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Visual MINTEQ 3.1 user guide Jon Petter Gustafsson This user guide is not compl

Visual MINTEQ 3.1 user guide Jon Petter Gustafsson This user guide is not complete and at this stage it contains information on the most basic aspects of the program, such as input/output file handling, pH options etc., as well as on adsorption. I will extend it in the future with details on organic complexation models and on the Biotic Ligand Model. / JPG 20/8 2014. 1 Contents 1. What is Visual MINTEQ? 3 1.1. History of the MINTEQ codes 3 1.2. MINTEQA2 and Visual MINTEQ – similarities and differences 4 1.3. Some technical specifications 4 1.4. Download and install 5 1.5. Common problems 6 1.6. Acknowledgements 7 2. Introduction to Visual MINTEQ 8 2.1. First look at Visual MINTEQ 8 2.2. Visual MINTEQ terminology 9 2.3. Input/output file handling 10 2.4. Options for setting the pH value 10 2.5. Creating a problem 12 2.6 Multi-problem / Sweep options 17 2.7 Reading data from Excel 23 2.8 Interpreting the output 25 3. Common menu options 31 3.1 Alkalinity 31 3.2 Oxidation and reduction reactions 35 3.3. Gases______________________ 38 3.4 Solid phases and excluded species 39 4. Adsorption 46 4.1 Introduction to adsorption reactions 46 4.2 Surface complexation models – mathematical basis 46 4.3 Using surface complexation models in Visual MINTEQ 54 4.4 Ion exchange reactions 60 4.5 Optimization of surface complexation constants by use of PEST 65 References 72 2 1. What is Visual MINTEQ? 1.1 History of the MINTEQ codes Visual MINTEQ was first released in 2000 as a Windows user interface to the U.S. EPA model MINTEQA2. The original version of this model (called MINTEQ) was developed in the early 1980's at Battelle Pacific Northwest Laboratory (Felmy et al., 1984) as a cooperative effort funded by the U.S. Department of Energy and the U.S. EPA. The original MINTEQ developed by Felmy et al. (1984) was produced by combining the mathematical structure of MINEQL (Westall et al., 1976) with the thermodynamic database of the WATEQ3 model developed by the U.S. Geological Survey (Ball et al., 1981). The MINTEQ model was then renamed to MINTEQA1 by the U.S. EPA Environmental Research Laboratory at Athens, Georgia (AERL) in 1985. The model was anticipated to diverge from the original as it was adapted to the special needs of the U.S. EPA, but in reality there were very few differences between MINTEQA1 and the original MINTEQ. The distribution package, available for DOS-based PC’s or for Digital Equipment Corporation VAX machines, included a preprocessor program PRODEFA1 for the preparation of MINTEQA1 input files. After more significant revisions were made in the late 1980's, the name was changed to MINTEQA2. With further development, version numbers were used to indicate new versions, and the model’s formal name was left as MINTEQA2. The current version, released in 2005, is version 4.03. Work with Visual MINTEQ began in 1998 with the code “MINTEQA2 For Windows 95”, which was only a Windows interface to MINTEQA2 ver. 3.11. This code was never published. It was used for undergraduate teaching at the Swedish University of Agricultural Sciences (SLU). In the first Visual MINTEQ version (1.0), released in 2000 on the web, the code had been entirely rewritten in Visual Basic version 6.0. Still, however, Visual MINTEQ was essentially just a Windows interface to MINTEQA2 ver. 4.0. After the release of Visual MINTEQ ver. 2 in 2001, the model gradually diverged from MINTEQA2, for example by expanding and revising the thermodynamic database as well as including new options for modeling surface complexation and organic complexation. With version 3.0, the code has been completely transferred to the .NET environment relying on .NET Framework. Still, however, the numerical engine of the program still relies on the subroutines of MINEQL (Westall et al.,. 1976) with only small changes to accommodate the new options added later. As for its graphical structure, Visual MINTEQ has remained essentially the same since the 1998 version of “MINTEQA2 For Windows 95”. 3 1.2 MINTEQA2 and Visual MINTEQ – Similarities and differences Because Visual MINTEQ and MINTEQA2 have the same origins and largely the same procedures for calculations, there are many similarities between the two codes. For example, the same terminology is used in both codes (e.g., components, infinite and finite solids, etc.). Still, users of Visual MINTEQ may still find it useful to consult the manual for MINTEQA2 ver. 4.0, especially for background descriptions. However, since Visual MINTEQ started to diverge from MINTEQA2 in 2000, there are now a number of differences between the codes. In most cases this is because a number of new options and features have been added. Here are some examples of enhancements in Visual MINTEQ: 1. Visual MINTEQ can account for the effects of mixing and dilution when a titrant of a given composition is added to a solution. 2. There are six different surface complexation models to choose from; Visual MINTEQ includes the Basic Stern, the Three Plane and the Non-Electrostatic models. 3. It is now possible to use different surface complexation models on different surfaces. 4. The charge of the reference surface component is now allowed to be different from zero. For one-pK models, the charge is typically –0.5 by default – this value can be changed by the user. 5. The surface can have a cylindrical or a spherical geometry. 6. Fixed-charge sites can be defined for ion-exchange calculations to permanently charged surfaces 7. Complexation to natural organic matter can be simulated with state-of-the-art models (SHM, NICA-Donnan) 8. In surface complexation models, each surface can have a maximum of six coordination sites and include one fixed-charge site for ion-exchange reactions. 9. Visual MINTEQ can consider counter-ion accumulation in the diffuse layer of charged surfaces 10. Interfacing with Microsoft Excel to facilitate the handling of input and output data. 11. The thermodynamic databases are different, as Visual MINTEQ contains updated and expanded data from the NIST Critical Stability Constants database. However, the database of MINTEQA2 ver. 4.0 can be downloaded and used as well. 1.3 Some technical specifications Visual MINTEQ has been coded in Microsoft Visual Basic *.NET 2005. Microsoft *.NET Framework 1.1 or higher is required for Visual MINTEQ to run. The program will run on most Windows platforms (except ME). Other operating systems are not supported, but Visual 4 MINTEQ has been reported to run under a Windows emulator such as Wine. Microsoft Excel 2003 or higher is required for the interaction with Excel. There are a number of executable (.EXE) files associated with the software. Of these there are two that can be considered being the core of Visual MINTEQ: - The Vminteq EXE file (vminteq13.exe in Visual MINTEQ 3.1) provides most of the interface for Visual MINTEQ. Input files are created, sent to the Mintrun EXE file (see below) and the results are read and presented on the output pages. - The Mintrun EXE file (mintrun13.exe in Visual MINTEQ 3.1) carries out all the calculations. It appears as a black box during runtime. These two EXE files communicate with one another using ASCII text files. More specifically, when the user presses the Run MINTEQ button in the interface, the text file “minin.vda” is created. This file contains all information necessary for the simulation. Mintrun reads in “minin.vda” and when it terminates the calculations, the output will be written to two other ASCII text files, “vmint.out” and “vmint.ou2”, where the former contains all detailed results for each problem, and the latter contains the information used to set up the table Selected sweep results for multi-problem / sweep files. This program structure is admittedly rather old-fashioned. It is inherited from MINTEQA2 ver. 4.0, where the two core .EXE files are “Prodefa2” and “Minteqa2”. Therefore, if the user opens the file “minin.vda”, this represents the last simulation that was carried out by Visual MINTEQ. Also, when the user presses the View output files button from the main menu, Visual MINTEQ will always open the results from the last simulation, which are stored in “vmint.out” and “vmint.ou2”. 1.4 Download and install To install Visual MINTEQ, follow these steps: 1. If this is NOT the first time you install Visual MINTEQ ver. 3.0 on your computer, start with removing the previous installation (go to Control Panel – choose Add or Remove Programs – choose Visual MINTEQ). 2. Double-click on the installation zip file (Vminteq3_setup.zip, available from the Visual MINTEQ webpage). Then double-click on the icon Setup. 3. Follow the instructions during the setup process. It is highly recommended that you install Visual MINTEQ in the default folder. 5 4. When setup is completed, click on the new icon Visual MINTEQ on the desktop. The main menu will open. If this is the first time you install Visual MINTEQ ver. 3.0, a dialog box will appear (see Fig. xx), prompting the user to select the folder for the user- editable files. Select one of the alternatives, save the settings, and return to the main menu. 5. For best performance, decimal points should be used as the decimal symbols instead of decimal commas. 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