Influence of operating parameters on the performance and efficiency of reverse osmosis membranes: modelling with the solution-diffusion model

• Main Authors: Шумбар, К.В., Щербак, А.І., Кравченко, М.В., Василенко, Л.О., Березницька, Ю.О.
• Format: Article
• Language: Ukrainian
• Published: Kyiv National University of Construction and Architecture 2024
• Subjects: dilute aqueous solutions; reverse osmosis; polymeric membrane; operating parameters; pressure; concentration; temperature; performance
• Online Access: https://es-journal.in.ua/article/view/321294

This work is devoted to the study of the influence of the main operating parameters (pressure, concentration, temperature) on the performance of reverse osmosis membranes and the use of the solution-diffusion transport model to predict their efficiency. The study provides a classification of reverse osmosis transport models for describing the flow of dissolved solutes and solvents through the membrane. The most common model for describing the transport of aqueous dilute solutions and salts in dense, non-porous polymers is the solution-diffusion model. This model allows for the prediction of the efficiency of solute retention depending on the applied external and osmotic pressure across the membrane, and salt transport is determined by the concentration gradient between the initial solution and the permeate. A scheme of the reverse osmosis process is presented, which includes: the profile of pressure, chemical potential and solvent activity at the solution-membrane interface in the solution-diffusion model; solvent behaviour in the membrane under pressure; division of the system into physical and chemical properties of the solvent and the solute inside the membrane. It is shown that the effect on permeability and solute retention is the result of the interaction of several factors, including the feed/operating temperature, which affects the membrane porosity, the concentration of the initial dilute aqueous solution, and the transmembrane pressure, which contributes to membrane compaction. It was found that an increase in the operating pressure leads to an increase in the driving force, which increases the water flow and the efficiency of solute retention. It was found that an increase in transmembrane pressure from 100 to 500 kPa increases salt retention from 82% to 94%, and the degree of salt retention decreases with an increase in solution temperature from 25 to 45 °C. It was found that with an increase in salt concentration from 1% to 8%, the degree of salt retention decreases from 99.5% to 97.8%. It is shown that the optimum permeation flux is observed at a temperature of 35 °C, especially 70 minutes after the start of operation, and the permeation flux decreases with time.