Ultrafiltration membranes made of secondary cellulose acetate modified with active carbon

Abstract

It was hypothesized that active carbon will play the role of an inert filler and cause the formation of a more developed pore structure in membranes since pores are formed as a result of the counteraction of the forces of contraction and adhesion during phase separation in evaporation of the solvent. The carbon particles perturb the structure of the polymer network. The porosity of the membranes also increases because the filler has a porous structure. Active carbon can be used to improve the performance properties of membranes.One method of increasing the food and biological value of dairy products is to include new kinds of raw materials and additives with a high protein content and scarce amino acids lysine and threonine in the formula. Cheese whey is widely used in practice to manufacture products enriched with protein.Membrane methods, ultrafiltration in particular, are used for processing cheese whey [1]. The ultrafiltration process is based on the membrane retaining dissolved particles larger than the size of the pores in the surface layer of the membrane. Adsorption of the components of the whey by the membranes accompanies ultrafiltration [2]. The efficiency of the ultrafiltration process is determined by the material from which the membrane is made. The search for the appropriate composition for manufacturing membranes is still urgent.Judging by the published data, using membranes made of secondary cellulose acetate (SCA) is promising for ultrafiltration. Such membranes are compatible with food products. They are easy to fabricate and consist of a chemically modified natural, renewable product.We manufactured modified composite ultrafiltration membranes for separating protein-carbohydrate raw material on the example of cheese whey. The membranes were modified by incorporating active carbon to create a more developed pore structure, since active carbon is known to contain pores.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. The concentration of the initial solution and content of filler in the solution were varied. The calculated amount of active carbon was placed in an acetone solution of SCA, mixed well, and films were poured. Membranes were formed over 24 h at 20°C. The performance and physicomechanical properties, water absorption, and swellability of the membranes obtained were investigated.The graphic dependences of the duration of swelling of the membranes in water on the filler content for different concentrations of the initial solution of SCA in acetone with the filler small and large fractions of active carbon are shown in Fig. 1. In analyzing the curves in Fig. 1, note that the lower the concentration of the initial solution for making the membranes, the shorter the swelling time and the more rapidly the system attains equilibrium. Membranes from a 5% initia...