Kinetic investigation of reaction between metallic silver and nitric acid solutions in the range 7.22-14.44 M

In this study, the reaction kinetics between metallic silver and nitric aci d solutions was investigated by taking into consideration the parameters of temperature, solid-to-liquid ratio, particle size, stirring speed, nitric acid concentration, and addition of sodium nitrite. It was determined that the dissolution rate of the process increased with decreasing particle size , solid-to-liquid ratio, and acid concentration, and increasing reaction te mperature and stirring speed. It was found that the-amount of sodium nitrit e in the solution has no significant effect on the dissolution rate. In the present study, the examination of shrinking core models of fluid-solid sys tems showed that the dissolution of metallic silver in the range of 7.22-14 .44 M nitric acid solutions was controlled by the film diffusion. The follo wing semiempirical model, which represented well the process, was developed by statistical methods: (5271.13)(D)(-0548)(S/L)(-0.3)(W)(0.851)(C)(-3.41) e(-18.81/RT)t, where D is the particle size, C the acid concentration, S/L the solid-to-liquid ratio, T the reaction temperature, W the stirring speed , and t the reaction time. The activation energy of the process was found t o be 18.81 kJ mol(-1).