ADSORPTION OF COPPER, NICKEL, AND COBALT BY OXIDE ADSORBENTS FROM AQUEOUS AMMONIACAL SOLUTIONS

Experimental measurements of the uptake of Cu, Ni, and Co by oxides in aqueous ammoniacal solutions show that the adsorption behavior exhibits maxima and minima which depend on pH, ammonia concentration, metal cation, and the adsorbent. Electrophoretic studies on these systems indicate that oxide colloids may undergo as many as five charge reversals in aqueous ammoniacal solutions of hydrolyzable ammine complex-forming metal ions. For interpreting the behavior of these systems, a competitive adsorption model is presented that combines double-layer theory with properties of the adsorbent, the solvent medium, and the aqueous ionic species.