Investigation of Zn extraction from Kooshk lead- Zinc tailing dam using Geocoat method

In this research work zinc extraction was investigated using Geocoat process from a low grade zinc concentrate produced from the Kooshk Lead- Zinc accumulated flotation tailings. The sample of tailings contained 3. 64% Zn. About 45% sphalerite was recovered by flotation process and zinc content was upgraded to 11. 97%.. The prepared concentrate was coated on the granite grains of 5-10mm، so experiments were conducted in the small column leaching of 0. 5m height. Solution irrigation was done in the close cycle which took 4 days. Collected liqueur was used for next stage irrigation. Results showed that 81% of sphalerite concentrate was dissolved during 10 cycles (40 days) in which solution، Zn concentration reached to 12. 63g/l/. In the same period 40% of pyrite was dissolved during the process. Making continue bioleaching process until 20th cycle indicated more than 90% Zn extraction. Zn extraction rate is significantly higher than Fe extraction until 40 day. Following the bioleaching process، considerable amount of pyrite was dissolved and Fe concentration increased in the leached solution، however، Zn extraction rate decreased and Zn concentration was improved slightly. Analysis of leaching residuals indicated only 0. 67% Zn content. In comparison of Zn content of low grade concentrate (11. 97%)، 91% Zn was dissolved during bioleaching period. Comparing effect of mixed-mesophile bacteria in the bioleaching column and control test (without addition of bacteria) indicated the Zn recovery improvement of 20-25% in presence of added mixed- bacteria.