The chemists of St Petersburg University, working in collaboration with Belarusian scientists, continue developing new membrane materials for dehydration and water purification. The project headed by Anastasiya Penkova, an associate professor at SPbU, is carried out within the framework of a grant from the Russian Foundation for Basic Research and the Belarusian Republican Foundation for Fundamental Research. The project is aimed at developing new modified polymeric membranes for their subsequent application in various industries.

Polymeric membranes modified with various nanoparticles are of great interest not only from a fundamental perspective, but also in terms of the application of these technologies in medicine, pharmaceutics, petrochemical, food and other industries, as well as the creation of environmentally friendly, energy- and resource-saving technologies.

In the course of this research, the scientists of St Petersburg University are developing new nanocomposite polymeric materials for functional purposes to be used in membrane processes. Special attention is paid to studying the behaviour of nanocomposite membranes for the separation of liquid mixtures (including industrially significant ones) in membrane processes, such as the processes of pervaporation and ultrafiltration.

Today, there is a wide variety of membranes created on the basis of either polymeric or inorganic materials. Both the classes have their own advantages and disadvantages.

Thus, polymer membranes have good mechanical properties, good film formability and reproducibility of transport characteristics. In addition, they have high packing density per unit volume of the membrane module, controllable pore sizes and a lower cost compared to inorganic membranes. Moreover, they are relatively easy to produce. The disadvantages of polymeric membranes include low resistance to contamination during operation, low permeability and insufficiently high chemical and thermal resistance.

Inorganic membranes, on the contrary, have good chemical and thermal stability as well as high selectivity. The latter advantage is explained by the fact that membranes of this type do not swell in the separated components, in contrast to their polymer competitors. The disadvantages of this type of membranes include fragility, labour-intensive production and a high price for inorganic materials.

A perspective method for eliminating these drawbacks can be creation of mixed matrix membranes that would contain a dispersed inorganic or polymeric filler in the polymer matrix.

In the course of their research, SPbU scientists use the most relevant and economically justified method to improve the properties of polymeric membranes for their use in dehydration and water purification processes — modification of the known polymeric materials with good physico-chemical and film-forming properties.

"As a result, we will for the first time develop new polymeric membranes modified with water-soluble fullerene derivatives and block copolymers of polyethylene glycol and polypropylene glycol for dehydration and water purification processes," Anastasia Penkova said. "In addition, we plan to prepare new thin-film composite membranes for dehydration using ultrafiltration substrates. They will also be developed in the course of our research."

The application of its results, according to the scientist, will bring about a significant economic effect, since such membrane processes as pervaporation and ultrafiltration are environmentally friendly, energy-intensive and do not require large material costs. The use of membranes with a mixed matrix will ensure highly efficient purification of water from organic solvents (alcohols, tetrahydrofuran, etc.), separation of azeotropic mixtures and close-boiling components, concentration and fractionation of mixtures. The membrane methods developed by the SPbU scientists may become an alternative for the already existing processes of separation in industry. Moreover, they can be used not only individually, but also in combination with other separation processes, this undoubtedly leading to an improvement in industrial process flows.