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A Preliminary Research on Acid Pressure Leaching of Pyritic Copper Ore in Kure Copper Mine, Turkey
Abstract
The combination of roasting and pressure leaching is an alternative process that offers advantages over conventional processes because of the shorter leaching time and higher metal recovery. The copper and iron sulphide minerals examined in this study were chalcopyrite (CuFeS2) and pyrite (FeS2). The best results obtained were with a pre-treatment by roasting followed by acid pressure leaching in an autoclave system. The extraction of copper achieved was over 85%. Copper dissolution in this system is affected by particle size, leaching time and oxygen pressure. This paper presents the preliminary research on acid leaching of pyritic copper ore in an autoclave system under laboratory conditions.
... Copper, one of the most important metals for humanity for more than five thousand years [1,2], is still among the most common metal used in the industry [3][4][5]. In nature, copper is generally found in the form of sulfide and oxide minerals such as azurite, malachite, tenorite, chrysocolla, bornite, brochantite, enargite, chalcopyrite, chalcocite, and covellite [3][4][5][6][7][8]. The most utilized mineral for the copper production [1,2], chalcopyrite (CuFeS 2 ), is an important and plentiful source that accounts for about 70% of all copper in the world, and is one of the widest spread copper-bearing minerals [9][10][11][12][13][14]. ...
... It was sieved to -212 µm before dried at 105 °C for 12 h. The mineralogical analysis results of the chalcopyrite concentrate samples are given in Table 1, and the mineralogical analysis results of the roasted concentrate, which has been subjected to oxidizing roasting process at 600 °C for 1 h according to the data in the literature [6,19,20,42,63,65,67,[79][80][81][82][83], are given in Table 2. ...
... In this study, the Cu extraction (%) values, which are a measure of how much of the total copper is leached, were calculated using Eq. (6) given below: (6) Cu Extraction (%) = Amount of Dissolved Cu Amount of Cu in Feed * 100. ...
Chalcopyrite (CuFeS2) is commonly used ore in production of copper, but leaching of this ore is very slow and inefficient due to “passivation” during leaching at atmospheric conditions. In this study, in order to overcome drawbacks of the passivation layers, the concentrate supplied from Eti Bakır A.Ş. Küre Plant in Turkey was roasted at 600 °C for 1 h and after leached. Box–Wilson procedure of statistical experimental design was utilized to identify the effects of significant leaching variables for instance leaching time (X1; 10–120 min), solid/liquid ratio (X2; 0.01–0.20), and H2SO4 concentration (X3; 0.01–1.00 M) on Cu extraction (%) from roasted concentrate and was tried to be optimized. The coefficients of response functions have been calculated by regression analysis, and the estimates have been found to be well in line with the experimental outcomes. The optimal leaching parameters, time, solid/liquid rate and H2SO4 concentration were determined as 115 min, 0.116, and 0.71 M, respectively, and the highest Cu extraction (%) value was calculated as 92.45%.
... Leaching studies have focused on the use of common laboratory chemicals such as sulfuric acid [2][3][4][5][6], nitric acid [7], halogens [8], and ammonia [9,10]. Nevertheless, direct leaching of chalcopyrite concentrates has some problems due to the low solubility of chalcopyrite without the presence of an oxidant, the formation of precipitation, and the disposal of the large amount of iron that dissolves along with the copper [11][12][13]. ...
... However, the anodic reaction for metal sulfur compounds and the total reaction are represented in Eqs. (2) and (3): ...
Inthisstudy,theleachingconditionsofchalcopyriteconcentratewithammoniumpersulfateinapressurereactorsystemwereoptimizedusingacentralcompositedesign(CCD).Duringdecompositionofammoniumpersulfate,theactiveoxygenformedcanprovideahighoxidationpotential,acidicmedium,andhighpres-sureinaclosedvesselforthedirectleachingofchalcopyrite,whichisamajoradvantageofthisprocessoverotherleachingprocesses.Theoptimizationcriteriaweredefinedtomaximizecopperextractionwhileminimizingironextraction.Theoptimalleachingconditionsweredeterminedtobeanammoniumpersulfateconcentrationof210g/L,aleachingtemperatureof388K,andareactorfullnessratioof0.43;experimentswereperformedtogetherwithconstantparametersincludingaleachingtimeof180min,stirringspeedof500rpm,andliquid/solutionratioof11g/L.Undertheoptimalconditions,therecoveryofCuandFewas57.04%and14.71%,respectively.Theproposedquadraticmodelisingoodagreementwiththeexperimentaldata,exhibitinghighcorrelationcoefficients(R2)fortheresponsesofbothmetals.
... Leaching studies have focused on the use of common laboratory chemicals such as sulfuric acid [2][3][4][5][6], nitric acid [7], halogens [8], and ammonia [9,10]. Nevertheless, direct leaching of chalcopyrite concentrates has some problems due to the low solubility of chalcopyrite without the presence of an oxidant, the formation of precipitation, and the disposal of the large amount of iron that dissolves along with the copper [11][12][13]. ...
... However, the anodic reaction for metal sulfur compounds and the total reaction are represented in Eqs. (2) and (3): ...
In this study, the leaching conditions of chalcopyrite concentrate with ammonium persulfate in a pressure reactor system were optimized using a central composite design (CCD). During decomposition of ammonium persulfate, the active oxygen formed can provide a high oxidation potential, acidic medium, and high pressure in a closed vessel for the direct leaching of chalcopyrite, which is a major advantage of this process over other leaching processes. The optimization criteria were defined to maximize copper extraction while minimizing iron extraction. The optimal leaching conditions were determined to be an ammonium persulfate concentration of 210 g/L, a leaching temperature of 388 K, and a reactor fullness ratio of 0.43; experiments were performed together with constant parameters including a leaching time of 180 min, stirring speed of 500 rpm, and liquid/solution ratio of 11 g/L. Under the optimal conditions, the recovery of Cu and Fe was 57.04% and 14.71%, respectively. The proposed quadratic model is in good agreement with the experimental data, exhibiting high correlation coefficients (R 2) for the responses of both metals.
... Leaching is extraction of the component from solids by using a solvent [1][2][3]. It finds application in recovery of various valuable metals [4][5][6]. The metal recovery from wastewater can be carried out by various physical, chemical and biological processes [7][8][9][10][11][12]. ...
Flotation is combination of chemical, physicochemical and physical phenomena. It separates minerals on the basis of differences in surface properties. It is important to study the chemical and physicochemical properties of mineral surfaces. The process involves injection of air bubbles into a moving stream of aqueous slurry containing a mixture of particles. In the process only hydrophobic ores are collected on the bubble surface and exit the stream. According to the investigations reported by various researchers, it is envisaged to have adequate characterization of the system under consideration. Important factors in characterization includes solid phase, aqueous phase with solutes, gas or the second liquid phase, the three kinds of interface and interline, flow and force parameters and end products. The dispersed-air flotation looked preferable than dissolved air flotation. Gas hold up, superficial velocity and bubble size are important factors in column flotation.
... The preliminary research on acid pressure leaching of pyritic copper ore was carried out by Akcil. [11] According to him, the combination of roasting and pressure leaching was an alternative process for copper extraction. He examined copper and iron sulphide minerals in chalcopyrite (CuFeS 2 ) and pyrite (FeS 2 ).He obtained best result by pre-treatment by roasting followed by acid pressure leaching in an autoclave system. ...
Leaching is one of the major unit operations used in mining sector. Leaching is extraction of the component from solids by using a solvent. The solvent preferably removes certain component. Leaching finds application in recovery of various valuable metals. Microbial leaching is gaining importance for recovery of metals from waste. It also plays important role in agriculture. It is always desirable to avoid the leaching of valuable components of soil through run offs. Various investigators have carried out research on various aspects of leaching. This review paper summarizes studies and research on various aspects of leaching.
... Leaching is extraction of the component from solids by using a solvent [1][2][3]. It finds application in recovery of various valuable metals [4][5][6]. The metal recovery from wastewater can be carried out by various physical, chemical and biological processes [7][8][9][10][11][12]. ...
Flotation is combination of chemical, physicochemical and physical phenomena. It separates minerals on the basis of differences in surface properties. It is important to study the chemical and physicochemical properties of mineral surfaces. The process involves injection of air bubbles into a moving stream of aqueous slurry containing a mixture of particles. In the process only hydrophobic ores are collected on the bubble surface and exit the stream. According to the investigations reported by various researchers, it is envisaged to have adequate characterization of the system under consideration. Important factors in characterization includes solid phase, aqueous phase with solutes, gas or the second liquid phase, the three kinds of interface and interline, flow and force parameters and end products. The dispersed-air flotation looked preferable than dissolved air flotation. Gas hold up, superficial velocity and bubble size are important factors in column flotation.
... During the pressure leaching process, copper and cobalt sulfides react to form sulfates, while iron can be precipitated into the residue in different forms such as hematite, goethite, and jarosite depending on the reaction temperature and acidity (Akcil 2002;Anderson 2003;Zhang et al. 2012;Seyrankaya 2022). The released acid during iron precipitation reacts with the gangue, and the rest remains in the solution as free acid. ...
Copper–cobalt sulfide flotation concentrate received from Comika Mining Kamoya project in Congo contains around 24.2% copper, 7.1% cobalt, 22.9% sulfur, 13% iron, and a small amount of other metals. Under the condition of temperature 190 °C, oxygen partial pressure 6 atm, leaching time 2 h, liquid-to-solid ratio 5:1, and initial acidity 0 g/L, metal recovery rates of over 98% can be achieved for both copper and cobalt. Copper that exists in chalcocite, bornite, chalcopyrite, and carrollite was almost completely leached, while most of copper in limonite remains in the residue. Cobalt that exists in carrollite can be completely leached, while the unleached cobalt remains in the pyrite and limonite phases. During pressure leaching, sulfur was oxidized into sulfate. Meanwhile, iron undergoes a dissolution reaction and generates high-valent iron ions, which can be partially oxidized into metal sulfides and partially precipitated under low acidity conditions. The hematite encapsulation is the main reason for the incomplete leaching of copper and cobalt.
... Leaching is the method of winning metals from a solid mineral by dissolving them in a liquid solvent naturally or by an industrial process (Akcil, 2002). The solvent preferentially extract certain components. ...
With much amount of money the nation had invested into the extractive sector of the economy, minerals are still mined and exported out of the country for beneficiation which results into much economic losses in the mining and extractive industries. The need to reduce the huge amount of losses expended on extracting valuable metals from ores by local miners and out springing cottage industries motivates this work. This report covers the design and construction of a laboratory size leaching equipment suitable for dissolution of clean pulverised minerals in acid and alkaline media via agitation and in-situ leaching techniques in single operation system. The dissolved metals are easily recovered from the solution by other techniques. The design and fabrication is based on the fundamentals of stoichiometric calculations and chemical reactions, engineering design drawings using AUTOCAD and INVENTOR softwares, material selection and safe environmental ethics. The equipment is produced from combination of highly corrosion resistant plastic materials, mild steel, stainless steel and other components. For the purposes laboratory studies, the machine can process about 320-350 kg mineral feeds charged manually and in batches for working period of 1 to 8 hours per day. The estimated fabrication cost is about N194,500.00.
... takes place faster, accompanied with growth of "molecular oxygen" which is adsorbed in surface of particles. This avoids " particle/peroxide" contacting, [12]. ...
____________________________________________________________________________________________ The leaching of copper from Mawat sulfide ore in Sulaimaniya, North East of Iraq with sulfuric acid in the presence of hydrogen peroxide is studied. The aim of this study is for investigating the effectiveness of hydrogen peroxide as an oxidant for sulfuric acid leaching of copper from a complex sulfide ore. Distribution of elements with different particles size was initially determined using XRF to provide as basis to explain leaching process. In this study the following parameters are selected: leaching time, concentration of hydrogen peroxide, particle size, stirring speed and acid concentration at a constant temperature of 25 ºC are studied. The concentrations of copper reduced as particle size decreased while silica, sulfur and iron contents increased. The higher recovery of copper, 97.7% was obtained at optimum leaching conditions which are time 180 minutes, stirring speed 160 rpm, particle size of 75 μm and concentrations of 3M H 2 SO 4 , 2M H 2 O 2. It was observed that copper leaching rate increases with the increase of hydrogen peroxide concentrations. The increase in stirring speed has a negative leaching effect as it promotes hydrogen peroxide decomposition.
... The differences between mine types might originate from the different ore types, smelting operations or treatment processes. Magnetic separation is usually the first option for iron beneficiation [57,58], whereas acid leaching is used for extracting copper ore [59], during which heavy metals can be inadvertently released into the environment. Accordingly, soil heavy metal availabilities at copper mine sites were usually higher than at iron mines ( Figure 2A). ...
China exemplifies the serious and widespread soil heavy metal pollution generated by mining activities. A total of 420 soil samples from 58 metal mines was collected across Eastern China. Total and available heavy metal concentrations, soil physico-chemical properties and geological indices were determined and collected. Risk assessments were applied, and a successive multivariate statistical analysis was carried out to provide insights into the heavy metal contamination characteristics and environmental drivers of heavy metal availability. The results suggested that although the degrees of pollution varied between different mine types, in general they had similar contamination characteristics in different regions. The major pollutants for total concentrations were found to be Cd and As in south and northeast China. The availability of Zn and Cd is relatively higher in south China. Soil physico-chemical properties had major effect on metal availability where soil pH was the most important factor. On a continental scale, soil pH and EC were influenced by the local climate patterns which could further impact on heavy metal availability. Enlightened by this study, future remediation strategies should be focused on steadily increasing soil pH, and building adaptable and sustainable ecological system to maintain low metal availabilities in mine site soils.
... takes place faster, accompanied with growth of "molecular oxygen" which is adsorbed in surface of particles. This avoids " particle/peroxide" contacting, [12]. ...
____________________________________________________________________________________________ The leaching of copper from Mawat sulfide ore in Sulaimaniya, North East of Iraq with sulfuric acid in the presence of hydrogen peroxide is studied. The aim of this study is for investigating the effectiveness of hydrogen peroxide as an oxidant for sulfuric acid leaching of copper from a complex sulfide ore. Distribution of elements with different particles size was initially determined using XRF to provide as basis to explain leaching process. In this study the following parameters are selected: leaching time, concentration of hydrogen peroxide, particle size, stirring speed and acid concentration at a constant temperature of 25 ºC are studied. The concentrations of copper reduced as particle size decreased while silica, sulfur and iron contents increased. The higher recovery of copper, 97.7% was obtained at optimum leaching conditions which are time 180 minutes, stirring speed 160 rpm, particle size of 75 μm and concentrations of 3M H 2 SO 4 , 2M H 2 O 2. It was observed that copper leaching rate increases with the increase of hydrogen peroxide concentrations. The increase in stirring speed has a negative leaching effect as it promotes hydrogen peroxide decomposition.
... In nature, the ores with copper content are available such as malachite, azurite, tenorite, covellite, chalcopyrite and bornite [1]. Metallic copper production from these ores generally can be performed by pyrometallurgical and hydrometallurgical methods at the present time [2]. ...
... To overcome these problems, researchers have focused on some combined methods. One of the methods is mechanical activation/extended milling as known pre-treatment of the concentrate before leaching process [17][18][19][20][21]. Another way is pressure leaching of concentrate or/and ore under the condition of high oxygen potential and acidic solution [22][23][24][25][26]. Although all of these methods are supplying high metal extraction, they are known to having high cost processes. ...
The addition of NaCl in the ammonium persulfate-APS (as an oxidant) leaching was investigated. APS has some advantages compared with conventional oxidants and its standard redox potential (E°) is 2.0 V. Effect of six parameters such as NaCl concentration, APS concentration, temperature, time, liquid–solid ration (L/S), and stirring speed on the leaching behavior was studied. Results showed that metals extraction increased with increasing of NaCl concentration, APS concentration, leaching temperature (up to 333 K), and L/S ratio. During oxidative leaching of sulfide minerals, the occurrence of elemental sulfur layer on particle surface is known as primary problem that causes low metal extraction. According to the results, the passivation effect of sulfur layer and low dissolution problems can be eliminated in the presence of chloride ions. Copper and iron extraction yields were obtained as 75% and 80%, respectively under leaching conditions as follows: APS concentration 250 g/L; NaCl concentration 150 g/L; time 180 min; temperature 333 K; stirring speed 400 r/min; and L/S 250 mL/g.
... Sulphuric acid, produced at an amount over 19 million tonnes in 1997 in Western Europe, is estimated to have a total worldwide production of approximately 150 million tonnes (Best Available Techniques, 1999). The main minerals of the Eti Mine Company Kure Copper Plant are pyrite and chalcopyrite (Akcil, 2002;Akcil and Deveci, 2010). The high-iron-content, copper-recovered pyrite concentrate obtained following flotation is sent to the Eti Mine Company Sulphuric Acid Production Plant for sulphuric acid production. ...
The pyrite ashes formed as waste material during the calcination of concentrated pyrite ore used for producing sulphuric acid not only has a high iron content but also contains economically valuable metals. These wastes, which are currently landfilled or dumped into the sea, cause serious land and environmental pollution problems owing to the release of acids and toxic substances. In this study, physical (sulphation roasting) and hydrometallurgical methods were evaluated for their efficacy to recover non-iron metals with a high content in the pyrite ashes and to prevent pollution thereby. The preliminary enrichment tests performed via sulphation roasting were conducted at different roasting temperatures and with different acid amounts. The leaching tests investigated the impact of the variables, including different solvents, acid concentrations and leach temperatures on the copper and cobalt leaching efficiency. The experimental studies indicated that the pre-enrichment via sulphation roasting method has an effect on the leaching efficiencies of copper and cobalt, and that approximate recoveries of 80% copper and 70% cobalt were achieved in the H2O2-added H2SO4 leaching tests.
... 第 20 卷第 12 期 徐志峰，等：复杂硫化铜矿热活化−加压浸出工艺 2413 酸"膨胀"， 需进一步中和处理。 HNO 3 催化氧化浸出 [7−8] 虽能明显降低浸出温度和压力，但在 HNO 3 强氧化作 用下，精矿中绝大部分硫也将氧化生成硫酸，而且浸 出液脱硝也是一难题；加氯活化浸出工艺 [9−10] 虽能有 效克服硫化铜矿浸出"钝化"，但氯离子对浸出设备的 腐蚀不容忽视。 为提高复杂硫化铜矿浸出效率，焙烧预处理是常 用方法，目前已开展多项研究 [11] 。张振健 [12] 针对汤丹 铜精矿提出先在 823~873 K 温度下焙烧脱硫，使不易 浸出的硫化铜转变成易溶解的氧化物或硫酸铜，进而 密闭氨浸；AKCIL [13] 采用 913 K 温度下焙烧方法对黄 铜矿进行预处理，然后进行低温压浸。上述"焙烧−加 压浸出"联合工艺必须回收焙烧过程中释放的 SO 2 以 解决烟气污染问题。近年有学者研究提出硫化铜矿焙 烧预处理新工艺，如固硫焙烧工艺 [14−15] 和硫化相变焙 烧工艺 [16−17] ...
The heat activation-pressure leaching of complex copper sulfide ores with tetrahedrite as the main mineral was studied. The results show that the leaching rates of copper and zinc are as high as 94.08% and 96.95%, respectively, while that of iron is limited at 22.37% in the following conditions: the heat activation temperature 573 K, the heat activation time 1-2 h, the leaching temperature 453 K, the oxygen partial pressure 0.6 MPa, the initial sulfuric acid concentration 1.23 mol/L, the liquid to solid ratio 5:1, the calcium lignosulphonate dosage of 1.25% of the mass of the ores, the leaching time 2 h. No loss of lead, zinc, sulfur and arsenic in the ores occurs during the heat activation pretreatment. The heat activation mechanism of complex copper sulfide ores is further discussed.
... In nature, copper minerals exist mainly in the form of copper sulphide, copper oxide, copper sulphate, and copper carbonate. The main copper sulphide minerals include CuFeS 2 ,CuAkcil, 2002;Bingöl & Canbazo˘ glu, 2004;Liu et al., 2012). Hydrometallurgy has the capacity to deal with oxidised copper ores that are resistant to flotation. ...
The dissolution of malachite particles in ammonium carbamate (AC) solutions was investigated in a batch reactor, using the parameters of temperature, AC concentration, particle size, and stirring speed. The shrinking core model was evaluated for the dissolution rate increased by decreasing particle size and increasing the temperature and AC concentration. No important effect was observed for variations in stirring speed. Dissolution curves were evaluated in order to test shrinking core models for fluid-solid systems. The dissolution rate was determined as being controlled by surface chemical reaction. The activation energy of the leaching process was determined as 46.04 kJ mol
... The optimization of ore-leaching conditions is important in industrial hydrometallurgical processes, and several studies have investigated this topic using various techniques. Akcil (2002) subjected chalcopyrite and pyrite to roasting followed by acidic dissolution, and they concluded that because of the shortening of the leaching time required with the combined roasting and leaching operations, this dual application was preferable to the individual application of each operation. Gü lfen and Aydın (2010) investigated the roasting and sulfation processes of primary chalcopyrite with and without Fe 2 O 3 , as well as the optimum conditions for the dissolution of copper from chalcopyrite in sulfuric acid solutions. ...
The optimum conditions for the extraction of copper from chalcopyrite concentrate into SO2-saturated water were evaluated using the Taguchi optimization method. High level copper recovery was obtained in an environmentally friendly process that avoids sulfur dioxide emission into the atmosphere because SO2 forming in the roasting is used in the dissolution. Experimental parameters and their ranges were chosen as follows: reaction temperature, 293–333 K; solid-to-liquid ratio, 0.025–0.15 g/mL; roasting time, 30–90 min; roasting temperature, 773–973 K; stirring speed, 400–800 rpm; and reaction time, 10–60 min. The particle size and gas flow rate were 63 µm and 10 cm3/min, respectively. The optimum conditions of the dissolution process were determined to be reaction temperature of 318 K, a solid-to-liquid ratio of 0.025 g mL−1, a roasting time of 75 min, a roasting temperature of 773 K, a stirring speed of 400 rpm, and a reaction time of 30 min. Under optimum conditions, dissolution yield of copper was 91%.
... However, low valence state oxidized copper minerals and some secondary sulfide copper minerals, such as cuprite (Cu 2 O), chalcocite (Cu 2 S) and covellite (CuS), as in the material for the present investigation, can only be dissolved in sulfuric acid solution in the presence of an oxidant (Vracar et al., 2003). Numerous leaching methods, such as bioleaching (Watling, 2006;Yin et al., 2008), pressure acid leaching (Akcil, 2002), microwave acid leaching (Kuo et al., 2005), chloride leaching (Tchoumou and Roynette, 2007) and ferric leaching (Cordoba et al., 2008) have been theoretically and experimentally investigated to leach copper from low-grade copper ores or its primary product. However, the application of these methods is extremely limited, due to the immaturity of the relevant technology or the disadvantages in cost. ...
The study aims to leach copper from a low-grade flotation middling by optimizing the leaching process using response surface methodology. The effect of key parameters, i.e., sulfuric acid concentration, nitric acid concen-tration and leaching time, on the leaching efficiency was investigated and a quadratic model was suggested by the methodology to correlate the variables to the efficiency. The results indicate that the model is in good agreement with the experimental data at a correlation coefficient (R 2) of 0.97 and the most influential parameter on efficiency was identified as sulfuric acid concentration. The optimum conditions for copper leaching from the middling were identified as sulfuric acid concentration at 103.74 g/L, nitric acid concentration at 12.50 g/L and leaching time of 30.98 min; under such a condition, an average leaching efficiency of 93.16% was achieved from the middling.
... In the earlier works, several studies were conducted for recovering Cu, cobalt (Co), nickel (Ni), zinc (Zn), gold (Au), and silver (Ag) from pyrite concentrates by sulfatizing-roasting, acid-leaching, and cyanidation, and from Kure massive rich ore, which was used in this study, by direct ferric sulfate, ferric chloride, cupric chloride, and pressure leaching processes (Arslan et al. 1995;Bulut et al. 2001aBulut et al. , 2001bKangal et al. 2001;Akcil 2002;Perek and Arslan 2002;Arslan et al. 2003). The effects of acid concentration, temperature, leaching time, oxygen partial pressure, solid concentration, and the addition of Ag ions as a catalyst on the dissolution efficiencies of Cu, Co, and Zn were investigated in the pressure leaching tests. ...
The effect of mechanical activation on metal dissolutions by pressure leaching of massive rich copper ore taken from Küre copper ore deposit (Turkey) was investigated. The dissolution efficiencies of sulfide minerals are significantly improved by ultrafine grinding, also known as mechanical activation. This grinding results in decrease of particle size and an increase in crystal distortion of sulfide minerals. Leaching efficiencies of copper, cobalt, and Zinc increased from 45.2%, 25.9%, and 87.7% to 98%, 85%, and 97%, respectively, after 3-h mechanical activation. At the end of the activation, leaching was carried out at a temperature of 110°C, 10-bar oxygen partial pressure, and 150-g/L solid concentration without addition of acid. This study has also indicated that mechanical activation involving fine milling as a pretreatment is not only effective on copper minerals dissolution but also on the dissolution of other associated minerals, such as cobalt and zinc sulfides.
... Existing treatment of Cu -Pb -Zn concentrates and their slags include ferric chloride leaching (Deng et al., 2001;Dutrizac, 1992), acidic ferric sulphate leaching (Das et al., 1999), ammoniacal leaching (Anand et al., 1985;Arbiter and McNulty, 1999;Rao and Ray, 1999). Atmospheric and high-pressure leaching were also investigated by some researchers (Akcil, 2000(Akcil, , 2002Akdag et al., 1994;Altundogan and Tumen, 1997;Berezowsky et al., 1991;Das et al., 1999;Evans et al., 1964;Filippou et al., 1997;Forward and Veltman, 1959;Guresin et al., 1996;Habashi, 1999;Karavasteva, 2001;Kawulka et al., 1978;Prasad and Pandey, 1999;Ricketts, 1989;Xia and Pickles, 1999). ...
A laboratory-scale method for treating a bulk concentrate (CuFeS2–PbS–ZnS) for metals recovery was developed utilising a combination of thermal process (roasting) and pressure leaching as an alternative to conventional pyrometallurgical processing. Pyrometallurgy is becoming less acceptable from environmental standpoints for the treatment of bulk concentrates. Additionally, high capital costs make modern facilities cost prohibitive. The leaching agents employed, namely, sulphuric acid (lixivant) and ferric sulphate, are selective for metal sulphides, this coupled with the fact that they create fewer environmental problems and are economical makes this new process highly favourable. In the laboratory evaluation of this process, the metal values in the flotation concentrates were selectively recovered by combining roasting and pressure leaching. The experimental parameters studied included roasting temperature, and pressure leaching pulp density, temperature, and retention time. Laboratory results indicate that roasting followed by pressure leaching is an efficient and cost effective method of treating base metal sulphide concentrates.
Soil heavy metal (HM) contamination around metal mining areas (MMAs) is a global concern that requires a cost-effective ecological risk assessment (ERA) method for preventive management. Traditional ERAs, comparing environmental HM concentrations with benchmarks, are labor- and cost-intensive in field investigations and chemical analyses, which challenge the management demands of numerous MMAs. In this study, a prospective ecological risk assessment method based on exposure and ecological scenario (ERA-EES) was developed to predict the eco-risk levels (low/medium/high) around MMAs prior to field sampling. Five exposure scenario indicators related to soil HM exposure and three ecological scenario indicators reflecting the soil bioreceptor response were selected and combined with the analytic hierarchy process and fuzzy comprehensive evaluation methods for ERA-EES development. Case application and performance evaluation with 67 MMAs in China demonstrated that the ERA-EES method had an overall effective and conservative performance when referring to potential ecological risk index (PERI) levels, with an accuracy of 0.87, kappa coefficient of 0.7, and low or medium eco-risk levels in PERI classified to high levels in ERA-EES. Overall, the selected scenario indicators could efficiently reflect the risk levels of soil HM pollution from mining activities. Besides, more regulatory efforts should be paid to the MMAs of nonferrous metals, underground and long-term mining and those located in southern China. This work provided a convenient and cost-effective prospective ERA method under the trend of ERA being tiered and refined, facilitating the risk management of various MMAs.
An integrated novel approach employing the Taguchi method and Aspen Plus software has been applied to evaluate a new configuration for the industrial process of Zn+Pb+Cu recovery from sphalerite ore, in order to minimize the toxic gas emission. The optimum operating condition achieved by the Taguchi method has been used as initial data for the process simulation. The impact of operating parameters on the process performance is considered. The optimum condition for the conversion of sulfide toxic gases to H2SO4 have been found to be: acid concentration of 0.867 mol/L, reaction temperature of 120 °C, stirring speed of 400 rpm, leaching time of 120 min, sulfide ore particle size of 0.01 mm; solid-to-liquid ratio of 30 wt%, additives amount of 50 kg/ton and oxygen pressure of 200 psi. Under optimum condition, H2SO4 production from sulfide toxic gases is 99%, the removal percentage of Fe, Co, Mn, Ni and Cd impurities is 99% and the recovery percentage of Zn+Pd+Cu is more than 97%.
The sensing mechanism of a salicylideneaniline-based fluorescence chemosensor (SB1) for the cyanide anion (CN⁻) has been investigated by nonadiabatic dynamics and transition state (TS) theory. The intramolecular hydrogen bonds in SB1 and the product SB1-CN are strengthened after photoexcitation, which induce the intramolecular proton transfer in 114 fs and 167 fs by the results of nonadiabatic dynamics. The fluorescence (626 nm) of SB1 emits from the proton-transfer tautomer rather than the excited state intramolecular charge transfer (ICT) state. The new appeared emission peak (523 nm) after the addition of CN⁻ is attributed to the proton-transfer tautomer of SB1-CN, which has a large blue shift (103 nm) compared to that of SB1. The TS calculations demonstrate the occurrence of reaction from SB1to SB1-CN after overcoming an energy barrier of 10.52 kcal/mol and there is a large interaction energy (95.92 kJ/mol) between SB1 and CN⁻, both of which confirm that SB1 has high sensitivity and selectivity to CN⁻. The nucleophilic addition reaction of CN⁻ interrupts the π-conjugation structure of SB1, resulting in an inefficient ICT, which in turn destroys the excited state intramolecular charge/proton transfer (ESICT-ESIPT) coupled system and causes the blue shift of the spectral peak. The work gives a complete explanation about ESICT-ESIPT coupling switching behavior and the sensing mechanism of SB1 for CN⁻.
The sensing mechanism of the ratiometric fluorescence chemosensor 2-((6-(diethylamino)quinolin-2-yl)methylene)malononitrile (3A) for the cyanide anion (CN ⁻ ) has been investigated theoretically. The calculated results show that the small reaction barrier (8.58 kcal/mol) of 3A implies a rapid response speed to CN ⁻ , and that the large interaction energy (25.75 kcal/mol) between 3A and CN ⁻ indicates a high selectivity to CN ⁻ . The results of condensed dual descriptor calculation confirm that CN ⁻ attacks the C 2 site of 3A rather than other sites. The nucleophilic addition reaction of CN ⁻ breaks the original conjugation structure of 3A and results in the redistribution of the charge. The frontier molecular orbitals (MOs) and the Hirshfeld population analysis demonstrate that the long-rang electronic transition between the diethylamino moiety and the dicyanovinyl group in 3A is cut off after the addition of CN ⁻ and a local electronic transition between the quinoline and diethylamino moiety is formed. These changes lead to a blue shift (63 nm) of the fluorescence emission in the nucleophilic addition product (P) compare to 3A.
Scientific objective of this work was elaboration of radiometric method for the development of hydrometallurgical process for recovery of Cu from the copper ore. A neutron activation analysis (NAA) was identified as a very convenient tool for the process investigation. The samples of copper ore were activated in a nuclear reactor. The parameters of the neutron activation were calculated. Radioisotope ⁶⁴Cu was selected as an optimal tracer, and it was used for the investigation of the leaching process. During the experiments, various processes applying leaching media such as sulphuric acid, nitric acid, and organic acids were investigated. The recovery of the metals using sulphuric acid was insufficient, around 10%. Investigated organic media also did not meet expectations. The best results were obtained in experiments with nitric acid. Up to 90% of Cu and other metals were extracted from the copper ore. Copper concentration calculations obtained by NAA were confirmed by inductively coupled plasma mass spectrometry (ICP-MS) technique. Both techniques gave comparable results, but the advantage of the NAA is a possibility for easy online measurements without shutting down or disturbing the system.
The improvement of an evaporation-condensation method allows for successful recovery of elemental sulfur from sulfide concentrates from the zinc industry. Elemental sulfur can be obtained with this method in samples with a low (60%) sulfur content. The effects of heating temperature between 150 °C and 250 °C and heating time up to 120 minutes on the recovery of sulfur are also studied. Elemental sulfur obtained in this way is of high purity and therefore, there is no need for further purification. The treatment of these industrial residue would help removing sulfur from the environment.
Leaching characteristics of a chalcopyrite concentrate received from Kure Copper Mine, Turkey, were investigated in sulfuric acid solutions. The investigation included the effect of leaching temperature, mechanical activation and microwave energy treatment. The extraction of copper was 10.20 % at conventional conditions in 8 h and it increased to 19.14 % with the mechanical activation. Microwave treatment of the concentrates further increased the extraction of copper to 32.21 % at a leaching temperature of 25 °C and to 53.74 % at 75 °C. X-ray analysis revealed the surface chemical alterations of the concentrate samples after microwave irradiation.
In this study, the leaching effect of copper oxide ore was investigated using ammonium chloride solution as leaching agent. The effects of temperature, concentration of ammonium chloride, average particle size and stirring speed on the leaching of copper oxide ore were investigated. The leaching rate increased with increasing solution temperature, concentration, and stirring speed as well as with decreasing average particle size. Ammonium chloride solution can therefore be used as an effective leaching agent for copper extraction from copper oxide ore.
The multimetallic sulfide copper ore containing large amounts of lead and iron was roasted in air atmosphere in the presence of calcium oxide, and the calcinate obtained was leached in sulfuric acid solution to extract copper. Characterization of the raw materials, calcinates and leach residues was conducted by using XRD and SEM/EDS analysis. The calcification mechanism of the complex ore was studied. The effects of temperature, stirring speed, liquid/solid ratio and sulfuric acid concentration on the kinetics and mechanism of copper dissolution from the calcinate were also investigated. Results of experiments show that sulfur retention efficiency in the calcinate achieves 97.77%, and that increasing both reaction temperature and acid concentration are capable of resulting in the increase of dissolution rate of copper. Leaching kinetics follows the un-reacted shrinking core model with a rate controlling step by diffusion through the solid product layer and the corresponding apparent activation energy is calculated as 19.21 kJ/mol, and consequently the rate of the dissolution of copper on aspect of H2SO4 concentration, liquid/solid ratio, and stirring speed can be expressed as .
This study investigates the dissolution kinetics of malachite using an ammonium citrate solution as an alternative leaching agent. The effects of several experimental parameters on the dissolution of malachite were investigated. A kinetic model to represent the effects of these parameters on the dissolution rate was studied. The dissolution rate was determined to increase with increasing solution temperature, concentration, stirring speed and decreasing particle size. Dissolution was observed to be controlled by the shrinking core model for surface chemical reactions. The activation energy of the dissolution process was determined to be 42.59 kJ/mol. The results indicate that the ammonium citrate solution could be used as an effective leaching agent for copper extraction from malachite.
A laboratory-scale method for treating bulk concentrate for reclaiming lead and silver was developed utilizing new hydrometallurgical technology as an alternative to the traditional pyrometallurgical processing. The condition experiments of every chief segment in the whole flowsheet have been systematically investigated, and then the whole hydrometallurgical processing flowsheet was determined. The main contents are followed as: Bulk concentrate was treated using pressure leaching in autoclave, the optimal leaching conditions were determined. The elemental sulphur was deprived from the pressure leaching residue using flotation-distillation. Carbonate conversion -silicofluoric acid leaching on flotation gangue containing lead sulfate using hydrometallurgy was carried. And Leaching silver using thiourea from the residue was carried after extracting lead. Through the whole hydrometallurgy flowsheet, the reclaiming of lead and silver was actualized.
The relationship between copper leaching from malachite ores by using sulphuric acid as the lixiviant and the morphology of malachite particles associated with the gangue minerals has been studied in this work by means of scanning electron microscope. This study was performed on two malachite ores that are associated with the gangue minerals in the forms of thin films and granules. The experimental results have shown that the leach kinetics closely correlated with the morphology of malachite in the ores. Owing to the larger specific surface area, the thin film malachite had a much higher copper leaching rate than the granular malachite. As a result, a higher copper recovery could be achieved from the thin film malachite. © 2011 Institute of Materials, Minerals and Mining and The AusIMM.
In this study, the effect of leaching of malachite was investigated using phosphoric acid solution as leaching agent. The effect of temperature on the leaching of malachite was investigated. The leaching rate increased with increasing solution temperature, and a kinetic model was developed to represent this relationship. The leaching was controlled by the shrinking core model for surface chemical reaction. The activation energy of the leaching process was determined to be 30.65kJ/mol.
The ammonium persulphate (APS) leaching of chalcopyrite concentrate in the presence of
ammonium carbonate was studied. The effects of ammonium carbonate concentration, APS
concentration, leaching time, leaching temperature, solid/liquid ratio and stirring speed were
investigated. Optimum leaching conditions were found as follows: APS concentration is
200 g L21; ammonium carbonate concentration is 200 g L21; leaching time is 180 min; leaching
temperature is 60uC; solid/liquid ratio is 0?04 g mL21; and stirring speed is 400 rev min21. Under
these conditions, copper extraction yield was obtained at about 72%. Furthermore, iron extraction
yield decreased with increasing ammonium carbonate concentration and iron did not pass into
solution under this condition. X-ray and SEM analysis also supported these results. It was
determined that the copper extraction results were satisfactory by way of all experiments were
performed under atmospheric conditions (i.e. low temperature and atmospheric pressure) and
achieved selective copper leaching from chalcopyrite concentrate.
Dissolution of copper from a primary chalcopyrite ore supplied from Damar mine area in Murgul-Artvin, Turkey, has been investigated in sulphuric acid solution after the calcination with and without Fe2O3. The chalcopyrite with and without Fe2O3 were performed by thermogravimetric (TO) analysis, and the calcined chalcopyrite samples were characterized by X-ray diffraction (XRD). In the leaching experiments, the effects of calcination temperature, sulphuric acid concentration, solid/liquid ratio, agitation rate, particle size and dissolution temperature and time on copper dissolution were examined. It was found that Fe2O3 addition contributed to sulphation during the calcination and then copper dissolution.
Solutions containing ammonia allow for selective leaching of copper from a copper ore. In this study, the leaching and kinetics of malachite ore were examined using ammonium acetate solutions as an alternative lixiviant The effects of some experimental parameters on the leaching of malachite ore were investigated. A kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature and stirring speed, and decreasing particle size and solid-to-liquid ratio. It was found that the leaching reaction followed the mixed kinetic control model. The activation energy of this leaching process was determined to be 59.6 kJ moll. Consequently, it was determined that ammonium acetate solutions could be used as an effective leaching agent for copper extraction from malachite ore.
The leaching behavior of a copper flotation concentrate was investigated using ammonium persulfate (APS) in an autoclave system. The decomposition products of APS, active oxygen, and acidic medium were used to extract metals from the concentrate. Leaching experiments were performed to compare the availability of APS as an oxidizing agent for leaching of the concentrate under atmospheric conditions and in an autoclave system. Leaching temperature and APS concentration were found to be important parameters in both leaching systems. Atmospheric leaching studies showed that the metal extractions increased with the increase in APS concentration and temperature (up to 333 K). A similar tendency was determined in the autoclave studies up to 423 K. It was also determined that the metal extractions decreased at temperatures above 423 K due to the passivation of the particle surface by molten elemental sulfur. The results showed that higher copper extractions could be achieved using an autoclave system.
In the present work, the high temperature oxygen pressure leaching behavior of chalcopyrite was studied in sulfuric acid solution. The influence of leaching time, temperature and oxygen partial pressure on leaching process were examined. Leaching rate of copper increased significantly with increasing leaching temperature. Copper recovery reached 87.1% within 2 hours at and 10 atm oxygen pressure, while most of the solubilized iron readily re-precipitates as hematite(). It was confirmed that e main leach reaction of chalcopyrite occurred through oxidation with oxygen under oxygen pressure and high temperature(above ). Because sulfur was oxidized entirely to sulfate, passivating elemental sulfur layer was not formed.
In this study, leaching of chalcopyrite concentrate was investigated in an autoclave system using hydrogen peroxide and sulfuric acid. By decomposition of hydrogen peroxide, the active oxygen formed can provide both high oxidation potential and high pressure in a closed vessel for leaching. Preliminary studies showed that hydrogen peroxide can be used as an oxidant instead of oxygen gas in the autoclave. Central composite design (CCD) was used to examine the effects of the experimental parameters on the copper and iron extraction as a response. The proposed model equation using CCD showed good agreement with experimental data, the correlation coefficients R
2 for copper and iron being 0.84 and 0.86, respectively. The optimum conditions to obtain the main goal of maximum copper and minimum iron extraction from chalcopyrite were determined as to be sulfuric acid concentration of 2.5 M, hydrogen peroxide concentration of 2.3 M, leaching time of 24 minutes, chalcopyrite amount of 3.17 g (in 50-mL solution), stirring speed of 630 rpm, and leaching temperature of 351 K (78 °C). Under the optimum condition, 76 pct of copper and 9 pct of iron were extracted from chalcopyrite concentrate. Extraction yield results of metals indicate that selective leaching of chalcopyrite can be achieved using hydrogen peroxide and sulfuric acid in an autoclave system.
The production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303 K to 323 K [30 °C to 50 °C]) and diffusion through a porous product layer (323 K to 343 K [50 °C to 70 °C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50 kJ/mol, respectively.
Recovery of metallic copper from the leach solution containing copper (II) ions by cementation process using aluminum disc has been examined. Solutions obtained from the leaching of malachite in aqueous acetic acid solutions were used in the study. It was determined that the cementation rate increased with increasing solution concentration, temperature and rotating speed, and decreasing solution pH. The reaction rate fits to the first order pseudo homogeneous reaction model and is controlled by diffusion. The activation energy of this process was calculated to be 32.6 kJ/mol.
The leaching of copper from the tailings of Baifang Copper Mine in Hunan province in China by aqueous ammonia/ammonium chloride solutions has been studied. The tailings belong to a low-grade and high-alkaline copper ore. The effect of leaching time, the concentration of ammonia, solid/liquid ratio and temperature were investigated. The main important parameters in ammonia leaching of copper tailings have been prioritized as solid/liquid ratio, leaching time, temperature and the concentration of ammonia. The optimum leaching conditions are found to be: 4/1 liquid/solid ratio, 4h leaching time, 40°C, 3 mol/L NH4 +. More than 75% of copper was effectively recovered. The dynamical equation of ammonia leaching of copper was obtained and the relation expressions between the grains diameter of tailings and the leaching time are fitted. The results show the grains diameter of tailings has good line relationship with the leaching time and has no relations to the original size of tailings.
Effects of particle size of the zinc sulfide concentrate, leaching temperature, solid-to-liquid ratio and additive amount on pressure acid leaching process of the zinc sulfide concentrate were studied. The results indicate that the additive can improve the reaction kinetics and the conversion rate. And sulfur can be successfully separated from the zinc sulfide concentrate as elemental sulfur. The reasonable experiment parameters are obtained as follows: the leaching temperature 150 °C, oxygen partial pressure 1 MPa, additive amount 1%, solid-to-liquid ratio 1:4, leaching time 2 h, initial sulfuric acid concentration 15%, and particle size less than 44 μm. Under the optimum conditions, the leaching rate of the zinc can reach 95% and the reduction rate of the sulfur can reach 90%.
An attempt was made to investigate the catalytic role of manganese in enhancing the reaction rate with respect to autoclave oxidation of germanium-rich sphalerite concentrates. A series of batch experiments was performed in different conditions to investigate the variables such as temperature and oxygen pressure. Experimental results obtained show that as a catalyst, aqueous divalent manganese can accelerate the leaching of sphalerite concentrates significantly.On a tenté d'étudier le rôle catalytique du manganèse pour améliorer la vitesse de réaction de l'oxydation en autoclave de concentrés de sphalérite riche en germanium. Une série d'expériences discontinues ont été menées dans différentes conditions afin d'étudier les variables telles que la température et la pression d'oxygène. Les résultats expérimentaux obtenus montrent qu'en tant que catalyseur, le manganèse divalent aqueux peut significativement accélérer la lixiviation des concentrés de sphalérite.
Bacterial leaching of minerals is a simple, effective and environmental by benign technology in the treatment of sulphidic ores. This method has been successfully applied for the recovery of copper, gold and uranium in commercial scale for the past 25 years. Efficiency and cost-effectiveness of the bacterial leaching process depend mainly on the activity of bacteria and mineralogical and chemical composition of the ores. Bacterial leaching is based on the activity of mesophilic iron- and/or sulphur-oxidizing bacteria, notably Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans. These bacteria oxidize metal compounds to water soluble metal sulphates by a series of biological and chemical oxidation reactions occurring in leaching medium. After the isolation of above bacteria from acidic mine drainage waters, two oxidation mechanisms (direct and indirect bacterial leaching) have been discussed as related to oxidation/leaching of sulphidic ores in leaching systems. Fully understanding the bacterial leaching mechanisms of sulphidic ores improves the design and operation of bacterial leaching plants. In this article, the importance of various leaching mechanisms employed for metal recovery and their application aspects are critically reviewed with emphasis on copper, lead, zinc and nickel minerals.
The direct sulphation of individual and mixed sulphides of copper and iron has been studied using a steam–oxygen mixture as the oxidant. The investigation showed that copper sulphide formed copper sulphate with this gaseous mixture at 773 K, whereas iron sulphide converted mostly to hematite at this temperature. It was also observed that the mixture of copper–iron sulphides yielded a higher amount of copper sulphate (92.7%) than that obtained (40.0%) from copper sulphide alone in the presence of 10 wt.% ferric oxide. This was mainly attributed to an improved sulphatising environment during the roasting of mixed sulphides. The kinetics study of the CuS–FeS system with a steam–oxygen mixture showed that the copper sulphate formation followed the topochemical model. An activation energy value for this conversion was found to be 30.36 kJ/mol in the temperature range 673 to 773 K. The sulphides and different calcined products obtained were characterised by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and the metallographic studies to examine the path of reaction.
The book covers the general principles of solution chemistry, engineering aspects, and detailed studies of hydrometallurgical processes in 750 pages fully illustrated with drawings and photographs. It contains a selected list of over 250 review articles, proceedings volumes, and books directly related to the subject. Emphasis is laid on chemical reactions, equipment used, and flowsheets.
A critical appraisal has been made of methods that have been proposed for the hydro metallurgical treatment of chalcopyrite concentrates. Those methods in which the primary breakdown of chalcopyrite is effected by leachants are discussed. Methods in which leaching is preceded by pyrometal-' lurgical decomposition of the mineral include selective sulphation and nonoxidizing treatments in which the ratios of _copper, iron and ulphur are changed. No process has yet been found that can replace conventional pyrometallurgical processing, although several have reached the pilot plant stage. The incentives for devising an eco- _nomic hydrometallurgicalprocess for extracting copper frosulphide ores are the avoidance of air pollution and the possibility of recovering iron, elemental sulphur and other nonferrous metals.
An integrated pilot plant for the development of the S-C Copper Process was constructed at Fort Saskatchewan in 1975 and operated in 1976. The pilot plant was designed to treat 9 tonnes per day of a pyritic copper concentrate. A demonstration run conducted during the last quarter of 1976 averaged 90% on-stream time, and confirmed that the process is operable as a stable and integrated unit. Part 2 of this article describes the parameters and equipment developed for thermal activation of chalcopyrite copper concentrates to make them amenable for the dissolution of iron and zinc, and their subsequent separation and recovery. The resulting high-grade copper sulphide was leached with return electrolyte and oxygen to extract 98. 5% of the copper into solution. The copper was electrowon at 65 amps per square meter from purified solution, to produce cathodes analyzing 0. 1 ppm Se, 0. 1 ppm Bi, 4 ppm Pb and 10 ppm S.
Thermal analysis (TA) studies have been made to understand changes in mineralogy that occur when pure sulphide minerals, single concentrates and different Cu-Zn-Pb sulphide concentrates are heated in air. The observed sequential oxidation behaviour of bath the synthetic and natural sulphide minerals is characterised by TA traces that are reasonably reproducible. It is shown that oxidation mechanisms of synthetic analogues during roasting are similar to those of bulk concentrates. The oxidation data thus obtained on sulphide roast products are also found to be useful to characterise some partial leach residues. During ammonia leaching of bulk concentrates, the pyrite grains are practically inert and remain in the leach residue along with oxidated lead compounds and goethite. The TA data for roasting of partially leached samples are compared with those for roasting of untreated feed concentrates. The oxidation behaviour of copper, zinc and lead mineral phases of leach residues is then characterised. The observations are corroborated by chemical phase analysis, X-ray diffraction (XRD) and optical microscopy.
Oxidation in an autoclave with sulfuric acid has been shown to extract 95 to 99 pct of the zinc present, produce a quantitative amount of elemental sulfur, and avoid loss of zinc due to ferrite formation.
Part 1 of this article describes salient features of the Sherritt-Cominco copper process, a hydrometallurgical process developed for refining copper from sulfide concentrates. For the most abundant and relatively refractory chalcopyrite concentrates, the first step of the process is thermal activation with hydrogen to decompose chalcopyrite and pyrite, commonly associated with it, into more reactive sulfides more amenable to leaching. The process was shown to be suitable for handling relatively low-grade concentrates and, in addition, it was capable of high recoveries of associated zinc, molybdenum, nickel and cobalt in saleable form.
The first ammonia leaching plants, applied to copper carbonate and native copper tailings in 1915, were followed more recently by research and development of flowsheets for ammonia leaching of sulfide concentrates. These were applied to two commercial plants. Anaconda's Arbiter Plant started up in 1974 with a design capacity of 36,000 tons/year of cathodes, to be produced by ammonia leaching with oxygen, followed by solvent extraction and electrowinning. The plant shutdown in late 1977 as a result of high maintenance and operating costs, partly due to harsh winters; to complications associated with sulfate disposal; and to changes in mineralogy. BHP's Coloso plant in Chile was designed to produce 80,000 tons/year of cathodes by leaching part of Escondida's concentrate production. Using a similar flowsheet but with air and low temperatures to avoid sulfate production, it started up in late 1994 and shutdown in mid-1998, after failing to reach cathode design capacity, and experiencing problems with its technology. The paper reviews the technologies and also alternative methods for overcoming the problems.
First developed in the 1950s for treating base metal sulfides and refractory gold ores, pressure leaching technology underwent rapid commercial expansion during the 1980s. Initially used to treat nickel concentrates and mattes, pressure leaching has since been extended to the processing of zinc sulfide concentrates and sulfide-containing refractory gold ores. The adoption of pressure leaching in the zinc industry and of pressure oxidation in the gold industry is expected to continue throughout this decade.
The electrochemical behaviour of chalcopyrite has been studied in sulphuric acid solutions with the carbon paste electrode technique. Cyclic voltammetry were performed and the effect of cathodic scan limit, Fe2+ and Cu2+ ion concentrations were followed. The presence of Cu2+ ions in solutions leads to an increase in both the oxidation and the reduction currents, but in either case further increases in currents were observed when Fe2+ ion was added in admixture to the electrolyte. Chalcocite was identified as a product of reactions at extremely high cathodic potentials. The morphology and structure of the produced products after anodic or cathodic treatments of chalcopyrite were examined by the scanning electron microscopy.
Recovery of copper, lead and zinc from complex sulphide concentrates with hydrometallurgical processes has been used as an alternative due to the technological and environmental impacts. In laboratory evaluation of the selective leaching, the metal values in the flotation concentrates were selectively recovered by sulphuric acid (H2SO4) and ferric sulphate (Fe2SO4)3. The experimental parameters studied were pulp density, temperature and time for leaching. From the experimental results, it is concluded that recovery of Cu and Zn from sulphide concentrates can be as high as 89% and 97%, respectively under laboratory conditions.
Chalcopyrite leaching in sulfuric acid solutions depends on the redox potential determined by the concentration ratio of ferric to ferrous ions, and the leaching rate is higher at redox potentials below a critical value. Previously, the authors have proposed a reaction model to interpret this phenomenon. The present study applied the model to interpret the catalytic effect of silver ions on chalcopyrite leaching.The model assumes that at lower potentials, chalcopyrite leaching proceeds in two steps: first, chalcopyrite is reduced by ferrous ions to form Cu2S that is more rapidly leached; next, the intermediate Cu2S is oxidized by ferric and/or dissolved oxygen to release cupric ions. During the chalcopyrite reduction, hydrogen sulfide is released to the liquid phase. Silver ions react with the hydrogen sulfide to form silver sulfide precipitate and decrease the concentration of hydrogen sulfide in the liquid phase, causing a rise in the critical potential of Cu2S formation and broadening of the potential range where rapid copper extraction takes place.To confirm the model, the redox potential dependence of chalcopyrite leaching was investigated in the presence of various concentrations of silver ions with 0.1 kmol m−3 sulfuric acid containing known concentrations of ferrous and ferric ions at 298 K in air. The critical potential increased with increasing concentrations of silver ions. This agrees with the model proposed here but cannot be explained by the conventional model proposed by Miller et al.
Conclusion Examination of calcine from a multihearth roaster and a 4 in diam fluid bed roaster suggest that part of the concentrate feed
remains unreacted while the remainder reacts to completion forming magnetite. No systematic difference is observed between
samples from the fluid bed roaster and the multihearth roaster. An empirical equation is proposed (Eq. [6]) for estimating
magnetite content for different level of sulfur removal.
The work described here was carried out during a vacation school at Mount Isa Mines, Limited, Mount Isa. The author wishes
to thank the management of the company for providing facilities for this work and for permission to publish this paper; the
students Messrs. Bruce, Fisher, Hanrahan, Ho, Hoa, Hutton, Koh, McPherson, Moretto and Schache who carried out the experiments;
and to the laboratory staff at Mount Isa Mines for carrying out the numerous analyses.
A critical appraisal has been made of methods that have been proposed for the hydro metallurgical treatment of chalcopyrite concentrates. Those methods in which the primary breakdown of chalcopyrite is effected by leachants are discussed. Methods in which leaching is preceded by pyrometal-lurgical decomposition of the mineral include selective sulphation and nonoxidizing treatments in which the ratios of copper, iron and sulphur are changed. No process has yet been found that can replace conventional pyrometallurgical processing, although several have reached the pilot plant stage. The incentives for devising an economic hydrometallurgical process for extracting copper from sulphide ores are the avoidance of air pollution and the possibility of recovering iron, elemental sulphur and other nonferrous metals.
Résumé
Une appréciation critique a été faite des méthodes proposees pour le traitement hydrométallurgique des concentrés de chalcopyrite. Les méthodes par lesquelles la deécomposition originale de la chalcopyrite est affectée par les lixiviants, sont décrites. Les méthodes selon lesquelles la lixiviation est précédée par la décomposition pyrométa1lurgique du minerai comprennent la sulphatation sélective et les traitements non-oxydants dans lesquels les concentrations relatives de cuivre, fer et souffre sont changées. Aucun procédé pouvant remplacer les procédés pyrométallurgiques conventionnels n'a encore été trouvé, bien que plusieurs soient parvenus au stade de l'exploitation sur pilote. L'intérêt d'un procédé hydrométallurgique économique, pour l'extraction du cuivre, à partir des minerais de souffre, serait la non-pollution de l'air et la possibilité de récupération du fer, du souffre élémentaire et des autres métaux non-ferreux.
Many industrially important metallurgical processes are accompanied by the emission of light, the analysis of which often supplies useful information concerning the current state of the process while also providing insight into the details of specific process mechanisms. Optical diagnostic techniques are finding an increasingly wide range of application throughout the metallurgical community. This paper discusses the application of emission spectroscopy and imaging techniques to the analysis of such diverse processes as vacuum arc remelting, laser welding, and arc welding. A discussion of these techniques will be presented addressing such subjects as instrumentation, data analysis, the kind of information available and its potential impact on the selection of process parameters. Special attention will be given to discussing the difficulties encountered in applying these diagnostic technologies to “real life” processes in non-laboratory environments.
Natural monoclinic pyrrhotite particles (Fe1−xS) were subjected to pressure leaching by oxygen in sulphuric acid solutions at temperatures ranging between 353 and 453 K (80–180°C). For temperatures below the melting point of sulphur (392 K), the rate of pyrrhotite oxidation shows a moderate dependence on temperature, while it is totally independent of sulphuric acid concentration. Nonetheless, in the absence of oxygen, as much as 30% of the mineral can be dissolved in 0.5 mol/l H2SO4. The conversion data were found to fit well to a shrinking-core model with mixed control by half-order surface reaction and oxidant diffusion though a product layer. Despite the high initial reactivity of pyrrhotite, complete oxidation of the mineral was never achieved at temperatures below 393 K, apparently due to an impervious sulphur product layer covering the particles. Complete pyrrhotite oxidation was achieved at temperatures above the melting point of sulphur and only with the use of lignin sulphonate as dispersant of molten sulphur. By analysing the conversion data with the shinking-core model, pyrrhotite oxidation in the high temperature range (403–453 K) was found to be surface-reaction controlled and of first order with respect to oxygen pressure.
Multi-mineral complex sulphide ores would, typically, not respond well to conventional single mineral flotation due to their fine grained nature. Thus, many complex ore deposits remain undeveloped due to a lack of alternative economic treatment scenarios. The selective leaching process that has been explored is capable of selectively extracting zinc from concentrates containing both sphalerite and chalcopyrite. Unfortunately, many complex sulphide concentrates may also contain appreciable levels of pyrite and galena. Understanding the influence of these mineral on the leaching system is critical to developing a selective leaching process that is easily adapted to a wide variety of concentrate materials.Based on these considerations the selective extraction of zinc using pressure oxidation from multi-mineral concentrates was investigated. Concentrates were artificially produced from pure minerals and ranged in composition of: 25–100% by weight sphalerite, 5–75% chalcopyrite, 0–75% pyrite and 0–75% galena. Zinc was selectively extracted from several Cu/Zn concentrates by utilizing various combinations of temperature and oxygen concentration in the pressure leaching process and the influence of the additions of pyrite and galena was defined. It was discovered that addition of only 5% by weight galena to the selective leaching system retarded the dissolution of sphalerite by up to 13%. Alternatively, a 10% pyrite addition increased zinc extractions while simultaneously decreasing the copper extractions, however, increased concentrations resulted in increased copper extraction and thus, decreased zinc selectivity.
This paper reports a 57Fe Mössbauer spectroscopic study of the kinetics of roasting process of chalcopyrite at two different temperatures and for different time intervals. Iron compounds formed at different stages of roasting have been identified and a possible scheme of transformations has been suggested to explain the observed kinetics.
A Textbook of Hydrometallurgy Kinetics of Metallurgical Processes The influence of chalcopyrite, galena and pyrite on the selective extraction of zinc from base metal sulphide concentrates
- F Habashi
- Qu
- Ebec
- Qu
- Canada Ebec
- F Habashi
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