On the Extraction of Silver and Copper from Aqueous Solutions Using Hydrogenated Palladium

The degree of extraction of silver and copper from solutions of their salts by atomic hydrogen in Pd was studied, as well as the conditions for their most complete extraction. The Ag+ concentration was 12.67 and 0.635 g/L, and that of Cu2+ was 1.145 and 1.527 g/L. The residence time of Pd in solution was 1 h. Electrochemical hydrogenation of Pd was carried out in 1 M NaOH solution at 30 mA/cm2 for 9 min until completely saturated with hydrogen, at which H : Pd was 0.73. It has been established that the PdH system has the ability to efficiently extract silver (and copper) with 100% yield if the amount of hydrogen in Pd exceeds the amount of Ag in solution. The main conditions for this are solutions diluted with silver (with respect to copper) and a large working surface of Pd samples. It has been established that the chemical deposition of silver on PdH is accompanied by the formation of colloidal silver near the surface, which can be isolated from the solution. The main condition for this is a low hydrogen content in the sample (Н : Pd < 0.3). The result of this is a decrease in the rate of hydrogen diffusion to the sample–solution interface, and the lifetime of the colloid increases.