The increasing amount of cyanided tailings produced as a by-product has gained significant attention in recent years because of the rapid development of the gold industry and extensive exploitation of gold mineral res...The increasing amount of cyanided tailings produced as a by-product has gained significant attention in recent years because of the rapid development of the gold industry and extensive exploitation of gold mineral resources. The effective use of these secondary resources is becoming an important and urgent problem for all environmental protection staff. Manganese-catalyzed ozonation for the pre-oxidation of cyanided tailings was studied and the effects of Mn2＋dosage, initial sulfuric acid concentration, ozone volume flow, temperature and agitation speed on pretreatment were examined. The optimum reaction conditions were observed to be： ore pulp density 2.5%, agitation speed 700 r/min,temperature 60°C, Mn2＋dosage 40 g/L, ozone volume flow 80 L/hr, initial sulfuric acid concentration 1 mol/L, and reaction time 6 hr. Under these conditions, the leaching rate of Fe and weight loss could reach 94.85% and 48.89% respectively. The leaching process of cyanided tailings by Mn2＋/O3 was analyzed, and it was found that the leaching of pyrite depends on synergetic oxidation by high-valent manganese and O3, in which the former played an important part.展开更多
A process for treating cyanide tailings was proposed.The process essentially implicates reduction smelting which involves volatilizing silver,lead,and zinc in the cyanide tailings at high temperatures.Meanwhile,gold a...A process for treating cyanide tailings was proposed.The process essentially implicates reduction smelting which involves volatilizing silver,lead,and zinc in the cyanide tailings at high temperatures.Meanwhile,gold and copper combine with the reduced iron to form a metal phase,allowing for the simultaneous recovery of polymetallic elements.The experimental results indicate that the process works optimally with a coke powder of 7.5 wt.%,an alkalinity of 1.0,a melting temperature of 1450℃,and a melting time of 60 min.Under these conditions,more than 99% of gold,77% of copper and 94% of iron are incorporated into pig iron.In the meantime,the volatilization rate of silver exceeds 90%,while lead and zinc are essentially completely volatilized.The primary component of the by-product smelting slag is akermanite,which exhibits lower leaching toxicity than the national standard and belongs to general solid waste.Additionally,taking the trapping process of iron to copper as a case study,the mechanism of iron trapping is methodically examined and divided into three processes:smelting reduction,migration capture,and condensation deposition.展开更多
About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our resea...About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our research group has designed and constructed the world’s first blast furnace gas desulfurization pilot plant with the scale of 2000 Nm^(3)/h in October 2021.The pilot plant is a two-step combined desulfurization device including catalytic hydrolysis of carbonyl sulfur(COS)and absorption-oxidation of H_(2)S,continuously running for 120 days.In the hydrolysis system,one reason for catalyst deactivation has been verified from the sulfur deposition.HCN in blast furnace gas can be hydrolyzed on the hydrolysis catalyst to produce the nitrogen deposition,which is one of the reasons for catalyst deactivation and has never been found in previous studies.The deposition forms of S and N elements are determined,S element forms elemental sulfur and sulfate,while N element forms-NH_(2)and NH_(4)^(+).In the absorption-oxidation system,the O_(2)loading and the residence time have been optimized to control the oxidation of HS^(−)to produce elemental sulfur instead of by-product S_(2)O_(3)^(2−).The balance and distribution of S and N elements have been calculated for thewholemulti-phase system,approximately 84.4%of the sulfur is converted to solid sulfur product,about 1.3%of the sulfur and 19.2%of N element are deposited on the hydrolysis catalyst.The pilot plant provides technical support formulti-pollutant control of blast furnace.展开更多
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 ...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.展开更多
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 cente...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.展开更多
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 wat...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.展开更多
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...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.展开更多
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 remova...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.展开更多
Large amounts of cyanide tailings are produced during the cyanidation process in gold extraction,which are hazardous solid wastes due to the toxic cyanide.Pyrite is one of the main minerals in cyanide tailings.The rem...Large amounts of cyanide tailings are produced during the cyanidation process in gold extraction,which are hazardous solid wastes due to the toxic cyanide.Pyrite is one of the main minerals in cyanide tailings.The removal of cyanide adsorbed on pyrite by H_2O_2 oxidation under alkaline conditions was investigated in this study.It was found that the removal efficiency was positively correlated with pH from 5 to 12,but remained almost constant when pH was higher than 12.The highest cyanide removal efficiency of 91.10% was achieved by adding no less than 0.6 wt.% of H_2O_2.Cyanide removal was positively correlated with the CN^-adsorption amount between 1.06 and 8.5 mg/g,and temperature between 25 and 85°C.The removal of cyanide adsorbed on pyrite by H_2O_2 oxidation under alkaline conditions was due to the oxidation of pyrite.Hexacyanoferrate,thiocyanate and sulfate were generated with mole ratios of about 2.03:1.12:3.17 during the cyanide removal.?2018 The Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences.展开更多
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...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.展开更多
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 result...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.展开更多
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 cyanid...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.展开更多
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...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.展开更多
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 concentrati...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.展开更多
Metal （Cu, Co, or Zn） loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide （HCN） toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly wh...Metal （Cu, Co, or Zn） loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide （HCN） toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The Nls XPS data and FT-IR spectra indicated that CN- would be formed in the presence of Cu＋/Cu2＋ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN.展开更多
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...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.展开更多
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 exam...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.展开更多
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 w...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.展开更多
Cyanide(CN−)is extensively used in the process of plating devices and for surface treatment in the electroplating industry and is extremely hazardous to humans and the environment.Peroxymonosulfate(PMS)-based advanced...Cyanide(CN−)is extensively used in the process of plating devices and for surface treatment in the electroplating industry and is extremely hazardous to humans and the environment.Peroxymonosulfate(PMS)-based advanced oxidation processes(AOPs)hold considerable promise for CN−removal.However,the activity of sulfate radical and hydroxyl radical generated in the PMS activation process is low in the base condition,leading to a drop in its efficiency in CN−removal.Thus,a photo-electrocatalytic system(PEC),developed using a TiO_(2) photoanode and a carbon aerogel cathode,was used to activate PMS for the removal of CN−from wastewater through the generation of radicals and non-radicals.The PEC/PMS system could effectively remove CN^(−),with the removal efficiency reaching 98.5%within 2 min,when PMS concentration was at the 0.25 mmol/L level,and the applied bias voltage was-0.5 V.The main active species in the PEC/PMS system were superoxide radicals and singlet oxygen,which was proved through electron paramagnetic resonance detection and quenching experiments.Results obtained through in-situ Raman measurements,photocurrent tests,and electrochemical impedance spectroscopy measurements indicated that the TiO2 could activate PMS to generate active species.Following many cycles of experimentation,it was discovered that the system displayed high catalytic performance and possessed satisfactory stability to remove CN−economically and efficiently.展开更多
Because of the highly toxic cyanide in the gold cyanide residues,cyanide must be removed for environmental protection.The process mineralogy of residues was studied firstly,and then cyanide removal was carried out by ...Because of the highly toxic cyanide in the gold cyanide residues,cyanide must be removed for environmental protection.The process mineralogy of residues was studied firstly,and then cyanide removal was carried out by three chemical methods.The results showed that the residue mainly contained Si,S and Fe.Pyrite was the main metallic mineral,and the iron-complex cyanides make cyanide removal difficult.The minerals in residues were in ultrafine particle size with high monomer dissociation degrees.In H_(2)O_(2)oxidation process,the self-decomposition and side reactions resulted in high consumption of H_(2)O_(2).In Na_(2)S_(2)O_(5)-air oxidation process,the time for complete process was long because of the reactions between Na_(2)S_(2)O_(5)and O_(2).Na_(2)SO_(3)oxidation method was found to be a new method for cyanide removal without air inflation device.The cyanide content was reduced to the national standard level in 90 min at pH 9.0 with optimum Na_(2)SO_(3)dose of 2.0 g/L.展开更多
基金supported by the Innovation Foundation of Donghua University for Doctoral Candidates (No. BC201132)the Shanghai Leading Academic Discipline Project (No. B604)
文摘The increasing amount of cyanided tailings produced as a by-product has gained significant attention in recent years because of the rapid development of the gold industry and extensive exploitation of gold mineral resources. The effective use of these secondary resources is becoming an important and urgent problem for all environmental protection staff. Manganese-catalyzed ozonation for the pre-oxidation of cyanided tailings was studied and the effects of Mn2＋dosage, initial sulfuric acid concentration, ozone volume flow, temperature and agitation speed on pretreatment were examined. The optimum reaction conditions were observed to be： ore pulp density 2.5%, agitation speed 700 r/min,temperature 60°C, Mn2＋dosage 40 g/L, ozone volume flow 80 L/hr, initial sulfuric acid concentration 1 mol/L, and reaction time 6 hr. Under these conditions, the leaching rate of Fe and weight loss could reach 94.85% and 48.89% respectively. The leaching process of cyanided tailings by Mn2＋/O3 was analyzed, and it was found that the leaching of pyrite depends on synergetic oxidation by high-valent manganese and O3, in which the former played an important part.
基金supported by the National Key R&D Program of China(No.2020YFC1909203)the Hunan Provincial Innovation Project,China(No.CX20230213)。
文摘A process for treating cyanide tailings was proposed.The process essentially implicates reduction smelting which involves volatilizing silver,lead,and zinc in the cyanide tailings at high temperatures.Meanwhile,gold and copper combine with the reduced iron to form a metal phase,allowing for the simultaneous recovery of polymetallic elements.The experimental results indicate that the process works optimally with a coke powder of 7.5 wt.%,an alkalinity of 1.0,a melting temperature of 1450℃,and a melting time of 60 min.Under these conditions,more than 99% of gold,77% of copper and 94% of iron are incorporated into pig iron.In the meantime,the volatilization rate of silver exceeds 90%,while lead and zinc are essentially completely volatilized.The primary component of the by-product smelting slag is akermanite,which exhibits lower leaching toxicity than the national standard and belongs to general solid waste.Additionally,taking the trapping process of iron to copper as a case study,the mechanism of iron trapping is methodically examined and divided into three processes:smelting reduction,migration capture,and condensation deposition.
基金supported by the Key Research and Development Program of Hebei Province(No.21373702D)the Key Science and Technology Program of HBIS Group Co.,Ltd.(No.HG2021117)+1 种基金the National Natural Science Foundation of China(No.52370124)the National Key R&D Program of China(No.2023YFC3707003).
文摘About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our research group has designed and constructed the world’s first blast furnace gas desulfurization pilot plant with the scale of 2000 Nm^(3)/h in October 2021.The pilot plant is a two-step combined desulfurization device including catalytic hydrolysis of carbonyl sulfur(COS)and absorption-oxidation of H_(2)S,continuously running for 120 days.In the hydrolysis system,one reason for catalyst deactivation has been verified from the sulfur deposition.HCN in blast furnace gas can be hydrolyzed on the hydrolysis catalyst to produce the nitrogen deposition,which is one of the reasons for catalyst deactivation and has never been found in previous studies.The deposition forms of S and N elements are determined,S element forms elemental sulfur and sulfate,while N element forms-NH_(2)and NH_(4)^(+).In the absorption-oxidation system,the O_(2)loading and the residence time have been optimized to control the oxidation of HS^(−)to produce elemental sulfur instead of by-product S_(2)O_(3)^(2−).The balance and distribution of S and N elements have been calculated for thewholemulti-phase system,approximately 84.4%of the sulfur is converted to solid sulfur product,about 1.3%of the sulfur and 19.2%of N element are deposited on the hydrolysis catalyst.The pilot plant provides technical support formulti-pollutant control of blast furnace.
基金financially supported by the National Natural Science Foundation of China(No.52274348)the Major projects for the“Revealed Top”Science and Technology of Liaoning Province,China(No.2022JH1/10400024)the National Key Research and Development Program of China(No.2018YFC1902002).
文摘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.
文摘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.
基金Projects(ZR2010EL006,Y2007F60) supported by the National Science Foundation of Shandong Province of ChinaProject(J12LA04) supported by High Education Science Technology Program of Shandong Province,China
文摘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.
基金This work was supported by the National Key Basic Research Special Foundation （No.2007CB815202 and No.2009CB220010） and the National Natural Science Foundation of China （No.20833008）.
文摘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.
基金supported by the grant of the Basic Research Program of the Korea Science & Engineering Foundation (No R01-2006-000-10284-0)
文摘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.
基金supported by the National Key Research and Development Program of China (No. 2017YFC0703200)
文摘Large amounts of cyanide tailings are produced during the cyanidation process in gold extraction,which are hazardous solid wastes due to the toxic cyanide.Pyrite is one of the main minerals in cyanide tailings.The removal of cyanide adsorbed on pyrite by H_2O_2 oxidation under alkaline conditions was investigated in this study.It was found that the removal efficiency was positively correlated with pH from 5 to 12,but remained almost constant when pH was higher than 12.The highest cyanide removal efficiency of 91.10% was achieved by adding no less than 0.6 wt.% of H_2O_2.Cyanide removal was positively correlated with the CN^-adsorption amount between 1.06 and 8.5 mg/g,and temperature between 25 and 85°C.The removal of cyanide adsorbed on pyrite by H_2O_2 oxidation under alkaline conditions was due to the oxidation of pyrite.Hexacyanoferrate,thiocyanate and sulfate were generated with mole ratios of about 2.03:1.12:3.17 during the cyanide removal.?2018 The Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences.
基金The Scientific and Technological Research Council of Turkey (TUBITAK) for providing financial support via a S&T research project (Project No. 213M492)
文摘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.
基金Project(51764045)supported by the National Natural Science Foundation of ChinaProject(NJYT-18-B08)supported by Inner Mongolia Young Science&Technology Talent Support Plan,China+1 种基金Project(GK-201804)supported by Research Fund Program of State Key Laboratory of Rare Metals Separation and Comprehensive Utilization,ChinaProject(DD20190574)supported by China Geological Survey Project
文摘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.
基金Project(2019YFC1908400)supported by the National Key Research and Development Program of ChinaProject(2018BDE02050)supported by the Key Research and Development Program of Ningxia Hui Autonomous Region,China+1 种基金Project(2302018FRF-TP-18-095A1)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2018-XY-14)supported by the Special Funds for Scientific and Technological Consultation of Academicians,China。
文摘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.
文摘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.
文摘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.
基金supported by the National Natural Science Foundation of China (No. U1137603,51268021)the Hi-Tech Research and Development Program (863) of China(No. 2012AA062504)the Applied Basic Research Program of Yunnan (No. 2011FB027,2011FA010)
文摘Metal （Cu, Co, or Zn） loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide （HCN） toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The Nls XPS data and FT-IR spectra indicated that CN- would be formed in the presence of Cu＋/Cu2＋ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN.
基金Project(2012BAB08B03)supported by the National Key Technologies R&D Program of China
文摘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.
基金financial supports from the National Key R&D Program of China (2018YFC0604604)the National Natural Science Foundation of China-Yunnan Joint Fund (U1702252)+1 种基金the Fundamental Research Funds for Central Universities of China (N182506003)the Key Scientific Research Project of Liaoning Province,China (2019JH2/10300051)。
文摘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.
基金Project(201552)supported by the Special Project on the Strategic Emerging Industries of Xinjiang Uygur Autonomous Region,ChinaProject(2017SK2254)supported by the Key Research and Development Project of Hunan Province,China。
文摘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.
基金supported by the Key projects of National Natural Science Foundation of China(No. 52030003)the National Key R&D Program of China(No. 2019YFC1407800)sponsored by Joint Doctoral Training Foundation of Hebei University of Technology(HEBUT)
文摘Cyanide(CN−)is extensively used in the process of plating devices and for surface treatment in the electroplating industry and is extremely hazardous to humans and the environment.Peroxymonosulfate(PMS)-based advanced oxidation processes(AOPs)hold considerable promise for CN−removal.However,the activity of sulfate radical and hydroxyl radical generated in the PMS activation process is low in the base condition,leading to a drop in its efficiency in CN−removal.Thus,a photo-electrocatalytic system(PEC),developed using a TiO_(2) photoanode and a carbon aerogel cathode,was used to activate PMS for the removal of CN−from wastewater through the generation of radicals and non-radicals.The PEC/PMS system could effectively remove CN^(−),with the removal efficiency reaching 98.5%within 2 min,when PMS concentration was at the 0.25 mmol/L level,and the applied bias voltage was-0.5 V.The main active species in the PEC/PMS system were superoxide radicals and singlet oxygen,which was proved through electron paramagnetic resonance detection and quenching experiments.Results obtained through in-situ Raman measurements,photocurrent tests,and electrochemical impedance spectroscopy measurements indicated that the TiO2 could activate PMS to generate active species.Following many cycles of experimentation,it was discovered that the system displayed high catalytic performance and possessed satisfactory stability to remove CN−economically and efficiently.
基金financially supported by the National Key R&D Program of China(No.2018YFC1902002)the Special Fund for the National Natural Science Foundation of China(No.U1608254)。
文摘Because of the highly toxic cyanide in the gold cyanide residues,cyanide must be removed for environmental protection.The process mineralogy of residues was studied firstly,and then cyanide removal was carried out by three chemical methods.The results showed that the residue mainly contained Si,S and Fe.Pyrite was the main metallic mineral,and the iron-complex cyanides make cyanide removal difficult.The minerals in residues were in ultrafine particle size with high monomer dissociation degrees.In H_(2)O_(2)oxidation process,the self-decomposition and side reactions resulted in high consumption of H_(2)O_(2).In Na_(2)S_(2)O_(5)-air oxidation process,the time for complete process was long because of the reactions between Na_(2)S_(2)O_(5)and O_(2).Na_(2)SO_(3)oxidation method was found to be a new method for cyanide removal without air inflation device.The cyanide content was reduced to the national standard level in 90 min at pH 9.0 with optimum Na_(2)SO_(3)dose of 2.0 g/L.
