Kinetics of Cobalt and Manganese Precipitation from Acid Mine Drainage Using Ozone

Cobalt (Co) and manganese (Mn) are among the critical elements listed by the U.S. Department of Interior, and Acid Mine Drainage (AMD) is one of the potential secondary resources for these elements. Recovery of these elements from AMD requires elevated pH (~9) or utilizing costly oxidants. Building upon our previously published work (patent-pending), the ozone oxidative precipitation process was employed to minimize chemical usage and efficiently recover these elements from AMD. The effects of process parameters (specifically, gas-flow rate, stirring rate, and temperature) on precipitation of Co-Mn from AMD were investigated. It was found that Co-Mn recovery is enhanced by increasing gas flow rate, temperature, and stirring rate to certain values, below which the results were not significantly different at 95% confidence level. Furthermore, a kinetic study of the Co-Mn oxidative precipitation was performed, and the activation energy values of the reactions were calculated. The effect of process parameters, along with the calculated activation energy values using the Pseudo-homogeneous model, collectively suggested that the ozone oxidative precipitation of Co-Mn is likely diffusion-controlled.