Chemical and biological removal of cyanides from aqueous and soil-containing systems
TL;DR: In this article, a study was conducted to determine the effect of various factors on the rate and extent of potassium cyanide and hexacyanoferrate (II, complex form) removal from aqueous and soil-containing systems.
Abstract: A study was conducted to determine the effect of various factors on the rate and extent of potassium cyanide and potassium hexacyanoferrate (II, complex form) removal from aqueous and soil-containing systems. In a sterile aqueous system at neutral pH, the concentration of free cyanide was reduced by 42% in 334 h as a result of the protonation of CN− and the volatilization of the HCN formed. In the presence of aerobic mixed consortium of the Institute of Gas Technology and a methylotrophic culture, Isolate 3, the concentration of free cyanide was reduced by 59% and 66% in 357 h, respectively, as a result of combined chemical conversion and microbial degradation. In the sterile aqueous system amended initially with the complex form of cyanide, a less-than-20% reduction in cyanide occured. The sorption equilibria for free and complex cyanides in slurries of the topsoil and manufactured gas plant (MGP) soil was reached in less than 22 and 4 days, respectively. The extent of desorption of cyanides from topsoil and MGP soil into water decreased with time. In sterile systems containing topsoil and MGP soil that were previously equilibrated to cyanides, only a 2% reduction in cyanide concentration occurred in 336 h due to chemical conversion. In the presence of microbial cultures, the concentration of cyanide was reduced by less than 15% and 7% in the slurries of topsoil and MGP soil, respectively. The comparison of the rate and extent of cyanide removal from the aqueous and soil-containing systems in the presence of micro-organisms suggests that cyanides were retained by the solid phase of the soil-containing systems and therefore were less available for biodegradation.
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TL;DR: Significant advances have been reported in the use of plants for the phytoremediation of cyanide compounds and evidence for the biodegradation of thiocyanate and metal-cyanide complexes has become available, however, physical and economic factors still limit the application of cyanides biodegrades.
268 citations
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...Cyanide bioavailability and solubility in soil–water systems are also determining factors [11]....
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TL;DR: In this article, the basic chemistry of cyanide, methods by which cyanide can be analyzed, and aspects of the cyanide behavior that are most relevant to environmental considerations at mineral processing operations associated with gold mines.
121 citations
TL;DR: This study suggests that complete removal of N-organics can be combined with a significant removal of nitrogen by using algal–bacterial systems and that further residual biomass digestion could pay-back part of the operation costs of the treatment plant.
Abstract: When compared with Chlorella vulgaris, Scenedesmus obliquus and Selenastrum capricornutum, C. sorokiniana presented the highest tolerance to acetonitrile and the highest O2 production capacity. It also supported the fastest acetonitrile biodegradation when mixed with a suitable acetonitrile-degrading bacterial consortium. Consequently, this microalga was tested in symbiosis with the bacterial culture for the continuous biodegradation of acetonitrile at 2 g l−1 in a stirred tank photobioreactor and in a column photobioreactor under continuous illumination (250 μE m−2 s−1). Acetonitrile removal rates of up to 2.3 g l−1 day−1 and 1.9 g l−1 day−1 were achieved in the column photobioreactor and the stirred-tank photobioreactor, respectively, when operated at the shortest retention times tested (0.4 days, 0.6 days, respectively). In addition, when the stirred-tank photobioreactor was operated with a retention time of 3.5 days, the microbial culture was capable of assimilating up to 71% and nitrifying up to 12% of the NH4+ theoretically released through the biodegradation of acetonitrile, thus reducing the need for subsequent nitrogen removal. This study suggests that complete removal of N-organics can be combined with a significant removal of nitrogen by using algal–bacterial systems and that further residual biomass digestion could pay-back part of the operation costs of the treatment plant.
117 citations
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...Unfortunately, the aerobic treatment of organonitriles is often limited by the high volatility of these compounds, which leads to significant stripping of the pollutants during the degradation process (Chen et al. 1981; Aronstein et al. 1994)....
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TL;DR: The data suggest that phytoremediation of cyanide may be possible and ecologically safe due to the lack of cyanine bioaccumulation in aerial tissues, and ferrocyanide uptake and metabolism is suggestive.
Abstract: Cyanide compounds are contaminants of growing importance that could be remediated biologically via phytoremediation, provided the plants possess suitable mechanisms for managing these pollutants without toxicity. The transport and metabolism of two cyanide compounds, potassium cyanide and potassium ferrocyanide, by willow (Salix eriocephala L. var. Michaux) were compared using a hydroponic system that preserved cyanide speciation and solubility. The cyanide compounds were labelled with 15N to quantify transport while a novel tissue extraction procedure was used to relate tissue 15N to cyanide content and speciation. These analyses revealed that although little free cyanide was detected in the aerial tissues of plants exposed to either of these two cyanide compounds, significant enrichments in 15N were observed, suggesting transport and subsequent metabolism of free cyanide as well as ferrocyanide. The results for ferrocyanide are of interest because this molecule is resistant to microbial degradation and if oxidized to ferricyanide is purportedly membrane impermeable. Nevertheless, these results and mass balance calculations for tissue 15N and solution cyanide confirming 100% recovery for the added ferrocyanide are suggestive of ferrocyanide uptake and metabolism. This study provides new information describing the biological transport and metabolism of these two cyanide compounds in plants. Moreover, the data also suggest that phytoremediation of cyanide may be possible and ecologically safe due to the lack of cyanide bioaccumulation in aerial tissues.
100 citations
TL;DR: In this article, the binding capacity of the biosorbent was investigated as a function of the initial pH, initial iron(III)-cyanide complex ion and biosorbents concentration.
97 citations
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TL;DR: The author discusses cyanide production, utilization, degradation, and resistance by microorganisms and concludes that among the most primitive organisms were some that could metabolize cyanide, perhaps in conjunction with other carbon and nitrogen sources.
Abstract: 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.
311 citations
TL;DR: In this article, the effect of low concentrations of surfactants on the biodegradation of sorbed aromatic compounds in soil was investigated, and it was shown that surfactant-induced desorption is not appreciable.
Abstract: A study was conducted to determine the effect of low concentrations of surfactants on the biodegradation of sorbed aromatic compounds in soil. The nonionic alcohol ethoxylate surfactants Alfonic 810-60 and Novel II 1412-56 increased the extent of desorption of phenanthrene from a mineral soil. Alfonic 810-60 enhanced desorption of biphenyl from this soil at one concentration tested, but Novel II 1412-56 did not. Less than 0.01{per thousand} of the added phenanthrene and biphenyl was present in solution after their introduction into an organic soil, and the surfactants did not promote desorption. The two surfactants at 10 {mu}g/g of soil markedly increased the extent of biodegradation of phenanthrene in both the mineral and the organic soil; the stimulation was greater in the organic soil. Biphenyl mineralization in the mineral soil was not affected by either surfactant, but biodegradation in the organic soil was enhanced by Alfonic 810-60 at 100 {mu}g/g. The authors suggest that surfactants at low concentrations may promote the mineralization of sorbed aromatic compounds in polluted soils, even when surfactant-induced desorption is not appreciable.
274 citations
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...The preparation of the soils amended with the radiolabeled chemicals for determining sorption/desorption rates was described previously (Aronstein et al. 1991; Aronstein and Alexander 1992)....
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TL;DR: This chapter focuses on cyanide metabolism in micro-organisms, which is probably the simplest secondary metabolic system and a continued investigation of cyanide formation should greatly aid a better understanding of microbial secondary metabolism.
Abstract: Publisher Summary This chapter focuses on cyanide metabolism in micro-organisms. It is noted that cyanide is a relatively common product of microbial as well as plant metabolism. Cyanide production by micro-organisms has many characteristics typical of secondary metabolism. In addition, it is probably the simplest secondary metabolic system and a continued investigation of cyanide formation should greatly aid a better understanding of microbial secondary metabolism. Cyanide degradation by Chromobacterium violaceum, or C. violaceum, is known to synthesize at least three enzymes capable of metabolizing cyanide. These include rhodanese, γ-cyano-α-aminobutyric acid synthase, and β-cyanoalanine synthase. The concentrations of all three enzymes increase in the post-cyanogenic period. The buildup of β-cyanoalanine is particularly noteworthy in bacteria grown under conditions of high cyanogenesis. The suspensions of harvested C. violaceum cells are also able to form β-cyanoalanine when incubated with cyanide and serine.
212 citations
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...It was also shown that even relatively low amounts of free cyanide produced by chemical decomposition may support microbial growth of cyanide degraders in the systems amended initially with the complex form (Finnegan et al. 1991; Knowles and Bunch 1986)....
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TL;DR: In this paper, the speciation of dissolved cyanide was studied under pH and redox conditions relevant to soil and groundwater environments, and it was shown that the free cyanide form will predominate at chemical equilibrium in the soil.
Abstract: In order to improve the assessment of the bioavailability and behavior of cyanide in the environment, the speciation of dissolved cyanide was studied under pH and redox conditions relevant to soil and groundwater environments. The partition of cyanide over free cyanide [HCN(aq)+ CN - ] and iron cyanide complexes [or hexacyanoferrates, e.g., Fe(CN) 6 3- and Fe(CN) 6 4- ] at thermodynamic equilibrium was calculated as a function of pH and redox potential. These calculations show that the free cyanide form will predominate at chemical equilibrium in the soil
143 citations
TL;DR: A simple method of isolating bacteria that utilize cyanide as a source of nitrogen for growth has been developed, with results showing that cyanide-grown bacteria produced stoichiometric amounts of ammonia from cyanide when pulsed with cyanide under aerobic conditions.
Abstract: SUMMARY: A simple method of isolating bacteria that utilize cyanide as a source of nitrogen for growth has been developed This involved supplying hydrogen cyanide as a vapour to glucose-containing minimal-salts agar plates The bacteria isolated were Gram-negative, oxidase-positive rods producing a fluorescent green pigment and were tentatively identified as strains of Pseudomonas fluorescens Three organisms were studied further and shown to be P fluorescens biotype II One of these (NCIB 11764) was grown in a glucose-containing fed-batch culture with either NH4Cl or KCN as the limiting nutrient Cyanide-grown bacteria produced stoichiometric amounts of ammonia from cyanide when pulsed with cyanide under aerobic conditions Stimulation of oxygen uptake was seen on addition of cyanide to suspensions of cyanide-grown but not ammonia-grown bacteria
137 citations
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...1992; Castric and Strobel 1969; Harris and Knowles 1983), carbon source (Murphy and Nesbitt 1964), or both (Harris and Knowles 1983; Skowronsky and Strobel 1969; Winter 1962)....
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...Studies on the microbial degradation of cyanide have concentrated on enrichment and isolation of micro-organisms that are capable of utilizing the free cyanide as a sole nitrogen source (Kunz et al. 1992; Castric and Strobel 1969; Harris and Knowles 1983), carbon source (Murphy and Nesbitt 1964), or both (Harris and Knowles 1983; Skowronsky and Strobel 1969; Winter 1962)....
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