Conceptual Models > Database selection and modification

Phreeqc.dat vs. Pitzer.dat in low-medium ionic strengths

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AzadGhadirian:
Hello everyone!

I am trying to model a simulation of a brackish water reverse osmosis desalination. I am specially modelling the rising concentrate and the precipiation of the different salts (mostly calcium sulfate dihydrate, Na, Cl, SiO2 and some Magnesium). I am focussing on the amount and order of the salts precipitating. Here I start with a solution with an ionic strength of 0,3 mol/kg and end at an ionic strength of 1,3 mol/kg. In a second simulation I evaporate the whole water in the concentrate so I reach very high ionic strengths.

Usually I am using the Pitzer database since I have read in several sources that the Pitzer database is the only one which has consistent thermodynamic data, has been assessed holisticly and is very accurate for high ionic strengths. Now I have found new papers in my research which show very good results for the phreeqc database aswell (specially in ionic strengths until 3 mol/kg).

 So my question is:
Should I use the phreeqc database for the first simulation (0,3 - 1,3 mol/kg) and then the pitzer database for the second simulation (1,3 - >10 mol/kg)
Or is the pitzer database more reliable even for low ionic strengths?

Since I am writing a scientific paper I need reliable sources and I only found that the pitzer database is assessed holisticly, not the phreeqc database.

Regarding the limitation of the ions: since I am focussing on the main precipitations the limited selection of the ions in the pitzer.dat is enough for my purpose.


I hope I have explained my situation understandable.
Thank you very much for your suggestions!

All the best,
Azad

dlparkhurst:
I think it would be most consistent to use pitzer.dat for all of your simulations. If you need to consider elements not contained in pitzer.dat, then you will need to use another database for those calculations.

AzadGhadirian:
Thank you very much for your reply Mr. Parkhurst!

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