Heap leaching of gold with in-situ bacterial formation of the leach lixiviant. The case for the bio-formation of (1) cyanide lixiviant, and (2) thiosulfate lixiviant

传统的浸金和提金方法依赖于使用氰化物（或硫代硫酸盐）作为浸金剂。在这个过程中，矿石中的金在氰化物（或高浓度的硫代硫酸盐）溶液中浸出，然后从溶液中回收不纯的金，最后提纯到99.99%的金。氰化物是一种毒性极强的试剂，但它对金的浸出具有高度的选择性，浸出效率非常高。因此，在黄金工业中，用替代浸出剂代替氰化物是非常困难的。然而，向黄金业务运送和处理氰化物盐一直令人关切。 该拟议项目涉及开发一种替代路线，用于在现场产生氰化物，用于浸金，从而消除氰化物在黄金行业中作为“购买试剂”的使用。 在此，提出在金堆浸操作中使用氰化物产生菌来产生氰化物。在黄金堆浸作业中就地形成氰化物，将消除购买氰化物并将其从氰化物生产设施运往世界各地金矿地点的需要。作为第二个目标，拟议的研究还将调查原位生产硫代硫酸盐的选择，硫代硫酸盐是一种非常有吸引力的浸金剂，类似于氰化物。硫代硫酸盐浸金工艺的挑战是硫代硫酸盐试剂的高成本（该工艺需要大量的硫代硫酸盐用于浸金）。在本研究项目中，我们还将研究在金堆浸操作中从硫化矿原位生产硫代硫酸盐的可能性，从而为金浸出提供一种非常低成本的浸出剂。*

The conventional method for gold leaching and extraction relies on the use of cyanide (or thiosulfate) as the gold leaching lixiviant. In this process gold from the ore is leached in a cyanide (or highly concentrated thiosulfate) solution, and later is recovered from the solution as impure gold, and finally purified to 99.99% gold.**Cyanide is known to be an extremely toxic reagent; however, it is highly selective for gold leaching with very attractive leaching efficiency. Thus the replacement of cyanide with alternative lixiviants is very difficult in the gold industry. Nonetheless, the shipping and handling of cyanide salts to the gold operations have always raised concerns. This proposed project pertains to the development of an alternative route for the in-situ generation of cyanide for gold leaching thus eliminating the use of cyanide as a "purchased-reagent" in the gold industry. Herein, it is proposed to use cyanide producing bacteria in gold heap leaching operations to produce cyanide. The in-situ formation of cyanide in the gold heap leaching operations would eliminate the need for the purchase and shipping of cyanide from the cyanide production facilities to the gold mines sites around the world.**As a secondary objective, the proposed research will also investigate the option for the in-situ production of thiosulfate, which is known to be a very attractive lixiviant for gold leaching, similar to cyanide. The challenge with the thiosulfate gold leaching process is the high cost of the thiosulfate reagent (the process requires large volumes of thiosulfate salt for gold leaching). In this research project we will also investigate the possibility of the in-situ thiosulfate production from the sulfide ores in the gold heap leaching operations, thus providing a very low cost lixiviant for gold leaching.****