The effect on the surface properties of eponit charcoal of impregnation with K 2Cr 2O 7 solution at various pH values

Abstract

The effect of the impregnation of Eponit charcoal with K 2Cr 2O 7 solution at different pH values was studied by polarographic and surface techniques. In acid media, where dichromate ions predominate, the Eponit charcoal was oxidized. The oxidation reaction was found to be first order with respect to the dichromate, and an increase in the concentration of H + ions accelerated the reaction rate. Although the cation exchange capacity of the Epoint charcoal had increased markedly after oxidation, the surface area for gas adsorption was decreased. This decrease was interpreted as being due to blockage of the narrow pores by the Cr 3+ ions. In alkaline media, where chromate ions predominate, no oxidation of the Eponit charcoal took place but preferential adsorption of OH - groups on the Eponit surface enhanced solution occurred. Adsorption of OH - groups on the Eponit surface enhanced the dipole-quadrupole interaction with nitrogen, and hence there was a slight variation between monolayer and multilayer adsorption.