PhreeqcUsers Discussion Forum

Processes => Surface Complexation => Topic started by: DeanWalmsley on May 19, 2021, 11:37:01 AM

Title: Hfo_CB error when using Hfo (ferrihydrite)
Post by: DeanWalmsley on May 19, 2021, 11:37:01 AM
Hi,
I was wondering if anyone had this error when modelling surface sorption to ferrihydrite,
ERROR: No potential unknown found for surface species Hfo_CB.
I am modelling surface sorption of phosphate at different pHs starting at pH 0.1 and going to pH 11, this is my initial solution, surface parameters and a few lines of the code to simulate the process:

SURFACE_SPECIES
#   Phosphate
      Hfo_wOH + PO4-3 + 3H+ = Hfo_wH2PO4 + H2O
      log_k   31.29

      Hfo_wOH + PO4-3 + 2H+ = Hfo_wHPO4- + H2O
      log_k   25.39

      Hfo_wOH + PO4-3 + H+ = Hfo_wPO4-2 + H2O
      log_k   17.72

SURFACE 1
    Hfo_sOH Ferrihydrite(am) equilibrium_phases 0.005    600
    Hfo_wOH Ferrihydrite(am) equilibrium_phases 0.2

solution 1
-units mg/kgW
pH 0.1
pe 12
Fe(3) 100
P  10     
N(5) 1 mol/kgw charge
SAVE solution 1

END

USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -0.25 NaOH; USE SURFACE 1;  END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -0.50 NaOH; USE SURFACE 1;   END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -0.75 NaOH; USE SURFACE 1;  END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -1.00 NaOH; USE SURFACE 1;  END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -1.25 NaOH; USE SURFACE 1; END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -1.50 NaOH; USE SURFACE 1;  END
USE SOLUTION 1; Equilibrium_phases 1; Ferrihydrite(am) 0.0 0.0; Fix_pH -1.75 NaOH; USE SURFACE 1;  END

I am using a modified version of the thermochimie database which includes surface reactions from Dzombak and Morel (1990). There is no reference to Hfo_CB in either my input file or in the database I am using so Iím at a loss as to where this error is coming from and how to eliminate it. Any advice would be hugely appreciated,
Thanks
Dean
Title: Re: Hfo_CB error when using Hfo (ferrihydrite)
Post by: dlparkhurst on May 19, 2021, 02:43:03 PM
I think it is that surface complexation electrical double layer model is not implemented for a SIT database.
Title: Re: Hfo_CB error when using Hfo (ferrihydrite)
Post by: dlparkhurst on May 19, 2021, 03:55:39 PM
See a discussion at https://phreeqcusers.org/index.php/topic,1765.msg5997.html#msg5997