Collect. Czech. Chem. Commun. 1995, 60, 1888-1904

Neutralization Dialysis. Problems and Outlook

Galina A. Tishchenkoa,b, Genadii A. Denisovc, Larisa K. Shataevab and Miroslav Blehaa

a Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic
b Institute of Macromolecular Compounds, Academy of Sciences of Russia, 199004 St. Petersburg, Russia
c Institute of Mathematical Problems of Biology, Academy of Sciences of Russia, 142292 Pushchino, Russia


Neutralization dialysis (ND) of model systems containing 0.1-0.5 M NaCl and various high-molecular-weight synthetic or natural substances have been investigated. Desalination experiments were carried out in a three-compartment spiral module equipped with heterogeneous Ralex or homogeneous Neosepta membranes. Practically complete desalination proceeds due to the neutralization reaction in the desalination compartment. The time of desalination depends only on the membrane permeability and on the initial salt concentration in solution. An important feature hindering larger application of this method is sharp pH changes occurring in the desalination solution. This phenomenon predicted theoretically is mainly caused by the difference in diffusivities of H+/Na+ and OH-/Cl- ion pairs. Independently of the type of membrane and desalinated solution, pH value jumps into acidic region at the beginning of the ND. In the course of the process the pH value increases and the ND proceeds mostly at pH < 7. On the basis of theoretical prediction, an experimental method consisting in adjustment of acid concentration is proposed, which makes it possible to maintain constant pH in the desalination compartment. The convenience of this method was demonstrated by the ND of protein solutions.