2Goe?

[tizzi27]

Dear Phreeqc users,

I'm trying to insert the following reaction as SURFACE_SPECIES (http://www.hzdr.de/db/res3t.detailsComplex?complexID=3127):

2 »Fe-OH + VO4<3-> + 4 H<1+>  ⇔  (»Fe-O)2-V(OH)2<1+> + 2 H2O

However, inserting the goethite as follow, 2Goe_OH, the code responds "Error: coefficient of first species on rhs is not equal to 1.0"

So I tried to divide by 2 mol: Goe_OH + .5VO4-3 + 2H+  =  Goe_OV(OH)2+ + H2O
but it is unbalanced.

So what's the right way to write this equation?

Many thanks

[dlparkhurst]

I think this matches your description.

Code: [Select]

SURFACE_MASTER_SPECIES
    Goe           GoeOH       
SURFACE_SPECIES
GoeOH = GoeOH
    log_k     0
2GoeOH + 4H+ + VO4-3 = (GoeO)2V(OH)2+ + 2H2O
    log_k     44.38
END
SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mmol/kgw
    density   1
    V(5)      1
    -water    1 # kg
END
EQUILIBRIUM_PHASES
Goethite 0 1
SURFACE 1
    GoeOH   Goethite        equilibrium_phase 0.01   600
-eq 1
END