The separation of cadmium, zinc, and lead from aqueous solutions using inorganic solid-phase extractants has been examined. An inorganic solid-phase extractant (ISPE-302) was prepared by attachment of his (2,4,4-trimethyl)monothiophosphonic acid on a functionalized silica surface. Results of preparation and characterization studies are presented here. FTIR spectral studies show van der Waals type interactions between the alkyl chain of the extractant and the functional groups bonded to the silica surfaces. ISPE-302 exhibits the selectivity series of cadmium > lead > zinc. The initial capacity of 0.175x10(-3) mol of cadmium/g of ISPE-302 achieved is 89% of the theoretical capacity. The capacity of ISPE-302 decreases to 0.5x10(-)4 mol/g, which is likely due to loss of extractant. Cadmium, lead, and zinc were separated by selective stripping from the bed saturated with these metal ions. These results indicate ISPE-302 has potential for separation of these metal ions from dilute aqueous solutions.