Quantifying Copper Leaching Kinetics Processing Wastes as a Function of Composition and Mineralogy

Environmental management of mineral processing wastes, particularly from lead and zinc operations, is critically important due to their high heavy metal content. This study evaluated the potential for copper release and its controlling factors from wastes of the Zanjan Lead and Zinc Processing Plant, using two representative samples (S۱ and S۲). Bulk chemical composition was analyzed by XRF, major minerals identified via XRD, and particle morphology examined with SEM. Metal release potential was assessed in batch leaching experiments varying contact time (۰-۳۶۰ minutes), liquid-to-solid (L/S) ratio (۲۰:۱ to ۲۰:۱۶), particle size (۰.۰۴۵-۲ mm), and pH (۱-۱۴), with copper concentrations in leachates measured by ICP-OES. Chemical analyses showed that the wastes primarily consist of oxides of silicon, aluminum, iron, and calcium, with significant levels of lead, zinc, and especially arsenic. XRD confirmed quartz (SiO۲) and gypsum (CaSO۴-۲H۲O) as the dominant crystalline phases forming the waste matrix. SEM revealed morphological differences, with S۲ displaying a more porous structure and likely higher organic/carbonate content (consistent with ۲۷.۲% LOI). Leaching tests indicated strong dependence of copper release on pH and L/S ratio, with maximum release at strongly acidic pH (۱-۴). Increasing L/S ratio exponentially reduced copper concentration in solution but increased cumulative extracted copper, suggesting rapid release from accessible surface fractions. Despite simple mineralogy, the wastes pose high environmental risk due to elevated arsenic and other heavy metals. Gypsum, as the primary phase, influences metal release through both physical properties and relative solubility. Copper release followed biphasic kinetics-initial rapid followed by slower-reflecting distribution across phases of varying solubility. Findings emphasize that initial runoff under low L/S conditions will carry the highest contaminant loads. Effective management requires continuous monitoring and engineered runoff control systems.

کلیدواژه ها:

Copper leaching ، Mine waste ، Heavy metals release ، Acid mine drainage