Cellulose diacetate ultrafiltration membranes

Abstract

New technology was developed for molding of membranes for ultrafiltration from and the conditions of their fabrication were optimized. It was shown that the method of spontaneous phase separation on a calender allows regulating the structure of the membranes.The problems related to the most complete use of the constituent parts of milk have been partially solved by using the membrane method of ultrafiltration.New technology for dry-wet molding of membranes from cellulose diacetate (CDA) solutions in acetone, including spontaneous gelation in the first stage and prolonged completion of constructing the structure of the gel (pore structure) in the second stage was proposed.Spontaneous formation of the gel structure was conducted on the heated metal roller of a vertical calender. The temperature was varied within the limits of (35-45)__. 1 ~ and the rate of rotation of the calender roller was varied from 25 to 100 rpm. The rate of evaporation of the solvent increased with an increase in the temperature and roller rotation rate, which accelerated phase separation.Films (0.005-1.250)_+0.002 mm thick and 0.5-0.6 m wide were fabricated. The thickness and porosity of the films were varied by altering the concentration of the starting CDA acetone solution (7, 10, 15, 20 wt. % CDA), the volume of the solution applied to the calender roller, and the gap between rollers.The duration of the stage of dry molding (intermediate) conducted on the calender was 2-3 min. The stage of modification of the films in aqueous medium for 12 h at room temperature was then followed. Back diffusion of acetone and water occurred on contact of the film with the aqueous medium. The maximum degree of swelling was approximately 25%, so that membranes modified with water were used for the subsequent studies.The membranes obtained were used for ultrafiltration of curd whey to concentrate it.

Rheological properties of spinning solutions for cellulose acetate ultrafiltration membranes

“…Membrane processes are also widely used for ultrafiltration of milk and cheese whey [2]. We propose a new formula for fabricating ultrafiltration membranes from secondary cellulose acetate (SCA) in the present article.We propose adding ethyl alcohol to the SCAacetone and SCAacetonewater spinning solutions for fabrication of ultrafiltration membranes which we previously developed [3] in order to increase the homogeneity of the solution and correspondingly form a more homogeneous structure of the membranes and decrease their thickness nonuniformity.Solutions of SCA contain microgel particles (MGP), fragments of cellulose and hemicellulose (xylan, mannan, etc.) which did not undergo acetylation during etherification.…”

“…We propose adding ethyl alcohol to the SCAacetone and SCAacetonewater spinning solutions for fabrication of ultrafiltration membranes which we previously developed [3] in order to increase the homogeneity of the solution and correspondingly form a more homogeneous structure of the membranes and decrease their thickness nonuniformity.…”

Ultrafiltration membranes made of secondary cellulose acetate modified with active carbon

“…We made ultrafiltration membranes from SCA by the pouring method [4] using two fractions of active carbon small (85 μm) and large (160 μm). Active carbon pellets used in medicine and thus compatible with food products were ground and passed through a sieve with mesh of a certain size.…”