The bacterial leaching of chalcopyrite ore coming from Albania

This experimental work was carried out in the framework of the S&T Cooperation Programme between Italy and Albania (years 2001-2003): the aim was to carried out a feasibility study, in laboratory step, with the main objective to realize an economical process for copper recovery by bacterial leaching. In Albania there are many cooper ore mines that worked from 1940 to 1999. Now cooper industry is not working, because of old and inefficient technology. At the same time about 30 million tons of sulfide cooper ore, with average content of copper over 1% Cu, have been discovered in North-East of Albania. Chalcopyrite ore samples coming from North-East of Albania, have been analysed. Quartz, ferrous clinochlore IIB, calcite, chalcopyrite and pyrite have been determined by X-Ray diffraction technique, while quantitative chemical analysis of the metals has been carried out by ICP 0ES. A mixed culture of microbial strains of Thiobacillus sp. was selected from Italian sulphuric waters. This organism is able to oxidize sulphide minerals such as chalcopyrite, pyrite, phyrrotite, stibnite, and arsenopyrite. Main experimental conditions investigated for bioleaching tests were: stirring rate, particle size, pH, pulp density, temperature. This investigation was realised by plan of factorial experiments. A systematic ANOVA by Yates's Method was used in the interpretation of the experimental results. The technical feasibility of the bioleaching process was demonstrated; in fact, about 85-90% Cu dissolution has been bioleached. An economical analysis will be necessary to understand when the bioleaching may be an effective alternative to conventional process.