Gold Reextraction from Cyanide Wastewaters
Development of Technology of Microbiological Gold Reextraction from Cyanide Wastewaters
Tech Area / Field
- CHE-ANL/Analytical Chemistry/Chemistry
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
- ENV-EHS/Environmental Health and Safety/Environment
- ENV-WPC/Water Pollution and Control/Environment
- MAN-MPS/Manufacturing, Planning, Processing and Control/Manufacturing Technology
- MAN-PDM/Plant Design and Maintenance/Manufacturing Technology
3 Approved without Funding
National Academy of Sciences of Kyrgyzstan / Institute of Chemistry and Chemical Technology, Kyrgyzstan, Bishkek
- Laurentian University, Canada, ON, Sudbury\nUniversity of Alberta / Earth and Atmospheric Sciences Department, Canada, AB, Edmonton
Project summaryKyrgyzstan is the gold-extracting country. The total gold resources of Kyrgyzstan make up 2.5-3 thousand tons according to assessment of different authors. The following deposits of gold stoсk may be distinguished:
- unique ones – more than 732t (Kumtor)
- large ones – more than 70t (Jerui, Taldybulak Levoberejniy)
- middle ones –30-70t (Makmal, Bozymchak, Unkurtash, Ishtamberdy, Altyn-Jilga, Nichke-Suu, Tahtazan)
- small ones- 5-30t (Solton-Sary, Jamgur, Terek, Perevalnoe, Terekkan).
There are two acting gold-extracting enterprises (Kumtor, Makmal) in Kyrgyz Republic. The exploitation of new deposits is planned. All of them are in need of effective and ecologically safe technologies of gold extraction. The method of microbiological gold reextraction by active biomass from cyanide wastewaters seems to be quite perspective.
At present gold is extracted by cyanide method that inevitably leads to cyanide wastewaters accumulation in tail-storages of gold extracting factories (GEF). For instance, only at “Makmalzoloto” GEF the tail-storage volume makes up 44849455.7 cubic meters (7128700 tons of cyanide sewage). The pulp thrown makes up 2740.74 cubic meters per day. At Kumtor deposit the tail-storage volume makes up 110mln cubic meters. Taking into account fact, that all Kyrgyzstan deposits are high in the mountains and Kyrgyzstan itself is located in the high seismic zone, the large probability of ecological catastrophe for whole Central Asia exists in the case of tail-storages damage and cyanide getting into reservoirs. For ecological catastrophe preventing it is necessary to develop effective and ecologically friendly technologies of gold reextraction. The idea of present project appeared in 2005 after completion of ISTC Project #KR-556 («The Microbiological Methods for Decontamination of Wastewaters from Gold-Extracting Factories of Kyrgyzstan: Environmental Aspect»). The result of testing strains destructors of cyanides and thyocyanates on industrial sewage of “Makmalzoloto”GEF was served as reason. Particular interest was caused by fact that gold content in cyanide wastewaters was also decreased from 2mg/l to 0.019mg/l (99.5%) (see Technical Report on # KR – 556 Project). This certifies that except of cyanide utilization by microbiological method it is possible to conduct simultaneously gold reextraction from industrial wastewaters. That time to study the extraction mechanism of gold was impossible for following objective reasons:
- project was actually completed
- project did not set gold reextraction as an object
- research group did not have necessary equipment (atomic-absorptional analyzer).
The possibility of combining technology of industrial waters decontamination from cyanides with technology of additional gold extraction interested commercial structures of Kyrgyzstan (as “Kyrgyzaltyn” Open Joint Stock Society). However, for this it is necessary to study in details mechanism of noble metals reextraction from cyanide GEF wastewaters with microflora. Just this mechanism will determine the technology of gold extraction and stipulate the profitability of this technology. It is known from literature that at using microbiological method, not only dissolved gold, but also colloid state gold is reextracted. For instance “Advanced Mineral Technology” (USA) developed the technology of extraction of metals microquantities from wastewaters using active biomass of Aspergillus niger fungi as sorbent. The total contents of gold and silver in burnt biomass rests reached 20%. Some other technologies of gold reextraction from GEF cyanide wastewaters are also known.
Project purpose: Developing new ecologically safe microbiological method of gold reextraction from cyanide industrial waters with simultaneous decontamination from cyanides.
- Ensure ecological purity of Kyrgyzstan natural medium in expense of cyanide decontamination in industrial GEF waters
- Develop technology of increasing gold manufacture in expense of cutting down its loss in waste
- Create the bank of technogenic microorganisms perspective for biohydrometallurgy.
Executors of the Project will be weapon specialists and research workers of National Academy of Sciences of Kyrgyz Republic.