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Pohl E.,TU Bergakademie Freiberg | Gloaguen R.,TU Bergakademie Freiberg | Gloaguen R.,Helmholtz Institute Freiberg for Resource Technology | Seiler R.,TU Bergakademie Freiberg
Remote Sensing | Year: 2015

Moisture supply in the Pamir Mountains of Central Asia significantly determines the hydrological cycle and, as a result, impacts the local communities via hazards or socioeconomic aspects, such as hydropower, agriculture and infrastructure. Scarce and unreliable in situ data prevent an accurate assessment of moisture supply, as well as its temporal and spatial variability in this strongly-heterogeneous environment. On the other hand, a clear understanding of climatic and surface processes is required in order to assess water resources and natural hazards. We propose to evaluate the potential of remote sensing and regional climate model (RCM) data to overcome such issues. Difficulties arise for the direct analysis of precipitation if the events are sporadic and when the amounts are low. We hence apply a harmonic time series analysis (HANTS) algorithm to derive spatio-temporal precipitation distributions and to determine regional boundaries delimiting areas where winter or summer precipitation dominate moisture supply. We complement the study with remote sensing-based products, such as temperature, snow cover and liquid water equivalent thickness. We find a strong intra-and inter-annual variability of meteorological parameters that result in strongly variable water budget and water mobilization. Climatic variability and its effects on floods and droughts are discussed for three outstanding years. The in-house developed HANTS toolbox is a promising instrument to unravel periodic signals in remote sensing time series, even in complex areas, such as the Pamir. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source

Rudolph M.,Helmholtz Institute Freiberg for Resource Technology | Peuker U.A.,Institute of Mechanical Process Engineering and Minerals Processing
Chemie-Ingenieur-Technik | Year: 2014

The mineral separation process flotation is fundamentally relying on hydrophobic interactions, which are still not entirely understood and heavily discussed in literature. Here, various possibilities to determine hydrophobic properties of mineral surfaces in water using the concept of colloidal probe atomic force microscopy are introduced. The method is based on the accepted theories of the hydrophobic effect of hydrophobic surfaces in water. Additionally, the hydrophobic parameters are correlated with microflotation experiments for magnetite and quartz surfaces. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Frenzel M.,Helmholtz Institute Freiberg for Resource Technology | Woodcock N.H.,University of Cambridge
Journal of Structural Geology | Year: 2014

Cockade breccias are fault fills in which individual clasts are completely surrounded by concentric layers of cement. They occur particularly in low-temperature near-surface hydrothermal veins. At least six mechanisms have been proposed for the formation of cockade breccia-like textures, but only two - repeated rotation-accretion, and partial metasomatic replacement of clast minerals - have been supported by detailed evidence. A typical example of cockade breccia from the Gower Peninsula (South Wales) shows clear evidence for the rotation-accretion mechanism: in particular, overgrown breakage points in cement layers - where cockades were previously touching each other - and rotated geopetal infills of haematitic sediment. Based on the available evidence, it is proposed that cockade textures result from low rates of cement growth compared to high rates of dilational fault slip. Seven criteria are given for the correct identification of cockade breccias. © 2014 Elsevier Ltd. Source

Rudolph M.,Helmholtz Institute Freiberg for Resource Technology
IMPC 2014 - 27th International Mineral Processing Congress | Year: 2014

Flotation is without a doubt one of the major processes for the separation of fine minerals and it has been applied for more than a century. A key task of a successful flotation separation is to find the proper chemical treatment to selectively hydrophobize and thus float a certain mineral phase using molecules or ions referred to as collectors, depressants, regulators and frothers. Commonly floatability is determined by microflotation tests using the Hallimond tube with pure mineral phases. This method however requires the pure mineral phase which is very often not even taken from the same deposit which is going to be processed. In this paper we present a new approach to in-situ determine and even map the floatability of finely disseminated mineral phases within crosssections of an ore. It is based on measuring hydrophobic effects using colloidal probe atomic force microscopy with a hydrophobic polystyrene probe based on force spectroscopy with a lateral resolution of only a few nanometers. Coupled confocal Raman spectroscopy on the same locality enables the identification of the mineral phase. We present the working principles of the method and show which signals in the force spectra characteristic for hydrophobic interactions can be used to define floatability and which can then be mapped as single quantities, e.g. jump-into-contact events due to nanobubble occurrence or parameters of the long range interaction curves most probably due to capillary effects. A finely grained silicate ore containing the valuable rare earth mineral eudialyte from southern Sweden as well as pure samples of magnetite are presented as substrates to demonstrate the capability of this new approach. This method will not only help to find the proper flotation chemistry but it can furthermore help in researching and unravelling problems of floatability within similar mineral phases. Source

Rudolph M.,Helmholtz Institute Freiberg for Resource Technology | Rudolph M.,TU Bergakademie Freiberg | Peuker U.A.,TU Bergakademie Freiberg
Journal of Nanoparticle Research | Year: 2012

A study is presented, where agglomerated magnetite nanoparticles with a crystallite size of 15 nm are transferred from water to an immiscible organic phase and tend to deagglomerate under certain conditions using different types of chemically adsorbing fatty acid. It is shown that the longer fatty acids lead to more stable dispersions and for the longest fatty acids, the functionality of the molecules defines stability with best results for ricinoleic acid. The disjoining force as a function of the brush layer thickness and adsorption density is calculated with a physical model applying the well-established Alexander de Gennes theory. We further investigate the colloidal stability of the transferred and stabilized magnetite nanocrystals in polymer solutions of destabilizing PMMA and stabilizing PVB. A DLVO-like theory presents the governing attractive and repulsive interactions for the case of destabilizing non-adsorbing polymers. The theory can be used to explain the influencing parameters in a mixture of sterically stabilized nanoparticles in an organic solvent based solution of polymer coils. Finally, by spray drying, we produce polymer-nanoparticle composite microparticles. Based on BET, laser diffraction and backscatter electron SEM measurements, we draw conclusions on the nanoparticle distribution within the composite in correlation with the stability investigations. © 2012 Springer Science+Business Media B.V. Source

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