VIDEO: Gold cyanidation research at Queen's

Posted on June 05, 2017

How do engineers come up with ways to extract the tiny amounts of gold (typically measured in grams) encased in each tonne of low-grade ore pulled from a mine? One widely used method is a process called cyanidation. Research undertaken by Rina Kim, a post-doctoral fellow with the Robert M. Buchan Department of Mining at Queen’s, aims to ensure gold cyanidation is as efficient and environmentally sustainable as possible. Here's how...

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    Video Transcript:

    Hello, I am Rina Kim in the hydrometalurgy group under the supervision of Professor Ahmad Ghahreman.

    I am studying the effect of oxygen on gold cyanidation especially in the presence of sulfidic ores. In my study, oxygen can give positive effects in two aspects. The first one is oxidation of sulfide minerals in the ore.

    Generally, sulfur and some metal components in the sulfide minerals can give negative effects on gold cyanidation, such as the side reaction concerning leeching chemicals like cyanide the formation of passive film on gold surface and so on. However, once the sulfide minerals are oxidized then the negative effects can be reduced and finally the gold oxidation can be improved.

    Secondly, gold leeching in cyanide solution is an oxidative reaction. So, if we increase the oxygen concentration, the gold cyanidation can be improved, too.

    Additionally, the oxygen can substitute one of the oxidants, the lead, which is currently being used in gold processes. Finally, the environmental problems caused by the use of lead an be reduced.

    To do my study, I'm mainly using the electro-chemical methods such as cyclic voltammetry, chronoamperometry, and Electrochemical quartz crystal microbalance (EQCM).

    In this fume hood I am running the electro-chemical test with cyanide solution and some sulfidic ore slurry and with gold electrodes, another reference electrode and a counter-electrode. In here this gold electrode is leeched by the cyanide solution and the slurry contains some sulfidic minerals and some sulfidic ores so it gives a positive effect or negative effect. At the same time I want to see the effect of oxygen, so I'm injecting oxygen through this tube and we can see some bubbles of oxygen gas.

    All of these electrodes are connected to this potentiostat which measures the potential and current so we can get potential-current curves and another one is by the chronoamperometry we can get the current-time curves. These are the curves acquired by the running test. This curve shows current change over time. So, it shows that this current is decreased by the time because of some of the effects of sulfide minerals in the ore slurry.

    In here, we can see another plot. this is current and potential curve. In this plot there are some current peaks. These peaks shows which potential cuases gold oxidation and how much gold oxidation has occurred. With the height of this current, we can measure the amount of gold oxidation.