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Juan Carlos Burillo

Trace the kinetics dissolution of arsenopyrite

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Hi,

 

Using REACT we want to trace dissolution of arsenopyrite into a wáter in equilibrium with gypsum, jarosite and quartz and calculate the minerals that might dissolved within the shake extraction of 1 gram minetailings waste sample into 20 ml of deionized wáter for 18 hours.

 

We have wáter analysis results after shake extraction and xRD waste results before and after shake extraction. The main minerals found in both xRD are gysum, jarosite, quartz, kaolinite and muscovite.

 

We have 10 wáter analysis in the GSS spreadsheet, we want to launch to SpecE8 and React program

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Hi Juan,

 

React can be used to simulate the kinetics of many different types of reactions, including dissolution and precipitation. For your problem, I think you'll want to start by defining your initial fluid in the Basis pane. You can swap gypsum, jarosite, and quartz into the Basis in order to prescribe equilibrium with those minerals. Take a look at sections 7.1 (Example calculation) and 7.2 (Equilibrium models) for more information about setting up equilibrium models. Section 2 (Getting Started with React) in the Reaction Modeling Guide should also be useful. Then, you would set up a rate law for arsenopyrite dissolution on the Reactants pane. Section 3 (Tracing Reactions paths) and Section 4 (Kinetic Reaction Paths) in the Reaction Modeling Guide should be helpful here.

 

You can launch SpecE8 or React for the samples in a GSS spreadsheet by going to Analysis -> Launch... and selecting the appropriate samples, then clicking Apply. For more information, take a look at section 3.5 in the GWB Essentials Guide.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions

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Hi Brian,

 

We used specE8 to set up the equilibrium model and we founded Mineral Saturation States results: anglesite > barite > gypsum > anhidrite > quartz. Same results were obteined with xRD: gyspsum >>> jarosite > quartz. The initial fluid we used was the "extract" obteined after shake with wáter.

 

The idea is to use deionized wáter as an initial fluid and react it with those minerals.

 

To construct a model using React I have noticed that examples arbitrarily specifiy the amounts of the minerals that coexist with the wáter.

 

The question is: How can we specify the better amounts to construct the model?.

We could use: react 100 mg of gypsum, 5 mg of quartz or 1 free cm3 gypsum

 

Best regards

 

Juan

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Hi Juan,

 

In a model where all you care about is the equilibrium state, the amount of minerals in equilibrium with your fluid doesn't matter. 1 g or 100 grams of Quartz in equilibrium with a fluid will result in the same fluid chemistry. If you're interested in simulating processes, though, the amount of the mineral is important. For example, if you have an oxidized fluid in equilibrium with calcite to which you add some pyrite, the amount of calcite has no effect on the initial state, but it has a great effect on the ability of the fluid to buffer pH as the pyrite dissolves.

 

You can specify mineral mass or volume in a variety of units, so it's easy to set the value appropriate to your system. It's typically best to use the "free" constraint for minerals in equilibrium with your system. So after swapping Quartz into the Basis, 1 free g Quartz indicates that there is one g of the mineral Quartz in the system, plus some amount of dissolved silica (SiO2(aq), H3SiO4-, H2SiO4--, etc.) in equilibrium with the quartz. If you simply said 1 g Quartz, that would indicate that the sum of mineral Quartz and dissolved silica would add up to the 1 g you specified.

 

Hope this helps,

Brian

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Hi Brian,

 

I tried to use React. I specified an initial oxidized fluid (DI wáter ) and swapped to anglesite, jarosite, kaolinite and barite, and reacted 5 cm3 of Gypsum but the program doesn´t converge

The program converge by swaping Quartz for SiO2 only and using Reactants Pane react 5 cm3 of gypsum and 1 cm3 of anglesite, jarosite-K, kaolinite, quartz, barite and gypsum. Also simulate 18 hr test using start-end Basic Pane was useful.

 

Reviewing Results gypsum is a nonestable mineral, its SI changed after 6 hours simulation from unsaturated to saturared as expected.

 

If I open Plot results Pane I found a Piper diagram, I´d like to plot a diagram like 2.2 example: React 400 mg of K-feldspar: Minerals (grams) vs K-feldspar reacted (mg) with my results.

 

Best regards

 

Juan

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Hi Brian,

 

I want to thank you the explanation about specify the amount of minerals in the model, In this case we want to simulate a process so the amount is important for us. I also appreciate your support about the use of the comand "free", I thought it was on the contrary´.

 

Thank you for your help.

 

Can you help me to attach a file into the Fórum?

 

 

Best regards

 

Juan

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Hi Juan,

 

I apologize for the delay in responding. I've just returned to the office from our Fate and Transport Modeling short course in Santiago, Chile.

 

To change your plot type in Gtplot, click Plot at the top and select your desired plot from the pulldown. In this case, select XY Plot... to bring up the XY Plot Configuration dialog. On the X Axis, choose Variable Type "System parameters" then scroll down and select "K-feldspar (or other mineral) reacted" or just "Mass reacted". For the Y axis, you might select Variable Type "Minerals" and plot the minerals that precipitate from your solution. For more info on plotting your data, please see section 6 Using Gtplot in the Reaction Modeling Guide.

 

You can attach a file to the forum (for example, a .rea file) by clicking "More Reply Options." Click "Choose File" and browse to select the appropriate file, then click "Attach This File."

 

Hope this helps,

Brian

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Hi Brian,

 

 

Very helpful !, thaks again for your help. I will try to change plot type with your support.

I am trying to reproduce an EH-pH diagram I founded in an article where Act2 was used, I used same pressure.temperature and log activities conditions include in the article but I didn´t find jarosite-K, Piryte and Gypsum, nevertheless the graph is very similar. As (arsenic) species at low pH formed as expected. Also I tried to plot an pH-Eh diagrams using Zn and Pb species.

I attached these files

 

 

Best regards

 

 

Juan

arsenopirita.ac2

anglesita.ac2

anglesita en agua desionizada.rea

esfalerita.ac2

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Hi Juan,

 

For an Eh-pH diagram to include Jarosite-K, Pyrite, and Gypsum, you would need to choose a sulfur species, like SO4--, as the main species to diagram. Orpiment, Arsenopyrite, and other sulfur species with arsenic could possibly plot on a diagram like this.

 

There are a few other items to consider. First, you should verify that the thermo data you're using matches what was used in the published diagram. If necessary, you can temporarily change equilibrium constants (see 3.3 alter in the GWB Reference Manual) or add new species to your thermo dataset (see 9 Using Tedit in the GWB Essentials Guide). Second, some stable species may have been suppressed in favor of less stable species (see 6.2 Solubility diagrams in the GWB Essentials Guide or 3.53 suppress in the GWB Reference Manual). Finally, complexing ligands (those that appear in the "in the presence of" section) may have been allowed to speciate over the X and/ or Y axes of the diagram (see 5.3 Mosaic diagrams in the Essentials Modeling Guide).

 

If that doesn't help, could you attach a picture of the diagram that you're trying to reproduce?

 

Best,

Brian

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Hi Brian,

 

I apologize for the delay in responding. I was in water sampling performances. I also think that thermo data must be changed or equilibrium constants modified /add temporaly. I appreciate the specific seccions of the GWB Essentials Guide and GWB Reference Manual you share us. I am studyng the sections you recomended us on the Guides.

 

I am attaching a picture of the diagram I¨m trying to reproduce. GWB 10.0 pictures are included too.

 

Best regards

 

Juan

arsenopyrite.docx

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Hi Juan,

 

In an activity diagram, like those produced by Act2, the choice of the "diagram species," also known as the "main species," is important. If you choose an arsenic species, for example, then all species that appear on the diagram must be some form of arsenic, depending on the conditions of the diagram (Eh, pH, S, K, Ca, etc.). If you choose a sulfur species as the main species, then all species on the diagram will be some form of sulfur. The diagrams you're trying to reproduce have SO4-- as the main species but you've set AsO4--- to be the main species, so you get different results.

 

Best,

Brian

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Hi Brian,

 

Thanks again, you were right, I made the changes you suggest and identical graphs appear magicaly!!!.

As you say "diagram species" are really important to model with Act2.

 

I am attaching a graph that explains us correctly the main species that dissolve when react a minetailing sample with ID water during 18 hr water shaking.. Our next step will be to react the fluid that is obtained after shake process (as initial fluid) with minerals found in soil and rocks

 

To be continue...

 

Best,

 

Juan

extracción secuencial con agua desionizada.rea

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Hi Juan,

 

I'm glad to hear that the suggestion helped. Good luck with the modeling.

 

Cheers,

Brian

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Hi Brian,

 

I need your support on plottind my data. Using GSS I launch to SpecE8 and obtain a Gtplot that can be a Piper plot or a SI plot which graphs all minerals. As all minerals appear I hide some of them to obtain a better graph. When I reopen the Gtplot file all minerals appear again. I´d like to mantain the graph in the same shape when I reopen the file. Same situation happens when I plot other graphs like React. I think the program "remembers" the last X-Y editing axes and reuse it on the next plot.

 

Best regards

 

Juan..

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Hi Brian,

 

I´ve found that It´s easy to actualízate or mantain plots using the rute: File > update plot data ; x-y plot configuration consider "All minerals" or "Ca++, Zn, SO4-- minerals", so you can view on the graph all minerals curves or a few ones, it´s up to your needs. Also "hide this mineral" option fits the graph according to your objetives.

 

Best

 

Juan


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