ISTOCK
Chemists at HSE University, Kurnakov Institute of General and Inorganic Chemistry, and the University of Science and Technology of China have developed membranes with enhanced properties. The researchers experimentally revealed the impact of various factors on the desalination process and on the selectivity of ion separation. According to the study authors, their research will enable a more precise prediction of the properties of new ion-exchange membranes used in water treatment and desalination. The study findings have been published in Desalination.
The study was supported by Grant No. 23-43-00138 from the Russian Science Foundation (RSF).
Each year, the global availability of fresh water is diminishing due to its intensive use, pollution, and inadequate development of water treatment systems in both industry and the domestic sector. Freshwater resources per person have dropped by 20% over the past two decades, and in 2023, according to the United Nations, 2.4 billion people lived in water-stressed countries.
Desalination of seawater is one method of producing drinking water. A variety of devices is used for this purpose, including ion exchange membranes. These thin, selective films have specific chemical groups that determine which ions are allowed to pass through and which are blocked. Electrodialysis is the method used in desalination: under the influence of an electric field, ions with the same charge are transferred through a polymer membrane and concentrated in a special chamber.
This membrane allows the passage of certain ions more readily than others based on their charge; for instance, chloride ions (Cl-) pass through more effectively than sulphates (SO42-). This characteristic is referred to as selectivity. In order to enhance the efficacy of water treatment devices, the ability to accurately evaluate membrane selectivity, considering the impact of external factors, is essential.
Chemists at HSE University, Kurnakov Institute of General and Inorganic Chemistry, and the University of Science and Technology of China conducted desalination experiments using two membranes: a commercial one and a modified experimental membrane obtained through layer-by-layer deposition of polyelectrolytes with different charges. They also developed a computer model that enables the evaluation of membranes' specific selectivity for single-charged ions, considering the influence of experimental factors. The researchers investigated the effects of various experimental conditions, including stirring, the composition and concentration of electrolyte solutions, pre-desalination, electric current, and distinctions between symmetric and asymmetric systems.
We systematised the methodology of the desalination process, demonstrating that the actual data aligns with the theoretical model. We hope that our work will facilitate more accurate predictions of the properties of future membranes.
The modified membrane proved to be more effective than its commercial counterparts in desalination experiments, and the separation efficacy increased with the increasing concentration of solutions. In the future, the researchers intend to design new membranes with enhanced selectivity for diverse electrochemical applications, such as extracting valuable components from industrial effluents.
IQ
Andrei Manin
Co-author of the paper, student at the HSE Faculty of Chemistry