EFFECTS OF pH AND ADSORBED HYDROLYSED METAL IONS ON THE PHOTODISSOLUTION OF COLLOIDAL CADMIUM SULPHIDE.

Abstract

The quantum yields for the photodissolution of colloidal CdS in Ludox stabilized aerated solutions, have been measured as a function of pH. It has been found that the quantum yield decreases with increasing pH. Electrophoresis measurements indicate that this decrease is due to the formation of Cd**2** plus hydrolysis products on the surface of the colloid as the pH is increased. Support for this conclusion is obtained from experiments in which hydrolysed Co**I**I, Ni**I**I and Zn**I**I species were deliberately deposited onto CdS colloids. The reactions involved in the photocorrosion of CdS are discussed in light of the present results and with respect to mechanims proposed in the literature..