PhreeqcUsers Discussion Forum

Processes => Oxidation and reduction equilibria => Topic started by: yasmina on May 05, 2021, 02:31:24 PM

Title: Manganese sorption
Post by: yasmina on May 05, 2021, 02:31:24 PM
Dear FREEQC-users,

I have just recently started using Phreeqc for my Master's thesis. I am facing some problems in writing my script, I tried to use the database as much as possible, but I don't know what I am doing wrong. I hope you could help me please.

So my problem is as follow:
I want to model the adsorption of manganese using Freundlich isotherm. In my experiment, I used a 0.01 M of NaHCO3 (40 ml as a background solution) to which I added 1g of soil, then I added different volumes of a 0.005 M Mn(NO3)2*2H2O solution. In the end, I got many samples that had the same amount of soil and background solution but different initial volume of Mn(NO3)2.

When I try to make this into a phreeqc script, nothing works. You will find the script here below. I really hope that you could spare some of your time to discuss my problem.
Thank you for any help you can provide.

SURFACE_MASTER_SPECIES
      Freundlich Freundlich

SURFACE_SPECIES
   Freundlich = Freundlich
   Freundlich + 0.722 Mn+2 = FreundlichMn+2
        -log_k -6.67    #log(k)=log(300)+(0,722-1)*log(54,9e6)-log(10100)
        -no_check
        -mole_balance FreundlichMn+2

SURFACE  1
        Freundlich   1e100 1 1
SOLUTION 1
        pH           8   charge
        units        mol/l
        Na           0.01
        C(+4)        0.01
        water        1

Reaction 1
        MnNO3        0.1
        0.1 in 20
User_Graph
-headings Freundlich
      -chart_title "Sorption Isotherm"
      -axis_titles "Dissolved Cd" \
                    "Sorbed Cd"
     
  -start
10 x = act("Mn+2") * 54.9e6
20 PLOT_XY x, mol("FreundlichMn+2")*54.9e6, color = Blue
  -end
PRINT
     -reset false
END
Title: Re: Manganese sorption
Post by: dlparkhurst on May 05, 2021, 10:51:55 PM
Code: [Select]
SURFACE_MASTER_SPECIES
      Freundlich Freundlich

SURFACE_SPECIES
   Freundlich = Freundlich
   Freundlich + 0.722 Mn+2 = FreundlichMn+2
        -log_k -99.6475    #log(k)=log(300)+(0,722-1)*log(54,9e6)-100
        -no_check
        -mole_balance FreundlichMn(NO3)2
SURFACE  1
        Freundlich   1e100 1 1
SOLUTION 1
        pH           8   charge
        units        mol/l
        Na           0.02
        C(+4)        0.01
  N(5)         0.01
        water        1
Reaction 1
        MnNO3        1
        0.001 in 20
User_Graph
-headings Freundlich
      -chart_title "Sorption Isotherm"
      -axis_titles "Dissolved Mn, ug/kgw" \
                    "Sorbed Mn, ug/kgw"
  -start
10 x = TOT("Mn")*GFW("Mn")*1e6
20 PLOT_XY x, MOL("FreundlichMn+2")*GFW("Mn")*1e6, color = Blue
  -end
END