[Pyrite dissolution in batch reactor]

Hi Brian,
I've attached two react files. The first, FeS2_Kin_7Jan2016#1.rea, uses the custom rate law you suggested in your previous post; unfortunately, I wasn't able to use "soln_vol" in my GWB version.

 

In the second file, FeS2_Kin_5Jan2016#11c.rea, I entered a constant value for O2(aq) and set the rate constant equal to k * A/V. In this run, the amount of pyrite that reacts more closely resembles what was observed/measured in the experimental system; however, the system is still saturated with pyrite.

 

In all of the simulations, I decoupled all relevant redox pairs.

 

Thanks for your help; I really appreciate it!

 

Amy

FeS2_Kin_7Jan2016#1.rea

FeS2_Kin_5Jan2016#11c.rea

[Pyrite dissolution in batch reactor]

Hi Brian,

Thanks for your help!

 

When I set up the basis using the inputs above (pH = 3; DO = 12 mg/kg free), the system becomes saturated with pyrite in <3 hours, when I don't think it should be - there is only 5.355 gr of pyrite in the system. I've tried entering a couple of different rate laws, with mixed results.

 

The main issue is that when the system is unsaturated with respect to pyrite, the amount of pyrite that reacts is much too low.

 

Is there anyway to constrain the pe of the system, if pH is fixed and DO is maintained?

 

Best,

Amy

[Pyrite dissolution in batch reactor]

Hi,

I am trying to modeling pyrite dissolution in a batch reactor, but I'm having issues getting reasonable results. I think part of the issue is how I'm entering the rate law (?). I’ve tried multiple configurations, but have been unsuccessful. I’ve looked over Sxn 31.1 in the text book, as well as Ch.5 in the Reaction Modeling Guide.

I’ve attached the experimental parameters, GWB input and results of the simulations. The experimental runs were over a 24 hour period; at the conclusion of the experiments, <2% of the total pyrite had dissolved.

Any insight is appreciated!

Many thanks, in advance, for your time!

Amy

PyriteDiss-GWB_23Dec2015_forumv2.pdf

React_output_GSS_1_23Dec2015.txt

React_output_GSS_3_23Dec2015.txt

React_output_GSS_5_23Dec2015.txt

[Pyrite Oxidation: Batch Reactor]

Hello,

 

I'm trying to look at your script, but I notice a few issues/ omissions in the script. What unit are you using to constrain the mass of Pyrite? The time units of your simulation were not saved correctly (it says hou in your script). Perhaps GWB isn't saving your script correctly. Which version are you using?

 

Thanks,

 

Brian Farrell

Aqueous Solutions LLC

 

Hi Brian,

Thanks for your help. I'm trying to model the experimental setup in Liu (2008). I used "grams" to constrain the mass of pyrite. I think the time units are correct: I want to see what Fe species are in solution after 24 hours. I tried to enter one of the rate laws calculated in the manuscript, but am having issues with how to deal with the oxygen.

 

I re-saved the script and attached the file. I also captured screen shots, if that helps. I'm using GWB 8.0 Pro. I checked for updates and the computer says I'm up to date.

 

Thanks so much for your help! I appreciate it.

PyriteOxidation_11June.rea

[Pyrite Oxidation: Batch Reactor]

Hi. I'm trying to model pyrite oxidation in a batch reactor (Liu et al 2008). Both pH and the concentration of dissolved oxygen in the system is held constant (at 3 and 9-12 ppm, respectively).

• pH is maintained by through discrete additions of HCl or NaOH
  
• The concentration of dissolved oxygen was maintained by controlling the oxygen partial pressure in the reactor headspace
  

 

When I try to fix O2 in the Reactants window, I get a convergence error. As soon as I "unfix the O2", the program is able to arrive at a solution.

 

I'm new to GWB, so any advice is greatly appreciated! Many thanks, in advance, for your time!

PyriteOxidation_8June_v2.rea