Metal recovery from stibnite tailings: Chemical and hybrid leaching applications

The production of mine tailings continues to increase worldwide, particularly in Turkey, as a result of the growing demand for raw materials and the depletion of high-grade deposits. Simply storing them in tailings dams can lead to environmental problems. This research investigated recovery of critical metals such as antimony (Sb) and arsenic (As) from stibnite flotation tailings from Halıköy/Ödemiş/İzmir/Türkiye antimony plant Hydro/biohydrometallurgical processes were tested. A single stage leaching process under optimum conditions of 25% solid ratio, 4.4M HCl, 0.5M NaNO3, 70°C and 400 rpm for 1 hour gave recoveries of Sb, As and Fe of 99.7%, 97.5% and 97% respectively in a 1 L reactor test. Under the same conditions, the semi-pilot process achieved Sb 98.3%, As 92% and Fe 98%. A co-precipitation process using 1M NaOH recovered about 100% Sb and 99% Fe within 30 min at pH 1 and 70°C. Using the same solid ratio of 25%, the optimum parameters in the first leaching step of a selective leaching process were 0.97M Na2S, 2.5M NaOH, 300 rpm, 70°C for 1 hour. Under these conditions, 99.13% of Sb and 61.5% of As were recovered in the 1L reactor compared to 97.00% and 50.30% in the pilot scale. By applying a second leaching test on the residue of the first step under the same solid ratio of 25%, the optimum parameters were 0.25M oxalic acid, 1M HNO3 400 rpm at 90°C for 1hour. The Fe and As recoveries were 97% and 100% and then 96% and 87% for the 1L reactor and semi-pilot leaching stages respectively. The Sb precipitation efficiency after the first process reached 99% using a ratio of 5/1 pregnant leach solution/H2O2 at 30°C, 300 rpm for 2 hours. The precipitation of Fe after the second process with 1M NaOH at pH 7, 90°C, 300 rpm for 1 hour was also 99%. The application of the one-step and two-step bioleaching processes led to the achievement of Sb leaching efficiencies of 12% and 13%, respectively. The techno-economic evaluation of the two hydrometallurgical processes using the SuperPro designer software showed that using of a single leaching stage in an acidic environment is economic.