Fluoride Removal in Wastewatar via Precipitation Using PhreeQC at Diff pH & temp

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i_azharkhan:
Hi all,

I am a Master student new to PhreeQC, and I am currently working on a project to model the removal of fluoride from wastewater through precipitation under varying conditions of pH and temperature. I have elemental concentration data for the wastewater, but I am unsure how to set up the PhreeQC model to simulate the removal of fluoride and the associated chemical reactions.

Project Overview:
Goal: To predict the removal of fluoride from wastewater via precipitation at different pH levels and temperatures.
Data: I have elemental concentration data for the wastewater, but I am not sure what specific chemicals, species, or reactions I should include in the PhreeQC model for precipitation processes.
Parameters: I am interested in understanding how fluoride removal is affected by pH, temperature, and the potential for precipitation reactions.

My Request:
PhreeQC Input File Help: I am looking for guidance on how to write a PhreeQC input file for simulating fluoride removal via precipitation. I need help identifying the appropriate chemical species and reactions that should be included in the input code.
Precipitation Mechanism: I would appreciate any suggestions on the chemical processes that could be involved in fluoride removal via precipitation. For example, should I focus on precipitation reactions with calcium, aluminum, or other available elements in the wastewater?
Temperature and pH Effects: How can I model the effects of temperature and pH on the fluoride precipitation process in PhreeQC?
Graphing Results: Is it possible to plot the fluoride removal results in a graph (e.g., fluoride concentration vs. pH or temperature)? If so, how can I set this up in PhreeQC and visualize the data?
General Advice: Any other tips or insights on how to properly set up the model and interpret the results would be very helpful.

Data:
Here is the elemental concentration data for the wastewater (I will add the specific values once I receive guidance on the format):

Fluoride (F-) concentration: [0.39 mg/L]
Other relevant elements: [SiO2 = 8.28 mg/L, Ammonia nitrogen = 0.22mg/L, F- = 0.39mg/L, Cl- = 1.21mg/L, Cr = <0.004 mg/L, CN- = <0.001mg/L, NO2- = <0.08mg/L, NO3- = 18.5mg/L, CO32- = 0mg/L, Mg2+ = 2.12mg/L, Ca2+ = 15.4mg/L, Na+ = 2.32mg/L, K+ = 0.96mg/L, HCO3- = 27.2 mg/L, Volatile phenol = <0.001, Sulfide (measured as H2S) = <0.02mg/L, suspended solids = 3.40mg/L, SO42- = 14.1mg/L, Total phosphorus = <0.01mg/L, Total nitrogen = 4.37mg/L, Cr = 0.001066mg/L, Ni = 0.001066mg/L, Cu = 0.0008604mg/L, Zn = 0.002393mg/L, As = 0.018424mg/L, Mo = <0.0002mg/L, Cd = 0.010439mg/L, Pb = <0.0002mg/L, TFe = 0.0009mg/L, Mn = <0.01mg/L, Al = 0.1465mg/L, As = 0mg/L, Hg = 0mg/L]
pH range: [e.g., pH 2-12]
Temperature range: [e.g., 15?C - 60?C]

PhreeQC Questions:
What chemicals or minerals should I include to model fluoride removal via precipitation?
Are there specific reactions I should focus on, such as fluoride precipitation with calcium (CaF₂), aluminum (AlF₃), or other potential precipitates?
How do I account for the changes in fluoride concentration due to pH and temperature variations during precipitation?
Is it possible to plot the results of fluoride removal in PhreeQC (e.g., fluoride concentration vs. pH or temperature) for better visualization?

dlparkhurst:
If you will write a SOLUTION definition in PHREEQC, I will try to answer one or two of your other questions. You can use PhreeqcI (https://github.com/usgs-coupled/phreeqci), Notepad++ (from hydrochemistry.eu), or an editor. All you need to do is define the solution composition in the proper units. You can probably skip the minor elements like Mo.

i_azharkhan:
The SOLUTION definition is
SOLUTION 1
temp 25
pH 7.54
pe 4
redox pe
units mg/l
density 1
F 0.39
Cl 1.21
N(3) 0.08
N(5) 18.5
C(4) 0
Mg 2.12
Ca 15.4
Na 2.32
K 0.96
S(6) 14.1
Cu 0.00239
Zn 0.01842
Cd 0.0002
Pb 0.0009
Fe 0.0523
Mn 0.01
Al 0.1465
-water 1 # kg
Besides that, I want to find the removal percentage of fluoride at different pH and temperatures. So for that, I will change the values of pH, temperature, as well as the concentration of elements. Thank you sir.

dlparkhurst:
Here is an example that determines the amount of CaCl2 that must be added to water to precipitate fluorite at a pH of 9 and a temperature of 30 C. It is not practical because it requires nearly 1 mol/kgw to begin precipitation. You can experiment with other reactants and other conditions.

I think you will have difficulty working with the Al - F system. I don't think the aqueous model is reliable. Basically, the Al-F ion pair and other complexes are so that the saturation index of AlF3 decreases as Al concentration increases. I have never worked in this system, but have noted the effect occasionally.

--- Code: ---PHASES
AlF3
AlF3 = Al+3 + 3 F-
log_k -17.2089
-delta_H -34.0441 kJ/mol # Calculated enthalpy of reaction AlF3
# Enthalpy of formation: -1510.4 kJ/mol
-analytic -3.9865e+2 -1.3388e-1 1.0211e+4 1.5642e+2 1.5945e+2
# -Range: 0-300

Fix_H+
H+ = H+
log_k 0
END
KNOBS
-step 10
-pe 2
SOLUTION 1
temp 25
pH 7.54
pe 4
redox pe
units mg/l
density 1
F 0.39
Cl 1.21
N(3) 0.08
N(5) 18.5
C(4) 0
Mg 2.12
Ca 15.4
Na 2.32
K 0.96
S(6) 14.1
Cu 0.00239
Zn 0.01842
Cd 0.0002
Pb 0.0009
Fe 0.0523
Mn 0.01
Al 0.1465
-water 1 # kg

EQUILIBRIUM_PHASES
Fluorite 0 0
Fix_H+ -9 NaOH 10
REACTION
CaCl2 1
1 in 10 steps
REACTION_TEMPERATURE
30

USER_GRAPH 1
-headings rxn Ca F SI("Fluorite")
-axis_titles "CaCl2 added" "Molality" "Saturation index"
-axis_scale y_axis auto auto auto auto log
-initial_solutions false
-connect_simulations true
-plot_concentration_vs x
-start
10 GRAPH_X RXN
20 GRAPH_Y TOT("Ca"), TOT("F")
30 GRAPH_SY SI("Fluorite")
-end
-active true
END

--- End code ---

i_azharkhan:
Thank you so much, sir. I really appreciate.
Sir, when I run it on phreeqc this code gives me a graph, but it is not what I want. Respected sir, I want fluoride removal percentage on the y-axis (lift) and pH on the y-axis (right) and calcium on the x-axis. I make some changes, but it gives me errors. Respected sir, I request you please make these changes for me because I don't understand how I should do it. Thank you.

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