Dissolution kinetics of metallic zinc obtained from spent zinc‐carbon batteries in nitric acid solutions

Abstract

In this study, the dissolution kinetics of metallic zinc pieces obtained from waste zinc–carbon batteries was investigated using nitric acid solutions. The effects of the concentration of nitric acid, amount of metallic zinc, reaction temperature and stirring speed on the dissolution process were determined, and a mathematical model to represent the dissolution kinetics was presented. It was observed that the dissolution rate increased with increasing nitric acid concentration, stirring speed and reaction temperature and with decreasing amount of metallic zinc. While the concentration of nitric acid, reaction temperature, stirring speed, amount of zinc, and reaction time were 0.15 M, 30°C, 400 rpm, 0.1 g, and 20 min, respectively, the amount of dissolved zinc was found to be 98.3%. The result of the kinetic analysis showed that the dissolution rate fit to the pseudo‐first order kinetic. The activation energy for the dissolution process was calculated to be 12.89 kJ/mol. It was determined that the dissolution process was controlled by diffusion. Zinc ions in the resulting solution after the dissolution treatment was recovered by precipitation method using sodium bicarbonate solution. It was determined that zinc ions were precipitated as zinc hydroxy‐carbonate compound. Zinc compound obtained was subjected to the calcination treatment, and zinc oxide was produced.