Error in a simple solution with Exchange site

[JW]

I would like to simulate just a simple solution; a solid who has exchange site is added into a pure water.
So, I coded as follows with the database, llnl.dat.

SOLUTION 1
   ph 7 charge

EXCHANGE 1
   X 1

But, it resulted in a convergence error.

Please, let me know what is wrong in the code.
Thank you in advance.

[dlparkhurst]

What cations will fill the exchange sites? Considering the database you are using, which exchange reactions would be applicable?

[JW]

I see.
I had to define associated cations in SOLUTION when EXCHANGE was defined.
OK. Thank you.

[dlparkhurst]

Yeah, phreeqc.dat does not have a definition for HX (it is commented) and H+ is the only cation in your solution. So, you could define or uncomment the HX reaction, but that would give you an inititial exchange composition of HX, which is unrealistic. Better to initialize with a a solution that has a plausible cation.

You can initialize the exchanger without equilibrating with a solution:

Code: [Select]

EXCHANGE
NaX 0.5
CaX2 0.1
END