Comparative study of the retention of monovalent salts by nanofiltration: Application to natural water
Many people are exposed to excessive fluoride in their drinking water. This is the case of the population living in southern Algeria. Excess fluoride causes disabling conditions: dental and skeletal fluorosis. The main objective of this work is to study the effect of pressure and solute concentration of salts on their retention by nanofiltration. In a first step, we determined flow and retention performance parameters for the ionic solutes NaF, NaBr, NaCl and NaI using the nanofiltration membrane NF 270. Secondly, defluorination of natural brackish waters from southern Algeria was carried out. The nanofiltration tests show that the retention of anions following the order: F‐ &gt; Cl‐ &gt; Br‐ &gt; I‐. The NF 270 membrane retains the ions better at a pressure of 10 bar. Beyond this value, the retention of ions leveled off at the different studied pH values and then decreased. At low concentrations (10‐3 M), the retention limit of the solutes studied was greater than that at a higher concentration (10‐2 M). It was finally shown that fluoride ions can be selectively retained from hyper-fluorinated natural brackish water (at a rate over 82%) in the presence of other ions.