Silver recovery from an effluent generated by plating industry using a rotating cylinder electrode (RCE)

This paper concerns silver recovery from simulated rinse wastewater from the electrolytic cyanide silver process (1300 and 23,000 ppm of Ag(I) and CN, respectively, at pH 13 and 150 mS cm(-1) conductivity) using a laboratory scale RCE. Rotating disk electrode (RDE) studies revealed that at -1.35 <= E <= -1.15 V vs. SCE, the Ag(I)/Ag process is limited by mass transport. Global mass transport data were obtained by monitoring the (first order) concentration decay of Ag(I). The electrolyses were performed by maintaining a potential of -1.2 V vs. SCE and varying the Reynolds numbers between 7600 <= Re <= 45,400. Based on the Sh = aRe(b)Sc(0.356) correlation, the value of the constant a, associated with transport properties, shape and cell dimensions, was 0.11; the constant b exhibited a value of 0.99 attributed to rough silver deposits on RCE interface. The best electrolysis in terms of Ag(I) removal reached 8 ppm in 90 minutes, at Re = 45400 with a 98% current efficiency, and energy consumption of 1.5 KW h m(-3). The metallic silver and treated solution can be recycled back through the same electrolytic cyanide silver process. (C) 2014 Elsevier Ltd. All rights reserved.