Kinetic mechanism of selenium leaching from selenium-rich acid sludge in NaOH solution

Abstract

Recovery of selenium from selenium-containing materials by metallurgical techniques is important. In this paper, the selenium was leached from the selenium-rich acid sludge via a direct NaOH leaching method. In order to analyze the leaching rate of various experimental conditions, certain parameters such as dosage of H2O2, NaOH concentration, leaching temperature, reaction time and liquid–solid ratio were also investigated. Particularly, the leaching rate of Se reached 98.94% under the optimal leaching condition, such as the H2O2 dosage of 75 mL·L−1, the NaOH concentration of 6.25 mol·L−1, the leaching temperature of 363 K, the reaction time of 120 min, and the liquid–solid ratio of 10. The unreacted nuclear dynamical model and homogeneous reaction kinetic model were then respectively utilised to describe the leaching kinetics of the Se leaching process. The results indicated that the homogeneous reaction kinetic model was more suitable than the unreacted nuclear dynamical model. Based on an analysis of leach kinetics, the leach was shown to proceed via homogeneous reaction. This work is of great practical value in terms of recovery of selenium from selenium-rich acid sludge with efficient and low cost methods.