# What's the lower limit for energy usage to desalinate water?

Consider a desalination process where you enter sea water and receive fresh water and brine (or maybe pure salt).

How do I compute the least amount of energy per mass? I think this has something to do with the entropy of the different mixtures, mostly dependent on the salt concentration in the brine. Is this correct? How to calculate?

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The result should be a positive number since the process is not spontaneous. However the value of $\Delta G$ will be the minimum non-mechanical work necessary for the process.