Separation of precious metals using selective mesoporous adsorbents

The mesoporous NH2-MCM-41 adsorbent prepared by grafting aminopropyls on MCM-41 is selective towards gold and palladium adsorptions and can separate these precious metals from complex solutions containing other metal ions such as cobalt, nickel, copper and zinc. Adsorption is rapid and the adsorbent's capacity for gold is better or comparable to most carbonaceous adsorbents including activated carbons. Furthermore, NH2-MCM-41 can separate palladium from gold solution at pH1.0 with excellent selectivity and capacity. Thus, it is possible to design a two steps separation process for the separation of palladium and then gold from the complex solution. A simple acid wash was sufficient to recover the adsorbed palladium and gold as concentrated, high purity (i.e.. > 95%) metal salt solutions and the regenerated adsorbent was reused without lost of performance.