Date

2017

Author

Büyüktanır, Karden

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In this work, the possibility of gold extraction using cyanide leaching from a refractory type gold ore, particularly rich in arsenic minerals of realgar and orpiment, was assessed. In this regard, the effectiveness of the cyanide leaching process on the ore was determined using bottle-roll leaching tests with respect to cyanide amount, cyanidation period, and particle size. In the study, Bottle Roll Tests were carried out at first in order to determine cyanide consumption tendency of the ore, with an ore with the particle size of 150 µm (P100), by using solutions containing NaCN in the amounts of 500, 1000, 1500 and 2000 ppm. As a result of the tests, it was decided to proceed to the 2nd stage, at which amenability of the ore to cyanide leaching was determined with solutions containing 1500 ppm of NaCN. At the 2nd stage, Bottle Roll Tests were conducted on samples with the particle size of 150, 106, 73, 57, 37 µm (P100), and the leaching behavior of the gold ore and the total amount of NaCN that it consumed during leaching were determined. In the tests performed, it was determined that the ore has a highly refractory structure containing high amounts of cyanicide. It was determined that Au extraction yield increases as the particle size decreases; however, consumption of NaCN increases with the increasing yield efficiency. When the particle size was decreased to 37 µm from 150 µm, Au extraction yield increased to 71.1% from 37.5%, and the total consumption of NaCN per ton of ore increased to 8.8 kg from 5.6 kg. A higher consumption of NaCN with the P100 of 37 µm and an Au extraction yield around 70% revealed the fact that the ore should be pre-treated before cyanide leaching. At the 3rd stage of the study, the leaching behavior of the samples which were pre-treated with roasting was examined. Through roasting, it was intended to rehabilitate refractory characteristic of the ore, increase its amenability to cyanide leaching, and decrease activity of cyanicides which lead to a higher consumption of cyanide. Within this scope, the behavior of gold ore in oxidizing thermal environment (0-1000 ºC) was determined at first through thermogravimetric analyses (TGA); and having regard to the obtained TGA profiles, it was decided to perform the ore roasting process at 400 ºC and higher temperatures. Bottle roll tests were carried out on the ore samples with a particle size of 150 µm (P100) and roasted at different temperatures (550, 650 and 750 ºC) for different periods (30, 60 and 90 minutes); and after such pre-treatment, Au extraction from the ore and NaCN consumption were determined. After the roasting process performed at 750 ºC for a period of 90 minutes, an Au extraction yield around 70% was obtained with a NaCN consumption of 3.7 kg per ton of ore. It revealed that Au extraction yield, which can be obtained only with a fine particle size of 37 µm without the roasting treatment, can be obtained with a much larger size (150 µm) and a much lower consumption of NaCN after the pre-treatment. As a result of the tests, the optimum roasting conditions for gold ore were determined as 650 ºC temperature and a roasting period of 60 minutes.  

Subject Keywords

Gold ores., Leaching., Cyanides., Sodium cyanide.

URI

http://etd.lib.metu.edu.tr/upload/12620770/index.pdf
https://hdl.handle.net/11511/26280

Collections

Graduate School of Natural and Applied Sciences, Thesis