Abstract
The objective of this study was to measure the charge density in the polyamide active layer of a commercial reverse osmosis membrane. To achieve this objective, cesium ion(Cs+)was chosen as a counter ion of the deprotonated carboxy group(R-COO-), and the mass of Cs+ that associates with R-COO- was measured with a quartz crystal microbalance(QCM). Experimental data showed that the charge density obtained in this study at the pH range between of 4.0-9.0 was in good agreement with those obtained using an existing method of Rutherford backscattering spectrometry(RBS). RBS is a powerful but not easily accessible technique. Therefore, the method investigated in this study can be used as a relatively easy and simple way that permits one to measure the charge density of polyamide active layers.