Creating a surface

[Charlie]

FROM Aoha:

Dear Charlie

Please help me concerning the construction of surface complexation model in PHREEQC. The examples are given in PHREEQC manual (e.g. 8 & 14) do not match with my problem. In those examples, surface species (Hfo_w and Hfo_s) are linked to hydrous ferric oxide master species.
I want to use calcite surface for Mg2+, SO42-, and Ca2+ etc. adsorption. I could not create such a surface although I followed above-mentioned examples. I tried different databases but unable to create such surface.
Please help me, if possible then share a simple data input file for self-learning.
Best Regards

Aoha

[Charlie]

Hi Charlie
Here is the example file that I tried to construct.
TITLE SCM for self-learning

SURFACE_MASTER_SPECIES
Ca_o   Ca_oH           # want to define >Ca+ is the binding site on calcite surface
C_o    C_oH            # want to define >CO3- is the binding site on calcite surface

SURFACE_SPECIES        # adding only two reactions for simplicity
Ca_OH + H+ = Ca_OH2+   # Original reaction is >CaOH + H+  <> >CaOH2+               
log_k  11.85

C_oH = C_o- + H+       # Original reaction is >CO3H <> >CO3- + H+   
log_k  -5.1

SURFACE 1 Explicit diffuse layer        # Explicit way to define the surfaces
   -equilibrate with solution 2
    -sites_units   density           #(density indicates the site density is given & the number of sites is calculated from the site density & the surface area)
    Ca_OH      5.0     2.0    1.0     
    Co_3H      5.0     2.0    1.0
    -diffuse_layer      2e-             #(Thickness of diffuse layer 2*10^-8 m)
END

SOLUTION 2
      -units    mmol/kgw
        pH      6.46
      pe       12 
        temp    70
      density 1.1486
      Ca      0.205
      Mg      0.075
      S(6)    0.010
      Na      3.124
      Cl      3.782                    # charge
      C(4)    0.001
      K       0.097

SELECTED_OUTPUT
-file Ca_CO3.csv
-pH
-ionic_strength
-activities Ca+2 CO3-2 CaHCO3+  HCO3-  CaOH+
#-molalities C_oCO3-1 0.33 C_oCa+1 0.33

END

[Charlie]

Aoha

It looks like there is are inconsistencies between your surface master species

SURFACE_MASTER_SPECIES
Ca_o   Ca_oH           # want to define >Ca+ is the binding site on calcite surface
C_o    C_oH            # want to define >CO3- is the binding site on calcite surface

and the surface site description:

 Ca_OH      5.0     2.0    1.0     
 Co_3H      5.0     2.0    1.0

These need to match and also be capitals for oxygen. 

Hope that is a helpful start!

[Tamirian]

I have a similar question. I tried to add surface complexations for the kaolinite surface. I followed the SURFACE_MASTER_SPECIES and SURFACE_SPECIES definitions for Hfo in phreeqc.dat as recommended in another post but It did not work. I am very new to phreeqc, would you please help me in this matter. I have two binding sites on the kaolinite surface (>Al-O and >Si-O) My input data is as follows:


SURFACE_MASTER_SPECIES
    Kaolin_al       Kaolin_alOH         
    Kaolin_si       Kaolin_siOH         

SURFACE_SPECIES
H+ + Kaolin_alOH = Kaolin_alOH2+
    log_k     -3
    delta_h   0 kJ
Kaolin_alOH = Kaolin_alO- + H+
    log_k     -3.8
    delta_h   32 kJ
Kaolin_siOH =Kaolin_siO- + H+
    log_k     -7
    delta_h   32 kJ

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mol/l
    density   1
    Na        0.5
    Cl        0.5
    -water    1 # kg

SURFACE 1
    -sites DENSITY
    Kaolin_siOH     1.15      10        20
    Kaolin_alOH     1.15
I have tried Surf and X and many thing instead of kaolin but it doesn't work. What am I doing wrong here?

[ramaiyer]

Let me try this way instead of the notify route maybe!

I am truly a fledgling at this and am trying to learn from reading through all this.

What I am trying to learn and do is the following:

Using the nanocrystal form of calcium silicate hydrates, which is supposed to have the general structure
          CaxSixO2.83x(OH)0.33x
to remove  phosphorous in phosphate mine water streams.

This appears similar to what you are trying so can I use the example and substitute calcium silicate hydrate formula for starters and see what I get?

[dlparkhurst]

This may be a relevant post http://phreeqcusers.org/index.php/topic,842.msg2486.html#msg2486

[MichaelZ20]

Aoha:
See  www.nrc.gov/docs/ML0815/ML081510035.pdf

[Oubai]

HI,
I have high saline water with specified species in equilibrium with two surfaces which are :
surface1: kaolinite_ AL-O-H
              kaolinite_Si-O-H

Surface 2: Oil_NH+
                Oil-COOH
So I would like to investigate the effect of adding a water with different salinity on the ionic strength and the concentration for the final species.