2. Membranes are frequently prepared by an immersion precipitation process in which three components are used:...

 

Transcribed Image Text:

2. Membranes are frequently prepared by an immersion precipitation process in which three components are used: polymer (P), solvent (S), and nonsolvent (NS). Consider a system in which ethyl cellulose is used as a polymer, acetone as a solvent and water as a nonsolvent. The cloud point measurements in this system yielded the following results: Ethyl cellulose, % Acetone, % 62 20 Water% 18 40 41 19 14 66 20 10 68 22 50 20 46 79 4 1 a) Draw the ternary diagram with demixing region for this system (an empty ternary phase diagram is provided, however, you can generate your own). If the points (62,20,18) and (1,20,79) are in equilibrium, draw the corresponding tie line and show the location of the critical point. Please justify the location of the critical point. Hint: the location of the critical point will depend on how you will draw the demixing region; however there is a region beyond which the critical point cannot be located. It is considered to change the solvent in this system by replacing the acetone with THF or DMF. Table below summarizes the solubility coefficient along with the corresponding molar volumes of all existing and potential components of the system. Component Ethyl cellulose Acetone 8, (cal/cm)2 V, (cm/mol) 10.3 - 9.9 74.0 THF 9.1 81.7 DMF Water 12.1 77 23.4 18 b) Assuming that the concentration of ethyl cellulose at the critical point is independent of the solvent, using the ternary phase diagram for acetone, draw qualitatively the demixing regions for THF and DMF as the respective solvents in this system. Also draw the tie lines for the new solvents relative to that for acetone as a solvent. Carefully explain all other aspects of the ternary systems with new solvents. For membrane casting, several different conditions are considered, which are summarized below Casting solution 10%P, 90%Act 20%P, 80% Act 20%P, 80%Act. 20%P, 70%Act, 10% W 20%P, 70% Act, 10%W Coagulation bath 100% Water 100% Water 90%W, 10%Act. 100% W 90%W, 10%Act. 2. Membranes are frequently prepared by an immersion precipitation process in which three components are used: polymer (P), solvent (S), and nonsolvent (NS). Consider a system in which ethyl cellulose is used as a polymer, acetone as a solvent and water as a nonsolvent. The cloud point measurements in this system yielded the following results: Ethyl cellulose, % Acetone, % 62 20 Water% 18 40 41 19 14 66 20 10 68 22 50 20 46 79 4 1 a) Draw the ternary diagram with demixing region for this system (an empty ternary phase diagram is provided, however, you can generate your own). If the points (62,20,18) and (1,20,79) are in equilibrium, draw the corresponding tie line and show the location of the critical point. Please justify the location of the critical point. Hint: the location of the critical point will depend on how you will draw the demixing region; however there is a region beyond which the critical point cannot be located. It is considered to change the solvent in this system by replacing the acetone with THF or DMF. Table below summarizes the solubility coefficient along with the corresponding molar volumes of all existing and potential components of the system. Component Ethyl cellulose Acetone 8, (cal/cm)2 V, (cm/mol) 10.3 - 9.9 74.0 THF 9.1 81.7 DMF Water 12.1 77 23.4 18 b) Assuming that the concentration of ethyl cellulose at the critical point is independent of the solvent, using the ternary phase diagram for acetone, draw qualitatively the demixing regions for THF and DMF as the respective solvents in this system. Also draw the tie lines for the new solvents relative to that for acetone as a solvent. Carefully explain all other aspects of the ternary systems with new solvents. For membrane casting, several different conditions are considered, which are summarized below Casting solution 10%P, 90%Act 20%P, 80% Act 20%P, 80%Act. 20%P, 70%Act, 10% W 20%P, 70% Act, 10%W Coagulation bath 100% Water 100% Water 90%W, 10%Act. 100% W 90%W, 10%Act.