiation from the spent nuclear fuel but very little is known about effects of ionizing radiation on bentonite concerning colloidal stability. In this work we have studied the effect of gamma-radiation on the stability of dilute colloidal Na+-montmorillonite dispersions using a Cs-137 gamma-source (doses of 0-53.2 kGy). Aggregation kinetics and sedimentation experiments revealed significant radiation effects, evident as increased colloid stability. The only rationale for this is a gamma-radiation induced increase in surface potential. The effects appeared to depend on the Na+-montmorillonite concentration in the irradiated dispersions, indicating that the change in surface potential is induced by aqueous radiolysis products.

  • 18.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Petterson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Effects of the injection grout Silica sol on Bentonite2011In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 36, no 17/18, p. 1580-1589Article in journal (Refereed)
    Abstract [en]

    Silica sol, i.e., colloidal SiO2, may be used as a low-pH injection grout for very fine fractures in the construction of deep geological repositories for radioactive waste in Sweden and in Finland. If the bentonite barrier encounters SiO2-colloid particles under conditions favorable for aggregation, there is concern that it will modify the bentonite barrier at the bentonite/bedrock interface. In this study qualitative experiments were performed with mixed dispersions of SiO2-colloids and bentonite or homo-ionic Na/Ca-montmorillonite. Samples were prepared at different colloid concentrations and treated under various conditions such as low and high ionic strength (0.3 M NaCl), as well as dehydration and redispersing. Free swelling and settling experiments were performed in order to qualitatively compare the conditions in which SiO2-colloids affect the bulk/macro properties of bentonite. In order to study specific SiO2-colloid/montmorillonite interactions and preferred type of initial aggregation, dilute dispersions of homo-ionic montmorillonite dispersions mixed with varying concentrations of SiO2-colloids were prepared and selected samples were characterized by PCS, SEM/EDS, AFM and PXRD. The results from this study show that bentonite and montmorillonite particles can be modified by SiO2-colloids when mixed in comparable amounts, due to dehydration or high ionic strength. Some indications for increased colloidal stability for the SiO2-colloid modified clay particles were also found. From the AFM investigation it was found that initial attachment of the SiO2-colloids in Na+ dominated samples seemed to occur on the edges of the montmorillonite layers. In Ca2+ dominated samples not subjected to excess NaCl, SiO2-colloid sorption onto the faces of the montmorillonite layers was also found. In all, contact between the bentonite barrier and ungelled Silica sol should preferably be avoided.

  • 19.
    Jansson, Mats
    et al.
    KTH, Superseded Departments, Chemistry. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Eriksen, Trygve E
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, Superseded Departments, Chemistry. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    LOT: in situ diffusion experiments using radioactive tracers2003In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 23, no 1-4, p. 77-85Article in journal (Refereed)
    Abstract [en]

    An experiment series at Aspo Hard Rock Laboratory, called "Long Term Test of Buffer Material", LOT, are carried out at Aspo Hard Rock Laboratory to validate models of clay buffer performance at standard KBS-3 repository conditions and to quantify clay buffer alteration processes at adverse conditions. In conjunction with the tests of the bentonite, cation diffusion tests using caesium and cobalt are performed. Each test contains 38 cylindrical blocks of bentonite clay with a hole in the middle which are placed around a copper rod in a vertically drilled hole at a depth of 450 m. In each test, four identical cylindrical bentonite plugs, doped with 1 MBq Co-57 and Cs-134, respectively, are inserted in the fifth block from the bottom. The system was left to be saturated with ground water before heating of the central copper rod started to simulate the thermal activity of radioactive waste. The experiments continued for 14 months before the bentonite blocks were drilled out using over-core drilling technique. The lowest blocks were cut up, sparsely in the outer layer, and in cubic centimeters, big samples closer to where the activity was inserted. All samples were analyzed using a gamma spectrometer to get a three-dimensional picture of the activity distribution. The system was then fitted to a diffusion model to obtain apparent diffusivities for the two cations. The apparent diffusivity for cobalt agrees well with those obtained in other in situ experiments and in laboratory studies, while the value for caesium is lower than expected. This can be due to that the clay was not fully water saturated during the experiment.

  • 20. Karnland, O
    et al.
    Sandén, T
    Johannesson, L-E
    Eriksen, Trygve
    KTH, Superseded Departments, Chemistry.
    Jansson, Mats
    KTH, Superseded Departments, Chemistry.
    Wold, Susanna
    KTH, Superseded Departments, Chemistry.
    Pedersen, K
    Rosborg, B
    Long term test of buffer material: Final report on the pilot parcels2000Report (Other academic)
  • 21.
    Lowe, Troy A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Chemical Speciation Measurements of Silver Ions in Alkaline Carbonate Electrolytes Using Differential Pulse Stripping Voltammetry on Glassy Carbon Compared With Ion Selective Electrode Measurements2013In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 8, no 3, p. 3851-3865Article in journal (Refereed)
    Abstract [en]

    Given the increasing incorporation of silver nanoparticles as an antibacterial additive in washing machines and textiles, sensitive methods for accurate determination of Ag+ ions in laundry relevant electrolytes (alkaline carbonate) are required. The most widely reported method, the silver ion selective electrode (ISE), lacked sensitivity and accuracy and was affected by the concentration of Na2CO3 in solution. Differential pulse stripping voltammetry (DPSV) on glassy carbon electrodes (GCE) was therefore investigated as an alternative technique. Surface preparation of the GCE surface was essential and a suitable procedure was developed. A linear response was observed from 0 to 180 mg L-1 with a lower detection limit of 500 ng L-1 (5 nM). DPSV was shown to be significantly more sensitive and accurate in determining the Ag+ activity than the silver ISE technique, particularly below 200 nM.

  • 22.
    Norrfors, K. Karin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Björkbacka, Åsa
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kessler, Amanda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Wold, Susanna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    γ-radiation induced corrosion of copper in bentonite-water systems under anaerobic conditions2018In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 144, p. 8-12Article in journal (Refereed)
    Abstract [en]

    In this work we have experimentally studied the impact of bentonite clay on the process of radiation-induced copper corrosion in anoxic water. The motivation for this is to further develop our understanding of radiation-driven processes occurring in deep geological repositories for spent nuclear fuel where copper canisters containing the spent nuclear fuel will be embedded in compacted bentonite. Experiments on radiation-induced corrosion in the presence and absence of bentonite were performed along with experiments elucidating the impact irradiation on the Cu2+ adsorption capacity of bentonite. The experiments presented in this work show that the presence of bentonite clay has no or very little effect on the magnitude of radiation-induced corrosion of copper in anoxic aqueous systems. The absence of a protective effect similar to that observed for radiation-induced dissolution of UO2 is attributed to differences in the corrosion mechanism. This provides further support for the previously proposed mechanism where the hydroxyl radical is the key radiolytic oxidant responsible for the corrosion of copper. The radiation effect on the bentonite sorption capacity of Cu2+ (reduced capacity) is in line with what has previously been reported for other cations. The reduced cation sorption capacity is partly attributed to a loss of Al-OH sites upon irradiation.

  • 23.
    Norrfors, Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Bouby, Muriel
    Heck, Stephanie
    Finck, Nicolas
    Marsac, Rémi
    Schäfer, Thorsten
    Geckeis, Horst
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Montmorillonite colloids I: Characterization and stability ofsuspensions with different size fractionsManuscript (preprint) (Other academic)
  • 24.
    Norrfors, Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Bouby, Muriel
    Luetzenkirchen, Johannes
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Smectite and latex colloid agglomeration at high ionic strength: Is there any effect of particle size?Manuscript (preprint) (Other academic)
  • 25.
    Norrfors, Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Bouby, Muriel
    Marsac, Rémi
    Heck, Stephanie
    Schäfer, Thorsten
    Geckeis, Horst
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Montmorillonite colloids II: Dependency of Colloidal size on Sorption of RadionuclidesManuscript (preprint) (Other academic)
  • 26.
    Norrfors, Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Bouby, Muriel
    Marsac, Rémi
    Heck, Stephanie
    Schäfer, Thorsten
    Geckeis, Horst
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Montmorillonite colloids III: Influence of Colloidal Size onthe Sorption Reversibility of RadionuclidesManuscript (preprint) (Other academic)
  • 27.
    Norrfors, Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kessler, Amanda
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Björkbacka, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Radiation induced corrosion of copper in bentonite-water systems under anaerobic conditionsManuscript (preprint) (Other academic)
  • 28.
    Norrfors, Knapp Karin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. Karlsruhe Institute of Technology (KIT), Germany.
    Bouby, Muriel
    Heck, Stephanie
    Finck, Nicolas
    Marsac, Rerni
    Schaefer, Thorsten
    Geckeis, Horst
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions2015In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 114, p. 179-189Article in journal (Refereed)
    Abstract [en]

    Bentonite is planned to be used as a technical barrier in the final storage of spent nuclear fuel and high level vitrified waste. In contact with ground water of low ionic strength, montmorillonite colloids may be released from the bentonite buffer and thereby enhance the transport of radionuclides (RNs) sorbed: In the present case, clay colloids represent aggregates of several clay mineral layers. It is of major importance to determine RN sorption properties for different sizes of montmorillonite aggregates, since size fractionation may occur during particle transport in natural media. In this study, a protocol for size fractionation of clay aggregates is developed, by sequential and direct centrifugation, in the presence and absence of organic matter. Seven colloidal fractions of different mean aggregate sizes are obtained ranging, when considering the mean equivalent hydrodynamic sphere diameter (ESD), from similar to 960 nm down to similar to 85 nm. Applying mathematical treatments (Jennings and Parslow, 1988) and approximating the clay aggregates to regular disc-shaped stacks of clay mineral sheets result in mean surface diameters varying from similar to 1.5 mu m down to similar to 190 nm. All these colloidal fractions are characterized by XRD, IC and ICP-OES where they are found to have the same chemical composition. The number of edge sites (aluminol and silanol) is estimated (in mol/kg) for each colloidal fraction according to (Tournassat et al., 2003). It is calculated from the mean particle sizes obtained from AsFlFFF and PCS measurements, where the clay aggregates are approximated to regular disc-shaped stacks of clay mineral sheets. The estimated number of edge sites varies significantly for the different clay dispersions. In addition, stability studies using the various clay colloidal fractions are performed by the addition of NaCl, CaCl2 or MgCl2, in the presence or absence of organic matter, where no difference in stability is found.

  • 29.
    Norrfors, Knapp Karin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Karlsruhe Institute of Technology (KIT), Germany.
    Marsac, Remi
    Bouby, Muriel
    Heck, Stephanie
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Luetzenkirchen, Johannes
    Schäfer, Thorsten
    Montmorillonite colloids: II. Colloidal size dependency on radionuclide adsorption2016In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 123, p. 292-303Article in journal (Refereed)
    Abstract [en]

    Bentonite is a strong radionuclide (RN) adsorbent. As a consequence, it is proposed as one of the engineered safety barriers in many nuclear waste disposal concepts in granite formations. Despite the many beneficial effects of bentonite, in contact with groundwater of low ionic strength montmorillonite colloids may be released from the bentonite buffer and transported towards the biosphere carrying the RNs bound to it. During the transport of colloids in bedrock fractures, size separation of clay colloids may occur, which may further affect RN mobility. In this work, RN adsorption (Th(IV), U(VI), Np(V), Tc(VII) and Pu(IV)) onto size fractionated montmorillonite colloids was studied in a synthetic, carbonated groundwater. Fractionation was done by simple settling procedures and sequential centrifugation. We combined batch adsorption experiments and geochemical modelling for the adsorption studies. U(VI), Np(V) and Tc(VII) did not adsorb to montmorillonite in the synthetic groundwater. Adsorption of Th(IV) and Pu(IV) is strong but, within experimental uncertainties, not significantly affected by the fractionation process. Montmorillonite colloids obtained by fractionation of the raw clay material but in the presence of organic matter during the initial separation step present significantly reduced uptake of Th and Pu. Based on the results, implementation of an "average log K-D" (i.e. average distribution coefficients) for all colloidal sizes in reactive transport modelling codes would be acceptable.

  • 30.
    Pradhan, Sulena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Tech Res Inst, Sweden.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Effect of sonication on particle dispersion, administered dose and metal release of non-functionalized, non-inert metal nanoparticles2016In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 18, no 9, article id 285Article in journal (Refereed)
    Abstract [en]

    In this study, we elucidate the effect of different sonication techniques to efficiently prepare particle dispersions from selected non-functionalized NPs (Cu, Al, Mn, ZnO), and corresponding consequences on the particle dose, surface charge and release of metals. Probe sonication was shown to be the preferred method for dispersing non-inert, non-functionalized metal NPs (Cu, Mn, Al). However, rapid sedimentation during sonication resulted in differences between the real and the administered doses in the order of 30-80 % when sonicating in 1 and 2.56 g/L NP stock solutions. After sonication, extensive agglomeration of the metal NPs resulted in rapid sedimentation of all particles. DLVO calculations supported these findings, showing the strong van der Waals forces of the metal NPs to result in significant NP agglomeration. Metal release from the metal NPs was slightly increased by increased sonication. The addition of a stabilizing agent (bovine serum albumin) had an accelerating effect on the release of metals in sonicated solutions. For Cu and Mn NPs, the extent of particle dissolution increased from <1.6 to similar to 5 % after sonication for 15 min. A prolonged sonication time (3-15 min) had negligible effects on the zeta potential of the studied NPs. In all, it is shown that it is of utmost importance to carefully investigate how sonication influences the physicochemical properties of dispersed metal NPs. This should be considered in nanotoxicology investigations of metal NPs.

  • 31.
    Skoglund, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lowe, Troy A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Effect of Laundry Surfactants on Surface Charge and Colloidal Stability of Silver Nanoparticles2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 28, p. 8882-8891Article in journal (Refereed)
    Abstract [en]

    The stability of silver nanoparticles (Ag NPs) potentially released from clothing during a laundry cycle and their interactions with laundry-relevant surfactants [anionic (LAS), cationic (DTAC), and nonionic (Berol)] have been investigated. Surface interactions between Ag NPs and surfactants influence their speciation and stability. In the absence of surfactants as well as in the presence of LAS, the negatively charged Ag NPs were stable in solution for more than 1 day. At low DTAC concentrations (<= 1 mM), DTAC-Ag NP interactions resulted in charge neutralization and formation of agglomerates. The surface charge of the particles became positive at higher concentrations due to a bilayer type formation of DTAC that prevents from agglomeration due to repulsive electrostatic forces between the positively charged colloids. The adsorption of Berol was enhanced when above its critical micelle concentration (cmc). This resulted in a surface charge dose to zero and subsequent agglomeration. Extended DLVO theory calculations were in compliance with observed findings. The stability of the Ag NPs was shown to depend on the charge and concentration of the adsorbed surfactants. Such knowledge is important as it may influence the subsequent transport of Ag NPs through different chemical transients and thus their potential bioavailability and toxicity.

  • 32.
    Sulena, Pradhan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rosenqvist, Jörgen
    Department of Chemistry and Molecular Biology,University of Gothenburg.
    Jonsson, Caroline M.
    Department of Chemistry and Molecular Biology,University of Gothenburg.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE).
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Influence of humic acid and dihydroxy benzoic acid on the agglomeration, adsorption, sedimentation and dissolution of copper, manganese, aluminum and silica nanoparticles – a tentative exposure scenarioManuscript (preprint) (Other academic)
    Abstract [en]

    The overall objective of this study was to fill existing knowledge gaps related to the potential dispersion and environmental fate of reactive metallic nanoparticles (NPs) for future use in predictive NP fate models. The work focuses on kinetic aspects of stability, mobility, and dissolution of bare Cu, Al and Mn NPs in synthetic freshwater (FW) with and without the presence of natural organic matter (NOM). This includes elucidation of particle and surface interactions, metal dissolution kinetics and speciation predictions of released metals in solution. Parallel stability measurements were performed on SiO2 NPs. NOM was in this study represented by dihydroxy benzoic acid (DHBA) monomers and Suwannee River Humic Acid.DHBA or humic acid rapidly adsorbed on all metal NPs (< 1 min) via multiple surface coordinations, followed in general by rapid agglomeration (predominantly due to strong van-der Waal forces) and concomitant sedimentation for a large fraction of the particles. No adsorption of NOM was observed for the SiO2 NPs, which remained stable in solution. The concentration and type of NOM influenced the degree of agglomeration, sedimentation, and dissolution of the metal NPs. DHBA in concentrations of 0.1 and 1 mM was unable to stabilize the metal NPs for time periods longer than 6 h, whereas humic acid, at certain concentrations (20 mg/L) was more efficient (>24 h). The presence of NOM in FW increased the amount of released metals into solution, in particular pronounced for Al and Cu, whereas 

    the effect for Mn was minor or non-significant. At least 10% of the particle mass was dissolved within 24 h and remained in solution. Speciation modeling revealed that released Al and Cu predominantly formed complexes with NOM without the existence of free ions or labile complexes, whereas less complexation was seen for Mn, predominantly present as free ions.From an environmental fate perspective, the results imply that potentially dispersed NPs of Cu, Al and Mn readily dissolve or sediment closes to the source in freshwaters of low salinity, whereas SiO2 NPs are more stable and mobile in solution. Released Cu and Al into FW form stable NOM-complexes of low bioavailability whereas released Mn predominantly remains as free bioavailable ions.

  • 33.
    Wold, Susanna
    et al.
    KTH, Superseded Departments, Chemistry.
    Eriksen, T. E.
    Diffusion of lignosulfonate colloids in compacted bentonite2003In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 23, no 04-jan, p. 43-50Article in journal (Refereed)
    Abstract [en]

    Colloids, as humic acid, are known to be strong complexing agent for radionuclides. If such colloids are introduced into the bentonite barrier in a repository for spent fuel, the diffusivities for radionuclides can change. The colloid complexed radionuclides diffusivities will be governed by the colloidal diffusivities, and the transport of strongly bentonite sorbed radionuclides might be facilitated into the biosphere. The diffusive properties of Lignosulfonate (LS) colloids dissolved in 0.01 and 0.1 M NaClO4 in bentonite of dry densities 0.6, 0.8, 1.0, 1.2, 1.5, and 1.8 g/cm(3) are studied. LS is used as a model substance for humic acid. Independent of ionic strength and of dry density apparent diffusivities in the order of 10(-8) cm(2)/s were obtained. The ratios of effective diffusivity/apparent diffusivity are in accordance with the porosities of the bentonite. The diffusing colloids were not found to be hindered by ionic exclusion or by filtering effects. The results indicate that the LS diffuse through the bentonite as small uncharged colloids. It seems that ionic strength greater than or equal to 0.01 M NaClO4 provides enough ions to shield the charged sites on the colloids, and the colloids can coil into smaller units.

  • 34.
    Wold, Susanna
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Eriksen, Trygve
    Diffusion of humic colloids in compacted bentonite2007In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 32, no 07-jan, p. 477-484Article in journal (Refereed)
    Abstract [en]

    Through-diffusion experiments in bentonite with humic colloids in the size range of 1-10 nm were carried out. Bentonite was compacted to 0.6-1.8 g/cm(3) dry density and equilibrated with 0.01 and 0.1 M NaClO4 solutions. Experiments with Eu(Ill) diffusing in the absence and presence of humics were run in parallel, as well as Co(ll) diffusing through compacted bentonite in the presence of hurnics. The hurnic colloid diffusion experiments were run for 60 days and the humic concentration in the outlet solutions measured at time intervals. The experimental breakthrough curves for humic substances (HS) as well as the HS, Co(II) and Eu(III) profiles in the bentonite were simulated using the finite difference based computer code ANADIFF. Regardless of the compaction and ionic strength of solutions, hurnic colloids diffused through the compacted bentonite. The effects of hurnic colloids on both Co(H) and Eu(111) sorption as well as on diffusion were significant. The apparent diffusivity (D-a) increased significantly for both Co(II) and Eu(III) when hurnic colloids were present and the distribution coefficient (K-d) values decreased.

  • 35.
    Yang, Guomin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Density functional theory of electrolyte solutions in slit-like nanopores I. The RFD/WCA approach extended to non-restricted primitive model2017In: APPLIED CLAY SCIENCE, ISSN 0169-1317, Vol. 135, p. 526-531Article in journal (Refereed)
    Abstract [en]

    An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) is tested for the description of the non-restricted primitive model of electrolyte solutions in slit-like nanopores. The RFD/WCA approach of modeling size-asymmetric ions is validated by reproducing the density and electrostatic potential profiles of planar electrical double layer systems in the presence of mixtures of mono- and multivalent ions. The results from the DFT agree quite well with Monte Carlo simulations and satisfy the contact density sum rules of ionic fluid under a wide range of conditions. These findings suggest that a generic RFD/WCA approach can be formulated within the framework of the restricted and non-restricted primitive model to further investigate the swelling and ion exchange of clay minerals.

  • 36.
    Yang, Guomin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Density functional theory of electrolyte solutions in slit-like nanopores II. Applications to forces and ion exchange2016In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 132, p. 561-570Article in journal (Refereed)
    Abstract [en]

    An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) for size-asymmetric electrolytes presented in part I is applied to calculate the forces and the ion exchange for Ca- and Na-montmorillonite systems in equilibrium with salt solutions. Our modeling shows that the DFT calculations are in excellent agreement with Monte Carlo simulations and experimental results. The results indicate that the ion size plays an important role in force-distance relation. Due to the excluded volume effect, the osmotic pressure curve predicted by DFT is shifted towards larger separation distances with increasing the diameter of counterions. Additionally, the interaction can be switched from attraction to repulsion with increasing diameter of counterions from standard to hydrated ionic size. Furthermore, the quantitative characterization of the exchange of calcium for sodium at room temperature on Wyoming bentonite is investigated with the DFT modeling in aqueous solutions at pH 7.0. It is found that a significant variation of the selectivity coefficient could be observed with the surface charge density, ionic diameter and interlayer separations. This implies that ion selectivity in compacted bentonite differs from that in dilute smectite dispersions.

  • 37.
    Zazzi, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Jakobsson, Anna-Maria
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Ni(II) sorption on natural chlorite2012In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 27, no 6, p. 1189-1193Article in journal (Refereed)
    Abstract [en]

    Sorption of Ni(II) onto chlorite surfaces was studied as a function of pH (5-10), ionic strength (0.01-0.5 M) and Ni concentration (10(-8)-10(-6) M) in an Ar atmosphere using batch sorption with radioactive Ni-63 as tracer. Such studies are important since Ni(II) is one of the major activation products in spent nuclear fuel and sorption data on minerals such as chlorite are lacking. The sorption of Ni(II) onto chlorite was dependent on pH but not ionic strength, which indicates that the process primarily comprises sorption by surface complexation. The maximum sorption was at pH similar to 8(K-d = similar to 10(-3) cm(3)/g). Desorption studies over a period of 1-2 weeks involving replacement of the aqueous solution indicated a low degree of desorption. The acid-base properties of the chlorite mineral were determined by titration and described using a non-electrostatic surface complexation model in FITEQL. A 2-pK NEM model and three surface complexes, Chl_OHNi2+, Chl_OHNi(OH)(+) and Chl_OHNi(OH)(2), gave the best fit to the sorption results using FITEQL. The high K-d values and low degree of desorption observed indicate that under expected groundwater conditions, a large fraction of Ni(II) that is potentially leachable from spent nuclear fuel may be prevented from migrating by sorption onto chlorite surfaces.

  • 38.
    Zazzi, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Malmström, Maria E.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Dissolution rates and stoichiometry of two different chlorites as a function of pHManuscript (preprint) (Other academic)
  • 39.
    Zazzi, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Ni(II) Sorption on the Fracture Filling Mineral Chlorite2009In: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXXII, 2009, Vol. 1124, p. 531-536Conference paper (Refereed)
    Abstract [en]

    Abundance of the mineral chlorite as fracture filling material in granitic bedrock motivates sorption studies for quantification of the retention of radionuclides on this mineral. The activation product Ni-63 is an important component in spent nuclear fuel, accounting for a large contribution to the high activity level, and further motivates sorption studies of Ni on chlorite. Earlier sorption studies have been performed on larger mineral pieces; however, it is questionable if these data are representative for fracture filling material. Chlorite from a borehole core from Oskarshamn, Sweden, from the depth of 944 m has been characterized and the chemical composition determined prior to the experiments. The thickness of the fracture filling mineral is at maximum a couple of millimeters; therefore, careful removal of the thin chlorite layer from the core was performed with a carbide tool. The fraction was sieved to a size distribution of 63-118 mu m and ultrasonically washed. The major oxides were found to be 34.4 % SiO2, 21.6 % MgO, 15.4 % Al2O3 and 12.9 % Fe2O3 determined by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis. Sorption of Ni(II) to the sample was performed in 0.1 M NaClO4 with a batch technique inside a glove-box with Ar-atmosphere, using Ni-63 as a tracer with the Ni carrier concentration of 10(-6) and 10(-8) M. The percent sorption in these experiments was 57% at pH 5.5, 85 % at pH 6.5 and 92 % at pH 8.3, with the last value corresponding to maximum sorption No significant differences between the experiments performed in the two concentrations of 10(-6) and 10(-8) M were found. The degree of sorption on this fracture filling material is of the same magnitude as earlier studies of Ni sorption on chlorite provided from larger mineral pieces, using the same size fraction of the material. Sorption of Ni is, as expected, strongly pH dependent and Ni-63 escaping a breached canister will, reaching chlorite within the surrounding bedrock, be retarded due to strong sorption.

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