MODELLING OF TEMPERATURE EFFECTS ON THE PERFORMANCE OF REVERSE OSMOSIS MEMBRANES

This paper investigates the modeling of temperature effects on the performance of reverse osmosis membranes at the level of brackish-water concentrations. A new approach in modeling is employed in which the temperature dependencies of the physical properties of the system (such as diffusivity and viscosity) are taken into account and incorporated into the recently developed modified surface force-pore flow (MD-SF-PF) model. The dimensionless potential function in the model, which describes the solute-membrane interactions, is assumed to be temperature independent, which is justified based on an analogy to the interaction energy for the case of parallel flat plates. The three parameters in the model are determined at 25°C and 2000 ppm NaCI-water solution. Based on these parameters, the temperature-extended model predicts the performance of four thin-film composite, aromatic polyamide, FilmTec FT30 commercial membranes, in a temperature range of 5-60°C and a pressure range of 350-7000 kPa. The extended model truly predicts the performance of the membranes well. The compaction effect has no effect on the prediction of membrane separation and the ratio of solution flux to pure water flux. The compaction effect is modelled empirically which then allows the calculation of the absolute solution flux and pure water flux.