PHREEQC

[Cheryl Halim <cheryl.halim@xxxxxxxxxxxxxxxxxxx>]

Dear Prof. Parkhurst,
My name is Cheryl from the University of New South Wales, Australia. I'm 
doing a PhD on the investigation of the mechanism of heavy metal 
leaching from different wastes. I'm currently trying to model my results 
using PHREEQC. However, noone here knows how to use it nor that I have 
much background in programming. I wonder if you can help me.
I've tried to set up a PHREEQC input file. This is attached in this 
email. Some of the data and formulae that I put in the file are not 
right. I just want them to work first, which hasn't been the case yet. I 
defined the phases that I need using the PHASES keyword. I plan to have 
model my cement system using SOLID_
SOLUTION. This cement consists of:
Leadhydroxide        2.3 moles/kg of cement
Calciumhydroxide    4.97
Aluminiumhydroxide    0.04
Ferrichydroxide        0.03
Magnesiumhydroxide    0.02
CaO(x)SiO2(y)H2O(1-x-y)            1.42 (Calcium silicate)
CaO(x)Al2O3(y)H2O(1-x-y)            0.22 (Calcium aluminate)
CaO(x)Al2O3(y)Fe2O3(z)H2O(1-x-y-z)        0.10
 I'm not sure if I can use SOLID_SOLUTION for a solid like cement. I 
actually defined the calcium silicate and calcium aluminate in the 
SOLID_SOLUTION as well as I plan to use it when I define the cement. Can 
I actually do that?
My problem so far has been to define the SiO2 phase and other phases 
(the calcium silicate and aluminate species). If I want to define a 
PHASE, as I understand, I have to put a dissolution reaction. However, 
SiO2 does not dissociate forming Si+4 ion like Pb does (Pb(OH)2 = Pb+2 + 
2OH-).
SiO2 reacts with H2O forming H4SiO4, which is present in the PHREEQC 
database.
Can you suggest me with anything here?
In addition, I can't also define the dissolution reaction for other 
oxides, e.g. CaO. CaO will just react with water forming Ca(OH)2, which 
will dissociate forming Ca+2 + 2OH-. How do I go about this?

When I have finished defining the SOLID_SOLUTION, I plan to mix the 
cement with acetic acid. The H+ from the acid will react with the 
Ca(OH)2, releasing heavy metals from the cement to the leachate. I have 
no idea how to approach this, but I will also try to think about this 
after I figure out the formation of the cement in the SOLID_SOLUTION.

Thank you very much for your attention. I hope you can suggest me with 
something.

With kind regards,
Cheryl



TITLE Kinetic of leaching of Pb from cement

SOLUTION_MASTER_SPECIES
Ac	    Ac-	        0.0	60.00		60.00
Cd(2)    Cd+2		   0.0	112.4
Pb(2)    Pb+2		   0.0	207.19
Si	    H4SiO4		   0.0	SiO2		28.0843
Ca	    Ca+2		   0.0	Ca		40.08	
SOLUTION_SPECIES
#Acetic acid
Ac- = Ac-
        log_k   0.0;    		-gamma  1e7   0.0
Ac- + H2O = HAc + OH- 
        log_k   4.75;   		-gamma  1e7   0.0
#Lead species
Pb+2 = Pb+2
        log_k   0.0;    		-gamma  1e7   0.0	
Pb+2 + H2O = Pb(OH)+ + H+
        log_k   -7.71;    		-gamma  1e7   0.0
Pb+2 + 2H2O = Pb(OH)2 + 2H+
        log_k   -17.12;    	-gamma  1e7   0.0
Pb+2 + 3H2O = Pb(OH)3- + 3H+
        log_k   -28.06;    	-gamma  1e7   0.0
2Pb+2 + H2O = Pb2(OH)+3 + H+
        log_k   -6.36;    		-gamma  1e7   0.0
4Pb+2 + 4H2O = Pb4(OH)4+4 + 4H+
        log_k   -20.88;    	-gamma  1e7   0.0
6Pb+2 + 8H2O = Pb6(OH)8+4 + 8H+
        log_k   -43.61;    	-gamma  1e7   0.0
#Silicate species
H4SiO4 + H2O = H3SiO4- + H+ + H2O
        log_k   -9.9;    		-gamma  1e7   0.0
H3SiO4- + H2O = H2SiO4-2 + H+ + H2O
        log_k   -9.9;    		-gamma  1e7   0.0
CO2 + 2H2O = HCO3- + H+ + H2O
        log_k   -13.31;    	-gamma  1e7   0.0
HCO3- + H2O = CO3-2 + H+ + H2O
        log_k   -6.4;    		-gamma  1e7   0.0
END


PHASES
Calciumhydroxide
        Ca(OH)2 = Ca+2 + 2OH-
        log_k   -5.3
Leadhydroxide
        Pb(OH)2 = Pb+2 + 2OH-
        log_k   -19.84
Aluminiumhydroxide
        Al(OH)3 = Al+3 + 3OH-
        log_k   -33.52
Ferrichydroxide
        Fe(OH)3 = Fe+3 + 3OH-
        log_k   -38.55
Magnesiumhydroxide
        Mg(OH)2 = Mg+2 + 2OH-
        log_k   -11.2
Calciumcarbonate
	   CaCO3 = Ca+2 + CO3-2
	   log_k	-10.3
SiO2(a)
	SiO2 + 2 H2O = H4SiO4
	log_k	-2.71
	delta_h  3.340 kcal
	-analytic	-0.26	0.0	-731.0
Chalcedony
	SiO2 + 2 H2O = H4SiO4
	log_k	-3.55
	delta_h  4.720 kcal
	-analytic	-0.09	0.0	-1032.0
Quartz
	SiO2 + 2 H2O = H4SiO4
	log_k	-3.98
	delta_h  5.990 kcal
	-analytic	0.41	0.0	-1309.0
H2O
	H2O = OH- + H+
	log_k	-14.0
	delta_h 13.362	kcal
	-analytic	-283.971	-0.05069842	13323.0	102.24447	-1119669.0
CaO
	CaO + H2O = Ca+2 + 2OH-
	log_k	-4
Al2O3
	Al2O3 + 3H2O = 2Al+3 + 6OH-
	log_k	-4
Fe2O3
	Fe2O3 + 3H2O = 2Fe+3 + 6OH-
	log_k	-4
END
SOLUTION 0 #0.1 mol/L Acetic acid
        units mol/l
	   pH  2.88
        Ac  0.1
SOLID_SOLUTIONS 1 
		CaO(x)SiO2(y)H2O(1-x-y)
			-comp		CaO				3
			-comp		SiO2				2
			-comp		H2O				3
SOLID_SOLUTIONS 2 
		CaO(x)Al2O3(y)H2O(1-x-y)
			-comp		CaO				4
			-comp		Al2O3				1
			-comp		H2O				1
SOLID_SOLUTIONS 3 
		CaO(x)Al2O3(y)Fe2O3(z)H2O(1-x-y-z)
			-comp		CaO				4
			-comp		Al2O3				1
			-comp		Fe2O3				1
			-comp		H2O				1

SOLID_SOLUTIONS 4 Cement containing Pb
		CementPb
			-comp		Leadhydroxide		2.3
			-comp		Calciumhydroxide	4.97
			-comp		Aluminiumhydroxide	0.04
			-comp		Ferrichydroxide		0.03
			-comp		Magnesiumhydroxide	0.02
			-comp		CaO(x)SiO2(y)H2O(1-x-y)			1.42
			-comp		CaO(x)Al2O3(y)H2O(1-x-y)			0.22
			-comp		CaO(x)Al2O3(y)Fe2O3(z)H2O(1-x-y-z)		0.10
			-comp		Calciumcarbonate	0	
RATES
Ca_Ac
-start
10  moles = (-128.67 * Ca + 244216) * TIME
200 SAVE moles
-end
SELECTED_OUTPUT
        -file kineticPbcement.sel
        -reset false
USER_PUNCH
-headings time Ca pH
10 PUNCH TOTAL_TIME/3600, TOT("Ca"), -LA("H+")
INCREMENTAL_REACTIONS true
KINETICS 1
Ca_Ac
        -Formula  Ac  -2.0   Ca  1.0
        -steps 1 3 6 9 12 15 18 
	   -step_divide 1e-7
END