Mesa+ Meeting

Thematic Sessions

1Early diagnostics of diseases, chaired by dr.ir. Loes Segerink & prof.dr.ir. Albert van den Berg

2Unconventional electronics, chaired by prof.dr.ir. Wilfred van der Wiel & prof.dr.ing. Guus Rijnders

3Storage and conversion of renewable energy, chaired by prof.dr. Guido Mul & dr.ir. Mark Huijben

4Water, chaired by prof.dr.ir. Rob Lammertink & dr.ir. Wiebe de Vos

Water (ROOM 8)

Chairs: prof.dr.ir. Rob Lammertink (Soft Matter, Fluidics and Interfaces) & dr.ir. Wiebe de Vos (Membrane Science and Technology)

INTRODUCTION

Scarcity of water is a very real problem in many parts of the world, with an estimated 780 million of us lacking access to clean drinking water. And even in western countries the high quality of surface and drinking water are under threat by new pollutants such as nanoparticles and medicinal remains. New sensors and sensing methods are needed to actively check the water quality, while new materials and processes are required to improve cleaning and recycling of water. Interestingly, while water can be considered a threatened resource, it is also key to many new approaches to come to a more sustainable economy. Water is becoming the solvent of choice for many chemical reactions replacing toxic and fossil fuel based solvents. Biobased materials and chemicals stemming from plants and algae require large amounts of water. Clearly, water, both as a resource and as a sustainable solvent, still holds many challenges and opportunities for researchers, some of which will be highlighted in this session.

PROGRAM

ABSTRACTS

Sensors and systems for real-time water quality monitoring

Prof.dr.ir. Joost Lötters (Micro Sensors & Systems/Bronkhorst)

There is a growing need for real-time measurement of the water quality in several types of applications, as for instance monitoring groundwater pollution or analysing the effluent of an oil well after water flooding as applied in enhanced oil recovery. Traditionally, monitoring the water quality is executed through taking samples every once in a while, which are subsequently being analysed in laboratories. This method is time consuming and discontinuous, so, important information is either too late or is not observed at all. Real-time sensors and their working principles will be presented. Furthermore, it will be demonstrated that even more information can be obtained when the sensors are combined into a system, and computational models are derived to determine the levels of the different types of pollution in the water. In the presentation, examples will be given of the applications involved, and some sensors and systems for the real-time monitoring of water quality will be shown.

Water – solid interface properties probed by in situ atomic force microscopy
Dr. Igor Sirenatu (Physics of Complex Fluids)

The distribution of water molecules, ions, surface defects, and charge at solid-water interfaces play an essential role in a wide range of processes, e.g. in oil recovery, photocatalysis and water purification. While study of the solid-aqueous electrolyte interfaces date back to the early 20th century, a detailed picture of the structure of the electric double layer and hydration has remained elusive, largely because of experimental techniques have not allowed direct observation of the behaviour of ions, i.e. with subnanometer resolution. Making use of recent advances in Atomic Force Microscopy with atomic level precision, herein, we reveal the local surface charge and the ordered adsorption of the water, ions, to heterogeneous catalyst under operating conditions and clay surfaces in contact with aqueous electrolytes.

Electrochemical detection at sub-nanomolar concentrations using nanofluidics

Prof.dr. Serge Lemay (NanoIonics)

Electrochemical detection in water is typically limited to analyte concentrations above 1 micromolar due to interference from background reactions caused by water itself or by traces of organics. We have developed methods for approximately determining the concentration of chemically reversible redox species down to 10 pM. Our approach is based on pairs of electrodes imbedded in a nanochannel and separated by ~50 nm. Analyte molecules undergoing Brownian motion inside the device repeatedly collide with the electrodes, where they are successively oxidized and reduced. This redox-cycling process is so efficient that individual molecules can be detected, either by directly measuring the electron-shuttling current or by integrating the charge deposited on an electrically floating electrode.

Energy from natural salinity gradients

Timon Rijnaarts MSc. (Membrane Science and Technology)

Reverse Electrodialysis (RED) is a technology for renewable energy using salinity gradients, such as river and seawater. In RED of artificial river and seawater, power densities of 2W per m² of membrane area can be achieved. However, in real water streams also multivalent ions (e.g. Mg²⁺, SO₄^2-) are present that decrease the RED power output. This is due to (I) transport of Mg²⁺ against its concentration gradient or (II) membrane resistance increase. A 30-50% decrease in gross power densities was observed with commercial membranes with just 10% Mg²⁺ in the feed waters.

In this research we show a new approach: new FUJI MP1 cation exchange membranes are designed with low resistance for Mg²⁺ to overcome the deteriorating effect of Mg²⁺ binding. Moreover, they are compared with the monovalent selective CMS, which is able to block uphill transport and thereby achieve a high voltage. For conclusion, we will show gross and net power densities in RED for the different cation exchange membranes as well.