MEMBRANES FOR ULTRAFILTRATION, OF GRADUATED FINENESS DOWN TO MOLECULAR SIEVES

Area of Science:

• Chemistry
• Materials Science
• Physical Chemistry

Background:

• Ultrafiltration is a key separation technique.
• Cellophane's potential as an ultrafilter requires detailed investigation.
• Understanding pore size effects is crucial for molecular separation.

Purpose of the Study:

• To evaluate cellophane's efficacy in ultrafiltration.
• To develop methods for controlling cellophane pore size for molecular sieving.
• To differentiate ultrafiltration from other separation processes.

Main Methods:

• Swelling cellophane in water to alter pore structure.
• Progressively decreasing pore size through controlled methods.
• Testing separation of molecules (e.g., sucrose) and colloidal particles.
• Comparing cellophane with collodion membranes and other ultrafilters (e.g., Bedicher, pig's bladder).

Main Results:

• Swollen cellophane retains colloidal particles but not molecules like sucrose.
• Methods were developed to create fine molecular sieves from cellophane.
• Cellophane's sieve structure is critical for its ultrafiltration performance.
• Collodion membranes exhibit inconsistent properties, while Bedicher and pig's bladder show varying retention capabilities.

Conclusions:

• Cellophane can be effectively utilized as a molecular sieve in ultrafiltration.
• The sieve structure of the membrane is the primary factor in separation.
• Ultrafiltration is a distinct process, separate from diffusion, dialysis, osmosis, electroosmosis, or thermodynamics.