Papers by Keyword: Cyanide

Abstract: Bacteria which are adapted both to high content of toxic compounds and to the environments grow in autochthonous communities of gold heap leach (HL) wastes. In the following study of HL waste from a deposit in the Sakha (Yakutia) Republic (Russia) it was shown that microbial processes had a greater impact on the degradation of cyanides and of complex copper and nickel cyanides, respectively, compared to a chemical degradation. The diversity of bacterial communities growing under natural and model conditions was determined.

Abstract: The ability of neutrophilic bacterium association to destruct thiocyanates and cyanides was found when working with oxidation of elemental and sulphide sulfur in biocake [1]. It was used for microorganisms association selection, which will oxidize thiocyanates and cyanides in liquid CIL tails of Olimpiada gold recovery plant. Originally selection occurred in laboratory reactors in periodical and later in continuous operation with thiocyanate content of 400-500 ml/l. Molasses in concentration of 0,5 g/l used as a source of carbons. After thiocyanates and cyanides stable oxidation in laboratory conditions the process was transferred to larger reactors (capacity of 2,2 m³). As a result of the research, rhodanides concentration reached 1800 mg/l. During the research rhodanides concentration was reduced from 1800 mg/l to 0,02 mg/l and cyanides concentration was reduced from 20 mg/l to 0,01 mg/l. Oxidation took 24 hours. Microbiological researches with application of molecular genetic analysis have shown that in the selected thiocyanate destructive association prevail the following strains: Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Enterobacter.

Abstract: The methods of biodegradation are of special interest because they help solving environmental problems of wastes detoxification from gold-mining operations. The use of bacterial strains is a promising approach in the field of biotechnology to destruct cyanide-bearing compounds. The diversity of microbial communities both in heap in situ and in the enriched cultures was studied with molecular genetic methods. The differences in representation of bacteria, cultivated in unexploitable and operating heaps, are territory, site and heap specific. The strains of Pseudomonas sp. and Methylobacterium sp. possess the biotechnological potential and might be used in biodegradation of heap leaching wastes in extreme continental climate.

Abstract: Gold extraction by cyanidation from refractory gold ores results in the formation of thiocyanate-and cyanide-contaminated wastewater effluents that must be treated before recycle or discard. Activated sludge processes, such as ASTERTM, can be used for biodegradation of these effluent streams. The destruction of these compounds is catalyzed by a mixed microbial culture, however, very little is known about the community composition and metabolic potential of the thiocyanate-and cyanide-degrading microorganisms within the community. Here we describe our on-going attempts to better understand the key microorganisms, within the ASTERTM bioprocess, that contribute to the destruction of thiocyanate and cyanide, and how this knowledge relates to further process optimisation.

Abstract: Cyanide leaching is currently the dominant process used by the mineral industry to extract gold and silver minerals. Cyanide is a nitrogen compound toxic for most living organisms. Many microorganisms are able to tolerate and degrade cyanide and its derivatives. In this study, were considered bacteria from soil and water samples corresponding to a chronological sequence (up to 5 years) of spontaneous cyanide bioremediation in a gold mining area (La Libertad Region, Peru). Culture dependent molecular identifications, based on 16S rDNA amplification and sequencing, were performed for bacteria isolated on agar media. Co-culture dependent molecular identifications were performed through 16S rDNA targeted metagenomics based on Next generation Sequencing with DNA directly extracted from the co-cultures in order to determine bacteria species unable to grow individually on agar media. Culture independent identifications were similarly performed through 16S rDNA targeted metagenomics from DNA directly extracted from water or soil samples in order to establish their respective global microbiota. Concerning cyanide contaminated soils, more than one hundred operational taxonomic units (OTU) were identified by metagenomics with only 30% species co-cultivable in broth medium and 82 isolated strains, in particular Pseudomonas spp. The global microbiota in non-contaminated soils was markedly different. Concerning cyanide contaminated waters, about one hundred operational taxonomic units (OTU) were identified by metagenomics with only 30% species co-cultivable in broth medium. The most frequently identified species belong to Alcaligenes, Alkalibacterium, Bacillus, Paenibacillus and Serratia. Bacteria isolated and co-cultivated from contaminated waters and soils are currently analyzed as candidates for cyanide bioremediation.

Abstract: This paper analyzed the seasonal and vertical variations of cyanide in Jiaozhou Bay, and tried to reveal the transfer processes based on investigation data in different seasons in 1982. Results showed that cyanide contents in surface waters were showing obvious seasonal variations, and were in orders of spring < summer < autumn, due to the inputs of cyanide were mainly occurred in wet season. The vertical variations seem to be not regular, and the influences of cyanide contents in surface waters to bottom waters were not significant, because the degradation of cyanide were rapid in summer and early autumn, leading to most of the cyanide was degraded before or in the process of sedimentation.

Abstract: Purpose The flow injection distillation (zinc acetate solution) was changed to be 5% phosphoric acid in the method of determination of cyanide. Application Cyanide in groundwater was measured by FIA6000 + automatic flow injection analyzer directly. Results In the 2.0-100.0μg/L range, the linear correlation coefficient was greater than 0.9, the recovery was 86.1% -100.8%, relative standard deviation 1.3% -3.8%. Conclusion This method not only reduces the white crystals [Zn (OH)₂] on the pump tube blockage, making the operation more simple and efficient, but also for the detection of a large number of groundwater samples.

Abstract: A laboratory-scale electrolytic cell with a Ti/RuO₂-Pt anode and a Ti cathode was developed to treat high concentration cyanide-contained wastewater. The effects of the different electrode distances, concentration of chlorine anion and current densities, on the CN^- removal were investigated. The results shown the too short and long electrode distance resulted in high energy consumption and low current, the appropriate electrode distance was essential. The CN^- removal was very significant at the electrode distance was 9 cm, and the removal efficiency reached 99.2%. The removal CN^- electrochemical oxidation was mainly attributed the success to in direct oxidation effect of chlorine /hypo-chlorite produced during the electrochemical reaction process. The CN^- removal efficiency increased with increasing the concentration of chloride ion and operating current density. The optimum experimental condition was set at the electrode distance of 9 cm, NaCl dosage of 0.5 g/L, the current density of 10 mA/cm², and pH of 12. At the optimum experimental condition, the CN^- concentration in the solution decreased from 150.33 mg/L to 1.20 mg/L, and the CN^- removal efficiency reached 99.2%.

Abstract: To study the ocean environmental problem, the article analyses and predicts the hydrodynamic feature of study area on the basis of Ecom model. After simulation of the contributed concentration field, the paper assesses the influence of the cyanide in discharge of sewage on the marine water quality nearby. Research shows that the results reflected the rules of transportation and diffusion of pollutants in the tidal water area bitterly.

Abstract: Electronic waste (E-waste) is recognized as a new emerging and fast-growing waste stream, and may be considered as a secondary ore for the recovery of some precious metals (such as gold). A number of control technologies have been conducted for gold recovery, and in which, cyanidation is widely used. In recent years, an alternate approach to the gold cyanidation process is being considered, in which the aim is to replace with the microorganism, specifically cyanogenic bacteria such as Chromobacterium violaceum, Pseudomonas fluorescens, Pseudomonas aeruginosa and Escherichia coli. All these species can produce cyanide ions and dissolve gold in their metabolic processes. The mechanism is a combination of chemical knowledge (interaction of metals and cyanide) with microbiological principles (biological cyanide formation) regarding metal solubilization from waste printed circuit boards and the formation of water-soluble cyanide complexes. And the activity of cyanogenic bacteria is affected by many factors, such as pH, dissolved oxygen pulp density and nutriment, especially several metal ions, which can serve as the catalyst in the metabolism. Now researchers are devoting themselves to looking for the proper conditions, not only from the bacteria themselves, but also the combination of many methods, which can reinforce the cyanide generation and improve gold leaching efficiency. At present the reported leaching efficiency of gold with cyanogenic is approximately 70%. As the continuous optimization of conditions, the industrial application can be expected soon.