SURFACE-PROPERTIES OF A NEW-TYPE MNO2 ADSORBENT PREPARED ON A SOLID SUPPORT .4.

The electric double layer formed on the surface of the novel-type adsorbent was studied using Cu2+, Zn2+, Cd2+, Pb2+ and Mn2+ ions as model compounds. The concentration of surface groups decreased due to the metalhydroxo compounds (charge: +1 or 0) formed on the surface of the adsorbent after ion exchange. Stability constants extrapolated to pH(zpc) of the surface hydroxo compounds were found to be similar to that of MOH+ in solution. Copper ions behaved differently because in addition to adsorption, an ion exchange on natural clinoptilolite has been observed as a major factor of the binding of Cu2+ ions. Calculations based on the equilibrium constants of chemical reactions supported the formation of a Stern-layer on the MnO2 CLI solution interface. The interface can be estimated from the integral capacity values. The boundary of the Stern layer and diffusion double layer moved toward acidic pH in the presence of Cu2+ ions. In case of Cd2+, Zn2+, Mn2+ and Pb2+ ions the Stern layer was found to be wider and the increasing capacity values characteristic of the diffusion double layer could not be achieved in the pH range studied.