Re: RO and entropy

R Britt (
Mon, 21 Feb 1994 17:51:53 -0800 (PST)

Well Barry,
That is why it takes pressure to "drive it backwards". The membrane
pores are too small to allow the solvated ions through.
But it takes added pressure to drive the water molecules back
against the entropy. It all works out fine if you calculate
such things with the molar Gibbs energy, ie the "chemical potential",
that keeps track of the entropy contribution as well as the
"mechanical" potential energy terms.