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.

Reversible solid-liquid conversion enabled by self-capture effect for stable non-flow zinc-bromine batteries

Non-flow aqueous zinc-bromine batteries without auxiliary components(e.g.,pumps,pipes,storage tanks)and ion-selective membranes represent a cost-effective and promising technology for large-scale energy storage.Unfortunately,they generally suffer from serious diffusion and shuttle of polybromide(Br^(-),Br^(3-))due to the weak physical adsorption between soluble polybromide and host carbon materials,which results in low energy efficiency and poor cycling stability.Here,we develop a novel self-capture organic bromine material(1,10-bis[3-(trimethylammonio)propyl]-4,4'-bipyridinium bromine,NVBr4)to successfully realize reversible solid complexation of bromide components for stable non-flow zinc-bromine battery applications.The quaternary ammonium groups(NV^(4+)ions)can effectively capture the soluble polybromide species based on strong chemical interaction and realize reversible solid complexation confined within the porous electrodes,which transforms the conventional“liquid-liquid”conversion of soluble bromide components into“liquid-solid”model and effectively suppresses the shuttle effect.Thereby,the developed non-flow zinc-bromide battery provides an outstanding voltage platform at 1.7 V with a notable specific capacity of 325 mAh g^(-1)NVBr4(1 A g^(-1)),excellent rate capability(200 mAh g^(-1)NVBr4 at 20 A g^(-1)),outstanding energy density of 469.6 Wh kg^(-1)and super-stable cycle life(20,000 cycles with 100%Coulombic efficiency),which outperforms most of reported zinc-halogen batteries.Further mechanism analysis and DFT calculations demonstrate that the chemical interaction of quaternary ammonium groups and bromide species is the main reason for suppressing the shuttle effect.The developed strategy can be extended to other halogen batteries to obtain stable charge storage.

Modeling of an Automatic Optimization System of Cyanide Concentration in Carbon in Leach for Optimal Ore Processing in a Mining Company

The optimization system, which was the subject of our study, is an autonomous chain for the automatic management of cyanide consumption. It is in the phase of industrial automation which made it possible to use the machines in order to reduce the workload of the worker while keeping a high productivity and a quality in great demand. Furthermore, the use of cyanide in leaching tanks is a necessity in the gold recovery process. This consumption of cyanide must be optimal in these tanks in order to have a good recovery while controlling the concentration of cyanide. Cyanide is one of the most expensive products for mining companies. On a completely different note, we see huge variations during the addition of cyanide. Following a recommendation from the metallurgical and operations teams, the control team carried out an analysis of the problem while proposing a solution to reduce the variability around plus or minus 10% of the addition setpoint through automation. It should be noted that this automatic optimization by monitoring the concentration of cyanide, made use of industrial automation which is a technique which ensures the operation of the ore processing chain without human intervention. In other words, it made it possible to substitute a machine for man. So, this leads us to conduct a study on concentration levels in the real world. The results show that the analysis of the modeling of the cyanide consumption optimization system is an appropriate solution to eradicate failures in the mineral processing chain. The trend curves demonstrate this resolution perfectly.

Impact of Selected Processing Methods of High-Level Cyanide in Cassava on Optic Neuropathy in Wistar Albino Rats—An Experimental Study

Background: Cassava tuber crop is a staple food rich in carbohydrates and utilized in various forms by millions of Nigerians. The storage root of the cassava contains linamarin, a cyanogenic glycoside that is easily hydrolyzed to release cyanide salt compounds which is toxic to the nervous system especially the optic nerve, sometimes leading to optic neuropathy and visual impairment. Aim: The aim of this study is to find out the impact of selected processing methods of high-level cyanide in cassava on optic neuropathy in Wistar albino rats. Methodology: Twenty-four Wistar albino rats were fed with different concentration and duration of predetermined high-cyanide content cassava root cultivar which was processed using different processing methods adopted by various communities in Rivers State, Nigeria (for human consumption). A control group of 3 Wistar albino rats was fed with normal “Growth Mesh” meals. The pre and post weights of the animals and the fundoscopic optic nerve status of the rats were evaluated after 30 and 60 days. SPSS Version 25 was employed for descriptive and inferential statistical analyses. A p-value of ≤0.05 was considered statistically significant. Results: The Cassava species available in Rivers State have high cyanide content (2336.79 mg CN-/kg dry weight of cassava). There was statistically significant reduction in the cyanide content (p = 0.000) depending on the various common processing methods (into garri for human consumption): 24 hours, 48 hours, fermentation;with and without red palm oil additive. The individual weights as well as the mean weight of the 24 rats in the experimental group increased gradually from the first week to the 9th week with a slight weight reduction on the third and fourth weeks which was not statistically significant (p = 0.092). However, there was a steady increase in the weights of the animals in the control group throughout the 9 weeks. Varying degrees of optic neuropathy occurred, worse with the rats that had 24-hour fermented cassava twice daily for 60 days. The intra and inter group differences in the optic disc changes was statistically significant (p = 0.000). Conclusion: Longer duration of processing cassava roots into garri for human consumption reduces its cyanide content and minimizes the adverse impact on the optic nerve.

Investigation on a Non-cyanide Plating Process of Ni-P Coating on Magnesium Alloy AZ91D

In this research we presented a non-cyanide plating process of Ni-P alloy coating on Mg alloy AZ91D. By applying a new process flow of electroless nickel plating in which zinc coating is used as transition of Ni-P coating on Mg alloy AZ91D, the process of copper transition coating plated in the cyanides bath can be replaced. A new bath composed of NiSO4 was established by orthogonal test. The results show that zinc transition coating can increase the adhesion and protect the Mg alloy substrate from the bath corrosion. The optimal plating bath composition is NiSO4·6H2O 20 g/L, NaH2PO2·H2O20g/L and C6H8O7·H2O 2.5 g/L, and optimal bath acidity and optimal plating temperature are pH 4.0 and 95℃, respectively. The present process flow is composed of ultrasonic cleaning→alkaline cleaning→acid pickling→activation→double immersing zinc→electroplating zinc→electroless nickel plating→passivation treatment. The present non-cyanide process of electroless nickel plating is harmless to our surroundings and Ni-P coating on Mg alloy AZ91D produced by present process possesses good adhesion and corrosion resistance.

Zincate mechanism on cast Al-Si alloy in non-cyanide multi-metal zincate solutions

Arrhenius formula was applied to calculate the apparent activation energy of zincate reaction. The standard electrode potential of all the metal coordinating ions and the order of galvanic couple of different metals in zincate solution were also calculated. Electrochemical behavior of zincate process was studied by Tafel polarization curves, E—t curves, and electrochemical impedance spectroscopy(EIS). The results show that the apparent activation energy of zincate reaction in non-cyanide multi-metal zincate solution is smaller than that in simple zincate solution, and precipitation sequence of all the metals in zincate solution is Cu, Ni, Fe and Zn. Relationship between the potential at 30 s before zincate and coverage was attained according to the change of potential of zincate. EIS shows that inductive reactance is produced during zincate.

Selective removal of nickel from iron substrate by non-cyanide strippers

A novel nickel stripper using ammonia as the key component was developed to substitute cyanide for removing nickel film from iron substrates. Its compositions are: ammonia 150 g/L, hydrogen peroxide 50 g/L, ammonium chloride 100 g/L, EDTA 7.5 g/L, copper chloride 15 g/L and glucopyrone 1.2 g/L. The optimum operating conditions are: pH 9.511, temperature 4050 ℃ and stripping time 1 h. It shows many advantages over the traditional cyanide stripper including no toxicity, mild operation, lower cost, larger holding capacity, faster stripping rate and good protection for the base metal, and can meet the technical requirements in industry.

Effect of non-cyanide zincation process parameters on the microstructure of the zincation layer on A356 alloys

The effects of non-cyanide zincation process parameters on the microstructure of the zincation layer on A356 alloy were investigated by scanning electronic microscope.With the increasing of zincation time,the zinc grain size and the number density increase gradually,and the zinc grains adhere each other.The zinc grain obtained in the double-dipping process is finer,compacter and more homogeneous than that obtained in the single-dipping process.With the increasing of the zincation temperature,the morphology of zinc grains changes from spherical shape to flake-like shape.However,higher zincation temperature results in the flaking off of the zincation layer from the matrix.The optimized zincation temperature is 20-30 ℃.The quality of the zincation layer obtained in a low concentration,non-cyanide and multi-element zincation solutions is much better than these obtained in conventional high concentration zincation solution,dilute zincation solutions or a dilute zincation solution containing nickel.In addition,the matrix alloy and the pre-treatment also have significant influence on the morphology of the zincation layer.

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.

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.

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.

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.

Highly active double metal cyanide complexes: Effect of central metal and ligand on reaction of epoxide/CO2

Various novel double metal cyanide （DMC） catalysts were successfully prepared by modifying the central metal （M） and one of cyanide ion （CN-） in Zna[M（CN）b]c complex. Such modifications have significant impact on the catalytic efficiency as well as the polymer selectivity for the reaction of PO/CO2. Zn-Ni（Ⅱ） DMC is a potential catalyst for alternating copolymerization of PO/CO2,and DMC catalysts based on Zn3[Co（CN）5X]2 （X = Br^- and N3^-） exhibit moderate efficiency for the production of polycarbonates.This research presents the preliminary exploration of novel DMC complex via chemical modification of its central metal and ligand.

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.

Effect of Pre-treatment of α-Ketoglutarate on Cyanide-induced Toxicity and Alterations in Various Physiological Variables in Rodents

Objective To investigate the effects of pre-treatment of α-ketoglutarate （α-KG） on cyanide-induced lethality and changes in various physiological parameters in rodents. Methods The LD50 of potassium cyanide （KCN） given orally （po）, intraperitoneally （ip）, subcutaneously （sc） or intravenously （iv） was determined in male mice, in the presence or absence α-KG given po, ip or iv. α-KG was administered 10, 20 or 40 min prior to KCN at 0.50, 1.0 or 2.0 g/kg by po or ip route, and at 0.10, 0.20 or 0.40 g/kg by iv route. Protection index （PI） was calculated as the ratio of LD50 of KCN in the presence of α-KG （protected animals） and LD50 of KCN in the absence of α-KG （unprotected animals）. In a separate experiment, several physiological variables viz. mean arterial pressure （MAP）, heart rate （HR）, respiratory rate （RR）, neuromuscular transmission （NMT） and rectal temperature （RT） were measured in anesthetized female rats pre-treated （-10 rain） with po （2.0 g/kg） or iv （0.125 g/kg） α-KG and then administered sub-lethal （0.75 LD50） or lethal （2.0, 4.0 or 8.0 LD50） doses of KCN （po）. Results PI of 4.52, 6.40 and 7.60 at -10 min, 3.20, 5.40 and 6.40 at -20 min, and 1.40, 3.20 and 5.40 at -40 min of po administration with α-KG was observed for 0.50, 1.0 and 2.0 g/kg doses, respectively, against KCN given by po route. When KCN was given ip, a PI of 3.38, 4.79 and 5.70 was observed for 0.50, 1.0 and 2.0 g/kg α-KG given ip （-10 min）, respectively. A lower PI of 3.37, 2.83 and 2.38 was observed when KCN given sc was challenged by 2.0 g/kg α-KG given ip at -10, -20 or -40 min, respectively. Similarly, a PI of 3.37, 2.83 and 2.0 was noted when KCN given sc was antagonized by 2.0 g/kg α-KG given po at -10, -20 or -40 rain, respectively. No appreciable protection was observed when lower doses of α-KG （ip or po） challenged KCN given by sc route. Pre-treatment of iv or po administration of α-KG did not afford any protection against KCN given po or iv route. Oral treatment of 0.75 LD50 KCN caused significant decrease in MAP and HR after 15 min, RR after 30 min and NMT after 60 min. There was no effect on RT. No reduction in MAP, HR, RR and RT was observed when rats received 2.0 or 4.0 LD50 KCN after pre-treatment of α-KG （po; 2.0 g/kg）. However, no protection was observed on NMT. Protective efficacy of α-KG was not observed on MAP, HR, RR, and NMT decreased by 8.0 LD50 KCN. Decrease in MAP and NMT caused by 2.0 LD50 KCN （po） was resolved by iv administration of α-KG Conclusions Cyanide antagonism by α-KG is best exhibited when both α-KG and KCN are given by po route. The protective effect of α-KG on cyanide-induced changes in several physiological parameters also indicates a promising role of α-KG as an alternative cyanide antidote.

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.

Study on Gold (Ⅰ) Solvent Extraction from Alkaline Cyanide Solution by TBP with Addition of Surfactant

The new solvent extraction system for gold() from alkaline cyanide solution by TBP with addition of surfactant in aqueous phase was studied. The effect of various factors, such as equilibrium pH, constitution of organic phase, molar ratio of CPBAu(CN)2-, extraction time, aqueous/organic phase ratio, different initial gold concentration, equilibrium temperature, different diluent, different types of extractants and surfactants etc., was inspected. The results show that gold() can be extracted quantitatively by controlling the quantity of surfactant (CPB); both the equilibrium pH and diluent hardly influence percent extraction. Gold() percent extraction reaches more than 98% under the optimal experimental conditions. 30% vol TBP diluted by sulphonating kerosene can load gold() to rather high levels. Loading capacity is in excess of 38 g/L. The extraction mechanism is discussed and the overall extraction reaction is deduced.

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.

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.