Effect of pH on Total Volume Membrane Charge Density in the Nanofiltration of Aqueous Solutions of Nitrate Salts of Heavy Metals.

The separation efficiencies of aqueous solutions containing nitric salts of Zn, Cu, Fe or Pb at various pH in process of nanofiltration have been investigated experimentally. These results were used to obtain the total volume membrane charge densities, through mathematical modelling based on the Donnan-Steric partitioning Model. The experimentally obtained retention values of individual heavy metal ions varied between 36% (Zn at pH = 2), 57% (Pb at pH = 2), 80% (Fe at pH = 9), and up to 97% (Cu at pH = 9).