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Abstract

Biological treatment is a proven process for the treatment of mining effluents such as tailings, wastewaters, acidic mine drainage etc. Several bacterial species (Pseudomonas sp.) can effectively degrade cyanide into less toxic products. During metabolism, they use cyanide as a nitrogen and carbon source converting it to ammonia and carbonate, if appropriate conditions are maintained. In this study, nine strains of Pseudomonas sp. were isolated and identified from a copper mine. Two (CM5 and CMN2) of the nine bacteria strains were used in a cyanide solution. Some important parameters in the biological treatment process were tested and controlled: pH, cell population and CN− concentration. Tests were conducted to determine the effect of the type of bacterial strains on the treatment of cyanide. Laboratory results indicated that biological treatment with Pseudomonas sp. might be competitive with other chemical treatment processes. This paper presents the results of an investigation of a biological treatment system for cyanide degradation in a laboratory batch process.

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... Generally, free cyanide originates from both anthropogenic and natural processes [6]. The anthropogenic sources of cyanide range from effluents discharged from municipal wastewater treatment plants, agricultural run-off, mining activities and electroplating industries [7,8], including the application of some cyanide containing insecticides in the agricultural industry, which culminates in environmental contamination [9]. Cyanides and CGs have also been generated in plants and agricultural produce such as Manihot esculenta (cassava), with the waste generated through processing of such produce contributing to the cyanide load into the environment. ...
... Furthermore, other biological treatments for free cyanide involve microorganisms; these organisms are known to be toxin producers and are organisms, such as Pseudomonas sp., Nocardia sp., Flavobacterium sp., Bdellovibrio sp., as well as nitrifiers, such as Nitrosomonas sp., Nitrobacter sp., Sphingomonas sp., Exophiala sp., Bacillus sp., and fungi such as Aspergillus sp. and Penicillium sp. [4,8,22,[26][27][28]. Among these microorganisms, Aspergillus sp. and Penicillium sp. are the most prevalent species able to grow successfully in stringent weather conditions, with some, including Cunninghamella sp. ...
... The focus of this review is that cassava can be toxic when consumed in large quantities owing to its cyanogen content [49]. The prolonged consumption of cassava in different forms can be harmful for humans in particular, owing to inadequacies in post-harvest treatment techniques [8,21]. For instance, studies on cassava-cyanide effects in humans revealed that a permanent consumption of low-level concentrations of cyanide from poorly processed cassava could result in goitres and Tropical Ataxic Neuropathy (TAN) [24,59], whereas a high consumption of the produce could result in neurological disorders, such as konzo [23,50]. ...
Chapter
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Cyanogens and mycotoxins are vital in protecting flora against predation. Nevertheless, their increased concentrations and by-products in agricultural soil could result in produce contamination and decreased crop yield and soil productivity. When exposed to unsuitable weather conditions, agricultural produce such as cassava is susceptible to bacterial and fungal attack, culminating in spoilage, particularly in arid and semi-arid regions, and contributing to cyanogen and mycotoxins loading of the arable land. The movement of cyanogen including mycotoxins in such soil can result in sub-surface and/ or groundwater contamination, thus deteriorating the soil’s environmental health and negatively affecting wildlife and humans. Persistent cyanogen and mycotoxins loading into agricultural soil changes its physico-chemical characteristics and biotic parameters. These contaminants and their biodegradation by-products can be dispersed from soil’s surface and sub-surface to groundwater systems by permeation and percolation through the upper soil layer into underground water reservoirs, which can result in their exposure to humans and wildlife. Thus, an assessment and monitoring of cyanogen and mycotoxins loading impacts on arable land and groundwater in communities with minimal resources should be done. Overall, these toxicants impacts on agricultural soil’s biotic community, affect soil’s aggregates, functionality and lead to the soil’s low productivity, cross-contamination of fresh agricultural produce.
... The highly toxic compound, cyanide, is often used in several industrial processes comprising photo finishing, metal plating, coal washing, synthetic fiber production and the processing of gold and silver, all of which contribute to serious environmental problems [1][2][3][4][5]. ...
... Many of these species are capable of using cyanide as a sole source of carbon or nitrogen. Up to now, several bacterial, fungal and algal species such as, Pseudomonas, Rhodococcus, Klebsiella, Bacillus, Citrobacter, Stemphylium loti, Aspergillus niger, Trichoderma spp., Chlorella sp., Arthrospira maxima, Chroococcus, Bacillus pumilus and etc., have been effectively used to biologically degrade cyanide [1,[16][17][18][19][20][21][22][23]. In all previous researches, not only the capability of microbes for cyanide degradation was evaluated, but also the rate at which cyanide can be degraded was also considered as an important and critical aspect of such biological processes. ...
... In all previous researches, not only the capability of microbes for cyanide degradation was evaluated, but also the rate at which cyanide can be degraded was also considered as an important and critical aspect of such biological processes. Due to the environmental significance of cyanide biodegradation methods, many researchers have attempted to accelerate the rate of the biological reaction and degradation of cyanide by using a combination of various methods, or by altering the relevant environmental conditions of the biological reaction [1,7,[24][25][26][27]. The electrochemical and biological degradation of cyanide represents an attractive and effective approach due to the degradation achieved and eco-environmental compatibility, but without the generation of secondary pollutants [28]. ...
Article
Background: Electro-biodegradation is a novel technique for cyanide degradation in aqueous solutions. Many physical, chemical, and biological methods have been developed and used to treat cyanide degradation. The biological methods are more environmentally-friendly and economically cost-effective when compared to other techniques, however, the process reaction time period is much longer and the efficiency is lower. Methods: In this research, the bacterial strain, Bacillus pumilus ATCC 7061, was tested for the first time to introduce the Cyanide Electro-biodegradation technique. By using a direct current power supply, electrons were generated in an electro-biodegradation cell containing culture media at free cyanide concentrations of 100 to 500 mg/l, under alkaline conditions. Results: Experimental tests showed that when electrons were added and bacteria were inoculated into the aqueous media containing 100, 200, 300, 400 and 500 mg/l of free cyanide, the cyanide degradation efficiency increased from 16.2, 21.6, 29.5, 38.7 and 44.5% to 98.6, 99.3, 99.7, 99.8 and 99.7%, in 36, 72, 137, 233 and 301 h, respectively. The results show that by adding electrons, the process reaction time decreases and cyanide degradation efficiency increases significantly. Conclusions: The results presented here demonstrate for the first time the importance and the significance of the electro-biodegradation technique in the efficient degradation and removal of cyanide present in aqueous solutions.
... The various species of cyanide remain in tails streams from gold plants, on some operations the waste streams are processed through a detoxification process prior to tails deposition [11]. This reduces the concentrations of these cyanide compounds, but does not completely eliminate them from the stream. ...
... One teaspoon of a 2% cyanide solution can kill a person. Regulatory documents often state that cyanide in water rapidly breaks down in the presence of sunlight into largely harmless substances, such as carbon dioxide and nitrate or ammonia [11]. Cyanide also tends to react readily with many other chemical elements and is known to form, at a minimum, hundreds of different compounds. ...
Conference Paper
Cyanide is any chemical compound that contains monovalent combining group of carbon and nitrogen (CN). It breaks down some group of heavy metals resulting in the formation of complexes with such metals. The complexes that are formed are usually very stable even under mildly acidic conditions.Cyanide has been preferred in gold and silver mining worldwide, but its potential toxicity and environmental impact has been of health concern.Although cyanide can be recovered or degraded by several processes, it is still widely discussed and examined. Biological treatment of cyanide is a well-established environmental friendly alternative and has been commercially used at gold mining operations to complement the existing physical and chemical processes. Biological treatment techniques facilitate growth of microorganisms that are essential for the treatment procedures. The present study describes the environmental challenges of cyanide in the mining industry and provided an alternative use of biological processes to treat the chemical.
... Biological treatment is able to simultaneously remove several compounds in a single process, therefore producing high-quality effluent often of an attribute suitable for direct discharge to surface water, thus making it an attractive alternative in comparison to conventional cyanide removing methods ( Botz et al., 2005). In addition, biological treatment had the ability to attain cyanide removal efficiency equivalent to those obtained through chemical or physical treatment under optimal conditions as reported in the literature ( Akcil et al., 2003). The superiority of biological methods is reflected in the increasing number of operating treatment plants in the United States and Canada which proved that the commercial applications of biodegradation processes can be implemented successfully to detoxify cyanide (Akcil, 2003). ...
... Rhodococcus UKMP-5M 11 nitrite, an intermediate, followed by the rapid second oxidation to nitrate as shown in Equations 1 and 2 ( Akcil et al., 2003). ...
Chapter
This book provides an overview of biodegradation. The first chapter provides a detailed description on the ability of Rhodococcus UKMP-5M to act as a biological tool to remediate phenol, chlorinated compounds, nitrile, oil spillage and cyanide which selection was primarily based on their large-scale presence in industrial wastewater. Chapter Two presents advances made in recent decades on the understanding of the metabolic capabilities of sulfate reducing bacteria (SRB) from marine and other types of sediment (i.e., freshwater, estuarine) for the biotransformation of carbon compounds and sulfate that are present as pollutants in several types of waters and soils. Chapter Three concentrates on the different parameters that influence biodegradation speed and energy release potential. Chapter Four reports and discusses several examples on biodegradation with bacteria and fungi of organochlorides, organophosphates, and more recently of pyrethroid pesticides. Chapter Five discusses heavy metals as biodegradation inhibitors of the forest litter in contaminated areas. Chapter Six introduces ecologically feasible ways of treating environments contaminated by BTEX (a mixture of benzene, toluene, ethylbenzene and xylene) based on efficient microbial metabolism.
... Chemical treatment of cyanide removal from environment are very expensive and generate toxic products, therefore, cyanide biodegradation can be an alternative and eco-friendly treatment. Bacteria such as Rhodococcus sp. and Nocardia sp; fungi such as Fusarium sp. and Aspergillus sp; algae such as Arthrospira maxima and Scenedesmus obliquus, possess enzymatic mechanisms to detoxify and bioremediate free cyanide and other cyanide complexes [121,122] . Kunz et al. [123] have discussed the mechanism of cyanide degradation by bacterial strain Pseudomonas fluorescens NCIMB 11764 by releasing of pyruvate and 2-oxoglutarate to the medium, and formation of their cyanohydrins via cyanide oxygenase enzyme. ...
Chapter
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Ever-increasing urbanization and industrialization are responsible for intensifying different pollutants in the environment. Biotechnology provides many solutions to combat these pollutants. Biotechnology involving potential of microbes is offering remediation of wide array of pollutants (viz. heavy metals, organic wastewater and solid wastes, radionuclides, polycyclic aromatic hydrocarbons, explosives, dioxins, etc.). Microbes-based biotechnological applications are focusing on improving their inherent capabilities and mechanisms to deal with different pollutants for their further decontamination. Bioaugmentation and biostimulation are the two prime process of biotechnology-based bioremediation. Recently, advanced biotechnology applications, like DNA microarray, environmental biosensors, metagenomics, proteomics, etc., have been applied in the field of environmental pollution.
... Bacterial consortia able to use metal-bound cyanides as nitrogen source, including copper and zinc complexes has been described and used in detoxification of cyanide from electroplating wastewater [5,6]. Several Pseudomonas species isolated from a copper mine have been also reported to degrade efficiently cyanide [53]. Detoxification of cyanide from industrial effluents is not restricted to bacterial strains, and fungi or algae like Scenedesmus obliquus have been used with this purpose [54,55]. ...
Article
Full-text available
Biological treatments to degrade cyanide are a powerful technology for cyanide removal from industrial wastewaters. It has been previously demonstrated that the alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 is able to use free cyanide and several metal−cyanide complexes as the sole nitrogen source. In this work, the strain CECT5344 has been used for detoxification of the different chemical forms of cyanide that are present in alkaline wastewaters from the jewelry industry. This liquid residue also contains large concentrations of metals like iron, copper and zinc, making this wastewater even more toxic. To elucidate the molecular mechanisms involved in the bioremediation process, a quantitative proteomic analysis by LC-MS/MS has been carried out in P. pseudoalcaligenes CECT5344 cells grown with the jewelry residue as sole nitrogen source. Different proteins related to cyanide and cyanate assimilation, as well as other proteins involved in transport and resistance to metals were induced by the cyanide-containing jewelry residue. GntR-like regulatory proteins were also induced by this industrial residue and mutational analysis revealed that GntR-like regulatory proteins may play a role in the regulation of cyanide assimilation in P. pseudoalcaligenes CECT5344. The strain CECT5344 has been used in a batch reactor to remove at pH 9 the different forms of cyanide present in industrial wastewaters from the jewelry industry (0.3 g/L, ca. 12 mM total cyanide, including both free cyanide and metal−cyanide complexes). This is the first report describing the biological removal at alkaline pH of such as elevated concentration of cyanide present in a heterogeneous mixture from an industrial source.
... 22 Metabolism of phenol and cyanide in mono component systems by strains of Acinetobacter, Bacillus, and Pseudomonas has been explored. [23][24][25] The intent of this research was to optimise the process parameters with an integrated technique by adsorption using spent tea activated carbon (STAC-C) and biodegradation using the bacterial species A. faecalis JF339228 accompanied with immobilisation for the eradication of phenol and cyanide existing in a binary system. Because adsorption technique is supplementary to biodegradation where the microbial mass consumes the matter as well as decomposes them. ...
Article
The current study is designed for the eradication of phenol and cyanide from a simulated binary mixture involving acetic acid modified spent tea activated carbon (STAC‐C), isolated bacterial strain Alcaligenes faecalis JF339228, and immobilized A. faecalis JF339228 onto spent tea biochar by an amalgamated approach of sorption coupled with biodegradation. Characterisation of the biosorbent was ascertained by field emission scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The viability for eco‐benign expulsion of the pernicious pollutants, and the resultant compounds after treatment was examined by fluorescence and UV‐visible spectrophotometry with comprehensive elucidation of the interactions with DNA. Gas chromatography–mass spectrometry (GC‐MS) anatomization was conducted for the evaluation of degraded derivatives post‐treatment. The chemical and structural analysis of the degraded compounds and its impact upon disposal on the basis of degree of toxicity and reactivity were evaluated using TOXTREE software. Batch studies were implemented for the evaluation of process parameters like pH, reaction time, biosorbent or inoculum dosage, initial concentration, and temperature. Mono and binary component isotherm modelling was executed. Immobilised cells and free cells could accomplish better removal efficacy of 94.71% and 92.25% for cyanide, respectively, whereas adsorption using STAC‐C was responsible for maximum removal of phenol up to 86.29%.
... Aside from the acidophilic mesophilic species known to be involved in bio oxidation of gold, diverse metallophilic Gram positive and negative bacteria belonging to the phylum Proteobacteria such as Pseudomonas, Aeromonas, Shewanella, Brevundimonas, Agrobacterium and Acinetobacter and the phylum Firmicutes (Bacillus, Serratia, and Exiguobacterium) and so on have been reported in gold mine tailings using culture-dependent techniques [30][31][32][33]. A number of studies also investigated bacterial diversity in gold mines using culture independent techniques based on bacterial 16SrRNA gene identification. ...
Article
Full-text available
Mining activities can lead to the generation of large quantities of heavy metal laden wastes which are released in an uncontrolled manner, causing widespread contamination of the ecosystem. Though some heavy metals classified as essential are important for normal life physiological processes, higher concentrations above stipulated levels have deleterious effects on human health and biota. Bacteria able to withstand high concentrations of these heavy metals are found in the environment as a result of various inherent biochemical, physiological, and/or genetic mechanisms. These mechanisms can serve as potential tools for bioremediation of heavy metal polluted sites. This review focuses on the effects of heavy metal wastes generated from gold mining activities on the environment and the various mechanisms used by bacteria to counteract the effect of these heavy metals in their immediate environment.
... Considering this fact, alkalophilic microorganisms should be required to remove cyanide efficiently from contaminated areas and wastewaters. These cyanide-containing residues need to be treated to reduce their toxicity, but physical-chemical treatments have not been demonstrated to be very efficient and, therefore bioremediation processes constitute a potent alternative to decontaminate industrial cyanide-containing residues [14,15,16]. ...
Article
Full-text available
The alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 uses free cyanide and several metal−cyanide complexes as the sole nitrogen source and tolerates high concentrations of metals like copper, zinc and iron, which are present in the jewelry wastewaters. To understand deeply the regulatory mechanisms involved in the transcriptional regulation of cyanide-containing wastewaters detoxification by P. pseudoalcaligenes CECT5344, RNA-Seq has been performed from cells cultured with a cyanide-containing jewelry wastewater, sodium cyanide or ammonium chloride as the sole nitrogen source. Small RNAs (sRNAs) that may have potential regulatory functions under cyanotrophic conditions were identified. In total 20 sRNAs were identified to be differentially expressed when compared the jewelry residue versus ammonium as nitrogen source, 16 of which could be amplified successfully by RT-PCR. As predicted targets of these 16 sRNAs were several components of the nit1C gene cluster encoding the nitrilase NitC essential for cyanide assimilation, the cioAB gene cluster that codes for the cyanide-insensitive cytochrome bd-type terminal oxidase, the medium length-polyhydroxyalkanoates (ml-PHAs) gene cluster, and gene clusters related with a global nitrogen limitation response like those coding for glutamine synthase and urease. Other targets were non-clustered genes (or their products) involved in metal resistance and iron acquisition, such as metal extrusion systems and the ferric uptake regulatory (Fur) protein, and a GntR-like regulatory family member probably involved in the regulation of the cyanide assimilation process in the strain CECT5344. Induction of genes targeted by sRNAs in the jewelry residue was demonstrated by qRT-PCR.
... Cyanide degrading enzymes are generally produced by mesophilic microorganisms. The biodegradation rate of cyanide is temperature dependent as these micro-organisms are generally isolated from soil and work efficiently with temperature typically ranging between 20 and 40 °C (Akcil, Karahan, Ciftci, & Sagdic, 2003;Baxter & Cummings, 2006a;Kao et al., 2003;Ubalua, 2010). The effect of pH (a master variable) specifically on the bioremediation of cyanide-contaminated soil is significant. ...
Article
Full-text available
Mining industry has been using cyanide for more than ten decades to recover precious metals such as gold and silver. The presence of cyanide in the environment has long been a matter of concern due to its high toxicity to human, animal, and aquatic life. The available treatment processes either physical or chemical are suffered with issues such as operating conditions, generation of secondary pollution, and lack of cost effectiveness. A number of micro-organisms are capable to consume cyanide as a source of carbon and nitrogen, and convert it into ammonia and carbonate. Some plants are also efficient in cyanide attenuation process. Bioremediation of cyanide might be an efficient, cost-effective, eco-friendly, and an attractive alternative to the conventional physical and chemical processes. This paper reviews the recent advances in remediation of cyanide contaminated tailings via micro-organisms and plants. Aspects such as speciation, toxicity, source, and degradation mechanisms of cyanide are discussed. Factors affecting functioning of micro-organisms and plants as bioremediation agents are also highlighted.
... Due to the high concentrations of heavy metals usually present in Au mine tailings, any bacterial species present in the tailings is likely to have the ability to survive high heavy metal concentrations. Acidophilic and mesophilic species such as Acidithiobacillus spp., Pseudomonas, Aeromonas, Shewanella, Brevundimonas, Agrobacterium, Acinetobacter Bacillus, Serratia, and Exiguobacterium have been reported in gold mine tailings (Akcil et al. 2003;Anderson and Cook 2004;Fashola et al. 2015;Wei et al. 2009). These bacterial species could present a possible solution to the remediation of heavy metal contaminated environments through bioaugmentation. ...
Article
Full-text available
Chemical precipitation, oxidation/reduction, filtration, ion-exchange, reverse osmosis, membrane technology, evaporation and electrochemical treatment as remediation technologies have various shortcomings which have fueled the search for more environmentally friendly and cost-effective methods of remediating heavy metal contaminated environments. Indigenous bacteria in heavy metal contaminated sites present a possible solution to this concern. This study assessed the potential of indigenous heavy metal resistant bacteria as immobilization agents of Pb, Ni and Zn in Au mine tailings. Tailings from three abandoned Au mining environments; mine tailings A (MA), mine tailings B (MB), and Tudor shaft (TS) were collected and indigenous heavy metal resistant bacteria present in the tailings isolated. The isolated bacteria OMF 532 (E. asburiae) and OMF 003 (B. cereus) were used in bioaugmenting Ni-, Pb- and Zn-spiked tailings to determine the potential of the isolates to immobilize these metals. The immobilization potential of the isolates as determined by the difference in metal mobility in the tailings samples before and after bioaugmentation was used to assess the immobilization potential of the bacterial isolates. Mobility factor (MF) of Ni in the samples was reduced from 16.4 to 6.2, and 17.6 to 7.4 in MB and MA, respectively, reflecting a 35% decrease in Ni mobility. Lead and Zn mobility in the samples also showed a decrease of 90% and 60%, respectively, after bioaugmentation. Though MF values for Ni, Pb and Zn in the TS samples indicated low level of mobility of these elements at the site, bioaugmentation further reduced their mobility by 25–35% for Ni, 95% for Pb, and 10–30% for Zn. The results of this study show that indigenous bacteria in the tailings have the potential to reduce the bioavailable fractions of the three metals studied in the mine tailing and could be further exploited in heavy metal remediation of the sites.
... Considering the drawbacks offered by the above systems, bioremediation provides a complete socioeconomic sustainable solution by mineralizing the toxic organics into eco-benign secondary intermediates. 13 Some of the major phenol and cyanide degrading organisms as reported include Pseudomonas sp., 14,15 Escherichia coli, 16 Acinetobacter sp., Serretia odoriferra MTCC 5700, Bacillus sp., 17,18 and etc. However, the drawbacks of suspension cultures like handling of high effluent and cell concentration, expensive cell recovery and reuse, and washout of cells can be eliminated by the adoption of immobilization technique, which restricts the mobility of cells within a defined area. ...
Article
Coke oven sectors dispense phenol and cyanide into the circumferential ecosystem, which becomes a serious concern to the subsistence of the flora and fauna. The current study investigates phenol–cyanide treatment using carbon alginate beads immobilized with mixed bacterial consortium. Response surface using central composite design was contrived for the batch and packed bed bio‐column optimization study. The optimal removal conditions obtained in batch study were 89.77% and 82.33% for phenol and cyanide, respectively, with 10‐g/L adsorbent dosage, time 2 hr, and particle diameter 0.3 cm, whereas 87.22% and 90.97% with 22‐cm column height, column diameter 3 cm, 10‐ml/min flow rate, and 1‐hr operation time. The actual exposure time of the pollutants in the bio‐column reactor was calculated to be 22.15 min. Analysis of variance and model statistics predicted a high coefficient of determination for column operation with R2 = .9950 (phenol), R2 = .9976 (cyanide), and p values < .0001 stating significant model. The quantitative estimation of the combined external mass transfer and biodegradation effect was performed to evaluate correlation as (phenol) and (cyanide) with km = 0.052 and km = 0.055 cm/hr, respectively. The surface morphological study was executed by field emission scanning electron microscopy and Brunauer–Emmett–Teller surface area analysis depicting bacterial film development on the porous carbon matrix for effective treatment of binary system.
... Due to the high concentrations of heavy metals usually present in Au mine tailings, any bacterial species present in the tailings is likely to have the ability to survive high heavy metal concentrations. Acidophilic and mesophilic species such as Acidithiobacillus spp., Pseudomonas, Aeromonas, Shewanella, Brevundimonas, Agrobacterium, Acinetobacter Bacillus, Serratia, and Exiguobacterium have been reported in gold mine tailings (Akcil et al. 2003;Anderson and Cook 2004;Fashola et al. 2015;Wei et al. 2009). These bacterial species could present a possible solution to the remediation of heavy metal contaminated environments through bioaugmentation. ...
Article
Full-text available
Chemical precipitation, oxidation/reduction, filtration, ion-exchange, reverse osmosis, membrane technology, evaporation and electrochemical treatment as remediation technologies have various shortcomings which have fueled the search for more environmentally friendly and cost-effective methods of remediating heavy metal contaminated environments. Indigenous bacteria in heavy metal contaminated sites present a possible solution to this concern. This study assessed the potential of indigenous heavy metal resistant bacteria as immobilization agents of Pb, Ni and Zn in Au mine tailings. Tailings from three abandoned Au mining environments; mine tailings A (MA), mine tailings B (MB), and Tudor shaft (TS) were collected and indigenous heavy metal resistant bacteria present in the tailings isolated. The isolated bacteria OMF 532 (E. asburiae) and OMF 003 (B. cereus) were used in bioaugmenting Ni-, Pb-and Zn-spiked tailings to determine the potential of the isolates to immobilize these metals. The immobilization potential of the isolates as determined by the difference in metal mobility in the tailings samples before and after bioaugmentation was used to assess the immobilization potential of the bacterial isolates. Mobility factor (MF) of Ni in the samples was reduced from 16.4 to 6.2, and 17.6 to 7.4 in MB and MA, respectively, reflecting a 35% decrease in Ni mobility. Lead and Zn mobility in the samples also showed a decrease of 90% and 60%, respectively, after bioaugmentation. Though MF values for Ni, Pb and Zn in the TS samples indicated low level of mobility of these elements at the site, bioaugmentation further reduced their mobility by 25-35% for Ni, 95% for Pb, and 10-30% for Zn. The results of this study show that indigenous bacteria in the tailings have the potential to reduce the bioavailable fractions of the three metals studied in the mine tailing and could be further exploited in heavy metal remediation of the sites. Article Highlights The study investigated the potential of indigenous bacteria to immobilize selected heavy metals in tailings samples. The highlights of the manuscript include the following: • The study identified Bacillus cereus OMF 003 and Enterobacter asburiae OMF 532 as heavy metal resistant bacteria in Au mine tailings. • Bioaugmenting tailings with the bacterial isolates reduced the mobility Factor of Ni in the samples by up to 35% for Ni, 90% for Pb and 60% for Zn. • Indigenous Bacillus cereus OMF 003 and Enterobacter asburiae OMF 532 presents significant opportunities for heavy metal immobilization in tailings contaminated environments.
... Under the optimized condition given by RSM, it can also achieve the highest degradation of Kao et al. reported that cyanide concentration higher than 2.6 mg L −1 can induce a longer lag phase and t test result determined that the difference between growths at cyanide concentration above 13 mg L −1 was not significant. In another research, performed by Akcil et al., the ability of degrading weak acid dissociable cyanide (CNWAD) at 400 ppm cyanide concentration was evaluated and the efficiency was found to be nearly 90% (Akcil et al. 2003). ...
Article
Full-text available
Cyanide is used in many industries despite its toxicity. Cyanide biodegradation is affordable and eco-friendly. Sampling from cyanide-contaminated areas from the Muteh gold mine and isolation of 24 bacteria were performed successfully. The selected bacteria—‘Bacillus sp. M01’—showed maximum tolerance (15 mM) to cyanide and deposited in Persian Type Culture Collection by PTCC No.: 1908. In the primary experiments, effective factors were identified through the Plackett–Burman design. In order to attain the maximum degradation by Bacillus sp. M01 PTCC 1908, culture conditions were optimized by using response surface methodology. By optimizing the effective factor values and considering the interaction between them, the culture conditions were optimized. The degradation percentage was calculated using one-way ANOVA vs t test, and was found to have increased 2.35 times compared to pre-optimization. In all of the experiments, R2 was as high as 91%. The results of this study are strongly significant for cyanide biodegradation. This method enables the bacteria to degrade 86% of 10 mM cyanide in 48 h. This process has been patented in Iranian Intellectual Property Centre under Licence No: 90533.
... The effects of these microorganisms would certainly be highly undesirable, and therefore it is necessary to understand how to prevent them. Akcil et al. (2003) studied the effects of cyanide concentration and pH on cyanide treatment using aerobic heterotrophic Pseudomonas species. They tested pH values from 9.2 to 11.4, finding that a pH of 10.5 was optimal for cyanide degradation. ...
Article
The intensive use of groundwater by the gold mining industry is an important sustainability concern, especially in arid and semiarid regions where groundwater is a scarce resource. Alternatives, such as water reuse, treatment and recycling, have been implemented to overcome this issue. The potential use of reclaimed wastewater in gold heap leaching, without decreasing the process efficiency, has not yet been considered. Hence, this review focuses on the physicochemical, biological and chemical features (organic matter, microbial loads, metal ions and anions) of reclaimed wastewater that may limit its use in gold heap leaching.
... In contrast with chemical treatment, biological treatment methods form nontoxic end products as ammonia. Therefore, biological treatment methods are seen to be more advantageous and successful than chemical ones (1,4,5,7,10,(24)(25)(26). In this respect, biodegradation of cyanide by using different microorganisms including bacteria, fungi and plants are being used in cyanide biodegradation processes (27,28). ...
Article
Full-text available
In this study, optimization conditions for cyanide biodegradation by Klebsiella pneumoniae strain were determined to be 25 °C, pH=7 and 150 rpm at the concentration of 0.5 mM potassium cyanide in the medium. Additionally, it was found that K. pneumoniae strain is not only able to degrade potassium cyanide, but also to degrade potassium hexa cyanoferrate( II) trihydrate and sodium ferrocyanide decahydrate with the efficiencies of 85 and 87.5 %, respectively. Furthermore, this strain degraded potassium cyanide in the presence of different ions such as magnesium, nickel, cobalt, iron, chromium, arsenic and zinc, in variable concentrations (0.1, 0.25 and 0.5 mM) and as a result the amount of the bacteria in the biodegradation media decreased with the increase of ion concentration. Lastly, it was also observed that sterile crude extract of K. pneumoniae strain degraded potassium cyanide on the fift h day of incubation. Based on these results, it is concluded that both culture and sterile crude extract of K. pnemoniae will be used in cyanide removal from different wastes.
... In this work only native strains were used along with one Pseudomonas reference strain. This strain was chosen because other authors have shown that it degrades cyanide due to the enzyme nitrilase capable of degrading cyanide, and thus, is widely used for this purpose [4,10,11,16,42,43]. The four isolates showed a degradation of cyanide concentration, evidenced for its reduction in time in the Fig. 5, when compared to the un-inoculated controls. ...
Article
Cyanide is the basic component of many industrial processes, among which is gold processing, being very toxic or even lethal. Treatment, with the help of microorganisms, can be used effectively to reduce the load of harmful chemicals into the environment. The combination of microbiological methods and molecular tools allowed inferring the presence of a dominant population and the composition varied both in the places of origin and in the method used. The dominant phylogenetic affiliations of the bacteria were determined by sequencing the 16S rRNA gene. The isolates identified, as Bacillus and Enterococcus were capable to degrade 41.9 and 27.5 mg CN- L-1 respectively. This study provides information about the presence of a diverse bacterial community associated with residual effluents from cyanidation processes in Colombia and suggests that their presence could play a role in the biological degradation of cyanide compounds, offering an alternative for mining wastewater treatment.
... The implementation of these processes is occurring on a large engineered scale owing to the favourable volumetric reaction rates and overall productivity of suspended cultures [25]. Several literature reports about the wide application of Pseudomonas sp., for degrading phenol and cyanide in batch and continuous mono substrate systems [26][27][28][29][30]. The most recent study by Singh et al. [31] reports about the degradation potential of Pseudomonas putida and Pseudomonas stutzeri isolated from coke oven effluentcontaminated soil for 720 mg L −1 phenol and 37 mg L −1 cyanide in binary system with 80% degradation simultaneously. ...
Article
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Coke oven sector emanates phenol and cyanide as the eminent virulent compounds due to abrupt industrialization which is detrimental in aqueous state, and its severity is increased on simultaneous coexistence even at low concentrations that eventually causes extensive damage to the peripheral ecosystem. The efficacy of isolated mixed bacterial culture comprising of Alcaligenes faecalis JF339228 and Klebsiella oxytoca KF303807 in wastewater treatment was investigated following a batch study. The impact of initial concentration of phenol (100–1500 mg L⁻¹) and cyanide (10–150 mg L⁻¹) on the growth and treatment by the mixed microbial cultures were evaluated over a time period of 72 h. The biodegradation mechanism was explained by Monod, Haldane, Aiba and Edward kinetic models. The maximum specific growth rate was reported to be 0.096 h⁻¹ and 0.126 h⁻¹ for phenol and cyanide respectively. The substrate inhibitory effect became eminent after a concentration of 450 mg L⁻¹ for phenol and 45 mg L⁻¹ for cyanide. Based on the lower sum of squared error (SSE) values, Haldane model for phenol and Edward model for cyanide was found to be favourable for substrate inhibition kinetics. The fate of the secondary intermediates produced after microbial degradation was assessed by phytotoxicity studies using Vigna radiata. The interactive binding of the pernicious pollutants and resultant biodegraded compounds with the DNA (herring sperm DNA) was examined following spectrofluorometric and spectrophotometric anatomization. Toxicity studies revealed that biological treatment was viable for eco benign disposal and results also depicted that both the strains have potential in remediation of phenol and cyanide from coke oven wastewater.
... (Shin et al., 2013) and crushed WEEE (Pradhan and Kumar, 2012) even though their ability to generate cyanide is lower than C. violaceum. However, the types of pseudomonads capable of producing cyanide are debated due to the fact that, under appropriate conditions, they can use cyanide as a nitrogen and a carbon source and degrade it via an oxidative pathway (Akcil et al., 2003;Huertas et al., 2010). Compared with C. violaceum, some Pseudomonas spp. ...
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Gold recovery from limited global resources has gained increasing attention due to a growing demand for gold and heightened social awareness of the high toxicity and the environmental threat of traditional cyanidation. This has led to the development of biomining methods to extract gold from low-grade ores and a variety of wastes using microbes to generate the required reagents. One such method, biocyanidation, has the potential to be an environmentally friendly technique for gold recovery from ore and secondary resources. This review quantifies the limited global gold resources, presents the gold leaching technologies, and describes the biocyanidation process, including the properties of commonly used cyanogenic bacteria and the influencing factors. Methods to measure free biogenic cyanide are summarized, with a focus on the silver nitrate method with potentiometric end-point titration. Finally, biocyanidation is systematically and comprehensively analyzed in the context of commercial and technical limitations imposed by low-grade gold reserves that are infeasible for commercialization, and recommendations for improvements to the process are suggested. This review provides insights on the necessity and urgency of recycling gold from both primary and secondary resources, the crucial role of biocyanidation, the present challenges and future directions toward commercial application of the process.
... Due to the toxicity of cyanide, a large amount of cyanide residue produced every year is a kind of hazardous waste, which has a huge impact on the sustainable development of the gold industry. Cyanide can be used as carbon and nitrogen sources by a variety of microorganisms, such as Pseudomonas and Bacillus, to be degraded (Akcil et al. 2003;Khamar, Makhdoumi-Kakhki and Mahmudy Gharaie 2015). After pelletizing, the cyanide residue can be used to build a heap, and then large amounts of residual cyanide can be removed by microorganisms. ...
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Heap bioleaching is a microbial technology that catalyzes the decomposition of ore without grinding. The crushed ore is stacked on the liner, and the microbial solution flows through the heap from top to bottom. Under the oxidation action of Fe³⁺, valuable metals in sulfide enter the liquid phase as ions, which are then recovered from the subsequent process. The main function of microorganisms are the regeneration of Fe³⁺. This technology has the advantages of low cost, environment friendliness, simple requirements, and suitability for the treatment of low-grade ore. It has been applied to industrial production. However, the technology is still evolving because there are still many problems that are not well explained, such as synergistic effect between microorganisms, the role of extracellular polymeric substances, passivation phenomenon, galvanic interaction between minerals, mode of ore treatment and heap running, the impact of the natural environment, reasonable disposal of tailings, etc. This paper adequately discusses these aspects based on plentiful excellent researches, including the latest ideas, which can provide a comprehensive and in-depth knowledge of heap bioleaching for the readers. Besides, commercial process data, effective improvement measures, environmental protection ways, laboratory research, and optimization methods were reviewed. Based on the comparative analysis of these knowledges, the recommended technical parameters and the remaining challenges are displayed, which can guide a new commercial or pilot-scale heap. Researchers can make new explorations from the potential research directions and methods proposed in this paper, so that heap bioleaching technology can better serve social development.
... Optimal temperatures range from 25 to 50 C, and are typically 30 C for bacteria, 43 C for fungi, and 40 C for plants [50,51]. According to Abdoul-Raimi et al. [6], Akcil [3], and Akcil et al. [52], biological degradation of cyanide can be performed with one or two steps, depending on the enzymes that are involved and the desired end product. The technique is based on obtaining a high metabolic conversion ratio of cyanide to cyanate (bio-oxidation) through bacterial activity, since both carbon and nitrogen are nutrients [9]: ...
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Given that mining is considered to be an essential activity for Mexico’s industrial development, cyanide has been increasingly used to recover precious metals such as gold and silver. Along with that arises the need to develop new technologies to treat the wastes (mining tailings). In addition to their high cyanide content, metal and other contaminants that are found in tailings also present a problem. As a result, conventional (physicochemical) strategies have been developed to reduce contamination from tailings, nonetheless, these have high operating costs and generate unwanted by-products. For this reason, studies have begun to focus on non-conventional strategies to treat free cyanide and cyanide complexes such as fungi, bacterial consortia, and pure bacteria. These are important because of the mechanisms involved in degrading or modifying contaminants at neutral to high pH levels, which convert contaminants into non-hazardous products. The ability of microorganisms to grow at an alkaline pH prevents HCN volatilization. These studies have been performed at the laboratory level using two types of microbial binding: suspended biomass and immobilized biomass. They have used both natural (granite rock, citrus peels, cellulose, gravel) and synthetic (stainless steel, geotextiles, alginate, plastics) packing material, as well as reactors with different types of flow, namely, batch and continuous.
... The mining industry uses technologies based on regeneration methods and chemical oxidation (destruction) methods to neutralize cyanide-containing effluents. Regenerative include: "acidificationvolatilization-reneutralization" method (AVR) [4], bio-oxidation of cyanides by dissolved oxygen O and solar photolytic decomposition [5]. The main disadvantages of these methods include the need for post-treatment of wastewater due to the high residual concentration of cyanide compounds that do not meet the legal standards, the significant processing time, the need to constantly keeping environmental conditions (oxygen regime, ambient temperature and pH). ...
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Photochemical process using of UV component of natural sunlight (hybrid Solar method) in the presence of an oxidizing agent – persulfates was studied for destruction of cyanides in mining effluents. The kinetic regularities was studied for process of photooxidation of cyanides. Comparative destruction of cyanides experiments have shown that the efficiency of the destruction process in the selected oxidative systems changed in the following order: {Solar + PS} > {Solar} > {UV + PS} > {UV} . High treatment efficiency of cyanides using a hybrid system {Solar + PS} is due to high intensity of the UV-C component of the sunlight and the rate of generation of hydroxyl radicals OH and sulfate anion radicals SO 4 -· , respectively. The results obtained indicate the high efficiency of the hybrid Solar-induced method for purification of cyanide-containing pollutants, which allows achieving complete destruction of toxic cyanides to non-toxic products.
... Different degradation techniques have been proposed for the treatment of thiocyanate, including biological treatment [8][9][10][11][12][13], adsorption [14][15][16], or chemical methods [6,[17][18][19][20]. However, the above methods require long treatment times, large tank capacities, and have limitations on parameters such as concentration range, pH, temperature, and solid contents. ...
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The degradation of thiocyanates (SCN⁻) by UV-C-activated persulfate (PS) in the presence of ferric ion (Fe³⁺) was investigated. As a source of monochromatic far-UV-C irradiation (222 nm), mercury-free KrCl excimer lamp was used. Results showed that compared with direct photolysis, UVC/ PS and PS/ Fe³⁺, the combined UVC/ PS/ Fe³⁺ treatment had the highest initial reaction rate ω0 and removal efficiency. 99.99% conversion of thiocyanates (100 mg/L of initial concentration) was achieved in 40 min. The addition of Fe³⁺ in the UVC/ PS treatment was found to reduce energy consumption (calculated as amount of oxidized thiocyanates per consumed electrical energy) by 4.5 times, while only a 30% difference between direct photolysis and UVC/ PS was observed. The high efficiency of the UVC/ PS/ Fe³⁺ process revealed a synergistic effect (synergy index ƒ=1.98). The effect of the initial SCN⁻, PS, and Fe³⁺ molar ratios and UV-C exposure time on SCN⁻ removal in UVC/ PS/ Fe³⁺ was further investigated. It was found that at molar ratios [S2O82–]:[SCN−] = 3:1 and [S2O82–]:[Fe³⁺] = 1:0.1, effective decomposition of SCN⁻ in a wide initial concentration range (from 50 to 500 mg/L or 0.86 to 8.6 mM) can be achieved. The strong role of •OH and SO4•− in the removal of SCN⁻ was confirmed by the addition of radical scavengers. It was demonstrated that the presence of Cu²⁺ in simulated gold mine wastewater effluents neutralizes the inhibitory effects that S2O32– and NH4⁺ have on the degradation process.
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Cyanide is a chemical that is widely distributed in the environment, mainly as a result of anthropogenic activities. Only small quantities are naturally produced. Most industrial activities use this chemical compound for manufacturing a product as electroplating or for extracting gold. Exposure to cyanide results in negative health impacts to the wildlife and humans. In nature, cyanide occurs in several species and fates, of which the free cyanide forms are the most toxic ones. Cyanide can be removed by chemical or biological processes. Biological treatment called bioremediation, which is cost-effective and eco-friendly, is the most applied process to remove cyanide from contaminated environments. This technology focused on the use of microorganisms to remove pollutants. Many microorganisms have been reported to transform the cyanide in another less toxic compound, or to consume cyanide for their growth. The reactions are influenced by environmental parameters such as pH and temperature and by the nutriment availability. Bioremediation technologies were few applied in most of African Countries. Future works should focus on how to adapt the bioremediation technologies that already applied in other parts of the World in African context.
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Solid waste and wastewater effluents emanating from many industries contain free cyanide. The environmental risk of this compound stems from its emission as component of the hydrocyanic gas, which is toxic. Cyanide and its complexes have been shown to have bioaccumulative properties which in turn result in ecological deterioration with both human and animal health implications. In this study, bioremediation of cyanide by A. awamoriisolates was carried using Citrus peel (CP) supplemented growth medium, refined pectin (RP) and Czapek Yeast Agar (CYA) with water as control in shake flask cultures (180 rpm) at 30 °C for 48 h. A. awamorifrom the various media demonstrated cyanide bioremediation potential with the CP medium showing considerably higher cyanide reduction. The presence of quantifiable NH 3 /NH + in the media solutions during the biodegradation was indicative of cyanide reduction. Use of CP adjunct-grown A. awamorito bioremediate cyanide contaminated wastewaters is an alternative environmentally friendly catalytic process for cleaning up the environment and improving water quality.
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Chitosan is a biopolymer with immense structural advantage for chemical and mechanical modifications to generate novel properties, functions and applications. This work depicts new pyridinedicarboxylicacid (PDC) crosslinked chitosan-metal ion films as veritable material for cyanide ion removal from aqueous solution. The PDC-crosslinked chitosan-metal films (PDC-Chit–Ni(II) and PDC-Chit–Fe(III)) were formed by complexing PDC-crosslinked chitosan film with anhydrous nickel(II) and iron(III) chloride salts respectively. The PDC-Chit and its metal films were characterized employing various analytical and spectroscopic techniques. The FT-IR, UV-Visible and the XRD results confirm the presence of the metal ions in the metal coordinated PDC-crosslinked chitosan film. The surface morphological difference of PDC-Chit-Ni(II) film before and after decyanidation was explored with scanning electron microscopy. Furthermore, the quantitative amount of nickel(II) and iron(III) present in the complex were determined using Atomic Absorption Spectrophotometer as 32.3 and 37.2 µg/g respectively which portends the biopolymer film as a good complexing agent. Removal of cyanide from aqueous solution with PDC-Chit, PDC-Chit–Ni(II) and PDC-Chit–Fe(III) films was studied with batch equilibrium experiments. At equilibrium, decyanidation capacity (DC) followed the order PDC-Chit-Ni (II) ≈ PDC-Chit-Fe(III) > PDC-Chit. PDC-Chit-Ni(II) film gave 100% CN- removal within 40 min decyanidation owing to favorable coordination geometry
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Soil and water samples were collected from a watershed in Burkina Faso where illegal artisanal gold extraction using cyanidation occurs. The samples were used to evaluate cyanide contamination and the presence of cyanide degrading bacteria (CDB). Free cyanide (F-CN) was detected in all samples, with concentrations varying from 0.023 to 0.9 mg kg−1, and 0.7–23 μg L−1 in the soil and water samples, respectively. Potential CDB also were present in the samples. To test the effective F-CN degradation capacity of the isolated CDB species, the species were cultivated in growth media containing 40, 60 or 80 mg F-CN L−1, with or without nutrients, at pH 9.5 and at room temperature. More than 95% of F-CN was degraded within 25 h, and F-CN degradation was associated with bacterial growth and ammonium production. However, initial concentrations of F-CN higher than 100 mg L−1 inhibited bacterial growth and cyanide degradation. Abiotic tests showed that less than 3% of F-CN was removed by volatilization. Thus, the degradation of F-CN occurred predominately by biological mechanisms, and such mechanisms are recommended for remediation of contaminated soil and water.
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Separation of cyanide, as a model contaminant, from aqueous solution was investigated using molecular dynamics simulations. In this research, cyanide separation was investigated using armchair silicon carbide (SiC) nanotubes of four different diameters at different applied pressures. The systems included (5,5), (6,6), (7,7) and (8,8) SiC nanotubes placed between two graphene sheets, and an external pressure was applied to the system. The ion permeability, the radial distribution function of nanotube–water and ion– water, the retention time of the cyanide ions, the density of water and water flux and the hydrogen bonding between inner water molecules were investigated. The results showed that all four studied nanotubes accepted water molecules into their interiors, and the (5,5) SiC nanotube could provide high rejection (100%) of cyanide ions.
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The continuous discharge of cyanide-containing effluents to the environment has necessitated for the development of environmentally benign treatment processes that would result in complete detoxification of the cyanide-containing wastewaters, without producing additional environmental toxicants. Since biological detoxification of hazardous chemical compounds has been renowned for its robustness and environmental-friendliness, the ability of the Exiguobacterium acetylicum (GenBank accession number KT282229) and Bacillus marisflavi (GenBank accession number KR016603) to co-metabolise thiocyanate (SCN⁻) and free cyanide (CN⁻) under alkaline conditions was evaluated. E. acetylicum had an SCN⁻ degradation efficiency of 99.9 % from an initial SCN⁻ concentration of 150 mg SCN⁻/L, but the organism was unable to degrade CN⁻. Consequently, B. marisflavi had a CN⁻ degradation efficiency of 99 % from an initial concentration of 200 mg CN⁻/L. Similarly, the organism was unable to degrade SCN⁻; hence, this resulted in the evaluation of co-metabolism of SCN⁻ and CN⁻ by the two microbial species. Optimisation of operational conditions was evaluated using response surface methodology (RSM). A numeric optimisation technique was used to evaluate the optimisation of the input variables i.e. pH, temperature, SCN⁻ and CN⁻ concentrations. The optimum conditions were found to be as follows: pH 9.0, temperature 34 °C, 140 mg SCN⁻/L and 205 mg CN⁻/L under which complete SCN⁻ and CN⁻ degradation would be achieved over a 168-h period. Using the optimised data, co-metabolism of SCN⁻ and CN⁻ by both E. acetylicum and B. marisflavi was evaluated, achieving a combined degradation efficiency of ≥99.9 %. The high degradative capacity of these organisms has resulted in their supplementation on an active continuous biological degradation system that is treating both SCN⁻ and CN⁻.
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In the present study, with the aim of isolating cyanide degrading organisms, four different Gram-positive, aerobic, endospore-forming bacteria (S1 to S4) having the ability to degrade cyanide were isolated by enrichment technique from salt pan region. They were identified as Bacillus sp. and were subjected to cyanide biodegradation assay. Based on the results obtained in cyanide and ammonia estimation, the strain S3 Bacillus cereus was found to show maximum biodegradation ability. The potential isolate S3 was confirmed as Bacillus cereus and submitted in NCBI with the accession number FJ267613. The selected isolate S3 was employed for biodegradation assay in minimal medium which showed that the degradation was higher, in the medium supplemented with glucose. Thereafter optimization studies at different pH, temperature, inoculum concentration, glucose concentration were done which showed that the alkaliphilic Bacillus cereus showed their degradation potential elevated in minimal medium at pH 8, 35 degrees C, 2% inoculum concentration and at 3% glucose concentration. The degradation kinetics was found to be best represented by pseudo-second order kinetic model. The Tempkin isotherm was the best fit isotherm for the degradation of cyanide under experimental conditions used in this study (R-2 = 0.996). Henceforth it can be concluded from the present investigation that there is a high potentiality for alkaliphilic isolate to degrade cyanide in effluent streams very effectively.
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Owing to the presence of several toxic pollutants such as cyanide, phenol, ammonium, coke–oven wastewater is being considered as hazardous stream and needs to be treated properly. In the present study, cyanobacterial consortium of Dinophysis acuminata and Dinophysis caudata, collected from East Kolkata Wetland, was used for the treatment of both synthetic cyanide solution and real coke–oven wastewater. The growth kinetics was studied considering nitrate as substrate. Since consortium showed growth in cyanide solution, a model was proposed considering both nitrate and cyanide as substrates. The simulated data match quite well with experimental ones. Two coke–oven wastewater samples were collected—untreated one from equalization tank and another from secondary clarifier effluent and treated with consortium separately. Lipid was extracted from biomass of native cyanobacterial consortium, biomass treated with raw coke–oven wastewater and biomass treated with secondary clarifier effluents. Fatty acid methyl ester of such lipid samples was analyzed using gas chromatograph.
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The cyanidation process has been, and still remains, a profitable and highly efficient process for the recovery of precious metals from ores. However, this process has contributed to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. The process produces numerous cyanide complexes in addition to the gold cyanocomplex. Additionally, the discharge constituents also include hydrogen cyanide (HCN) – metallic complexes with iron, nickel, copper, zinc, cobalt and other metals; thiocyanate (SCN); and cyanate (CNO). The fate of these complexes in the environment dictates the degree to which these species pose a threat to living organisms. This paper reviews the impact that the cyanidation process has on the environment, the ecotoxicology of the cyanidation wastewater and the treatment methods that are currently utilised to treat cyanidation wastewater. Furthermore, this review proposes an integrated biological approach for the treatment of the cyanidation process wastewater using microbial consortia that is insensitive and able to degrade cyanide species, in all stages of the proposed process.
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Cyanide is among the most toxic chemicals widely employed in the cyanidation process to leach precious minerals, such as gold and silver, by the minerals processing companies worldwide. This present article reviews the determination and detoxification of cyanide found in gold mine tailings. Most of the cyanide remains in the solution or the slurries after the cyanidation process. The cyanide species in the gold tailings are classified as free cyanide, weak acid dissociation, and metallocyanide complexes. Several methods, such as colorimetric, titrimetric, and electrochemical, have been developed to determine cyanide concentrations in gold mine effluents. Application of physical, natural, biological, and chemical methods to detoxify cyanide to a permissible limit (50 mg L ⁻¹ ) can be achieved when the chemical compositions of cyanide (type of species) present in the tailings are known. The levels of cyanide concentration determine the impact it will have on the environment.
Chapter
Fenton oxidation, coagulation/flocculation/sedimendation plus Fenton oxidation, and Fenton oxidation plus activated carbon adsorption were conducted to develop the effective processes for recycling a biologically treated coking plant effluent. Fenton oxidation enhanced adsorptive capacities of activated carbon for the residual organics and also made them more biodegradable. The Fenton oxidation followed by adsorption and biodegradation in a biological activated carbon (BAC) adsorber was the most cost-effective treatment process to recycle the final effluent for in-plant reuses while meeting the much more stringent discharge limits of the future. Batch experiments were also conducted to determine the effects of copper-loading and fixing methods on the capacity of granular activated carbon (GAC) for removing cyanide from KCN (pH = 11), K3Fe(CN)6 solutions and several Shanghai Coking Plant (SCP) effluent samples. KI-fixed carbon (Cu/KI-GAC) was the best GAC samples tested. Adsorption was the primary mechanism of cyanide removal; catalytic oxidation of the adsorbed cyanide on carbon surface contributed a minor amount of the observed removal. Four small adsorbers containing the base GAC and 0–100% of Cu/KI-GAC were employed for treating a Fenton-oxidized/precipitated SCP effluent sample. After the start-up period (<3 weeks) to establish the effective BAC function in the adsorbers, the effluents became stable and met the discharge limits (CODCr < 50 mg/L and TCN < 0.5 mg/L); with >30% Cu/KI-GAC in the adsorber, the effluent would meet the discharge limits during the start-up phase. The BAC function of the adsorber substantially reduced the carbon replacement cost, making the combined Fenton oxidation and BAC treatment process a cost-effective alternative for recycling the biotreated coking plant effluent.
Chapter
Occurrence of huge quantity of cyanide in the environment is due to extensive use in metal-finishing and mining industries. The strong affinity of cyanide with metals makes it favorable as an agent for metal-finishing and lixivant for metal leaching. For many years, cyanide has been used as a leaching reagent for the extraction of precious metals, particularly gold and silver. As a high toxicity of the cyanide it appears on the international priority pollution list. Considering the lethal impact of cyanide on the environment as well as human health, environmental authorities have taken a more stringent attitude toward the presence of cyanide in water. The researchers are trying to investigate best removal techniques for treating hazardous materials like cyanide from metal-finishing industrial wastewater and also strive to reuse of this water for agricultural or other purposes. Although cyanide can be removed and recovered by several processes, while biological treatment process gained an impetus of efficient degradation ability. Biological treatment of cyanide has often been offered as a potentially economical, environmentally friendly alternative to conventional methods. For the treatment of cyanide-containing wastewater, the adsorption and biodegradation are two significant methods. The first one, that is, adsorption is better to other wastewater treatment techniques in terms of efficiency, ease of operation, and low cost. The second, biodegradation method of cyanides removal is better than physical and chemical methods. In cyanide biodegradation process; the cyanide is converted to carbon and nitrogen source by various enzymes present in microorganisms. Biological treatments with bacterial whole cells is another important route for cyanide removal from water in which whole cells are used either in bulk phase or are immobilized on a solid support (bioadsorbent). Immobilized whole cells produce biolayer on bioadsorbent surface and when treated with solution having cyanide, the bacterial cells biodegrade it within the cell as well as it gets adsorbed on bioadsorbent surface. This process is termed as simultaneous adsorption and biodegradation process. In this chapter, we are aimed to make comprehensive description about sustainable bioremoval techniques on the removal of most hazardous materials like cyanide which are released from metal-finishing industrial effluents.
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Cyanide is a toxic substance which can be released from plants. It can be accumulated in the plant-based food fermentation. Therefore, it is necessary to control the concentration of cyanide in food fermentation with cereals as materials. In this study, Saccharomyces cerevisiae was identified as the cyanide-degrading microbe in Baijiu fermentation using metatranscriptomic analysis, and an indigenous strain S. cerevisiae MT-1 was isolated from Baijiu fermentation. This strain could produce nitrilase and degraded 58.42% cyanide in in vitro experiment. The optimum temperature and pH for cyanide degradation activity of S. cerevisiae MT-1 were 30 °C and pH 8.0. Moreover, the cyanide degradation ability of S. cerevisiae MT-1 increased with increase of cyanide concentration. After inoculation of this strain in simulative Baijiu fermentation with additional cyanide, the final cyanide content decreased by 46.45%. In conclusion, this study developed an effective strategy to degrade the content of cyanide in food fermentation.
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For over a century now, the mining industry has been using cyanides for gold and silver recovery. Cyanides are highly toxic for human beings, animals, and aquatic organisms. The available physical and chemical methods of wastewater treatment are cost-ineffective. Certain microorganisms are capable of use cyanides as sources of carbon and nitrogen and turn those into ammonia and carbonate. Some plants are also efficient for the processes of cyanides destruction. Phytoremediation of cyanides may be efficient, cost-effective, environmentally friendly, and be used as an attractive alternative to traditional physical and chemical processes. This article considers the capability of aquatic plants, which grow in the valley of Zerafshan River on the territory of Uzbekistan, to dispose of cyanides and recover the cyanides-contaminated tailings of Navoi Mining & Metallurgical Combinat. Such aspects as the mechanisms of enzymatic detoxification of cyanides by aquatic plants and microorganisms are discussed. The most promising plants to be bedded in the tailings dump are selected.
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Cyanide, a carbon-nitrogen radical, is a major building block in many industries including pharmaceuticals, petrochemical and gold processing. In the gold extraction industry, cyanide has been the universal lixiviant for over a century due to better understood process chemistry, among others. Industries that discharge cyanide-laden effluents are mandated to keep concentrations below 0.2 mg/L to prevent death by cyanide-intoxification, which occurs when cyanide binds to key iron-containing enzymes and prevent them from supplying oxygen-containing blood to the tissues. Techniques used to attenuate cyanide in wastewater can broadly be grouped into chemical, physical and biological methods. In recent times, attention has been placed on biotechnological methods, which make use of cyanotrophic microorganisms to clean up cyanide-contaminated environments. This paper reports on studies set out to assess the ability of Phanerochaete chrysosporium to degrade cyanide under different conditions including changes in cyanide concentration, culture mass, time, closed system and open system. At the end of 24-hour contact in an open agitated system with initial pH of 11.5, a control experiment using 100 mg/L cyanide revealed a natural attenuation of 15% with pH decreasing to 9.88, while the best myco-detoxification of 85% was achieved by contacting 100 mg/L cyanide with 0.5 g culture mass, translating into degradation capacity of 17.2 mg/g (milligram of cyanide per gram of culture) with pH reducing to 8.4 in 24 hours. The degradation could be based on a number of mechanisms including hydrolysis to HCN, oxidation to cyanyl radical and cyanate due to natural attenuation through atmospheric contact, and secretion of organic acid, oxidative enzymes, and hydrogen peroxide by the fungus. Keywords: Cyanotrophic Organism, Myco-Detoxification, Cyanide-Laden Effluents, pH
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Cyanide is a known toxic chemical compound that has an adverse effect on living organisms. Nonetheless, it is one of the active reagents in industries such as mining, pharmaceutical, cosmetics, and food processing companies worldwide. The beneficiation of gold and other precious metals from ore generates great amount of cyanide-bearing contaminants, which is released into the environment. The abundance of cyanide contaminants from these industries have created public health concern since the inception of metal extraction from ore. There are strict regulations on the production, transportation, utilization, and disposal of cyanide-bearing contaminants worldwide. The conventional treatment of cyanide waste is either chemical or physical process. The use of these treatment processes has certain pitfalls like operational challenges, an increase in capital cost, and generation of secondary waste. A number of microorganisms have the potential to utilize cyanide as nitrogen and carbon source and transform it into ammonia and carbon dioxide. Biodetoxification might be efficiently, economically and environmentally safe to detoxify cyanide in contaminants and attractive alternative to conventional detoxification method like chemical or physical. This paper reviews the principles and methods of biodetoxification of cyanide contaminants found in the ecosystem.
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Microbial community and metabolic potential changes in a biological wastewater treatment reactor were investigated using phylogenetic and functional profile analysis from 16S rRNA-gene-based pyrosequencing. Stirred-tank bioreactors fed by cyanide-containing synthetic solutions were inoculated with a sewage sludge and the cyanide-degrading microbial consortium. A better cyanide degradation was observed in the reactors containing the phylum Proteobacteria, but lower efficiency was observed when Firmicutes and Bacteroidetes were dominant. This study shows the important role of phylum Proteobacteria for the cyanide-containing wastewater treatment in the gold processing plant and contributes the fundamentals about the microbial community exposed to the cyanide.
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To evaluate the removal of potassium cyanide (KCN) and its toxicity in algae, an initial comprehensive analysis was performed with Chlorella vulgaris. The algae showed potential removal capability for KCN, with the maximal removal rate of 61%. Moreover, effects of KCN on growth, cellular morphology and antioxidant defense system of C. vulgaris were evaluated. Cell number and chlorophyll a content decreased in most cases, with the maximal inhibition rates of 48% and 99%, respectively. The 100 mg L− 1 KCN seriously damaged the algal cell membrane. Additionally, activity of superoxide dismutase (SOD) was promoted by KCN exposure among 0.1–50 mg L− 1 and inhibited by 100 mg L− 1 KCN, while the malondialdehyde (MDA) content gradually decreased in C. vulgaris with increasing exposure concentration compared to the control. The present study reveals that C. vulgaris is useful in bio-treatment of cyanide-contaminated aquatic ecosystem, except in high concentrations which would cause overwhelming effects.
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Gold nanoparticles (Au NPs) are often used to study the physiochemical behavior and distribution of nanomaterials in natural systems because they are assumed to be inert under environmental conditions, even though Au can be oxidized and dissolved by a common environmental compound: cyanide. We used the cyanogenic soil bacterium, Chromobacterium violaceum, to demonstrate that quorum-sensing-regulated cyanide production could lead to a high rate of oxidative dissolution of Au NPs in soil. After 7 days of incubation in a pH 7 soil inoculated with C. violaceum, labile Au concentration increased from 0 to 15%. There was no observable dissolution when Au NPs were incubated in abiotic soil. In the same soil adjusted to pH 7.5, labile Au concentration increased up to 29% over the same time frame. Furthermore, by using a quorum-sensing-deficient mutant of C. violaceum, CV026, we demonstrated that Au dissolution required quorum-sensing-regulated cyanide production in soil. Au NP dissolution experiments in liquid media coupled with mass spectrometry analysis confirmed that biogenic cyanide oxidized Au NPs to soluble Au(CN)2⁻. These results demonstrate under which conditions biologically-enhanced metal dissolution can contribute to the overall geochemical transformation kinetics of nanoparticle in soils, even though the materials may be inert in abiotic environments.
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The facile removal of cyanide anions from cyanide‐containing water was achieved using CO2 in conjunction with aldehydes which can be recycled from the process. The conversion of the cyanide ion into an insoluble cyanohydrin in water allowed the removal of cyanide and could be used as a method for treating cyanide contaminated wastewater and for recovering cyanide or cyanohydrins for further applications. Carbon dioxide promotes the formation of cyanohydrin in aqueous media and therefore, enabled to purify cyanide contaminated water without reactive oxidants and/or additional energy input. The method was tested in various conditions mimicking goldmine wastewater to elucidate the capacity of CO2‐mediated cyanide remedy process.
Chapter
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Various procedures exist for treating cyanides from different industrial waste waters, and comprise several physical, chemical and biological methods. It is still widely discussed and examined due to its potential toxicity and environmental impact. Physical and chemical methods are highly expensive and also cause secondary pollution. The treatment of cyanide by said method is rarely used, owing to cost-effectiveness. Thus, there is a pressing need for the development of an alternative treatment process capable of achieving high removal efficiency without troubling the environment. Several microbial species can degrade cyanide well into less toxic products. Biodegradation of cyanide compounds may take place through various enzymatic pathways, the enzymes of which are produced by microorganisms that utilize cyanides as substrate. The biological methods for the treatment of cyanide are not only cost-effective but also do not produce any secondary pollution. The present chapter describes the mechanism and ardent approaches of proficient biological methods for the removal of cyanide compounds and their advantages over other treatment processes.
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Anaerobic co-digestion of cassava pulp (CP) and pig manure (PM) under cyanide inhibition conditions was investigated and modeled. Batch experiments were performed with initial cyanide concentrations ranging from 1.5 to 10 mg/L. Cyanide acclimatized sludge from an anaerobic co-digester treating cyanide-containing CP and PM was used as the seed sludge (inoculum). Cyanide degradation during anaerobic digestion consisted of an initial lag phase, followed by a cyanide degradation phase. After a short sludge acclimatization period of less than 3 days, the anaerobic sludge was able to degrade cyanide, indicating that the sludge inhibition due to cyanide was reversible. Cyanide degradation during anaerobic co-digestion of CP and PM followed the first-order kinetics with a rate constant of 0.094 d-1. Gas evolution during batch anaerobic degradation was modeled using the modified Monod-type kinetics to incorporate cyanide inhibition. The model predicted results yielded a satisfactory fit with the experimental data.
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Mine tailings and wastewater generate man-made environments with several selective pressures, including the presence of heavy metals, arsenic and high cyanide concentrations, but severe nutritional limitations. Some oligotrophic and pioneer bacteria can colonise and grow in mine wastes containing a low concentration of organic matter and combined nitrogen sources. In this study, Pseudomonas mendocina P6115 was isolated from mine tailings in Durango, Mexico, and identified through a phylogenetic approach of 16S rRNA, gyrB, rpoB, and rpoD genes. Cell growth, cyanide consumption, and ammonia production kinetics in a medium with cyanide as sole nitrogen source showed that at the beginning, the strain grew assimilating cyanide, when cyanide was removed, ammonium was produced and accumulated in the culture medium. However, no clear stoichiometric relationship between both nitrogen sources was observed. Also, cyanide complexes were assimilated as nitrogen sources. Other phenotypic tasks that contribute to the strain’s adaptation to a mine tailing environment included siderophores production in media with moderate amounts of heavy metals, arsenite and arsenate tolerance, and the capacity of oxidizing arsenite. P. mendocina P6115 harbours cioA/cioB and aoxB genes encoding for a cyanide-insensitive oxidase and an arsenite oxidase, respectively. This is the first report where P. mendocina is described as a cyanotrophic and arsenic oxidizing species. Genotypic and phenotypic tasks of P. mendocina P6115 autochthonous from mine wastes are potentially relevant for biological treatment of residues contaminated with cyanide and arsenic.
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Cyanide and its complexes are produced by industries all over the world as waste or effluents. Biodegradation is considered to be the cheapest and the most effective method to clean-up cyanide from the environment. Several studies on different types of microorganisms that can degrade cyanide in the environment have been carried out. Hydrolytic, oxidative, reductive and substitutive/transfer reactions are some of the common pathways used by microorganisms in cyanide degradation. Biodegradation of cyanide can occur aerobically or anaerobically depending on the environmental conditions. Immobilized enzymes or microorganisms prove to be very effective method of degradation. Microorganisms such as Klebsiella oxytoca, Corynebacterium nitrophilous, Brevibacterium nitrophilous, Bacillus spp., Pseudomonas spp. and Rhodococcus UKMP-5M have been reported to be very effective in biodegradation of cyanide.
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Cladosporium cladosporioides biomass was a highly efficient biosorbent of copper cyanide and nickel cyanide from aqueous solutions. A 32–38 fold concentration of initial 0.5mM metal cyanides could be achieved when biosorption process was carried out under standardised conditions. Residual, unrecoverable metal cyanide could be completely biodegraded in 5–6h. The solution treated with the combined biosorption-biodegradation process was fit for discharge in the environment.
Article
An innovative biological process is described for the treatment of cyanide-, metals- and nitrate-contaminated mine process water. The technology was tested for its ability to detoxify cyanide and nitrate and to immobilize metals in wastewater from agitation cyanide leaching. A pilot-scale demonstration is described in which a pilot plant was constructed to demonstrate the technology on a mine process-waste stream at a mine in Nevada. The demonstration was performed jointly under the Mine Waste Technology Program (MWTP), funded by the US Environmental Protection Agency (EPA) and jointly administered by the US Department of Energy's (DOE) Western Environmental Technology Office (WETO) under Interagency Agreement Number DW89938513-01-0. The Superfund Innovative Technology Evaluation (SITE) demonstration program was also involved in the project. MSE Technology Applications Inc. (MSE), Butte, MT, was the contractor responsible for conducting the project, and Pintail Systems Inc., Aurora, CO, was the technology provider. The pilot-scale unit was field-tested at Echo Bay's McCoy/Cove Mine southwest of Battle Mountain, NV. The biotreatment process was considered successful in destroying cyanide in the mine process water. The process was also determined to be effective in removing metals. The pH was consistently neutralized and nitrates were successfully removed from the mine process water. From the results of these pilot-scale tests, it was concluded that the biotreatment process potentially offers an innovative, cost-effective alternative for the treatment of mining wastewaters.
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An attached growth aerobic biological treatment process has been developed at Homestake Mining Co. 's Homestake gold mine in Lead, SD, which not only oxidizes free and complexed cyanides, indlucing the stable iron complexed cyanides, but also thiocyanate, and the oxidation byproduct ammonia. Through the employment of a mutant strain of bacteria which has been gradually and specifically acclimated to the waste, these potential pollutants are mineralized to relatively harmless sulfates, carbonates, and nitrates. The resultant effluent, through toxicological testing, has been shown compatible with the receiving stream, which serves as a cold water marginal trout fishery.
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This chapter provides an overview of the microbial treatment of industrial wastes. Biochemical wastes treatment with activated sludge as a major agent is effective for the detoxification of domestic wastes. Industrial wastes differ from domestic ones because they have an unstable composition and contain many compounds including those that are oxidized with difficulty. In those conditions, the oxidizing activity of the microorganisms of sludge is repressed and the screening of active destructors is necessary. More than 50 active strains of microorganisms were isolated from activated sludge and waste waters that were capable of destroying the toxic compounds of these industries: methylatyrols, crotonic aldehyde, and toluol. The strains belong to the genus Pseudomonas and Bacillus. Almost all isolated strains of pseudomonads utilize substances, such as toluol, biphenyl, naphtalin and are resistant to high concentration of Hg. Many of these strains contain plasmida of biodegradation that determine their growth on the aromatic compounds.
Article
Former gasworks sites are sometimes be heavily contaminated with spent oxide which contains cyanide complexed to metals (especially iron). In this study, mixed fungal cultures have been isolated from acidic gasworks soil by their ability to utilize iron or nickel cyanide as the sole source of nitrogen at acidic or neutral pH, respectively. A mixed culture comprising Fusarium solani and Trichoderma polysporum was obtained by enrichment on tetracyanonickelate [K2Ni(CN)4] at pH 4. A second mixed culture consisting of Fusarium oxysporum, Scytalidium thermophilum, and Penicillium miczynski was isolated on hexacyanoferrate [K4Fe(CN)6] also at pH 4. Both consortia were able to grow on K4Fe(CN)6 as the sole source of nitrogen under acidic conditions. Growth was associated with progressive removal of cyanide from the culture supernatant. After the termination of growth, at least 50% of the total cyanide had been degraded. Growth of the fungi on K2Ni(14CN)4 as a source of nitrogen at pH 7 yielded 14C-labelled carbon dioxide. Growth of the Fusarium isolates on K2Ni(CN)4 at pH 7, associated with the removal of cyanide, required 5 days as compared to 28 days on K4Fe(CN)6 at pH 4. Cyanide uptake by the fungi on K4Fe(CN)6 at pH 4 occurred simultaneously with removal of iron from the biomass-free medium. Pure cultures of F. solani and F. oxysporum were grown on K2Ni(CN)4 or K4Fe(CN)6 in pure culture at pH 7 or 4, respectively.
Article
The presence of cyanide in industrial effluent waste presents a major environmental and ecological hazard. Although chemical methods of treating this compound are known, bacterial detoxification of cyanide is of interest both in order to understand how cyanide may be dealt with in the environment and to evaluate the economic viability of bacterial systems for cyanide detoxification. The enzyme rhodanese, which catalyzes the formation of thiocyanate and sulfite from cyanide and thiosulfate, has been found in various organisms including Bacillus subtilis and E. coli. Thiobacillus denitrificans was shown to have the highest levels of this enzyme, but growth conditions in continuous culture on defined media have recently been developed for the production of equally high rhodanese levels in the thermophile Bacillus stearothermophilus. Purified rhodanese from this latter organism has already proved to be of value as an antidote in experimental cyanide poisoning in small mammals. This communication reports on the use of a culture of B. stearothermophilus in a small chemical reactor for the continuous removal of cyanide in the form of thiocyanate. The capacity of B. stearothermophilus to remove cyanide in the form of thiocyanate in the process described is high (5 to 8 g NaCN/l culture/hr at 27°C); furthermore, both the rate of cyanide removal and the half life of the process were unaffected by the presence of 5x10-5M Zn2+, Cu2+, Ni2+, or Al3+ over a 12 day period. By running the process at temperatures at which B. stearothermophilus is capable of growth in normal media (i.e. above 35°C) higher rates of cyanide detoxification are possible (14 to 25 g NaCN/l culture/hr at 50°C), although preliminary evidence indicates a reduction in half life at higher temperature.
Article
In the history of Turkey the first use of cyanide for gold recovery has been at the Ovacik Gold Mine. During one-year test period, this mine has successfully been mining and processing after a complicated and extensive environmental impact procedure. In Turkey about 2500 ton of sodium cyanide are used with about 240 ton of sodium cyanide being used at this mine annually. During the test period, it has been shown that an effluent quality (CNWAD) between 0.06 ppm (min) and 1 ppm (max) was achievable after cyanide destruction with the Inco Process. It was also found that treated effluent values (CNWAD) of process water (decant) were between 0.04 ppm (min) and 0.59 ppm (max). This paper presents a review of the cyanidation and cyanide destruction processes at the Ovacik Gold Mine.
Article
Combined biodegradation and internal diffusion effects on the biodegradation rate of ferrous(II) cyanide complex (ferrocyanide) ions by Ca-alginate gel immobilized Pseudomonas fluorescens beads were investigated as a function of initial ferrocyanide concentration and particle size in a batch system. Assuming first-order biodegradation kinetics (ν=kC), first-order biodegradation rate constants for free and different sized immobilized particles were predicted and at 100 mg l−1 bulk ferrocyanide ion concentration experimental effectiveness factors (η) were determined for each particle size. Then using these data, the Thiele modulus (φ) was evaluated for each particle size. Finally effective diffusion coefficient (De) was calculated from the Thiele modulus equation, which is a function of particle size, effective diffusion coefficient and first-order biodegradation rate constant. The results showed that the intraparticle diffusion resistance has a significant effect on the observed biodegradation rate.
Article
The susceptibility of cytochrome oxidases to cyanide means that cyanide is toxic to living cells and cyanide pollution causes great damage to microbial and other ecosystems. Cyanide pollution comes from both industrial wastes and a number of plants, many of agricultural importance, which are cyanogenic and release cyanide into the soil. Despite some understanding of the pathway of cyanide assimilation by aerobic microorganisms, there is little known about cyanide assimilation by anaerobic microorganisms. The author discusses cyanide production, utilization, degradation, and resistance by microorganisms. He concludes that among the most primitive organisms were some that could metabolize cyanide, perhaps in conjunction with other carbon and nitrogen sources. 199 references, 4 figures, 2 tables.
Article
Pseudomonas denitrificans pre-cultured (revived from agar plates) under varying conditions (nitrate absent or present; dissolved oxygen absent or present) was subsequently grown aerobically with or without nitrate present, and finally exposed to anoxic conditions (i.e., aeration stopped and dissolved oxygen stripped from solution). The occurrence and length of diauxic lags following transition from aerobic to anoxic conditions were affected strongly by the nitrate and oxygen exposure history of the biomass.
Article
Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.
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