Particle-mediated transport in geosystems
The mobility of metals and non-metal elements in hydro-geosystems is often determined by the mobility of their likely carriers that occur in broad varieties in nature (geogenic) or are introduced into nature by technological and/or anthropogenic activities. A further deepened, fundamental research based understanding of such particle-mediated transport in geosystems (process understanding) and the likely subsequent risks for the environment is the aim our past, current and future research activities.
Current and past Projects:
- NuWaMa: Visualization of PET-labelled SiO2 particles in a fracture and porous flow (Co-ordinator). BMBF (2016-2018)
- NetFlot: Network of infrastructure: Modeling the Flotation Process (Co-ordinator). H2020, EIT KIC RawMaterial (2016-2018)
- nanoSuppe: Fate of nanoparticles in waste water: TiO2, MWCNT, CeO2, Quantum Dots (Co-ordinator). BMBF (2014-2017)
- cntTrack: Transport of technical carbon nanoparticles in geomatrices´s. DFG FR1643/3-1 (2012-2015)
- Quality-Nano projects: Radiolabelling of nanoparticles with cyclotron facilities. JRC (2013, 2014, 2015)
- nanoTrack: Investigation of the life cycle of nanoparticles be means of [45Ti]TiO2 and [105Ag]Ag0 (Co-ordinator). BMBF (2011-2014)
Occurrence, characterization and modification of nanoparticles and colloids
Natural aqueous humic and fulvic acids, partly extracted from geosystems (surface water and soils), are characterized and used in (kinetic) metal-humate complexation and sorption studies. Metals and non-metals under investigation include Al, Fe, Co, Cu, Zn, Sn, Y, Tl, Eu, Tb, Th, U, Np, Pu, Am, Cm and Se [e.g. 1-3]. Spectroscopic methods (XAS, HEXS, and DLS) allow for the speciation , microscopic (TEM and SEM) allow elucidating their complex structures and polymerization/aggregation mechanism. Radiolabelling methods for the impact assessment of geochemical parameter variations on the metal or metal-humate mobility in geosystems . Isotope exchange and luminescence studies allow for the quantification of kinetic interaction studies between metal and humic/fulvic acids and additional competing system components .
The formation of U(IV)-silica colloids (<20 µm) and their significant stability in natural waters was described for the first time .
The capacity of modified, primarily water-insoluble multiwall carbon nanotubes as U(IV) carrier was uncovered and their significant stability in systems near to nature was demonstrated .
Currently, the characterization of technical nanoparticles (metal oxides and carbon nano tubes) by means of dynamic light scattering, SEM, and ICP-OES, and their modification for better solubility in aquatic systems is studied in detail.
Radiolabelling of system components
Radiolabelling strategies of dedicated system components (humic/fulvic acids , technical nanoparticles, EDTA-coated SiO2) aim at gaining an advanced understanding of processes related to the particle-mediated transport in geosystems. An increasing portfolio of suitable radionuclides (half-life, chemistry, decay mode) is – if not commercially available – produced via neutron activation or at an in-house cyclotron. Effective and stable particle-labelling strategies (complexation, in-diffusion, isotope exchange) are prerequisites for the monitoring of their transport behaviour in geosystems under conditions near to nature and are continuously under development and are regularly published [10,11].
Methods for the 1-4 dimensional visualization and quantification of (particle-mediated) transport in synthetic and natural heterogeneous geologic media were developed in the past decade [12-16]. A basic principle is the application of radionuclide-labelled system components, detectable at very low concentrations and – ideally - chemical identical with non-labelled system components. A specific distinctive feature is the application of the GeoPET-method that allows the visualization of the movement of a PET-nuclide-labelled system component during its passing through the connected pore space/ or fracture in a natural, heterogeneous geological media. So far, complementing tomographic and numerical methods allow for the quantification and verification of the proposed, underlying conceptual models for fluid dynamics and non-reactive (conservative) transport [16,17].
 Schmeide, K., et al.: Np(V) reduction by humic acid: Contribution of reduced sulfur functionalities to the redox behavior of humic acid. Sci.Tot.Environ. 419(2012), 116-123
 Joseph, C., et al.: Sorption of uranium(VI) onto Opalinus Clay in the absence and presence of humic acid in Opalinus Clay pore water. Chem.Geol. 284(2011), 240-250
 Lippold, H., et al.: Competitive effect of iron(III) on metal complexation by humic substances: Characterisation of ageing processes. Chemosphere 67 (2007) 1050-1056
 Hennig, C., et al.: The relationship of monodentate and bidentate coordinated uranium(VI) sulfate in aqueous solution. Radiochim.Acta 96(2008), 607-611
 Lippold, H., Lippmann-Pipke, J.; Effect of humic matter on metal adsorption onto clay materials: Testing the linear additive model. J.Cont.Hydrol. 109(2009) 40-48
 Lippold, H., et al.: Diffusion, degradation or on-site stabilisation – identifying causes of kinetic processes involved in metal-humate complexation. Appl.Geochem. 27(2012), 250-256
 Dreissig, I., et al.: Formation of uranium(IV)-silica colloids at near-neutral pH. Geochim.Cosmochim.Acta 75, 2 (2011), 352-367.
 Schierz, A.; Zänker, H. Aqueous Suspensions of Carbon Nanotubes: Surface Oxidation, Colloidal Stability and Uranium Sorption.Environ.Poll. 157(2009), 1088-1094
 Franke, K., et al.: A new technique for radiolabelling of humic substances. Radiochim. Acta 92 (2004) 359 – 362.
 Hildebrand, H.; Franke, K. A new radiolabeling method for commercial Ag0 nanopowder with 110mAg for sensitive nanoparticle detection in complex media. J. Nanopart. Res. 14 (2012), 1142
 Hildebrand, H., Schymura, S., Holzwarth, U., Gibson, N., Dalmiglio, M., Franke, K.: Strategies for radiolabeling of commercial TiO2 nanopowder as a tool for sensitive nanoparticle detection in complex matrices. J. Nanopart. Res. 17 (2015) 278ff
 M. Richter, M. et al.: cc, Radiochim.Acta 93 (2005), 643-651.
 M. Gründig, M. et al.: Tomographic radiotracer studies of the spatial distribution of heterogeneous geochemical transport processes. Appl.Geochem. 22, 2334-2343.
 Kulenkampff, J., Gründig, M., Richter, M. and Enzmann, F. Evaluation of positron emission tomography for visualisation of migration processes in geomaterials. Phys.Chem.Earth 33 (2008), 937-942.
 Kulenkampff, J., Gründig, M., Lippmann-Pipke, J. Quantitative observation of tracer transport with high-resolution PET. Solid Earth 7, 1217-1231.
 Kulenkampff, J., Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J. Geoscientific process monitoring of molecular diffusion in clay with positron emission tomography (GeoPET). Solid Earth 7, 1207-1215.
 Lippmann-Pipke, J., Gerasch, R.; Schikora, J.; Kulenkampff, J. Benchmarking PET for geoscientific applications: 3D quantitative diffusion coefficient estimation in clay rock. Comp. Geosci. 101, 21-27.
 Schymura, S., Fricke, T., Hildebrand, H., Franke, K. Elucidating the Role of Dissolution in CeO2 Nanoparticle Plant Uptake by Smart Radiolabeling Angew. Chem. Int. Ed., 56(26) (2017) 7411–7414.