Stephan Schmidt KG

Langendernbach, Germany

Stephan Schmidt KG

Langendernbach, Germany
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Binner I.,Leibniz University of Hanover | Dultz S.,Leibniz University of Hanover | Schellhorn M.,Stephan Schmidt KG | Schenk M.K.,Leibniz University of Hanover
Applied Clay Science | Year: 2017

Clay amendments are used widely in the horticultural industry in peat-based substrates, as they have the capability to improve the potassium (K) buffering capacity. The K adsorption and desorption behavior of different clays was characterized here to develop criteria for identification of clays suitable for substrate amendment and to evaluate their significance for plant K uptake. K adsorption of saprolitic, bentonitic and relocated clays from the Westerwald area, Germany, was characterized with adsorption isotherms for calculating the maximum adsorption capacity for K. The K desorption was quantified in a percolation experiment using 0.01 M CaCl2 as extractant. The influence of a varying K adsorption capacity of the clays on the K availability to plants was investigated in a growth experiment. The availability of K in substrates was determined by 0.01 M CaCl2 (CAT), Ca-acetate-lactate and NH4 acetate. Different cultivation practices were simulated by varying the start of K topdressing: “immediate,” “delayed” and “no” K topdressing. A higher K adsorption capacity of the clays amended resulted in a lower K concentration in the pore solution of clay-amended peat-based substrates, while the CAT extractable K concentration was the same. It also resulted in an enhanced plant growth and higher K concentrations in the shoot without K topdressing. The uptake of K by plants exceeded the amount of exchangeable K in some peat-clay blends where no K was fertilized. The amount of K released from the clays in the plant experiments was in the same magnitude as the maximal desorbable K determined in the percolation experiment and was highly dependent on the mineralogical composition in the order: smectitic > illitic, kaolinitic clay. The K released from the clays contributed significantly to the supply of K to plants. © 2017 Elsevier B.V.

Wolters F.,Clostermann Consulting GmbH and Co KG | Baille W.,Ruhr University Bochum | Emmerich K.,Karlsruhe Institute of Technology | Schmidt E.,Stephan Schmidt KG | And 5 more authors.
Clay Minerals | Year: 2015

The two high-pressure water-retaining dams at the Ibbenbüren coalmine in Münsterland (Germany) have to perform reliably under the induced tension caused by further exploitation of the current mining area. The load-bearing and the sealing functions of the new barriers were separated and new sealing materials were developed. An innovative multilayer sealing system of bentonite and sandwiched equipotential layers (SANDWICH) supporting homogeneous swelling and sealing, independent of formation water (Nüesch et al., 2002), was applied in this project. A testing program of strain-controlled swelling pressure tests on compacted bentonite specimens and on a bentonite/sand mixture was conducted to ensure an adequate potential for swelling-pressure development. The measurements under constant volume for dry densities between 1.45 g/cm3 and 1.67 g/cm3 showed an evolving swelling pressure between 1.04 and 1.8 MPa for 100% bentonite samples. Straincontrolled oedometer tests for zero strain and step-wise applied strain up to 2% revealed that a sufficient magnitude of swelling pressure existed at maximum applied strain. © 2015 The Mineralogical Society.

Schellhorn M.,Stephan Schmidt KG | Schenk M.K.,Leibniz University of Hanover | Schmilewski G.,Klasmann Deilmann GmbH | Binner I.,Leibniz University of Hanover | And 5 more authors.
Telma | Year: 2013

The purpose of adding clay to horticultural growing media is to achieve objectives such as a well-balanced nutrient supply, buffering of the pH-value, improvement of the rewettability, cohesion of the growing medium and supply of trace elements. Criteria for choosing clay types for specific applications are necessary to assess the suitability of original materials as well as processed clays in a reliable way. A wide range of clays for different applications was chosen for this study. Differences in the mineralogical composition and in pretreatment of the selected clays resulted in specific physical and chemical characteristics of the different growing media mixes. The influence of different clays on the rewettability and cohesion of growing media was analyzed in laboratory experiments which resulted in the definition of important parameters for selection of clays and suitable methods for processing. Clays with strong K and P fixation as well as clays with spontaneous release of these macronutrients were identified. The effects of clays on the flow of nutrients were documented in crop tests, growth-trials regarding Mn toxicity, carried out with clays with different contents of active Mn, proved that an existing RHP-threshold value for Mn in clays for growing media is not justified.

Diedel R.,Forschungsinstitut For Anorganische | Latief O.,Stephan Schmidt KG
CFI Ceramic Forum International | Year: 2011

The requirements for raw material evaluation and therefore raw material analysis are defined with the goal of developing mineral blends that permit a workable production as well as the required product properties. A range of interdisciplinary test series and projects have been conducted, the results of which have contributed to the further development of measurement methods as well as to further clarification of correlations between the constituent materials and the processing properties of silicate ceramic bodies. Particle size measurement is an integral component in the assessment of raw materials and their possible applications. Especially for clay minerals, this characteristic value is of crucial importance as, in combination with the chemism, it is possible to derive information concerning the mineralogical composition of the clay. However, systematic research is needed for the determination of the zeta potential for characterization of the colloid chemical behavior or also for the reproducible measurement of the particle shapes for clay-mineral-containing bodies.

Dultz S.,Leibniz University of Hanover | Below M.,Leibniz University of Hanover | Walsch J.,Leibniz University of Hanover | Schmilewski G.,Klasmann Deilmann GmbH | And 2 more authors.
Acta Horticulturae | Year: 2013

Peat is an important growing media constituent which exposes hydrophobic properties if getting dry. The addition of clay induces a coated surface with hydrophilic properties which improves the re-wettability. The formation of an effective clay coating on peat during processing depends predominantly on the amount of clay applied, clay fineness and mineral parameters. Peat surfaces consist mainly of C. When these are covered with clay minerals rich in Si, the degree of coverage can be described as the C/Si ratio, determined by energy dispersive X-ray spectroscopy. A moderately decomposed sphagnum peat was amended with four different clays from the Rhenish Massif, Germany (10, 20, and 30 kg clay/m3). Aggregate size varied from <0.063 to 2.0-4.0 mm and water-uptake characteristics were determined using a capillary-rise method. Water uptake was improved for all samples by amendment of clay, strongly depending on clay parameters. At C/Si ratios <20, where the surfaces of peat are most completely coated with clay minerals, all clay-peat systems showed the highest water uptake rate. Saprolitic and translocated clays, consisting mainly of illite and kaolinite, had the strongest effect on surface coverage degree. Here already 20 kg/m3 were sufficient to reach lowest C/Si ratios indicating maximum coverage degree. These clays showed fastest water uptake (50 vol. % within 10 min), whereas bentonite showed only minor effects (1.47 to 3.63 (% v/v)/min). A translocated clay was most effective to improve the water uptake rate, admixing small clay amounts. The results show a good correlation of the C/Si ratio and re-wettability. The determination of the C/Si ratio in a relatively short procedure is a method to estimate the water uptake rate of different horticultural growing media. The combination of these methods can be used to identify suitable clays for improving re-wettability, optimum clay fineness and the amount of clay needed.

The data of the mineralogical composition and the determination of CEC were used to develop clay blends for sanitaryware on the basis of reduced proportions of swellable clays. The rheological parameters were determined applying the usual testing methods with Gallenkamp and flow viscosimeter. Measurements after 24 h clearly illustrates that the blend developed on the basis of the data determined shows less deviation with respect to rheology. The suspensions used for these tests were produced with identical process parameters regarding content of deflocculant, stirring rate and stirring time. A total of 10 measurements were carried out, each time refilling the measuring system. During the disturbance test with the rotational viscosimeter the homogenized suspension is stressed by a pre-shearing and a subsequent resting period at a constant shear rate of 0,5 s-1, increasing the stress after 120 s suddenly to a shear rate of 100 s-1.

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