A numerical analysis describing acetone evaporation from a cellulose acetate casting solution is reported. Profiles of acetone density and acetone density gradient within the membrane are calculated as a function of evaporation time for three evaporation rates. The analysis indicates that, for a given composition of the casting solution, there are optimum evaporation times for the formation of the asymmetric skin, according to the composition of the casting atmosphere. These data make it possible to define a membrane 'productivity factor', which has a maximum value under conditions when the polymer is precipitating and the solvent gradient is maximized at the evaporating surface, and a minimum value when the solvent concentration throughout the membrane is below a critical value for polymer precipitation. A numerical analysis describing acetone evaporation from a cellulose acetate casting solution is reported. Profiles of acetone density and acetone density gradient within the membrane are calculated as a function of evaporation time for three evaporation rates. The analysis indicates that, for a given composition of the casting solution, there are optimum evaporation times for the formation of the asymmetric skin, according to the composition of the casting atmosphere. These data make it possible to define a membrane ?productivity factor? , which has a maximum value under conditions when the polymer is precipitating and the solvent density gradient is maximized at the evaporating surface, and a minimum value when the solvent concentration throughout the membrane is below a critical value for polymer precipitation.
Preparation of reverse osmosis membranes. A numerical analysis of asymmetric membrane formation by solvent evaporation from cellulose acetate casting solutions
OTTANI;
1981
Abstract
A numerical analysis describing acetone evaporation from a cellulose acetate casting solution is reported. Profiles of acetone density and acetone density gradient within the membrane are calculated as a function of evaporation time for three evaporation rates. The analysis indicates that, for a given composition of the casting solution, there are optimum evaporation times for the formation of the asymmetric skin, according to the composition of the casting atmosphere. These data make it possible to define a membrane 'productivity factor', which has a maximum value under conditions when the polymer is precipitating and the solvent gradient is maximized at the evaporating surface, and a minimum value when the solvent concentration throughout the membrane is below a critical value for polymer precipitation. A numerical analysis describing acetone evaporation from a cellulose acetate casting solution is reported. Profiles of acetone density and acetone density gradient within the membrane are calculated as a function of evaporation time for three evaporation rates. The analysis indicates that, for a given composition of the casting solution, there are optimum evaporation times for the formation of the asymmetric skin, according to the composition of the casting atmosphere. These data make it possible to define a membrane ?productivity factor? , which has a maximum value under conditions when the polymer is precipitating and the solvent density gradient is maximized at the evaporating surface, and a minimum value when the solvent concentration throughout the membrane is below a critical value for polymer precipitation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
