Add lithium dissociating and hydrolyzing species to code

[Topskeer]

Hi all,

I have the following water matrix:

SOLUTION 1
    pH 7.5                      # pH of the solution
    temp 25                     # Temperature in Celsius
    units mg/L                  # Concentration units in mg/L

    Co     1.88                 # Cobalt (mg/L)
    Cu     19.9                 # Copper (mg/L)
    Ni     108.0                # Nickel (mg/L)
    Pb     0.0007               # Lead (mg/L)
    Zn     1.94              # Zinc (mg/L)
    Li     333              # Lithium (mg/L)
    Na     45               # Sodium (mg/L)
    K      2.19                # Potassium (mg/L)
    Mg     2.04                # Magnesium (mg/L)
    Ca     4.66               # Calcium (mg/L)
    Si     2.66                # Silicon (mg/L)
    B      1.07                # Boron (mg/L)
    P      492            # Phosphorus (mg/L)
    Mn     4010                # Manganese (mg/L)
    Fe(3)  0.209                # Ferric iron (mg/L)
    F      40.43               # Fluoride (mg/L)
    Cl     33.49               # Chloride (mg/L)
    S(6)   167.54             # Sulfate (mg/L)
    P      6.19                # Phosphate (mg/L)
END

The Lithium is initially present as LiPF6, however it dissolves into Li+ and PF6- ions. The PF6- can react with H2O as well to form LiF + HF + HPO42-.
It my also further hydrolyze into HF via the following reaction: LiPF6 + 6 H2O = Li+ + PO4^3- + 6 HF. Is there anyone who knows how to add these reactions to my input file? I'm using the Minteq database.

Thanks.

[dlparkhurst]

If you assume equilibrium, you need a log K for the following aqueous association reaction, which you would define in the SOLUTION_SPECIES data block.

Code: [Select]

SOLUTION_SPECIES
PO4-3 + 6F- + 4H2O = PF6- + 8OH-

Note that you should define P only once in the SOLUTION definition, probably the following if PF6- is a large proportion of the phosphorus. I suspect that PF6- and PO4 do not coexist at aqueous equilibrium, in which case, you need a different reaction network that treats PF6- as a separate "element".

Code: [Select]

P 492 mg/L as P