Zinc Cyanide Complex Research Articles

A new strategy for extraction of copper cyanide complex ions from cyanide leach solutions by ionic liquids

Copper cyanide complexes in cyanide leach solutions deteriorate the recoveries of gold. Herein, five phosphonate-based [P204]− ionic liquids were synthesized, which were pioneered to apply to extraction of copper cyanide complex ions in cyanide leach solutions. In the extraction process, macroscopic layered solids rich in copper cyanide complex ions were formed at the aqueous-organic phase interface, which was driven by self-assembly of ionic liquids. Notably, the layered solids can be obtained by simple filtration. The extraction behaviors were systematically studied in the present work. The results show that the extraction efficiency in excess of 90 % can be achieved at higher pH (13.16) and enriched as self-assembly solids in the process of one-step extraction and solidification, based on the self-assembly extraction systems of [P4444][P204] IL. It is worthy of note that no self-assembly sample was observed when the extraction systems is applied to extraction zinc and iron cyanide complex ions. It indicates that the present self-assembly extraction systems could be applied in separation copper and zinc/iron cyanide complex ions. Meanwhile, the coordination mechanism was investigated detaily, and the covalent nature played a leading role in the binding interaction. Remarkably, [P4444][P204] can be repeatedly used without obvious loss in extraction capacity of copper cyanide complex ions after two cycles, indicating that the IL has a good recycling ability. In conclusion, it is possible to employ the self-assembly extraction systems to separate and recover various valuable metals from aqueous solutions by designing and developing ILs extractants in the future.

Study on electrosorption behavior of weak metal cyanide complex ions based on coal-based electrode

Using the electrosorption technology treatment the cyanide wastewater has a good treatment effect, but the mechanism is not completely clear. In this paper, we conducted electrosorption experiments using simulated cyanide solutions to study the adsorption kinetics, thermodynamics, adsorption isotherms and analyze the reaction mechanism of zinc-cyanide and copper–cyanide complex ions. The results show that the electrosorption process of weak metals cyanide complexes treated by coal-based (CB) electrode conforms to the second-order kinetic model and follow the Langmuir model, affected by the dipole force and exchange of coordination groups. The equilibrium adsorption amounts of the two species at 2 V were 1.53 and 1.74 times higher than those at open circuit, respectively. During the electrosorption process, affected by the pseudo-capacitance, pore structure of CB electrodes and the charges of complex ions, the zinc-cyanide complex is bound in the double electric layer on the anode surface by the electric field, but partly decomposed to produce zinc ions and forms Zn(OH)2 in alkaline solution then generates ZnO precipitates, a small amount of Zn2+ were electrostatically adsorbed on the cathode surface for reduction deposition. However, the majority of the copper–cyanide complexes were purified by electrostatic adsorption to the double layer near the anode, while a small amount of decomposition occurred to produce Cu(OH)2 in the alkaline system, and almost no copper was deposited by reduction. This research results can enable us to better understand the removal characteristics of the weak metal cyanide complex ions in the process of electrosorption by CB electrode, and have great significance for the application of electrosorption technology to the treatment of cyanide wastewater.

Removal of metal ions from cyanide gold extraction wastewater by alkaline ion-exchange fibers

The metal cyanide complex ions of gold extraction wastewater consume extra cyanide and compete with gold for adsorption on activated carbon during wastewater recycling. Therefore, the removal of metal cyanide complex ions from gold extraction wastewater is of great significance. In this study, polypropylene (PP) fibers were used to prepare strong acylated alkaline ion-exchange fibers (SAA-IEFs) using a polymer graft monomer method that achieved excellent adsorption of metal cyanide complex ions from gold extraction wastewater. The properties of the SAA-IEFs were characterized via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). Adsorption experiments were conducted to study the adsorption performance and to verify the adsorption mechanism. The results show that the highest adsorption efficiencies of the SAA-IEFs for zinc and copper cyanide complex ions were 85.5% and 91.2%, respectively, and these performances were obtained when the SAA-IEF concentration was 50 g/L and pH was 10. The adsorption efficiency of the cyanide complexes in practical wastewater reached 92% at a concentration of 30 g/L. The desorption and regeneration results indicate that the adsorption capacity of the SAA-IEFs remained high after nine cycles. Moreover, an adsorption mechanism is proposed, and the adsorption process is best modeled using the Freundlich isotherm and pseudo-second-order kinetic model. These results indicate that chemisorption plays a dominant role in the adsorption process. Overall, SAA-IEFs are a promising, efficient, and cost-effective adsorbent for metal cyanide complex ion adsorption from gold extraction wastewater.

Zinc cyanide removal by precipitation with quaternary ammonium salts

In gold-processing plants, the final tailing containing metal cyanide species is typically treated using various oxidation methods to produce the main source of process water, which is subsequently recycled to the upstream units, such as flotation units. In some gold-processing plants, a considerable amount of metal cyanide species such as zinc cyanide remains in process water, despite the cyanide destruction process. Because residual zinc cyanide complexes can depress gold flotation, the amount of process water must be decreased such that it can be recycled to a flotation circuit. Previous studies report that the critical concentration of zinc cyanide, measured based on the total cyanide concentration during flotation depression, is 0.4 mmol/L. In the present study, the feasibility of using quaternary ammonium salts to precipitate zinc cyanide complexes to less than the critical concentration was studied. The results showed that 92.17% of 60 mg/L of cyanide and 88.86% of 50 mg/L of zinc (molar ratio Zn/CN = 1:3) can be removed using 0.4 g/L of octadecyl trimethyl ammonium bromide at a pH of 10. The concentration of the residual CN cyanide was less than the critical concentration. This indicates that the abovementioned process is effective when nonpolar organic contaminants and moderate amounts of salt (<50 mmol/L) are present. This work revealed that the precipitation process can be used as an advanced treatment method for process water subjected to oxidation treatment.

Enhanced photocatalytic reaction and mechanism for treating cyanide-containing wastewater by silicon-based nano-titania

The treatment of cyanide-containing wastewater is very important for the sustainable development of gold industry. Treating wastewater by nano-titania (nano-TiO2) has the advantage of adsorbing heavy metals and catalyzing the decomposition of cyanogen simultaneously. Since the catalysis is limited by solid-liquid diphase system, the photocatalytic and adsorption efficiency is relatively low. This study aimed to enhance catalytic process based on silicon-based nano-TiO2 composite functional material to treat deeply cyanide-containing wastewater. The characteristics of the silicon-based nano-TiO2 material were studied by Brunner−Emmet−Teller (BET) and field emission scanning electron microscopy (FESEM)/ energy dispersive spectrometer (EDS), which indicated that the material has excellent dispersibility and large specific surface area(146.6±2.4 m2·g−1). Further, the comparison of the treatment effects of cyanide wastewater with pure nano-TiO2 and silicon-based nano-TiO2 material demonstrates that the latter is more effective on cyanide degradation. Almost 99.8% of cyanide degradation was achieved by silicon-based nano-TiO2 material under light irradiation within 135 min. The mechanism and X-ray photoelectron spectroscopy (XPS) analysis. It was found that the final decompositions of Copper cyanide complex and zinc cyanide complex are CO2, NO2, Cu2+ and Zn2+.

A sensitive photoluminescent chemosensor for cyanide in water based on a zinc coordination polymer bearing ditert-butyl-bipyridine.

Sensitive and direct sensing of cyanide in buffered aqueous solutions at pH = 7.0 by three new blue photoluminescent zinc-1,4-cyclohexanedicarboxylato coordination polymers bearing di-alkyl-2,2'-bipyridines has been achieved. Specifically, a Zn-polymer with the general formula: {[Zn2(H2O)2(e,a-cis-1,4-chdc)2(4,4'-dtbb)2]·7H2O}n, (1,4-chdc = 1,4-cyclohexanedicarboxylato and 4,4'-dtbb = 4,4'-ditert-butyl-2,2'-bipyridine) has been synthesized in high yield and studied as a luminescent chemosensor for halides, pseudohalides and a series of oxyanions in neutral water. CN- ions can be quantitatively detected by this polymer based on complete quenching (λem = 434 nm) in the sub-micromolar concentration range with a pronounced selectivity over common anions such as acetate, bromide and iodide. The quenching response (KSV = 9.7(±0.2) × 104 M-1) by the addition of CN- was also observed in the presence of typical interfering anions with a very low detection limit of 0.9 μmol L-1 in buffered water at pH = 7.0. On the basis of the crystal structure and solid state CPMAS 13C-NMR correlation and 1H NMR, IR-ATR, MS-ESI(+) and SEM-EDS experiments, the optical change is attributed to the efficient release of its corresponding ditert-butyl-bipyridine, with the simultaneous formation of a zinc cyanide complex. The CPMAS 13C-NMR spectrum of the coordination polymer is consistent with the symmetry of the crystal structure. The use of flexible coordination polymers as fluorescent sensors for fast and selective detection of cyanide ions in pure aqueous solutions has been unexplored until now.

Density functional theory study of cyanide adsorption on the sphalerite (1 1 0) surface

Cyanidation tailings in gold plants often contain lots of sphalerites that are difficult to recycle by flotation because of the strongly depressive effect of the residual cyanide. To reveal the depression mechanism of cyanide on sphalerite, the adsorption of isolated cyanide molecule (CN) at different coverages on the sphalerite (1 1 0) surface were studied by means of density functional theory. The calculated results show that the adsorption energy of per CN molecule drops as the increase of adsorbed CN molecule coverage, indicating that the adsorption structure becomes more thermodynamically stable. Cyanide molecule adsorption on sphalrite (1 1 0) surface prior occurs on the atop site of surface Zn atom, in which the Zn 3d orbital donates electrons to the 2p orbital of C forming a d-p back donating bond, leading to the production of hydrophilic zinc cyanide complexes that serve as strong obstacles to the flotation recovery of sphalerite in cyanidation tailings. Electron transfer from mineral surface to the adsorbed CN molecules takes place during the process of CN adsorption, and the surface atoms lose more electrons when the coverage of adsorbed CN molecules is high, weakening the reactive activity of Zn and S atoms on the sphalerite (1 1 0) surface.

Изучение прооксидантных свойств цианидных комплексов цинка (II) в эксперименте

The aim of this paper is to study the toxic effects of zinc compounds and cyanide ions on the system of lipid peroxidation and antioxidant defence. Studies were conducted on 24 rats of Wistar line, divided into three groups (control group and two experimental, having received respectively 0.1 mg / kg of zinc chloride and cyanide complexes of zinc, calculated on the Zn2+). It was found that the administration of cyanide complexes of zinc leads to the increased level of lipid peroxidation products (methaemoglobin, hydroperoxide) on the background of the decreased activity of ceruloplasmin. In addition the content of malon dialdehyde and catalase activity does not undergo significant changes.

Removal of cyanide and zinc–cyanide complex with malachite green functionalized amberlite XAD-4 resin from electroplating wastewater

A new chelating resin was prepared by coupling Amberlite XAD-4 with malachite green through an azo spacer, and it has been used for the removal of cyanide and zinc from electroplating wastewater. The resulting chelating resin was characterized by elemental analysis, thermogravimetric analysis and infrared spectra. The effect of pH, electrolytes, and foreign ions was evaluated on the efficiency of cyanide removal, and some eluents were considered for the regeneration of synthesized resin. For the initial 200 mg L−1 cyanide solution, the packed bed gave a cyanide effluent concentration of 0.2 mg L−1 at 110 bed volume and in the mixture of 200 mg L−1 cyanide and 100 mg L−1 zinc. The packed beds were exhausted at 185 bed volumes. In order to validate the methodology, the proposed method was applied to electroplating wastewater for the removal of cyanide and zinc. Wastewater was analyzed, before and after of passing from synthesized resin. The results clearly indicated the success in removing cyanide in wastewater using the chelating process.

Treatment of cyanide bearing effluents by adsorption, biodegradation and combined processes: effect of process parameters

The present investigation focused on a comparative study for the removal of cyanide from separate solutions of sodium, zinc and iron cyanide compounds by three different processes such as; adsorption, biodegradation and simultaneous adsorption and biodegradation (SAB) processes. Adsorption studies were carried out on commercial granular activated carbon (GAC). Biodegradation and SAB studies were conducted with suspended and immobilized cultures of Pseudomonas putida, respectively. Effect of pH, temperature and agitation time on percentage removal of cyanide was measured at an initial cyanide concentration of 100 mg/L and it was found that these parameters significantly affect the three process performances. The SAB process was found to have better removal efficiency as compared to adsorption and biodegradation processes. SAB process could achieve more than 95% removal efficiency for cyanide concentrations up to 100 mg/L in sodium, zinc and iron cyanide solutions. Higher percentage of cyanide removal and specific uptake was achieved in case of zinc–cyanide complexes as compared to other cyanide complexes. Adsorption isotherms evaluated the uptake and degradation on cyanide in SAB process.

Wet oxidation characteristics of metal cyanide complexes below 423 K

In the present study, the wet oxidation of zinc and copper cyanide complexes (cyanide concentration of 1,000 mg dm-3) was conducted in a hydrothermal reactor, under oxygen atmosphere of which the pressure was set to 1 MPa. The pH of the reaction solution was kept in the range of 11 to 12 and the reaction temperature was changed from 383 K to 423 K. In the experiments, mainly the effect of reaction time on the cyanide decomposition was investigated. As a result, it was found that cyanide decomposition increased with an increase in the temperature and cyanide decompositions of 99.9 % and 96.1 % were achieved after 8 hours at 423 K for Na2[Zn(CN)4] and Na3[Cu(CN)4], respectively. In the case of Na2[Zn(CN)4], mainly HCOO- and NH4+ were identified as the decomposition products. By contrast, in the case of Na3[Cu(CN)4], carbon of CN- was transformed either to H2CO3 or HCOO-, and nitrogen was converted to NH4+, N2 or NO2-. Based on these results, the decomposition mechanisms of Na2[Zn(CN)4] and Na3[Cu(CN)4] at a temperature of 423 K and pressure of 1 MPa were discussed.

Copper cyanide removal by precipitation with quaternary ammonium salts

Cyanide is widely used in the mining industry to extract gold from ores. Some of the minerals processed for precious metals extraction contain copper species which may react with cyanide to form cuprocyanide complexes. The presence of these copper species affects adversely the process and causes high cyanide consumption. In order to overcome these limitations this laboratory work explores the feasibility of removing the copper–cyanide complexes by precipitation with quaternary ammonium salts, allowing the remaining solution, free of copper and containing free cyanide, to be recycled to the cyanidation process. The first part of the experimental work was performed with synthetic copper–cyanide solution simulating a high copper–cyanide solution (2700mg/L cyanide, 730mg/L copper and pH adjusted to 12 with CaO) and three quaternary ammonium salts: hexadecyl trimethyl ammonium chloride (HTA), octadecyl trimethyl ammonium chloride (OTA) and dioctadecyl dimethyl ammonium chloride (DDA). The results showed that it is possible to remove up to 90% of the copper in the precipitate when adding 12.32g OTA/g copper at pH 12. The free cyanide remains unreacted in the solution and could be recycled to the process. Results of tests performed at different pH values suggest that regardless the initial species distribution in the solution, the solid formed will contain mainly copper tricyanide and some of copper tetracyanide. The molar ratio CN/Cu in the solid is around 3 while the molar ratio OTA/Cu is around 2. This implies that some amount of copper tetracyanide is transformed into copper tricyanide while reacting with the amine and forming the precipitate. When zinc is also present in the cyanide solution, the ammonium salt will react first with the zinc–cyanide complexes before precipitating the copper cyanides. Tests performed with an industrial solution corroborated the results obtained with synthetic solutions: quaternary ammonium salts (e.g. OTA) react with copper and zinc cyanides (but not with free cyanide) to form a precipitated that can be separated from the solution by filtration. An analytic technique for measuring quaternary ammonium salts HTA and OTA in solution was developed.

Determination of free cyanide and zinc cyanide complex by capillary electrophoresis

A capillary electrophoretic (CE) protocol was developed for the separation and quantification of free cyanide and zinc cyanide complex, two key species in gold cyanidation of zinc-bearing sulfidic ores. Several common carrier electrolytes were implemented in an indirect UV detection method. The effect of electric field strength, injection volume, concentration of electro-osmotic flow (EOF) modifier and UV-absorbing agent in background electrolyte (BGE) was examined while peak height, peak area and noise were considered for optimization. The best results were obtained using a BGE that contained 35 mM sodium chromate, 12 mM free cyanide and 0.45 mM hexamethonium bromide at pH 10.5. Free cyanide concentration was compared to that measured with the conventional silver nitrate titration method in solutions containing free cyanides and weak cyano-complexes. The developed CE protocol proved very robust in capturing the concentration of free cyanides (4% error) unlike the titration method which exhibited substantial sensitivity to the interfering weak cyano-complexes (38% error).

Structure and stability of neutral cyanide complexes of copper and zinc

A theoretical study of neutral Zn[CN] n and Cu[CN] n complexes has been carried out, as representative examples of cyanide complexes of late transition metals. Both complexes prefer the cyanide arrangement over the isocyanide form, in agreement with the experimental evidence for the monocyanide compounds. The successive complexation energies suggest that the preferred complex in the case of copper is the monocyanide, CuCN, whereas for zinc the most favourable complex seems to be Zn(CN) 2. Both Zn and Cu have preference for low coordination numbers, since mixed complexes with cyanide and cyanogen ligands are preferred over homoleptic M(CN) n complexes for n > 2.

Molecular dynamics simulations of metal–cyanide complexes: Fundamental considerations in gold hydrometallurgy

This study utilizes molecular dynamics simulations (MDS) in order to evaluate the hydration state and the characteristics of metal–cyanide anions in aqueous solutions. Cyanide complexes of gold, silver, zinc, mercury, and copper were examined. Tetracyano anions of zinc and mercury showed the highest level of hydration, whereas dicyano anions of mercury, gold, and silver showed the lowest level of hydration. Several of the cyano anions were found to form clusters in solution. Other species, especially the tetracyano complexes, were found to be well dispersed in water. This MDS information on the behavior of metal–cyanide complex anions may lead to further advances in the understanding of processes being used in gold hydrometallurgy operations. This paper discusses the results from simulations and how these results contribute to a fundamental understanding of carbon adsorption, solvent extraction/ion exchange, and membrane water treatment processes.

Transport of zinc complexes through an anion exchange membrane

The transport of zinc complexes ions through an anion exchange membrane was evaluated by the treatment of solutions with and without cyanide. The ionic transport was analyzed as a function of the applied current density and of the cyanide and hydroxyl concentration. Experimental results showed that the ionic transfer in electrodialysis was mainly affected by concentration. There is an ideal molar relationship among the concentration of the cyanide ions, hydroxyl and zinc ions, in solution, in which the zinc transport is maximized. For values above or below this, the transport decreases. Zinc extraction from solution containing CN − was more effective when the current density of 29 mA.cm −2 was applied. The current–voltage curves (CVC) of the anion exchange membrane show that the electrical resistance of the AMV membrane increases with the presence of the zinc–cyanide complex in the solution.

Removal of Cyanide and Zinc–Cyanide Complex by an Ion-Exchange Process

Removal efficiencies of cyanide and a zinc–cyanide complex in solutions were studied by using an ion-exchange process at pH 10.0 and 12.0. An anion-exchange resin, AMBERLITE® IRA-402 Cl, was used to perform packed bed continuous experiments. For the initial 200 mg/l cyanide solution, the packed bed gave a cyanide effluent concentration of 0.2 mg/l at 80 bed volumes for both pH 10.0 and 12.0. Comparatively, in the mixture of 200 mg/l cyanide and 100 mg/l zinc, packed bed volumes were obtained as 80 and 90 at pH 10.0 and 12.0, respectively, to have 0.2 mg/l cyanide effluent concentrations. The packed beds were exhausted at 250 and 400 bed volumes for cyanide and zinc–cyanide complex solutions, respectively. Speciation calculations in Zn(II)/cyanide/OH− were used to interpret the results. The exchange capacities of the resin were determined as ∼1.2 and ∼0.9 meq/ml resin for cyanide and zinc–cyanide complex solutions, respectively, and were independent of pH in the studied pH range.

Decomposition behavior of zinc and copper cyanide complexes by wet oxidation at lower temperatures

Decomposition behavior of zinc and copper cyanide complexes by wet oxidation at lower temperatures

The elution of metal cyanocomplexes from polyacrylic - and polystyrene- based ion exchange resins using nitrate and thiocyanate eluants

Ion exchange resins can potentially be applied in cyanide recycling to address growing environmental concerns over the use of cyanide during gold extraction. In the present work the elution of copper-, iron-, and zinc-cyanocomplexes from polyacrylic- and polystyrene-based resins was studied. It was found that iron and copper cyanides are easily eluted from polyacrylic- and polystyrene-based ion exchange resins using either SCN- or NO3-. However, elution of the zinc cyanide complex from polystyrene-based resins was poor when using nitrate solution as eluant. Besides, an increase in elution temperature from 25 °C to 50 °C improved the elution of iron and zinc cyanides from polystyrene-based resins using a nitrate eluant; however temperature did not have any significant effect on other metal cyanocomplexes or for elution using thiocyanate. It was therefore proposed that the optimal combination of resin-eluant was site-specific, and depends on the features of the effluent, processing temperature, eluant concentration, and ion exchange resin under consideration.

Ferrate(VI) oxidation of zinc–cyanide complex

Zinc–cyanide complexes are found in gold mining effluents and in metal finishing rinse water. The effect of Zn(II) on the oxidation of cyanide by ferrate(VI) ( Fe VI O 4 2 - , Fe(VI)) was thus investigated by studying the kinetics of the reaction of Fe(VI) with cyanide present in a potassium salt of a zinc cyanide complex (K 2Zn(CN) 4) and in a mixture of Zn(II) and cyanide solutions as a function of pH (9.0–11.0). The rate-law for the oxidation of Zn ( CN ) 4 2 - by Fe(VI) was found to be - d [ Fe ( VI ) ] / d t = k [ Fe ( VI ) ] [ Zn ( CN ) 4 2 - ] 0.5 . The rate constant, k, decreased with an increase in pH. The effect of temperature (15–45 °C) on the oxidation was studied at pH 9.0, which gave an activation energy of 45.7 ± 1.5 kJ mol −1. The cyanide oxidation rate decreased in the presence of the Zn(II) ions. However, Zn(II) ions had no effect on the cyanide removal efficiency by Fe(VI) and the stoichiometry of Fe(VI) to cyanide was approximately 1:1; similar to the stoichiometry in absence of Zn(II) ions. The destruction of cyanide by Fe(VI) resulted in cyanate. The experiments on removal of cyanide from rinse water using Fe(VI) demonstrated complete conversion of cyanide to cyanate.