Lead leaching mechanism and kinetics in electrolytic manganese anode slime

Abstract

Anode slime is produced by electrolytic manganese production enterprises. The effects of anode slime particle size, leaching temperature, leaching agent concentration, and leaching time on the extent of lead leaching were investigated using ammonium acetate as the leaching agent. The lead leaching mechanism and kinetics in the anode slime were also studied. The extent of lead leaching of anode slimes with different particle sizes is significantly different. The extent of lead leaching was increased by elevating the leaching temperature. The extent of leaching reaches 99.3% after 30 min of leaching when the average particle size of anode slime approaches 10 μm, the leaching temperature is 80 °C, and the concentration of ammonium acetate is 2 mol/L. Due to the high-temperature roasting, the high valence state of the lead is changed. Then, both the compact structure between the wrapped lead and the external anode slime and the dense structure between the coated lead and the anode mud outside are destroyed. A multidimensional tunnel and a porous network structure with cracks are formed. Under the mechanism of the complex, lead is transferred from the solid phase to the liquid phase. The lead leaching process followed the “shrinkage particle model”. The reaction is mainly controlled by the diffusion of solid product layers. The apparent activation energy of the reaction Ea (28.521 kJ/mol), the pre-exponential factor A (13.34), and the macroscopic kinetic equation are obtained by establishing a macroscopic dynamic model based on the experimental data.