1-step acidic gold bioleaching by the use of iron and sulfur oxidizing and thiocyanate (SCN) generating microorganisms

传统的低品位硫化金矿提金工艺是先将矿石在低pH条件下堆浸，利用细菌氧化硫化物，然后进行固体洗涤，最后用含氰化液浸出堆，将金浸出成氰化物。由于堆操作中使用氰化物会对环境造成影响，而且硫化物氧化后堆中的pH是酸性的，需要用石灰中和才能将pH提高到氰化金浸出所需的水平，即pH 9.5至10.5，因此该工艺对环境和成本都有不利影响。使用氰化物的石灰成本和环境问题是这一标准工艺的主要挑战。*这里建议在酸性pH下同时进行硫化物氧化和金浸出。在该工艺中，硫化物矿物被普通细菌氧化，但在酸性pH中，硫氰酸盐产生菌被用来生产硫氰酸盐作为浸金剂。该工艺将减少工厂的石灰消耗(整个工艺将在酸性pH下进行)，并将消除氰化物的使用。硫氰酸盐的毒性比氰化物低200倍，因此对黄金回收更具吸引力。通过这个项目，将培养一名博士生。

The conventional gold extraction process from low grade sulphide gold ores is to heap leach the ore at low pH to oxidize sulphides with the help of bacteria, and then wash the solids and finally leach the heap with cyanide containing solution to leach gold into cyanide. The process has environmental and cost disadvantages as the cyanide application in the heap operation has environmental consequences, and also the heap pH is acidic after sulphide oxidation and will require neutralization with lime to increase the pH to the required level for gold cyanide leaching, i.e. pH 9.5 to 10.5. The lime cost and environmental issues of cyanide use are the main challenges with this standard process.****Here it is proposed to do both the sulfide oxidation and gold leaching in acidic pH in one step. In this proposed process, sulfide minerals are oxidized with the usual bacteria, but in addition, thiocyanate producing bacteria are used in the heap to produce thiocyanate as the lixiviant for gold leaching in acidic pH. The process will reduce the lime consumption of the plant (the whole process will be carried out at acidic pH) and will eliminate cyanide use. Thiocyanate is 200x less toxic than cyanide thus making it much more attractive for gold recovery. Through this project a PhD student will be trained.