Zinc and Manganese Leaching Doubt

[AnnaJulIQ]

Hello,
First I would like to thank this forum, I have been able to learn many things.

I am trying to simulate the same leaching conditions from the article "Recovery of zinc and manganese from spent zinc-carbon and alkaline battery mixtures via selective leaching and crystallization processes"
The leaching conditions are as follows:
*pH (1-5)
*Liquid / solid ratios (10 g / mL)
*Temperature (60 ° C)
*100 g of black mass with water according to the L / S ratio
*H2SO4 (50% w / w) (Note: I take this in phase equilibrium)
*Zn (% w / w): 21.93% (Note: take this as ZnO phase)
*Mn (% w / w): 26.20% (Note: take this as MnO2 phase)

The situation that appears to me is the following: when observing the results of the article for the same conditions, it says that at a pH of 2 only approximately 40% of Mn is dissolved and in the results of speciation in phreeplot all the Mn is dissolved . How could I do this more exactly?

This is my code

Code: [Select]


SPECIATION
  DATABASE                             "Minteq.dat"
  jobTitle                             "Speciation vs pH using 'species' plot type"
  calculationType                      species
  calculationMethod                    1
  mainSpecies                          Mn Zn
  xmin                                 -5.0               # logH range
  xmax                                 -0.0
  resolution                           100

PLOT
  plotTitle                            "Recovery of zinc and manganese"
  customXcolumn                        2                   # x-axis value is the second column - the first column is 'pH' (see out file)
  pxmax                                4                  # default is 14
  pxmin                                0
  pymin                                0
  pymax                                100
  minimumYValueForPlotting             5.0                 # eliminates minor species

  png true
  pdf true

CHEMISTRY

include 'speciesvsph.inc'                                  # contains the logic for outputting the expected x-axis, y-axis (%distr) pairs expected by 'species' plot type

TITLE #Recovery of zinc and manganese from spent zinc-carbon and alkaline battery mixtures via selective leaching and crystallization processes
PHASES
Fix_H+
   H+ = H+
   log_k 0.0
Na2SO4
Na2SO4 = 2Na+ + SO4-2
log_k 0.0

SOLUTION 1
-temp 60  #ºC
-WATER 1  # 1 Kg of water/// S/L = 1/10 (g/mL) - 1000 mL
END

USE solution 1
EQUILIBRIUM_PHASES
     Fix_H+  <x_axis>  H2SO4 10.204 # Mol H2SO4
     -force_equality true
     Na2SO4  -15 10
# 100 g of black mass
Pyrolusite 0  0.3011  #mol de MnO2
Zincite    0  0.2707  #mol de ZnO
END


[dlparkhurst]

I'm not clear on how they adjusted pH and whether that affected the solid-liquid ratio. At a solid-liquid ratio of 0.1 g/mL, the pH should be negative, even if all of the solid dissolves; so, it how do you get a pH of 2?

Here is a simulation that incrementally adds solid to 1 kg of acid solution to an ultimate solid liquid ratio of 10 kg/L (10 g/mL).

A previous post that I deleted forgot to take into account the assumed loss of oxygen to the atmosphere.

Code: [Select]

PHASES
Zincite
ZnO + 2H+ = Zn+2 + H2O
log_k 11.334
delta_h -89.62 kJ
Pyrolusite
MnO2 + 4H+ + 2e- = Mn+2 + 2H2O
log_k 41.38
delta_h -272 kJ
END
USER_PRINT
10 PRINT "mol H2O in 0.5 kg:   ", 0.5 * 1000 / GFW("H2O"), " moles"
20 PRINT "mol H2SO4 in 0.5 kg: ", 0.5 * 1000 / GFW("H2SO4"), " moles"
30 PRINT "Zn moles in 10 kg:   ", 10000*.22/GFW("Zn")
40 PRINT "Mn moles in 10 kg:   ", 10000*.26/GFW("Mn")
SOLUTION 1
-temp 60  #ºC
-WATER 0.5 # 0.5 kg
END
USER_PRINT
USE solution 1
REACTION
H2SO4 1
5.0979e+00 mole # 0.5 kg H2SO4
SAVE solution 1 # 50% H2SO4 w / w
END
USE solution 1
REACTION 1
Pyrolusite 47.3      #mol de MnO2  2.2 kg
Zincite    33.7      #mol de ZnO   2.6 kg
1 in 1000
EQUILIBRIUM_PHASES
O2(g) -0.7
Pyrolusite 0 0
Zincite 0 0
USER_GRAPH 1
    -headings               ratio Zincite Pyrolusite pH
    -axis_titles            "Solid/Liquid ratio, g/mL" "% Dissolved" "pH"
    -axis_scale x_axis      0.1 10 auto auto log
  -start
10 GRAPH_X SYS("Zn")/33.7 * 10
20 GRAPH_Y (RXN*33.7 - EQUI("Zincite"))/(RXN*33.7)*100
30 GRAPH_Y (RXN*47.3 - EQUI("Pyrolusite"))/(RXN*47.3)*100
40 GRAPH_SY -LA("H+")
  -end
END


[AnnaJulIQ]

I am a bit confused in the development of this in phreeplot, because in this phase equilibrium H2SO4 is already added to carry out the pH variation

in phreeplot would it be that way?

Code: [Select]


SPECIATION
  DATABASE                             "Minteq.dat"
  jobTitle                             "Speciation vs pH using 'species' plot type"
  calculationType                      species
  calculationMethod                    1
  mainSpecies                          Mn Zn
  xmin                                 -14.0               # logH range
  xmax                                 0.0
  resolution                           100

PLOT
  plotTitle                            "Recovery of zinc and manganese"
  customXcolumn                        2                   # x-axis value is the second column - the first column is 'pH' (see out file)
  pxmax                                14                  # default is 14
  pxmin                                0
  pymin                                0
  pymax                                100
  minimumYValueForPlotting             5.0                 # eliminates minor species

  png true
  pdf true

CHEMISTRY

include 'speciesvsph.inc'                                  # contains the logic for outputting the expected x-axis, y-axis (%distr) pairs expected by 'species' plot type

TITLE #Recovery of zinc and manganese from spent zinc-carbon and alkaline battery mixtures via selective leaching and crystallization processes
PHASES
Fix_H+
   H+ = H+
   log_k 0.0
Na2SO4
Na2SO4 = 2Na+ + SO4-2
log_k 0.0

SOLUTION 1
-temp 60  #ºC
-WATER 0.5  # 1 Kg of water/// S/L = 1/10 (g/mL) - 1000 mL
END

USE solution 1
EQUILIBRIUM_PHASES
     Fix_H+  <x_axis>  H2SO4 5.0979e+00 # Mol H2SO4
     -force_equality true
     Na2SO4  -15 10
# 100 g of black mass
Pyrolusite 0   0.4763  #mol de MnO2
Zincite    0   0.3373  #mol de ZnO

END




[dlparkhurst]

(I may have mislead you, in that PhreePlot usually starts with the most acid condition, and then adds only base to achieve the desired pH range. The method I gave allows for any pH in the initial solution and adding acid or base as necessary.)

You are wearing me down. The PhreePlot calculation adds or removes H2SO4 and NaOH to achieve a specified pH. The last simulation I sent uses the Zn/Mn mixture to adjust the pH  (which makes more sense to me) up to a maximum of about pH 5, but I do not have the paper to see what they actually did.

Are you sure about your ratio of solid to liquid of 0.1 g/mL? The last simulation shows that a ratio of about 2 g/mL results in dissolution of all ZnO and only a fraction of MnO2.

I don't know what you are trying to do with PhreePlot; I'm not that familiar with all the options. I think the last simulation I posted is pretty close to what you want. Here is the same simulation adjusted a little to maximize the solid/liquid ratio at 1.9 g/mL and plotted with pH on the X axis. A ratio of about 0.7 to 1.5 g/mL generates pH between 1 and 5 where most Zn dissolves with limited Mn dissolution. Reality of course depends on the kinetics of reactions, and more detailed understanding of the solids.

Code: [Select]

PHASES
Zincite
ZnO + 2H+ = Zn+2 + H2O
log_k 11.334
delta_h -89.62 kJ
Pyrolusite
MnO2 + 4H+ + 2e- = Mn+2 + 2H2O
log_k 41.38
delta_h -272 kJ
END
USER_PRINT
10 PRINT "mol H2O in 0.5 kg:   ", 0.5 * 1000 / GFW("H2O"), " moles"
20 PRINT "mol H2SO4 in 0.5 kg: ", 0.5 * 1000 / GFW("H2SO4"), " moles"
30 PRINT "Zn moles in 10 kg:   ", 10000*.22/GFW("Zn")
40 PRINT "Mn moles in 10 kg:   ", 10000*.26/GFW("Mn")
SOLUTION 1
-temp 60  #ºC
-WATER 0.5 # 0.5 kg
END
USER_PRINT
USE solution 1
REACTION
H2SO4 1
5.0979e+00 mole # 0.5 kg H2SO4
SAVE solution 1 # 50% H2SO4 w / w
END
USE solution 1
REACTION 1
Pyrolusite 47.3      #mol de MnO2  2.2 kg
Zincite    33.7      #mol de ZnO   2.6 kg
.19 in 1000
EQUILIBRIUM_PHASES
O2(g) -0.7
Pyrolusite 0 0
Zincite 0 0
USER_GRAPH 1
    -headings               ratio Zincite Pyrolusite S/L_ratio
    -axis_titles            "pH" "% Dissolved" "Solid/Liquid ratio, g/mL"
    -axis_scale sy_axis      0.1 10 auto auto log
  -start
10 GRAPH_X -LA("H+") #SYS("Zn")/33.7 * 10
20 GRAPH_Y (RXN*33.7 - EQUI("Zincite"))/(RXN*33.7)*100
30 GRAPH_Y (RXN*47.3 - EQUI("Pyrolusite"))/(RXN*47.3)*100
40 GRAPH_SY SYS("Zn")/33.7 * 10
  -end
END


[AnnaJulIQ]

Here is the article, I also attach it as PDF

Recovery of zinc and manganese from spent zinc-carbon and alkaline battery mixtures via selective leaching and crystallization processes
Bayram Andaka, Erhan Özduğana,Selçuk Türdüb, A. Nusret Bulutcuc

https://doi.org/10.1016/j.jece.2019.103372

[dlparkhurst]

What is it that you want to model? Try to formulate a PHREEQC script that does what you want.