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Fundamental and practical factors in ammonia leaching of nickel and cobalt ores
Abstract
As indicated in the title, this article gives brief statements of investigations of various fundamental and practical factors of the ammonia leaching process for nickel and cobalt ores. The process was in large scale operation at Nicaro, Cuba, as an emergency measure in World War II. Descriptions of this plant and its operation have been published but these descriptions mainly covered installation and working scale results, and the present article gives a considerable amount of hitherto unpublished data on various phases of the method, including conditions for ore reduction, leaching, distillation, etc. Possibilities as to further development and results of tests on ores other than the Cuban laterites are also included.
... The mineral ores shall be classified as hydrated silicates, clay silicates, and oxide deposits; those are processed by using a variety of processes, including the Caron process. [4][5][6][7] The Caron process is a technology that combines the pyrometallurgical and hydrometallurgical processes, and is based on leaching of previously reduced lateritic ores with ammoniacal-ammonium carbonate solutions ((NH4)2CO3) with the reduction being one of the stages that mostly influence the final extractions [8][9][10]. Also, the use of the Caron process is recommended when the contents of Ni, Fe, and MgO in the lateritic ore exceed 0.9, 25 and 2 %, respectively [8,11]. ...
... [4][5][6][7] The Caron process is a technology that combines the pyrometallurgical and hydrometallurgical processes, and is based on leaching of previously reduced lateritic ores with ammoniacal-ammonium carbonate solutions ((NH4)2CO3) with the reduction being one of the stages that mostly influence the final extractions [8][9][10]. Also, the use of the Caron process is recommended when the contents of Ni, Fe, and MgO in the lateritic ore exceed 0.9, 25 and 2 %, respectively [8,11]. Rodríguez et al. [12] recognize that the Caron process, generates high consumption of fuel oil during its operation, and the reduction stage in the production process induces one of the most important costs. ...
... (3) FeO + CO → Fe + CO2 (4) NiO + CO → Ni + CO2 (5) CoO + CO → Co + CO2 (6) C + CO2 → 2CO (7) Different studies focused on the reduction of lateritic minerals indicating that the particle size [15], temperature profile, and the composition of the reducing atmosphere are the most important variables in the process [16][17][18][19], which is why the use of reducing additives has been one of the most analyzed variables in recent years [20,21]. Some additives used during the reduction in the Caron process are FeS2 [8], NaCl [8,20], CaCl2 [8], S [21,22], Na2SO4 [22] and coal [23][24][25]. Still, it has not been possible to replace the 2.5% of fuel oil (denoted here as FO-2.5 [11,13,25] implemented at the industrial scale. ...
Lateritic ores constitute the main source of raw material for extraction of Ni and Co by the Caron process. Consumption of oil in the reduction furnace is one of the key indicators if the metallurgical process is economical. To date it has not been possible to replace the additive fuel oil that is used at commercial scales, therefore, the aim of this study was to partially replace the oil with bituminous coal on a pilot scale by using a mixture of 2 % coal and 1.25 % oil as the reducer additive. Phases of the reduced/leached ores were analyzed by powder X-ray diffraction, while the metallic state of the ore was determined by leaching the reacted samples with a bromine-ethanol solution followed by the atomic absorption spectrometry analysis. Extractions of Ni and Co were confirmed by leaching the reduced ore with ammoniacal-ammonium carbonate solutions. It was observed that the mixture used as a reducer additive can replace the fuel oil since it allows the adequate transformation of the main mineralogical phases of the laterite ore during the reduction process and the average extraction yields of Ni and Co for 3 and 8 %, respectively. Although the effect of bituminous coal particle size in the process was not analyzed, the reducing mixture ensured that the Caron process was more efficient.
... The process having been utilized for the production of nickel since 1944 (Caron 1950), is applicable to treat limonitic (high iron laterite) plus saprolitic (high magnesium) ores as stated above. The main advantage of the Caron's process is derived from the selective leaching of nickel in the ammoniacal solutions (ammonia-ammonium carbonate) by forming the soluble ammine complexes from the roasted (reductively) lateritic ores while rejecting iron and gangue minerals in the residue. ...
... Ammonia-ammonium carbonate leaching (caron) process. The Caron type processes reported earlier (Caron 1950), having been utilized for the production of nickel for long time (Rhamdhani et al. 2009), have undergone modifications to suit various requirements depending upon the type of ores. Some works in respect of using different gaseous reductants during the reduction roasting steps are reported. ...
... Recently thrust has been given to the use of nitric acid as the lixiviant for processing the laterites. This acid is not only relatively strong oxidant, but adequately dissolves the valuable metals contained in the iron minerals and completely oxidizes (Caron, 1950). The dotted box indicates the practices adopted in Yabulu, Australia (Kyle 2010). ...
In this review, resources of nickel and status of different processes/technologies in vogue or being developed for extraction of nickel and associated metals from both primary and secondary resources are summarized. Nickel extraction from primary resources such as ores/minerals (sulfides, arsenides, silicates, and oxides) including the unconventional one viz., the polymetallic sea nodules, and various secondary resources has been examined. Though sulfide ores after concentration are generally treated by the pyro-metallurgical route, most processes for lateritic ores deal with either the acid leaching at ambient temperature and pressure, or high pressure, and a few based on the microbial treatment and owing to the extensive research on laterites, a special emphasis is put forth in this review. Prominent sources that are covered in some detail include the solid wastes like spent batteries viz., end-of-life nickel-cadmium (NiCd) and nickel metal hydride (NiMH), spent catalysts, and spent/scrap superalloys, and liquid wastes such as copper bleed stream and electroplating effluents. In particular pre-treatment of the spent nickel-based batteries, leaching of metals from the electrode materials in different lixiviants, besides separation/solvent extraction of nickel/other metals from the leach liquors, are highlighted.
... In the reduction roasting-ammonia leaching process, various metal oxide minerals within nickel laterite were reduced by coal at 600-900 • C first. Minerals always tend to undergo phase transformation during reduction roasting, and they will not change much in leaching stage [5,10]. Generally, similar to other non-ferrous metal slag, the processes extracting the valuable metals primarily include acid leaching to recover the Ni and Co [13,14], roasting followed by leaching [15], reduction or direct reduction-wet magnetic separation process to recycle Fe and Cr [16][17][18], and flocculation-magnetic separation to recover iron as magnetite [19][20][21]. ...
... Hydrometallurgical processes, as the effective technologies, are preferred to extract the nickel from limonitic laterite which is a principal nickel-bearing ore [6][7][8]. Therein, reduction roasting-ammonia leaching (RRAL) is one of mature technologies to process the limonitic laterite and has been extensively used in industrial applications for decades [9][10][11][12]. Until now, this process is commercially used in several countries, including Cuba, Australia and Philippines [9]. ...
... In the reduction roasting-ammonia leaching process, various metal oxide minerals within nickel laterite were reduced by coal at 600-900 °C first. Minerals always tend to undergo phase transformation during reduction roasting, and they will not change much in leaching stage [5,10]. Generally, similar to other non-ferrous metal slag, the processes extracting the valuable metals primarily include acid leaching to recover the Ni and Co [13,14], roasting followed by leaching [15], reduction or direct reduction-wet magnetic separation process to recycle Fe and Cr [16][17][18], and flocculation-magnetic separation to recover iron as magnetite [19][20][21]. ...
The reduction roasting ammonia leaching process (RRAL) originally defined by Caron (1950) has been extensively applied to treat low grade nickel laterite and a large amount of slag-containing some valuable metals, has been generated and accumulated over the years since then. However, there are no reports on how to utilize it based on its essential properties. In this investigation, the textural and mineralogical characterization of the typical nickel slag from RRAL inWestern Australia was performed by X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results show that the nickel slag is dominated by magnetite, maghemite, gangue minerals and minor Cr-spinel. The magnetite and maghemite possess simple distribution relationship with other minerals and their particles are highly variable with most over 50 μm, which are easily able to be recovered. In term of the complex association and distribution feature of chromium and nickel minerals, it is very difficult to recovery them. Meanwhile, an economically viable extraction process was proposed to preliminarily utilize the nickel slag based on textural and mineralogical characteristics of the slag, and the magnetic concentrate, assaying about 62% iron grade at over 75% recovery rate, was obtained through the recommended method.
... In the recent past, the increasing attention to ammoniacal leaching of nickel laterite ore using the Caron process has driven considerable efforts to develop other efficient downstream processing of the ammoniacal leach liquor (Caron, 1950;Ilyas et al., 2020). Among them, the application of extractant mixtures inhibiting the co-extraction of metals has been applied by several researchers (Hu et al., 2013;Yang et al., 2016;Zhu et al., 2012). ...
... The stock solution containing 3.0 g•L −1 copper and 3.0 g•L −1 nickel was prepared in ammoniacal solution to simulate the ammoniacal leach liquor of nickel laterite ore obtained via the Caron process (as described elsewhere by Caron, 1950;Sridhar et al., 2010). It needs to be mentioned that many times, cobalt also remains present in the leach liquor, but it has not remained any issue as its co-extraction can be avoided by simply oxidizing cobalt to the higher oxidation state as Co 3+ (Ilyas et al., 2020). ...
In the present study, a complete separation of copper over nickel has been studied from an ammoniacal leach liquor of nickel laterite ore generated via the Caron process. For this purpose, a phenolic oxime (LIX 84-IC) used as the extractant molecule was mixed with tributyl phosphate (TBP) to inhibit the co-extraction of nickel with copper loading into the organic phase. The antagonistic effect of TBP was confirmed by the distribution coefficients to be D mix << D LIX 84-IC + D TBP and negative values of ∆D. The highest separation (β Cu/Ni) of >1329 was yielded using the molar ratio of organic mixture at LIX 84-IC:TBP = 0.4:0.6 at an organic-to-aqueous phase ratio of 1. The thermodynamic properties of copper extraction exhibited an endothermic nature with ΔH° value of 5.4 kJ•mol −1 , indicating the formation of inner-sphere coordination between metal ions and the organic mixture. Further, the stripping of copper from the loaded organic phase was quantitatively achieved by contacting with 1.0 mol•L −1 H 2 SO 4 solution at the unit phase ratio.
... Se ha notado cortezas de intemperismo con rangos de potencias promedios entre 1,0 a 40 metros, siendo la media de 8,0 metros, demostrado por varios informes, (3) lo cual ocupan como valor promedio dentro de la clasificación de uso tecnológico, las lateritas con un 48 % de lateritas de balance (LB), 27 % de laterita fuera de balance (LF) con hierro fuera balance (FF), además de 16 % de silicatos de magnesio de tipo: serpentinitas de balance, serpentina dura y roca estéril en forma de gabros (SB-SD-RE), esto lo convierte en un yacimiento potencialmente explotable por la Empresa Productora Comandante Ernesto Che Guevara (ECG), los datos del quimismo muestran una concentración baja de níquel y elevada concentraciones de hierro, muy característico a minerales de lateritas de baja ley de níquel y escombros lateríticos, además como en otros yacimientos o sectores por ejemplo: Yagrumaje Sur, Camarioca Este y Camarioca Sur, con altas concentraciones de aluminio con un valor promedio de 9,57 %, independientemente que aparezca en algunos sectores muy reducidas altas concentraciones de níquel, de modo general la granulometría es bastante homogénea en la parte superior y media de la corteza de intemperismo de la zona ocrosa, según: (4) , muestra que para los yacimientos de la extensa zona de Yagrumaje, más del 90 % de los granos son menores de 0,074 mm (< 200 mallas), aspecto que en realidad debería estimular el procesamiento industrial, como realmente fue mostrado con este mineral su procesamiento a escala de banco por la tecnología Caron y por el propio autor. (2) Se observó la elevada reducción de los minerales con 10 a 11 % de hierro metálico y extracciones de 86 -88 % de níquel, este comportamiento de los minerales, no es generalizado para todos los sectores del mismo, pero el objetivo del presente artículo es mostrar las interioridades a tener en cuenta para poder obtener un procesamiento adecuado a escala industrial que difieren de los resultados obtenidos a escala de banco, especialmente a la presencia abundante, relativo a menas normales, con respecto a la fase de hierro tipo: (a) lepidocrocita, de su transformación en espinelas oxidadas de (b) maghemitas y con menor presencia de (c)hidrogoethita, fase por excelencia portadora de níquel. ...
... En la formación de los yacimientos lateríticos, los relieves de montañas bajas aplanadas ligeramente diseccionadas, constituyen las principales formas de relieve. Llama la atención que la industria para el procesamiento de los minerales de yacimientos mineros por la tecnología Caron según:(2) ; se encuentran generalmente enmarcados en la explotación de nuevos yacimientos, como la zona ...
The work exposes to the authors consideration a summary of technician-historical aspects related with the Caron process, new approaches and technical procedures, as well as those accumulated given by the experiences acquired by geologist-miners, technologists in investigations in the context of the Cuban industry of the nickel. The XXI century it outlines new and transcendent challenges for the industry, one of them, is related with the variability of the ores processed today in day for this technologies that generate behaviours dissimilar as for metallurgical efficiency and operative to commercial scale. However, the strategies of sustainable development are being defined without an enough diagnosis of the multi-causal problems, originated to the lack of new mineralogical knowledge and of opportune identification in the own dynamics of the industry, based on the priorities of to maintain or to overcome the productive increments from these chords to the standards and international demands. The objective of the work is to show reinterpreted results in a different way, and to complete the square of chemical-mineralogical identification of the fewer of low nickel law, with high iron content and of the lateritic overburden, in search of its previous operative diagnosis, through new procedures of contributed rehearsals that they identify, if they are of industrial prosecution or not, this knowledge are in disposition of the scientific and technological community, based on "New interpretation focus "physical-chemistry" during its thermal treatment in an atmosphere “oxidizer or reduction", as well as of other techniques of magnetic identification and of thermal treatment.
... The main objective of this process is to selectively leach the desired metals from the gangue minerals and metallic iron. Various authors have previously dealt with the details of ammoniacal leaching of pre-reduced laterite ores (1)(2)(3)(4). ...
... The standard reduction potential for reaction [1] is -0.58V and the formal equilibrium potential can be calculated from the Nernst equation: ...
The Caron process involves the oxidative dissolution of pre-reduced iron alloys containing nickel, cobalt and copper in ammoniacal carbonate solutions. This study has demonstrated that passivation is exhibited by nickel and cobalt at higher potentials than that previously established for iron. It is shown that alloys of iron with nickel and cobalt also undergo passivation at low potentials resulting in inhibition of the dissolution of the valuable metals. The potential regions of active dissolution of each of these metals in ammonia-ammonium carbonate solutions have been established. The effect of thiosulfate and cobaltammine complex ions on the dissolution of iron and nickel was found to be significant in that thiosulfate appears to partially prevent the passivation of nickel while the presence of cobaltammine ions leads to lower apparent anodic current densities. Copper does not exhibit passivation under typical leaching conditions and its anodic behaviour appears to be unaffected by the presence of thiosulfate or cobaltammine ions. Possible mechanisms for the passivation processes and for the effects of thiosulfate and cobaltammines on the dissolution are presented.
... Pyrite was initially studied as an additive for roasting in the Caron process and has attracted little attention as an additive in recent years (Sadykhov et al. 2019(Sadykhov et al. , 2020; however, it could be less expensive than other sulfide minerals. Caron (1950) reported nickel recoveries between 91% and 94% after roasting an ore at 900°C for an unspecified time with an unspecified amount of pyrite and an unspecified reducing agent, followed by ammoniacal leaching. studied roasting a saprolite ore at 750°C for an unspecified time and with four pounds of pyrite per ton of ore, and using a reducing gas containing 19% H 2 , 14% CO, 3.5% CO 2 and 63.5% N 2 . ...
Australia has large reserves of limonite and clay-based laterites that are currently underutilized. This review summarizes the latest nickel laterite upgrading studies reported in the literature which use physical beneficiation – only studies reported after the most recent review in 2015 included – as well as high-temperature methods involving oxidation/reduction roasting (with and without additives), sulphidation, and other high-temperature methods. The focus of this review is on upgrading limonite ores, but studies using other types of laterites are also discussed for comparative purposes. Oxidative roasting has proven to be ineffective but producing a magnetic phase by reduction roasting then magnetically separating it from gangue minerals has produced nickel grades and recoveries of up to 14% and 99% respectively with limonite ores. The choice of reductant has negligible effect although hydrogen reduction is predicted to occur at slightly lower temperatures and recoveries are slightly lower compared with carbon-based reductants. The addition of sulfurous compounds improves agglomeration of ferronickel particles, increases the nickel grade and recovery. The highest recovery of 97.91% (grade 13.62%) was reported when sulfur was used as an additive during the roasting of a limonite ore with coal and limestone at 1400°C for 6 h. The results show reduction roasting followed by magnetic separation is effective for upgrading nickel ores, but challenges with this technology are the potentially high reagent usage and temperatures required. The economic feasibility for processing limonite ores via this route is not clear and should be investigated further.
... Q is the adsorption capacity expressed in mg of sorbed Co 2+ per g of ferrihydrite and is equal 220 mg/g at pH 6. This result is in good agreement with bibliography [305], [307], [322], [323]. Figure 48 shows the evolution of Co 2+ concentration versus time in the pH range 1.7 to 6. ...
Ce travail de thèse s'inscrit dans le cadre du projet ADEME CALICE "Procédé de captage et libération du CO2 assisté par électrolyse utilisant des matériaux de type brucitique". Il vise à développer une technologie de rupture dans le domaine du traitement d'effluents gazeux contenant du CO2, en vue de sa valorisation. Le procédé repose sur la modification des valencedes espèces redox actives constitutives des feuillets du matériau pour moduler sa capacité d'échange anionique et assurer le captage et la libération du CO2, sous forme d'anions inorganiques. Décrits dans la bibliographie comme matériaux capables d'assurer jusqu'à 5000 cycles électrochimiques d'oxydation et de réduction, les HDLs Co/Fe ont été sélectionnés comme matériaux d'intérêt, susceptibles d'assurer le captage et la libération des anions HCO3- et/ou CO32- ; les atomes de cobalt, aux degrés d'oxydation II et III, constituent les entités électroactives. Le mécanisme de formation des HDLs Co/Fe, par coprécipitation à pH variable, a été étudié pour des valeurs de pH comprises entre 2 et 11. La ferrihydrite, sur laquelle Co2+ s'adsorbe, est l'intermédiaire réactionnel clé de la synthèse des HDLs Co/Fe. L'adsorption de Co2+ est responsable de phénomènes d'oxydoréduction qui induisent la formation d'un HDL métastable (FeII/CoIII) dont l'évolution conduit au matériau HDL final (CoII/FeIII). L'analyse du comportement thermique des matériaux a permis de préciser la formulation des HDLs synthétisés (Co3,14Fe2(OH)10,28(CO3), xH2O) et de définir leur domaine thermique d'application potentielle (inférieur à 160°C) en vue de leur utilisation dans un procédé de capture du CO2 contenu dans des gaz chauds issus d'installations industrielles dont la température peut atteindre 600°C. Dans le cadre de l'intégration énergétique du procédé, des échangeurs thermiques, pour la récupération d'énergie ou le préchauffage de certains flux, devront par conséquent être mis en œuvre. Le couplage des techniques électrochimiques, gravimétrique et de diffraction de rayons X, au synchrotron Soleil, a permis de déterminer le potentiel standard apparent du couple CoIII/CoII (1,23 V/ESH), la constante cinétique d'oxydo-réduction du couple CoIII/CoII constitutifs des feuillets du HDL (k° = 2,5 x10-4 m/s, a = 0,6, b = 0,4) et d'analyser les mécanismes physico-électrochimiques associés à l'oxydation de CoII et à la réduction de CoIII de telle sorte que : CoII6CoIIIFeIII2[(OH)16][CO3], zH2O + 0,5x CO32- ⇆ CoII6-xCoIIIxFeIII2[(OH)16][CO3](1+0,5x),(z-z')H2O + z'H2O + xe- Le procédé de captage et libération du CO2 a été mis en œuvre sur des solides de type HDLs utilisés sous forme de pulpes dans des réacteurs électrochimiques à deux compartiments, en milieu aqueux. Les analyses ont été conduites dans une solution tampon NaHCO3/Na2CO3 à pH 9 (FI 0,05M). Le couplage des électrolyses à potentiel imposé et du suivi de l'alcalinité a permis de calculer le rendement des réactions redox. Le pourcentage de Co redox actif est compris entre 5 et 12%. Le coefficient de transport de matière électroactive vers la surface de l'électrode, km, est égal à 4,72x10-5 m/s ; les constantes réactionnelles électrochimiques d'oxydation et de réduction du cobalt, qui quantifient l'efficacité de l'interaction matière/électrode, sont respectivement égales à 1,48x10-3 s-1 et 1,27x10-3 s-1. Dans les conditions optimales de cyclage (0,84 et 0,24 V/ESH respectivement pour l'oxydation et la réduction de Co, avec une concentration de Co de 4 10-3 M), le rendement du procédé est supérieur à 170 kg de CO2 par tonne de HDL et par cycle. Ce résultat laisse présager des perspectives intéressantes pour l'optimisation d'un procédé, assisté par électrolyse, de capture et de libération du CO2 par des HDLs Co/Fe.
... Oxidation roasting has also been evaluated based on improving Ni extractability during hydrochloric acid leaching (Zhu et al. 2012) or selective oxidation of iron sulfides prior to ammoniacal leaching (Leo and Georg 1954). The Caron process for extraction of Ni and Co from oxidized ores was patented in 1924 by M. H. Caron (Caron 1950) and involves reduction roasting to convert Ni and Co oxides to their respective metals followed by leaching of the reduced calcine in oxygenated ammonia-ammonium carbonate to dissolve Ni and Co (Forward, Kudryk, and Samis 1948). Based on the success of the Caron process in treating oxidized Ni ores at the Nicaro nickel plant, Cuba, the process was adapted by Forward, Kudryk, and Samis (1948) and Queneau, Sproule, and Illis (1949) to process sulfide ores and concentrates. ...
The following review is Part III of a series concerned with the direct hydrometallurgical processing of nickel sulfide flotation concentrates. In the first part of this series, piloted leaching processes and commercial nickel sulfide operations that employed direct hydrometallurgical processing were comprehensively reviewed. In the second part of this series, laboratory investigations into pressure leaching of nickel sulfide concentrates were critically analyzed. In Part III of this series, laboratory investigations into the leaching of nickeliferous sulfide concentrates at ambient pressure are reviewed, and the challenges and research opportunities in the direct leaching of nickel sulfide flotation concentrates are summarized. The majority of the published studies on atmospheric leaching of nickel sulfide flotation concentrates have focused on leaching in chloride media due to the faster leaching kinetics in chloride lixiviants relative to sulfate media; bioleaching due to the perceived environmental advantages over other leaching systems; and pyrometallurgical pre-treatments to render refractory sulfide minerals more amenable to subsequent leaching.
... Q is the adsorption capacity, expressed in mg of sorbed Co 2+ per g of ferrihydrite, and is equal to 220 mg·g −1 at pH 6. This result is in good agreement with the literature [66,68,93,94]. Figure 9 shows the evolution of Co 2+ concentration versus time in the pH range from 2 to 2.2. Data were extracted from Figure S2. ...
Co/Fe-based layered double hydroxides (LDHs) are among the most promising materials for electrochemical applications, particularly in the development of energy storage devices, such
as electrochemical capacitors. They have also been demonstrated to function as energy conversion catalysts in photoelectro-chemical applications for CO2 conversion into valuable chemicals. Understanding the formation mechanisms of such compounds is therefore of prime interest for further controlling the chemical composition, structure, morphology, and/or reactivity of synthesized materials.
In this study, a combination of X-ray diffraction, vibrational and absorption spectroscopies,
as well as physical and chemical analyses were used to provide deep insight into the coprecipitation
formation mechanisms of Co/Fe-based LDHs under high supersaturation conditions. This
procedure consists of adding an alkaline aqueous solution (2.80 M NaOH and 0.78 M Na2CO3) into a cationic solution (0.15 M CoII and 0.05 M FeIII) and varying the pH until the desired pH value
is reached. Beginning at pH 2, pH increases induce precipitation of FeIII as ferrihydrite, which is the pristine reactional intermediate. From pH > 2, CoII sorption on ferrihydrite promotes a redox
reaction between FeIII of ferrihydrite and the sorbed CoII. The crystallinity of the poorly crystalized ferrihydrite progressively decreases with increasing pH. The combination of such a phenomenon with the hydrolysis of both the sorbed CoIII and free CoII generates pristine hydroxylated FeII/CoIII LDHs at pH 7. Above pH 7, free CoII hydrolysis proceeds, which is responsible for the local dissolution of pristine LDHs and their reprecipitation and then 3D organization into CoII4FeII2CoIII2 LDHs.
The progressive incorporation of CoII into the LDH structure is accountable for two phenomena: decreased coulombic attraction between the positive surface-charge sites and the interlayer anions and, concomitantly, the relative redox potential evolution of the redox species, such as when FeII is re-oxidized to FeIII, while CoIII is re-reduced to CoII, returning to a CoII6FeIII2LDH. The nature of the interlamellar species (OH−, HCO3−, CO32− and NO3−) depends on their mobility and the speciation of anions in response to changing pH.
... Similarly, the Arbiter processes developed in the 1970s used a direct ammoniacal oxidative pressure leaching process to extract copper from copper concentrates (Kuhn et al., 1974). Additionally, recovery of cobalt and nickel from both lateritic ores (Caron, 1950) and pyrrhotite flotation concentrates (Schlitt, 1980) using ammonia-ammonium carbonate solutions have been employed. Further, recent pilot-scale applications of commercial ammoniacal leaching is highlighted in Radmehr et al. (2013). ...
The dissolution of copper during the leaching of chalcopyrite in ammonia solutions is an attractive alternative to acid sulfate leaching in the treatment of ores with high consumption of acid. Despite considerable research into this complex leaching system, a lack of understanding of the fundamental chemical drivers has delayed the implementation of the ammonia process. In the present study, various ammonium salts solutions (chloride, sulfate, carbonate) have been used to study the effect of ion association on the dissociation constant of the ammonium ion at temperatures of 25 and 35 °C. Experimental and calculated solubilities of Cu²⁺ have been obtained under different conditions and plotted in speciation distribution diagrams, in other to assess the accuracy of predictions using available thermodynamic properties.
Ion association was found to significantly affect the dissociation constant of the ammonium ion in solutions containing sulfate, chloride and carbonate anions; thus, influencing the free ammonia concentration in solution. Increasing temperature from 25 to 35 °C was found to decrease the dissociation constant of the ammonium ion. These findings highlight the importance of using the correct anionic ligands for the ammonium ions and temperature in order to obtain high dissolution of copper.
It has been established that solubility of copper in ammonia solution is affected by the anionic ligands, temperature and addition of chloride ions. The NH3 ligand forms strong coordination compounds with cupric or cuprous ions depending on the anionic ligand, generating an increase in solubility between pH 8.5 and 10.0. The present study, therefore, identifies important constraints on the role of varying anion associated with ammonia, temperature, pH, and addition of chloride ions and the inter-dependence of these factors in controlling Cu²⁺ solubility in ammoniacal systems. The results from the present study provides experimental pKa values and solubility constants of the various ammoniacal systems to provide commercial processing via ammoniacal routes the optimal conditions in which to maximise Cu recovery and maintain free ammonia at levels to minimise volatility and loss. The findings are directly beneficial to future commercial application employing effective ammonium-anion lixiviant strategies in the sustainable recovery of Cu.
... Anaconda's Arbiter process and BHP's Escondida process were developed to extract copper from sulfide flotation concentrates utilizing ammonia-ammonium sulfate as a lixiviant (Duyvesteyn and Sabacky 1993;Kuhn, Arbiter, and Kling 1974). Ammonia-ammonium lixiviants have been utilized for the extraction of Ni and Co from lateritic ores via the Caron process, which involves reduction roasting followed by ammonia-ammonium carbonate leaching (Caron 1950) and was in use at the Yabulu refinery in Queensland for processing laterite ores (now in care and maintenance) and by Inco (now Vale) until 1982 for treating pyrrhotite concentrates via a modified process (see Section 3.6.2). The only (2012); Hourn, Turner, and Holzberger (1996), Stieper (2018) commercialized ammonia leaching process to date for the direct treatment of nickel sulfide concentrates is the Sherritt-Gordon ammonia pressure leaching process which is currently in use at Fort Saskatchewan, Canada, and Kwinana, Western Australia. ...
The extraction of nickel (Ni) from sulfide resources commences with flotation to produce a concentrate which is then smelted to produce a nickel-enriched phase called matte, and further refined to produce pure Ni products as well as by-products, such as cobalt (Co), copper (Cu) and precious metals. However, the traditional concentrate smelting-matte refining process, whilst technologically robust, is capital intensive and suffers from several environmental and technical issues such as sulfur dioxide emissions, poor recovery of cobalt and difficulty processing concentrates high in magnesia and arsenic without appropriate blending with high grade concentrates to dilute the concentration of these species. The direct hydrometallurgical processing of nickel sulfide concentrates and whole ores may be a remedy to these issues and hydrometallurgy offers several advantages over pyrometallurgy such as potentially lower capital costs, the ability to process lower grade materials and produce marketable metals or compounds directly from ore/concentrate. Despite the advantages of hydrometallurgy over traditional base metal sulfide smelting, the hydrometallurgical processing of nickel concentrates has been limited to a small handful of commercial operations, some of which only produce an upgraded intermediate for pyrometallurgical processing. In Part I of this three-part series, a comprehensive review of piloted processes for direct hydrometallurgical processing of nickel sulfide concentrates is presented, followed by a survey of industrial operations which have carried out direct leaching of nickel sulfide concentrates. A review of research activities and challenges/opportunities in the direct hydrometallurgical processing of nickel sulfide concentrates are presented in Part II and Part III of this series.
... Q is the adsorption capacity, expressed in mg of sorbed Co 2+ per g of ferrihydrite, and is equal to 220 mg·g −1 at pH 6. This result is in good agreement with the literature [66,68,93,94]. Figure 9 shows the evolution of Co 2+ concentration versus time in the pH range from 2 to 2.2. Data were extracted from Figure S2. ...
Co/Fe-based layered double hydroxides (LDHs) are among the most promising materials for elec-trochemical applications, particularly in the development of energy storage devices, such as elec-trochemical capacitors. They have also been demonstrated to function as energy conversion cata-lysts in photoelectrochemical applications for CO2 conversion into valuable chemicals. Under-standing the formation mechanisms of such compounds is therefore of prime interest for further controlling the chemical composition, structure, morphology, and/or reactivity of synthesized materials. In this study, a combination of X-ray diffraction, vibrational and absorption spectrosco-pies, as well as physical and chemical analyses were used to provide deep insight into the co-precipitation formation mechanisms of Co/Fe-based LDHs under high supersaturation conditions. This procedure consists of adding an alkaline aqueous solution (2.80 M NaOH and 0.78 M Na2CO3) into a cationic solution (0.15 M CoII and 0.05 M FeIII) and varying the pH until the de-sired pH value is reached. Beginning at pH 2, pH increases induce precipitation of FeIII as ferrihy-drite, which is the pristine reactional intermediate. From pH > 2, CoII sorption on ferrihydrite promotes a redox reaction between FeIII of ferrihydrite and the sorbed CoII. The crystallinity of the poorly crystalized ferrihydrite progressively decreases with increasing pH. The combination of such a phenomenon with the hydrolysis of both the sorbed CoIII and free CoII generates pristine hydroxylated FeII/CoIII LDHs at pH 7. Above pH 7, free CoII hydrolysis proceeds, which is respon-sible for the local dissolution of pristine LDHs and their reprecipitation and then 3D organization into CoII4FeII2CoIII2 LDHs. The progressive incorporation of CoII into the LDH structure is ac-countable for two phenomena: decreased coulombic attraction between the positive sur-face-charge sites and the interlayer anions and, concomitantly, the relative redox potential evolu-tion of the redox species, such as when FeII is re-oxidized to FeIII, while CoIII is re-reduced to CoII, returning to a CoII6FeIII2 LDH. The nature of the interlamellar species (OH−, HCO3−, CO32− and NO3−) depends on their mobility and the speciation of anions in response to changing pH.
... The Caron process is a technology that combines the pyrometallurgical and hydrometallurgical process, and it is based on the leaching of previously reduced lateritic ores with ammoniacal ammonium carbonate solution; the reduction being one of the stages that most influences the final extractions [8][9][10][11][12][13][14][15]. ...
Lateritic ores are currently considered as the fundamental raw material for the extraction of Ni and Co through the Caron process. This directly affects the temperature control of the hearth 6 of reduction furnaces from the injection of the post-combustion air into the metallurgical process. To date, there is no consensus on the part of the researchers about the positive or negative effect that this variable generates in Ni and Co extractions; therefore, this research reports the results obtained by reducing a lateritic ore on a pilot plant scale, evaluating different temperature levels in the hearth 6, as the post-combustion air was fed. It was found that the injection of the post-combustion air in the reduction furnaces decreases the Ni extractions with respect to the Co extractions, the behavior is becoming more irregular by showing maximum and minimum values. The best result of the present study is obtained when working in an operational condition without the injection of post-combustion air with a temperature of 495 °C in hearth 6 of the reduction furnace.
... El proceso metalúrgico Caron (1950) emplea licor amoniacal, el cual es una mezcla de agua, amoníaco y sólidos en suspensión que se transporta por medio de bombas centrífugas a temperaturas desde 20 o C hasta 64 o C. Esta mezcla, según el principio de Gibbs, puede expresarse como una función de dos variables: la temperatura de saturación y la concentración, existiendo un único valor de presión de saturación para cada valor de concentración. ...
This article exposes the effect bubbles implosion causes on buckets on the liquor from carbonate-ammonia leaching (mixture of water, ammonia and particles in suspension) of ferronickel lateritic ores. Based on the previous results that establish a relationship between the bubbles’ size and the ammonia concentration of the liquor, the microstructure of a Hastelloy C 276 steel blade affected by cavitation was analyzed. It was also obtained that affectations are smaller in the initial area of the bucket than the distal parts, where complete perforations can be produced in the metal, what is associated to the fact that bubbles develop a great size at a concentration of 34% of ammonia in the liquor and implode at the exit of the bucket producing more intense pressure waves than those generated by the bubbles formed at 27% and that implode in the initial zone. It is concluded that the microstructural changes in the bucket material are closely related to the concentration of ammonia in the liquor making pitting, cracks, and cavities larger when the concentration of ammonia is maximum (34%).
... El proceso metalúrgico Caron (1950) emplea licor amoniacal, el cual es una mezcla de agua, amoníaco y sólidos en suspensión que se transporta por medio de bombas centrífugas a temperaturas desde 20 o C hasta 64 o C. Esta mezcla, según el principio de Gibbs, puede expresarse como una función de dos variables: la temperatura de saturación y la concentración, existiendo un único valor de presión de saturación para cada valor de concentración. ...
Resumen En bombas centrífugas que trasiegan licores industriales amoniacales los daños por cavitación se acentúan debido a la composición de este fluido. Este artículo expone el efecto que sobre los álabes produce la implosión de burbujas en el licor producto de la lixiviación carbonato-amoniacal (mezcla de agua, amoníaco y partículas en suspensión) de menas lateríticas ferroniquelíferas. A la luz de resultados previos que establecen una relación entre el tamaño de las burbujas y la concentración de amoníaco del licor, se analizó la microestructura de un álabe de acero Hastelloy C 276 afectado por la cavitación. Se obtuvo que en la zona inicial del álabe las afectaciones son menores que hacia las partes distales, donde llegan a producirse perforaciones completas en el metal, lo cual se asocia a que a concentración de 34 % de amoníaco en el licor las burbujas desarrollan gran tamaño e implosionan a la salida del álabe produciendo ondas de presión más intensas que las que generan las burbujas que se forman a 27 % y que implosionan en la zona más cercana al eje del impelente. Se concluye que los cambios microestructurales en material del álabe guardan estrecha relación con la concentración de amoníaco en el licor, siendo las grietas, picaduras y cavidades de mayores dimensiones cuando la concentración de amoníaco es máxima (34 %).
... El proceso metalúrgico Caron (1950) emplea licor amoniacal, el cual es una mezcla de agua, amoníaco y sólidos en suspensión que se transporta por medio de bombas centrífugas a temperaturas desde 20 o C hasta 64 o C. Esta mezcla, según el principio de Gibbs, puede expresarse como una función de dos variables: la temperatura de saturación y la concentración, existiendo un único valor de presión de saturación para cada valor de concentración. ...
En bombas centrífugas que trasiegan licores industriales amoniacales los daños por cavitación se acentúan debido a la composición de este fluido. Este artículo expone el efecto que sobre los álabes produce la implosión de burbujas en el licor producto de la lixiviación carbonato-amoniacal (mezcla de agua, amoníaco y partículas en suspensión) de menas lateríticas ferroniquelíferas. A la luz de resultados previos que establecen una relación entre el tamaño de las burbujas y la concentración de amoníaco del licor, se analizó la microestructura de un álabe de acero Hastelloy C 276 afectado por la cavitación. Se obtuvo que en la zona inicial del álabe las afectaciones son menores que hacia las partes distales, donde llegan a producirse perforaciones completas en el metal, lo cual se asocia a que a concentración de 34 % de amoníaco en el licor las burbujas desarrollan gran tamaño e implosionan a la salida del álabe produciendo ondas de presión más intensas que las que generan las burbujas que se forman a 27 % y que implosionan en la zona más cercana al eje del impelente. Se concluye que los cambios microestructurales en material del álabe guardan estrecha relación con la concentración de amoníaco en el licor, siendo las grietas, picaduras y cavidades de mayores dimensiones cuando la concentración de amoníaco es máxima (34 %).
... Notably, the ammonia leaching of Cu and Ni from various raw materials (from the leaching of native copper ore at Lake Superior District and Caron's process for nickel laterite ore from the early 20th century to the recent applications for metal recycling from e-waste) has been well established and reviewed (Caron, 1950;Habashi, 2005;Mishra et al., 2011;Radmehr et al., 2013;Srivastava et al., 2013;Sun et al., 2015;Yoo and Kim 2012). ...
The ammoniacal leaching of surface-coated metals from automobile-discarded ABS plastics followed by their recovery through solvent extraction has been investigated. The leaching of ABS (typically containing 4.1% Cu, 1.3% Ni, and 0.03% Cr) could efficiently dissolve the ammine complexes of Cu and Ni, leaving Cr unleached as fine particles. The optimization studies for achieving the maximum efficiency revealed that the leaching of metal ions in different ammoniacal solutions follows the order CO3²⁻ > Cl⁻ > SO4²⁻. The leaching carried out in a carbonate medium by maintaining the total NH3 concentration 5.0 M at a NH4OH/(NH4)2CO3 ratio of 4:1, pulp density of 200 g/L, agitation speed of 400 rpm, temperature of 20 °C, and time of 120 min yielded the optimum efficiency of >99% Cu and Ni (i.e., 8.14 g/L and 2.57 g/L, respectively, in the leach liquor). Subsequently, the solvent extraction of metals from ammoniacal leach liquor as a function of extractant (LIX 84-I) concentration and organic-to-aqueous (O:A) phase ratio was examined. Based on the extraction data, a three-stage counter-current extraction at O:A = 1:1 was validated using 0.8 M LIX 84-I, yielding the quantitative extraction of both metals into the organic phase. Thereafter, the stripping of metals in acid solutions indicated that 0.5 M H2SO4 could quantitatively strip Ni from the loaded organic phase; however, ∼27% Cu was also co-stripped. The rest of Cu from the Ni-depleted organic phase was separately stripped with 1.0 M H2SO4 that can be directly sent to the electrowinning process. On the other hand, the co-stripped metals from the acidic solution can be easily separated, again using LIX 84-I as the extractant, by adopting the pH-swing method. Finally, a process has been proposed for the hydrometallurgical recovery of surface-coated metals from waste ABS plastics; that does not affect the physicochemical characteristics of the polymer substances for their reuse.
... The main methods that have been used include direct smelting of the ore to either matte or ferronickel in electric arc or blast furnaces; reduction roasting followed by either ammonium carbonate leaching (Caron process), (Caron, 1924(Caron, , 1950 or sulphuric acid leaching under pressure (Moa Bay process), (Carlson and Simons, 1960;Whittington and Muir, 2000). Many other processes have also been proposed. ...
The development of a hydrometallurgical hydrochloric acid-based leaching process for the treatment
of nickeliferous laterites of various types is described. A key step is the separation and concentration of the
. nickel in the leach liquor (1-5 gIL) from magnesium and/or iron to a tenor compatible with electrowinning or
hydrogen pressure reduction. This can be achieved using solvent extraction with Cyanex 301, Cyanex 302 or
with Versatic 10, which displayed the best extraction characteristics. Cyanex 301 showed excellent selectivity
for Ni but was very difficult to strip, except with high concentrations of acid. Cyanex 302 seemed suitable hut
co-extraction of magnesium was appreciable.
... Pyrometallurgical routes involving reduction roasting, hydrometallurgical processes involving acid leaching or a combination of both have been applied to recover nickel from laterite ores. One such example is the Caron process, where the ore is reduced at 700° C in a reducing atmosphere to convert nickel into a metallic state, followed by selective leaching with ammoniaammonium carbonate solution ( Caron, 1950). Microwave radiation or a combined method such as segregation roasting of laterites followed by flotation or magnetic separation, as well as microbial aspects of mineral beneficiation, have also been attempted to recover nickel and other metal values ( Iwasaki et al., 1966;Kawatra and Natarajan, 2001;Zhai et al., 2009). ...
The dissolution behavior of lateritic nickel ore containing 1.2% Ni, 40.6% Fe, 9.5% SiO2 and 9.59% MgO by sulfuric acid was investigated. The ore was characterized adequately by different techniques such as chemical analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), thermal analysis and Fourier transform infrared (FTIR) spectroscopic measurements. The characterization results did not reveal any distinct mineral phase for nickel; it was associated with mineral phases like goethite, hematite, chromite and serpentine in various proportions. The beneficiation studies by hydrocyclone, magnetic separation and flotation did not enrich the nickel value. Reduction roasting followed by magnetic separation indicated only 2%Ni with 28.9% yield. Consequently, the recovery of nickel values from the lateritic ore by acid leaching under different conditions was studied. The kinetics of leaching obey the first order rate equations. The recovery of nickel was found to be influenced by temperature. It was observed that at an acid concentration of 2M, leaching temperature 363 K, time 240 min and solid-to-liquid ratio of 1:10, it is possible to leach out more than 95% Ni.
... The main methods that have been used include direct smelting of the ore to either matte or ferronickel in electric arc or blast furnaces; reduction roasting followed by either ammonium carbonate leaching (Caron process), (Caron, 1924(Caron, , 1950 or sulphuric acid leaching under pressure (Moa Bay process), (Carlson and Simons, 1960;Whittington and Muir, 2000). Many other processes have also been proposed. ...
... An alternative process, a modified version of that first described by Caron in 1950 [3,4] and known by his name, based on ammonia/ammonium carbonate leaching of reduction-roasted laterite, has seen some commercial success, notably by Níquel Tocantins in Brazil and Queensland Nickel (BHPBilliton) in Australia, although there have been other operations using this process. Its major disadvantage is that cobalt recovery is limited, often as low as 40%. ...
Chesbar Resources Inc.1 is developing a nickel-cobalt laterite project in Guatemala, Central America, by applying existing atmospheric chloride technology to a known resource. The tropical laterite project has an inferred resource of 133 million tonnes grading 1.51% nickel, which represents ∼20% of Chesbar's land holdings in Guatemala. Within its boundaries, the Sechol area has a measured resource of 14 million tonnes grading 1.46% nickel and 0.08% cobalt, and an indicated resource of 23 million tonnes grading 1.34% nickel and 0.08% cobalt. Notwithstanding the impressive overall resource, the company has taken an innovative approach to a laterite project and is concentrating on El Inicio, a high-grade starter pit with five million tonnes grading 2.1% nickel and 0.08% cobalt. The process flowsheet is based on atmospheric chloride leaching in a slightly acidic magnesium chloride brine, solution purification by recycled magnesia, precipitation of a mixed nickel/cobalt hydroxide intermediate product, and lixiviant regeneration by modified pyrohydrolysis technology. Initial results suggest that >90% of the contained nickel and cobalt in the non-magnetic fraction of the feed can be recovered, with <5% of the iron leaching. A metallurgical scoping study has established preliminary capital and operating costs for a production facility at a proposed rate of 20,000 tonnes per year of nickel as the intermediate mixed hydroxide. A preliminary assessment of producing a magnesium oxide by-product has also been carried out. This paper reports on the current development of the project and highlights the advantages of working in a chloride medium at atmospheric pressure and slightly elevated temperatures.
... The standard reduction roasting-ammonia leaching process originally defined by Caron (1950) has been proven to be the most successful treatment for most oxide ores. Until now, this process is commercially used in several countries, including Cuba (Nicaro), Australia (Townsville), the Philippines (Marinduque), and China (Qinghai). ...
... Pyrometallurgical routes involving reduction roasting, hydrometallurgical processes involving acid leaching or a combination of both have been applied to recover nickel from laterite ores. One such example is the Caron process, where the ore is reduced at 700° C in a reducing atmosphere to convert nickel into a metallic state, followed by selective leaching with ammoniaammonium carbonate solution (Caron, 1950). Microwave radiation or a combined method such as segregation roasting of laterites followed by flotation or magnetic separation, as well as microbial aspects of mineral beneficiation, have also been attempted to recover nickel and other metal values (Iwasaki et al., 1966;Kawatra and Natarajan, 2001;Zhai et al., 2009). ...
The dissolution behavior of lateritic nickel ore containing 1.2% Ni, 40.6% Fe, 9.5% SiO 2 and 9.59% MgO by sulfuric acid was investigated. The ore was characterized adequately by different techniques such as chemical analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), thermal analysis and Fourier transform infrared (FTIR) spectroscopic measurements. The characterization results did not reveal any distinct mineral phase for nickel; it was associated with mineral phases like goethite, hematite, chromite and serpentine in various proportions. The beneficiation studies by hy-drocyclone, magnetic separation and flotation did not enrich the nickel value. Reduction roasting followed by magnetic separation indicated only 2%Ni with 28.9% yield. Consequently, the recovery of nickel values from the lateritic ore by acid leaching under different conditions was studied. The kinetics of leaching obey the first order rate equations. The recovery of nickel was found to be influenced by temperature. It was observed that at an acid concentration of 2M, leaching temperature 363 K, time 240 min and solid-to-liquid ratio of 1:10, it is possible to leach out more than 95% Ni.
In recent times, ammoniacal leaching has received widespread attention in extractive metallurgy, mainly to process the lateritic ores of nickel. Copper has always been found as the companion metal ion in ammoniacal solutions, whose effective separation is highly desirable to achieve product purity. Usually, LIX series extractants are applied to co-extract and their selective stripping is a function of acid concentration, resulting in large hold-up volumes of the solvent. Henceforth, to achieve high selectivity in the extraction step, we studied the antagonistic effect of tributyl phosphate (TBP) mixing with LIX 84-IC, which inhibited nickel extraction with copper from the ammoniacal solution. The determined distribution coefficient values as D(mix) < < D(LIX 84-IC) + D(TBP) and negative ∆D values clearly demonstrate the antagonistic effect caused by the extractant mixture. The highest separation factor, i.e., β(Cu/Ni) = 1330, was obtained at a molar mixture of LIX 84-IC:TBP = 0.4:0.6 and an organic-to-aqueous (O:A) phase ratio of 1. The extraction thermodynamics indicate an endothermic process (ΔH° = 5.4 kJ/mol) that forms the inner-sphere organometallic complexation. The copper-loaded organic phase was quantitatively stripped by contacting it with a 1.0 mol/L H2SO4 solution at an O:A ratio of 1.
There is a growing interest in extracting valuable metals from secondary resources due to the depletion of primary metal resources and environmental concerns associated with solid wastes. As a result of the challenges associated with traditional extraction lixiviants, non-conventional lixiviants, particularly ammoniacal reagents, have gained a lot of attention in hydrometallurgical processes for metal extraction or recycling techniques. The present article reviews the use of ammonia and ammonia-ammonium salt leaching systems to extract valuable metals from secondary resources. This paper highlights the use of ammoniacal leaching for successful extraction of metals like nickel, cobalt, copper, zinc, vanadium, and molybdenum from diverse sources such as spent batteries, printed circuit boards, spent catalyst, sludge, dust, slag, and fly ash. Moreover, this paper summarizes and discusses research on the comparative outcomes of several ammonia leaching systems from these secondary resources. Furthermore, the potential benefits and challenges of using the ammonia leaching method for metal extraction from these sources are highlighted. Key advantages of ammoniacal leaching are low toxicity, cheap cost, high metal selectivity, closed-loop ammonia regeneration and lower operational costs. Overall, this article has demonstrated that ammonia leaching is a viable technique for extracting valuable metals from secondary resources.
Awaruite is a native nickel-iron alloy with high nickel content and mainly present in serpentinized ultramafic rocks. Recent discoveries have demonstrated the potential for awaruite to contribute to the economics of a nickel deposit. Awaruite selectively floats in weakly acidic conditions with xanthate as collector. However high reagent dosages are required in such conditions since xanthate decomposes and ultramafic rocks are acid consumers. In this work, a novel reagent scheme including ammonium sulfate and sodium thiosulfate is proposed to float awaruite in neutral conditions from ultramafic rocks. Electrochemical studies were carried out on awaruite samples to demonstrate the effect of low concentrations of these reagents on the awaruite surface. The awaruite passivation layer formed in alkaline conditions (natural slurry pH) can, at least, be partially dissolved in the presence of low concentrations of ammonium sulfate and thiosulfate in neutral conditions. After the passivation layer is partially removed, the xanthate collector reacts with the awaruite surface and induces hydrophobicity, thus enabling the awaruite flotation. Microflotation and bench scale flotation tests demonstrate the applicability of the reagent scheme herein proposed. This reagent scheme allows the flotation of awaruite in conditions where xanthate is stable and reduces the acid addition required to adjust the pH.
An original methodology based on the use of experimental values of the conditional equilibrium constants in metallurgical calculations was employed to perform a theoretical modeling of the exchange interactions in melts formed during joint matte smelting of oxidized saprolite nickel ore and a product (cinder) of partial oxidizing roasting of pyrrhotite concentrate. It is shown that heating of the ore-cinder mixture (mass ratio ≈ 1.0) to 1,300°C will ensure the separation of the slag and matte phases with the optimal process parameters. The proposed smelting conditions were tested experimentally, the material composition of the products was studied by X-ray fluorescence and X-ray powder diffraction analyses, and the possibility of obtaining results close to those predicted theoretically was confirmed. By using a flux-free smelting (at 1,400°C) of the mixture, it became possible to convert at least 76.1% nickel, 79.9% cobalt, and 62.8% copper to matte, containing (wt.%): Ni — 8.4, Co — 0.39, Cu — 0.5, Fe — 56.8, S — 25.6, and O — 7.2. 75.3% of the matte phase consists of iron monosulfides, including nickeliferous pyrrhotites (Fe17.574Ni0.24S20 and Fe2.747Ni0.253S3). Cobalt is present as jaipurite (CoS), and copper is dissolved in pyrite (Cu0.25Fe0.75S2) and in metallic iron (Cu0.003Fe0.997). Low contents of non-ferrous metals in slag (0.24 wt.% Ni, 0.08 wt.% Co, and 0.04 wt.% Cu) are associated with the presence of significant amounts of metasilicates and free SiO2 in the slag composition. A sufficient matte separation factor (5.5 for nickel, 5.7 for cobalt, and 4.5 for copper) and reduced desulfurization (≈ 0%) confirm the selected optimal conditions of joint ore-cinder smelting. The applied methodology of theoretical modeling and the obtained results can be used in the development of technologies for processing mineral and technogenic raw materials with low copper and nickel contents.
In this work, we have developed lead-free multi-layered epoxy polymer composites to effectively shield personnel and equipment against high energy γ-rays. Multi-layered shield, consisting of several layers of different materials, not only contributes to weight and cost reduction but also offers solution to inconsistent shielding performance. Compared to single layer of one type of shielding material, the probability of radiation absorption and scattering is higher in multi-layered configuration, thus enhancing shielding efficiency. However, there is a need to investigate the effect of stacking sequence and properties (dispersion of fillers, density of composites, etc.) of multi-layered materials on shielding performance. In view of this, several combinations of epoxy multi-layered composites containing micro and nano particles of both bismuth (III) oxide and tantalum (V) oxide were prepared to study the attenuation of γ-rays from 137Cs (662 keV) radioactive source. Attenuation experiments showed that the layered epoxy composites loaded with 30 wt% Bi2O3 nanoparticles alone showed around 30% γ-ray attenuation. 19-mm-thick multi-layered shield composed of two layers of n–Ta2O5/epoxy at the outer side, and two layers of n-Bi2O3/epoxy layer at the inner side were found to be as effective with almost same shielding efficiency. At around similar thickness, the epoxy composite containing n-Bi2O3/m-Bi2O3/n-Ta2O5/m-Ta2O5 layer-by-layer showed 28% attenuation, demonstrating the synergistic effect of combining micro and nano sized particles. Enhancement in attenuation on use of multi-layered structures could be attributed to the fact that epoxy composites containing different fillers of varying size will probably attenuate radiations more efficiently than those with one type of filler of a particular size. This work demonstrates that the multi-layered high-Z metal oxide-polymer composites may be as reliable as conventional lead-based materials in attenuating γ-rays.
Significant reserves of oxidized nickel ores are concentrated in the Ural region, in the deposits of various sizes that are mined by open-pit method. Ore is rather loose, which makes the cost of production relatively low. At the same time, the technologies employed at Ural nickel plants fail to meet the energy conservation requirements, and they are environmentally unfriendly and unprofitable. The paper proposes a two-stage hydrometallurgical technology for processing oxidized nickel ores from the Serovsky deposit. The composition of investigated ore is, wt.%: 1.01 Ni, 0.031 Co, 15.32 Fe total , 8.51 Al 2 O 3 , 21.76 MgO, 43.97 SiO 2 . The phase composition of the sample was determined by powder diffraction on the XRD-7000 X-ray diffractometer (Shimadzu, Japan). Serpentine Mg 6 [Ni, Si 4 O 10 ](OH) 8 and nimite (Ni, Mg, Al) 6 (Si, Al) 4 О 10 (OH) 8 were identified as the main nickel-containing minerals. Nickel enters the crystal lattice of silicates and replaces magnesium and iron isomorphically, which significantly complicates the disintegration of such minerals by the hydrometallurgical method. The paper provides the results of laboratory studies into atmospheric ore leaching with hydrochloric acid at the first stage and autoclave leaching of the obtained slurry at the second stage depending on temperature, leaching time and acid consumption. The total (in two stages) extraction into the solution was, wt.%: 82 Ni, 73.6 Co, 22 Fe, 22 Mg, 50.4 Al. Hydrochloric acid is almost completely consumed under these conditions with residual acid concentration of about 3 g/dm ³ . The autoclave slurry has good filterability. Cake composition after autoclave leaching is as follows, wt.%: 0.35 Ni, 0.01 Co, 12 Fe total , 10.63 Mg, 1.2 Al, 55 SiO 2 .
Laboratory studies have been undertaken to determine the mechanisms and kinetics of reactions occurring during the reduction roasting of saprolite ores with 1 wt% elemental sulphur addition. The reduction was undertaken using a 15%H2/85%N2 gas mixture at temperatures between 400 and 800°C; nickel was recovered by subsequent leaching in an ammoniacial aqueous solution. The effect of sulphur on dehydroxylation, reduction and sintering was investigated. Improvements in nickel recoveries were obtained when 1 wt% S was added to the nickel-bearing serpentine ore prior to the reduction roasting. Characterisation of the reduced and leached ore samples indicated that this improved Ni recovery with S addition is due to the formation of a leachable nickel sulphide phase, and the suppression of sintering and recrystallisation of the olivine phase formed at high reduction temperatures.
Studies have been undertaken to investigate the thermodynamic aspects of the reduction roasting of saprolite ores in the Caron Process. Reduction experiments have been conducted in controlled oxygen partial pressure conditions at selected temperatures. Detailed microstructure characterisation and thermodynamic analysis of reduced ore samples, focusing on the phase transformations, nickel recoveries and Ni-Fe alloy compositions produced, were carried out. Comparison has been made between the experimental results and FactSage thermodynamic predictions for these conditions. The differences between between the experimental and predicted results are discussed. It has been shown that the system below 700°C is approximated thermodynamically by considering the nickel–iron alloy product to be in chemical equilibrium with a metastable amorphous oxide phase.
Fundamental studies have been undertaken to determine the microstructural and phase transformations occurring during the reduction roasting of saprolite ores. Laboratory studies have been undertaken to simulate the conditions occurring during the reduction roast step of the Caron Process. Selected serpentine samples have been treated at temperatures between 500°C and 800°C in H2/N2 gas mixtures, and leaching tests on the reduced samples have been undertaken. Phase and microstructural changes have been characterised using X-ray Powder Diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) techniques.
A series of complex physical, microstructure and phase changes has been shown to occur during reduction roasting involving: (i) the dehydration of serpentine, (ii) the formation of a high-silica amorphous phase, (iii) the formation of Ni-Fe nanoparticles, and (iv) the nucleation, growth and recrystallisation of the forsterite (olivine) phase. The principal mechanism of removal of nickel from the reduced ore has been shown to occur through the selective leaching of the Ni-Fe alloy nano-particles from the surfaces in the product oxide.
Laboratory studies have been undertaken to investigate the mechanisms and kinetics of reactions occurring during the reduction roasting of saprolite ores. Reduction was undertaken using a H2/N2 gas mixture at temperatures between 400 and 800°C. The focus of the study was to determine the effect of dehydration, reduction, sintering and olivine recrystallisation reactions on nickel recovery. The effects of thermal history, temperature and time on the rates and extents of these processes have been investigated. The results provide valuable insights into the relative contributions of the elementary processes taking place during the reduction roast process, and help to explain some of the behaviour observed in industrial practice.
A new process is developed for metallurgical beneficiation of iron laterite nickel-containing (limonite) ores with the formation of a metallic nickel–cobalt concentrate. This process includes reducing roasting of the ores with sulfur-containing additions in the temperature range 1100–1200°C, the fragmentation of the roasting product, and the magnetic separation of metallic and slag phases. The coarsening of metallic particles in roasting is shown to occur with the participation of a low-melting-point phase (iron oxysulfide Fe(O,S)). In this case, nickel and cobalt concentrate in a metallic phase in the form of an alloy with iron (ferronickel). At the optimum charge composition and reducing roasting parameters, ferronickel particles coalesce and grow to 40–100 μm, which creates favorable conditions for the subsequent beneficiation of the roasting product (cinder) by magnetic separation. After wet magnetic separation of a fragmented cinder, the extraction of nickel and cobalt into a magnetic fraction is 92 and 84%, respectively. When a poor limonite ore (1.03% Ni, 0.05% Co) is processed according to the developed technology, the synthesized metallic concentrate contains up to 8.3% Ni and 0.37% Co.
The studies on the development of a new process for nickel and cobalt recovery from ferriferous laterite ores via a reducing roasting–sulfuric acid leaching are carried out. The conditions for the reducing roasting of the ores in the temperature range from 400 to 950°C and for the sulfuric acid leaching of the cinder (after cooling without air and passivation in water) at pH 1.4–3.0 and the weight ratio of the solid to liquid phases 1 : (3–4) in the temperature range from 25 to 95°C for 0.5–4 h are studied. General regularities of the reducing roasting of the ores with the selective metallization of nickel and cobalt (where the formation of wustite (FeO) is excluded; i.e, Fe2O3 is reduced to Fe3O4) are revealed. The conditions for the leaching of the cinder by sulfuric acid with nickel and cobalt recovery into a solution are established. The optimum parameters of these processes that make it possible to achieve high parameters for the recovery of nickel (87–99%) and cobalt (80–91%) into a solution at the sulfuric acid consumption within 90–140 kg/t ore are determined.
Presently work theoretical-experimental aspects of the leaching process are exposed ammonia-carbonate, new procedures are described that increase the nickel and cobalt recovery, characterized by the treatment attended with ultrasonic, for the aditivation process with chemical products of national production, substitution of CO2 in the turbos for the air, to a ≥ 60 g/L concentration, without excessive expenses in equipment for their implementation. A negative shade of the influence is given that exercises the iron in the process hydrometallurgical, its correct and opportune separation of the slurry ammoniacal for the mechanism of carbonatation in the first instants of the reactions, with this to be worked it perfects this technology, since leaves to this process without chemical-physical interferences, making to the same one appropriate for the prosecution of the laterities ores after a process of reductor calcination and during the leaching process and washing.
The ore used in this work came from the Goro deposits of New Caledonia, and analyzed 2. 50% nickel, 33. 5% iron and 7. 0% magnesium. Rapid and high recovery of metallic nickel may be obtained using stoichiometric copper sulfate addition for dissolution of the iron-nickel alloy, provided the ore is ground to about minus 325 mesh and a leach temperature of about 90 degree C is used. About 95% of the copper precipitated in the leach step may be recovered by flotation at pH 9. 0 using 0. 10 lb potassium amyl xanthate, 0. 20 lb Dextrine, and 0. 15 lb sodium cyanide per ton of solids. The copper sulfate leachant may be regenerated by oxidation of the concentrate and dissolution of copper oxide in a slight excess of sulfuric acid.
Nickeliferous laterites were characterized by particle size analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), Fourier transform infrared (FTIR) spectroscopy and thermal analysis. Results showed that the laterites consist mainly of nickel-substituted lizardite with cobble-like morphology and traces amounts of magnetite and phlogopite. As fluoride ions can react with silicon in the lizardite crystal structure and form metal-fluoride complexes, as well as increase the equilibrium constant of the lizardite dissolution in acid solution dramatically, the addition of minor fluoride salts (0.2wt.% NaF) gave a markedly enhanced metal extraction rate (Ni 81.7% and Co 52.3%) under the experimental conditions of particle size d(50)= 25 mu m, 10% (v/v) H(2)SO(4), reaction time 2 h, reaction temperature 90 degrees C, liquid-to-solid ratio 3 mL g(-1) and stirring at 500 rpm compared with H(2)SO(4) alone (Ni 69.6% and Co 30.8%).
The dissolution kinetics of cobalt in iodine/ iodide solutions were investigated using a rotating-disc technique. Variables studied included temperature, rotating speed, concentration of lixiviants and the pH of the solution. The overall dissolution reaction appeared to be limited by the mass transfer of tri-iodide through the diffusion boundary layer with an Arrhenius activation energy of <16.2 kJ/mol (4 kcal/mol) over the temperature range of 2 to 42 °C. The pH of the solution had little effect, as long as the pH of the solution was <8. However, when the pH of the solution became >8, the dissolution rate decreased dramatically, due to passivation. The rate of dissolution was in good agreement with the dissolution model developed by the authors earlier.
Pilot plant operations have confirmed the validity of a process for the recovery of nickel and cobalt from the ores of laterite deposits, the world’s largest known reserves of these metals.
Precipitation of manganese from the S02-roast leach, ammoniacal ammonium sulphate solution bearing both, high and low manganese content was carried out in a stainless steel reactor fitted with a turbo grid. Air/0 2 was used to precipitate Mn as MnO2. There was adsorption loss of cobalt from solution. There was precipitation of 57.2 - 99.96% Mn with, loss of 3% Cu, 3.5% Ni and 2.9% Co. The precipitation of Mn and adsorption loss of cobalt from the solution was first order. The rate constants for manganese and cobalt precipitations were evaluated. The data were fitted to Freundlich and Langmuir adsorption isotherms. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).
This paper covers the history and implementation of key technologies in nickel and cobalt hydrometallurgy. Breakthrough leaching, purification, separation, concentration and recovery unit operations are considered. The author has humbly chosen illustrative technologies which have innovative drivers. The key driver has been the enhanced separations offered by hydrometallurgy albeit global politics has also played a significant role in the case of Cuban developments. This includes industrial examples such as the Sherritt Gordon Process, the Falconbridge Process, the Roast Reduction Ammoniacal Leach Process, and the High Pressure Acid Leaching Process along with a treatise on the advent of Solvent Extraction separations in these endeavors. To that end, the proposed and imminent Voisey's Bay sulfide concentrate industrial process, relying heavily on modern hydrometallurgical innovations such as continuous pressure oxidation and multiple solvent extraction separations is briefly elucidated.
Phytomining technology employs hyperaccumulator plants to take up metal in harvestable plant biomass. Harvesting, drying and incineration of the biomass generates a high-grade bio-ore. We propose that “agromining” (a variant of phytomining) could provide local communities with an alternative type of agriculture on degraded lands; farming not for food crops, but for metals such as nickel (Ni). However, two decades after its inception and numerous successful experiments, commercial phytomining has not yet become a reality. To build the case for the minerals industry, a large-scale demonstration is needed to identify operational risks and provide “real-life” evidence for profitability.
Phytomining technology employs hyperaccumulator plants to take up metal in harvestable plant biomass. Harvesting, drying and incineration of the biomass generates a high-grade bio-ore. We propose that 'agromining' (a variant of phytomining) could provide local communities with an alternative type of agriculture on degraded lands, farming not for food crops, but for metals such as nickel (Ni). However, two decades after its inception and numerous successful experiments, commercial phytomining has not yet become a reality. To build the case for the minerals industry, a large-scale demonstration is needed to identify operational risks and provide 'real-life' evidence for profitability.
Small-scale laboratory experiments were performed on the roasting and the smelting of manganese nodules at various temperatures using either coal or No. 6 fuel oil as the reductant. Using oil as the reductant yielded significantly higher extractions of copper, nickel, and cobalt in subsequent leaching of the roasted calcines or the metallic alloy produced by smelting. Better overall extractions of the above metals and better selectivity of reduction are obtained with oil because of the improved contact with the finely disseminated metal values of the porous nodules. Such improved contact assures a closer approach to thermodynamic equilibrium. The by-product residues from leaching the roasted calcines, or slags from smelting, are excellent materials for ferromanganese production since they are substantially free from all heavy metal contaminants.
A low grade iron ore containing 51.6% Fe, 17.6% SiO2, 4.3% Al2O3, and 3.8% LOI was subjected to reduction roasting followed by low intensity magnetic separation studies. The phase transformation of hematite into magnetite and fayalite due to reduction roasting was investigated using reflected microscope and X-ray diffraction (XRD) techniques. The effects of reduction variables such as reduction time (40−175 min), temperature (750−1000°C), and reductant dosage (3−11%) using activated charcoal were studied. The process was optimized by using central composite rotatable design (CCRD) and response surface methodology. Iron grade from 59−66% with recovery of 9.5−87% was achieved using CCRD experiments. Model equations were developed both for Fe grade and recovery and then optimized within the bounds of experimental conditions. The program predicted 63.3% Fe with 79% recovery with the following optimum conditions: temperature: 950°C, time: 53.04 min, and reductant: 3%.
The Hague, Holland 54.-15-29-1939 (No. 13) 58.-37-40-1946 (No. 22) 59.-21-22-1947 (No. 24) 59
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