The calculation of osmotic pressure in Nanofiltration unit has been changed (see also Tutorial file ). Before the Van't Hoff equation was used:
In the new version, the Gibbs equation is used:
The linear assumption from the Van't Hoff equation is mostly accurate for low-concentration solutions or ‘ideal solutions,’ and at higher concentrations, the deviation from the ideal behavior is more significant. For that reason, the osmotic pressure in this work is calculated considering the water activity. In particular, the water activity is assumed to be equal to the mole fraction of water because appropriate Pitzer model parameters are not available.