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Mass of water question
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Topic: Mass of water question (Read 759 times)
Olasz Tamas
Frequent Contributor
Posts: 11
Mass of water question
«
on:
January 21, 2021, 01:23:31 PM »
Dear Community!
I am confused by how PHREEQC determines mass of water. Below I will put my working model for a red mud sample for which I am trying to determine its equilibrium composition. However, if I put in 0.2 kg for the mass of water for the initial solution, and I equilibrate it with minerals present in red mud, after the reaction the mass of water becomes 0.77. Where does the water come from in this case? Or does PHREEQC recalculate for 1kg of water somehow? I am using the llnl database for this case.
My code:
SOLUTION 1
temp 25
pH 7 charge
units mol/kgw
density 1
-water 0.2 # kg
PHASES
NdPO4
NdPO4 = PO4-3 + Nd+3
log_k -26.2
Nd2(CO3)3
Nd2(CO3)3 = 3 CO3-2 + 2 Nd+3
log_k -33
Nd(OH)3
Nd(OH)3 + 3 H+ = 3 H2O + Nd+3
log_k 18.09
NdCl3
NdCl3 = Nd+3 + 3 Cl-
log_k -4.16
Nd2(SO4)3
Nd2(SO4)3 = 2 Nd+3 + 3 SO4-2
log_k -12.515
SOLUTION_SPECIES
Nd(CO3)2- = 2 CO3-2 + Nd+3
log_k -12.73
Nd(SO4)2- = Nd+3 + 2 SO4-2
log_k -5.1
Nd2(OH)2+4 + 2 H+ = 2 H2O + 2 Nd+3
log_k 13.894
NdCO3+ = CO3-2 + Nd+3
log_k -7.53
NdOH+2 + H+ = H2O + Nd+3
log_k 7.997
NdSO4+ = Nd+3 + SO4-2
log_k -3.66
EQUILIBRIUM_PHASES 1
Corundum 0 2.88
Quartz 0 3.84
Hematite 0 4.64
Anatase 0 0.88
Shcherbinaite 0 0.02
Lime 0 6.47
Periclase 0 0.43
Zincite 0 0.01
Pyrolusite 0 0.09
Afwillite 0 0
Akermanite 0 0
Albite 0 0
Albite_high 0 0
Albite_low 0 0
Amesite-14A 0 0
Analcime 0 0
Andalusite 0 0
Andradite 0 0
Anorthite 0 0
Anthophyllite 0 0
Antigorite 0 0
Aragonite 0 0
Beidellite-Ca 0 0
Beidellite-H 0 0
Beidellite-Mg 0 0
Boehmite 0 0
Brucite 0 0
Burkeite 0 0
Ca-Al_Pyroxene 0 0
Ca2Al2O5:8H2O 0 0
Ca2V2O7 0 0
Ca3V2O8 0 0
Ca4Al2O7:13H2O 0 0
Ca4Al2O7:19H2O 0 0
CaAl2O4 0 0
CaAl2O4:10H2O 0 0
CaAl4O7 0 0
Calcite 0 1.14
CaV2O6 0 0
Chalcedony 0 0
Chrysotile 0 0
Clinochlore-14A 0 0
Clinochlore-7A 0 0
Clinoptilolite-Ca 0 0
Clinoptilolite-dehy-Ca 0 0
Clinoptilolite-hy-Ca 0 0
Clinoptilolite-hy-Na 0 0
Clinoptilolite-Na
Clinozoisite 0 0
Coesite 0 0
Cordierite_anhyd 0 0
Cordierite_hydr 0 0
Cristobalite(alpha) 0 0
Cristobalite(beta) 0 0
Dawsonite 0 0
Diaspore 0 0
Dicalcium_silicate 0 0
Diopside 0 0
Dolomite 0 0
Dolomite-ord 0 0
Enstatite 0 0
Epidote 0 0
Epidote-ord 0 0
Ferrite-Ca 0 0
Ferrite-Dicalcium 0 0
Ferrite-Mg 0 0
Ferrite-Zn 0 0
Forsterite 0 0
Foshagite 0 0
Gaylussite 0 0
Gehlenite 0 0
Gibbsite 0 0
Gismondine 0 0
Goethite 0 0
Grossular 0 0
Gyrolite 0 0
Hatrurite 0 0
Hillebrandite 0 0
Jadeite 0 0
Kaolinite 0 0
Katoite 0 0
Kyanite 0 0
Larnite 0 0
Laumontite 0 0
Lawsonite 0 0
Margarite 0 0
Merwinite 0 0
Mesolite 0 0
Mg2V2O7 0 0
MgV2O6 0 0
Mirabilite 0 0
Monticellite 0 0
Montmor-Ca 0 0
Montmor-Mg 0 0
Montmor-Na
Na2CO3 0 0
Na2CO3:7H2O 0 0
Nahcolite 0 0
Natrolite 0 0
Natron 0 0
Nepheline 0 0
Nontronite-Ca 0 0
Nontronite-H 0 0
Nontronite-Mg 0 0
Nontronite-Na 0 0
Okenite 0 0
Paragonite 0 0
Pirssonite 0 0
Portlandite 0 0
Prehnite 0 0
Pseudowollastonite 0 0
Pyrophyllite 0 0
SiO2(am) 0 0
Rankinite 0 0
Ripidolite-14A 0 0
Ripidolite-7A 0 0
Rutile 0 0
Saponite-Ca 0 0
Saponite-H 0 0
Saponite-Mg 0 0
Saponite-Na 0 0
Scolecite 0 0
Smithsonite 0 0
Sepiolite 0 0
Sillimanite 0 0
Spinel 0 0
Talc 0 0
Thenardite 0 0
Tobermorite-11A 0 0
Tobermorite-14A 0 0
Tobermorite-9A 0 0
Tremolite 0 0
Tridymite 0 0
Wairakite 0 0
Wollastonite 0 0
Xonotlite 0 0
Zincite 0 0
Zn2SiO4 0 0
Zn2TiO4 0 0
ZnCO3:H2O 0 0
Zoisite 0 0
Na2O 0 2.92
Gypsum 0 0.29
Whitlockite 0 0.11
O2(g) -0.679 10
CO2(g) -3.5 10
NdPO4 0 0
Nd2(CO3)3 0 0
Nd(OH)3 0 0.002784
NdCl3 0 0
Nd2(SO4)3 0 0
end
Logged
dlparkhurst
Top Contributor
Posts: 2736
Re: Mass of water question
«
Reply #1 on:
January 21, 2021, 03:58:02 PM »
I am a little skeptical of the set of minerals that you are including.
However, the mass of water is calculated as part of the equilibration. A simple example would be dissolution of gypsum, where the mass of water will increase as gypsum dissolves because of the formula CaSO4:2H2O. Other reactions also produce water Fe(OH)3 + 3H+ = Fe+3 + 3H2O, for example. The number of moles of H and O is conserved between the initial solution and the moles of minerals initially present.
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Olasz Tamas
Frequent Contributor
Posts: 11
Re: Mass of water question
«
Reply #2 on:
January 21, 2021, 05:07:44 PM »
Thank you for your answer!
The minerals included are those that had a SI close to 0 or higher in the initial output file (without allowing any minerals to precipitate). Later I also mix the sample with different acids (HCl, HNO3, H3PO4, H2SO4) so all minerals are included which can form. But only 10-15 of these actually precipitate or dissolve along the process.
Yes I was thinking about the minerals "releasing" water as well, but the minerals that have inital amounts are all oxides, and in smaller amounts calcite, gypsum and whitlockite. So there is no H in any of them, how is it still possible that the amount of water increases?
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dlparkhurst
Top Contributor
Posts: 2736
Re: Mass of water question
«
Reply #3 on:
January 21, 2021, 09:05:37 PM »
I think by default you introduced 10 moles of Montmor-Na and Clinoptilolite-Na. Setting these to zero, you get a decrease in water mass by about 75% due to the dissolution and precipitation reactions.
Logged
Olasz Tamas
Frequent Contributor
Posts: 11
Re: Mass of water question
«
Reply #4 on:
January 22, 2021, 09:04:27 AM »
Oh well, now I feel stupid I didn't check thoroughly. But I guess thats why you define only the relevant minerals so you dont get lost. Thank you so much for your help.
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