Novel and efficient removal of impurities from spent silicon contact mass via an in situ copper-catalyzed leaching process

As spent silicon contact mass (SCM) continues to accumulate, recovering silicon from this waste stream has become increasingly important for resource sustainability and waste management. In this study, we developed a novel in situ copper-catalyzed leaching strategy that exploits the copper naturally present in SCM to promote impurity dissolution in an oxidative acid-leaching system, thereby facilitating the efficient removal of impurities and the recovery of both silicon and copper. Compared with conventional leaching processes, the proposed approach substantially enhanced impurity removal. Under optimized conditions, the leaching efficiencies of iron, aluminum, and calcium reached 99.33%, 97.54%, and 99.59%, respectively, while the purity of the recovered silicon and the copper recovery efficiency reached 99.76% and 98.82%, respectively. The leaching kinetics of iron were analyzed using the shrinking-core and homogeneous-reaction models. The homogeneous-reaction model provided a better fit to the experimental data. When combined with activation-energy analysis, the rate equation, and its criterion number, these kinetic results provided further insight into the mechanism governing iron dissolution. Overall, this study demonstrates an environmentally sustainable strategy for the efficient removal of impurities and high-value recovery of resources from SCM. The proposed process offers a promising route for hazardous-waste valorization and supports cleaner production within a circular economy.