Ralf Kägi

Ph.D. position in the field of fate and behavior of nanoparticles in the aquatic environment.

The objective of this Ph.D project is to investigate the behavior of silver nanoparticles during wastewater treatment.

Background

The release of silver nanoparticles (Ag-NP) from consumer products is of concern due the well known toxicity of the Ag+ ions. Ag-NP, or nanomaterials in general, released from domestic and industrial sources will be mostly collected in sewer systems and transported to wastewater treatment plants (WWTP). Depending on efficiency of the WWTP, the nanomaterials may enter the aquatic environment (or soils via sewage sludge). WWTP thus play a key role in controlling the release of Ag-NP into the aquatic environment.

Aim

In this project, the physical (agglomeration) and chemical (speciation of Ag) changes of the Ag-NP during different stages of the wastewater treatment including aerobic and anaerobic conditions will be investigated. For that purpose a combination of on-line methods (e.g. UV-vis absorption spectroscopy, dynamic and static light scattering), microscopic (scanning and transmission electron microscopy), and synchrotron based x-ray adsorption spectroscopic (XAS) methods will be employed. Specifically, the effect of size and of surface coatings (functionalization) on the kinetics of the Ag-NP transformation in complex matrices will be investigated.

Profile

The ideal candidate should have a Master degree or equivalent in chemistry, environmental sciences (including earth sciences), or environmental engineering. The person should be highly motivated, and being able to work independently in our research team. Experience in analytical chemistry or process engineering are advantageous.

Research Interests

• Detection and fate of engineered nanoparticles in the natural environment and engineered systems
• Development of new analytical methods for nanoparticle detection
• Characterization of the structure of environmental colloids and particles using microscopic and spectroscopic methods
• Optimization of sampling and fractionation procedures for colloids and nano scale materials

CV

Feb. 2006 – today	Head of the Particle Laboratory at the Eawag.
Feb. 2001 – Feb. 2006	Research fellow, Department of Air Pollution / Environmental Technology, Swiss Federal Institute of Materials Science and Technology (Empa), Dübendorf, Switzerland
Oct. 1996 – Dec. 2000	Ph.D. thesis (Institute for Mineralogy and Petrology, ETH Zürich): “The Liquid line of Descent of Hydrous, Primary, Calc-alkaline Magmas under Elevated Pressure: An Experimental Approach” (Supervisors: Prof. Dr. Alan B. Thompson, Prof. Dr. S. Poli, Dr. P. Ulmer, and Dr. O. Muentener)
October 1997 / 1998	Geological field work in Washington State, USA (Sampling of magmatic high-pressure rocks) (Collaboration with Prof. Dr. G. Bergantz, Washington State University, Seattle, USA)
Nov. 1991 – April 1996	Diploma Thesis in Earth Sciences at University of Basel : “Geochemical Evolution of the Husafell-Central Volcano, SW-Iceland”, (Supervisors: Prof. Dr. W. Stern, Dr. K. Saemundsson (Reykjavik), and PD Dr. R. Hänny)

Research statement

Nano-materials (including engineered nanoparticles(NP), as well as nano-structure materials) are increasingly used in many consumer products due to their ‘beneficial’ properties. However, while these materials are certainly beneficial regarding their respective application, they might not be as beneficial in the aquatic environment. The (unintended) release and the fate of these nano-materials in the aquatic environment are only poorly understood mainly due to the he lack of adequate analytical techniques to detect and characterize these materials in the environment. My research therefore, aims at combining well established standard characterization methods from colloidal sciences, with new methods from materials science and with own developments to detect, quantify and understand the effects of the ‘nano-materials’ in the aquatic environment. The following research areas are of particular interest:

Detection and fate of engineered nanoparticles in the natural environment and engineered systems.

Although a large variety of analytical methods exist to characterize nano scale materials (and especially nanoparticles) mainly developed for materials science applications. these methods are capable of detecting pure substances in high concentrations (such as Ag-NP in concentrated stock solutions), but cannot handle polydisperse and dilute systems. However, natural systems are polydispers and dilute; we therefore try to fractionate aquatic colloids, including engineered NP, into monodisperse size fractions using field flow fractionation techniques. Individual size fractions can be further be analyzed using light scattering, mass spectroscopic or microscopic techniques.

Development of new analytical techniques to detect NP

Commercially available particle detection systems are not designed to detect particles down to the nano scale. A very promising laser based method (Laser Induced Breakdown Detection, LIBD) capable of detecting particles down to about 10nm at low concentrations has been developed almost 20 years ago by Japanese researchers. The technique never had it huge break-through (for several reasons) and thus no commercial LIBD systems are available. However, for certain applications, such as drinking water monitoring, the technique seems to be well suited. We therefore developed our own LIBD prototype in collaboration with the FZ-Karlsruhe, which is being continuously refined.

Characterization of the structure of environmental colloids and particles using microscopic and spectroscopic methods

Within this branch of research I am using state-of-the-art electron microscopes (SEM and TEM) to characterize particles, such as natural and experimentally produced aquatic colloids, as well as particles recovered from ice cores. This part of my research has the rather unspecific goal of seeking any kind of information stored in the particles that was not accessible with ‘older’ instruments. This exploratory work is vital to my function as head of the particle laboratory at the Eawag, where I support / advise different ‘users’ on a variety of different materials.

Particle Laboratory at Eawag

Apart from my own research outlined above I also run the particle laboratory at Eawag. The particle laboratory is a contact-point for all sorts of particle-related questions, especially concerning microscopic work. My engagement in different projects covers all ranges from simple advice over a few measurements for a feasibility study up to solid collaborations. Thanks to very good contacts to the electron microscopy centers at ETHZ and Empa, experts on any kind of materials can be consulted if necessary.

Selected Publications:

Glaus, R., Kaegi, R., Krumeich, F.Guenther, D., 2010. Phenomenological studies on structure and elemental composition of nanosecond and femtosecond laser-generated aerosols with implications on LA-ICPMS, Spectrochimica Acta Part B: Atomic Spectroscopy, accepted.

Kaegi, R., Sinnet, B., Zuleeg, S., Hagendorfer, H., Mueller, E., Vonbank, R., Boller, M.Burkhardt, M., 2010a. Release of silver nanoparticles from outdoor facades, Environmental Pollution,doi:10.1016/j. envpol.2010.06.009

Kaegi, R., Voegelin, A., Folini, D.Hug, H. J., 2010b. Effect of phosphate, silicate and Ca on the morphology, structure and elemental composition of Fe(III) precipitates formed in aerated Fe(II) and As(III) containing water., Geochimica Et Cosmochimica Acta, accepted.

Latkoczy, C., Kaegi, R., Fierz, M., Ritzmann, M., Günther, D.Boller, M., 2010. Development of a mobile fast-screening laser-induced breakdown detection (LIBD) system for field-based measurements of nanometer sized particles in aqueous solutions, Journal of Environmental Monitoring, in press.

Hagendorfer, H., Lorenz, C., Kaegi, R., Sinnet, B., Gehrig, R., v. Götz, N., Scheringer, M., Ludwig, C., and Ulrich, A., 2010. Size fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles. Journal of Nanoparticle Research, in press.

Voegelin, A., Kaegi, R., Frommer, J., Vantelon, D., and Hug, S. J., 2010. Effect of phosphate, silicate, and Ca on Fe(III)-precipitates formed in aerated Fe(II)- and As(III)-containing water studied by X-ray absorption spectroscopy. Geochimica Et Cosmochimica Acta 74, 164-186.

Godoi, R. H. M., Aerts, K., Harlay, J., Kaegi, R., Ro, C. U., Chou, L., and Van Grieken, R., 2009. Organic surface coating on Coccolithophores - Emiliania huxleyi: Its determination and implication in the marine carbon cycle. Microchemical Journal 91, 266-271.

Vernooij, M. G. C., Mohr, M., Tzvetkov, G., Zelenay, V., Huthwelker, T., Kaegi, R., Gehrig, R.Grobety, B., 2009. On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study, Environmental Science & Technology,43, 5339-5344.

Weber, F. A., Voegelin, A., Kaegi, R.Kretzschmar, R., 2009. Contaminant mobilization by metallic copper and metal sulphide colloids in flooded soil, Nature Geoscience,2, 267-271.

Kirchner, U., Scheer, V., Vogt, R., Kaegi, R., 2009. TEM study on volatility and potential presence of solid cores in nucleation mode particles from diesel powered passenger cars, Journal of Aerosol Science,40, 55-64.

Kaegi, R., Ulrich, A., Sinnet, B., Vonbank, R., Wichser, A., Zuleeg, S., Simmler, H., Brunner, S., Vonmont, H., Burkhardt, M.Boller, M., 2008a. Synthetic TiO2 nanoparticle emission from exterior facades into the aquatic environment, Environmental Pollution,156, 233-239.

Kaegi, R., Wagner, T., Hetzer, B., Sinnet, B., Tzuetkov, G.Boller, M., 2008b. Size, number and chemical composition of nanosized particles in drinking water determined by analytical microscopy and LIBD, Water Research,42, 2778-2786.

Fierz, M., Kaegi, R.Burtscher, H., 2007. Theoretical and experimental evaluation of a portable electrostatic TEM sampler, Aerosol Science and Technology,41, 520-528.

Lorenzo, R., Kaegi, R., Gehrig, R., Scherrer, L., Grobety, B.Burtscher, H., 2007. A thermophoretic precipitator for the representative collection of atmospheric ultrafine particles for microscopic analysis, Aerosol Science and Technology,41, 934-943.

Lorenzo, R., Kaegi, R., Gehrig, R.Grobety, B., 2006. Particle emissions of a railway line determined by detailed single particle analysis, Atmospheric Environment,40, 7831-7841.

Kaegi, R.Gasser, P., 2006. Application of the focused ion beam technique in aerosol science: detailed investigation of selected, airborne particles, Journal of Microscopy-Oxford,224, 140-145.

Kaegi, R., 2004. Chemical and morphological analysis of airborne particles at a tunnel construction site, Journal of Aerosol Science,35, 621-632.Kaegi, R.Holzer, L., 2003. Transfer of a single particle for combined ESEM and TEM analyses, Atmospheric Environment,37, 4353-4359.

Mathis, U., Kaegi, R., Mohr, M.Zenobi, R., 2004. TEM analysis of volatile nanoparticles from particle trap equipped diesel and direct-injection spark-ignition vehicles, Atmospheric Environment,38, 4347-4355.

Mavrocordatos, D., Kaegi, R.Schmatloch, V., 2002. Fractal analysis of wood combustion aggregates by contact mode atomic force microscopy, Atmospheric Environment,36, 5653-5660.

Book Chapter:

Hassellöv, M. and Kaegi, R. (2009): Analysis and characterization of Manufactured Nanoparticles in Aquatic Environments. In Environmental and Human Health Impacts of Nanotechnology Eds. Lead J.R. and Smith, E., Blackwell Publishing Ltd.