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Heberling F.,Karlsruhe Institute of Technology | Bosbach D.,Jülich Research Center | Eckhardt J.-D.,Karlsruhe Institute of Technology | Fischer U.,Rheinkalk Akdolit GmbH and Co. KG | And 14 more authors.
Applied Geochemistry | Year: 2014

Surface reactions on calcite play an important role in geochemical and environmental systems, as well as many areas of industry. In this review, we present investigations of calcite that were performed in the frame of the joint research project "RECAWA" (reactivity of calcite-water-interfaces: molecular process understanding for technical applications). As indicated by the project title, work within the project comprised a large range of length scales. The molecular scale structure of the calcite (104)-water-interface is refined based on surface diffraction data. Structural details are related to surface charging phenomena, and a simplified basic stern surface complexation model is proposed. As an example for trace metal interactions with calcite surfaces we review and present new spectroscopic and macroscopic experimental results on Selenium interactions with calcite. Results demonstrate that selenate (SeO4 2-) shows no significant interaction with calcite at our experimental conditions, while selenite (SeO3 2-) adsorbs at the calcite surface and can be incorporated into the calcite structure. Atomistic calculations are used to assess the thermodynamics of sulfate (SO4 2-), selenate (SeO4 2-), and selenite (SeO3 2-) partitioning in calcite and aragonite. The results show that incorporation of these oxo-anions into the calcite structure is so highly endothermic that incorporation is practically impossible at bulk equilibrium and standard conditions. This indicates that entrapment processes are involved when coprecipitation is observed experimentally. The relevance of nano-scale surface features is addressed in an investigation of calcite growth and precipitation in the presence of phosphonates, demonstrating the influence of phosphonates on the morphology of growth spirals and macroscopic growth rates. It is investigated how physical properties of limestone containing cement suspensions may influence the workability of the cement suspensions and thus the efficacy of limestone in industrial applications. The largest scale is reached in iron filtration experiments in a water-purification-pilot-plant using limestone as filter material, which appeared to be highly effective for removing iron from drinking water. Investigations presented cover a whole series of methods to study the calcite-water-interface. Many calcite related topics are addressed, demonstrating how broad the field of calcite-water-interface research is and how manifold the applications are, for which calcite-water-interface phenomena are of major relevance. © 2014 Elsevier Ltd.


Ukrainczyk M.,Karlsruhe Institute of Technology | Ukrainczyk M.,Ruder Boskovic Institute | Stelling J.,Karlsruhe Institute of Technology | Vucak M.,Schaefer Kalk GmbH and Co. KG | Neumann T.,Karlsruhe Institute of Technology
Journal of Crystal Growth | Year: 2013

Abstract: The influence of organic additives on the crystal growth of different calcite morphologies in two crystallization processes operating under steady state and batch mode is described. The crystal growth kinetics and overgrown morphological observations of rhombohedral, scalenohedral and prismatic calcite seed crystals in the systems containing etidronic acid (HEDP) and tartaric acid (TA) were investigated. The crystallization systems were of low supersaturations (SI<1.1) and of moderate pH (8.0). Kinetic parameters of the crystal growth in the presence of selected additives, such as reduction of the growth rates, rate constant and reduced critical supersaturation were calculated and correlated with additive concentration and different calcite seeds. The results indicate strong interactions of HEDP molecules and weak but specific interactions of TA for calcite surfaces. Interactions occur at the step edges which finally results in the expression of near-{hk0} faces and highly polar faces, consisting of solely Ca layer on the surface, stabilised by TA and HEDP molecules, respectively. The affinity of both additives is significantly higher for scalenohedral and prismatic calcite in contrast to rhombohedral calcite seeds. The effect of calcite seed morphology was attributed to different surface energetics of the predominant crystal faces of the studied calcite seeds. © 2013 Elsevier B.V.


Petrack J.,University of Duisburg - Essen | Vucak M.,Schaefer Kalk GmbH and Co. KG | Nover C.,Schaefer Kalk GmbH and Co. KG | Epple M.,University of Duisburg - Essen
Journal of Applied Polymer Science | Year: 2014

Natural rubber latex contains different allergenic proteins and peptides that restrict its application in consumer products. Small mineral particles have a comparatively high specific surface area and are therefore well suited to adsorb such biomolecules. The adsorption of such biomolecules onto different polymorphic phases of calcium carbonate, i.e., calcite, aragonite, and vaterite, was quantitatively determined, both from solution as well as from cured natural rubber latex. All phases were able to adsorb the allergens, with slight differences between the different allergens. Desorption experiments showed differences between the allergens of natural rubber latex, but only small differences between the polymorphic phases of calcium carbonate. The release of the allergens from latex objects with incorporated calcium carbonate particles showed that a retention of allergens is possible by adding calcium carbonate as a filler material. © 2014 Wiley Periodicals, Inc.


Vogel R.,Leibniz Institute of Polymer Research | Boldt R.,Leibniz Institute of Polymer Research | Vucak M.,Schaefer Kalk GmbH and Co. KG | Haussler L.,Leibniz Institute of Polymer Research
Polymer Engineering and Science | Year: 2014

It has been reported in the technical literature that whiskers of rodlike single crystals can be used in order to generate shish-kebab structures or other different lamellae morphologies during isothermal or dynamic crystallization of sheared or presheared polymer melts. The expected advantage of the changed crystalline structure is a reinforcing effect of the composite. A lot of papers reported about the application of inorganic and organic whiskers such as cellulose and chitin whiskers. This study reports on an attempt to use acicular PCC as appropriate whisker for improving mechanical properties of polypropylene. In this article special attention is given to demonstrate the effect of flow induced crystallization under varying shear conditions in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis, tensile testing, and transmission electron microscopy. © 2013 Society of Plastics Engineers.


Vogel R.,Leibniz Institute of Polymer Research | Vucak M.,Schaefer Kalk GmbH and Co. KG | Nover C.,Schaefer Kalk GmbH and Co. KG | Peitzsch L.,Leibniz Institute of Polymer Research
International Polymer Science and Technology | Year: 2013

Precipitated calcium carbonates (PCC) with different particle morphologies were used as appropriate carrier particles for post-processing crosslinking reactions. Optimum particle morphology and size were estimated for preparation of dry liquids. The dry liquids were tested in three typical crosslinking reactions of polymers, e.g. post-processing crosslinking of grafted ethylene/butyl acrylate copolymer, UV crosslinking of metallocene PE and post-processing crosslinking of silane-grafted isotactic PP. © 2013 Smithers Rapra Technology.


Vogel R.,Leibniz Institute of Polymer Research | Vucak M.,SCHAEFER KALK GmbH and Co. KG | Nover C.,SCHAEFER KALK GmbH and Co. KG | Peitzsch L.,Leibniz Institute of Polymer Research
E-Polymers | Year: 2012

Precipitated calcium carbonates (PCC) of different particle morphologies were used as appropriate carrier particles for post-processing crosslinking reactions. Optimum particle morphology and size were estimated for preparation of dry liquids (DLs). The DLs were tested in three different typically crosslinking reactions of polymers.


Vogel R.,Leibniz Institute of Polymer Research | Vucak M.,Schaefer Kalk GmbH and Co. KG | Nover C.,Schaefer Kalk GmbH and Co. KG | Peitzsch L.,Leibniz Institute of Polymer Research
Gummi, Fasern, Kunststoffe | Year: 2012

Precipitated calcium carbonates (PCC) of different particle morphologies were used as appropriate carrier particles for post-processing crosslinking reactions. Optimum particle morphology and size were estimated for preparation of dry liquids (DLs). The DLs were tested in three different typically crosslinking reactions of polymers.


A single-track bypass road was made in Hahnstätten at the instigation of Schaefer KaIk GmbH & Co. KG, one of the largest lime producers in Germany and Europe. The road was prepared as a test section in 2003 to determine the influence of hydrated lime on the resistance of asphalt to ageing. An 0/11S asphalt concrete with a 50/70 bitumen was used in the asphalt covering layer and dolerite, which was available in the region, was chosen as the aggregate. In the test section with a total length of about 1.5 km a subsection approximately 150 m long was laid with 6.2 mass % reclaimed filler and 2 mass % hydrated lime. Since October 2003 about 3000 lorries, each with a load of 40 t, and sometimes also with loads on the return journey, have driven over this test section every year. Samples were taken from the asphalt covering layer in 2009, i.e. after the section had been in place for about six years. These have shown that the weathering on the test section where hydrated lime had been added was clearly less than on the section with no hydrated lime. A linear extrapolation of the results that had been obtained on the basis of the measured softening points suggested that the service life of the asphalt could be extended by up to seven years by using 2 mass % hydrated lime. If this is confirmed then it would correspond to a 27 % improvement in the resistance of asphalt to ageing. The addition of 2 mass % hydrated lime was substantiated during the investigations that were carried out, in which samples were obtained by taking drill cores. However, the questions about the depth of the influence of weathering and the influence of the void volume had to remain unanswered as it was not technically possible to take thin slices from the drill cores in order to obtain reliable information about the progress of the weathering.


Drescher H.,Schaefer Kalk GmbH and Co. KG | Geissler M.,Schaefer Kalk GmbH and Co. KG
Cement International | Year: 2013

Schaefer Kalk GmbH & Co., with its head office in Diez, Germany, processes crushed limestone from several extraction sites in the lime kilns at its Steeden works. For quality purposes (limestone, a natural material, is often subject to large variations both in chemical composition and colour) the company installed two optical sorting machines from the Austrian company BT-Wolfgang Binder GmbH in the limestone preparation plant of its Steeden works at the end of 2011. Depending on the feed material, the two sorting machines have a throughput of 120 to 150 t/h, with up to 30 % of the feed material being discarded. The machines installed at the Schaefer site, each with a sorting width of 2 m, are currently the only ones of their kind in the limestone industry. A colour camera positioned on each side of the crushed limestone to be sorted examines it during free-fall, while the evaluation unit located downstream decides within milliseconds whether the inspected stone has "passed" or is to be rejected from the material stream. The working relationship between the lime works and the Austrian machine manufacture, which was very close right from the beginning, has enabled them to make considerable improvements to the function of the sorting machines over the course of the two-year production operation.


Drescher H.,SCHAEFER KALK GmbH and Co. KG | Geissler M.,SCHAEFER KALK GmbH and Co. KG
Aufbereitungs-Technik/Mineral Processing | Year: 2012

SCHAEFER KALK GmbH & Co. KG processes limestone from a number of different quarries in the kilns of its Steeden plant. Two optical sorting machines were officially commissioned at this plant in late 2011 to permit sustainable continued operation of the quarries and to ensure constant high quality in the particle fractions for burning.

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