CEMENTATION KINETICS OF AN INDUSTRIAL SOLUTION OF AG(CN)(2)(-) WITH GRANULAR SPHERICAL ZINC IN A VIBRATING REACTOR

The kinetic behavior of the cementation of an industrial solution of A g(CN)(2)(-) with granulated spherical zinc in a vibrating reactor was investigated. The influence of parameters such as vibratory amplitude and frequency, cyanide and oxygen concentration, pH and temperature we re studied in an intermittent state. The reaction rate was analyzed in a continuous run. Some of the significant results are the following: (1) the process takes place in two steps, the first one consisting of an instantaneous cementation in which silver concentration in solution was reduced by 54% to 78% and the second, a slower one, with a reacti on order of one; (2) in batch tests, it with an oxygen was possible to perform the cementation at a rate of 2.49 x 10(-4) mg cm(-2) s(-1) co ncentration of 8 mg l(-1) (2.5 x 10(-4) M); (3) the critical effect of the cyanide concentration on the reaction kinetics, found with differ ent techniques in other investigations, was not observed in this study ; (4) the granulated zinc was not passivated in the 77.5 min of the co ntinuous test. (C) 1998 Elsevier Science B.V.