中国有色冶金

A low-grade copper sulfide ore was treated by bio-heap leaching-extraction-electrowinning method to produce cathode copper in a Fujian enterprise. The heap leaching process applies a permanent heap operation mode, generating a problem of excess acid and iron. The common practice is to neutralize the low copper raffinate after secondary extraction to a pH 7-8, however, this method reduces the current efficiency due to the high carry-over iron ions in the electrowinning solution, and also generates problems of high neutralization cost and neutralization residue storage. In order to solve the problem of excess acid and iron in bio-heap leaching at source, this paper puts forward the idea of mixing limestone particles into heap leaching ores to increase the content of acid-consuming gangue, and carries out test work with different batches of ores. The effects of limestone content ratio and spray intensity on the extractions of copper and iron, and other parameters were investigated, and the following conclusions were drawn. With the increase of the proportion of limestone ore blending, the acid consumption and the pyrite content in the leaching residue increase, indicating that the limestone can inhibit the leaching of pyrite and reduce the systems external acid production and iron production; increasing the spray intensity is helpful to avoid the drastic change of pH value, thus reducing the hydrolysis precipitation of copper and iron ions and promoting the leaching of copper and iron; limestone blending can maintain the low potential (450~550mV vs. Ag/AgCl) of the leaching system for a long time, and the lower potential helps to inhibit the oxidation of pyrite and reduce the production of external acid and iron.