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  • 1.
    Danielsson, Carl-Ola
    KTH, Tidigare Institutioner, Mekanik.
    Continuous electropermutation using ion-exchange textile2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increased levels of nitrate in ground water has made many wells unsuitable as sources for drinking water. In this thesis an ion-exchange assisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. A new ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an continuous electropermutation cell. The ion-exchange textile have a high permeability and provides faster ion-exchange kinetics compared to ion-exchange resins. The sheet shaped structure of the textile makes it easy to incorporate into the cell. A report on the development of a new electro-membrane module, capable of incorporating an ion-exchange textile spacer, is presented. A theoretical study of the flow field through the electro-membrane module was performed using two different 2-D models. The calculated flow distributions provided by different proposed module designs were compared and a prototype module was produced. The flow field obtained with the prototype cell was visualised in a experimental cell with a transparent plexiglass cover. A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are presented and volume averaged to give macro-homogeneous equations. The model equations are analysed and relevant simplifications are motivated and introduced. The dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment. An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained

  • 2.
    Danielsson, Carl-Ola
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Electropermutation assisted by ion-exchange textile: removal of nitrate from drinking water2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increased levels of nitrate in ground water have made many wells unsuitable as sources for drinking water. In this thesis an ion-exchang eassisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. An ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an electropermutation cell. The sheet shaped structure of the textile makes it easy to incorporate into the cell. High permeability and fast ion-exchange kinetics, compared to ion-exchange resins, are other attractive features of the ion-exchange textile.

    A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are volume averaged to give macro-homogeneous equations. The model equations are analyzed and relevant simplifications are motivated and introduced. Dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment.

    An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained.

    Enhanced water dissociation is known to take place at the surface of ion-exchange membranes in electromembrane processes operated above the limiting current density. A model for this enhanced water dissociation in presented in the thesis. The model makes it possible to incorporate the effect of water dissociation as a heterogeneous surface reaction. Results from simulations of electropermutation with and without ion-exchange textile incorporated are presented. The influence of the water dissociation is investigated with the developed model.

  • 3. Danielsson, Carl-Ola
    et al.
    Dahlkild, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Velin, Anna
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    A Model for the Enhanced Water Dissociation On Monopolar Membranes2009Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 11, s. 2983-2991Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model for the enhanced water dissociation that takes place at the solution/membrane interface in electromembrane processes is presented. The mechanisms behind the enhanced water dissociation are poorly understood and therefore a semi-empirical approach is suggested. The enhanced water dissociation is introduced as a heterogeneous surface reaction similar to the well established Butler–Volmer law for electrode reactions. In the model there are two parameters that need to be determined through experiments. A 1D diffusion boundary layer problem is presented and solved in order to show that a sufficient rate of water dissociation can be obtained with the model. The advantage of the presented model is that it can easily be incorporated into simulations of electromembrane processes such as electrodialysis, electrodeionization and electropermutation. The influence of the enhanced water dissociation on these processes can then be studied.

  • 4. Danielsson, Carl-Ola
    et al.
    Dahlkild, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Velin, Anna
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Modeling Continuous Electropermutation with Effects of Water Dissociation Included2010Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 56, nr 9, s. 2455-2467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The repeating unit consisting of a cell pair of one concentrate and one feed compartment of an electropermutation stack is modeled. Both the feed and the concentrate compartments are filled with an ion-exchange textile material. Enhanced water dissociation taking place at the surface of the membrane is included in the model as a hetrogeneous surface reaction. Results from simulations of nitrate removal for drinking water production are presented and comparisons with previous experimental results are made. The influence of both conductive and inert textile spacers on the process is investigated via simulations

  • 5.
    Danielsson, Carl-Ola
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Dahlkild, Anders
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Velin, Anna
    Behm, Mårten
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile: I. Modeling2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, nr 4, s. D51-D61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a steady-state model of the feed compartment of an electropermutation cell, used for nitrate removal, with ion exchange textiles incorporated as a conducting spacer. In the model the ion-exchange textile is treated as a porous medium and volume averaging is applied to obtain a macrohomogeneous two-phase model. The ion-exchange between the two phases is modeled assuming that the rate-determining step is the mass-transfer resistance on the liquid side of the phase interface. Analysis of the model equations reveals appropriate simplifications. The influence of the governing dimensionless numbers is investigated through simulations based on the model.

  • 6.
    Danielsson, Carl-Ola
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Velin, Anna
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Dahlkild, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile: II. Experimental Investigation2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, nr 4, s. D62-D67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water with nitrate concentrations above 100 ppm has been treated with continuous electropermutation which partially substitutes the nitrate with chloride. The performance of a textile anion exchanger as conducting spacer in the feed compartment of an electropermutation cell was investigated. Experiments with and without textile are compared and the influence of the textile is discussed. The process could, using the textile, successfully treat feed water with 105 ppm nitrate to produce a water with less than 25 ppm nitrate. The importance of establishing a good contact between the membranes and the textile spacer was pointed out. The experimental results were compared to model predictions and a good agreement was found.

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