The effect of illumination on the adsorption of dyes on zinc oxide

Abstract

The adsorption of uranine and rhodamine B, from ethanolic solution, onto high-purity polycrystalline zinc oxide has been determined in the dark, in natural room-light, and under ultraviolet irradiation. It is shown that the amount of uranine chemisorbed in room-light is approximately 60% greater than that chemisorbed in the dark. Ultraviolet irradiation effected a threefold increase in the amount of uranine chemisorbed, with a corresponding decrease in physisorption and total adsorption. The adsorption of rhodamine B, which is exclusively chemisorption, is significantly increased in room-light, and is approximately doubled by ultraviolet irradiation.