SCM with CD-MUSIC in carbonate suface

[Nlesani75]

hi guys
I m new in CD-MUSIC .when i run my code i have constant surface charge or psi in 3 planes then i have constant surface charge in my diagrams(-85 mV).can you help me on this?thanks
my code:
DATABASE C:\Program Files (x86)\USGS\Phreeqc Interactive 3.6.2-15100\database\phreeqc.dat
TITLE projectFW

SURFACE_MASTER_SPECIES
    Limsurf_a     Limsurf_aOH 
    Limsurf_c     Limsurf_cH   
SURFACE_SPECIES
Limsurf_aOH = Limsurf_aOH
    log_k     0
Limsurf_aOH = Limsurf_aO- + H+
    log_k     -12
Limsurf_aOH + CO3-2 + H+ = Limsurf_aHCO3 + OH-
    log_k     8.15
   Limsurf_aOH + CO3-2 = Limsurf_aCO3- + OH-
    log_k     1.55
Limsurf_aOH + SO4-2 = Limsurf_aSO4- + OH-
    log_k     -0.1
   Limsurf_cH = Limsurf_cH
    log_k     0
   Limsurf_cH = Limsurf_c- + H+
    log_k     -5.1
   Limsurf_cH + Ca+2 = Limsurf_cCa+ + H+
    log_k     -1.7
   Limsurf_cH + Mg+2 = Limsurf_cMg+ + H+
    log_k     -2


SURFACE 1
    -equilibrate with solution 1
    -sites_units density   
   Limsurf_a    2.5       0.11      0.2
   Limsurf_c    2.5
   -capacitance 0.97     0.97
     
   -cd_music
    -donnan 1e-9
    only_counter_ions false
    KNOBS; -iter 2000


SOLUTION 1 FW
    temp      25
    pH        6.7
    redox     pe
    units     ppm
    density   1
    Alkalinity 1400 as HCO3-
    Ca        14547 as Ca+
    Cl        112943
    K         0
    Mg        739
    Na        5658
    S(6)      1728 as SO4-2
    -water    1 # kg
   
EQUILIBRIUM_PHASES 1
    Calcite   0 1e-3
SAVE solution  1
PHASES
    Fix_H+
    H+ = H+
    -log_k  0

SELECTED_OUTPUT
    -file                 fw3V1.sel
    -reset                 false

USER_PUNCH 
    -start
 10 FOR i = 6.5 to 8 STEP 0.5
 20 a$ = EOL$ + "USE solution 1" + CHR$(59) + " USE surface 1" + EOL$
 30  a$ = a$ + "EQUILIBRIUM_PHASES 2" + EOL$
 40 a$ = a$ + " Fix_H+ " + STR$(-i) + " HCl 0.1" + EOL$
 50 a$ = a$ + "END" + EOL$
 60 PUNCH a$
 70 NEXT i
 80 FOR i = 8 to 11 STEP 0.5
 90 a$ = EOL$ + "USE solution 1" + CHR$(59) + " USE surface 1" + EOL$
100 a$ = a$ + "EQUILIBRIUM_PHASES 2" + EOL$
110 a$ = a$ + " Fix_H+ " + STR$(-i) + " NaOH 0.1" + EOL$
120 a$ = a$ + "END" + EOL$
130 PUNCH a$
140 NEXT i
END
SELECTED_OUTPUT
    -file                 fw3V1-zp.sel
    -reset                true
    -molalities           Limsurf_cCa+  Limsurf_cMg+ Limsurf_c-  Limsurf_cH  Limsurf_aOH  Limsurf_aHCO3  Limsurf_aCO3-  Limsurf_aSO4-
USER_PUNCH 
    -start
10 PUNCH EDL("psi","Limsurf")
    -end
USER_GRAPH 1 fw-sp
    -headings               pH Limsurf_cCa+ Limsurf_cMg+ Limsurf_c- Limsurf_cH Limsurf_aOH Limsurf_aHCO3 Limsurf_aCO3-  Limsurf_aSO4-
    -axis_titles            pH  "moles per kg water"
    -chart_title            "surface species in FW"
    -axis_scale x_axis      5 12 1 1
    -axis_scale y_axis      1e-17 1e-6 1 1 log
  -start
10 GRAPH_X -LA("H+")
20 GRAPH_Y MOL("Limsurf_cCa+"), MOL("Limsurf_cMg+"), MOL("Limsurf_c-"), MOL("Limsurf_cH"), MOL("Limsurf_aOH"), MOL("Limsurf_aHCO3"), MOL("Limsurf_aCO3-"), , MOL("Limsurf_aSO4-")
  -end
   
USER_GRAPH 2 fw-zp
    -headings               pH zp
    -axis_titles            pH "zeta potential mV"
    -chart_title            "zp distribution in FW"
    -axis_scale x_axis      5 12 1 1
    -axis_scale y_axis      -85 30 5 5

  -start
10 GRAPH_X -LA("H+")
20 GRAPH_Y EDL("psi","Limsurf")*1e3
  -end
     
INCLUDE$ fw3V1.sel
END



 

[dlparkhurst]

To use CD_MUSIC, you need to specify that each SURFACE_SPECIES definition is for CD_MUSIC and give the location of charge among the different planes. Here is an excerpt from the attached example file:

Code: [Select]

SURFACE_SPECIES
Goe_triOH0.5 = Goe_triOH0.5; -log_k 0
            -cd_music  0.5 0 0 0 0


[Nlesani75]

thanks
i have question on that.how these deltas calculate?its from charges of  surface groups in diffrent positions?
can you explain more for me

[dlparkhurst]

Yes, the CD-MUSIC model allows the charge of a sorbed species to be distributed among multiple planes. You need to read the works of Hiemstra and coworkers for details. Here is a start into that literature:

Hiemstra, T., and Van Riemsdijk, W.H., 1996, A surface structural approach to ion adsorption--The charge distribution (CD) model: Journal of Colloid Interface Science, v. 179, no. 2, p. 488-508.