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Kulik D.A.,Paul Scherrer Institute | Wagner T.,ETH Zurich | Dmytrieva S.V.,Institute of Environmental Geochemistry | Kosakowski G.,Paul Scherrer Institute | And 4 more authors.
Computational Geosciences | Year: 2013

Reactive mass transport (RMT) simulation is a powerful numerical tool to advance our understanding of complex geochemical processes and their feedbacks in relevant subsurface systems. Thermodynamic equilibrium defines the baseline for solubility, chemical kinetics, and RMT in general. Efficient RMT simulations can be based on the operator-splitting approach, where the solver of chemical equilibria is called by the mass transport part for each control volume whose composition, temperature, or pressure has changed. Modeling of complex natural systems requires consideration of multiphase-multicomponent geochemical models that include nonideal solutions (aqueous electrolytes, fluids, gases, solid solutions, and melts). Direct Gibbs energy minimization (GEM) methods have numerous advantages for the realistic geochemical modeling of such fluid-rock systems. Substantial improvements and extensions to the revised GEM interior point method algorithm based on Karpov's convex programming approach are described, as implemented in the GEMS3K C/C++ code, which is also the numerical kernel of GEM-Selektor v.3 package (http://gems.web.psi.ch). GEMS3K is presented in the context of the essential criteria of chemical plausibility, robustness of results, mass balance accuracy, numerical stability, speed, and portability to high-performance computing systems. The stand-alone GEMS3K code can treat very complex chemical systems with many nonideal solution phases accurately. It is fast, delivering chemically plausible and accurate results with the same or better mass balance precision as that of conventional speciation codes. GEMS3K is already used in several coupled RMT codes (e.g., OpenGeoSys-GEMS) capable of high-performance computing. © 2012 Springer Science+Business Media B.V.

Wagner T.,ETH Zurich | Kulik D.A.,Paul Scherrer Institute | Hingerl F.F.,ETH Zurich | Hingerl F.F.,Paul Scherrer Institute | Dmytrievava S.V.,Institute of Environmental Geochemistry
Canadian Mineralogist | Year: 2012

The development of highly accurate and computationally efficient modeling software based on Gibbs energy minimization (GEM) makes it possible to thermodynamically simulate geochemically realistic subsurface fluid-rock interaction processes. This involves consideration of non-ideal multicomponent-multiphase systems that include dilute to concentrated aqueous electrolyte solutions, mineral solid solutions, supercritical fluids, silicate and metal melts, and sorption and ion exchange phases. Predicting the stability and thermodynamic properties of non-ideal solution phases over wide ranges of pressures and temperatures requires that theoretically sound and sufficiently accurate equation of state and activity models are used within the GEM framework. The variety of such models calls for a novel, flexible, and computationally efficient code architecture that supports a wide range of models of non-ideal mixing with different mathematical structures and input data. Here, we introduce the TSolMod C++ class library for equation of state and activity models, implemented within the GEMS3K solver of geochemical equilibria as part of the GEM-Selektor code package (http://gems.web.psi.ch). Essential features of the TSolMod library include a generic and flexible model parameter setup, computationally efficient data exchange with the GEM algorithm, and a straightforward extensibility with any new models of mixing. The current version of TSolMod features a comprehensive selection of fluid, gas, liquid, and solid solution models of interest for geochemical, petrological, material science, and chemical engineering applications.

Miron G.D.,ETH Zurich | Kulik D.A.,Paul Scherrer Institute | Dmytrieva S.V.,Institute of Environmental Geochemistry | Wagner T.,University of Helsinki
Applied Geochemistry | Year: 2015

GEMSFITS is a new code package for fitting internally consistent input parameters of GEM (Gibbs Energy Minimization) geochemical-thermodynamic models against various types of experimental or geochemical data, and for performing inverse modeling tasks. It consists of the gemsfit2 (parameter optimizer) and gfshell2 (graphical user interface) programs both accessing a NoSQL database, all developed with flexibility, generality, efficiency, and user friendliness in mind. The parameter optimizer gemsfit2 includes the GEMS3K chemical speciation solver (http://gems.web.psi.ch/GEMS3K), which features a comprehensive suite of non-ideal activity- and equation-of-state models of solution phases (aqueous electrolyte, gas and fluid mixtures, solid solutions, (ad)sorption. The gemsfit2 code uses the robust open-source NLopt library for parameter fitting, which provides a selection between several nonlinear optimization algorithms (global, local, gradient-based), and supports large-scale parallelization. The gemsfit2 code can also perform comprehensive statistical analysis of the fitted parameters (basic statistics, sensitivity, Monte Carlo confidence intervals), thus supporting the user with powerful tools for evaluating the quality of the fits and the physical significance of the model parameters. The gfshell2 code provides menu-driven setup of optimization options (data selection, properties to fit and their constraints, measured properties to compare with computed counterparts, and statistics). The practical utility, efficiency, and geochemical relevance of GEMSFITS is demonstrated by examples of typical classes of problems that include fitting of parameters of thermodynamic mixing models, optimization of standard state Gibbs energies of aqueous species and solid-solution end-members, thermobarometry, inverse titrations, and optimization problems that combine several parameter- and property types. © 2014 Elsevier Ltd.

Bondar Y.,Institute of Environmental Geochemistry | Kuzenko S.,Institute of Environmental Geochemistry | Han D.-H.,Yeungnam University | Cho H.-K.,Yeungnam University
Nanoscale Research Letters | Year: 2014

A nanocomposite adsorbent based on potassium nickel hexacyanoferrate-loaded polypropylene fabric was synthesized for selective removal of Cs ions from contaminated waters by a two-stage synthesis: radiation-induced graft polymerization of acrylic acid monomer onto the nonwoven polypropylene fabric surface with subsequent in situ formation of potassium nickel hexacyanoferrate (KNiHCF) nanoparticles within the grafted chains. Data of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy confirmed the formation of KNiHCF homogeneous phase on the fabric surface, which consisted of crystalline cubic-shaped nanoparticles (70 to 100 nm). The efficiency of the synthesized adsorbent for removal of cesium ions was evaluated under various experimental conditions. It has demonstrated a rapid adsorption process, high adsorption capacity over a wide pH range, and selectivity in Cs ion removal from model solutions with high concentration of sodium ions. © 2014, Bondar et al.; licensee Springer.

Bondar Yu.V.,Institute of Environmental Geochemistry | Han D.H.,Yeungnam University
Russian Journal of Applied Chemistry | Year: 2012

Amination with diethylenetriamine of poly(glycidyl methacrylate) chains grafted onto polypropylene fibers by the radiation-chemical procedure was studied. © Pleiades Publishing, Ltd., 2012.

Cho H.K.,Yeungnam University | Park J.S.,Yeungnam University | Han D.H.,Yeungnam University | Han D.H.,Institute of Environmental Geochemistry | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2011

A sorption-active material carrying sulfonic acid groups was synthesized by the radiation-induced graft polymerization of styrene monomer onto the surface of non-woven polypropylene fabric, followed by sulfonation of the grafted polystyrene chains. The effect of the main experimental parameters (absorbed dose, monomer concentration, reaction time) on the styrene degree of grafting was investigated. The sulfonation process with 5% chlorosulfonic acid at room temperature was investigated in detail and the optimal sulfonation conditions for the samples with a medium degree of grafting (70-140%) were determined. Densities of 3.5-5 meq/g were obtained by applying those sorption-active PP fabrics with a sulfonic acid group. © 2011 Elsevier B.V. All rights reserved.

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