Soluble Catalysts for Copper Recovery from Low Grade Primary Copper Sulfide Ores

世界上大约80%的铜来自硫化铜矿CuFeS2。通常，黄铜矿被浓缩，然后熔炼以获得高纯度的铜。然而，这些原生铜矿石的品位一直在稳步下降，这使得这条路线对于今天许多低品位的矿石来说不太经济。堆生物浸出是处理低品位铜矿石的一种潜在的低成本替代方法。然而，由于矿物钝化，黄铜矿是出了名的难以浸出，而堆生物浸出的商业应用迄今为止仅限于次级硫化铜（辉铜矿，Cu2S）矿石。低品位黄铜矿的堆生物浸出（结合溶剂萃取和电积）多年来一直是湿法冶金的“圣杯”，有几种方法已经显示出一些希望，包括在热堆中使用极端嗜热微生物，在那里黄铁矿首先被氧化以产生热量，以及使用氯化物作为催化剂。然而，热堆是不可靠的，难以控制，氯化物具有极强的腐蚀性。

Roughly 80% of the world's copper comes from the copper sulfide mineral chalcopyrite, CuFeS2. Typically, chalcopyrite ores are concentrated and subsequently smelted to obtain high purity copper. However, the grades of these primary copper ores have been steadily decreasing, which renders this route less than economical for many of today's low-grade ores. A potential low-cost alternative to process low-grade copper ores is heap bioleaching. However, chalcopyrite is notoriously difficult to leach due to mineral passivation, and commercial application of heap bioleaching has thus far been limited to secondary copper sulfide (chalcocite, Cu2S) ores. Heap bioleaching of low-grade chalcopyrite ores (combined with solvent extraction and electrowinning, or SXEW) has been the “holy grail” of hydrometallurgy for many years, and several methods have shown some promise, including the use of extreme thermophilic microbes in hot heaps where pyrite is first oxidized to generate heat, and the use of chloride as a catalyst. However, hot heaps are unreliable and difficult to control, and chloride is extremely corrosive. Recent work at UBC suggests that it is possible to catalyse the leaching of chalcopyrite with certain soluble species. Electrochemical tests on a chalcopyrite electrode showed that small amounts of a proprietary (albeit inexpensive and readily available) soluble organic compound (which will be referred to as MFD) depassivated the electrode. Preliminary results from column and tank leaching experiments show that MFD is a powerful catalyst in ferric leaching. Adding MFD prevented passivation and enhanced the leaching rate significantly. Also, a column of ore which had stopped leaching began to leach rapidly again upon addition of MFD. These results are very promising. If MFD can depassivate chalcopyrite under heap leaching conditions, then this could render chalcopyrite ores as easy to heap leach as chalcocite ores. This would be a major breakthrough which fundamentally alters the economics of copper mining. The proposed research will focus on developing a viable heap bioleaching process for chalcopyrite ores using MFD. Specific objectives include: 1 Conduct column bioleaching experiments with MFD to determine optimum process conditions 2 Culture iron and sulfur oxidizing bacteria to be resistant to MFD at the levels required 3 Refine analytical methods for measuring MFD concentrations in leach solutions 4 Determine the impact of MFD (if any) on copper SXEW 5 Measure the reaction kinetics of MFD-catalyzed leaching 6 Develop a comprehensive mathematical model of heap bioleaching with MFD 7 Develop a parallel technology for stirred tank bioleaching of chalcopyrite ores and concentrates 8 Determine the fundamental mechanism of the catalytic effect of MFD 9 Test alternative organic compounds which share the same functional groups as MFD 10 Test MFD on other important sulfide minerals