Specificity in the adsorption of dyes on oxide surfaces

Abstract

Total adsorption and chemisorption isotherms of the acid dye fluorescein and the basic dye rhodamine B from ethanolic solution have been determined for magnesium oxide, α-alumina, zinc oxide and kieselguhr. Molar ratios of the two dyes adsorbed on each of the oxides show a variation of more than two orders of magnitude for both physisorption and chemisorption, which demonstrates that the physical bond can be highly specific in this type of system.    

The effects of varying the liquid/solid ratio and of using different solvents have been studied, and it is suggested that significant improvements in the estimation of specific surface area by dye adsorption can be effected by appropriate selection of both dye and liquid/solid ratio.