Question

what is the relationship between osmosis pressure and TDS ?

and the relationship between osmosis pressure with temperature

subject: application of chemical engineering

Answer 1

Roughly, every 100 ppm of total dissolved solids (TDS) contributes about 1 psi of osmotic pressure. For instance, if the TDS of feed water is 2,000 ppm then the natural osmotic pressure for this water is about 20 psi.

Osmotic pressure is driven by the tendency of the solute molecules that are not glueing together to take up as much space as they can get. This is the same as for molecules in the gas phase, and described by the ideal gas law: pV=nRT. All else staying equal, this gives a direct proportional relationship between temperature and pressure.

The added pressure can be considered to be due to the higher speed of the molecules: at higher temperatures molecules move faster, giving both more energetic and more frequent bounces off the walls of a container.

There is a relation i.e : Π(pie) = CRT which shows that Osmotic pressure (Π) is directly proportional to temperature due to which osmotic pressure depends on temperature.

From the van't Hoff equation, the osmotic pressure is directly proportional to the system temperature, which is an indispensable factor for the FO process.