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By Patrick Clark

As part of the Mine Waste Technology Program (MWTP), a large-scale column test using bacteria and a sulfide ore was conducted at McClelland Laboratories, Inc., in Sparks, Nevada. Four technology providers participated in this demonstration. A mining company in Nevada provided the sulfide ore, process effluent and make-up water. A process effluent column, a chemical oxidation column, and the four biological treatment columns were set side by side on a test pad outside the laboratory building. The process effluent and chemical oxidation columns were used for experimental control. The goal of this project was to evaluate the viability and feasibility of using these biodegradation technologies to reduce the cyanide to the regulatory level of 0.2 parts per million (ppm) within an acceptable timeframe and with low operational costs. The column testing began on December 3, 1998 and operated until May 17, 1999. One technology provider reached the regulatory level within the 158 days. The remaining three biotechnology columns were approaching the regulatory limit at completion of the demonstration. The MWTP is funded by the U.S. Environmental Protection Agency (EPA) and is jointly administered through an interagency agreement with the U.S. Department of Energy (DOE).

Jan 1, 1998

By Diane M. Jordan Tom M. Malloy

As part of the Mine Waste Technology Program (MWTP), a large-scale column test utilizing bacteria and a sulfide ore was conducted at McClelland Laboratories, Inc., in Sparks, Nevada. The MWTP is funded by the U.S. Environmental Protection Agency (EPA) and is jointly administered through an interagency agreement with the U.S. Department of Energy (DOE). The project was intended to illustrate the viability and feasibility of biodegradation technologies to reduce the cyanide to the regulatory level of 0.2 parts per million (ppm) within an acceptable time frame and with low operational costs.

Jan 1, 1999

By Schulz R. S, Staunton W. P, McGuire J

The increased activity in the Australian gold industry over the last decade has resulted in a concomitant increase in the use of sodium cyanide, with a projected consumption of 80,000 tonnes per annum by 1991. Growing environmental awareness by government, industry and the public has generated increased interest in the fate of cyanide near gold mine tailings dams and has highlighted the lack of basic knowledge in this area, particularly for Australian conditions.

Jan 1, 1991

By W. P. Staunton, K. Jones

INTRODUCTION The increased activity in the Aus­tralian gold industry over the last decade has resulted in a concomitant increase in the use of sodium cyanide, with a projected consumption of 80,000 tonnes in 1991. Growing environmental awareness by government, industry and the public has generated increased interest in the fate of cyanide near gold mine tailings dams and has highlighted the lack of basic knowledge in the area, particularly for Australian conditions. In 1989 the Chemistry Centre (W.A,) commenced a' project, under the auspices of the Australian Mineral Industries Research Association entitled "Fate of cyanide in the Enviroment Near Mine Tailings" to investigate some of the issues arising from the management of tailings containing cyanide, The project, which has been supported by thirteen companies has three broad aims:

Jan 1, 1991

By James L. Hendrix

This paper is intended to give the reader an update on the work being done at the Mackay School of Mines about the fate of cyanide on precious metals mill tailings waste. During the last two years several tailings impoundments have been sampled and analyzed for total and free cyanides. From our sampling program we are beginning to learn valuable information concerning the fate of cyanides in precious metals mill wastes. Included in this paper is a detailed description of our sampling and analytical techniques. Also, some of the data obtained from five sites are given.

Jan 1, 1986

By Daniel L. Noble

Riparian communities are those related to, or near a natural watercourse (or sometimes of a lake, impoundment, or tidewater). Generally, riparian communities contrast sharply with the dominant vegetation type in an area, for example, the willow-birch-aspen- dominated watercourse in the Black Hills with its associated beaver- muskrat-trout habitat as compared to the dominant monotype ponderosa pine forest on either side of the drainage. Riparian ecosystems are valuable for the aesthetics, namely, varied landscape; photography and art; human awareness; diversity of plant and animal life, some of which may be unique to that habitat; cover, food, and water for associated wildlife and domestic animals; for recreation; for domestic water supply; and as natural outdoor laboratories. One major negative impact on riparian communities is hazardous chemicals from effluents from agricultural, industrial, and mining- metallurgical processes. One such chemical is cyanide, long used in the processing of gold and silver, and discharged previously directly into some of our natural ecosystems. With present environmental awareness, industry and government are attempting to minimize or eliminate this contamination. Homestake Mining Company began processing gold ore in the Lead- Deadwood area of South Dakota in 1878 and has remained in production at variable activity levels to the present time. The amount of cyanide (and heavy metals) entering the ecosystem during this time can only be crudely estimated, in part because of the variability in activity and the lack of understanding and concern about environmental pollution until the 1960's. Whitewood Creek, a tributary of the Belle Fourche River which flows into the Cheyenne River and

Jan 1, 1983

By C. A. Young

Cyanide is a fast-acting, highly toxic substance but, at the same time, is deemed essential for sustaining life as well as our standard of living. In this manuscript, the facts about cyanide are presented beginning with a brief history and definition and ending with a discussion on cyanide alternatives. Other topics include speciation, physical characteristics, toxicity, manufacturing, cyanogenics, cyanide cycle, separation, destruction, and markets including those outside the mining industry. Emphasis, of course, is placed on gold production by leaching and how it is influenced by ore type, mineral characteristics and economics as well as its advantages and disadvantages.

Jan 1, 2001

By P. L. Sibrell

Previous research by the U.S. Bureau of Mines showed that autoclave cyanide leaching of used automobile exhaust catalysts for recovery of platinum group metals (PGM) was technically feasible. This work involves a more detailed investigation of the chemistry of the dissolution of PGM in cyanide solutions. The PGM species in solution identified by ultraviolet spectroscopy. Pt and Pd cyanide complexes were square were The planar in geometry, while the Rh complex was octahedral. The rate of dissolution of the PGM was also investigated using a rotating disk technique. Dissolution rates increased in the order of Rh, pt, and Pd, respectively.

Jan 1, 1994

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 Norman Hedley, Howard Tabachnick

The extraction of gold and silver from ores with alkaline cyanide solutions is well known. Cyanide solutions are also good solvents for many base metal minerals, particularly most of the copper minerals. Leaver and Woolf, who determined the solubilities of copper minerals in 0.10 pct sodium cyanide solution, showed that malachite, cuprite, chalcocite, and bornite are readily soluble in cyanide; least soluble are chalcopyrite and chrysocolla. The Mining Chemicals Laboratory of American Cyanamid Co. has studied the possibilities of using cyanide solutions for leaching base metals. In this article the authors present the results of their experiments with cyanide leaching to reduce the copper content of a zinc concentrate from 0.050 pct to the desired specification of less than 0.02 pct.

Jan 2, 1960

By Dan A. Mackie

Cyanide leaching operations have taken a beating from the press and the public at large for its seemingly haphazard approach to control of cyanide solutions and containment of tailings. Major spills in Colorado, Guyana, Spain, and more recently, Romania, have highlighted what had already been perceived to be a bad scene. Citizen initiatives and legislative actions are increasing. Whether these indictments are justified or not will not be debated in this paper. What this paper presents is that the technology to avoid these disasters and future ones has been around for more than ten years but has been ignored by the industry, despite demonstrated' cost effectiveness. It is time for miners to wakeup, and use emerging, instead of old, technologies.

Jan 1, 1998

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 K. Barbetti, D. C. Wright, L. J. Warren, J. A. Rumball

This paper describes the advantages and disadvantages of cyanide sensors in gold processing operations, and their role in reducing process variability and lowering cyanide consump­tion. The importance of understanding the chemistry of the sensing principle, and the role of impurities, in order to choose the correct sensor setting, is demonstrated.

Jan 1, 1997

By J A. Rumball

Measuring cyanide in the leach liquors associated with high copper and/or sulfide ores is a non-trivial exercise. It is well known that copper complexes with cyanide and reduces the amount of cyanide available for gold leaching. What is not so well known is that the rhodanine end point overestimates the amount of cyanide available for leaching in the presence of copper. Sulfide ions also interfere with a rhodanine end point titration, although this is less of a problem as the black silver sulfide precipitate formed clearly indicates to the operator that something is wrong. Thiosulfate, which forms readily from the alkaline oxidation of sulfides, causes an overestimation of the cyanide available for leaching due to the formation of Ag(S2O3)-. The net result of these observations is that rhodanine is rarely of value as an end point indicator in complex solutions. It generally overestimates the amount of cyanide available, providing plant metallurgists with a false sense of security. Potentiometric titrations are generally much more capable of accurately measuring cyanide in complex solutions. The interfering effect of copper can be resolved and it is even possible to estimate the copper concentration using the inflexions associated with the titration of CN- + Cu(CN)43- versus Cu(CN)32-. Using the potentiometric method sulfide ions can be determined before the cyanide measurement is made due to the formation of AgS2, although the electrode will foul with repeated measurements. Thiosulfate can also be distinguished from cyanide with a potentiometric titration. Rhodanine and potentiometric titrations are both affected by the pH of the liquor. At pH 9.2 half the cyanide will be present as CN- and half as HCN(aq) with only the CN- being titratable. This does not hold in the presence of a buffer active around pH 9. In the presence of sufficient buffer, both the CN- and HCN(aq) are titrated. Ca(OH)+ may buffer the pH when large amounts of lime have been added.

Jan 1, 2007

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 E. A. Devuyst, G. Robbins

A unique process for removing cyanide and base metal complexes from industrial waste streams was patented by G.J. Borberly et al. (1984). The process uses SO2 (liquid or gas, or solutions of sulfite salts, or from burning elemental sulfur), plus air that is dispersed in the effluent using a well agitated vessel. Acid produced in the oxidation reactions is neutralized with lime at a controlled pH generally in the range 7 to 10. The reaction requires the presence of soluble copper as a catalyst which can be supplemented by copper sulfate if necessary. The process can be applied to the detoxification of gold and silver mining waste streams, such as carbon-in-pulp (CIP) tailing pulps, barren solution bleeds, pond waters and heap leach rinse solutions and also to plating shops wastewaters. The SO.jAir process has substantial advantages over two of the main alternative methods of cyanide destruction, namely alkaline chlorination and hydrogen peroxide. Alkaline chlorination is highly penalized in terms of reagent consumption. Chlorine is a strong oxidant reacting with species other than cyanide present in the effluent such as thiocyanate and sulfides. Furthermore alkaline chlorination is an incomplete detoxification process. Iron cyanide is not removed and the potential for harmful by-products species exist. Consequently final effluents may be subject to additional treatment in order to comply with regulatory demands.

Jan 1, 1991

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 D. Kidby, A. Briggs

"Vitrokele ™ is a synthetic adsorbent, using chelating groups on large polystyrene beads, developed in Canada over 7 years ago, and first commercialised in 1985 to recover noxious metals from plating wastes.Pilot plant trials have been performed in Australia and Canada to demonstrate the recovery of cyanide and removal of metal cyanide complexes from gold plant effluent using Vitrokele1 M 912. The pilot plants comprise a simple adsorption train (similar to a CIP circuit) followed by complete elution facilities, so that loaded Vitrokele™ can be stripped and returned to the adsorption circuit.An account of these campaigns is provided, showing the reduction of total CN levels from over 200 ppm to less than 0.5 ppm and Cu levels from approximately 100 ppm to less than 0.3 ppm in treated tailings.Comparisons between pilot plant results and laboratory test data are given and probable future work on the process and its application to the gold mining industry is discussed.INTRODUCTIONThrough millions of years of evolution, life forms have developed specialised molecules with exceptionally high affinity and selectivity for various metals such as iron, cobalt, zinc and copper.In the early 80's professors at the Faculty of Medicine of McGill University engaged in research on the extremely efficient ways that living cells captured trace metals essential for life.As research progressed, it became evident that the special molecules used by biological systems to capture metals could be synthesized to capture selected metals with similar efficiency from water or other solutions.The technology was first commercialised in 1985 to recover noxious metals from plating wastes with compositions applying the special molecules (chelating groups) on vitreous particles (hence Vitrokele™). To date approximately three commercial Vitrokele™ plants have been installed for treating plating waters in Ontario and Quebec."

Jan 1, 1992

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