čas: 21.4.2021 19:29:40
Obnovit | RAW
KU Leuven, Belgium
List of available PhD theses
Characterization and modelling of dispersion systems with variable viscosity
The goal of this project is to characterize and model systems where viscosity of the dispersed phase is rising during the process. Typical examples are emulsification, suspension polymerization or spherical agglomeration. The student will start with simplified system composed of two liquid phases with various viscosities, which will be analyzed by on-line sensors providing information about the droplets sizes. Experimental activity will cover both batch as well as continuous operation modes. Collected data will be consequently used to develop engineering model based on computational fluid dynamic of the fluid flow coupled with population balances to describe coalescence and breakup of dispersed phase for various levels of dispersed phase viscosity. An extension of this activity will be process of spherical agglomeration where dispersed phase will contain particles (nanoparticles or crystals), which can undergo agglomeration and thus increasing the viscosity of the dispersed phase. Developed model will be validated against experimental data collected at various scales or operating conditions.
New effective separation membranes for water and wastewater treatment based on hybrid carbon-based materials
Current membrane separation processes allow efficient purification and physical disinfection of water from undesirable components on the basis of a size-sieving mechanism without the need for chemical agents. The pore sizes and their distribution on the membrane surface is an important factor for the effective removal of contaminants and microorganisms. The thesis will study the possibilities of using newly prepared membrane materials based on carbon materials (carbon nanotubes, graphene derivatives, etc.) with targeted surface modifications (eg doping with antimicrobial agents, etc.) in order to effectively remove collected contaminants from water. In addition to the preparation, characterization and testing of materials, the work will also include modelling of the separation process. The result of this work will be, besides the preparation of an effective separation material and describing the model, an extension of knowledge in the given membrane field.
Polymer-based membranes for highly selective removal of CO2 from biogas
Membrane-based gas separation technology has contributed significantly to the development of energy-efficient systems for natural gas purification. Also CO2 removal from biogas, with CO2 contents exceeding 40% has more recently known rapid growth and development. Major challenge of polymer membranes for gas separation is related to their susceptibility to plasticization at high CO2 partial pressures. CO2 excessively swells the polymer and eases the permeation of CH4, thus reducing the selectivity. Membrane crosslinking is one of the best ways to prevent the plasticization. Mixed matrix membranes (MMMs), consisting of fillers homogeneously dispersed in a polymeric matrix aim at combining the processibility of polymers and the superior separation properties of the porous fillers. Metal-organic frameworks (MOFs) are such materials which have attracted considerable attention due to their tailorable functionality, well-defined pore size, pore tunability and breathing effects. MMMs for biogas upgrading will be prepared with increased permeabilities by choosing proper MOF/polymer combinations and modifying the thermal treatment, employing core-shell MOF materials with high bulk porosity and a selective shell layer.
Solvent and pH stable membranes with ultra-sharp molecular weight cut-off values
Membrane-based separations currently offer the best strategy to decrease energy requirements and environmental footprint through newly developed solvent resistant nanofiltration (SRNF) or solvent-tolerant nanofiltration (STNF). So-called solvent activation of polymeric membranes involves treatment of an existing membrane by contacting it with solvents or solvent mixtures, which is hypothesized to restructure the membrane polymer through solvatation, increase polymer chain flexibility and organization into suitable structures. This will be verified by systematically treating membranes with different solvents and testing them for the separation of synthetic liquid streams. A high-throughput set-up will be used. Fundamental physico-chemical characterisations of the membranes before and after the treatments will provide insight in the changes at molecular level. The characterization techniques include gas and liquid uptake experiments (diffusivity), PALS (positron annihilation lifetime spectroscopy, to determine free volume element distributions), ERD (elastic recoil scattering, providing elemental analysis in membrane depth profiles), solid state NMR (nuclear magnetic resonance), TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry).
Tailoring of nanostructure in mixed matrix membranes for selective removal of CO2 from biogas
Membrane separation processes belong to modern technologically important separation methods, which are less demanding (economically and ecologically) in comparison with classical separation methods. For the gas separation applications, mainly polymer membranes are used. Their performance (permeability or separation effect) can be additionally adjusted by the targeted embedding of liquid or solid additives into the polymer matrix. The dissertation thesis will focus on the preparation, characterization, and testing of the so-called mixed matrix membranes for the separation of gases based on glassy polymers and functional nano-additives with a purposefully prepared structure. In addition, modeling of the separation process will be part of the work. The result of this work will be prepared and tested membrane material for the effective removal of CO2 from biogas and extension of knowledge in the given membrane field.