Student assignments

Information on student assignments with MST

Looking for an assignment? Please contact us for the possibilities at the Membrane Science & Technology cluster. Below are our vacant  student assignments. 


  • Metal-organic frameworks (MOFs) for specific ion selective membranes

    Metal-organic frameworks (MOFs) are a class of porous hybrid materials that are composed of coordinated metal atoms that are linked to each other via organic linker molecules.  This forms porous materials with pores in the order of magnitude of several Angstroms. This property makes MOFs interesting to use as a membrane to separate specific ions from each other, unlike conventional ion-exchange membranes which are primary based on charge-exclusion and show very limited ion-ion selectivity.

    Relatively recently, in the field of ion separations in water MOFs became of interest for specific water treatment that needs to target specific types of ions in water that also consists of other less interesting ions that do not need to be removed. Due to these small pore sizes, ions that are transported through the membrane have to dehydrate some shells of water to fit into the MOF pores. Therefore MOF based membranes can separate ions based on how easy they lose their water shells[1,3]. This makes it  possible for instance to recovery lithium ions selectively from a saline feed stream and it is possible to create a membrane that is more selective towards monovalent ions compared to multivalent ions (Cl- vs. SO4- or Na+ vs Mg2+) [1,2]. Furthermore it was found specifically for fluoride ions, that specifically bind fluoride to the MOF structure also enhanced the transport through a MOF membranes [3].

    In this project we will make MOF modified membranes and will characterize the membrane for instance with SEM and XRD. Furthermore we will analyze the modified ion transport through the MOF membrane with bi-ionic potential measurements and finally we can potentially test how well this membrane works in an electric-driven separation processes to separate specific ions. This project has industrial implications into developing new resource recovery processes in industry of valuable components, such as lithium from seawater.

    This assignment can be suitable for either bachelor or master students.

    If you’re interested and would like to know more about this project don’t hesitate to contact Harm Wiegerinck

    Email: h.t.m.wiegerinck@utwente.nl

    [1]:J. Lu et al. Efficient metal ion sieving in rectifying subnanochannels enabled by metal–organic frameworks. Nature Materials 2020 p. 767-774

    [2]: H. Zhang. Ultrafast selective transport of alkali metal ions in metal organic frameworks with subnanometer pores. Science Advances 2018 vol. 4 (2)

    [3]:X.Li.  Fast and selective fluoride ion conduction in sub-1-nanometer metal-organic framework channels. Nature Communications 2019 vol. 10 (1)

  • Effect of a temperature & concentration gradient on the transport of ions through ion selective porous media

    Previously, we have researched the influence of temperature gradients on the performance of electrodialysis experimentally [1,2] as well as numerically with a model system of ion selective nanochannels [3]. It was found that temperature differences can increase current at a given voltage (as expected from conductivity) and more interestingly that ion selectivity could be tuned based on these temperature differences due to variation in how the hydrated radius of ions change at different temperatures.

    However, in an electrodialysis process, the salt concentration changes along the length of the membrane due to the electrical field, which drives the ions through the ion-exchange membrane. Therefore, more fundamental research into the effect of temperature and concentration gradients  on the transport rate of ions through a membrane is necessary to exploit these effects.

    In this work, we plan to study ion and related transport phenomena through a bed packed with ion-exchange resin particles, while keeping the temperature gradient and concentration gradient nearly constant across the bed. Ion exchange resin particles are composed of  charged groups and therefore will preferentially allow the transport of counterions through the bed, while co-ions are retained by the ion exchange resin, which mimics a ion-exchange membrane. This setup allows to study the effect of concentration difference, electrical field strength, etc. on the rate of transport of different ions through porous ion exchange beds. This then has possible implications in how to improve industrially scale ion-exchange processes using low-grade waste heat.

    This assignment can be suitable for either bachelor and master students.

    If you’re interested and would like to know more about this project don’t hesitate to contact Harm Wiegerinck

    Email: h.t.m.wiegerinck@utwente.nl      

    [1]A. Benneker et al. Effect of temperature gradients in (reverse) electrodialysis in the Ohmic regime. Journal of Membrane Science 2018 pg.421-428

    [2]: A.Benneker et al. Influence of temperature gradients on mono- and divalent ion transport in electrodialysis at limiting currents. Desalination 2018 pg. 62-69

    [3] A. Benneker et al. Influence of temperature gradients on charge transport in asymmetric nanochannels. Physical Chemistry Chemical Physics 2017 vol. 19 (41)

  • Removal of micro-pollutants from wastewater with a hybrid biological and nanofiltration pilot

    What happens if you take a painkiller like paracetamol? Part of the substance will be used to indeed relieve your pain, but your body does not degrade the chemical completely. Therefore, you will excrete part of it and send that part to the sewage. Our current wastewater treatment plants are however not designed to remove all medicine like the painkillers, but also all kinds of other chemicals. These components are called organic micro-pollutants (OMPs) and lead to growing awareness and concern. OMPs have the potential to cause long-term harm to humans and the environment. Therefore, a novel nanofiltration membrane is developed that discharges very clean water from wastewater treatment plants, free from OMPs. A membrane however also creates a concentrate (waste stream) which contains elevated concentrations of OMPs, and needs to be treated. This project uses a unique pilot system at a scale of 1000 L/hr, with a recycle of the concentrate to a biological wastewater treatment system as depicted in the schematic overview. This biological treatment system is also part of the pilot. You can find pictures of the full installation below as well. In this assignment, you can investigate the total removal of OMPs as well as the general effect of the recirculation of concentrate on the system; what’s the effect of the concentrate on the biological activity and would it be possible to reuse the clean water for other purposes? Furthermore, you can optimize the operation of the membranes by changing the process conditions.

    Figure 1: schematic overview of the process with on the left a typical wastewater treatment plant, and at the right the membrane. The pilot plant will contain the full process as depicted here.

    Your tasks include:

    • Contributing to applied research by answering relevant research questions.
    • Ensuring smooth operation of the pilot plant, observing possible (operational) issues and solving them.
    • Analyzing the performance of the pilot plant by (1) taking samples & analyzing these samples yourself and (2) analyzing the data that the pilot plant will produce continuously.
    • Communicating about your findings with both involved universities (Wageningen University & Research and University of Twente) and companies (membrane producer NX Filtration, several water boards, technology supplier Nijhuis Industries).

    The assignment is suitable for students of universities and universities of applied sciences, for both internships and graduation assignments.

    You will have the opportunity to bring forward your own ideas to be implemented in the operation. We are looking for a student that can communicate well (preferably both in Dutch & English), is able to work independently and has a hands on, problem solving attitude. You will be working in Enschede, mainly at the wastewater treatment plant of Enschede and at the UT.

    If you have any questions about the assignment, please contact Hans David Wendt at  j.d.wendt@utwente.nl.

    Pictures: 1,2 = bioreactor, 3 = settler, 4 = nanofiltration


    (1)


    (2)



    (3)                                                                                         (4)