Theory 79/Energy Limits/Desalination
Desalination Has a Floor
The claim
The energy needed to separate salt from water is bounded below by the ratio of osmotic pressure to recovery, so higher recovery costs disproportionately more.
01Mechanism
The minimum work is the free energy of mixing, which diverges as the concentrate approaches saturation.
02Prediction
Specific energy should rise steeply with recovery.
03Refutation
Energy independent of recovery would remove the thermodynamic floor.