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.
The results of the study indicated the significant adsorption interaction of the components in the adsorAdsorption phenomena accompany many industrial processes, determining their contribution to the overall state of a real physicochemical system. Up to now, adsorption on porous polymer sorbents, in particular during ultrafiltration of curd whey, has been inadequately studied since the role of adsorption processes is considered insignificant. In addition, the problem of a comprehensive study of adsorption equilibria is difficult due to the complexity of the intermolecular interactions of the multicomponent mixtures.One of the most important problems in adsorption theory is to develop methods for the experimental and theoretical investigation of adsorption equilibria in binary and muiticomponent systems.Thermodynamic adsorption theory is based on the correlation of the experimental adsorption value with the thermodynamic functions of the system as a whole. It can be used to characterize adsorbate--adsorbate and adsorbate--adsorbent interactions.The following topics were considered in our article: -analysis of the adsorption isotherms of the low-molecular-weight components of curd whey on cellulose diacetate membranes; -calculation of the thermodynamic functions of the adsorption system; -determination of the character of the adsorbate--adsorbate and adsorbate--adsorbent interaction.
Studies showed that industrial PA membranes can be used for comprehensive treatment of whey containing substances of value to the food industry and allow separating 80% of the protein components in it. PA membranes have ion-exchange properties that allow separating from 20 to 40% of salt cations and anions from the whey and using them in production of food products.Secondary dairy stock (whey and buttermilk) frequently enter the wastewaters of industrial enterprises together with industrial waters and other production wastes. In pouring secondary dairy stock in the sewage system, we not only pollute the environment, but we also lose the additional commercial product that can be made from it.An analysis of the experience of the leading companies in the sector shows that as a function of the product volumes and lines pressed from whey and buttermilk, the additional profit would be 15-35% of the profit obtained from the basic product. It is thus not possible to underestimate the value of secondary dairy stock as product and raw material whose processing is unusually promising, economically advantageous, and environmentally necessary.Membrane methods, ultrafiltration in particular, are the most promising for processing secondary dairy stock. Despite the unconditional promise of membrane methods, they are not sufficiently utilized in industry due to the low output of membrane equipment.Increasing the specific separating surface per unit of working volume of the equipment has been successfully solved by using hollow fibres with semipermeable walls as membranes [1]. We used semipermeable polyamide (PA) membranes in the form of hollow fibres for separating whey. Proteins and mineral salt ions were separated from whey with PA membranes and the performance characteristics of the membranes were determined the permeability for water and whey, selectivity for protein, and ability to retain mineral salt ions.Whey obtained as the usual product of the dairy industry is a valuable protein-carbohydrate raw material. It basically contains protein nitrogenous compounds, organic acids, mineral salts, and a small amount of carbohydrates, vitamins, lipids, enzymes, and trace elements. Whey can be fractionated by ultrafiltration and food additives with the required composition and properties can be obtained. Ultrafiltration is widely used for production of protein concentrate from whey, which is the most valuable of the existing food proteins.Industrial semipermeable VPU-15-PA membranes made of an aromatic polyamide were used for the first time in the study. Ultrafiltration was conducted on a laboratory setup consisting of a nitrogen tank, a manometer, intermediate and receiving tanks, and ultrafiltration module filled with membranes.Ultrafiltration was conducted under 0.2 MPa pressure and 1.5 liters of product was investigated per cycle. The permeability and selectivity of the PA membranes were determined. The permeability is the amount of filtrate obtained per unit of time per unit of working membrane surface. To determine the permeab...
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