Rotating Ring‐Disk Electrode Studies of Cyanocuprous Ion Oxidation on Platinum

Abstract

The anodic oxidation of cyanide ion is catalyzed by the addition of cuprous ion. Studies with a platinum‐platinum rotating ring‐disk electrode indicate that at the anode cyanocuprous ion is oxidized to adsorbed cyanocupric ion which then decomposes primarily by a heterogeneous quasi‐second‐order intracomplex redox reaction. The rate of this heterogeneous reaction increases roughly linearly with homogeneous cyanide concentration, indicating a fundamentally different reaction mechanism from the homogeneous decomposition of the tetracyanocupric ion. An analytic model has been developed to simulate the effect of the heterogeneous reaction on the rotating ring‐disk electrode system. This model reproduces adequately the collection efficiencies observed experimentally.

The electrochemical oxidation of alkaline copper cyanide solutions

“…The currents in this region were found to be somewhat irreproducible and the Tafel slopes were typically around 140 Á/200 mV per decade. Such irreproducibility tends to be the characteristic of a surface sensitive, heterogeneous reaction, thus supporting the results of Hofseth and Chapman [10,11]. The Tafel slope is indicative of a rate determining step involving the initial electron transfer.…”

“…The mechanism for cyanide oxidation in the presence of copper has been suggested in the literature to be [10,20]: 6 ] 2( , however the exact steps remain to be determined. This mechanism has been considered as a solution reaction [20], though others feel that the predominant path involves a surface adsorbed intermediate [10].…”

“…This mechanism has been considered as a solution reaction [20], though others feel that the predominant path involves a surface adsorbed intermediate [10]. This would not be surprising because the anionic nature of the possible intermediates.…”

Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

“…In our previous work, no oxidation current is found for alkaline sodium cyanide at the glassy carbon electrode at potentials below oxygen evolution [20]. With copper present, at low overpotential, and without sufficient hydroxide [20] the reaction mechanism for cyanide oxidation has been suggested in the literature [13,21]. 2) .…”

“…Electrochemical methods for treating copper cyanide solutions have been investigated by numerous researchers [9][10][11][12][13][14][15][16][17][18][19][20]. In electrochemical methods, while cyanide is oxidized to cyanate at the anode, copper is recovered at the cathode avoiding copper precipitation.…”