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-equilibrate command for PHREEQC



I am trying to use the equilibrate command under SURFACE for PHREEQC.  I
have a water composition that I am assuming is in equilibrium with
ferrihydrite.  I'm trying to model the composition of the ferrihydrite and
compare to the actual composition from samples I digested.  When I use
the -equilibrate command, the initial surface composition is virtually empty
of sorbed species, possibly because there is no ferrihydrite.  But the
solution is supersaturated wrt ferrihydrite.  So I don't understand why the
initial surface does not have ferrihydrite.  If you could provide any
suggestions I would appreciate it very much.  The input and database files
are attached.

Kelly Greaser
Ph.D Candidate
Colorado School of Mines
Hydrogeology Program
Geology and Geological Engineering
TITLE 207 and 208 mix 6/27/02
SOLUTION_SPREAD
	-units ppm	# Al=0.021 Cu=0.001 P=0.095 Pb=0.012
Number	Desc	Al	Ba	Ca	Cd	Cu	Fe	K	Mg	Mn	Na	Ni	P	Pb	S(6)	Si	Zn	F	Cl	pH	Alkalinity	pe	Temp
18	207 6/27	0.260	0.031	15.039	0.005	0.005	4.962	0.405	10.246	0.740	1.828	0.045	0.004	0.001	83.267	2.960	3.555	0.000	0.379	6.21	4.1	1.85	7.6
19	208 6/27	0.008	0.063	20.635	0.001	0.001	0.002	0.138	8.315	0.000	0.990	0.001	0.004	0.001	11.586	1.246	0.000	0.000	0.416	7.93	81.9	2.38	8.2
MIX 1 207 and 208
	18	0.33
	19	0.67
PHASES
pH_Fix
	H+ = H+
	log_k	0.0
pe_Fix
	e- = e-
	log_k	0.0
Clayproxy
	K0.08Na0.02Ca0.56Mg0.39Al1.7Si0.475O4(OH) + 7.1H+ = 0.08K+ + 0.02Na+ + 0.56Ca+2 + 0.39Mg+2 + 1.7Al+3 + 0.475H4SiO4 + 3.1H2O
	log_k	-10
EQUILIBRIUM_PHASES 1
	pH_Fix	-7.17	Calcite	0.1
	pe_Fix	-3.35	O2(g) 0.1
SAVE solution 66
END
EQUILIBRIUM_PHASES 2
	pH_Fix	-7.17	Calcite	0.1
	pe_Fix	-3.35	O2(g) 0.1
	Ferrihydrite	0.0	0.0
	Clayproxy	0.0	0.0
	Otavite	-0.72	0.0
	Barite	0.11	0.0
#	Zn(OH)2(s)	0.0	0.0
#	Zn(OH)2(w)	0.0	0.0
#	Ca-Nontronite	10.0	0.0
#	Mg-Nontronite	0.0	0.0
#	Kaolinite	0.0	0.0
#	Ca-Montmorillonite	0.0	0.0
#	Schwertmannite	1.4	0.0
SURFACE_SPECIES
	Hfo_wOH + Zn+2 + SO4-2 = Hfo_wOHZnSO4
	log_k   6.67	#ternary surface complex formation
	Hfo_wOH + H+ + SO4-2 = Hfo_wSO4-  + H2O
	log_k	7.78		#7.78 -	no conf limits
	Hfo_wOH + SO4-2 = Hfo_wOHSO4-2
	log_k	0.79		#0.79 -	no conf limits
	Hfo_sOH  + Zn+2 = Hfo_sOZn+ + H+
	log_k   0.99	#0.99 +
	Hfo_wOH  + Zn+2 = Hfo_wOZn+ + H+
	log_k	-1.99		#-1.99 +
	Hfo_sOH  + Cd+2 = Hfo_sOCd+ + H+
	log_k   0.47	#0.47 +
	Hfo_wOH  + Cd+2 = Hfo_wOCd+ + H+
	log_k	-2.9		#-2.9 +
	Hfo_sOH  + Pb+2 = Hfo_sOPb+ + H+
	log_k   4.65	#4.65 -
	Hfo_wOH  + Pb+2 = Hfo_wOPb+ + H+
	log_k	0.30		#0.3 -		derived
	Hfo_wOH + PO4-3 + 3H+ = Hfo_wH2PO4 + H2O
	log_k	31.29		#31.29 
	Hfo_wOH + PO4-3 + 2H+ = Hfo_wHPO4-  + H2O
	log_k	25.39		#25.39 
	Hfo_wOH + PO4-3 + H+ = Hfo_wPO4-2 + H2O
	log_k	17.72		#17.72
	Hfo_sOH + Mn+2 = Hfo_sOMn+ + H+
	log_k  -0.40	#-0.4 +	derived
	Hfo_wOH + Mn+2 = Hfo_wOMn+ + H+
	log_k -3.50	#-3.5 +	derived
	Hfo_sOH + Ba+2 = Hfo_sOHBa+2
	log_k	5.46		#5.46 
	Hfo_wOH + Ba+2 = Hfo_wOBa+ + H+
	log_k	-7.2		#-7.2 	derived
	Hfo_wOH + Mg+2 = Hfo_wOMg+ + H+
	log_k -4.6		#-4.6 +	derived; no constant available for strong site!
	Hfo_sOH + Ca+2 = Hfo_sOHCa+2
	log_k	4.97		#4.97
	Hfo_wOH  + Ca+2 = Hfo_wOCa+ + H+
	log_k	-5.85		#-5.85
	Hfo_sOH  + Cu+2 = Hfo_sOCu+ + H+
	log_k	2.89		#2.89
	Hfo_wOH  + Cu+2 = Hfo_wOCu+ + H+
	log_k	0.6		#0.6		derived
	Hfo_sOH  + Ni+2 = Hfo_sONi+ + H+
	log_k   0.37	#0.37
	Hfo_wOH  + Ni+2 = Hfo_wONi+ + H+
	log_k	-2.5		#-2.5 	derived
USE solution 66
SURFACE 2
	-equilibrate with soltuion 66
	Hfo_sOH	Ferrihydrite	equilibrium_phase	0.005		5.33e4
	Hfo_wOH	Ferrihydrite	equilibrium_phase	0.2
SELECTED_OUTPUT
	-file	2078MixEQ.out
	-sim false
	-state false
	-soln false
	-distance false
	-time false
	-step false
	-ionic_strength	false
	-percent_error	false
	#-totals	Fe	S	Zn
	-molalities	Hfo_sOZn+	Hfo_sOPb+	Hfo_sOMn+	Hfo_sOCd+
	Hfo_sOHCa+2	Hfo_sOHBa+2	Hfo_sOCu+	Hfo_sONi+	Hfo_wOHSO4-2	
	Hfo_wSO4-	Hfo_wOHZnSO4	Hfo_wOZn+	Hfo_wOMg+	Hfo_wOMn+	
	Hfo_wOCa+	Hfo_wOPb+	Hfo_wOCd+	Hfo_wOBa+	Hfo_wOCu+	Hfo_wONi+
	Hfo_wPO4-2	Hfo_wHPO4-	Hfo_wH2PO4
	-equilibrium_phases	Ferrihydrite	Clayproxy	Barite	Otavite
	-pH
	-pe
END
#Clayproxy
#	K0.08Na0.04Ca0.56Mg0.38Al1.6Si0.55O4(OH) + 6.8H+ = 0.08K+ + 0.04Na+ + 0.56Ca+2 + 0.38Mg+2 + 1.6Al+3 + 0.55H4SiO4 + 2.8H2O
#	log_k	-10
#Clayproxy
#	K0.08Na0.04Ca0.56Mg0.38Al1.5Si0.625O4(OH) + 6.5H+ = 0.08K+ + 0.04Na+ + 0.56Ca+2 + 0.38Mg+2 + 1.5Al+3 + 0.625H4SiO4 + 2.5H2O
#	log_k	-10
#Clayproxy
#	K0.04Ca0.58Mg0.4Al1.9Si0.325O4(OH) + 7.7H+ = 0.04K+ + 0.58Ca+2 + 0.4Mg+2 + 1.9Al+3 + 0.325H4SiO4 + 3.7H2O
#	log_k	-10
#Clayproxy
#	Ca0.7Mg0.3Al2Si0.25O4(OH) + 8H+ = 0.7Ca+2 + 0.3Mg+2 + 2Al+3 + 0.250H4SiO4 + 4H2O
#	log_k	-10
#Clayproxy
#	Ca0.72Mg0.28Al2.05Si0.2125O4(OH) + 8.15H+ = 0.72Ca+2 + 0.28Mg+2 + 2.05Al+3 + 0.2125H4SiO4 + 4.15H2O
#	log_k	-10
#Clayproxy
#	Ca0.7Mg0.3Al2.1Si0.175O4(OH) + 8.3H+ = 0.7Ca+2 + 0.3Mg+2 + 2.1Al+3 + 0.175H4SiO4 + 4.3H2O
#	log_k	-10

Attachment: GMree.dat
Description: Binary data



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