Elimination of nitrate ions in drinking waters by nanofiltration

This study is focused on the influence of the nature of the water to be treated on the efficiency of nitrate elimination by a commercial membrane. By gradually increasing the complexity of the treated solutions (binary, ternary mixtures and then natural waters), we identified the physical, chemical and electric phenomena, which govern the ion transfer. We highlighted the influence on the membrane selectivity of the hydration energy of the solute, of the membrane– solute and solute–solute interactions. The observations made with simple nitrated solutions (binary and ternary) were extrapolated and confirmed in experiments on the water doped out of nitrates.

The objective of this study was to contribute to a better comprehension of the transfer of the ion nitrate in nanofiltration. We thus highlighted the effect of the hydration energy of the various solutes in solution, the effect of the interactions membrane–solute and solute–solute on the retention of nitrates. The effectiveness of the nanofiltration in the treatment of natural water polluted by nitrates depends on these various factors. It should be noted that an increase in the concentration in divalent anion affects particularly the retention of nitrates, whereas that of a divalent cation tends to improve it.