Characterization and Upgrading of Zircon Sand from Central Kalimantan Placer Gold Mine Tailings for Zirconia Production

This research explores the characterization and upgrading of zircon sand derived from placer gold mine tailings in Central Kalimantan, Indonesia, for zirconia production. The tailings, a byproduct of intensified small-scale gold mining activities, contain zircon (ZrSiO4) that necessitates upgrading to meet industrial specifications (ZrO2 + HfO2 ≥ 65%). The characterizations include chemical composition, grain size distribution, mineralogy, degree of liberation, and photomicrographs. The physical upgrading methods consist of gravity separation that applies a shaking table, magnetic separation (MS), and high-tension separations (HTS). The optimal conditions for the shaking table were identified at a slope of 3°, a water debit of 12 L/s, and a feeding rate of 15 kg/h, resulting in a concentrate with up to 64.84% ZrO2. Magnetic separation was conducted at a magnetic intensity of 10,000 Gauss, and a feeding rate of 5 kg/h resulted in 65.32% ZrO2 concentrate. The optimum conditions for HTS are a tension of 30 kV at a 5 kg/h feeding rate which resulted in 66.21% ZrO2 concentrate. On the other hand, the alkali fusion method, which utilized sodium hydroxide at 650 °C for 60 min followed by acid leaching, crystallization using ammonium hydroxide, and calcination at 1000 °C for 60 min, effectively yielded zirconia of 96.32% purity with a recovery of 71.33%. The study explains process optimization that significantly improves the quality of zircon sand and facilitates zirconia production while mitigating the environmental impact of mining tailings.