Click here to donate to keep PhreeqcUsers open
Welcome,
Guest
. Please
login
or
register
.
Did you miss your
activation email
?
1 Hour
1 Day
1 Week
1 Month
Forever
Login with username, password and session length
Forum Home
Login
Register
PhreeqcUsers Discussion Forum
»
Processes
»
Oxidation and reduction equilibria
»
Turn Off Redox?
« previous
next »
Print
Pages: [
1
]
Go Down
Author
Topic: Turn Off Redox? (Read 2470 times)
JD
Contributor
Posts: 1
Turn Off Redox?
«
on:
May 02, 2016, 07:56:18 PM »
Hi,
I'm new to PHREEQC. I'm trying to model the speciation, pH, and density of a salt mixture in a high ionic strength solution (~8 M). Is there anyway I can turn off the redox reactions?
For example, the following input predicts an initial ~1M NaNO3 solution will have a pH of about 6.5. But then if I react it with nothing (baseline sanity check), I generate a substantial amount of N2 gas and increase the pH to around 12.5.
Example Input:
SOLUTION 3 1M NaNO3
temp 55
pH 7 charge
pe 4
redox pe
units mol/l
density 1
N(3) 1
Na 1
-water 1 # kg
REACTION 3
1 moles in 1 steps
Logged
dlparkhurst
Top Contributor
Posts: 3174
Re: Turn Off Redox?
«
Reply #1 on:
May 02, 2016, 11:39:51 PM »
You can disable the production of N2(aq) by decreasing the log K for the species. Add the block below to your input file. However, there is something else that is getting oxidized, so the nitrogen is just half of the story, and there may be other redox reactions.
Also, with concentrated solutions, it would be better to use the Pitzer approach for solution thermodynamics. Unfortunately, nitrate is not available in pitzer.dat. If you have a limited system, just NaNO3, it should be possible to find interaction coefficients. Not sure how good the density calculation will be even if you go to the effort, because the volume parameters may need fitting.
SOLUTION_SPECIES
2 NO3- + 12 H+ + 10 e- = N2 + 6 H2O
#-log_k 207.08
-log_k 0
-delta_h -312.130 kcal
-dw 1.96e-9
-Vm 7 # Pray et al., 1952, IEC 44. 1146
Logged
MichaelZ20
Top Contributor
Posts: 124
Re: Turn Off Redox?
«
Reply #2 on:
May 04, 2016, 08:46:47 AM »
It should be N(5) instead of N(3) in your input file.
Logged
Print
Pages: [
1
]
Go Up
« previous
next »
PhreeqcUsers Discussion Forum
»
Processes
»
Oxidation and reduction equilibria
»
Turn Off Redox?