Application of ferrate(VI) in the treatment of industrial wastes containing metal-complexed cyanides : A green treatment

Ferrate（VI） was employed for the oxidation of cyanide （CN） and simultaneous removal of copper or nickel in the mixed/complexed systems of CN-Cu, CN-Ni, or CN-Cu-Ni. The degradation of CN （1.00 mmol/L） and removal of Cu （0.095 mmol/L） were investigated as a function of Fe（Ⅵ） doses from 0.3-2.00 mmol/L at pH 10.0. It was found that Fe（Ⅵ） could readily oxidize CN and the reduction of Fe（Ⅵ） into Fe（Ⅲ） might serve efficiently for the removal of free copper ions. The increase in Fe（Ⅵ） dose apparently favoured the CN oxidation as well as Cu removal. Moreover, the pH dependence study （pH 10.0-13.0） revealed that the oxidation of CN was almost unaffected in the studied pH range （10.0-13.0）, however, the maximum removal efficiency of Cu was obtained at pH 13.0. Similarly, treatment was carded out for CN-Ni system having the initial Ni concentration of 0.170 mmol/L and CN concentration of 1.00 mmol with Fe（Ⅵ） dose 2.00 mmol at various pH values （10.0-12.0）. Results showed a partial oxidation of CN and partial removal of Ni. It can be observed that Fe（Ⅵ） can partially degrade the CN-Ni complex in this pH range. Further, Fe（Ⅵ） was applied for the treatment of simulated industrial waste/effluent waters treatment containing CN, Cu, and Ni.

Interaction mechanism of cyanide with pyrite during the cyanidation of pyrite and the decyanation of pyrite cyanide residues by chemical oxidation

The toxic cyanides in cyanide residues produced from cyanidation process for gold extraction are harmful to the environment.Pyrite is one of the main minerals existing in cyanide residues.In this work,the interaction of cyanide with pyrite and the decyanation of pyrite cyanide residue were analyzed.Results revealed that high pH value,high cyanide concentration,and high pyrite dosage promoted the interaction of cyanide with pyrite.The cyanidation of pyrite was pseudo-second-order with respect to cyanide.The decyanation of pyrite cyanide residue by Na_(2)SO_(3)/air oxidation was performed.The cyanide removal efficiency was 83.9% after 1 h of reaction time under the optimal conditions of pH value of 11.2,SO_(3)^(2-) dosage of 22 mg·g^(-1),and air flow rate of 1.46 L·min^(-1).X-ray photoelectron spectroscopy analysis of the pyrite samples showed the formation of Fe(Ⅲ)and FeSO_(4) during the cyanidation process.The cyanide that adsorbed on the pyrite surface after cyanidation mainly existed in the forms of free cyanide(CN^(-))and ferrocyanide(Fe(CN)_(6)^(4-)),which were effectively removed by Na_(2)SO_(3)/air oxidation.During the decyanation process,air intake promoted pyrite oxidation and weakened cyanide adsorption on the pyrite surface.This study has practical significance for gold enterprises aiming to mitigate the environmental impact related to cyanide residues.

Clinical Case Report of Acute Heart Injury and Acute Rhabdomyolysis Due to Cyanide Poisoning

Cyanide poisoning is one of the most dangerous poisonings, and it can be absorbed into the body through the mouth, inhalation and through the skin. A 32-year-old female patient was admitted to our poison control center because of high fever, severe vomiting, and seizures. Physical examination found that the patient was drowsy, had a high fever of 40 degrees Celsius, pulse of 140 beats/minute, and increased tendon and bone reflexes. Exploiting the patient’s information, it was discovered that the patient bought Cyanide to drink with the intention of committing suicide. The patient was quickly treated with gastric lavage and activated charcoal. Echocardiography recorded EF: 35%, reduced movement of the entire myocardium. CK blood test: 4562 U/L. The patient’s condition rapidly deteriorated and the patient was made ECMO, IHD and CVVHDF. After 3 days of treatment, the patient’s condition did not improve, so the family asked for the patient to go home. This article aims to describe the rapidly progressing and severe damage to the heart and muscles of patients with cyanide poisoning.

Fe extraction from high-silicon and aluminum cyanide tailings by pretreatment of water leaching before magnetic separation

Pretreatment of high content of Si- and Al-containing cyanide tailings by water leaching to remove some impurities, such as the major impurities minerals of Si and A1, as well as its effect on Fe extraction in the water leaching process was investigated. The effects of different parameters on iron recovery were studied, and the reaction parameters were proposed as follows： sodium carbonate content of 30%, water leaching at 60 ~C for 5 min, liquid/solid ratio of 15：1, and exciting current of 2 A. Under these optimal conditions, magnetic concentrate containing 59.11% total iron and a total iron recovery rate of 76.12% was obtained. In addition, the microstructure and phase transformation of the process of water leaching were studied by X-ray powder diffraction technique （XRD）, Electronic image of backscattering （BEI）, X-ray fluorescence （XRF）, and energy dispersive spectrometry （EDS）. The results indicate that the soluble compound impurities generated in the roasting process are washed out, and the dissoluble substances enter into nonmagnetic materials by water leaching, realizing the effective separation of impurities and Fe.

Greener approach towards the facile synthesis of 1,4-dihydropyrano[2,3-c]pyrazol-5-y1 cyanide derivatives at room temperature

This report describes triethylammonium acetate （TEAA） ionic liquid catalyzed one pot synthesis of 6-amino-4-aryl-5-cyano-3- methyl-1-phenyl-1,4-dihydropyrano [2,3-c]pyrazoles by the reaction of aromatic aldehyde, malononitrile and 3-methyl-1-phenyl-2- pyrazolin-5-one at room temperature. TEAA plays dual role as reaction media and catalyst. It can also be easily recovered and reused in several runs. TEAA provides greener reaction protocol to present methodology which obviates the need of organic solvents, expensive and toxic catalyst.

Granular activated carbons from palm nut shells for gold di-cyanide adsorption

Granular activated carbons were produced from palm nut shells by physical activation with steam. The proximate analysis of palm nut shells was investigated by thermogravimetric analysis, and the adsorption capacity of the activated carbons, produced as a result of shell pyrolysis at 600℃ followed by steam activation at 900℃ in varying activation times, was evaluated using nitrogen adsorption at 77 K. Applicability of the activated carbons for gold dicyanide adsorption was also investigated. Increasing the activation hold time with the attendant increase in the degree of carbon burn-off results in a progressive increase in the surface area of the activated carbons, reaching a value of 903.1 m2/g after activation for 6 h. The volumes of total pores, mieropores, and mesopores in the activated carbons also increase progressively with the increasing degree of carbon burn-off, resulting from increasing the activation hold time. The gold di-cyanide adsorption of the activated carbons increases with the rise of pore volume of the activated carbons. The gold di-cyanide adsorption of palm nut shell activated carbon obtained after 6-h activation at 900℃ is superior to that of a commercial activated carbon used for gold di-cyanide adsorption.

Recovery of Gold and Silver and Removal of Copper, Zinc and Lead Ions in Pregnant and Barren Cyanide Solutions

Over the past decade the concern about toxic metals in freshwater has increased. Environmental laws such as the Clean Water Act have forced industries that produce metal containing wastewater to treat their wastewater prior to discharge. The purpose of this study was to investigate the use of a novel method for the minimization of heavy metals in the wastewater from the mining industry. A very promising electrochemical treatment technique that does not require chemical additions is electrocoagulation (EC) and sulphide precipitation. The present study has been done for the recovery of gold and silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes;that is a developed alternative technology for the Merril-Crowe process. The average gold and silver content in pregnant solution was 4.27 and 283 ppm respectively and the recoveries were 92% for gold and 95% for silver, with optimum operating parameters of pH 10, residence time of 20 minutes and addition of sodium chloride of 4 gr/L. The results of precipitation process show that the elimination of lead, zinc, cooper and iron ions from the barren solution was successful, with optimum operating parameters of pH 3 and residence time of 15 minutes, and the recoveries were 99% of these ions. Finally the characterization of the solid products of gold and silver formed during the EC process with Scanning Electronic Microscope was performed. Results suggest that magnetite particles and amorphous iron oxyhydroxides (lepidocrocite) were present.

Unveiling anomalous lattice shrinkage induced by Pi-backbonding in Prussian blue analogues

Transition-metal(TM)-based Prussian blue and its analogues(TM-PBAs) have attracted considerable attention as cathode materials owing to their versatile ion storage capability with tunable working voltages. TM-PBAs with different crystal structures, morphologies, and TM combinations can exhibit excellent electrochemical properties because of their unique and robust host frameworks with well-defined<100> ionic diffusion channels. Nonetheless, there is still a lack of understanding regarding the performance dependence of TM-PBAs on structural changes during charging/discharging processes. In this study, in situ X-ray diffraction and X-ray absorption fine structure analyses elucidate the TMdependent structural changes in a series of TM-PBAs during the charging and discharging processes.During the discharging process, the lattice volume of Fe-PBA increased while those of Ni-and Cu-PBAs decreased. This discrepancy is attributed to the extent of size reduction of the cyanometallate complex([Fe(CN)_(6)]) via pi-backbonding from Fe to C due to redox flips of the low-spin Fe^(3+/2+) ion. This study presents a comprehensive understanding of how TM selection affects capacity acquisition and phase transition in TM-PBAs, a promising class of cathode materials.

Cassava Flour: Quantification of Cyanide Content

Cassava flours are obtained from the roots of Manihot esculenta Crantz and daily fairly consumed by the Brazilian population considering it comes to hum food, and also inserted into food baskets, besides to present low cost and easy access, in addition to being plant easily cultivated by the population. However, the food obtained with cassava may contain hydrocyanic acid, in the form of cyanogenic glycoside when those meals are not cooked properly. The oral toxicity can range 30 - 210 mg/kg body, the average daily consumption per capita in larger rural areas than in urban areas for cassava flour 19.1 g against 4.7 g, respectively. Brazil’s North and Northeast have higher consumption of cassava flour, associated with family monthly monetary income, making this region more vulnerable to poisoning. The objective of this study was to quantify cyanogenic glycosides present in some types of Brazilian cassava foods by means of spectrophotometric technique (reading at a wavelength of 530 nm). For quantitative determination of cyanide content, linamarase hydrolysis was used. The amount of cyanide was determined, and results were: artisan toasted cassava flour: 15 mg/500g, sweet cassava starch: 32.5 mg/500g, artisan dried cassava flour: 37.5 mg/500g, “bijuzada” cassava flour: 60 mg/500g, industrialized, toasted cassava flour: 115 mg/500g, industrialized, raw cassava flour: 140 mg/500g, and wet cassava flour: 225 mg/500g. Considering the chronic ingestion of cyanide present in these foods, they can cause public health problems.

Recovery of Silver from Cyanide Solutions Using Electrochemical Process Like Alternative for Merrill-Crowe Process

The conventional processes for recovery of silver from cyanide leach solutions are the carbon adsorption, the Merrill-Crowe zinc dust cementation, the Ion Exchange, and Solvent Extraction processes;among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising electrochemical process that does not require high concentrations of silver in cyanide solutions to yield excellent results and neither pretreatment of cyanide solutions like Merrill-Crowe process (deoxygenating and clarification). The present study has been done for the recovery of silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes, and therefore develops an alternative technology for Merril-Crowe process. The average silver content in pregnant solution was of 52 ppm, recovery was obtained of 99% of silver, with this optimum operating parameters, pH = 8, residence time = 20 minutes and conductivity by addition of sodium chloride = 4 grs/L. Finally the characterization of the solid products formed during the EC process with X-ray Diffraction and Scanning Electronic Microscope was performed, results suggest that magnetite particles and amorphous iron oxyhydroxides are present (Lepidocrocite).

Syntheses,Crystal Structures and Magnetic Studies of Heterobimetallates Based on Paramagnetic Ruthenium(Ⅲ) Building Block [Ru~Ⅲ(salchda)(CN)2]

The syntheses, crystal structures and magnetic properties of two cyano-bridged heterobimetallic compounds prepared from a paramagnetic Ru^Ⅲ building block, transK[Ru^Ⅲ（salchda）（CN）2]（1, salchda = N,N＇-bis（salicylidene）-o-cyclohexylenediamine）, are described.1 reacts with hydrated CoCl2 and [Mn Ⅲ（salchda）（Cl）（H2O）] in MeOH to produce a trinuclear compound {[Ru^Ⅲ（salchda）（CN）]2（μ-CN）2[Co（MeOH）4]·4MeOH}n（2） and a dinuclear{[Ru^Ⅲ（salchda）（CN）]（μ-CN）[Mn^Ⅲ（salchda）（MeOH）]·2MeOH}n（3）, respectively. Both compounds exhibit intramolecular ferromagnetic coupling between Ru^Ⅲ and 3-d metal centers via the cyano bridge and intermolecular antiferromagnetic coupling. Moreover, 2 exhibits antiferromagnetic ordering below 3.4 K.

TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino- 3-formylcoumarin （sensor a） and 7-diethylamino-3-（2-nitrovinyl）coumarin （sensor b）, are proposed to account for their distinct sensing mechanisms and experimental phenomena. The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysieal properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore, the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescence for the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.

Treatment of copper-rich gold ore by cyanide leaching, ammonia pretreatment and ammoniacal cyanide leaching

The treatment of a copper sulphide-bearing gold ore by direct cyanide leaching, ammonia pretreatment and ammoniacal cyanide leaching was investigated. Dissolution behaviour of gold and copper in these leaching systems was demonstrated. Severe interference by the copper containing sulphides with cyanide leaching of gold is observed at p（NaCN）〈5 g/L. This is consistent with speciation calculations. Ammonia pretreatment is shown to readily eliminate the copper interference, allowing almost complete extraction of gold with concomitantly low reagent consumption in subsequent cyanide leaching. In ammoniacal cyanide system, Box-Behnken experimental design shows the main and interaction effects of NH3, NaCN and Pb（NO3）2. The concentrations of NH3 and NaCN are statistically confirmed to be significant factors affecting extraction of gold while the effect of Pb（NO3）2 is limited. Increasing the concentration of NH3 improves the selectivity and extent of gold extraction and reduces the cyanide consumption. The contribution of reagent interactions to gold extraction is statistically insignificant. These findings highlight that ammonia pretreatment and ammonia-cyanide leaching are promising approaches for the treatment of gold ores with high copper sulphide content.

Mechanism of sodium sulfide on flotation of cyanide-depressed pyrite

The mechanism of sodium sulfide(Na2S)on the flotation of cyanide-depressed pyrite using potassium amyl xanthate(PAX)as collector was investigated by flotation test and electrochemical measurements.The flotation results show that both PAX and Na2S can promote the flotation recovery of cyanide-depressed pyrite and their combination can further improve the pyrite flotation recovery.Electrochemical measurements show that PAX and Na2S interacted with cyanide-depressed pyrite through different mechanisms.PAX competed with cyanide and was adsorbed on the pyrite surface in the form of dixanthogen,thus enhancing the hydrophobicity and flotation of cyanide-depressed pyrite.Unlike PAX,Na2S rendered the pyrite surface hydrophobic through the reduction of ferricyanide species and the formation of elemental sulfur S0 and polysulfide Sn2-.The combined application of PAX and Na2S induced superior pyrite flotation recovery because of a synergistic effect between PAX and Na2S.

Footprint of harmful substances in spent pot lining of aluminum reduction cell

Spent pot lining(SPL) from aluminum reduction cells is considered to be hazardous materials due to containing a large amount of soluble fluoride salts and trace toxic cyanides. The distribution of fluorides and cyanide in a 350 kA cell operated for 2396 days was analyzed and the footprint and corrosion mechanism of the harmful substances in SPL were also studied. It is found that the fluorides are mainly concentrated in the cathode carbon block and the layer of dry barrier under the cathodes, which is closely related to permeability of the cathodes and dry barrier the fluorides penetrate in. Cyanide has a low concentration in the cell center and a high concentration in the sidewall, which is positively related to the air amount entering into the areas in the cells.

Mechanisms underlying attenuation of apoptosis of cortical neurons in the hypoxic brain by flavonoids from the stems and leaves of Scutellaria baicalensis Georgi

Flavonoids from the stems and leaves of Scutellaria baicalensis Georgi, an antioxidant, markedly improve memory impairments and neuronal injuries. In the present study, primary cortical neurons of rats were exposed to potassium cyanide to establish a model of in vitro neural cell apoptosis. Inhibition of apoptosis by flavonoids from the stems and leaves of Scutellaria baical- ensis Georgi at concentrations of 18.98, 37.36, and 75.92 gg/mL was detected using this model. These flavonoids dramatically increased cell survival, inhibited cell apoptosis and excessive pro- duction of malondialdehyde, and increased the activities of superoxide dismutase, glutathione peroxidase, and Na＋-K＊-ATPase in primary cortical neurons exposed to potassium cyanide. The flavonoids from the stems and leaves of Scutellaria baicalensis Georgi were originally found to have a polyhydric structure and to protect against cerebral hypoxia in in vitro and in vivo models, including hypoxia induced by potassium cyanide or cerebral ischemia. The present study suggests that flavonoids from the stems and leaves of Scutellaria baicalensis Georgi exert neuroprotective effects via modulation of oxidative stress, such as malondialdehyde, superoxide dismutase, glutathione peroxidase and Na＋-K＋-ATPase disorders induced by potassium cyanide.

Copper solvent extraction from alkaline cyanide solution with guanidine extractant LIX 7950

The use of the guanidine extractant LIX 7950 extracting copper and cyanide from alkaline cyanide solution was investigated.The extraction of copper and cyanide under different initial copper and extractant concentrations was examined and the stoichiometric extraction constant of Cu(CN)32- with LIX 7950 was calculated.Both the distribution coefficient and the stoichiometric extraction constant of Cu(CN)3 2-with LIX 7950 decrease when the temperature is varied from 25℃to 45℃, indicating the extraction process is exothermic.The calculated enthalpy change of the reaction(-HΘ)is about-190 kJ/mol.The copper extraction isotherms under different molar ratios of cyanide to copper are established.The preferential extraction of Cu(CN)32- over Cu(CN)4 3-and CN -has been confirmed and a high cyanide-to-copper molar ratio tends to suppress copper loading. The loaded copper and cyanide can be stripped efficiently by the moderately strong NaOH solutions(0.5-1.0 mol/L)and the presence of NaCN in the stripping solution facilitates copper stripping.

Flotation behaviors and mechanisms of chalcopyrite and galena after cyanide treatment

Adsorbing tests between CN? and chalcopyrite or galena were conducted firstly, and then flotation tests of the twocyaniding minerals were investigated in butyl xanthate (BX) system. Results showed that the interaction between CN? and the twomineral surfaces were both chemical adsorption and can be described by the Langmuir adsorption isotherm model. In the optimumcondition of pH 6.5 and 4.0 mg/L BX, the recovery of cyaniding chalcopyrite and galena reached 82.1% and 63.9%, respectively. BXimproved the hydrophobicity of the surfaces of the two minerals, although CN? reduced the contact angle on the surface of minerals.The inhibitory effect of CN? on chalcopyrite far outweighed galena. Electrostatic adsorption exists in the interaction between BX andthe surface of galena after cyanide treatment in the pH range of 4.2?8.4, while the interactions between BX and the surface ofchalcopyrite after cyanide treatment is chemical adsorption.

Efficient destruction of sodium cyanide by thermal decomposition with addition of ferric oxide

Efficient destruction of cyanide by thermal decomposition with ferric oxide addition was proposed. The mechanism of destruction of sodium cyanide with or without ferric oxide addition under various conditions was examined by XRD, DSC-TG, and chemical analysis technologies. In the absence of ferric oxide, sodium cyanide decomposes at 587.4 ℃ in air and 879.2 ℃ in argon atmosphere. In the presence of ferric oxide, about 60% of sodium cyanide decomposes at 350 ℃ for 30 min in argon, while almost all sodium cyanide decomposes within 30 min in air or O2 with mass ratio of ferric oxide to sodium cyanide of 1:1. The increase of ferric oxide addition, temperature, and heating time facilitates the destruction of sodium cyanide. It is believed that with ferric oxide addition, NaCN reacts with Fe2O3 to form Na4Fe(CN)6, Na2CO3, NaNO2 and Fe3O4 in argon. NaCN decomposes into NaCNO, Na4Fe(CN)6, minor NaNO2, and the formed NaCNO and Na4Fe(CN)6 further decompose into Na2CO3, CO2, N2, FeOx, and minor NOx in air or O2.

Differences of cyanide leaching between calcine and dust from refractory gold concentrates

Differences of cyanide leaching between the calcine and the dust from a refractory gold concentrate were investigated by comparative method. Results showed that gold leaching efficiencies of the calcine and the dust were 85.31% and 54.30%, respectively, with direct cyanidation. Contents and existing forms of arsenic and carbon were the main reasons for those differences. The maximum gold leaching efficiencies of the calcine and the dust were 87.70% and 58.60%, respectively, with cyanidation after NaOH pre-leaching. Harmful elements removal, gold loss in NaOH pre-leaching and iron oxides hindrance codetermined gold leaching efficiencies of the calcine and the dust. After H2SO4 pre-leaching, the maximum gold leaching efficiencies of the calcine and the dust achieved 94.96% and 80.40%, respectively. The effect of carbonaceous matter was the main reason for differences for leaching efficiencies of the calcine and the dust. Based on those differences, two proper gold extraction processes were put forward, and gold leaching efficiencies for the calcine and the dust achieved 94.91% and 91.90%, respectively.