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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. 


Preparation and characterization of new pH stable nanofiltration membranes prepared by interfacial polymerization (MSc or BSc assignment)

Project Scope

Nanofiltration membranes are used in a wide variety of industries. Advantages such as low energy cost, ease of application, operation at moderate conditions and no extra waste streams, makes that membrane technology can offer both economic and ecologic benefits. However, the insufficient stability of the membranes currently limits their application in extreme industrial conditions such as at extreme pH values, in e.g. the mining, textile or dairy industry. 

For extreme pH conditions (i.e. below 2 and above 12.5), only a few membranes are available, and often they have inadequate stability, low flux/rejection making them unsuitable for large-scale implementation.

In this project, we try to develop new polymeric nanofiltration membranes, which tackle the currently existing shortcoming of commercial membranes.

The technique used for preparing the membranes is interfacial polymerization. A thin selective toplayer is formed on a porous support (figure 1) by reacting two monomers at the interface of two immiscible phases (figure 2).

Your task:

During this research you will focus on the development and characterization of nanofiltration membranes. You will focus on the exploration of new chemistries, leading to pH stable membranes (inspired by the work of Kah Peng Lee 3,4). You will test the potential of several monomer combinations for its film formation and its use as selective layer on pH stable membranes. The prepared films and membranes will be characterized by means of a.o. FTIR, SEM, zeta potential, clean water flux, salt retention, MWCO and stability tests in extreme pH.

Contact:

If you are interested to work on this topic or if you want more information, please contact Mariël Elshof (m.g.elshof@utwente.nl), Films in Fluids, ME236B.

Reference:

  1. Dalwani, M. Thin film composite nanofiltration membranes for extreme conditions. Ph.D.Thesis (2011).
  2. Raaijmakers, M. J. T. & Benes, N. E. Current trends in interfacial polymerization chemistry. Prog. Polym. Sci. 63, 86–142 (2016).
  3. Lee, K. P., Zheng, J., Bargeman, G., Kemperman, A. J. B. & Benes, N. E. pH stable thin film composite polyamine nanofiltration membranes by interfacial polymerisation. J. Memb. Sci. 478, 75–84 (2015).
  4. Lee, K. P., Bargeman, G., de Rooij, R., Kemperman, A. J. B. & Benes, N. E. Interfacial polymerization of cyanuric chloride and monomeric amines: pH resistant thin film composite polyamine nanofiltration membranes. J. Memb. Sci. 523, 487–496 (2017).
Ion transport through graphene (MSc assignment)

Graphene is increasingly studied as a potential material for membrane applications. It does not have any separation capability in its pristine state, however a perforated monolayer graphene membrane can selectively separate material due to steric or electrostatic exclusion [1, 2].  In our work, we use ion-bombarded perforated monolayer graphene membrane supported on a polymer foil to study diffusional ion transport properties through graphene [3]. This membrane allows positive ions to pass through and blocks negative ions, acting as a cation-exchange membrane (CEM). We have studied the selectivity of the membrane with varying concentrations from range where Donnan potential dominates to concentrations where the diffusion potential dominates and the membrane loses all its selectivity. We have also analyzed our experimental results with theory, based on Donnan equilibrium and the Teorell, Mayer and Sievers (TMS) theory.  

 

So far, we have done our measurements without applying any electric field across the membrane and the observations are based on diffusional ion transport. Now, we need to explore how the ions transport through the membrane when an electric field is applied across the membrane. The aim of the current master’s project is to study the ion transport behaviour of the graphene membrane with the application of electric field. Also, in the later part of the project the ion transport will be studied with varying number of pores in the membrane. Finally, the experimental result will be validated with theoretical understanding.  

For more information, feel free to contact Madakranta (Dona) Ghosh:
m.ghosh@utwente.nl

[1] O’Hern et al. “Selective Ionic Transport through Tunable Subnanometer Pores in Single-Layer Graphene Membranes.” Nano Lett. 2014, 1234-1241

[2] Rollings et al. “Ion selectivity of graphene nanopores” Nature Comm., 2016, 7, 11408

[3] Madauß et al. “Fabrication of nanoporous graphene/polymer composite membranes” Nanoscale, 2017, 9, 10487

Theoretical Investigation of Electroforming MOFs on Copper Hollow Fibers (MSc assignment)

Recently in the Films in Fluids group a novel technique for producing highly controllable hollow fibres using an environmentally friendly ionic-gelation technique has been developed. Through the addition of nanoparticles, metallic oxide or metallic hollow fibres can be easily fabricated. Using this technique, the FiF group has pursued the intriguing idea of utilizing this simple fibre production technique in order to fabricate copper-based metal organic frameworks (MOFs). MOFs are metal-ions which are coordinated to organic ligands, forming network structures (1d, 2d or 3d) that can be porous. MOFs are of potential interest in catalysis, sensing and gas separation and having the capacity to form high specific surface area hollow fibres is an attractive option for making use of the unique MOF properties.

Research has been carried out in fabricating Cu(BTC) using an electrochemical synthesis method. In this approach, a Cu hollow-fibre is used as the working electrode in a cell containing an ethanol-water mixture containing an organic ligand - trimesic acid (BTC). BTC then reacts with copper to form Cu-BTC, a copper-hollow fibre MOF. The underlying mechanism behind this transformation and its enhancement using applied potential has been postulated but not confirmed.

It is the goal of this proposed Masters assignment to develop a theoretical model to understand this system, which we are presently investigating experimentally. This model framework can then be implemented in a 2 or 3d numerical simulation (COMSOL) in order to predict or fit experimental results. For example, what is the role of the electric-field distribution within the system, ion dissociation in the water-ethanol mixture, etc. This will greatly aid in understanding of the potential of this approach for synthesis of MOF hollow-fibres and its potential applicability at larger scales.

For more information, please contact:

Özlem Haval Demirel (o.h.demirel@utwente.nl), Films in Fluids, Meander 322

Jeff Wood (j.a.wood@utwente.nl), Soft Matter, Fluidics and Interfaces, Meander 313

[1] Schäfer et al. Unraveling a two-step oxidation mechanism in electrochemical Cu-MOF synthesis. Chem. Comm. 2016. 52: 4722

Diffusioosmotic flow for enhancing conversion (MSc assignment)

Many heterogeneous systems have mass transfer limitations near the solid-liquid interface. These limitations in the boundary layer are due to fast reaction at the wall, creating a concentration drop towards the solid. Or it could be from the velocity which is standing still near the wall due to a laminar, parabolic flow pattern in the microchannel. The main focus of this project is to overcome this mass transfer limitation by creating an osmotic flow near the solid-liquid interface in the boundary layer.

An osmotic flow is created by a pressure gradient in the liquid, which is directly proportional to the concentration gradient for non-electrolytes and to the natural logarithm of the concentration gradient for electrolytes [1]. The concentration gradient is created by the interaction between the liquid particles and solid interface, which can be repulsive or attractive. If different solid interfaces are used, alternating each other, a continuous osmotic flow can be created. This is schematically shown in the figure below.

This project can be approached both numerically and experimentally. Optimal conditions need to be found for maximal diffusioosmotic flow in the boundary layer in order to enhance the conversion as much as possible. Design parameter would be for example flow velocity, organic compound to degrade, and length of the titanium dioxide patch. 

Please do not hesitate to contact Nicole Timmerhuis for more information! (n.a.b.timmerhuis@utwente.nl)

[1] D.C. Prieve, J.L. Anderson, J.P. Ebel, M.E. Lowell, J. Fluid. Mech., 148:247-269, 1984

Catalytically Induced Convective Flow

The electrochemical decomposition of hydrogen peroxide  has been reported to generate interfacial fluid flow by micro-pumps, and interdigitated microelectrodes[1], as well as the motion of bimetallic platinum/gold nano-motors [2]. In principle, the immersion of platinum/gold nanorods in hydrogen peroxide, triggers a series of oxidation and reduction reactions, where  is oxidized at the platinum anode into protons, electrons, and oxygen molecules, while reduction takes place at the gold cathode. The resulting ionic flux generates an electric field that is coupled with the charge density, thereby inducing an electric body force that drives interfacial fluid motion.The heterogeneous rate constant which largely influences ionic flux by way of proton generation and consumption is an important parameter that needs to be understood under steady state and transient conditions.

The kochi and Kolinger’s approach [3] will be used in determining the reaction rate constant. Several electrochemical experimental techniques such as chronoamperometry, chronopotentiometry and cyclic voltammetry, will be used in determining important parameters such as, diffusion coefficient, charge transfer, number of electrons, and peak potentials needed for evaluating the rate constant. The experimental heterogenous rate constant will be implemented in existing numerical models by way of the Damköhler’s number to ascertain its influence on the reaction flux, proton distribution, induced potential and convective flow.

For more information, contact:

Abimbola ASHAJU (a.a.ashaju@utwente.nl), Soft Matter, Fluidics and Interfaces, Meander 317)

[1]          T. R. Kline, W. F. Paxton, Y. Wang, D. Velegol, T. E. Mallouk, and A. Sen, “Catalytic micropumps: Microscopic convective fluid flow and pattern formation,” J. Am. Chem. Soc., vol. 127, no. 49, pp. 17150–17151, 2005.

[2]          T. R. Kline, W. F. Paxton, T. E. Mallouk, and A. Sen, “Catalytic Nanomotors: Remote-Controlled Autonomous Movement of Striped Metallic Nanorods**,” pp. 744–746, 2005.

[3]          R. J. Klingler and J. K. Kochi, “Electron-transfer kinetics from cyclic voltammetry. Quantitative description of electrochemical reversibility,” J. Phys. Chem., vol. 85, no. 12, pp. 1731–1741, 1981.

Multicomponent nanofiltration modeling

Nanofiltration membranes are commonly employed in industrial practice for separations of molecular species while working at relative low operation pressures. The unique property of these membranes is that they allow passage of certain solutes, while they can retain others. This makes nanofiltration a cost-effective step in the separation or purification of several streams. This can for instance be drinking water production, or resource recovery from waste streams. For an effective process, it is essential to understand the transport of the different solutes to and through the membrane. 

One observed non-ideality is the emergence of non-intuitive phenomena, such as negative retention of solutes (the permeate of a process is more concentrated than the retentate). This is, in particular, more common in mixture systems due to the fascinating non-ideal thermodynamics involved and has important consequences in the design and operation of membrane processes for separations. Building a model framework that can capture these effects and understand the role of mixture interactions in a simple manner is therefore of crucial importance.

In this assignment, you will work to build and compare multicomponent mass transfer models and compare the role of choosing an effective mixture thermo-dynamics rule + model framework in describing experimental data for hollow fiber filtration. The aim is to be able to describe industrially relevant hollow fiber filtration data obtained from actual membrane filtration experiments. The assignment will be performed at the UT in close collaboration with an industrial partner (NX Filtration).

For more information please contact Jeff Wood (j.a.wood@utwente.nl) or Joris de Grooth (j.degrooth@utwente.nl)

Future generation membranes by Aqueous Phase Separation

Elif Nur Durmaz (1), Wouter Nielen(1), Joshua Willott  (1), Wiebe de Vos(1)

(1)Membrane Surface Science (MSuS), Membrane Science and Technology Cluster

Project Outline

Membranes are used in a variety of processes including the production of clean drinking water, artificial kidneys, CO2 capture, and food processing. Due to their large application areas and many advantages of membranes over other separation technologies, the membrane market is continuously growing. However, a major concern regarding membrane production is the use of large quantities of aprotic organic solvents such as N-Methyl-2-pyrrolidone. Such solvents are harmful to humans and the environment. This project is focused on investigating a novel, environmentally friendly technique for the production of membranes without using organic solvents. Here, membrane formation relies on the phase separation of polyelectrolytes either through a pH switch or a complexation with an oppositely charged polyelectrolyte. The main aim is to understand which factors govern the morphology and separation performance of the membranes. Additionally, improving mechanical and chemical stability with cross-linking will be investigated.

     

Figure 1 - Porous symmetric and porous asymmetric structure of membranes obtained by tuning conditions of the aqueous phase separation

Project Description

Polyelectrolytes are polymers that contain repeating charged groups. Due to these charges, they are soluble in polar solvents like water. Polyelectrolytes can be separated into two categories based on the charged groups. 1. Weak: when their charge depends on the pH of the medium or 2. Strong: when the charge is independent of pH. Weak polyelectrolytes can be used to precipitate a hydrophobic polyelectrolyte from water by shifting to a pH where the polyelectrolyte is uncharged.  Alternatively, this can also be used to charge an uncharged hydrophilic weak polyelectrolyte. When this is mixed with an oppositely charged strong polyelectrolyte, they form a complex, which can be solid. In both cases, a phase separation occurs and under the right conditions, this can be used to form a porous, asymmetric membrane. By controlling the rate at which the polyelectrolyte is charged or uncharged the kinetics of the phase separation can be controlled which in turn gives control over the structure of the precipitate that is formed. This allows us to fabricate membranes with controllable properties. To fine-tune membrane performance e.g. membrane flux or retention, additives can be used. Additionally, the mechanical and chemical stability can be significantly improved with cross-linking. To assess the membrane performance several filtration techniques are used. In addition, the morphology is imaged using scanning electron microscopy. The membrane can then be optimized towards specific applications, such as gas-separation, ion removal or the treatment of oily wastewater.

Project Outcome

This project is expected to lead to a new and sustainable approach to produce membranes. Moreover, the newly produced membranes are expected to have unique separation properties relevant to a number of applications.

Membranes by Aqueous Phase Separation (APS): Effect of monomer molecular weight on the membrane properties

Muhammad Irshad Baig(1), Wiebe M. de Vos(1)

(1)Membrane Surface Science,  Membrane Science and Technology Cluster, MESA+ Institute for Nanotechnology, University of Twente, Faculty of Science and Technology, P.O. Box 217, 7500 AE, Enschede, The Netherlands.

m.i.baig@utwente.nl ; w.m.devos@utwente.nl

Project Background

A membrane is  a barrier that regulates the flow of species in a selective way. The most commonly used membranes in water purification and gas separation applications are made from polymers that are only soluble in organic solvents. Ask anyone who works in the field of polymeric membranes about its fabrication procedure, and you will mostly hear one answer i.e. NIPS. It stands for Non-solvent Induced Phase Separation. Simply put, you take a polymer (Polysulfone, Polyimides for example) and dissolve it in an organic solvent such as N-methyl-2-pyrrolidone (NMP). When the solution is homogeneously mixed, it is then cast on a flat surface and put in a water bath. The solvent (NMP) is highly miscible in water and so it leaves the polymer solution and mixes with water. The polymer, at this point, becomes insoluble due to all the water that is around it, forming a solid porous membrane. The membranes prepared in this way are also known as ‘Loeb-Sourirajan Membranes (L-S membranes)’, named after the researchers who first made asymmetric cellulose acetate membranes for seawater desalination.

This simple procedure of making commercial polymer membranes has remained the same since the 1970s. NMP is by far the most widely used solvent to prepare membranes and the multi-billion dollars membrane industry uses this solvent in immense amounts.

However, NMP is not a friendly chemical by any means. It is partly flammable, and most importantly, it has been proven to be repro-toxic to humans and harmful for the environment.1 Therefore, it has to be recycled and/or removed from waste streams plus it has to be removed from the membranes before they can be utilized for water production. The EU has introduced a law that restricts the use of such chemicals throughout the Union.2 

Having discussed the nature of aprotic, polar organic solvents and their harmful effects, we have an alternative solution which uses only water as a solvent. It is extremely difficult and almost impossible to dissolve conventional polymers in water. This leaves us with a special class of polymers called ‘Polyelectrolytes’ which can be easily dissolved in water. These polyelectrolytes are charged polymers with a unique property that their charge can be manipulated by a pH switch. Some polyelectrolytes are only charged below a particular pH. They are called weak polyelectrolytes. On the other hand, certain polyelectrolytes remain charged in almost all the pH range. These are called strong polyelectrolytes. When the two oppositely charged polyelectrolytes come across each other, they instantly form a ‘Polyelectrolyte Complex’. So if we make a homogeneous solution of these two polyelectrolytes such that they are uncharged in the solution and then cast it in a water bath with a pH where both become charged, we get a polyelectrolyte complex membrane. This novel approach to making membranes is termed ‘Aqueous Phase Separation’ (APS). 

Project Details and Outcome

In this project, Poly(sodium 4-styrenesulfonate) and Poly(allylamine hydrochloride) will be used as strong and weak polyelectrolytes, respectively. The aim of this study would be to investigate the effect of the monomer molecular weight on the final membrane properties. During the course of the project, the effect of pH and salt concentration of coagulation bath would also be investigated in detail. Monomer molecular weight is a very important factor that determines the final structure and properties of the membrane. A low molecular weight polyelectrolyte usually results in an open structure (porous) membrane with water fluxes that are in the range of Microfiltration and Ultrafiltration. However, this is not the only control parameter. Coagulation bath pH and the salt concentration in the bath are one of the most crucial parameters as well. In this project, all these effects will be studied to have a better understanding of APS.

Figure 1. Schematic illustration of polyelectrolyte complexation induced by a pH switch.

The membranes prepared in this study will be used for water treatment and purification. The applications are as diverse as the new APS field itself. From oil/water separation (Microfiltration) to seawater desalination (nanofiltration and reverse osmosis), the outcomes of this study are diverse.

It is important to mention here that one of the inventors of L-S membranes, Loeb Sidney, was an MSc. student at UCLA when he got the breakthrough in membrane science and technology. Similarly, this project, part of a larger research goal, will play an important role in shaping the next generation of polyelectrolyte membranes.

References

  1. D. Prat, J. Hayler and A. Wells, Green Chem., 2014, 16, 4546–4551.
  2. L. Bergkamp and N. Herbatschek, Rev. Eur. Comp. Int. Environ. Law, 2014, 23, 221–245.
Polyelectrolytes for an improved aquaporin embedded top layer for next generation forward osmosis membranes (MSc assignment)

Dennis Reurink(1), Wiebe M. de Vos (1)

(1)Membrane Surface Science (MSuS)

Introduction

An emerging separation and desalination technology that shows great potential is forward osmosis (FO). FO uses osmotic pressure gradients to transport water across a semipermeable membrane. These membranes are usually based on reverse osmosis (RO) membranes, which lack, however, suitability for FO applications [1]. A way to create new membranes truly optimized for FO, is by incorporating aquaporin containing vesicles (AQPVs) in the separating layer [2]. These vesicles have the aquaporin protein incorporating in the vesicle wall as shown in Figure 1. This aquaporin protein acts as a water channel that allows solely water and block all other solutes [3]. In this way the permeation and rejection properties are enhanced.

Another versatile technique is the self-assembly of oppositely charged polyelectrolytes (PEs) on the surface of a porous support membrane. In this so-called Layer-by-Layer (LbL) assembly, the support membrane is alternatively exposed to polycations and polyanions [4]. Such a PEM coating is easily applied on all geometries. In this study, the focus will be on making a PEM coating with the incorporation of AQPVs. Since the interaction between the vesicles and the multilayer is important, the distribution of the AQPVs is first studied. Subsequently, a layer will be produced and tested on its FO and RO performance.

Study

In order to create a more permeable and selective layer, aquaporin containing vesicles (AQPVs) can be used. These vesicles are incorporated in the separating layer of the membrane.

In order to control the distribution of the aquaporin vesicle, various polyelectrolytes can be used which have different interaction with the AQPVs. Also different coating environments, like salt concentration, pH, and solvent can be used to control the distribution of the vesicles.

In this MSc project, the distribution of the AQPVs will be studied on model surfaces. When the distribution is controlled and understood a separating layer will be made and incorporated on a membrane.

Methods

PEMs can be made by dip-coating silicon wafers or membranes in a solution containing a certain polyelectrolyte. AQPVs can be also be coated by means of dip-coating.

The distribution of AQPVs can be seen with a high resolution scanning electron microscope. Adsorption of both the PEs and AQPVs are measured with reflectometry and further characterization can be done with ellipsometry, zeta potential, and contact angle measurements. The knowledge obtained from model surfaces (silicon wafers) will be translated into hollow fiber membranes. The membranes will be coated under the same conditions as the model surfaces and will be tested on their performances in forward and reverse osmosis operating conditions.

Figure 1: The water-selective aquaporin protein incorporated in the vesicle wall.

References

1. Shaffer, D.L., et al., Forward osmosis: Where are we now?, Desalination, 2015. 356.

2. Tang, C., et al., Biomimetic aquaporin membranes coming of age, Desalination, 2015. 368.

3. Murata, K., et al., Structural determinants of water permeation through aquaporin-1, Nature, 2000. 407(6804).

4. Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites, Science, 1997. 277(5330).

Polyelectrolytes for new generation reverse osmosis hollow fiber membranes (MSc assignment)

Dennis Reurink (1), Wiebe M. de Vos (1)

(1)Membrane Surface Science (MSuS)

Introduction

Nowadays most membranes for nanofiltration (NF) and reverse osmosis (RO) are based on thin film composite (TFC) membranes. On a TFC membrane, a thin film is coated on a porous support with interfacial polymerization. A major disadvantage is that defect free hollow fiber membranes based on the TFC principle is merely impossible [1]. A new versatile technique for membrane the self-assembly of oppositely charged polyelectrolytes (PEs) on the surface of a porous ultrafiltration support membrane. In this so-called Layer-by-Layer (LbL) assembly, the support membrane is alternatively exposed to polycations and polyanions [2]. Such a polyelectrolyte multilayer (PEM) coating is easily applied on all geometries. In this study, the focus will be to create a PEM based membrane suitable for RO applications. In order to achieve RO performance, PEMs should be made as dense as possible by means of crosslinking and the use of different kinds of PEs. Subsequently, the layer will be characterized and tested on its RO performance.

Study

Creating more intrinsic bonds will increase the rejection properties of an active membrane layer. Crosslinking is a manner to create more intrinsic bonds and can easily be done by heat or a catalyst. Many moieties of PEs are amines or carboxylic acids which can easily be crosslinked, as shown in Figure 1.

Crosslinking of PEMs has already shown to be a promising way to create an active layer capable of retaining salts [3]. For FO purposes, the layer has to be as dense as possible in order to cope with highly concentrated saline streams. In order to control the layer density, different materials can be used that influence the intermolecular distance.

In this MSc project, different types of crosslinking techniques and materials will be evaluated. Materials will vary from aliphatic, branched, to aromatic structures while controlling and monitoring the performance of the membrane. 

Methods

PEMs can be made by dip-coating silicon wafers or membranes in a solution containing a certain polyelectrolyte. The growth and properties of these multilayers can be monitored by using techniques like reflectometry, ellipsometry, contact angle, and zeta potential measurements. 

Crosslinking can be done catalyzed or non-catalyzed. Non-catalyzed reactions take place under the influence of heat. To see if crosslinking has taken place, the layer will be characterized by, e.g., FTIR measurements.

The knowledge obtained from model surfaces (silicon wafers) will be translated into hollow fiber membranes. The membranes will be coated and crosslinked under the same conditions as the model surfaces and will be tested on their performances in forward osmosis operating conditions.

Figure 1: Crosslinking of polyelectrolyte multilayers [4].

References

1. Lau, W.J., et al., A recent progress in thin film composite membrane: A review, Desalination, 2012. 287.

2. Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites, Science, 1997. 277(5330).

3.  Park, J., et al., Desalination membranes from pH-controlled and thermally-crosslinked layer-by-layer assembled multilayers, Journal of Materials Chemistry, 2010. 20(11).

4.  Sullivan, D.M. and M.L. Bruening, Ultrathin, cross-linked polyimide pervaporation membranes prepared from polyelectrolyte multilayers, Journal of Membrane Science, 2005. 248(1-2).

Studying the nanoscale properties of polymer brush coatings with different architectures

Joshua Willott (1), Wiebe M. de Vos (1)

 (1) Membrane Surface Science (MSuS)

Project Outline

Solid surfaces coated with water-soluble stimuli-responsive polymers (specifically end-tethered brushes) exhibit many diverse macroscopic behaviors such as tuneable wettability and lubrication. For these promising coatings to be applied in ‘real world’ scenarios their nanoscale properties (solvation, charge state, thickness) and how they response to stimuli (pH, temperature, salt) and stresses (confinement, added foulants like surfactants, particles) must be very well understood.

The scope of this project encompasses designing specific polymer architectures to control the responsive nature of end-tethered polymer layers. Recently, it has been shown that polydispersity within such layers can be used to control its thickness response. However, this is difficult to achieve synthetically, and something that can be easier to control is polymer architecture. The polymeric layers will be designed and then studied using numerical self-consistent field theory (Willott et al. 2018, Macromolecules 51, 1198-1206 and Langmuir, 2019, 35, 2709-2718) with comparisons made to experimental observations.

 

Project Description

In this project, you will work to investigate how the architecture (molecular structure) of end-tethered polymer chains (e.g. linear, star, comb, dendrimer) changes their solution behaviour. The polymer response to stimuli including temperature, pH, salt concentration and salt type will also be studied by changing the type of monomers (or segments) and the solvent. Preliminary work shows that architecture is a control parameter for brush behaviour as shown in Figure 1 where linear and comb polymers are compared. Figure 1 also shows that behaviour depends on which sections within the brush contain the responsive monomers.

Figure 1. Thickness response of the polymer layer as a function of chi parameter (proportional to temperature) for linear vs. comb polymer architectures.

Thin film composite (TFC) membranes for organic solvent nanofiltration (BSc or MSc assignment)

 1.     Project description 

The invention of thin film composite (TFC) membranes has revolutionized the desalination industry. It not only lowers the price of fresh water, but also improves the quality of clean water. A typical TFC membrane consists of two different layers, a selective layer on top and a porous substrate underneath. The selective layer is commonly made from conventional interfacial polymerization, coating or layer-by-layer method while the substrate is a ultrafiltration membrane. The main advantage of TFC membranes is that one can manipulate both layers separately in such a way to produce a highly permeable and selective membrane.

Despite all the advantage of membrane based separations, their application in petrochemical and pharmaceutical industries are still limited because most separations in these industries involve organic solvents or extreme pH, where conventional polymer membranes fail to operate. Therefore, design and fabrication of chemically stable TFC membranes with great mechanical and thermal stabilities are highly demanded for sustainable manufacturing in chemical and pharmaceutical industries.

In this project we are looking into developing novel and highly stable selective layers, while a commercially available substrate would be used for the substrate. The newly developed membranes would be tested under harsh/real industrial conditions. This include organic solvents and acidic solutions.

2.    Your tasks 

  • TFC membrane synthesis
  • Operation of dead-end filtration systems. 
  • Membrane characterizations such as FESEM, FTIR, etc.

 3.    Your profile 

  • Specialized in environmental/chemical engineering, chemistry or related areas.
  • Actively enrolled in undergraduate (BSc) or graduate (MSc) studies 
  • An interest for practical laboratory experience.
  • Fluent in English language (speaking, writing and communication skills) 

Duration of the project: 6-9 months

4.     How to apply 

Interested students are invited to contact Akbar Asadi Tashvigh (a.asaditashvigh@utwente.nl) for more details.

 

[1]. Asadi Tashvigh, A., et al., 110th Anniversary: Selection of Cross-Linkers and Cross-Linking Procedures for the Fabrication of Solvent-Resistant Nanofiltration Membranes: A Review. Industrial & Engineering Chemistry Research, 2019. 58(25): p. 10678-10691.

[2]. Asadi Tashvigh, A. and T. S. Chung, Facile fabrication of solvent resistant thin film composite membranes by interfacial crosslinking reaction between polyethylenimine and dibromo-p-xylene on polybenzimidazole substrates. Journal of Membrane Science, 2018. 560: p. 115-124.

Development of supported thin film membranes for hydrogen separation (MSc assignment)

Announcing Institution: Forschungszentrum Jülich GmbH, IEK-1 – Materials Synthesis and Processing and University of Twente – Electrochemistry Research Group

Starting date: anytime, Duration: 7 Months

Field of activity: The energy supply in Europe has changed in the past few decades from conventional technologies (fossil, nuclear) to more renewables (solar, wind) and the process is still going on. This leads to a high fluctuation of the energy supply and to times of over- and undercapacity. To ensure a sustainable and environmental friendly energy supply for the future, carbon capture technologies are necessary to reduce CO2 emissions, and energy storage is needed to cover periods of low energy generation by renewables. The development of new batteries or the production of synthetic fuels is urgently required for energy storage.

Oxide ceramic membranes for the separation of oxygen or hydrogen from gas mixtures are of great interest for different applications due to their high efficiency and practically infinite selectivity. Supported membrane structures are envisaged for applications in oxygen and hydrogen generation for the corresponding gas supply, for example in power plants, glass, cement or steel production, as well as for chemical or petrochemical applications and for green energy generation (H2). In addition, ion-conducting ceramic membrane reactors make it possible to combine membrane separation processes directly with chemical reactions, leading to process intensification and, hence, benefits with regard to efficiency. Current research activities focus on membrane reactors due to their high intrinsic efficiency and great potential for the production of a large variety of commodity chemicals, energy carriers, and synthetic fuels.

Description of work: The proposed master thesis targets the development of BaZr0.8Y0.15Mn0.05O3-δ gastight membranes with several micrometers thickness on a porous support. In addition the microstructure must be optimized and fully characterized regarding performance and sintering behavior. Aim is to increase the hydrogen permeation of the membrane by modifying structure and surface area. The manufacturing of the membranes will be done by sequential tape casting or another reasonable method. Tailoring of the microstructure of the support will be done by modifying the amount of pore former in support and the adjustment of sintering behavior. Sufficient porosity and tortuosity are needed to avoid polarization effects. An enhanced surface area on both sides of the membrane increases the hydration effect. Before starting the experimental work a literature study has to be done to check the state of the art. A detailed work plan will be provided after first discussion with the candidate.

Requirements
Knowledge in materials science ideally ceramics; ability of hands-on lab work; good English skills

Contact person – Forschungszentrum Jülich
Prof. Dr. Wilhelm A. Meulenberg
Phone: +49 2461 61-6323 
E-Mail: w.a.meulenberg@fz-juelich.de

Contact person – University of Twente
Prof. Dr. Henny Bouwmeester
E-Mail: h.j.m.bouwmeester@utwente.nl
Tel:+31 53 489 2202

The main work will be carried out at Forschungszentrum Jülich in Germany. Forschungszentrum Jülich GmbH will cover some living costs for the stay in Jülich.

Sieving of hot gases by thin film composite membranes (MSc assignment)

Project outline:

Global warming due to greenhouse gas emissions is one of the worldwide concerns. Among these gases, CO2 has been recognized as the most responsible one. Many efforts have been made to fabricate membranes, which can separate H2 from CO2 in harsh conditions. Recently, IPOSS membranes show breakthrough results for H2/CO2  selectivities at temperatures up to 300°C, which makes them ideal for using them in the pre-combustion capture.

IPOSS membranes are polyimide membranes which contain POSS (Polyhedral oligomeric silsesquioxane) as the main building block. They are produced by using a two-step procedure: the interfacial polymerization of POSS and anhydride on a ceramic layer (Fig 1.a), followed by thermal imidization (Fig 1.b). The thickness of the produced layer is less than 100 nm [1].

Figure 1. two-step procedure of producing IPOSS membranes [1]

Project description:

This master thesis aims to enhance the performance of IPOSS membranes. To achieve this, Palladium (Pd) nanoparticles can be used. These nanoparticles are only selective toward H2 and using them in the iPOSS membrane will improve the H2 permeability and H2/CO2 selectivity.

There are different ways to add Pd nanoparticles to the membranes. In this assignment, you will explore these methods and investigate its effect on the performance of the membranes.

Project outcome:

This project is a new approach for producing thin film composite (TFC) membranes contain nanomaterials.

Contact:

For more information, feel free to contact Farzaneh Radmanesh (f.radmanesh@utwente .nl)

References:

1.           Raaijmakers, M.J., and N.E. Benes, Current trends in interfacial polymerization chemistry. Progress in polymer science, 2016. 63: p. 86-142.

Influence of thermal history on the oxygen surface exchange for SOFC cathode materials (MSc assignment)

Background

Perovskite oxides belonging to the family; (La1-xSrx)s(Co1-yFey)O3-δ (1 ≥ x ≥ 0, 1 ≥ y ≥ 0, s = 1) have found use as electrodes for solid oxide cells (SOC) and oxygen sensors and are also being explored as potential materials for oxygen separation membranes. This is due to their good ionic and electronic transport properties, high activity for oxygen reduction/ evolution reactions (ORR/OER) and the fact that via tailoring the composition, properties can be ‘tuned’ with a view to the specific application. When assessing the performance of a particular perovskite composition, one usually compares the catalytic activity with a reference, a non-modified sample or a literature value. However, establishing a suitable reference point is not necessarily trivial. A good illustration is given by Bobing et al.1 where a literature review reveals that the results of surface exchange coefficient (kchem) differ over one order of magnitude even for the same cathode material (fig. 1). One of the factors responsible for this scatter in literature is that the thermal history of the samples prior to measurement is rarely detailed. Furthermore, it is often not clear how stable the reported enhancements are and whether the reference samples have representative and stable performance themselves.

Fig.1 Hu, B., & Xia, C. Asia-Pacific J. Chem. Eng. (2016)


Project description

In this project, the aim is to investigate the dependence of oxygen surface exchange rate on the thermal history of LAF64. The candidate will benefit of the expertise and equipment of Electrochemistry Research Group (ECRG) to:

  1. Synthesize LAF64 powder and dense pellets from the protocol described in literature and developed in ECRG previously.
  2. Characterize the as-prepared membranes by various techniques like LEIS, XRD, electron microscopy, XPS, etc...
  3. Finding key parameters (e.g. variations in composition, effect of microstructure and surface composition) that control membrane properties.
  4. Evaluate the electrochemical performance of the membranes by electrical conductivity relaxation (ECR)

 Skills which will be developed during the Master assignment:

  • Synthesis of perovskite powders and dense membranes
  • Characterization of the as-prepared dense membranes by XRD and SEM
  • Surface composition and bulk profile analysis after post annealing treatments by LEIS  and XPS
  • Evaluation of the membrane performances by ECR

For more information please contact:

Zainab Aman  (z.aman-1@utwente.nl), ECRG, ME 236B

Henny Bouwmeester (h.j.m.bouwmeester@utwente.nl), ECRG, ME 349

 [1] Hu, B.; Xia, C. Factors Influencing the Measured Surface Reaction Kinetics Parameters. Asia‐Pacific Journal of Chemical Engineering 2016, 11 (3), 327–337.

Photocatalytic degradation of glycerol in a microchannel (MSc assignment)

Background

Microreactors are well known to intensify a process. Higher conversion can be achieved by changing the reactor from a slurry reactor to a microreactor. It’s easier to determine what is happening in the channel and taking it into account due to the laminar flow. Kinetics can be identified as what is happening at the surface instead of in the bulk. Therefore, microreactors are the ideal platform to study different parameters which influence the kinetics of organic oxidation reactions. Parameters which could influence the kinetics are pH, temperature, oxygen concentration, and others. The microchannel is schematically shown in the figure below, adjusted from [1].

 

Project scope

In this project, the focus is on the influence of the light source on a photocatalytic reaction, which is the oxidation of glycerol to more valuable products. In combination with some modelling you’ll try to figure out what is happening in the channel at the catalytic wall. The experimental part will consist of conversion experiments, to measure how much is converted and into what. A second experimental part consists of fluorescence lifetime imaging microscopy, where real-time profiles of oxygen, pH, carbon dioxide and temperature can be made over the length of the channel.

Contact

For more information, feel free to contact Nicole Timmerhuis (n.a.b.timmerhuis@utwente.nl)

Reference 

[1] Rafieian, D., Driessen, R. T., Ogieglo, W., & Lammertink, R. G. (2015). Intrinsic photocatalytic assessment of reactively sputtered TiO2 films. ACS applied materials & interfaces7(16), 8727-8732.

This project can also be executed by a bachelor student, but preference is given to a master student.

Diffusio-osmosis, an engineering approach (MSc assignment)

Background

Many heterogeneous systems have mass transfer limitations near the solid-liquid interface. These limitations in the boundary layer are due to fast reaction at the wall, creating a concentration drop towards the solid. Or it could be from the velocity which is standing still near the wall due to a laminar, parabolic flow pattern in the microchannel. The main focus of this project is to overcome this mass transfer limitation by creating an osmotic flow near the solid-liquid interface in the boundary layer.

An osmotic flow is created by a pressure gradient in the liquid, which is directly proportional to the concentration gradient for non-electrolytes and to the natural logarithm of the concentration gradient for electrolytes [1]. The concentration gradient is created by the interaction between the liquid particles and solid interface, which can be repulsive or attractive. If different solid interfaces are used, alternating each other, a continuous osmotic flow can be created in the boundary layer along the wall. This is schematically shown in the figure below.

Project scope

In this project you’ll research the broader impact of diffusio-osmosis. What would be the design parameters to utilize osmotic flow for higher conversion or lower pump intensities? This could be investigated numerically. An experimental approach is also possible, where you would first come up with a possible experimental design to measure the diffusio-osmotic velocity.

Contact

For more information, feel free to contact Nicole Timmerhuis (n.a.b.timmerhuis@utwente.nl

Reference

[1] D.C. Prieve, J.L. Anderson, J.P. Ebel, M.E. Lowell, J. Fluid. Mech., 148:247-269, 1984

This project can also be executed by a bachelor student, but preference is given to a master student.