Use of ultra- and nanofiltration ceramic membranes for desalination

The filtration tests of electrolyte solutions performed with different ceramic membranes show that salt rejection depends on pH, salt nature and concentration. A simple correlation between streaming potential and rejection rates exits and confirms that streaming potential is a relevant parameter to characterize the surface charge of filtering material during the filtration process.

The efficiency of a filtration process depends on the complexity of the filtered solution. In the case of an ionic solution, the steric and electrical interactions are the two main parameters which must be considered. The steric effect depends on the stability of the formed complex between the cation and the ligand. For simple electrolytes, the rejection depends on the electrical interactions, which are controlled by the surface charge developed on the filtering material. Generally, the streaming potential measurement across the membrane seems to be a good parameter to predict the rejection rates of the salt instead of electrophoretic powder mobility, which sometimes is not in agreement with salt rejection.