Gold Cyanide Research Articles

Potassium Amyl Xanthate (PAX) as an alternative organic reactive for mercury removal from cyanidation process of amalgamation tailing.

Mercury is the heavy metal that is most difficult to remove from cyanide solution. This situation brings with it many environmental, health and economic problems. This study aims to effectively utilize xanthate by presenting a new strategy for purifying mercury in the cyanidation process of amalgamation residues. In the study, the removal of mercury by precipitation using PAX from cyanidation leach solutions of a well-characterized amalgamation residue was investigated. The dosage of the precipitation reagent is the most important parameter in the removal of mercury. The mercury removal efficiency increases with the increase in the PAX/Hg ratio, and when the removal ratio is 60, the precipitation efficiency reaches a value of 66.7%. Applying coagulation and flocculation procedures after the precipitation process increases the mercury removal efficiency. It is seen that with this application, mercury can be removed with an efficiency of 95.6% at the same reagent rate. With this application, the particle sizes of the precipitates are enlarged and their filtration properties are improved. It has also been determined that the precipitates formed are in the form of HgS, a stable mercury compound. These results indicate that mercury can be effectively removed in its steady state. It was found that the concentration of Au and Cu did not change significantly, while the concentration of Ag decreased during the precipitation processes.

Cyanide removal of gold cyanide residues by manganese compounds as new decyanation reagents

Plenty of the toxic gold cyanide residues are produced by cyanidation process of gold extraction. As a kind of hazardous solid wastes, cyanide residues must be treated to remove cyanide before disposal. In this study, the removal of cyanide in gold cyanide residues by manganese compounds (KMnO4 and MnO2) was investigated. It was found that both KMnO4 and MnO2 could be used as new decyanation reagents for cyanide removal. To make the residue after cyanide removal meet the national standard, it needed KMnO4 1.8 wt% for 60 min reaction or MnO2 1.0 wt% for 30 min reaction with about pH 8.0. The mechanisms of two processes were investigated by X–ray photoelectron spectroscopy (XPS). The results show that KMnO4 concentrates on the reactions with pyrite in the cyanide residue, the products are mainly Fe(II), Fe(III), SO42− and MnO2. KMnO4 added in the slurry could be consumed by pyrite before oxidation of cyanide, resulting in relatively low cyanide remove efficiency and high KMnO4 consumption. On the surface of the residue after MnO2 treatment, there are mainly pyrite, Fe(II), Mn(II), Fe-CN and CN−, showing that the MnO2 process focuses on the removal of cyanide in the cyanide residue. The MnO2 process has the advantages of low reagents consumption, short reaction time and high cyanide removal efficiency, presenting a promise use for cyanide removal of cyanide residues in a range of applications.

Impacts of cyanide in gold mining and cyanide removal methodologies in liquid waste from gold processing

Cyanide is used in several industries but is widely used for gold extraction due to its ability to complex and stabilize gold ions. The waste generated from this process is of great volume because of low ore grades that requires more processing areas. Also, it is highly toxic due to cyanide being a contaminant of animal life and the environment. The mining sector can recycle the effluents generated in their processes, however, this can affect the gold extraction and treatment methods. There are legal laws that define cyanide levels in effluents for disposal in water bodies. Methodologies for reaching these levels include oxidation degradation processes, physical-chemical, biological processes, adsorption, photocatalysis, among others. In this present review, the use of cyanide in gold mining and some of these methodologies for removing cyanide in effluents generated by gold processing are evaluated.

Study of the Cyanide Leaching of Gold from Low-Grade Raw Materials in the Presence of Amino Acids

The article discusses the interaction in amino acid–gold cyanide systems using amino acids of different structures. The formation of complex compounds of gold cyanide with amino acids with the participation of carboxyl and amino groups is shown. A relationship has been established between the formation of gold complexes with amino acids and the degree of its extraction in the process of leaching from low-grade ore with sodium cyanide together with amino acids: the higher the degree of participation of the amino group in the formation of the complex, i.e., covalent bond, the more pronounced the effect of the amino acid on the degree of gold leaching. The contribution to the formation of the complex of the carboxyl group (ionic bond) and the amino group (covalent donor–acceptor) can be assessed by the intensity of the band at a wave number of 1419 cm−1 of the IR spectra of the systems: gold cyanide–amino acid. This approach makes it possible to predict the effect of amino acid structure on gold recovery during cyanide leaching based on IR spectra.

Operating performance assessment based on stacked performance‐relevant enhanced denoising auto‐encoder for industrial processes

AbstractAs an effective way to ensure the economic benefits of enterprises, process operating performance assessment has attracted more and more attention from industry and academia in recent years. In this paper, a stacked performance‐relevant enhanced denoising autoencoder (SPEDAE) network is designed for the operating performance assessment of industrial processes. Compared to the original denoising auto‐encoder (DAE), each performance‐relevant enhanced denoising auto‐encoder (PEDAE) not only reconstructs the input features in the output layer, but also strives to reconstruct the original input data and the performance grade labels simultaneously. Then the SPEDAE is formed by stacking multiple PEDAEs layer by layer. Through this improved training strategy, SPEDAE can avoid accumulated information loss during the deep feature extraction process, improve the robustness of the network, and extract features closely related to the operating performance, thereby better completing the assessment task. The effectiveness of the proposed assessment method is validated on the case of gold cyanide leaching process. Compared with several methods, the proposed SPEDAE has the highest accuracy and reaches 99.85%, which demonstrates its superiority in operating performance assessment.

Experimenting with Dimethyl Sulfoxide to Leach Gold from a Colombian Artisanal Gold Ore

The diverse uses of gold and its crucial role in the global economy are growing, particularly during cycles of economic crises. The broad use of cyanide by conventional gold-mining companies and mercury by artisanal miners poses environmental and health concerns for local communities. This article introduces an innovative gold-leaching process using a non-toxic organic reagent, dimethyl sulfoxide (DMSO), a water-free lixiviant that extracts gold from ores/concentrates in combination with copper halides. The results of laboratory experiments using dimethyl sulfoxide and a sample of high-grade gold ore from Colombia show that 96.5% of the gold was extracted in 2 h at room temperature. The typical cyanidation process using 5 g/L of CN− at pH 10.5 on the same ore sample obtained 97% gold extraction in 24 h at ambient temperature. The gold extracted using DMSO was precipitated by adding a mild acidic solution, and the reagent can be recycled via distillation and reused in repeating cycles. The results show that DMSO can be used as a promising agent for gold leaching, offering a straightforward, cost-effective, and eco-friendly procedure with minimal chemical waste.

Evaluation of manganese bioleaching and silver extraction in mining tailings by native bacteria using a flooded system

During the silver extraction process in mining, the generated residues (called tailings) still contain approximately 100-140 g/ton of silver due to the presence of refractory materials that trap this metal and prevent its solubilization by conventional methods. These residues can be treated by biohydrometallurgical processes allowing, together with the cyanidation process, an increase in the efficiency of silver extraction by eliminating refractory materials such as manganese, which is present as pyrolusite (MnO2, 3.78 %). Pyrolusite can change from manganese (IV) to manganese (II) when solubilized by bioleaching. This research analyzed the effects of bioleaching using native bacteria on the concentration of silver extraction from the removal of manganese in mining tailings. The native bacteria ITDBC2, ITDBC5, and ITDBC6 were identified as Leptospirillum ferriphilum by amplification of the 16S gene corroborated by bioinformatic analysis. The experimentation was carried out using a flooded bioleaching system (9.43 L) to resemble the industrial geometry with the following variables: concentration of ferrous ions (2, 7, and 14 g/L), pH (2, 4, and 6) and agitation time at 100 rpm (2, 4 and 6 min/day). The experimentation lasted 18 days. The removal of manganese and silver extraction was 71.84 and 55.53 %, respectively. The scaled-up of the evaluated bioprocess could reduce energy consumption and process larger amounts of pulp than the reported at the laboratory scale.

Evaluation of biosorbents as an alternative for mercury cyanide removal from aqueous solution

Worldwide, artisanal gold miners currently use and lose over 2000 t/year of mercury, which causes massive social and environmental problems. The combined use of mercury and cyanide by artisanal processing centers have exacerbated the bioavailability of the pollutant. Biosorbents have the capability to adsorb mercuric species in solution, and due their low cost and extensive availability close to mines, they can be used to detoxify effluents. In this study, four biosorbents were evaluated for mercury cyanide removal from simulated gold mining effluents: banana peel, passion fruit peel, eggshells, and chicken feathers. For each treatment, the adsorption capacity, equilibrium isotherms, and kinetic modeling were studied. Only banana peel showed favorable adsorption of Hg(CN)2, with a 94 % removal percentage within 90 min. The pseudo-first order model resulted in the same adsorption capacity as the experimental data (0.47 mg/g). The Sips isotherm model fitted the experimental data, indicating that the adsorption was monolayer-based. Banana peel was found to be more selective for mercury than for gold cyanide. Conversely, the excess of free cyanide had a negative effect on the adsorption efficiency.

The cyanidation of sub microscopic gold: An experimental and molecular modeling study

Sub microscopic refractory gold ore is an important resource of gold with the depletion of free-milling gold deposits in this century. It has been generally accepted that submicroscopic gold mainly in the form of solid-solution and colloidal particles are physically locked inside mineral phases and impervious to cyanide solution. However, some researches on synthetic nanoparticles show they have very different physical and chemical properties which can affect their dissolution behavior.This research has been conducted to investigate the dissolution behavior of gold sub microscopic particles experimentally and theoretically using density functional theory. For this purpose, 20 nm gold particles have been synthesized and dissolved in cyanide solution under controlled condition. The rate of dissolution has been monitored during cyanidation and compared with a gold disk. The results depict the rate of dissolution per surface area is significantly reduced in gold nanoparticles (30 times, the surface ratio of 14/9 m2/g and 0.006 m2/g in samples is 2500 times smaller while the dissolution rate in nanoparticles is 83 times faster). Also, the smaller nanoparticles have much slower dissolution kinetics than large nanoparticles (5.485 × 10−5 and 4.280 × 10−6 g/m2.s for 16 and 2 nm particles, respectively). Two different dissolution regimes can be identified for >3 nm and < 3 nm nanoparticles. In larger particles, by increasing the number of surface atoms with weaker bond energy and also lower oxidation potential, the dissolution rate increases compared to bulk gold. In nanoparticles smaller than 3 nm, the electrochemical reaction in the cyanide medium is disrupted by the reduction of oxidation potential and decreasing the conductivity as the requirement for electrochemical dissolution of gold in cyanide.The molecular modeling study on the gold clusters of 1 to 20 atom confirm that the oxidation of small clusters of gold is more difficult than bulk gold due to the high ionization energy (9.66 vs. 5.4 eV). Also, the monoatomic gold has a much weaker interaction with cyanide (−4.36 vs. -1.6 eV) and higher interaction with oxygen (−0.64 vs. -0.15 eV) compared to the bulk gold. The HOMO of monoatomic and bulk gold (−9.22 and − 4.5 eV) as well as LUMO of cyanide and oxygen (1.734 and − 4.657 eV), as two reactants in cyanidation process confirm the results based on HSAB theory. As a result, oxygen competes with cyanide for adsorption on the surface of gold nanoparticles, disrupting the first step of electrochemical dissolution of gold, as the adsorption of cyanide and the formation of the Au-CN− complex. This is possible by deactivating the surface by creating a resistant layer of gold oxide or electrostatic adsorption of oxygen on the gold surface and passivating the surface. The modeling data are very well in agreement with the experimental results indicating the inherent inactivity of free surface gold sub microscopic particles during the cyanidation process.

Experimental and molecular modeling investigation on adsorption of gold cyanide complex onto the iron oxide and hydroxide minerals

Complex and refractory gold ores contain high amount of iron oxide and hydroxide minerals, potential adsorbents of gold through preg-robbing phenomenon. In this study, density functional theory (DFT) approach was used to investigate the adsorption of Au(CN)2- complex on hematite, magnetite, and goethite surfaces. The most stable adsorption occurred for goethite when the Au(CN)2- complex was adsorbed from the Au atom along the y axis on the Fe site and the interaction energy was the highest. The following trend was obtained for the preg-robbing potential, which is in good agreement with experiments carried out on synthetic minerals: Goethite > Hematite > Magnetite.

Dissolution of gold in the presence of copper ion and diethylenetriamine (DETA)

ABSTRACT Cyanidation is the most widely used technique for gold extraction worldwide. However, its efficiency in gold extraction has decreased due to gold association with base metals such as copper. Copper is known to form different complexes with cyanide depending on the pulp pH. These Cu-CN complexes deplete the pulp of free cyanide, thereby decreasing gold leaching. The study examined the application of diethylenetriamine (DETA) in cyanidation to minimise copper ions effect on gold cyanidation. Leaching tests performed in the presence of copper ions reduced gold recovery from 93% to 15% at a copper sulphate concentration of 1% and increased cyanide consumption by 10%. The introduction of DETA (between 0.2% and 1%) however restored gold recovery back to normal as the baseline without copper ions and also enabled gold extraction at a reduced cyanide strength. Based on the study, DETA could be used during gold–copper cyanide leaching to minimise the copper ion effect and enhance gold extraction.

Investigation of techniques to replace amalgamation in artisanal gold mining operations

Artisanal gold mining is the leading source of anthropogenic mercury emissions worldwide. This article explores cost-effective gold leaching methods for skilled miners to address mercury's environmental and health impacts in this sector. A sample from Colombia's La Maria deposit, containing 48.87 ppm gold, ground to 80% below 0.13 mm, served as the basis for comparison. The standard whole ore amalgamation approach, commonly used by miners, resulted in less than 19% gold extraction. However, employing cyanidation with 1g/L of free cyanide extracted 84% of the gold within 24 hours. Among the unconventional processes investigated, using effluent from a local cassava processing plant as a lixiviant demonstrated promise. Two cassava varieties produced liquids with 267 and 600 mg/L of free cyanide, leading to 50.9% and 82.4% gold extraction from the ore in 24 hours, respectively. Another alternative method involved employing Dimethyl sulfoxide, a water-free reagent, as a gold-leaching lixiviant, resulting in a remarkable 96.5% gold extraction in just 2 hours. The researchers also modified the Merrill-Crowe cyanidation process by eliminating filtration and vacuum, instead utilizing bags filled with zinc (or aluminum) in the pulp. With reduced agitation to prevent aeration, over 99% of the gold precipitated on the zinc shavings within 2 hours. Furthermore, testing a hydrochloric solution (50%) with an oxidant demonstrated 83.9% and 100% gold extraction in 8 hours at ambient temperature and 50°C, respectively. It is crucial to note that successful implementation of these alternative strategies necessitates knowledge, investment, and customization to suit specific site conditions.

Study on the treatment of cyanide gold extraction wastewater by persulfate-electrochemical oxidation

The cyanide gold extraction wastewater from a gold smelter was treated using a persulfate-electrochemical oxidation (PS-EO) coupling process. The optimal process conditions and significance level of each factor were determined using orthogonal experiments, and the precipitates and cathodic precipitates in the system were analyzed and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), and the oxidation removal reaction mechanism of cyanide was further explored. The results showed that voltage, time and PS concentration were the main influencing factors of the cyanide removal extent. When the voltage was 5 V, PS concentration 0.5 g L–1, pH 7, plate spacing 2.5 cm and reaction time 240 min, the removal extents of total cyanide (CNT), free cyanide (CN–), Cu and Zn ions in wastewater reached 98.33 %, 100 %, 99.53 % and 98.86 %, respectively. The removal of cyanide was mainly attributed to the indirect oxidation by SO4•–, •OH and O2•– active radicals produced by activated PS and the direct oxidation of S2O82–. The contribution rate of S2O82– direct oxidation was 42.38 %. The oxidation contribution rates of SO4•–, •OH and O2•– active free radicals were 15.75 %, 29.33 % and 12.54 %, respectively. Compared with simple PS and EO treatment processes, the PS-EO combined process reduced the amount of oxidants and helped to improve the current density of the system, as well as the generation of active free radicals such as SO4•–, •OH and O2•–. Additionally, after PS-EO treatment, there were almost no precipitates such as Zn(CN)2, CuCN, Zn(OH)2 and Cu(OH)2 produced in the wastewater. The cyanide ions in complex ions such as Cu(CN)32– and Zn(CN)42– were completely oxidized to N2 and CO2, and then under the influence of an electric field, the released Cu2+ and Zn2+ ions were directed to migrate to the cathode and precipitate.Finally, the treated wastewater could be directly returned to the grinding or leaching the ore process, thus achieving the goals of being harmless and utilizing cyanide wastewater resources.

Susceptibility to cyanidation of pyrrhotite-associated gold in pyrite calcines from (non)oxidizing roasting environments

The susceptibility to leaching of pyrrhotite-associated gold in roasted pyrite calcines was studied, with emphasis on the effects of the roasting environment and galvanic contacts under cyanidation conditions. The first part scrutinized the thermal treatment of pyrite under different oxidizing and non-oxidizing atmospheres, and demonstrated that air roasting promoted the coexistence of multiple pyrrhotites, while He, CO2, and steam environments resulted in single hexagonal pyrrhotites with increasing iron deficiency and decreasing porosity. The second part employed a bilayer leach cell to control the electrochemical contacts between gold powder and raw/roasted pyrite during cyanidation, and found that the topology of pyrrhotite and iron oxides was influenced by the type of roasting treatment, which could impact the kinetics of gold dissolution, particularly in cases involving refractory gold or ore preg-robbing recalcitrance. Therefore, when it comes to extracting encapsulated gold associated with refractory pyrite that requires heat treatment, air roasting was the most effective for leaching gold from calcine, outperforming both inert and mild oxidative environments. In addition, the presence of CO2 (and/or moisture) in the roasting atmosphere to mimic the combustion of carbonaceous material could moderately enhance gold recovery regardless of whether or not there was galvanic contact with the roasted pyrite.

Challenges in the determination of total vitamin B12 by cyanidation conversion: insights from stable isotope dilution assays

Previous methods for vitamin B12 (B12) analysis have extensively used cyanidation conversion with the intention of converting all cobalamins to cyanocobalamin (CNCbl) for total B12 determination. This approach has been favored for its advantages in reducing the number of analytes, increasing analyte concentration, and improving analyte stability. However, the present study revealed underlying limitations associated with this approach. First, a stable isotope dilution assay (SIDA) determining total B12 as CNCbl after cyanidation conversion (conversion SIDA method) was developed. Method validation demonstrated good sensitivity, recovery, accuracy, and reproducibility for the target analyte CNCbl. However, subsequent application of the conversion method to real meat samples showed incomplete conversions of cobalamins. These inconsistencies revealed day-to-day variability and reliability challenges associated with the cyanidation process. It was not possible to identify this issue during method validation as CNCbl was spiked as the sole analyte and it requires no further cyanidation conversion. The application of LC-MS/MS enabled the detection of trace amounts of unconverted cobalamins. Nevertheless, this approach remains restricted by instrument sensitivity and stability as well as the performance of immunoaffinity purification for different vitamers. Further development of a reliable monitoring method is a prerequisite for further optimization of the cyanidation process. However, significant improvements of analytical instrumentation in terms of sensitivity and stability are required to overcome the current limitations.Graphical abstract

Study of the basic laws of dissolution of gold and copper in solutions with an ultra-low concentration of sodium cyanide

The work sets out to study the basic physicochemical dissolution patterns of gold, copper, and natural copper-containing minerals (chalcopyrite, bornite and azurite) in solutions with an ultra-low concentration of sodium cyanide (from 0.102∙10-3 to 4.08∙10-3 mol/L). The influence of various factors on the rate of dissolution of Au and Cu in solutions with ultra-low NaCN concentrations was studied by the rotating disk method; for natural copper minerals, the powder diffraction method was used. The concentration of gold and copper in solutions was determined by atomic absorption analysis. The chemical composition of the studied copper minerals was determined using the X-ray phase method, while the specific surface of the minerals was detected using a laser granulometer. The process of gold dissolution is shown to proceed in both diffusion and kinetic regions. In the diffusion region, the rate constant was 0.334∙10-6 L∙cm-2∙s-1/2∙rad-1/2; in the kinetic region – 0.919∙10-6 L∙cm-2∙s-1/2. The calculated value of the apparent activation energy for the diffusion region was 22.5 kJ/mol; for the kinetic region – 40.1 kJ/mol. The addition of glycine to a solution with an ultra-low concentration of sodium cyanide is shown to increase the specific dissolution rate of gold by 1.2 times: from 0.692∙10-9 to 0.82∙10-9 mol/cm2∙s. The process of copper dissolution is shown to take place in the diffusion r egion. The rate constant was 0.496∙ 10-6 L∙cm-2∙s-1/2∙rad-1/2 at an activation energy of 17.0 kJ/mol. With a fractional supply of sodium cyanide, the dissolution rate of copper minerals is reduced by 10–30% compared to a single load. The calculated apparent activation energy values for chalcopyrite, bornite, and azurite were 22.03, 24.2, and 24.1 kJ/mol, respectively. Thus, the use of ultra-low concentrations of NaCN in the process of cyanidation of gold and copper has a positive effect, which can be used i n the processing of gold-copper raw materials to significantly reduce the consumption of sodium cyanide.

Rapid photocatalytic gold recovery from industrial cyanide-based gold plating wastewater via TiO2/WO3 nanocomposites: Role of mixed hole scavengers and operating conditions

A rapid photocatalytic gold recovery from the industrial cyanide-based gold plating wastewater was carried out via TiO2/WO3 nanocomposites synthesized by hydrothermal method. Effects of different weight ratios of TiO2 and WO3 in nanocomposites, types of hole scavenger (Na2S2O3, C2H5OH, Na2S2O3/C2H5OH), concentrations of Na2S2O3 (0–100 mM) and photocatalyst loading (1–4 g/L) were examined. The preliminary results demonstrated that the employed wet chemical process induced a well formation of TiO2/WO3 nanocomposites with better textural properties as well as a more negative band position than the pristine WO3. The presence of mixed hole scavengers of Na2S2O3 and C2H5OH played a crucial role on the photocatalytic gold recovery from the cyanide-based gold plating wastewater. A more stable form of gold cyanide ([Au(CN)2]-) was altered to a less stable form ([Au(S2O3)2]3-) by the addition of Na2S2O3. At the end, approximately 85.9 % and 98.2 % of gold were respectively recovered within 180 and 300 min via the T6/WO3 nanocomposite in the presence of 10 mM Na2S2O3 and 20 vol% C2H5OH at photocatalyst loading of 2 g/L and light intensity of 3.20 mW/cm2. The photocatalytic gold recovery was significantly improved via the 1st reused T6/WO3 nanocomposite, in which 99.9 % of gold was recovered within 180 min. The obtained results can pave the way for the design of novel TiO2/WO3 nanocomposites for gold recovery as well as the strategy of waste management for the practical operation.

Experimental Study on Desulfurization and Ceramic Tile Preparation of Gold Cyanide Tailing

Desulfurization and ceramic tile preparation of gold cyanide tailing have been carried out. A novel oxidant DDTQ has been successfully applied to collaborative decyanation and desulfurization. The removal efficiency of cyanide ions can exceed 99%, and the reduction rate of pyrite and chalcopyrite can be achieved above 90% at the same time with wet oxidation process. Ceramic tiles have been successfully prepared by adding sulfur fixing agent composites during the firing process. The fixing mechanism of residual sulfur after oxidative desulfurization has also been proposed.

Removal of Cyanide in Gold Cyanide Residues through Persulfate-Advanced Oxidation Process

The toxic cyanides in gold cyanide residues produced in the cyanidation process of gold extraction threaten environmental safety and inhibit the recovery of valuable metals. In this study, the removal of cyanide through the persulfate-advanced oxidation process was investigated, and heat activation and ultrasonic activation were tested for cyanide removal. The results showed that cyanide in cyanide residue could be removed by 2.0 wt.% potassium persulfate at pH 10.0 after 60 min reaction with a removal efficiency of 53.47%. The removal efficiency increased to 62.18% at T = 60 °C for heat activation and 74.76% with an ultrasonic power of 100% for ultrasonic activation. The cyanide content in the toxic leaching solution of the residue after the ultrasonic-activated persulfate-advanced oxidation process (3.84 mg/L) reached the national standard of China. Two kinds of free radical scavengers, tert-butanol and methanol, were used to investigate the generation of free radicals. The results showed that both SO4•− and HO• were produced and accelerated the oxidation of cyanide, and HO• played a major role under alkaline conditions. According to XPS analysis, the oxidation of ultrasonic-activated persulfate focused on cyanide removal rather than pyrite in cyanide residue. More cyanides were transferred from the cyanide residue to the liquid phase, leading to the high efficiency of ultrasonic activation. The ultrasonic-activated persulfate-advanced oxidation process has potential application prospects for the treatment of gold cyanide residues.

The Molecular Sieve Effect in the Adsorption of Gold Cyanide on Carbon Adsorbents

The Molecular Sieve Effect in the Adsorption of Gold Cyanide on Carbon Adsorbents