Jump to content
Geochemist's Workbench Support Forum

All Activity

This stream auto-updates     

  1. Yesterday
  2. Hi Ozan, You are welcome. Best, Jia
  3. Jia Wang

    O2 release from CaO2

    Hello C. Penna, I took a quick look at your script and it seems like you have set a combined volume for the system to be greater than 100 percent. I suggest you leave medium properties at default settings unless you are specifying a porous medium from your field site or experiment. The program will calculate the porosity and volume minerals base on your entries in the basis pane. You might also want to start at 0 for the rate constant to make sure that entries in the basis pane and the rest of the system is set up correctly before starting to add in your redox reaction. Once your initial system is set up in the way you want and is able to run without the reaction, then increase the rate constant. Additionally, I noticed that you have O2(g) fugacity fixed right now in the Reactants pane. In this case, the fixed fugacity is calculated from the initial O2(aq) concentration in your basis pane. Usually a fixed gas reactant is set for modeling systems buffered in nature by contact with a gas reservoir such as the atmosphere or in a controlled laboratory setting. If you fix the fugacity of O2(g), your O2(aq) concentration will to equilibrate with the fugacity which would not change throughout the simulation. You might want to reconsider this constraint for your system. Hope this helps. Best regards, Jia
  4. Last week
  5. C Penna

    O2 release from CaO2

    Hi Jia, Thanks for the response. I was able to successfully add in CaO2 as a redox within the thermo dataset. And then was able to create a coherent expression in Rxn for CaO2 and H2O, however I am having issues with the React application. I have tried altering the input values and seem to keep coming up with errors, mostly stating that my "porosity of node 0 is too small". I am not sure how to proceed from here. Could you provide feedback on any issues with my parameters? Thank you, C CaO2penna.rea thermopenna.tdat
  6. Thank you very much! I will be careful about that. Best, Ozan Turkes
  7. Jia Wang

    O2 release from CaO2

    Hello C. Penna, I would suggest you add the species CaO2 as a redox species into the thermo database to start. If CaO2 species is generally unstable then you can put in sufficiently large Log K values to ensure that CaO2 is thermodynamically unstable. For more information, please refer to section 9 in the GWB Essentials Guide for adding new entries into the database. I recommend you save the database with a new file name such as ‘thermo+CaO2.tdat’ to preserve the original file. Then in the GWB application you are using for your simulation (React, X1t, X2t), use the decouple dialog to decouple CaO2. This allows you to add in CaO2 as a basis species in your basis pane. You can then specify a kinetic redox reaction and an intrinsic rate constant in the reactants pane for your system to regulate the rate at which CaO2 dissociates in your system. Additionally, you might also want to consider a custom rate law as well for your reaction. GWB defaults to a built in general rate law form but you can customize your own rate law according to observations or experimental data. For more information, please refer to Section 5 in the GWB Reaction Modeling Guide. If you have any further questions, please include your input files. Best Regards, Jia Wang
  8. Hi Ozan, You're allowed to move the software three times before requiring a reset from us. I have reset your license and you should now be able to deactivate now. I hope you enjoy using the software. Best, Jia Wang
  9. Luis C. Savanguane

    Kinetic of complexation and sorption model

    Dear all! I am Luis Savanguane, learning how to use GWB. 1. I want to know how GWB calculate pH, species concentration and mineral precipitation after get the kinetic reaction rate on kinetic of complexation and sorption model (react)? Can I get the equations to quantify species contraction and pH change? 2. How to introduce (consider) inhibitors on modeling. 3. How to add mineral as reactant ? Sincerely
  10. Hi, I am getting the error 7466 ; The return of the fulfillment is denied by the return policy because max return exceed. I would be happy if you could help with this issue. Thanks! Ozan
  11. Hello Frank, Sorry for the late response. There are several options to set heterogeneous mineral mass distribution in X1t and X2t. X1t and X2t require the initial system to be configured with a single set of basis species. Therefore, an equilibrium mineral in the initial pane must be have some mass present in every node in order for the program to equilibrate the fluid with the mineral. For this reason, you would not be able to set a zero mineral mass for an equilibrium mineral. You can, however, set a heterogenous distribution for its abundance in the initial pane. For more information, please refer to the Heterogeneity Appendix in the GWB Reactive Transport Modeling Guide. Kinetic minerals are a different story. For purely kinetic minerals (those not swapped into the basis), you can set their abundance heterogeneously on the Reactants pane. There’s no issue with setting a reactant mineral in some nodes and no mass in others. For each kinetic mineral using the built-in rate law, you can supply a specific surface area (m2/g), which gets multiplied by the current mass to calculate the surface area. This property can also be set heterogeneously. Going back to the issue of different equilibrium minerals, you could alternatively write a simple flow program that uses ChemPlugin instances to figure reaction and transport. ChemPlugin is a self-linking software object based off the GWB’s compute engine. You spawn a ChemPlugin instance for each nodal block, and there’s no requirement that each instances uses the same set of basis species, so you can configure each instance in equilibrium with different minerals. To learn more about ChemPlugin, you can visit the ChemPlugin page. Hope this helps. Best, Jia
  12. I am trying to show the reaction release of CaO2 to O2 for remediation of benzene-impacted groundwater in a system. However, I cannot find an equilibrium constant value for the reaction of CaO2. How can I go about having this reaction in GWB? What is the best way to show benzene degradation through use of added O2?
  13. Hi Frank Don't know If I understand your problem correctly. Will it help if you make a copy of the mineral in the database: e.g. calcite1 and calcite2 and then give it the different surface areas you want in the model?
  14. Earlier
  15. Brian Farrell

    Saturation index for sulfides

    Hi Silvain, The reaction for Pyrite in the LLNL dataset, thermo.tdat, is shown below: Pyrite + H2O = Fe++ + 1.75 HS- + .25 SO4-- + .25 H+ You’ll notice that the reaction is written in terms of the basis species SO4-- and the redox species HS- because the oxidation state of sulfur in pyrite is between that of SO4-- and HS-. When the reaction gets loaded into an app like Rxn, SpecE8, or GSS, though, it’s rebalanced to be in terms of the basis species only: Pyrite + H2O + 3.5 O2(aq) = Fe++ + 2 SO4-- + 2 H+ This is because each of the apps assume that redox coupling reactions are enabled by default. In any case, to be able to calculate a saturation index for a mineral like pyrite, you need a way to constrain every species in the reaction. So in addition to adding Fe++ and SO4-- to your spreadsheet, you need to add O2(aq) (or Eh or pe), as well as pH. In this case, the concentration you set for the SO4-- component should represent all the sulfur in the system. The program uses the oxidation state you supply to find the equilibrium distribution of mass between sulfate and sulfide species. You can alternatively decouple HS- from SO4-- to set up a disequilibrium model. This is done from the Config > Redox Couples dialog in Rxn and SpecE8, and from Data > Redox Couples in GSS. Alternatively, simply adding the redox species HS- to your spreadsheet triggers HS- to be decoupled from SO4--. In this case, you don’t need to supply a measure of oxidation state, but you do need to provide separate measurements for the SO4-- and HS- entries. Hope this helps, Brian Farrell Aqueous Solutions LLC
  16. Jia Wang

    How can i make the sorption isotherm?

    Hello Jeonghwan, To simulate sorption in GWB, prepare a surface dataset for the ion of interest. You can refer to section 2.5 for more information on the various sorption models in GWB Essentials Users Guide and section 9.2 for more information on how to edit or create new surface datasets. Using React, you can set up a simulation to titrated the ion of interest into a system and observe the mass of ion sorbed based on the sorption model (Kd, Freundlich, Langmuir) of your choice. Note that for the Kd and Freundlich approach, you would need to completely specify mineral mass, including both equilibrium and kinetic minerals as well as any inert volume. You can do so by setting a low concentration of the ion in interest in the basis pane and then in the Reactants pane, select ‘add’ --> ‘Simple’ --> ‘Aqueous’--> name of species. Enter the total quantity you want to titrate in through the simulation and run the simulation. Plot the amount of ions in solution vs. the total concentration of ions sorbed from your simulation. Note that mass of ions sorbed per unit of solid mass is not a unit you can select in Gtplot. To convert to mass of ions sorbed per mass of soil, I would recommend copying the total sorbed mass from each simulation and divide by the total mass of soil in excel or a similar program. You can then replot your results in the desired units Hope this helps. Best Regards, Jia
  17. Silvain Rafini

    Saturation index for sulfides

    Hi Brian I'm currently making may first steps using GWB. I'm trying to calculate mineral saturation indexes for some sulfide minerals (pyrite, sphalerite, chalcopyrite, galene) that do not appear in the default list as proposed by GSS. Equilibrium constants for the dissolution reactions of these mineral are in the thermo.tdat file (more or less the LLNL database), then I can not figure why GSS do not propose it by default. Of course, my dataset includes Zn and SO4 concentrations. Thanks for helping. Silvain
  18. Is there a way to do kinetic isotopic exchange as in Druhan et al. GCA 2013? I have a system that recrystallizes calcite due to hot fluid circulation and I've read some papers that look at closure temperatures for isotopes. Currently I have a kinetic transformation from a (segregated) low ordered to a (unsegregated) hydrothermal calcite. I was just wondering if there was a cleaner way. Crunchflow, as used in the original paper, doesn't do heat flow for some reason and so isn't an option. Thanks, Peter
  19. Hi, My name is Jeonghwan Hwang. I am studying about sorption isotherm, and i want to make a sorption isotherm using GWB. However, i cannot find how to make isotherm in any tutorial or workshop material. Can i make the sorption isotherm? I attached a sample which was resulted by PHREEQC. I wonder if I can make a figure like this. Thank you for kind reading. Sincerely, Jeonghwan Hwang
  20. It seems that when units of mmol/L_as_CaCO3 are used for carbonate alkalinity in GSS (GWB12) they are being read as mol/L. If I enter a value of 1 for carbonate alkalinity in units of mmol/L_as_CaCO3 and convert to meq_acid/l the value returned is 2000 rather than 2.
  21. Hello Kaizen, I took a look in your input file and here are a couple of suggestions. To look at the speciation of La+++, you would need to add the species and the associated Log Ks for the reactions into the database. Without your thermo file, I am guessing that you might want to check whether or not the species you are interested in are all there and double check the Log K values. Please refer to section 9.2.3 in the GWB Essentials Guide for more information. React defaults to using Cl- as the balancing species but in this case you might not need to have a charge balancing species since you are generating a speciation diagram. You can turn off balance species by clicking on the units of a species and select do not balance. You can then eliminate Cl- from your basis pane. Lastly, note that La(OH)3 is a mineral in the thermo.V8.R6+.tdat database. If the mineral precipitates, you will be able to see its calculated quantity under the variable type: ‘Mineral’ and not under ‘Species concentration’. Hope this helps. Best, Jia Wang
  22. Hello Jia, I followed your suggestions and that solved the problem. Thank you for your help, I appreciate it! All the Best, Bob
  23. Hi, I am trying to generate a simple La3+, LaOH2+, La(OH)2+, La(OH)3 speciation diagram in React but so far I have been unsuccessful with my approach (attached). Eventually, I want to be able to add in other species. So guidance on this 101 problem will be very much appreciated. Many thanks! La React file.rea
  24. Hello Bob, Thanks for attaching your input file. I noticed a few things in your input file that might be the problem. Here are a couple of suggestions that might help. Methane is not one of the basis species available in the thermo.tdat dataset. You can swap it into the basis pane as you have done so by swapping CH4(g) for H+. However, in doing so, you are setting the reaction H+ + H2O + HCO3- = CH4(g) + 2 O2(aq) to fix pH. I am not sure if this is what you want to do. If you wish to set both bicarbonate and methane gas concentrations in your initial system, I would suggest you engage disequilibrium by decoupling CH4(aq) and HCO3- in the Redox Couples dialog. By disengaging equilibrium between HCO3- and CH4(aq), you can enter the species of CH4(aq) as a basis species into your initial condition, which then you can swap for CH4(g). This would also eliminate the need to have to enter O2(aq) as part of your basis constraint. Another thing to consider is the value used for the partial pressure of the methane in your basis pane. The value entered should the partial pressure of CH4(g) in your reservoir and not the confining pressure. For more information, please refer to section 7.5 Gas Partial Pressure in the GWB Essentials Guide for more information. Currently, you cannot fix the confining pressure of the system in Speciate. Hope this helps. Best Regards, Jia Wang
  25. Hello Rob, If you’re doing a simple calculation of the equilibrium state of your wastewater, or making an Eh-pH diagram or stability diagram of some sort, there’s nothing extra to incorporate. You can certainly account for the effects of microbes in a process model, however. Please note that a mineral still has to reach saturation to precipitate. Microbes can catalyze redox reactions that are thermodynamically favored, but kinetically limited. I’m not especially familiar with the details of biological wastewater treatment, but perhaps the byproducts of microbial metabolism (e.g. NH4+ from dissimilatory NO3- reduction) help drive the saturation of struvite. If you’re interested in simulating the effects of microbial metabolism and growth, you’ll probably want to use a kinetic rate law in React. A simple option is to use an enzyme-mediated reaction to predict the influence on species concentrations. In enzymatic catalysis, a substrate combines with an enzyme to form an activated complex, which can decay to give a catalytic product. React can also consider more complex models of microbial metabolism and growth, including competing strains. Perhaps a good place to start is chapter 4.6.2 (Enzymes and biotransformation) and chapter 4.7(Microbial metabolism and growth) in the GWB Reaction Modeling Guide. Best regards, Jia Wang
  26. Hi Jia, Here is the file with the mixed water sample that I am trying to speciate. Thanks, Bob GSS_Mix.sp8
  27. Hi! I would like to model a 2D transport calculation with two spatially separated mineral phases. Is this possible to set up a model with different minerals in different blocks? And, due to the effects of grain boundaries and surface roughness, is it somehow possible to have different surface areas for the minerals in different blocks? Thanks in advance and best regards, Frank
  28. Misato Shimbashi

    Change nucleus density in X1t

    Dear Jia Thank you for your reply. It is now possible. Thank you. Misato
  1. Load more activity