Surface complexation

[tsnmaster]

Hi to everyone, i'd like to know if this script is ok or i have to fix it and also i got confused with 2 concepts which i describe below.

PHASES
   Schwertmannite
      Fe8O8(OH)6(SO4)+ 22 H+ = 8 Fe+3 + SO4-2 + 14 H2O
      log_k 10

SURFACE_MASTER_SPECIES 1
    Al_           Al_OH

SURFACE_SPECIES 1
AsO4-3 + 3H+ + Al_OH = Al_H2AsO4 + H2O
   log_k     26.94
AsO4-3 + 2H+ + Al_OH = Al_HAsO4- + H2O
   log_k     21.79
AsO4-3 + Al_OH = Al_OHAsO4-3
   log_k     6.39
Al_OH = Al_OH
   log_k     0
Al_OH + H+ = Al_OH2+
   log_k     7.17
Al_OH = Al_O- + H+
   log_k     -11.18


SOLUTION_SPREAD
    -units    mg/l
   pH    pe    Alkalinity     Al       B     Br     Ca     Cl    Fe(3)    Fe(2)       K       Mg    Mn(3)    Mn(2)    N(5)     Na     Pb    S(6)     Zn     Si    Description    Temperature    As(5)
                   meq/l                                                                                                                                                                           
 2.24     9             0    156    19.7    3.3    233    920     46.9      2.1    87.7    159.2        9        1     0.1    333    0.6    2450    9.8    200         Azufre             10      2.1
  8.7     9             2    0.7     3.3    0.5    120    190     0.57      0.3    20.0     55.0      0.1        0     0.4    170      0     477    0.1     15              x             10     0.05
END

EQUILIBRIUM_PHASES 1
    Basaluminite 0 0
    CO2(g)    -3.6373 10
    Gibbsite  0 0
    O2(g)     -0.8833 10
    Schwertmannite 0 0
   
END

SURFACE 1
    Al_OH Basaluminite      equilibrium_phase 0.046  9108
    Hfo_sOH Schwertmannite  equilibrium_phase 0.04   154580
    Hfo_wOH Schwertmannite  equilibrium_phase 1.6
    -donnan 1e-08
END


#USE SOLUTION 1
#USE SOLUTION 2
MIX
1   0.30
2   0.70

USE equilibrium_phases 1
USE surface 1

END

My question is about how can i know how much arsenic was adsorbed into each phases. In the results, do i have to select molalities into each one (because it gives me the values of hfo_AsO3 and other anions) but these ones are of the solution or i have to quantify schwertmannite and basaluminite and it is all.
 I got confused with these phases and molalities because i'd like to know how much arsenic and sulfate were adsorbed into the phases.

Thank you a lot

[dlparkhurst]

Can't tell you if your script is OK.

Not sure if PHREEQC will work right if you name the surface Al_; it may get confused with Al. I suggest you use another prefix. like Alx without the underscore unless you need multiple sites.

The function you want is SURF, which is used below in USER_PRINT. There is also a function EDL for the diffuse layer and EDL_SPECIES to find individual species in the diffuse layer, which is documented in the release notes.

The example adds some NaOH to precipitate schwertmannite.


PHASES
Schwertmannite
    Fe8O8(OH)6(SO4) + 22H+ = 8Fe+3 + 14H2O + SO4-2
    log_k     10
SOLUTION 1
    temp      10
    pH        2.24
    pe        4
    redox     pe
    units     mg/l
    density   1
    Al        156
    As(5)     2.1
    Ca        233
    Cl        920
    Fe(2)     2.1
    Fe(3)     46.9
    K         87
    Mg        159.2
    Na        333
    S(6)      2450
    -water    1 # kg
END
EQUILIBRIUM_PHASES 1
    Basaluminite 0 0
    CO2(g)    -3.6373 10
    Gibbsite  0 0
    O2(g)     -0.8833 10
    Schwertmannite 0 0
END
SURFACE 1
    Hfo_sOH Schwertmannite  equilibrium_phase 0.04   154580
    Hfo_wOH Schwertmannite  equilibrium_phase 1.6
    -donnan 1e-08
END
USER_PRINT
-start
10 PRINT "As sorbed on Hfo: ", SURF("As", "Hfo")
20 PRINT "S  sorbed on Hfo: ", SURF("S", "Hfo")
-end
REACTION
NaOH
10 mmol
USE equilibrium_phases 1
USE solution 1
USE surface 1
END

[tsnmaster]

thank you a lot.
If i want to export these data to excel, what do i have to add?

[tsnmaster]

i tried with user_punch but i couldn't do it.

[dlparkhurst]

You need a SELECTED_OUTPUT n and USER_PUNCH n, n = 1 by default


SELECTED_OUTPUT 2
-file xyz
USER_PUNCH 2
-headings Hfo-As Hfo-S
10 PUNCH SURF("As", "Hfo")
20 PUNCH SURF("S", "Hfo")