Potential use of carbon felt in gold hydrometallurgy

The use of carbon felt as a three-dimensional electrode appears to be very promising for the recovery of heavy metals, and toxic compounds removal from dilute solutions, considering its favourable physico-chemical properties: high specific surface area, good fluid permeability and compressibility, chemical inertness and good electrical conductivity. ork presents the contribution of the carbon felt electrode in two different steps of the gold cyanidation recovery process • tly as a cathode for the electrowinning of gold solution obtained after the elution of loaded carbon; x02022; ndly as an anode for the electro-oxidation of cyanide ions present at low concentration (200–300mg/l) in waste streams. first case, more than 10 kg of gold per m2 of felt (2000 kg of gold per m3 of felt) can be loaded at 400 A/m2 from dilute gold solutions (30 mg/l Au) with classic Faradic yields (6–12 %) and high overall extraction efficiency (>90 %). The felt homogeneously loaded with adhesive gold deposit can be smelted in an electric furnace without addition of fluxes since the carbon felt decomposes in gaseous products without formation of ashes. second case, the cyanide ion concentration can be lowered to as low as 10 mg/l by electro-oxidation to cyanate form (CNO−) at 400 A/m2 in the anodic compartment of a divided cell. The presence of copper ion significantly improves the current efficiency of this electro-oxidation and sharply reduces the oxidation of the carbon felt. Copper ions accelerate the oxidation rate of free cyanide ions through the formation of easily oxidizable complexes owing to a mechanism in which the Cull Cull redox couple acts as an electron transfer mediator.