Extraction of an Industrial Tin Compound from a Local Cassiterite Ore in Alkaline Media;leaching Studies

ABSTRACT
Cassiterite (SnO2) is the principal source of tin, but its extraction remains difficult due to its refractory nature. In this study, cassiterite ore from Sepeteri, Oyo State, Nigeria, was leached and characterized using XRD, XRF, SEM-EDS, and physicochemical analyses before being subjected to alkaline leaching experiments. Leaching was carried out with 1 g of ore in 100 mL KOH solution (0.01–1.0 M) under varying particle sizes (75–250 µm), temperatures (27–70 °C), and leaching durations (5–120 min). Dissolution behavior was interpreted using the shrinking-core diffusion model, and activation energy was determined from Arrhenius plots. The results showed that tin dissolution increased with both KOH concentration and temperature, achieving a maximum fractional recovery of ~0.20 at 70 °C after 120 min. At low KOH concentrations (0.01–0.05 M), dissolution was sluggish and surface-controlled, while higher concentrations (≥0.1 M) enhanced dissolution through the formation of soluble stannate complexes. Unexpectedly, larger particles (250 µm) exhibited higher dissolution than finer ones, likely due to aggregation or passivation of fine particles. Kinetic analysis confirmed diffusion-controlled leaching, with an activation energy of ~29.6 kJ·mol⁻¹, consistent with reported values for diffusion through product layers in refractory oxides. These findings demonstrate that Nigerian cassiterite can be upgraded and partially dissolved in alkaline media, with process efficiency strongly dependent on leaching parameters. The study highlights the need for optimization and possible integration with beneficiation and pyrometallurgical steps for effective industrial tin recovery.