Article

A New Global Approach of Cyanide Management: International Cyanide Management Code for the Manufacture, Transport, and Use of Cyanide in the Production of Gold

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Abstract

The International Cyanide Management Code was developed to improve the management of cyanide at gold mines. Spills and other incidents involving cyanide solutions at gold mines such as the January 2000 incident at a Romanian gold mine (Baia Mare) demonstrated to the gold mining industry, governments, and the public that better management of cyanide was needed, particularly at operations with limited experience or in countries lacking adequate regulatory programs. In 2001, the Code was underwritten by a group of gold companies and cyanide producers from around the world. The Gold Institute was instrumental in organizing this financial and technical support and provided the administrative and logistical support necessary to successfully complete the project. This effort represents one of practical action that an industry has worked with mining companies and producers including UNEP, World Banks, and Environmental Groups to develop an international voluntary industry Code of Practice.The regional and national environmental management criteria of cyanide are different in various countries. Thus, a common language should be applied as a global perspective which is provided by the Cyanide Code Management. In this review article, a general and brief introduction on Cyanide Code Management is presented.

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... Consequently, several non-cyanide leaching processes (see below) have been developed considering the toxic nature and handling problems of CN -. However, none of them has yet proven more costeffective than cyanide at full-scale operation (Akcil, 2010 ...
... This property gives them an advantage to achieve selective recovery of PGM from waste materials (Serpe et al., 2015). The gold dissolving reaction with chloride and iodine are given below in Equations (2)(3)(4)(5) and (2)(3)(4)(5)(6), respectively: ...
... This property gives them an advantage to achieve selective recovery of PGM from waste materials (Serpe et al., 2015). The gold dissolving reaction with chloride and iodine are given below in Equations (2)(3)(4)(5) and (2)(3)(4)(5)(6), respectively: ...
Thesis
The well-being of the society depends on a number of metals, including base metals, precious metals and increasingly rare earth elements (REE). The usage of these metals increased in numerous applications, including electrical and electronic equipment (EEE), and their interrupted supply is at stake. There is an increasing interest in the secondary sources of these metals, particularly waste electrical and electronic equipment (WEEE) in order to compensate their potential supply deficit. This PhD thesis demonstrates the advantages and bottlenecks of biological and chemical approaches, as well as the advances and perspectives in the development of sustainable processes for metal recovery from WEEE. Furthermore, a novel process for the recovery of metals from WEEE is described, and a techno-economic assessment is given. Discarded printed circuit boards (PCB) from personal computers (PC), laptops, mobile phones and telecom servers were studied. Following an extensive literature review, a novel characterization and total metal assay method is introduced and applied to waste board materials. Discarded PCB contained metals in the range of (%, by weight): copper (Cu) 17.6 - 39.0, iron (Fe) 0.7 - 7.5, aluminum (Al) 1.0 - 5.5, nickel (Ni) 0.2 - 1.1, zinc (Zn) 0.3 - 1.2, as well as gold (Au) (in ppm) 21 - 320. In addition, multi-criteria analysis (MCA) using the analytical hierarchical process (AHP) methodology is applied for selection of the best-suited technology. A proof-of-concept for a two-step bioleaching extraction was given, in which 98.4% and 44.0% of the Cu and Au, respectively, were extracted. The two-step extraction concept was applied to the chemical leaching of metals from PCB. Cu leaching was carried in an acidic oxidative mixture of H2SO4 and H2O2, whereas Au leaching for carried out by S_2 O_3^(2-) in a NH_4^+ medium, catalyzed by CuSO4. Under the optimized parameters, 99.2% and 96.6% of Cu and Au, respectively, were extracted from the board material. Selective recovery of Cu from the bioleaching leachate using sulfidic precipitation and electrowinning was studied. Cu was selectively recovered on the cathode electrode at a 50 mA current density in 50 minutes, with a 97.8% efficiency and 65.0% purity. The techno-economic analysis and environmental sustainability assessment of the new technology at an early stage of development was investigated
... The severity of the environmental incident of Baia Mare led to the implementation of the International Cyanide Management Code (ICMC), developed to improve the management of cyanide at gold mines; the Code was underwritten by a group of gold companies and cyanide producers from around the world (Akcil 2010). The Gold Institute was instrumental in organizing the financial and technical support and provided the administrative and logistical support necessary to successfully complete the project. ...
... The Gold Institute was instrumental in organizing the financial and technical support and provided the administrative and logistical support necessary to successfully complete the project. In this respect, there have been no major environmental incidents at certified sites since 2003 when the ICMC was finally implemented (Akcil 2010). ...
Book
The southeast of Spain is a mythical land for geology in Europe. Its geological marvels include a Miocene volcanic chain, marine sedimentary basins in which were recorded the events of the Messinian Salinity Crisis and the two westernmost metamorphic complexes of the Alpine chain: Nevado Filábride and Alpujárride. This is only “the geology” of this realm, because in relation to the volcanism, important clusters of ore deposits were formed, among them, Rodalquilar (gold), and Mazarrón and La Unión (lead-zinc), which gave rise to famous mining districts. These two new GMMM documents are “teaching field guides”, because the reader will find in them more than just raw data and photos for a “geotour”. The authors go further explaining the regional and local geology, the history of mining and how mining was done, and how the ore deposits were formed, also providing a base for the analysis of the environmental scenario left after mining ceased. https://www.aulados.net/GEMM/Libros_Manuales/Field_Teaching_Guide_Cabo_de_Gata_Rodalquilar.pdf
... Although the use of cyanide is mostly perceived by the general public as being associated with the mining and metallurgical processes, only about 13% of world cyanide production is consumed by these industries with the remaining percentage being used elsewhere (WHO ECEH, 2000;Mudder and Botz, 2001;Mudder et al., 2001a,b;Akcil, 2002Akcil, , 2006Akcil, , 2010Mudder and Botz, 2004). Cyanide is an essential raw material in producing synthetic silk, synthetic rubber and nylon, paints, medical and pharmaceutical products, agricultural products, coloured photographic and television films, and cosmetics (Kirk-Othmer, 2002). ...
... ICMI promotes the adoption of the Code, evaluates its implementation, and manages the certification process. The participation to the Code that exclusively focuses on the safe management of cyanide at gold mines is voluntary (Akcil, 2002(Akcil, , 2010. Since the establishment of ICMI, the Cyanide Code has experienced dramatic growth. ...
... In this process, cyanide reacts with a variety of chemical constituents within the ore, forming chemical complexes which vary widely in their stability and solubility [4]. The major chemical constituents resulting from the cyanidation process are free cyanide, thiocyanate and metal-complexed cyanides, as weak acid (Cu, Cd, Ni, Zn, etc.) and strong acid dissociable cyanides (Au, Ag, Fe, Co, etc.) [5,6]. The prevalence and co-existence of these chemical compounds is harmful to both the environment and living organisms. ...
Article
A microbial consortium which was largely dominated by Thiobacillus sp. and Serratia sp. was evaluated for the biodegradation of thiocyanate (SCN⁻) and free cyanide (CN⁻) under neutral to alkaline conditions, in a two-staged stirred tank bioreactor system operated in series. The bioreactors were operated across a range of residence times (7 d to 24 h), SCN⁻ (100–1000 mg SCN⁻/L) and CN⁻ (200–450 mg CN⁻/L) concentrations at room temperature (21–25 °C). The bioreactors were characterised by high SCN⁻ degradation efficiencies (>99.9%) throughout the experimental run except when the microorganisms were temporarily shocked by a pH increase and the introduction of CN⁻ within the system. Similarly, high CN⁻ biodegradation efficiencies (>99.9%) were observed subsequent to its introduction to the system. Planktonic microbial activity tests by organisms within the bioreactor system revealed high SCN⁻ and CN⁻ degradation efficiencies (>80%); a direct indication of high planktonic microbial activity within the bioreactor system. Furthermore, there was an observed total nitrogen removal by the organisms within the system, which demonstrated the nitrification and denitrification capacity of the organisms while the sulphate concentration increased as a result of SCN⁻ biodegradation, over a period of approximately 300 days. This is the first report on the simultaneous biodegradation of high CN⁻ and SCN⁻ concentrations, coupled with nitrogen removal under alkaline conditions. The results demonstrated the potential of the process to treat CN⁻ and SCN⁻ laden wastewaters.
... Cyanides are discharged by various industries involved in metallurgical processes, e.g. extraction of gold and silver; metal plating and surface finishing; chemical synthesis of nylon, fibers, resins, and herbicides (Botz, Mudder, and Akcil 2005;Akcil 2010); and food industries (Somboonchai, Nopharatana, and Songkasiri 2008;Montagnac, Davis, and Tanumihardjo 2009). They are among the most dangerous compounds and their toxicity is essentially due to their aptitude to release free hydrogen cyanide. ...
Article
This work is devoted to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H2O2 catalyzed by copper-impregnated activated carbon. Effects of initial molar ratio [H2O2]0/[CN−]0, copper-impregnated activated carbon amount, pH and the temperature on cyanide removal have been investigated.The presence of copper-impregnated activated carbon has increased the reaction rate showing thus a catalytic activity. The rate of cyanides removal increases with the raise of the initial molar ratio [H2O2]0/[CN−]0 and decreases with the increase in the pH from 8 to 12. The increase in the copper-impregnated activated carbon amount from 1.5 to 10g/L in reaction solution has a beneficial effect. Beyond this value, the impact of activated carbon amount is not anymore significant. The temperature does not have a significant effect between 20 and 35°C. The four successive times re-use of catalyst shows a good stability. The kinetics of cyanide removal has been found to be of pseudo-second-order with respect to cyanide and the rate constants have been determined. This process seems very interesting because the rate of cyanides removal is very fast, the reaction does not use soluble metal catalyst and it consumes only hydrogen peroxide as chemical product.
... Therefore, there has been a great pressure on producers of gold and silver for the disposal of cyanide wastes from gold and silver plants. Moreover, cyanide is not only employed for gold and silver discharge but also for the discharge of plating and surface finishing [4] [5]. ...
... However the cyanide has been efficient, user-friendly if and only handled carefully obeying all the safety regulations, and economical with the acceptable risk to humans and is preferred over all other non-cyanide lixiviants. It has been observed that 875 gold and silver mines are being operational by the year 2000, where > 90% of gold and silver recovery processes uses cyanide lixiviant (Mudder and Botz, 2004; Akcil, 2010). Out of the total global demand of 360,000 tons of sodium cyanide annually, approximately one-third of the total i.e., 120,000 tons is used potentially for gold and silver recovery. ...
Article
Waste generated by the electrical and electronic devices is huge concern worldwide. With decreasing life cycle of most electronic devices and unavailability of the suitable recycling technologies it is expected to have huge electronic and electrical wastes to be generated in the coming years. The environmental threats caused by the disposal and incineration of electronic waste starting from the atmosphere to the aquatic and terrestrial living system have raised high alerts and concerns on the gases produced (dioxins, furans, polybrominated organic pollutants, and polycyclic aromatic hydrocarbons) by thermal treatments and can cause serious health problems if the flue gas cleaning systems are not developed and implemented. Apart from that there can be also dissolution of heavy metals released to the ground water from the landfill sites. As all these electronic and electrical waste do posses richness in the metal values it would be worth recovering the metal content and protect the environmental from the pollution. Cyanide leaching has been a successful technology worldwide for the recovery of precious metals (especially Au and Ag) from ores/concentrates/waste materials. Nevertheless, cyanide is always preferred over others because of its potential to deliver high recovery with a cheaper cost. Cyanidation process also increases the additional work of effluent treatment prior to disposal. Several non-cyanide leaching processes have been developed considering toxic nature and handling problems of cyanide with non-toxic lixiviants such as thiourea, thiosulphate, aqua regia and iodine. Therefore, several recycling technologies have been developed using cyanide or non-cyanide leaching methods to recover precious and valuable metals. Copyright © 2015 Elsevier Ltd. All rights reserved.
... Cyanide is one of the most dangerous compounds for humans and environment, particularly if it is present in the form of free cyanide and nonstable metal complex cyanide (Weak Acid Dissociable (WAD)). It is discharged by several industries, particularly chemical synthesis plants (nylon, fibers, resins, and herbicides), metallurgical processes (extraction of gold and silver), [1][2][3] or food industries. [4,5] The Algerian standards limits its discharge to 0.1 mg=L in wastewater. ...
Article
Cyanide is considered one of the most dangerous compounds for the environment. They are discharged by various industries: chemical and metallurgical processes (extraction of gold and silver) and food industries. Adsorption is among the most used processes for elimination of cyanides particularly for the low concentrations. In this work, the cyanide removal is carried out by adsorption onto activated carbons prepared from olive stones and coffee ground. So we can promote this by-product as an inexpensive adsorbent. The prepared activated carbons are characterized by scanning electron micrograph and by determination of the physicochemical properties and specific surface area. All the adsorption experiments were performed in batch mode on synthetic water cyanide (KCN) at pH 10.8–11.0 to avoid volatilization of very toxic HCN. To describe the adsorption kinetics, the kinetic models of pseudo-first-order, pseudo-second-order, and intra-particle diffusion were applied. The experimental equilibrium data for adsorption of free cyanide were analyzed by the Langmuir, Freundlich, and Temkin isotherm models.
... En comparación a otras técnicas de extracción de oro desarrolladas a nivel mundial, la extracción por medio de suspensión cianurada es la más segura para la salud humana y la de menor impacto ambiental; siempre y cuando se lleve a cabo de forma adecuada (Ata 2010). Las compuestos cianurados no son persistentes en el ambiente, ya que el cianuro se descompone por acción de la luz solar (Johnson et al. 2000). ...
Thesis
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En el municipio de El Corpus, Choluteca, Honduras; se extrae oro a escala industrial a través de cianuración y a escala artesanal a través de amalgamación con mercurio (Hg). Ambos procesos resultan en impactos ambientales y en la salud de las poblaciones. El objetivo del estudio fue cuantificar y comparar el impacto que ambas actividades mineras tienen en la calidad de agua de la red hidrográfica del municipio. Se recolectaron muestras en época seca y lluviosa en 10 puntos de muestreo ubicados en los ríos El Sabroso y San Juan, ambos tributarios del Río Sampile. Se analizaron parámetros físico químicos a partir de los cuales se compararon las diferencias entre época lluviosa y seca en ambos afluentes y se calculó un índice de calidad de agua. El agua del afluente afectado por minería artesanal está muy contaminada y la del afluente afectado por minería industrial está ligeramente contaminada según las categorías establecidas por el índice. La minería artesanal contamina el afluente debido al vertido de sedimentos y Hg. El Hg detectado se encuentra en el rango de <0.05 a 9103 ng L-1. Los valores máximos superan los de otros estudios similares en la región y se encuentran muy por encima del valor máximo permitido para aguas destinadas a consumo humano. La minería artesanal tiene mayor impacto en la calidad de agua en comparación con la industrial en El Corpus con base en los parámetros estudiados. Es necesario implementar técnicas sostenibles para la mitigación de impactos provocados por la minería artesanal y la realización de estudios complementarios para determinar el impacto en la salud de los mineros.
... deals with the proper management and approval of process certificates for cyanide-utilising industries. Additionally, the ICMC has enforced codes of practice that compel industries to implement alternative waste management practices in order to minimise environmental contamination by such industries (Gibbons, 2005;Akcil, 2002;Akcil, 2010). ...
Article
Full-text available
The cyanidation process has been, and still remains, a profitable and highly efficient process for the recovery of precious metals from ores. However, this process has contributed to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. The process produces numerous cyanide complexes in addition to the gold cyanocomplex. Additionally, the discharge constituents also include hydrogen cyanide (HCN) – metallic complexes with iron, nickel, copper, zinc, cobalt and other metals; thiocyanate (SCN); and cyanate (CNO). The fate of these complexes in the environment dictates the degree to which these species pose a threat to living organisms. This paper reviews the impact that the cyanidation process has on the environment, the ecotoxicology of the cyanidation wastewater and the treatment methods that are currently utilised to treat cyanidation wastewater. Furthermore, this review proposes an integrated biological approach for the treatment of the cyanidation process wastewater using microbial consortia that is insensitive and able to degrade cyanide species, in all stages of the proposed process.
... Cyanide is one of the most hazardous nitrogenous compounds found in effluent of the industries mainly electroplating, coal coking, coal gasification, plastics, steel tempering and metallurgical processes (extraction of gold and silver) (Akcil, 2010;Botz et al., 2004;USEPA, 2000). It is included in the CERCLA priority list of hazardous substances and it occupies 28th position in the list of most hazardous chemicals (ATSDR, 2007). ...
Article
Full-text available
In the present study, Tectona grandis leaves powder has been investigated as a potential bioadsorbent for the removal of cyanide from synthetic wastewater. Effects of significant process parameters on the percentage removal of cyanide are evaluated to get the most suitable operating conditions. Under the optimum conditions; pH 7, contact time 120 min, adsorbent dose 20 g/L; around 86.43% cyanide removal is obtained with the initial cyanide concentration of 100 mg/L. Kinetic evaluation indicates that the adsorption of cyanide ions onto the Tectona grandis leaves powder is best fitted by the pseudo-second order kinetic model. However, it can also be explained by intra-particle diffusion model. The equilibrium assessment illustrates that the Langmuir model is the best fitted model for the experimental data, which attains a maximum adsorption capacity of 18.45 mg/g. Therefore, it seems that the Tectona grandis leaves powder has the potential to be a low-cost bioadsorbent for removal of cyanide from water and wastewater.
... Cyanide is one of the most hazardous nitrogenous compounds found in effluent of the industries mainly electroplating, coal coking, coal gasification, plastics, steel tempering and metallurgical processes (extraction of gold and silver) (Akcil, 2010;Botz et al., 2004;USEPA, 2000). It is included in the CERCLA priority list of hazardous substances and it occupies 28th position in the list of most hazardous chemicals (ATSDR, 2007). ...
Article
Full-text available
In the present study, Tectona grandis leaves powder has been investigated as a potential bioadsorbent for the removal of cyanide from synthetic wastewater. Effects of significant process parameters on the percentage removal of cyanide are evaluated to get the most suitable operating conditions. Under the optimum conditions; pH 7, contact time 120 min, adsorbent dose 20 g/L; around 86.43% cyanide removal is obtained with the initial cyanide concentration of 100 mg/L. Kinetic evaluation indicates that the adsorption of cyanide ions onto the Tectona grandis leaves powder is best fitted by the pseudo-second order kinetic model. However, it can also be explained by intra-particle diffusion model. The equilibrium assessment illustrates that the Langmuir model is the best fitted model for the experimental data, which attains a maximum adsorption capacity of 18.45 mg/g. Therefore, it seems that the Tectona grandis leaves powder has the potential to be a low-cost bioadsorbent for removal of cyanide from water and wastewater.
... In recent years, cyanide use for extraction of gold and silver from primary sources has come under scrutiny due to the environmental impact and human health concerns associated with accidental release and containment in tailings facilities (Akcil 2010). Many alternative chemicals have been proposed as technically viable alternatives, including chlorides, thiocyanate, and thiosulfate (Hilson and Monhemius 2006). ...
Article
Full-text available
Thiosulfate is a lixiviant with potential applications for extraction of precious metals with lower environmental impact. As an alternative leaching reagent to cyanide, thiosulfate has promising gold extraction efficiency with much lower risk to operators and the environment. Thiosulfate is often produced at high temperatures via processes utilizing sulfide or sulfur and an oxidant. However, certain microorganisms can produce thiosulfate as the final product of their metabolism. This represents potential for lower emissions and costs in the manufacture of gold leaching reagents. Biotechnological applications of these processes have not been reported in the past and need to be investigated in depth. This review serves as a study of microorganisms to collect and analyze the reported species for potential utilization of biogenic thiosulfate in industrial applications, with a specific focus on precious metals extraction. Bacteria were identified and compared with respect to thiosulfate producing ability, feasibility for the mining industry, and cost of substrates. The future applications of biogenic thiosulfate and further direction of research on the topic have been identified.
... Consequently, several non-cyanide leaching processes (see below) have been developed considering the toxic nature and handling problems of CN − . However, none of them has yet proven more cost-effective than cyanide at full-scale operation (Akcil, 2010). Montero et al. (2012) studied column leaching of metals from discarded PCB using cyanide in a semi-continuous system. ...
Article
The wealth of the society depends on several metals, including base metals, precious metals and increasingly rare earth elements (REE). They are collectively termed as technology metals. Numerous applications stimulated the use of technology metals, and their supply is at stake, owing to the high demand and uneven geographical distribution of these metals. Their stable supply is crucial for the transition to a sustainable and circular economy. There is an increasing interest in secondary sources of these metals. This article outlines the global state of electronic waste, its management and the latest technological developments in metal recovery from various streams of electronic waste. An emphasis is given to printed circuit boards (PCB), hard disc drives (HDD) and displays regarding their critical metal content. Physical, pyrometallurgical and (bio)hydrometallurgical metal recovery technologies are overviewed. In addition, perspectives on electronic waste as a secondary source of critical metals are given.
... ide-code .org) (Akcil 2010). Additionally, the discharge of cyanide containing wastewaters to drainage systems, which ultimately end-up in wastewater treatment plants (WWTP), has been reported to have deleterious effects on the microorganisms that are normally employed in such systems as they are sensitive to the presence of CN − (Han et al. 2013;Kim et al. 2011). ...
Article
Full-text available
This study focused on the identification of free cyanide (CDO) and thiocyanate (TDO) degrading microbial communities using a culture-dependent and independent approach. Culturable microbial species were isolated from the CDOs (n = 13) and TDOs (n = 18). The CDOs were largely dominated by Bacillus sp. while the TDOs were dominated by Bacillus sp., Klebsiella oxytoca, Providencia sp. and Pseudomonas sp. However, 16S rRNA amplicon gene sequencing revealed the complexity and diversity of the microbial communities in contrast to the organisms that were detected using culture-dependent technique. Overall, the organisms were mainly dominated by Myroides odoratimimus and Proteus sp. at 37.82% and 30.5% for CDOs, and 35.26% and 17.58% for TDOs, respectively. The co-culturing of the CDOs and TDOs resulted in biochemical changes of key metabolic enzymes, and this resulted in the complete degradation of CN- and SCN- simultaneously; a phenomenon which has not been witnessed, especially under alkaline conditions. Current ongoing studies are focused on the application of these organisms for the biodegradation of CN- and SCN- in a continuous system, under changing operational parameters, to assess their effectiveness in the biodegradation of CN- and SCN-.
... The RJC Cert and the ICMM SDF include environmental impacts among a broader range of sustainability standards. Cyanide spills inspired the creation of the ICMC for gold mining in the early 2000s (92,121,122). ...
Article
Full-text available
This review focuses on transnational governance in the minerals and mining sector. Although several initiatives have emerged to address specific governance challenges in this sector, knowledge of these efforts is piecemeal and little is known about patterns in transnational governance development across this issue area. We address these gaps by reviewing the extant research literature and analyzing empirical examples of transnational minerals and mining governance, using the gold sector as an illustrative case. We identify the social, humanitarian, security, and environmental problems manifest along the mineral lifecycle and consider the extent to which existing transnational governance initiatives address these issues. We call for future scholarship that addresses the diversity of transnational governance practices in the minerals and mining sector and explains emergent patterns in the particular forms of governance that dominate this issue area, as well the types of problems that have (and have not) received attention.
... The American states of Colorado and Montana are still deliberating over a ban on using cyanide in gold mines (cited in Laitos, 2012). The ICMC, an important source of principles and standards of practice for use of cyanide, states that 50 mg/l WAD is an appropriate discharged concentration (Akcil, 2010;Gibbons, 2005), which refers to limiting wildlife exposure to cyanide. However, there is no research predicting the relationship between the discharged cyanide concentration into TSFs, the pH of the solution in TSFs, and the potential danger to the environment and public health. ...
... Existing methods of chemical sample preparation are often multistage [16,19,27,31,44], taking between 2-72 hours from start to end [7,9,16,30,39,41] and requiring use of complex mixtures of chemical reagents [6,16,42]. The most widely used chemical sample preparation method is analyte leaching by various reagents: thiosulphate [7,14,22,25,34], cyanide [6,12,28,36], thiourea [18,29,30] and various mixtures of acids and reagents [6,9,16,18,42]. To extract elements, supercritical water pre-treatment combined with leaching techniques [10,32,40] is a common technique. ...
Article
Waste printed circuit boards (PCBs) contain high amounts of valuable precious metals (PMs) as well as ecotoxic elements (TE). Recycling waste PCBs enables the recovery of precious metals minimize harm to the environment caused by discarded electronics. This study established a benign and effective process for selective recovery of Au, Pt, Pd and ecotoxic elements such as As, Cd, Cr, Pb, Sb from waste PCBs. Pre-treating waste PCBs with a mixture of HCl and H2O2 in autoclave was fast and efficient decomposition. In order to recover PMs and TE from obtained PCB solutions, two sorbents were synthesized. 0.1 M HCl is sufficient for extraction of 96–100 % of TE and 3 M HCl is used for extraction of 100 % of PMs from PCB-solutions. The developed approach of transferring analyte into a solution is characterized as highly productive and make it possible to avoid any impact of matrices upon selectivity extraction and to determine analyte with high accuracy. The concentrations of analytes in five PCB samples were found in range of 10−6 - 10-1 % wt by HR-CS GFAAS method. HR-CS-GFAAS limits of determination and upper limits of analyte content determination were (µg·mL-1) 0.0008 and 0.1 (Au); 0.0008 and 0.1 (Pd); 0.001 and 0.8 (Pt); 0.0005 and 0.3 (As); 0.00006 and 0.01 (Cd); 0.0002 and 0.03 (Cr); 0.0005 and 0.1 (Pb); 0.0005 and 0.25 (Sb). The obtained data will be useful for the development of processes for the recycling of analytes from waste mobile phones.
... However, the benefits of cyanide leaching are evident only when the reagent is dealt with cautiously, complying with all the safety guidelines. ( Akcil, 2010 ). ...
Article
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The modernization of technologies has led to the escalation of the demand for silver in the electrical and electronics manufacturing sectors. Conventional lean grade ores of silver are insufficient to account for silver consumption. This deficit compels the extraction engineers to broaden the scope and delve into secondary silver recovery and recycling. The key purpose of current work is to draw attention to the modern hydrometallurgical technologies in silver recovery from waste printed circuit boards (WPCBs). Abundant with the base and precious metals, WPCBs form a plethora of important materials and the efficient recycling of WPCBs is essential for economic and environmental reasons. Low capital cost, high selectivity, no dust generation and reduced environmental effect advocate the versatility of hydrometallurgical route. Silver leaching from WPCBs through cyanide, thiourea and thiosulfate have been investigated. Cementation, ion exchange, solvent extraction, and membrane processes employed for recovery of silver have been studied. This review provides a holistic view of the significant technological advances throughout the world to recover silver from the WPCBs by hydrometallurgical route.
... The cyanide has been efficient and user-friendly so long as handled carefully obeying all the safety regulations. It is reported that >90% of gold and silver in the 875 gold and silver mine recovery processes uses cyanide lixiviant by the year 2000 (Akcil 2010). The optimal gold extraction pH is 10.5 or greater, where most of the free cyanide in the solution in the form of the cyanide anion (CN − ) and cyanide loss by volatilization is limited, or the cyanide will not adapt to industrial produce process, especially production safety (Kuyucak and Akcil 2013). ...
Article
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A large number of waste mobile phones have already been generated and are being generated. Various countries around the world have all been positively exploring the way of recycling and reuse when facing such a large amount of waste mobile phones. In some countries, processing waste mobile phones has been forming a complete industrial chain, which can not only recycle waste mobile phones to reduce their negative influence on the environment but also turn waste into treasure to acquire economic benefits dramatically. However, the situation of recycling waste mobile phones in China is not going well. Waste mobile phones are not formally covered by existing regulations and policies for the waste electric and electronic equipment in China. In order to explore an appropriate system to recover waste mobile phones, the mobile phone production and the amount of waste mobile phones are introduced in this paper, and status of waste mobile phones recycling is described; then, the disposal technology of electronic waste that would be most likely to be used for processing of electronic waste in industrial applications in the near future is reviewed. Finally, rationalization proposals are put forward based on the current recovery status of waste mobile phones for the purpose of promoting the development of recycling waste mobile phones in developing countries with a special emphasis on China.
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Küresel ekonomideki dalgalanmaların en önemli tetikleyicilerinin başında, hammadde tedariğinden dolayı, madencilik sektörü gelmektedir. Bu durum, aynı zamanda, madencilik sektörünü kamuoyu gündeminde tartışmaların arttığı bir konuma oturtmaktadır. Ülkemizde olduğu gibi, küresel anlamda da madencilik sektörü içinde İş Sağlığı ve Güvenliği tedbirlerinin uygulanmasına en hassas olan Altın ve Gümüş madenciliğidir. Bunun ana sebebi; çok ince boyutta serbestleştirilmesi gereken cevher tipinden ve de çok düşük tenörlerin işlenmesinden dolayı bu değerli metallerin kazanımında siyanür kimyasalının kullanılmasından ileri gelmektedir. Bilindiği gibi, altın ve gümüş madenciliğinde siyanür kullanımı zorunluluğu bu konuda 120 yılı aşkın süren araştırma ve bilimsel gerekçelere dayanmaktadır. Siyanürün yerine kullanılabilecek başka kimyasallar üzerine 80’li yıllardan bu yana ciddi araştırmalar yürütülmektedir. Ancak siyanürün etkinliği, ekonomisi yanında, insan sağlığı ve çevre üzerinde bilinen risk ile birlikte kullanılabilirliğinden dolayı madencilik endüstrisinde kullanımı halen devam etmektedir. Dünya’da altın ve gümüş üretiminin % 90’ınında halen bu değerli metallerin kazanımı için etkin bir kimyasal olarak siyanür kullanılmaktadır. Şehir efsanelerinin aksine kanserojen etkisi olmayan bu kimyasalın küresel olarak yönetimi, 2000 yılındaki Baia Mare (Romanya) altın madenindeki kazadan sonra Birleşmiş Milletlerinde aralarında olduğu kuruluşlar tarafından ele alınmıştı ve 2002 yılından itibaren siyanür yönetiminin anayasası olarak bilinen “Uluslararası Siyanür Yönetim Kodu” (International Cyanide Management Code-ICMC) tüm dünyada yaygın olarak uygulanmaya başlandı. Dolayısı ile, siyanür kullanılan altın ve gümüş madenciliğinde 15 yıldır bu tür bir bağımsız dış denetleme aracının küresel düzeyde uygulanmasıyla iş sağlığı, güvenliği ve çevre konularında en üst seviyede yeni ama normal bir yaklaşım sergilenmektedir. Bu konuda dünyadaki en üst düzey denetleme şekli olmasına rağmen, bağımsız dış denetleme süreçlerine girmek istemeyen bazı şirketler ileri düzeyde yönetim uygulama kriterleri nedeniyle çekingen davranarak bu sürece girmemektedirler. Ülkemizde ise konuya uzak yakın birçok şirket için ilk örnek uygulama 2012 yılında başlamıştır (Kışladağ Altın Madeni, Uşak). Ülkemizde madencilik faaliyeti yapan birçok şirketlerinde önemli ölçüde Siyanür Koduna uyumlanma ve bağımsız dış denetleme sürecine katılmak için; eğitim, boşluk analizi ve ana denetleme (ICMI sertifikasyonu) çalışmaları yaklaşık 7 yıldır devam etmektedir.
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There were considered the key approaches to resolving of problems, arising in the time of exploitation of Russian and CIS countries gold-mining enterprises, where alkaline cyanide solutions are used. There were compared the international and Russian requirements to neutralization of cyanide wastes of gold-mining industry. International cyanide classification was carried out. Processes of natural detoxification of cyanide compounds in tailings impoundment were considered. There were described the current Russian regulations, relating to purification of waste waters from cyanide ions and thiocyanates which are free and bounded to complex compound with metal ions. Efficiency of purification of cyanide waste waters and possibility of their discharge into water flows have the following determining indices: values of maximum allowable concentrations, dissolved in water; standard of admissible exposure and standard of admissible discharge. This article shows the Russian approach to assessment of hazard of solid wastes, which appear as a result of semi-dry storage of cyanide leaching cakes in complete sludge process, and gold heap leaching. It was noted that it is rather easy to destroy the most toxic free cyanides by a variety of methods, harmless for humans and fauna. However, even after complete destruction of cyanide compounds, dissolved in water, obtained waste waters should be dissolved by pure water or with additional purification measures. The indicators, which most frequently exceed the standard concentrations in de-cyanided water, include pH value, total salt content, products of decomposition of cyanide ions and cyanide destroying reagents, and some by-products of ore and concentrate leaching process which do not contain CN anions. 1. Ritcey G. M. Tailings management: problems and solutions in the mining industry. Amsterdam, New York: Elsevier, 1989. 970 p.
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The decreasing grade of gold deposits and environmental regulations concerning the use of cyanide, a conventional extraction agent used in gold recovery, has highlighted the challenge in the field of gold extraction. The bioleaching of gold using microorganisms for in situ cyanide production to recover gold is a promising new approach for prohibiting the use of conventional chemical cyanide. For the first time, this study reports a comprehensive investigation on the role of pH on individual steps of Bacillus megaterium bacterial growth, cyanide production, and gold recovery. This novel way of maximizing biogenic cyanide is highly efficient and demonstrates biocyanidation as a potentially viable technique for direct treatment of sulfidic gold ores, i.e., eliminating the step of biooxidation for the first time. The low-grade sources were treated with both chemical cyanide and biogenic cyanide generated by B. megaterium. Results indicate that the bacteria generated a maximum of 61.89 ppm cyanide, which correspondingly recovered over 87% and 43% gold from O1 and O2 sources, respectively, comparable to gold recoveries by chemical leaching. The pure gold powder leaching was also performed to evaluate the loss in gold recovery due to the biosorption of gold to bacterial cells. The feasibility of the work is also supported by green chemistry metrics, and a comparison has been made between conventional and biocyanide leaching. The results revealed the potential of biocyanidation for industrial applications.
Thesis
Sustainability in mining has received much global attention in recent years from academics, policy makers, and industry leaders, and other players. However, scant attention has been paid to examining the sustainability practices of mining companies within developing countries in addressing the proximate and long-term social and environmental impacts of mining activities. To address this knowledge gap, this study examines how large-scale mining companies address their social and environmental impacts through their sustainability practices. This study is situated within an interpretivist paradigm and employs a qualitative research methodology based on multiple cases, drawing on data from interviews with six (6) managers of multinational mining companies operating in Ghana, and 12 key stakeholder groups. This thesis contains four empirical findings chapters. The first of these examines the sustainability practices of large-scale mining companies in addressing environmental impacts throughout mine lifecycle. The findings indicate that the environmental sustainability practices are determined by regulatory compliance and corporate environmental responsibility. Although the environmental sustainability practices are predicated on the requirements in relevant policies and legislation, the findings demonstrate that regulatory pressures drive large-scale mining companies to embrace beyond compliance initiatives based on perceived ethical obligations. The second findings chapter examines the barriers to environmental sustainability implementation in large-scale mining in Ghana. The findings demonstrate that both institutional and corporate challenges are hindering effective sustainability implementation. The third findings chapter investigates the sustainability practices of large-scale mining companies in addressing social impacts throughout mining development. The findings show that large-scale mining companies have embraced a broader scope of social sustainability implementation based on a changing institutional environment. Drawing on stakeholder theory, the findings indicate that mine managers address social sustainability challenges based on instrumental and normative considerations. The fourth and final findings chapter examines the drivers for and barriers to mining companies’ social sustainability practices by drawing on stakeholder theory and institutional theory. The findings suggest that regulatory evolution, institutional pressures, post-closure legacies, transparency and disclosures, and managerial cognition are key drivers for the social sustainability implementation of large-scale mining companies. On the contrary, the barriers to social sustainability implementation stem from institutional voids and divergent stakeholder interests. Thus, by doing a critical reflection of the findings, this study contributes to theory by offering a series of propositions and suggesting a holistic framework for social and environmental sustainability implementation. Regarding stakeholder theory, the findings show that Large-scale mining companies experience fewer pressures from local communities and activists because of their lack of proactive engagement on environmental sustainability issues. Drawing on institutional theory, the findings suggest that multiple and contradictory logics within various institutional arrangements undermine social and environmental sustainability implementation. Additionally, this study provides a frame of reference for practitioners including mining companies and mine managers, regulatory officials, policy makers, and mining pressures groups who are involved in social and environmental sustainability implementation. Future research may consider data sets from other empirical domains, which might uncover differences in the emerging framework for sustainability implementation
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Chemical replacements for cyanide have been investigated for decades; however cyanide remains the exclusive lixiviant of choice in the mining industry due to a combination of its availability, effectiveness, economics and ability to use it with acceptable risk to humans and the environment. About 90% of the significant gold producing operations worldwide currently utilize cyanide for gold and silver extraction. Despite the number of cyanide-related mining operations, there have been no documented accounts during the previous three decades of the death of humans due to cyanide as a direct consequence of major mining-related environmental incidents. Major mining-related environmental incidents have not been concentrated in any geographic location, may occur regardless of the size of the company and do not occur more frequently with a specific type of mining activity. The main aspects of cyanide management that should be addressed at mining operations include transportation of cyanide to site, process solution conveyance, worker health and safety training, water management and treatment, emergency response and preparedness, workplace and environmental monitoring, and community relations. If these aspects of cyanide management are integrated into an overall cyanide management plan, dramatic reductions in risk and potential incidents at mine sites will be realized.
Chapter
There are several water and tailings treatment processes that have been successfully used worldwide for cyanide removal at mining operations. The key to successful implementation of these processes involves consideration of the following:•Site water and cyanide balances under both average and extreme climate conditions.•Goals to be adopted for cyanide levels in treated effluent, including the form of cyanide to be regulated (free vs. WAD vs. total cyanide).•The range of cyanide treatment processes available and their ability to be used individually or in combination to achieve treatment objectives.•Proper treatability testing, design, construction, maintenance and monitoring of both water- and cyanide-management facilities.By carefully considering these aspects of water and cyanide management before, during and after mine operation, operators can reduce the potential for environmental impacts associated with the use of cyanide. Another aspect of cyanide treatment to be considered is the potential environmental impact of the cyanide-related compounds - cyanate, thiocyanate, ammonia, nitrate and nitrite. These compounds may be present in mining solutions to varying extents and may require treatment if water is to be discharged. Each of these cyanide-related compounds is affected differently in the treatment processes discussed, and this should be considered when evaluating cyanide-treatment alternatives for a given site. Table 13 provides a simplified summary of the general applications of various treatment technologies for the removal of iron cyanide and WAD cyanide. This table represents a very simplified summary, but can be used as a conceptual screening tool when evaluating cyanide-treatment processes.
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In the history of Turkey the first use of cyanide for gold recovery has been at the Ovacik Gold Mine. During one-year test period, this mine has successfully been mining and processing after a complicated and extensive environmental impact procedure. In Turkey about 2500 ton of sodium cyanide are used with about 240 ton of sodium cyanide being used at this mine annually. During the test period, it has been shown that an effluent quality (CNWAD) between 0.06 ppm (min) and 1 ppm (max) was achievable after cyanide destruction with the Inco Process. It was also found that treated effluent values (CNWAD) of process water (decant) were between 0.04 ppm (min) and 0.59 ppm (max). This paper presents a review of the cyanidation and cyanide destruction processes at the Ovacik Gold Mine.
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This paper discusses issues of cyanide management at the newly-constructed Ovacik gold–silver mine in Turkey. The mine, which has been using 120 ton/y of sodium cyanide (NaCN) since May 2001, was the first operation in the country to use cyanide to recover gold. Mine staff strives to continuously plan and provide detailed accounts of the management practices and initiatives being undertaken with regard to handling cyanide. It is believed that the programs and activities that have been implemented at Ovacik will facilitate improvement in this area.
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In gold mining, cyanide has been the preferred lixiviant worldwide since 1887. Although cyanide can be destroyed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. Biological treatment of cyanide is a well-established process and has been commercially used at gold mining operations in North America. Biological treatment processes facilitate growth of microorganisms that are essential for the treatment. The present review describes the advances in the use of biological treatment for the destruction of cyanide in gold mill effluents.
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