Question

At 25 °C in a lab membrane with area A = 2 *10^-3 m² we feed a solution of 10 kg NaCl per m³ solution so well mixed that essentially it has the same strength leaving.

The permeate is measured as 0.39 kg NaCl per m³ solution at a rate of 1.92 * 10^-8 m ³.s^-1 when applying a constant pressure difference of 54.42 atm.

Calculate:

1. the permeance constants for the solvent

2. the permeance constants for salt (these type of constants are previously given, but this question shows

how they may be calculated experimentally)

3. the rejection coefficient.

Answer 1

Solution

This question shows how permeance constants, A(solv ) and A(salt), which are normally given, may be calculated

1. The solvent flux is given by 

So now the osmotic pressure difference can be found from

2. The permeance constant for salt is found from

3. The rejection coefficient is