Article
Chemistry, Physical
Stephan Kaufhold, Reiner Dohrmann, Kristian Ufer
APPLIED CLAY SCIENCE
(2020)
Article
Geochemistry & Geophysics
Tilo Kneuker, Martin Blumenberg, Harald Strauss, Reiner Dohrmann, Joerg Hammer, Gernold Zulauf
Article
Chemistry, Physical
Stephan Kaufhold, Reiner Dohrmann, Christian Weber
Summary: The study analyzed the evolution of pH at the iron-bentonite interface and found that the pH values of iron-bentonite mixtures were lower than pure iron-water mixtures, indicating a buffering effect of the clay on alkalinity induced by iron oxidation. Further research is needed to investigate if this will lead to substantial smectite destabilization.
APPLIED CLAY SCIENCE
(2021)
Article
Soil Science
Thilo Rennert, Jan Dietel, Stefan Heilek, Reiner Dohrmann, Tim Mansfeldt
Summary: The study compared Ox, CA, and citrate extractions on subsoils with element accumulation and various minerals. Extraction by Ox showed larger contents of Al, Fe, and Mn compared to CA, except for allophane. Citrate extraction revealed the potential contribution of organic forms to Al and Fe extraction, suggesting the combination of Ox and CA extraction with citrate extraction for better estimation of poorly crystalline pedogenic Al and Fe species. The appropriateness of oxalate-extraction data for species identification and mineral quantification was questioned based on the results.
Article
Geochemistry & Geophysics
Stephan Kaufhold, Reiner Dohrmann, Kristian Ufer, Daniel Svensson, Patrik Sellin
Summary: This study analyzed the ABM5 test results, a medium scale bentonite buffer deposition test conducted at higher temperatures up to 250 degrees C. The chemical and mineralogical reactions were characterized, but the impact of the high temperature was not significant. Some reactions observed were similar to previous tests, while others, such as the decrease in Mg content at the heater, were unique and not fully understood.
Article
Environmental Sciences
Andre Baldermann, Stephan Kaufhold, Reiner Dohrmann, Claudia Baldermann, Ilse Letofsky-Papst, Martin Dietzel
Summary: Nanoscale zero-valent iron (nZVI) based composites supported by clay mineral substrates show promise for the in-situ remediation of groundwater and soils contaminated with chlorinated hydrocarbons. The nZVI-B nanocomposite, with higher reactivity and efficiency for TCE removal compared to pure nZVI, demonstrates the potential for use in permeable reactive barriers for contaminated field sites while minimizing reduction of soil-bearing capacity.
Article
Engineering, Geological
Wolfgang Lieske, Wiebke Baille, Joyce Schmatz, Stephan Kaufhold, Reiner Dohrmann
Summary: This study focused on the characteristics of sensitive clay from Norway, with a special emphasis on the role of mica in material properties. It was found that the plasticity index of these clays tends to decrease with an increasing amount of mica when the salinity is lower than 10 g/1, but increases significantly for higher salt concentrations. The formation of aggregates and their impact on soil mechanical behavior were discussed in relation to the study findings.
ENGINEERING GEOLOGY
(2021)
Article
Environmental Sciences
Christopher Poetzl, Siegfried Siegesmund, Ruben Lopez-Doncel, Reiner Dohrmann
Summary: Volcanic tuffs exhibit strong heterogeneity in their petrography and petrophysical properties, resulting in a wide range of porosities and fabrics that lead to diverse weathering behavior. The presence of clay minerals and zeolites in volcanic tuffs contribute to their high sensitivity to expansion and salt crystallization. Understanding the influence of rock properties on material behavior and durability allows for predictions on future material behavior and evaluation of suitability for construction purposes.
ENVIRONMENTAL EARTH SCIENCES
(2022)
Article
Engineering, Chemical
Srdjan Stankovic, Mirko Martin, Simon Goldmann, Hans-Eike Gaebler, Kristian Ufer, Frank Haubrich, Vivian Fernandes Moutinho, Ellen Cristine Giese, Reiner Neumann, Jose Luciano Stropper, Jens Stummeyer, Stephan Kaufhold, Reiner Dohrmann, Anne Oxley, Herwig Marbler, Axel Schippers
Summary: This study investigated the extraction of nickel and cobalt from iron-rich, limonitic laterites through bioleaching experiments and chemical analyses. The results showed that aerobic bioleaching was more effective in extracting metals, with cobalt mainly hosted by Mn-rich phases and nickel mainly hosted by goethite. The research confirmed the reductive bioleaching of Mn-rich phases and supported the results through chemical leaching tests with different acids and ferrous iron.
MINERALS ENGINEERING
(2022)
Article
Environmental Sciences
Siegfried Siegesmund, Christopher Poetzl, Ruben Lopez-Doncel, Christian J. Gross, Reiner Dohrmann, Kristian Ufer
Summary: This study conducts comprehensive investigations and analyses on volcanic tuff rocks in Mexico to determine their suitability and durability as natural building stones. The research findings indicate a wide range of diversity in color, rock composition, mineralogy, and rock fabric of volcanic tuffs in Mexico.
ENVIRONMENTAL EARTH SCIENCES
(2022)
Article
Geosciences, Multidisciplinary
Lutz Reinhardt, Solveig Estrada, Reiner Dohrmann, Nikola Koglin, Karsten Piepjohn, Jennifer M. Galloway
Summary: Outcrops of distinctive reddish to yellowish clinker, blackish paralava, and mixtures of both are found throughout the Canadian Arctic, resulting from natural combustion of bituminous shale and low-rank coal seams in Cretaceous and Paleogene sedimentary rocks. The geochemical composition of these rocks shows similarities within each outcrop, but also specific elemental enrichments related to the protolith properties. This combustion process has been ongoing since at least the Messinian stage (Miocene) and continues to the present day.
CANADIAN JOURNAL OF EARTH SCIENCES
(2023)
Review
Chemistry, Physical
G. E. Christidis, G. D. Chryssikos, A. Derkowski, R. Dohrmann, D. D. Eberl, E. Joussein, S. Kaufhold
Summary: Layer charge is an important property of 2:1 phyllosilicates and can be determined by various methods. The structural formula method and the alkylammonium method are primary methods but are time consuming and yield contrasting results. Other methods, such as the NH4-method, the K-saturation method, and the O-D method, have been developed recently and can provide a large amount of data quickly. These methods can be used for geological interpretations and industrial-scale assessment of bentonite deposits.
CLAYS AND CLAY MINERALS
(2023)
Article
Environmental Sciences
Siegfried Siegesmund, Christian J. J. Gross, Reiner Dohrmann, Bernd Marler, Kristian Ufer, Tobias Koch
Summary: This study investigates volcanic tuffs and sandstone samples used in cultural heritage buildings in Armenia, Mexico, Germany, and Switzerland. The study shows that progressive weathering caused by temperature fluctuations, moisture uptake, humidity variations, precipitation, pollutants, or salt crystallization leads to damages in the internal structure of the stone. Furthermore, the study explores the possible interaction between swellable clay minerals and zeolites.
ENVIRONMENTAL EARTH SCIENCES
(2023)
Review
Chemistry, Physical
Stephan Kaufhold, Reiner Dohrmann, Ilka Wallis, Christian Weber
Summary: Bentonites are proposed to be used as buffers in high-level radioactive waste repositories. However, the high temperatures in repositories can affect their desired properties, such as swelling and dissolution reactions. Various observable geochemical reactions have been observed, including cation exchange and enrichment of certain elements. Improving the thermodynamic/kinetic data and numerical modeling are necessary for predicting the long-term performance of bentonite buffers.
Article
Chemistry, Physical
Florian Painer, Andre Baldermann, Florian Gallien, Stefanie Eichinger, Florian Steindl, Reiner Dohrmann, Martin Dietzel
Summary: In this study, the hydrothermal alteration of perlite into zeolites was investigated for water treatment and softening applications. Different types of zeolites were successfully synthesized from perlite powder, and their performance for metal ion removal and water softening was evaluated. The LTA-zeolite derived from perlite exhibited excellent removal capacity and can be applied effectively for water treatment and softening.