my sample has Cu, Cd, Zn, NaOH, and H2SO4. I expected to see cu precipitation at this pH.
The precipitation of Cu at pH 7 might depend on various factors like the initial concentrations of Cu, Cd, Zn, as well as the ionic strength of the solution. Check the equilibrium constants and solubility products used in your PHREEQC model, and ensure they are accurate for Cu precipitation at pH 7 under your specific conditions. Adjusting these parameters or considering additional chemical reactions may help simulate the expected Cu precipitation.
If you fix pH at 7, at least Cu(OH)2 precipitates.
DATABASE c:\phreeqc\database\minteq.v4.dat
PHASES
Fix_pH
H+ = H+
log_k 0
SOLUTION 1
pH 7
Cu 1
Cl 2
EQUILIBRIUM_PHASES
Fix_pH -7 HCl
Cu(OH)2 0 0
END
My fault. The right input file is as follows. Cu(OH)2 precipitates
DATABASE c:\phreeqc\database\minteq.v4.dat
PHASES
Fix_pH
H+ = H+
log_k 0
SOLUTION 1
pH 7 charge
Cu 1
Cl 2
END
USE SOLUTION 1
EQUILIBRIUM_PHASES
Fix_pH -7 NaOH
Cu(OH)2 0 0
END
The same:
DATABASE c:\phreeqc\database\minteq.v4.dat
PHASES
Fix_pH
H+ = H+
log_k 0
SOLUTION 1
pH 7 charge # Result: 3.883
Cu 1
Cl 2
END
USE SOLUTION 1
EQUILIBRIUM_PHASES
#Fix_pH -7 NaOH
Fix_pH -7 HCl
Cu(OH)2 0 0
END
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