Salt and water permeability in reverse osmosis membranes

The permeate flux, permeate concentration, brine flux, and brine concentration have been experimentally determined. A pilot-scale reverse osmosis configuration consisting of 18 tubular-type cellulose acetate membranes has been used for the desalination of brackish water. The transport parameters (i.e., mass transfer coefficients) as well as the permeability coefficients (of water and salt) in reverse osmosis membranes, useful for the prediction of the membrane performance and membrane characterization, have been calculated by fitting the model predictions to the experimental results. A classical model, applicable for reverse osmosis systems, has been used. The effect of the operating conditions (pressure, flowrate, and concentration) on the model parameters has also been studied. Through the incorporation of six adjustable parameters to the model, the prediction results have been found to be in good agreement with the experimental data within the accuracy of the experimental determination. Finally, a study of the membrane performance on the rejection of six different ions (chloride, sodium, calcium, magnesium, bicarbonate, and sulphate) has also been made. The permeability parameter values for these ions have been determined and are reported. This option also yielded quite satisfactory predictions, as far as the permeate concentrations and flowrates are concerned.