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By K. J. R. Ford, Botz. M. M.

Porphyry copper ores are frequently a source of low-grade gold ore, but gold in these ores is often associated with significant levels of cyanide-soluble copper. Cyanide leaching of such ores increases flowsheet complexity and operating costs, and requires thorough planning to satisfy environmental requirements for tailings disposal and mine closure. This paper presents a review of the chemistry of cyanide leaching of gold-copper porphyry ores, carbon adsorption phenomena and means of removing base metals from leach solution. The primary economic drivers behind the processing of such complex ores are also analyzed.

Jan 1, 2011

By Janene Barter

Telfer Gold Mine treats both gold/copper oxide and sulfide ores in a remote location in the Great Sandy Desert, Western Australia. Currently, the oxide gold ore is treated in a conventional CIL circuit by blending the low and high grade copper ores to minimise cyanide consumption and allow smooth operation. The sulfide ore is treated through a flotation circuit to produce pyrite and copper concentrates. The pyrite concentrate is treated in the CIL. Copper concentrate is stockpiled and sold to a smelter for further processing. In recent times, as the depth of the pit has increased the copper head grade has also increased, to the point where the ore was becoming uneconomical to treat. In addition, it was desirable to reduce the amount of cyanide reporting to the tails dam both from an environmental and economical viewpoint. Newcrest Mining Limited engaged GRD Minproc Limited to evaluated a process to reduce the amount of cyanide entering the tail dam with consideration given to copper recovery. From this investigation, the Sulfidisation, Acidification, Recycle and Thickening (SART) process was selected. A detailed testwork program for SART was undertaken with the objective to design and construct a SART plant at Telfer. This paper outlines how the SART process was chosen and summarises the testwork that led to the design of the SART plant. It also touches on some of the important issues for designing this type of process.

Jan 1, 1998

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide 'a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction' behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of ' the cyanide behavior.

Jan 1, 1998

By Artem Dolotov, Alexander Ter-Oranesyants, Saveliy Kaplan, Boris Axenov, Vasiliy Kovalev, Valeriy Tsyplakov, Konstantin Grigorjev, Nikolai Vorob’ev-Desyatovskii

The issues of double refractory gold ores pressure oxidation were considered. It was demonstrated that along with chloride autoclave preg-robbing which has been studied there are other negative external and intra-autoclave processes resulting in gold losses. It was found that an ingress of even low concentrations of NaCN, ferrum(II) and ferrum(III) cyanide complexes, as well as thiocyanate compounds into the autoclave leads to decrease of gold recovery during further cyanidation in a "carbon in leach" process (CIL). Admixtures depressing recovery of gold can get into the autoclave together with water in the result of industrial accidents or due to peculiarities of recirculation of industrial water used for feed pulp preparation or with quench-water used for process temperature maintenance. In contrast to a chloride preg-robbing which occurs only at pressure oxidation of double refractory gold ores, cyanide preg-robbing starts in the autoclave feeding tank (so-called «upper» preg-robbing). Possible causes of cyanide autoclave preg-robbing and requirements to the quality of water supplied to autoclaving were discussed.

Jan 1, 2014

By Jose R. Parga

In mining operations, cyanidation is the ,predominant method by which gold and silver are recovered from their ores and it is recognized that cyanide consumption can be a major factor that contributes to the operating costs for such operations. Also after extraction and recovery of precious metals a certain amount of cyanide is delivered to the tailings pond and must be considered with respect is environmental problems due to the toxicity of cyanides. In this regard, the Air-Sparged Hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions in two ways; first for cyanide recovery by acidulation using the Mexican modification of the Mills-Crowe process and second for cyanide destruction by oxidation with the use of chlorine dioxide (ClO2). In both cases, excellent performance can be achieved using the high capacity ASH system.

Jan 1, 1998

By Dean Lindsay, Inna Dymov, Mariam Melashvili, Jim Smolik, Chris Fleming

"This paper presents results from the proposed cyanide detoxification circuit for Seabridge Gold’s KSM project. The proposed flowsheet uses a two-stage CCD (counter-current washing/decantation) circuit to transfer the flotation products CIL(carbon-in-leach) barren solution to a SART process (Sulphidization, Acidification, Recycling of precipitate, and Thickening of precipitate) to recover copper and free cyanide from the copper cyanide complex. The SART barren solution is then treated by an AVR process (Acidification, Volatilization of HCN gas, and Reneutralization) to concentrate the cyanide that was liberated in SART for recycling to leach. The washed CIL barren pulp (the CCD underflow) is treated with the SO2 /Air process to oxidize residual cyanide.The goal of this complex flowsheet is to recover and recycle as much cyanide as possible and produce a final effluent containing less than 0.5 mg/L copper and CNWAD at the lowest cost. The SO2/air process is capable of achieving low residual CNWAD (<1 mg/L) in the final product, but the persistence of aqueous copper above the target level has been detected in the treated solution in some instances. The expected high concentrations of copper and cyanide in the KSM CIL barren ( >200 mg/L each species) and the difficulties this might create for the SO2 /air process was a key factor in the decision to consider including the washing, SART and AVR steps in the project flowsheet.The target concentrations of CNWAD and Cu were readily achieved after aging the SO2 /air treated pulp, as would occur in a tailing or polishing pond. This suggests no additional treatment will be required to sustain low levels of these species in the final plant effluent."

Jan 1, 2015

By M. Hames, K. Larmour-Ship, B. Grinbaum, E. Buchalter, R. Hackl, B. Wassink

Sodium cyanide continues to be the lixiviant of choice for gold dissolution. Many gold ore-bodies contain a significant amount of cyanide-soluble copper which increases the cost of processing due to high cyanide consumption and high cyanide destruction and disposal costs. Several cyanide destruction processes are in use today, however, there are just a few cyanide recovery plants operating. A solvent extraction process to recover cyanide has been developed which utilizes the organophosphorous extractants Cyanex 923, di-butyl-butyl-phosphonate (DBBP) or tri-n-butyl phosphate (TBP) in Bateman Pulsed Columns. Copper cyanide species are first converted to hydrogen cyanide (HCN) by acidification, with or without sulfide addition. HCN is extracted by the organic and stripped using a suitable base (eg. NaOH) resulting in a high strength cyanide solution (eg. NaCN) for recycle to the gold recovery process. Continuous pilot plant testwork on HCN extraction using a 40 mm diameter Bateman Pulsed Column demonstrated a cyanide recovery of greater than 99% with final levels of cyanide in solution of less than 10 ppm. These results illustrate the potential of this technology to recycle cyanide and to detoxify final effluent streams.

Jan 1, 2005

By C. A. Fleming, K. W. Sarbutt, P. K. MacPhail

The SART process has been developed for Teck to treat bar­ren solution from the cyanidation/CIP process that has been developed for the Lobo-Marte project in Chile. The objective of the process is to recover cyanide in a form that is suitable for recycling to the leaching part of the process. The Marte and Lobo ore bodies require a dosage rate of about 2 kg/t NaCN, of which only 0.5 kg/t is truly consumed (as thiocyanate, cyanate and ferrocyanide species). The remaining -1.5 kg/t is present as cop­per cyanide (-1 kg/t) and free cyanide (-0.5 kg/t), and is poten­tially recoverable and recyclable. SART is an acronym that describes the unit operations in this cyanide recovery process; namely, .. Sulphidization .. Acidification .. Recycling of precipitate " Thickening of precipitate The basic chemistry has been applied previously, and has also been the subject of two patents (American Cyanamid Company, 1965, Potter et al., 1986). The process involves the conversion of all free and WAD cyanide in solution to hydrocyanic acid by acidification of the tailings solution to pH :s,4, and the conversion of all copper in solution to cuprous sulphide (synthetic chal­cocite) by the addition of a sulphide salt:

Jan 1, 1998

By P. A. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The recovery of cyanide from a gold mill solution containing high levels of copper (400 mg/L to 900 mg/L) using the AVR process was evaluated. It was determined that acidification to pH 2 to 3 provides a suitable balance between HCN generation, copper precipitation and acid consumption. A short pilot plant campaign showed that ~75% of the feed WAD cyanide was recovered while the remainder precipitated along with copper upon acidification. The acid consumption averaged 3.5 g H2SO4 per litre of solution. The copper precipitate, consisting mostly of CuCN and CuSCN, was readily separated from the solution by gravity. The volatilization of HCN in countercurrent packed columns averaged 98.7% efficiency. Reabsorption of HCN was practically 100% in NaOH solutions and slightly lower in a lime slurry. Basic volatilizer design parameters applicable to a large-scale operation were determined, including the Henry’s Law constant and the mass transfer coefficient of HCN gas.

Jan 1, 1998

By H. Soto, J. Jara, F. Nava

A method has been developed to recover cyanide and copper from cyanidation effluents contaminated with thiocyanate and copper-cyanide complexes. Copper is precipitated as copper thiocyanate or as copper cyanide depending on pH and the concentrations of thiocyanate and cyanide present in the effluent. The copper precipitate presents good dewatering characteristics and can be easily separated from the effluent by thickening and filtration. The solution containing the bulk of the cyanide is then oxidized with ozone to transform the remaining thiocyanate into cyanide. This results in a regenerated solution rich in free cyanide that can be recycled to the cyanidation process. Careful control of the pH of the solution is required. First pH of the effluent is lowered to optimize the precipitation and oxidation stages, then the pH is restored to an alkaline value to regenerate the cyanide solution. Recoveries of over 96% copper are obtained. Free cyanide in the regenerated solution corresponds to up to 160% of the total cyanide contained in the original impure effluent. (The balance being accounted for by the cyanide obtained by the oxidation of thiocyanate). The efficiency of the thiocyanate oxidation stage is 85% to 90%. The method has been demonstrated at bench scale with effluents of various cyanidation plants of northern Quebec. A preliminary economic evaluation indicates that the procedure would be profitable for effluents rich in copper and thiocyanate. This is the case for most barren bleeds of Merrill Crowe and heap leaching operations and also certain CIP tailings of gold ores containing copper impurities. Environmentally the procedure is a better alternative than the current detoxification methods based on the oxidation of cyanide that do not allow for copper recovery and that have difficulties in producing a final effluent with acceptable levels of contaminants such as ammonia, thiocyanate and copper.

Jan 1, 1996

By H. Soto, J. Jara, F. Nava

A method has been developed to recover cyanide and copper from solutions containing copper complexes and thiocyanate. Copper is precipitated as copper thiocyanate or as copper cyanide depending on pH and the concentrations of thiocyanate and cyanide in the effluent. The copper precipitate assays over 50% copper and presents good dewatering characteristics. After settling it can be separated from the effluent by filtration. The solution containing the bulk of the cyanide is then oxidized with ozone to transform the remaining thiocyanate into cyanide. This results in a regenerated solution rich in free cyanide that can be recycled to the cyanidation process. Careful control of the pH of the solution is required. First, pH of the effluent is lowered to optimize the precipitation and oxidation stages, then the pH is restored to an alkaline value to regenerate the cyanide solution. Recoveries of over 96% copper and cyanide were obtained in laboratory tests using industrial solutions. With this procedure, cyanocidic gold/copper ores could be treated economically by heap leaching, since the cyanide consumed by the copper impurities could be regenerated at very low cost (most of the cost of cyanide regeneration would be compensated by the copper credits). In order to achieve this, a bleed of the barren solution could be treated by the proposed method, and then recycled to the leaching step. The volume of solution to be treated should be large enough to keep a cyanide/copper molar ratio higher than 3:1. This would assure that copper does not cause undue interferences in the leaching or the carbon adsorption stages. If the thiocyanate content is low, the oxidation stage can be avoided, and the solution can be recycled to the leaching stage directly after the solid-liquid separation stage.

Jan 1, 1997

By A. V. Faiberg

Currently, the interest to conditioning of cyanide-bearing recycled solutions with high-grade of base metals, in particular, copper has significantly grown. This can be explained by two major factors. Firstly, there are strict regulations on cyanides amount in tails and higher cost of detoxification processes. This problem can be easily solved during the ore treatment using the conditioning of solutions and water recycling. Secondly, the presence of other metals minerals which react with cyanide during gold leaching resulting in high cyanide consumption. The presence of copper is a major problem. Many copper minerals react with cyanide with the formation of cyanide complexes-Cu(CN)2-, Cu(CN)32- and Cu(CN)43-. One mole of copper consumes 2-4 moles of free cyanide. Availability of cyanide-soluble copper minerals has deleterious effect on gold leaching (gold recovery, cyanide consumption, tails detoxification, efficiency of gold elution and electrowinning). The precipitation of copper from the solutions improves gold recovery by CIL. The removal and recycling of cyanide allowed the reduction of cyanide addition to the process. The recycling of spent cyanide-bearing solutions based on the removal of copper and the return of cyanide bound in complex compounds for leaching process is an optimal way of solving the problem of gold-bearing copper ores treatment. By using the technology, an adverse impact onto gold recovery process is eliminated and at the same time reducing the cyanide consumption. Today, processes and methods of high-grade copper leaching solutions conditioning before and after gold recovery have been developed, which combine two ways of copper recovery: as a saleable product and cyanide to recover gold and reduce total operating costs. They are Cutech, MNR, SART, Cyanomet, AuGment, Vitrokele, Hannah and Cyanisorb. At the same time, these technologies have not been studied enough and described in literature. Data on parameters and operating conditions as well as introduction is not available. The conditioning technology of recycled solutions developed by IRGIREDMET JSC allows copper to be recovered as high quality concentrate and at the same time free cyanide regeneration in the recycled solution which is amenable to gold leaching. This technology was commercialized at a mine in Kazakhstan in 2008. The removal and recycling of cyanide does not require additional cyanide and is cost-effective. More cost-efficiency is achievable through selling copper concentrates, closed water cycle without the detoxification of effluents and enhanced gold recovery by CIL and cathode quality.

Sep 1, 2012

By C. W. Lawr

THE ores mined by the Santa Gertrudis Co. at Pachuca, Mexico, are mainly silver-bearing; they also yield some gold and carry a little copper. Strong cyanide solutions are used to dissolve the silver and gold, and the mechanical loss of cyanide at the tailings filter has been considerable. Prior to the year 1923, the pulp, after agitation, was given a 35 to 37-min. wash with barren solution in a Butters-type leaf filter; the discharged slime cake was repulped and pumped into eight Merrill self-sluicing slime presses in which the slime was given a further wash with barren solution for 25 to 35 min., followed by a 10-min. water wash. At that time the barren solution titrated around 0.350 per cent. free KCN and 0.500 per cent. total KCN. (Aero brand cyanide is used.) It can readily be seen that a 10-min. water wash would leave considerable cyanide in the filter cake, which of course was a total loss. This averaged 0.522 kg. (1.15 lb.) KCN per ton of solution. As the daily discharge to. the dam was 1600 tons1 of slime of a 2: 1 ratio of liquid to solid, the value of this mechanical loss of cyanide was an important item and its recovery held alluring possibilities.

Jan 1, 1929

By A. Khodadadi, M. Abdolahi, P. Taimory

Cyanide is used by the mining and chemical industries in tremendous quantities without attention being given to its hazardous properties. The use of cyanide compounds in mining is one of the most important environmental issues for the mining industry due to the acutely toxic properties of many cyanide compounds to humans and aquatic life. Cyanide tends to react readily with most other chemical elements, producing a wide variety of toxic, cyanide-related compounds and because cyanide is carbon based an organic compound it reacts readily with other carbon-based matter, including living organisms. This research is aimed at investigating a feasible and economical technique for the removal of cyanide from tailing wastewater of Muteh gold mine. In this research, removal from Muteh factory&apos;s waste water, was achieved at Tarbiat Modares University&apos;s mineral processing laboratory through the oxidation of cyanide by calcium hypochlorite. Cyanide oxidizes and changes to cyanide (CNO-) which is 1000 times less environmentally hazards than cyanide. Cyanide titration was accomplished using Rhodanine solution and silver Nitrate. Cyanide concentration in the wastewater, was 270 mg/L. Cyanide removal was achieved at an optimum pH of 12.3. However, at higher temperatures, cyanide removal was complete at this pH level. Optimum Dosage for complete removal of cyanide using calcium hypochlorite was 1.43g/L.

Jan 1, 2005

By G. Van Weert, J. F. Breedveld

Both regular and Silver Impregnated Activated Carbon (SIAC) were studied for their effectiveness in removing WAD (Weak Acid Dissociated) cyanides from solutions at pH = 10. SIAC has already been shown to be effective in the removal of free cyanide down to 30 ppb or less. The present work deals with complexed cyanides. Zinc cyanide was used to represent the WAD component. At pH=10, in either batch or column tests it was not possible to lower the total cyanide in solution from either 30 or 8 ppm to less than 1 ppm, using SIAC, regular activated carbon as received, or after grinding. Silver (metal) impregnation of the carbon was not beneficial in the removal of WAD cyanide. However, when silver is added as silver ions (nitrate), the cyanide is adsorbed as silver cyanide in preference to zinc cyanide. The latter compound converts to zinc (hydr) oxide. This way, the cyanide concentration in solution can be lowered below 1 ppm, even when zinc cyanide is already adsorbed on the carbon used. A single exploratory test with added copper ions indicated a similar effect for that system.

Jan 1, 2004

By Charles H. Buclmam

"Environmental regulatory requirements for discharge of solutions and closure of operations for the gold mineral processing industry have been gradually lowered and in certain instances have been targeted to USEP A inorganic drinking water standards for dissolved ions in solution. The use of jar tests for water treatment process development is suitable for preliminary scoping work to be conducted in the research laboratory, as well as for optimization studies at the site of the treatment requirement. This paper will describe experimental methods which were performed using standard jar test equipment in efforts to produce solutions which meet USEP A inorganic drinking water standards after chemical treatment of cyanide solutions. The materials tested included gold bearing pregnant solutions from heap leaching operations, gold plant barren solutions from the Merrill-Crowe zinc cementation gold recovery process and gold heap leach wash solutions after carbon-in-column gold recovery. Experiments included cyanide destruction with sodium hypochlorite and arsenic and selenium co-precipitation coupled with mercury precipitation.IntroductionCyanide leaching solutions are used to selectively dissolve metallic gold from commercially viable mineral deposits. The heap leaching process involves stacking of gold bearing ores on specially designed solution containment pads and percolating alkaline cyanide solutions through the ore to dissolve the gold. Pregnant solutions containing the dissolved gold are collected and sent through a gold recovery process. After selective recovery of the gold, the barren solutions are recycled to the gold extraction process after adjustment of the solution alkalinity and available cyanide concentrations."

Jan 1, 1997

By Kambhampati C. Rao, Cecil Lue-Hing, Nabih P. Kelada, William B. Willborn

improvements in the analytical techniques for cyanide speciation can furnish useful information about the behavior of the different cyanide species in the receiving environment. This could be of help to the environmentally concerned public and the regulatory agencies in the assessment of cyanide limits for effluents, stream quality, and land disposal of cyanide bearing wastes. In addition the ability to distinguish the free cyanide and the weakly bound cyanide from the strong ULTRAVIOLET IRRADIATION UNIT (LAMP, COIU3' HOUSING) FIGURE 1 complexes, as well as transformation to thiocyanate is also needed by different industries, such as mining and metal finishing, etc., to evaluate the efficiency of several processes. Cyanide has been used for the recovery of gold since the late 19th century. Although cyanide leach solutions are mostly recovered and used again, a large quantity of cyanide bearing wastewater becomes unfit for use and has to be treated before it can be released into natural waterways.

Jan 1, 1992

By A. G. Roach

IT IS generally stated that the gold ores of Nova Scotia are free-milling, and for the most part this is true. However, there is a certain proportion of the gold finely disseminated throughout the sulphides, notably arsenopyrite, and this gold is definitely not recoverable as &apos;free-milling&apos; gold by amalgamation. The proportion of free-milling gold to total gold seems to vary widely in different localities in the Province and is lowest in deposits of the fissure-vein type. The problem of recovery of these relatively recalcitrant values is usually one of economics, in some plac.es a simple gravity concentrate being of such low tenor that its extraction and subsequent disposal will not bear the costs involved. In other cases, such a high percentage of values escapes from the mortars and plates that concentration is definitely indicated. The size of the mining operation is also an important factor. In the large majority of cases, however, some concentrating step is warranted, even if the resulting concentrate is stock-piled until sufficient has accumulated to justify further treatment.

Jan 1, 1940

By JIAQI JIN, Joe Milbourne, Maoming Fan

Gold is very important to support the financial system, and to be used in industries of the jewelry, high-tech fields such as electronics and aerospace, etc. Gold is mainly extracted from three types of ores: primary ore (vein gold), placer (alluvial gold) and associated ore. Cyanide was widely used in gold ore flotation to depress gangue minerals and leaching/cyanidation. The process of extracting gold from gold ore, its separation and flotation concentrate, specifically through a technique called cyanidation or cyanide leaching. This method, which has been dominant since the 1970s, utilizes a dilute solution of cyanide to dissolve gold from the ore. While effective, the use of cyanide raises environmental and safety concerns due to its high toxicity. Cyanide spills can have severe environmental consequences. This has led to the exploration of alternative, environmentally friendly reagents. This paper discusses processing results using the alternative flotation depressants such as sodium sulfite (Na2SO3), etc. to produce a goldrich flotation concentrate for sale to a smelter or as feed to an alternative leaching agent. and methods to extract gold from ore without relying on cyanide.

Feb 22, 2026

By Roger L. Beals, George A. Tweedy

I. INTRODUCTION. THE results of the cyanide-operations, given in detail in the following paper, show the progress that is being made at the Minas del Tajo. The old pan-amalgamation process, in operation up to and including 1905, while paying a profit on high-grade ores, was no longer able to treat profitably the ores in sight at that time, hence an alteration in the process was imperative. The success of this alteration is eloquently expressed by the following data Pan- Amalgamation. Cyanidation. 1905. 1907. 1903. Tons treated, . . 51,387 53,983 69,300 Value per ton (U. S. currency),. $10.75 $8.39 $8.28 Extraction, per cent., 65.00 88.50 S7.45 Extraction, per ton. .- $7.00 $7.4.; $7.24 Total cost, per ton treated, 6.50 4.311 4.01 Profit, per ton treated, . . 0.50 3.07 3.23.;

Feb 1, 1910