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Zinc recovery from sphalerite concentrate by direct oxidative leaching with ammonium, sodium and potassium persulphates
Abstract
The recovery of zinc from sphalerite concentrate by oxidative leaching with ammonium, sodium and potassium persulphates in sulphuric acid media is reported in this investigation. Effects of particle size, reaction temperature, acid concentration, pulp density (PD) and oxidant concentration on zinc dissolution rate were determined. The results showed that leaching of 95% zinc was achieved from the concentrate of particle size −150 μm at a temperature of 333 K for 5 h in the presence of 20% (w/v) ammonium persulphate (APS) with 5% (v/v) sulphuric acid concentration. The best fit of the kinetic data to a diffusion-controlled model indicated that diffusion through the product layer was the rate-controlling step during the dissolution. The activation energy was determined to be 41±2 kJ/mol in the temperature range 308–333 K which was also an indication of the diffusion-controlled process. The mechanism of the leaching was further established by characterising the original concentrate and the leach residue by XRD phase identification, optical and SEM-EDS studies.
... These methods allow high-quality metal production with much lower environmental impact than that of pyrometallurgical methods. However, hydrometallurgical methods cannot be used for lead production because lead salts are only weakly soluble [12][13][14][15]. ...
... 2ZnO + C → Zn g + CO 2 (11) ZnO + CO → Zn g + CO 2 (12) 2PbO + C → Pb + CO 2 (13) PbO + CO → Pb + CO 2 (14) CaCO 3 → CaO + CO 2 (15) 2Zn g + O 2 → 2ZnO (16) PbO + CO → Pb + CO2 (14) CaCO3 → CaO + CO2 (15) 2Zng + O2 → 2ZnO (16) In this process, the furnace charge consists of refining slags, coal (reducing agent), and limestone CaCO 3 (flux). During the processing of the slags, sample weight loss was observed, which primarily occurred due to zinc evaporation caused by the reduction process. ...
... 2ZnO + C → Zn g + CO 2 (11) ZnO + CO → Zn g + CO 2 (12) 2PbO + C → Pb + CO 2 (13) PbO + CO → Pb + CO 2 (14) CaCO 3 → CaO + CO 2 (15) 2Zn g + O 2 → 2ZnO (16) PbO + CO → Pb + CO2 (14) CaCO3 → CaO + CO2 (15) 2Zng + O2 → 2ZnO (16) In this process, the furnace charge consists of refining slags, coal (reducing agent), and limestone CaCO 3 (flux). During the processing of the slags, sample weight loss was observed, which primarily occurred due to zinc evaporation caused by the reduction process. ...
This article presents the mineralogical and chemical characteristics of zinc and lead smelting slags, with particular reference to the slags formed during the simultaneous production of Zn and Pb by the Imperial Smelting Process. These slags, because of the presence of many metals in their composition, mainly in the form of crystalline phases, are a valuable source for their extraction. Slags from Zn-Pb metallurgy are processed on an industrial scale using pyrometallurgical and hydrometallurgical methods, alongside which a number of experiments conducted to recover metals as efficiently as possible, including bioleaching experiments.
... Según Babu, Sahu, & Pandey (2012), investigaron sobre la recuperación de zinc a partir de concentrado de esfalerita por lixiviación oxidante con persulfato de amonio, sodio y potasio en medios de ácido sulfúrico. Se determinaron los efectos del tamaño de partícula, la temperatura de reacción, la concentración de ácido, la densidad de la pulpa y la concentración de oxidante en la velocidad de disolución del zinc. ...
... > F0.05, 2,18= 3.55, donde la temperatura también influye significativamente al porcentaje de recuperación de zinc. Ello lo corrobora Babu, Sahu, & Pandey (2012), los cuales investigaron sobre la recuperación de zinc a partir de concentrado de esfalerita por lixiviación oxidante con persulfato de amonio, sodio y potasio en medios de ácido sulfúrico. Se determinaron los efectos del tamaño de partícula, la temperatura de reacción, la concentración de ácido, la densidad de la pulpa y la concentración de oxidante en la velocidad de disolución del zinc. ...
... Por lo tanto, para cada sistema se establecen equilibrios determinados y la velocidad de recuperación dependerá fundamentalmente de la naturaleza de estas relaciones. En todos los procesos de lixiviación es necesario conocer el tiempo que el sistema tarda en alcanzar el equilibrio, es decir, el tiempo a partir del cual, por más que se mantenga el contacto entre el persulfato de amonio y el metal a recuperar (Babu, Sahu, & Pandey, 2012) Asimismo, el persulfato de amonio es un fuerte oxidante en solución ácida para sulfuros metálicos y no existen suficientes estudios de su empleo para la lixiviación de concentrados de sulfuro de zinc o esfalerita. Considerando la alta eficiencia de extracción de este oxidante y que además se puede regenerar para volverlo a utilizar, resulta muy importante y se justifica su estudio para determinar las condiciones óptimas del proceso de lixiviación oxidante directa de los concentrados de zinc, en presencia de ácido sulfúrico (Yong & Wadsworth, 2006). ...
Se estudió la influencia del tiempo de residencia y temperatura en la recuperación de zinc porlixiviación oxidante con persulfato de amonio. El estudio experimental se realizó utilizandoun concentrado disuelto en solución con contenidos de zinc sometida a diferentes tiempos deresidencia a 2, 4, 6 horas, y diferentes temperaturas a 20, 40 y 60 °C, con una concentracióninicial de zinc de 53.80 %. El resultado del estudio concluyó que el inicio de la recuperación dezinc a 2 horas y 20° C fue de 44.64 %; es así que se llegó a obtener una mayor recuperación de88.73 % a un parámetro de 6 horas y 40° C. Los resultados son confirmados mediante análisis devarianza para un nivel de confianza de 95%. De esto se concluye que la recuperación de zinc porla influencia del tiempo de residencia de F0 = 803.27 es mayor al F0.05; 2; 18= 3.55, y la influencia dela temperatura es de F0 = 5388.01 es mayor al F0.05; 2; 18= 3.55; y con la interacción de influenciadel tiempo de residencia y temperatura de F0 = 94.90 mayor al F0.05; 4; 18= 2.93, obtenido de maneratabular. Esto confirma la aceptación de la hipótesis alterna, por lo tanto, la influencia del tiempode residencia y temperatura de manera individual como en conjunto sí afectan significativamenteen la recuperación de zinc.Palabras clave: Lixiviación oxidante, esfalerita, persulfato de amonio, zinc
... Therefore, there has been a considerable interest in using an alternative oxidant to make atmospheric leaching process faster and operable at even milder conditions. The use of persulfates (Babu, Sahu and Pandey, 2002;Sahu, Sahu and Pandey, 2006), nitric acid and tetrachloroethylene (Peng, Xie and Lu, 2005), and hydrogen peroxide (Aydogan, 2006;Pecina et al., 2008) as alternative oxidants in sulfuric acid medium have been studied for this purpose. ...
... This is also in agreement with the work of Havlik and Skrobian (1990), who studied the leaching of chalcopyrite concentrate with sulfuric acid and ozone. This fact therefore asserts the dominant role of ozone on zinc dissolution from sphalerite concentrate, considering that increased temperature should generally increase the leaching rate of sphalerite with sulfuric acid in the studied temperature range (Dutrizac, 2006;Souza et al., 2007;Aydogan, 2006;Peng, Xie abd Lu, 2005;Sahu, Sahu and Pandey, 2006;Babu, Sahu and Pandey, 2002;Pecina et al., 2008). ...
... The residue, which was mostly comprised of elemental sulfur, was readily floated (Fig. 11b), suggesting that the generated sulfur was forming independent particles that were released from the mineral surface rather than layering on the surface of the reacted particle. This was also indicated by the fact that there was no apparent hindrance in zinc dissolution throughout the leaching process, which is usually observed in an atmospheric leaching of sphalerite concentrate with other oxidants such as in a ferric sulfate system (Lochmann and Pedĺik, 1995;Souza et al., 2007) or in a system with persulfates (Babu, Sahu and Pandey, 2002;Sahu, Sahu and Pandey, 2006), nitric acid (Peng, Xie and Lu, 2005), hydrogen peroxide (Aydogan, 2006;Pecina et al., 2008). Moreover, the kinetic analysis suggested that the overall reaction process was controlled by a surface reaction throughout the leaching process, as the best result from the data-fit of the used kinetic models (Fig. 12) was obtained by the following equation: ...
The use of ozone as an oxidant for the direct leaching of zinc sulfide (sphalerite) concentrate in sulfuric acid medium under atmospheric pressure was explored. The influence of acid concentration, feed gas injection rate, particle size distribution, stirring speed, temperature and slurry density on zinc extraction efficiency was examined. The experimental results showed that the leaching efficiency depends on all of these operating parameters except for stirring speed. It was found that essentially complete dissolution of zinc from the concentrate with the present method can be achieved in only about seven hours under the conditions of sulfuric acid concentration of 2 mol/L, particle size smaller than 74 ìm, slurry density of 50 g/L, stirring speed of 420 rpm and feed gas injection rate of 1 L/min at ambient temperature. The experimental results suggest that the dissolution reactions produce independent elemental sulfur that is readily floated and can be easily separated rather than forming a layer on the surface of the reacted particle, as usually observed in a system with ferric-sulfate as oxidizing agent. It was therefore determined that the dissolved ozone play a key role in improving the rate of zinc dissolution from the concentrate. Analysis of the leaching kinetics indicate that the leaching rate follows the shrinking particle model, and the overall dissolution rate of zinc is controlled by a surface reaction.
... A schematic representation of the system is shown in Fig. 1. Babu et al. [47] have reported the decomposition behavior of ammonium persulfate in aqueous solutions under atmospheric conditions. The decomposition behavior of ammonium persulfate in a closed vessel is also important for the present study. ...
... Active oxygen released from the rapid decomposition of APS under the atmospheric conditions may escape from the leaching medium without achieving further oxidation. It has also been reported that the decomposition rate of APS increased with increasing temperature above 333 K according to Eq. (4) [47]. In these experiments, the reaction mixtures were stirred under reflux. ...
... Babu et al. [47] showed that leaching of zinc from sphalerite concentrates was feasible using persulfate salts. The authors also reported that the recovery of zinc depended on the leaching temperature. ...
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.
... Direct leaching processes can be divided into two categories, zinc pressure leaching (ZPL) processes and atmospheric direct leaching (ADL) processes. Both processes have many industrial applications [15][16][17][18][19]. Sherritt Gordon Ltd. (Now Sheritt International) pioneered PL in the 1970s with its Sherritt Pressure Leach Process, which allows for quick concentrate dissolution [20], and the standard residence time of sphalerite pressure leaching process is 90 minutes, the leaching temperature is mostly higher than 120 ℃, the pressure up to 1600 kpa, autoclave equipment is required [21,22]. The drawback of ZPL is large capital and maintenance requirements as well as high operational safety requirements. ...
... The results have made clear that there is no obvious impediment to the zinc leaching process under open-air conditions when the zinc sulfide concentrate is solidified at high temperature and concentrated sulfuric acid. Other oxidants that cause this include the ferric system [9,29], persulfates [22], nitric acid [23] or hydrogen peroxide [14,30]. ...
Because the traditional roasting-leaching-electrowinning zinc hydrometallurgy process has a small sulfuric acid sales radius and a high inventory pressure, the process of direct leaching zinc concentrate is gaining popularity. but the pressurized leaching process is a high-pressure condition, which requires strict equipment material and high safety requirements. Furthermore, the atmospheric leaching efficiency is low and generally introduces impurities and chloride ions, which increase the cost of subsequent decontamination. Therefore, a new environmentally friendly hydrometallurgy extraction method of zinc was proposed: an atmospheric pressure medium temperature sulfuric acid curing-leaching process. In an open-air condition, zinc sulfide concentrate was cured with sulfuric acid at different acid-to-ore ratios and heated to 220?C~260?C for a different time, then leaching the cured product. The effects of temperature, curing time, acid-to-ore ratio and sulfuric acid concentration on the leaching ratio of zinc (hZn) were studied. The results demonstrated that hZncould reach as high as 98.23% under the optimized conditions of temperature 240?C, curing time 2.5 hours, acid-to-ore ratio 1.4:1 and sulfuric acid concentration 60 wt.%. The leaching residue ratio is 6%, with silicate accounting for the majority of it. The kinetic results support the shrinking core model, which is controlled by an interface chemical reaction with an apparent activation energy of 43.158 kJ/mol.
... To date, sulfide ore is the most commonly used raw material for zinc metallurgy because of its high grade of zinc and easy flotation. However, sulfide ores are gradually being depleted [3][4][5][6]. Zinc oxide ores are the most abundant zinc resource, representing more than 65% of zinc resource reserves. Therefore, the effective exploitation and utilization of zinc oxide ores is important for the zinc industry [5][6][7][8]. ...
... Zinc oxide ores are the most abundant zinc resource, representing more than 65% of zinc resource reserves. Therefore, the effective exploitation and utilization of zinc oxide ores is important for the zinc industry [5][6][7][8]. ...
An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using (NH4)2SO4. The optimized reaction conditions are defined as an (NH4)2SO4/zinc molar ratio of 1.4:1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of (NH4)2SO4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric–differential thermal analysis was used for (NH4)2SO4 and zinc mixed in a molar ratio of 1.4:1 at the heating rates of 5, 10, 15, and 20 K·min−1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle–Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.
... Zinc is an important metal required for various applications in metallurgical, chemical and textile industries, and is mainly recovered from zinc sulfide concentrates through the conventional hydrometallurgical process, including oxidative roasting, acid leaching, purification and electrowinning steps, in the world [1][2][3]. In the roasting step, zinc ferrite (ZnFe 2 O 4 ) is generated as an inevitable byproduct of the oxidative roasting [4,5]. ...
... In addition, the FeO can be also converted into Fe as the P CO /P CO+CO2 is more than 50%, and the ZnO can be converted into Zn when the P CO /P CO+CO2 is beyond 82% and the temperature exceeds 900°C. In a word, with the increase in P CO /P CO+CO2 the decomposition of ZnFe 2 It is common that there are some differences between practical process and thermodynamic analysis because of dynamic influence. Therefore, it is necessary to study the decomposition behavior of zinc ferrite by reduction roasting experiment, in spite of positive results being shown in terms of thermodynamics. ...
... Direct pressure leaching enables fast concentrate dissolution; standard residence time in the sphalerite pressure leaching process is 90 min, and operating pressures are up to 1600 kPa. Problems associated with pressure leaching are mainly found in the operation and maintenance of autoclaves (Takala, 1999;Babu et al., 2002). Atmospheric leaching is considered an option to address problems encountered in industrial pressure leaching processes. ...
... The direct atmospheric leaching process is carried out with slow kinetics requiring around 24 h for leaching, and larger reactors are therefore needed compared to pressure leaching plants ( Takala, 1999). Studies of direct leaching have been performed by many authors (Rath et al., 1981;Verbaan and Crundwell, 1986;Crundwell, 1987;Corriou et al., 1988;Palencia Perez and Dutrizac, 1991;Babu et al., 2002;Dutrizac, 2006;Souza et al., 2007;Xie et al., 2007;Xu et al., 2013), and a novel reaction system has been presented ( Haakana et al., 2007). New technologies Hydrometallurgy 153 (2015) ...
In this study, direct leaching of zinc sulfide concentrate was investigated in a solution that resembles the composition of solutions used in industrial leaching processes. The effect of different factors (temperature, Fe2 +–Fe3 +-concentration, H2SO4-concentration, SO4-concentration, pressure, size of the concentrate particles) on the rate of the zinc sulfide concentrate leaching was studied experimentally. H2SO4-concentration had no influence on the leaching kinetics. The obtained experimental data were used to model the reaction kinetics with mechanistic models as well with a more empirical model, and the reliability and the accuracy of the model parameters were studied with Markov Chain Monte Carlo (MCMC) methods. The model that best describes the leaching system (R2 = 97%) takes into account the reactions between the zinc sulfide concentrate and oxidizing agents at the reacting surface of the concentrate particles, the decrease in the active surface area of the concentrate particles as the leaching proceeds, the particle size distribution of the concentrate particles, the composition of the solution, and the oxidation rate of Fe2 + to Fe3 +. The experimental results together with the modeling results clearly demonstrate that it is important to have experimental data for the kinetics of the leaching at the conditions of the reactor.
... Babu et al. [20] investigated oxidative leaching of sphalerite with ammonium persulphate in sulphuric acid media. They achieved of 95% zinc extraction at a temperature of 60 o C for 5 h in the presence of 20% (w/v) ammonium persulphate. ...
... Various investigators were found the similar values of activation energy for the sphalerite leaching. Babu et al. [20] leached sphalerite with ammonium persulphate in sulphuric acid media. The activation energy was 41±2 kJ/mol in the temperature range 35-60 o C, and the diffusion through the product layer was the rate-controlling step. ...
Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90 o C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90 o C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism.
... As a result, researchers have explored alternative methods, such as leaching in direct pressure leaching and atmospheric leaching for extracting zinc metal [3][4][5][6]. Pressure leaching allows for fast dissolution with a standard residence time of 90 min and operating pressures up to 1600 kPa [7,8]. On the other hand, atmospheric leaching is less expensive than pressure leaching due to lower maintenance costs. ...
The utilization of deep eutectic solvents (DESs) as a novel class of solvents in hydrometallurgical processes for metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20-1440 min, 40-100 °C, and 0-24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to substantially improve efficiency. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The zinc sulfide leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data was in the range of 0.87 to 0.97 for temperature of 40 to 100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.
... Bu nedenle sfaleritin hidrometalurjik yöntemlerle kazanımı hususunda çok çeşitli çalışmalar yapılmıştır. Bu çalışmaların bir kısmında farklı liç yöntemleri denenmiş [15][16][17][18][19], bir kısmında da liç kinetiği çalışılmıştır [20][21]. Bazı çalışmalarda atıklardan çinko eldesi çalışılmış [22][23], bir çalışmada da alkali liçi denenmiştir [24]. ...
Bu çalışmada Balıkesir-Balya Pb-Zn cevherlerinden Zn’nin asit liçi yöntemi ile kazanımı araştırılmıştır. Sülfürik asit (H2SO4), hidroklorik asit (HCl) ve nitrik asit (HNO3) ile gerçekleştirilen kimyasal çözündürme deneylerinde; 75-106-150 µm tane boyutu, %5-10-15-20-25 katı oranı, 30-60-120-180-240 dak. liç süresi, 0,25-0,5-1-2-5 M asit dozajı ve 30-40-50-60-70 oC pülp sıcaklığı parametreleri denenmiştir. Zn için optimum sonuçlar 75 µm (H2SO4 ve HNO3) ve 106 µm (HCl) tane boyutu, %15 (H2SO4), %25 (HCl) ve %20 (HNO3) katı oranı, 120 dak. (H2SO4) ve 60 dak. (HCl ve HNO3) liç süresi, 0,5 M (H2SO4 ve HCl) ve 1M (HNO3) asit dozajı ve 50 oC (H2SO4 ve HNO3) ve 70 oC (HCl) pülp sıcaklığı şartlarında elde edilmiştir. Belirtilmiş olan bu optimum koşullarda gerçekleştirilen deneyler sonucunda sırasıyla %97,32, %96,38 ve %96,06 Zn çözünme verimleri elde edilmiştir. Ayrıca bu çalışmada her üç asit için de sıcaklığa bağlı kinetik analizler gerçekleştirilmiştir. Her asit için -106+75 µm tane boyutu, 1 M asit dozajı, %20 katı oranı, 0-30 dak. liç süresi, 50-90 oC pülp sıcaklığı, 250 dev./dak. karıştırma hızı koşullarında deneyler gerçekleştirilmiştir. H2SO4, HCl ve HNO3 deneyleri için liç kinetiği incelendiğinde farklı sıcaklıklarda elde edilmiş olan çözünme verimleri grafiklendirilerek elde edilen doğruların eğiminden görünür hız sabitleri ve korelasyon katsayıları hesaplanmıştır. Bu değerler incelendiği zaman Zn çözünmesinin her üç asit ortamında da Küçülen Çekirdek Modeli’nde difüzyon kontrollü modele uyduğu görülmüştür. Zn liçi çözünme verimlerinde farklı sıcaklıklar için elde edilen Arrhenius grafiği doğrusunun eğiminden aktivasyon enerjileri H2SO4 için 3,615 kJ/mol, HCl için 4,811 kJ/mol ve HNO3 için de 4,736 kJ/mol olarak hesaplanmıştır.
... Previous studies corroborated that the efficient recovery of zinc in a sulfuric acid medium was governed by diffusion of lixiviant through porous sulphur layer (Babu et al., 2002). APS was found to be better oxidant than sodium/potassium PS at 343 K for the leaching of zinc from sphalerite concentrate in sulphuric acid media. ...
Over the past years, persulfate (PS) is widely applied due to their high versatility and efficacy in decontamination and sterilization. While treatment of organic chemicals, remediation of soil and groundwater, sludge treatment, disinfection on pathogen microorganisms have been covered by most published reviews, there are no comprehensive and specific reviews on its application to address diverse sustainability challenges, including solid waste treatment, resources recovery and regeneration of ecomaterials. PS applications mainly rely on direct oxidation by PS itself or the reactive sulfate radical (SO4•−) or hydroxyl radical (•OH) from the activation of peroxodisulfate (PDS, S2O8²⁻) or peroxymonosulfate (PMS, HSO5⁻) in SO4•−-based advanced oxidation processes (SO4•−-AOPs). From a broader perspective of environmental cleanup and sustainability, this review summarizes the various applications of PS except pollutant decontamination and elaborates the possible reaction mechanisms. Additionally, the differences between PS treatment and conventional technologies are highlighted. Challenges, research needs and future prospect are thus discussed to promote the development of the applications of PS-based oxidation processes in niche environmental fields. In all, this review is a call to pay more attention to the possibilities of PS application in practical resource reutilization and environmental protection except widely reported pollutant degradation.
... Большое значение имеет получение из природного сфалерита химически чистого люминофорного ZnS, активированного Ag, Cu, который применяют для изготовления люминофоров, различных светосоставов и светящихся красок. Кроме того, природный сфалерит может быть использован в качестве фотокатализатора разложения красителей в воде[5].В работе исследованы цинковые концентраты, полученные из месторождений Хандиза. В Узбекистане на Алмалыкском ГМК ведется переработка полиметаллических руд месторождения Хандиза[4].Полиметаллические руды месторождения Хандиза комплексные, т.е. ...
Приведены данные литературных источников в области получения и
применения соединений цинка и, в частности, сульфата цинка. Дана характеристика
полиметаллическим рудам месторождения «Хандиза», их переработки и получения
цинкового концентрата. Отмечается необходимость глубокой, комплексной переработки
цинкового концентрата с выделением редких и благородных металлов.
... This step requires activation energy and can be limiting in ambient conditions (Liang et al., 2008). However, at 100°C for 14 days, the persulfate is exposed to conditions that enhance its oxidation kinetics; for example, persulfate was found to fully decompose in 2 h at 90°C and decompose more quickly at higher temperatures (Babu et al., 2002). The sulfate ions react with water to produce HSO 4 − and OH, the latter of which is a reactive oxidizing species (ROS) (Deng and Ezyske, 2011). ...
Natural gas extracted from tight shale formations, such as the Marcellus Shale, represents a significant and developing front in energy exploration. By fracturing these formations using pressurized fracturing fluid, previously unobtainable hydrocarbon reserves may be tapped. While pursuing this resource, hydraulic fracturing operations leave chemically complex fluids in the shale formation for at least two weeks. This provides a substantial opportunity for the hydraulic fracturing fluid (HFF) to react with the shale formation at reservoir temperature and pressure. In this study, we investigated the effects of the carbonates on shale-HFF reactions with a focus on the Marcellus Shale. We performed autoclave experiments at high temperature and pressure reservoir conditions using a carbonate-rich and a decarbonated or carbonate-free version of the same shale sample. We observed that carbonate minerals buffer the pH of the solution, which in turn prevents clay dissolution. Carbonate and bicarbonate ions also scavenge reactive oxidizing species (ROS), which prevents oxidation of shale organic matter and volatile organic compounds (VOCs). Carbonate-free samples also show higher pyrite dissolution compared to the carbonate-rich sample due to chelation reactions. This study demonstrates how carbonate minerals (keeping all other variables constant) affect shale-HFF reactions that can potentially impact porosity, microfracture integrity, and the release of heavy metals and volatile organic contaminants in the produced water.
... Consequently, two alternative processes were proposed in the 1970's and several leaching studies have been carried out through them. The first process involved direct leaching using oxidising agents such as acids [6,7], ferric salts [8], alkalis [9], hydrogen peroxide [10], persulphate salts [11], among others. The second process involved pressure leaching using oxygen under pressure with some oxidising agents in autoclaves [12]. ...
The effectiveness of a binary solution of acetic acid and sodium nitrate as a lixiviant for zinc recovery from sphalerite has been investigated in this study. Response surface methodology (RSM) was used to model the leaching process. RSM optimisation was carried out using a 5-level-5-factor central composite design to achieve a maximum zinc yield of 89.61% at a leaching temperature of 90o C, acid concentration of 6 M, stirring rate of 550 rpm, leaching time of 120 min., and sodium nitrate concentration of 0.6 M. A binary solution of acetic acid and sodium nitrate thus proves to be a good lixiviant for zinc recovery.
Keywords: sphalerite, Enyigba, zinc recovery, response surface methodology
... However, this later is characterized by slow dissolution kinetics. To overcome this shortcoming, researchers have used different oxidants such as ferric ions [12], ozone [22], hydrogen peroxide [23], ammonium, and sodium and potassium persulfate [24]. ...
The present work reports the direct leaching of zinc from a sphalerite concentrate in acid media. Lab-scale and pilot-scale experiments were conducted in atmospheric-pressure and low-pressure reactors, respectively. Leaching of zinc and precipitation of iron was achieved in the same stage using different reagents like Fe 3+ , O 2 , O 3 , and Fe 2+ (which is continuously oxidized in the leaching solution by H 2 O 2 and O 2). The highest percentage of zinc extraction (96%) was obtained in pilot-scale experiments using H 2 SO 4 , Fe 2+ , and O 2. Experimental results were compared with those of other researchers to provide a better understanding of the factors influencing the dissolution of zinc. In the first instance, it was determined from analysis of variance that leaching time and the use of an oxidant agent (O 2 or O 3) were the most influential factors during the direct leaching of zinc from the sphalerite concentrate. Kinetic models were also evaluated to determine the rate-limiting step of the sphalerite leaching; it was concluded that the type of the sulfur layer formed in the residue (porous or non-porous) depends on the type of the oxidant used in the leaching media, which determines the dissolution kinetics of zinc.
... Persulfate compounds are strong oxidizing agents that are reduced to sulfates in solution during the oxidation process. The oxidizing properties are thought to be a significant advantage for the leaching of sulfide materials [35,36]. The cathodic reaction of persulfate salts is represented as ...
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.
... Pyrometallurgy and high-pressure leaching are two typical methods used for the extraction of metals from concentrates of flotation separation [1][2][3]. These methods have several disadvantages such as high investment and operation costs, environmental pollution (chemical reagents in the waste waters of hydrometallurgical plants and SO 2 gas generation from pyrometallurgical plants), high energy consumption in the pyrometallurgy processes, high technology requirements for pyro/hydro-metallurgy process, and finally special expertise for system operators [4,5]. ...
Bioleaching is an environment-friendly and low-investment process for the extraction of metals from flotation concentrate. Surfactants such as collectors and frothers are widely used in the flotation process. These chemical reagents may have inhibitory effects on the activity of microorganisms through a bioleaching process; however, there is no report indicating influences of reagents on the activity of microorganisms in the mixed culture which is mostly used in the industry. In this investigation, influences of typical flotation frothers (methyl isobutyl carbinol and pine oil) in different concentrations (0.01, 0.10, and 1.00 g/L) were examined on activates of bacteria in the mesophilic mixed culture (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans). For comparison purposes, experiments were repeated by pure cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in the same conditions. Results indicated that increasing the dosage of frothers has a negative correlation with bacteria activities while the mixed culture showed a lower sensitivity to the toxicity of these frothers in comparison with examined pure cultures. Outcomes showed the toxicity of Pine oil is lower than methyl isobutyl carbinol (MIBC). These results can be used for designing flotation separation procedures and to produce cleaner products for bio extraction of metals.
... This process has several troubles, such as the restrictions to treat sphalerite concentrate with silica, calcium, copper and iron, the emissions of SO 2 and marketing of sulphuric acid (Deller, 2005). Several processes have been studied, in the last years, to extract Zn from differential concentrates, such as atmospheric pressure leaching (Salmi et al., 2010;Souza et al., 2007a;Babu et al., 2002), bioleaching (Haghshenas et al., 2012) or heap-Bioleaching (Lizama et al., 2003). ...
A novel process for the integral treatment of polymetallic sulphide ores is proposed. The process consists of a global flotation, two stages of ferric leaching, the first stage dissolves the sphalerite and the rest of secondary sulphides, and the second dissolves the chalcopyrite with a silver catalyst, and finally a brine leaching to recover lead and silver (added as catalyst). The proposed process offers several advantages comparing to traditional pyrometallurgical techniques. This study is focused on the sphalerite dissolution with ferric sulphate, as the first stage of the treatment of Cu-Zn-Pb concentrates. The ferric ion concentration, the temperature and the particle size have an important role in the sphalerite oxidation. However, the initial sulphuric acid, ferrous ion and sulphate ion concentrations have no influence in the process rate. The formation of an elemental non-porous layer of sulphur along the reaction hinders the ferric ion transport to the sphalerite surface. Two kinetics regimes are proposed, in the beginning the chemical reaction is the rate controlling step, and, at 30% Zn extraction, the rate controlling step changes to diffusion through a non-porous film of elemental sulphur. The activation energy obtained for the chemical reaction has a value of 51.3 kJ/mol, and the apparent activation energy in the diffusional stage is the 47.7 kJ/mol. The reaction order with respect ferric ion is 0.26 and the reaction rate is proportional to the zinc sulphide amount in the first stage. The behaviour of sphalerite, contained in a bulk concentrate, is similar to the pure sphalerite or the sphalerite contained in a differential concentrate.
... Under the atmospheric pressure, it has been determined that the copper extraction limited, and it could be improved by a further milling to obtain better extraction yields [42,43]. And also, some studies showed that using of persulfate compounds provided several benefits because of owning high potential [44,45]. ...
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.
... Two kinetic regimes were studied in leaching process. Equations (2) and (3) can be used to describe the leaching of zinc when only one step, chemical reaction [12,14,22,24] or diffusion through the reaction product [4,8], controls the entire process. However, some investigations [7,25] confirmed both equations. ...
The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined. All tests were carried out in the pilot plant. To allow the execution of hydrostatic pressure condition, the slurry with ferrous sulfate and sulfuric acid solution was filled into a vertical tube (9 m in height) and air was blown from the bottom of the reactor. The effects of initial acid concentration, temperature, particle size, initial zinc sulfate concentration, pulp density and the concentration of Fe on the leaching kinetics were investigated. Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinking core model (SCM). This process was controlled by a chemical reaction with the apparent activation energy of 49.7 kJ/mol. Furthermore, a semi-empirical equation is obtained, showing that the order of the iron, sulfuric acid and zinc sulfate concentrations and particle radius are 0.982, 0.189, −0.097 and −0.992, respectively. Analysis of the unreacted and reacted sulfide particles by SEM–EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lower than 60% Zn conversion and lixiviant in the face with sphalerite particles.
... Oxygen could be an oxidizing agent as well, but the concentration of oxygen is very low in the solution. The role of ferric ions is predominate in this oxidation (Babu, Sahu, & Pandey, 2002). The oxidation reaction for sphalerite in the presence of ferric in can be presented as follows (Lampinen, Laari, & Turunen, 2015): ...
In this work, the kinetics of ferric-ferrous redox reaction on a passivated sphalerite electrode is studied by the application of chronoamperometry method in 0.5 mol L-1 H 2 SO 4 solution. The electrochemical behaviour of ferric and ferrous couple was investigated on two sphalerite minerals acquired from two different geological regions (Iran and Canada). The carbon paste electrode (CPE) of sphalerite was initially prepared and passivated in 0.5 mol L-1 H 2 SO 4 solution and after reaching the steady-state condition, ferric and ferrous sulfate solution was added. The registered current density differences between the current density of the passivated electrode and that of the electrode in the iron salts added solution were interpreted for kinetics of ferric-ferrous reduction-oxidation reaction. The equilibrium potential for ferric-ferrous couple on sphalerites surface was about 500 mV vs. Ag/AgCl. The exchange current density (i 0) for ferric-ferrous redox reactions on the sphalerite samples had the same magnitude of 10 –6 A cm –2. The electrochemical impedance spectroscopy (EIS) measurements at 550 mV vs. Ag/AgCl illustrated that sphalerite oxidation was controlled by two charge transfer process in both of Fe-free and Fe-containing solutions. The charge transfer resistance remarkably decreased when Fe salts added to the 0.5 mol L-1 H 2 SO 4 solution, owing to the ferric-ferrous redox reactions being the predominant reactions on sphalerite surface.
... Additionally, the oxidation of landfill leachate using persulfate demonstrates its superior performance over hydrogen peroxide and permanganate. Finally, the recovery of zinc, gold, silver and lithium using persulfate systems has been successfully developed (Alzate et al., 2016;Babu et al., 2002;Hyk and Kitka, 2017;Ji et al., 2017;Syed, 2006;Zhong et al., 2017). The oxidizing power of persulfate compounds could be explained by the activation of S 2 O 8 2À under the addition of heat, UV irradiation or transition metals (Eqs. ...
The present paper reports the application of ammonium persulfate ((NH4)2S2O8) assisted with oxygen and pressure to recover gold from electronic waste (e-waste). This process suggests the selective breaking of metallic bonds to release gold from its substrate without grinding stages or pollutants generation. Waste printed circuit boards were analyzed to determinate base metals (Ni, Fe, Cu) and gold (Au) using microwave plasma atomic emission spectroscopy. After chemical characterization, aqueous commercial grade ammonium persulfate was used to produce the persulfate anion (S2O8²⁻) and the oxidative sulfate ion (SO4²⁻), which partially oxidized and leached the base metals breaking the Au–Ni–Fe–Cu bonds and allowing gold to be recovered in its original non-leaching state. The influence of oxygen and pressure in the base metals oxidation and gold recovery were separately studied in two different oxidative systems and evaluated by analysis of variance. Firstly, the system S2O8²⁻/O2 was studied under the addition of oxygen (0.1–1.0 L/min) with (NH4)2S2O8 concentration (0.66–1.31 M), and liquid/solid ratio (15–25 mL/g). Secondly, the system S2O8²⁻/Pressure was evaluated increasing pressure (101–203 kPa) with (NH4)2S2O8 concentration (0.66–1.31 M), and liquid/solid ratio (15–25 mL/g). The recovery of gold was made using optimal conditions and reaction times of 30 min in the S2O8²⁻/O2 system and 5 min in the S2O8²⁻/Pressure system. At those reaction times, gold was recovered in its solid state and was analyzed using scanning electron microscopy. The findings presented in this paper suggest that the oxidative reaction produced by the system S2O8²⁻/Pressure could be applied to release and recover gold from e-waste with an effective reduction of the agent consumption and minimum time.
... Though it has showed tremendous value to the development of zinc industry, its defects on environment protection, energy saving, and limiting raw materials, put serious restrictions on its application [2]. And the present wildly used hydrometallurgy processes also exist some disadvantages, such as low efficiency, complex operation, and high demand for apparatus, etc. [3][4][5][6][7][8][9]. Therefore developing cost-effective meanwhile environment-friendly processes remains a major challenge. ...
A novel process for the treatment of zinc sulfide ores is discussed in this paper, which consists of two procedures: microwave roasting pretreatment and synergistic chelation. What’s more, the reaction mechanism also has been studied. By comparing XRD patterns before and after roasting, it can be concluded that microwave truly alleviates the reaction energy, and adding Na2O2 avoids the emission of SO2. % recovery of zinc can reaches 72.47 % on conditions of adding Na2O2 25 %, microwave activating temperature 500 °C, holding time 10 min, leaching temperature 40 °C, ultrasonic wave power 1,800 W, leaching time 4.5 h and solid to liquid ratio 10:1 in ammonium chloride solution whose total ammonium concentrate is 7.5 mol/L (c(NH3)T=7.5 mol/L). The molar ratio of NH4Cl and NH3·H2O is 1:1 (c(NH4Cl): c(NH3·H2O)=1:1). The effect of ultrasonic wave power in this process is to shorten reaction time.
... Zinc is the third most common nonferrous metal after aluminum and copper, which has wide application in the areas of plating, coating and alloying [1][2][3]. Currently, 80 %-85 % zinc is produced from zinc sulfide concentrates by the hydrometallurgical methods of roasting-acid leaching-purifying-electrowinning process or oxygen pressure acid leaching-purifying-electrowinning process worldwide [4]. Copper and cadmium are the main associated valuable metals in zinc resources and can be leached out in company with zinc, which have to be removed to avoid their influence on subsequent zinc electrolysis. ...
An intensified oxidative acid leaching of copper–cadmium-bearing slag featuring using high-efficient oxygen carrier, such as activated carbon, was investigated to achieve high leaching rate of valuable metals. The effects of leaching variables, including agitation rate, sulfuric acid concentration, temperature, slag particle size, activated carbon and cupric ion concentration, were examined. It is found that leaching rates of cadmium and zinc both exceed 99 % in a very short time, but for copper, leaching rate of 99 % is achieved under the optimized leaching parameters, which are agitation rate of 100 r·min−1, sulfuric acid concentration of 15 wt%, leaching temperature of 80 °C, slag particle size of 48–75 μm, activated carbon concentration of 3 g·L−1, liquid-to-solid ratio of 4:1, oxygen flow rate of 0.16 L·min−1, and leaching time of 60 min. The macro-leaching kinetics of copper metal was analyzed, and it is concluded that the inner diffusion is the controlling step, with apparent activation energy of 18.6 kJ·mol−1. The leaching solution with pH value of 2–4 can be designed to selectively extract valuable metals without neutralization, and the leaching residue can be treated by prevailing Pb smelting process.
Graphical Abstract
The phase compositions of the leaching residue are PbSO4 and CaSO4. And the chemical composition analysis result shows that about 13 % Pb is contained in the residue, which can be recycled by Pb smelting technology in an Isa furnace. The way is that the Pb-containing concentrate and the PbSO4-containing leaching residue can be mixed and placed in the furnace.
... In addition, the produced persulfate ions (S 2 O 8 2À ) are not absorbed or bio accumulated in the soil after the process (Hernandez, 2005) and the generated by-products (sulfates) have not a negative effect on the environment (Syed, 2006). Comparing with potassium persulfate, sodium persulfate and cupric chloride, (NH 4 ) 2 S 2 O 8 has a greater leaching power to oxidize base metals than potassium and sodium persulfate (Babu et al., 2002) and is operationally safer and less toxic than CuCl 2 . The toxicity reduction responds to the absence of Cl 2 (g) during the reaction. ...
This paper presents a novel methodology to recover gold from waste electrical and electronic equipment (WEEE) using ammonium persulfate ((NH4)2S2O8). Gold was recovered as a fine coating using substrate oxidation without shredding or grinding process. The WEEE sample was characterized giving values of Au: 1.05 g/kg, Fe: 86.00 g/kg, Ni: 73.64 g/kg, Cu: 26.65 g/kg. The effect of (NH4)2S2O8 concentration (0.22–1.10 M), oxygen (0.0–1.4 L/min) and L/S ratio (10–30 mL/g) on the main responses (substrate oxidation and Au recovery) was investigated implementing response surface methodology with numerical optimization. A quadratic model was developed and quantities greater than 98% of Au were recovered. The findings presented suggest that, optimized quantities of ammonium persulfate in aqueous highly oxygenated media could be used to extract superficial gold from WEEE.
... Bypassing the roasting stage for metallic zinc production is mostly preferred from economic and environmental perspective. For this purpose, two alternative processes were proposed in the 1970's and several different leaching studies have been accomplished by many researchers in the course of time: Direct atmospheric leaching in which sphalerite concentrates are leached directly with some oxidizing agents such as acids (Copur, 2002), alkalis (Zhang et al., 2008), ferric salts (Crundwell, 1987;Dutrizac, 1992;Jin et al., 1993;Palencia Perez and Dutrizac, 1991;Santos et al., 2010), hydrogen peroxide (Balaz and Ebert, 1991), oxygen, ammonium, sodium and potassium persulfates (Babu et al., 2002), manganese dioxide (Rao and Paramguru, 1998), and bacteria (da Silva, 2004;Gomez et al., 1997;Haghshenas et al., 2012); and pressure leaching carried out using oxygen under pressure with similarly contributing some oxidizing agents in autoclaves (Baldwin and Demopoulos, 1995;Dehghan et al., 2008;Gu et al., 2010;Harvey et al., 1993;Li et al., 2010a;Xie et al., 2007). ...
The zinc leaching from sphalerite concentrate using oxygen under pressure in sulfuric acid solution was primarily studied and evaluated. The effects of important leaching parameters such as oxygen partial pressure, temperature, solid/liquid ratio and leaching time on leaching efficiency, Zn concentration and Fe extraction were investigated. Response surface methodology based on central composite rotatable design technique was used to optimize the leaching process parameters in order to obtain a suitable leach solution with high Zn leaching efficiency considering further processes such as precipitation of contaminating metal ions and electrolysis. The optimum leaching condition for maximum Zn leaching efficiency and Zn concentration with minimum Fe extraction was determined as follows: oxygen partial pressure of 12 bars, temperature of 150 °C, solid/liquid ratio of 0.20 and leaching time of 89.16 minutes. The achieved experimental results for Zn leaching efficiency, Zn concentration and Fe extraction under the optimum conditions were as 94%, 80 g dm-3 and 8.1% respectively. The experimental results corresponded well with the predicted results of quadratic polynomial models.
... The activation energy was found to be 22.91 kJ/mol. The kinetic study developed by Babu et al. (2002) indicated that the leaching of zinc in ammonium persulfate followed a diffusion-controlled model and the rate was governed by the diffusion of lixiviant through porous sulfur layer as the reaction product. The activation energy was found to be 41 ± 2 kJ/mol. ...
Our research aims the development of an eco-friendly leaching method for the separation of electronic components with high gold content, from other parts of waste printed circuit boards (WPCBs) without the use of any other separation technique. The base metals were removed in a specially designed leaching reactor using acidic FeCl3 solution. The dependency of the dissolution rate of base metals on the amount of FeCl3 and solid: liquid ratio was determined based on a kinetic model developed in MATLAB. The kinetic parameters identified by the experimental results indicate that the leaching rate of metals is more strongly dependent on the amount of FeCl3 used than on the solid: liquid ratio. The optimal values of the operating parameters were established in order to maximize the amount of dissolved metals and minimize the oxidant consumption.
... The activation energy was found to be 22.91 kJ/mol. The kinetic study developed by Babu et al. (2002) indicated that the leaching of zinc in ammonium persulfate followed a diffusion-controlled model and the rate was governed by the diffusion of lixiviant through porous sulfur layer as the reaction product. The activation energy was found to be 41 ± 2 kJ/mol. ...
... Zinc is an important base metal in the galvanizing and battery manufacturing industries [1]. The main source for zinc metal production is zinc sulfide ore [2][3]. Currently, with the gradual depletion of zinc sulfide ore and the rapidly rising demand for zinc metal, much research is focused on zinc oxide ore [4][5][6][7]. ...
Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by (NH4)2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and (NH4)2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows: 1 − (1 − α)1/3 = 30.85 exp(−45.57/RT)·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.
... The pyrometallurgical process of zinc oxide ores has almost been eliminated for its high raw material requirement, poor raw material adaptability, low resource utilization rate, high energy consumption and serious environmental pollution, and it is widely accepted that hydroleaching, especially alkaline leaching which can avoid forming of gel SiO 2 and alleviate subsequent solid-liquid separation load [1,2], is the trend of times and broad in prospect. What's more, ammonia leaching is evaluated as the optimal advanced clean zinc production technology for the following advantages [3][4][5][6]: (1) abundance in raw materials; (2) short process; (3) leaching solution easily purify; (4) more production varieties and (5) high selectivity. ...
The effects of sodium citrate on ammonium sulfate recycled leaching of low-grade zinc oxide ores were studied. By applying various kinds of detection and analysis techniques such as chemical composition analysis, chemical phase method, scanning electron microscopy and energy dispersive spectrum (SEM/EDS), X-ray diffraction (XRD) and Fourier-transforming infrared spectrum (FT-IR), zinc raw ore, its leaching slag and the functional mechanism of sodium citrate were investigated. Based on a comprehensive analysis, it can be concluded that in contrast to hemimorphite (Zn
... Persulfate compounds are strong oxidizing agents that are reduced to sulfates in solution during the oxidation process. The oxidizing properties are thought to be a significant advantage for the leaching of sulfide materials [35,36]. The cathodic reaction of persulfate salts is represented as ...
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.
... Increasing cadmium extraction, as acid concentration increases, is due to acid concentration effect on increasing the H + activity that result in further dissolution of cadmium containing material. Similarly (Babu et al., 2002), also confirmed that the zinc extraction from zinc sulphide concentrate is a function of sulphuric acid concentration. Increasing metal extractions by increasing leaching agent concentration were also observed by Bodas (1996) and Souza et al. (2007). ...
In the present paper cadmium leaching from zinc plant residue using sulphuric acid was examined. The zinc plant residue is a hazardous waste which is produced in the hydrometallurgical zinc plant and it contains considerable amounts of metals such as zinc, cadmium and nickel. The effects of sulphuric acid and other important factors such as reaction time, solid-to-liquid ratio, particle size, stirring speed and temperature on cadmium recovery were investigated. The concentration of cadmium in solution was observed to increase with the increase of the reaction time, acid concentration, stirring speed and temperature. Decreasing of solid/liquid ratio and particle size were also beneficial for cadmium recovery. The largest cadmium leaching recovery (97%) was obtained after 30 minutes of treatment at 25°C using H 2 SO 4 (8% (v/v)) at solid-to-liquid ratio of 0.10. XRD and SEM analyses of the residues obtained after leaching showed that the cadmium containing phase had been decomposed in the leaching residues. The results indicated that it is possible to use this waste as a secondary resource for cadmium recovery.
تحقیق حاضر مروری بر فرایندهای استحصال فلز روی به روش هیدرومتالورژی و خلاصه ای از پژوهشها و تحقیقات علمی منتشر شده با هدف تولید هیدرومتالورژی این فلز، از منابع سولفیدی و غیرسولفیدی و هم چنین به طور خاص مطالعه ی عوامل لیچینگ اسیدی و قلیایی کنسانتره های روی میباشد. این روش که قابلیت بازیابی انتخابی از ذخایر کم عیار را با هزینه های به صرفه تر از پیرومتالورژی فراهم کرده، کاربردی تر و اقتصادی تر از سایر روش ها است. فرایند هیدرومتالورژی شامل سه روش: تشویه_لیچینگ_الکترووینینگ، لیچینگ تحت فشار و لیچینگ مستقیم اتمسفری می باشد، که به علت هزینه های بالای روش اول و مشکلات عملیاتی در لیچینگ تحت فشار، فرایند لیچ مستقیم اسفالریت به صنعت تولید روی وارد شده است و امکان لیچ کنسانتره های با عیار پایین را فراهم کرده که طی این فرایند گوگرد موجود در اسفالریت به عنوان محصول فرعی به صورت گوگرد عنصری قابل بازیابی می باشد. باتوجه به اینکه هر ذخیره کم و بیش منحصربه فرد است، از این رو برای رسیدن به شرایط بهینه و عیار بالای روی در فرایند، نیاز به شناخت دقیق فرایند لیچینگ و بررسی پارامترها و عوامل لیچ اسیدی و قلیایی کنسانتره ی سولفیدی و غیرسولفیدی روی داریم.
Germanium-containing dust as an intermediate by-product in the process of zinc hydrometallurgy, which often contains a large number of heavy metal substances. Due to the constraints of economic benefits and process technology, green and efficient treatment of germanium-containing dust is always a great challenge. In this work, XRD, XRF, XPS, SEM and other characterization methods were used to analyze the existing state and quantity of main substances in germanium-containing dust. It was found that the occurrence state of germanium was closely related to sphalerite. At the same time, longer reaction time would lead to continuous hydrolysis of silicate, which would eventually affect the recovery of zinc, germanium and lead and the fixation of toxic substances. Therefore, the ultrasonic enhanced ammonium persulfate oxidation process was proposed to control the waste of resources and environmental pollution caused by the accumulation of germanium-containing dust. The final results showed that more than 95% of zinc and 89% of germanium were efficiently recovered, and heavy metals such as arsenic and cadmium were fixed in the liquid, and then concentrated in the purification and impurity removal stage. The residue after reaction is high-grade lead sulfate residue, which can be returned to the lead smelting system for recycling. In summary, the ultrasonic-enhanced ammonium persulfate process eventually makes all substances in germanium-containing dust harmless and resource treatment.
To achieve the high value-added utilisation of steelmaking slag, the separation of P from steelmaking slag is crucially important. Because P is primarily concentrated in the C2S–C3P solid solution, acid leaching was adopted to dissolve and separate the solid solution from the P-bearing steelmaking slag. The effects of leaching parameters on the dissolution behavior of P in the citric acid solution were investigated. The results indicated that decreasing particle size and pH significantly increased not only the leaching rate of P but also the dissolution ratio of P. Increasing temperature enhanced the leaching rate of P whereas had little influence on the dissolution ratio of P. At pH 5, the dissolution ratio of P reached 85.1% and only 6.7% of Fe was dissolved, achieving selective leaching of P. The dissolution kinetics of P followed the shrinking core model, which was controlled by the diffusion through the residue layer.
An experimental investigation was carried out to improve the zinc dissolution rate in the direct atmospheric leaching of marmatite by adding sodium chloride to the sulfuric acid-ferric sulfate‑oxygen media. The experiments were carried out by using mono-sized marmatite particles varying the concentrations of sulfuric acid from 0.1 to 1.3 M, ferric sulfate from 0 to 0.8 M, sodium chloride from 0 to 1.3 M, and temperature in the range of 60 to 95 °C. The results showed that the addition of 0.7 M of sodium chloride improved drastically the direct leaching kinetics of the zinc sulfide; therefore, this leaching media is an excellent alternative to produce zinc from marmatite concentrates at ambient pressure. The sulfuric acid concentration was also found to have a significant effect on the rate of dissolution, indicating that the non-oxidative dissolution of marmatite plays an important role in the reaction mechanism in this system. A shrinking core model with diffusion through a product layer control was found to fit the reaction rate. An apparent activation energy value of 81.8 kJ/mol was found for the temperature range of 60–95 °C. The direct atmospheric leaching of marmatite in H2SO4-Fe(SO4)1.5-NaCl-O2 is an excellent alternative method to extract zinc due to high dissolution rates obtained in the presence of chloride ions, reducing substantially the treatment times.
Regulations force to Waste Electrical and Electronic Equipment (WEEE) management by recycling the materials by safe and suitable methods, due to generating massive amounts of WEEE. This research aims towards extract metals from waste random-access memory (RAM) devices in different solutions. In addition, the effect of different parameters such as reagent concentration, oxidant concentration and solid/liquid ratio were investigated with full factorial experimental design tests and analysis of variance (ANOVA). The results showed that the extraction of gold and silver was 96.81% and 99.02% respectively under the following conditions: concentration of 2% iodine and 3% hydrogen peroxide as oxidizing agent, 5% solid/liquid ratio and leaching period of 2 h. An increase of the hydrogen peroxide concentration increased gold and silver extraction. While about 79.30% silver was found to be extracted using 2 M sulfuric acid, 1.5 M ammonium persulfate, 5% solid/liquid ratio and leaching period of 5 h, 79.43% copper was extracted by using ammonia instead of sulfuric acid under the same conditions. Ammonium persulfate was found to be a good oxidizing agent for sulfuric acid and ammonia leaching, since it provided selective extraction of silver and copper respectively. Two-step sequential bench scale reactor leaching tests were conducted to extract copper (98.73%), gold (99.98%) and silver (96.90%) selectively with high extraction. Two-step leaching approach was concluded as the most appropriate method for selective extraction of targeted metals from waste RAM devices.
Direct leaching of sphalerite has been considered as a cost effective and an environmentally benign alternative to the traditional two-step roasting-leaching approach. Yet the slow leaching rate due to the formation of surface passivating phases remains the main challenge. Here, we studied the mechanism and kinetics of sphalerite leaching in the temperature range of 35–130 °C using three oxidants, Fe2(SO4)3, FeCl3, and Fe(NO3)3, and observed distinctly different surface passivation and significantly different leaching rate. Leaching using Fe2(SO4)3 was the slowest, due to the formation of passivating surface layers of sulfur at the early stage and hydrated (Fe,Zn)-sulfates at the later stage. The formation of hydrated (Fe,Zn)-sulfates reduced Zn extraction by up to 20%, leading to incomplete Zn extraction. Using FeCl3, leaching was faster than in Fe2(SO4)3. However, the formation of surface sulfur also caused passivation. Leaching in Fe(NO3)3 was the fastest, as the initially formed surface sulfur was quickly oxidized to sulfuric acid and hence passivation was negligible. Using Fe(NO3)3, complete Zn extraction from 106 to 150 μm sphalerite particles took 7 days at 35 °C, 2 days at 70 °C, 5 h at 90 °C, and 1 h at 130 °C. This is about one order of magnitude and two orders of magnitude faster than leaching in FeCl3 and Fe2(SO4)3, respectively. The observed leaching behaviors were in agreement with changing activation energy as a function of leaching extent, analyzed by the modified ‘time-to-a-given-fraction’ method. In the case of Fe2(SO4)3 and FeCl3, leaching was controlled by phase-boundary reactions at the early-to-middle stages, but changed to diffusion control at the later stage after the formation of passivating surface layers; in the case of Fe(NO3)3, leaching was controlled by phase boundary reactions over the entire leaching process. This work demonstrates that Fe(NO3)3 is the more efficient oxidant than FeCl3 and Fe2(SO4)3 for fast leaching of sphalerite at low temperatures with minimum surface passivation.
Bu çalışma, alternatif çözücüler kullanarak bakır, altın ve gümüşün geri kazanımı için atıkmerkezi işlemci ünitelerinin (CPU) liç süreciyle ilgilidir. Fiziksel ön işlemler (boyut küçültme,ayıklama) ve hidrometalürjik yöntemler kullanılarak yüksek verimlerle metallerin kazanımıhedeflenmiştir. Kimyasal liç testleri kapsamında 23 tam faktöriyel tasarım testleri yürütülmüştür.Metal kazanım verimi üzerine reaktif (I2, H2SO4, NH3) derişimi, oksitleyici (H2O2, (NH4)2S2O8)derişimi, katı/sıvı oranının etkileri, varyans analizi (ANOVA) ile incelenmiştir, etkin değerlere bağlımodeller oluşturulmuştur. Metal kazanımlarını arttırmak amacıyla iki aşamalı reaktör liçi testleriyürütülmüştür. Birinci aşamada H2SO4+H2O2 liçi ile %95,60 bakır, ikinci aşamada I2+H2O2 liçi ile%99,92 altın, %99,81 gümüş kazanım verimleri elde edilmiştir.
Low-nickel matte was intensively characterized, and Ni, Cu, and Co were determined to exist mainly as (Fe,Ni)9S8 and FeNi3, Cu5FeS4, and (Fe,Ni)9S8 and Fe3O4 (in isomorphic form), respectively. The efficient and selective extraction of Ni, Cu, and Co from the low-nickel matte in an (NH4)2S2O8/NH3·H2O solution system was studied. The effects of (NH4)2S2O8 and NH3·H2O concentrations, leaching time, and leaching temperature on the metal extraction efficiency were systematically investigated. During the oxidative ammonia leaching process, the metal extraction efficiencies of Ni 81.07%, Cu 93.81%, and Co 71.74% were obtained under the optimal conditions. The relatively low leaching efficiency of Ni was mainly ascribed to NiFe alloy deactivation in ammonia solution. By introducing an acid pre-leaching process into the oxidative ammonia leaching process, we achieved the high extraction efficiencies of 98.03%, 99.13%, and 85.60% for the valuable metals Ni, Cu, and Co, respectively, from the low-nickel matte.
Mixed sulfide-oxide lead and zinc ores are generally composed of both sulfides and oxides. The dissolution of sulfides is more difficult than oxides thus the addition of oxidant is necessary. In this paper, oxidative leaching of mixed ore in NH3-(NH4)2SO4 solution using ammonium persulfate as oxidant under atmospheric pressure and relatively low temperature was investigated for the first time. The effects of factors on the leaching of pure ZnS were studied and the optimal conditions with zinc 98.7% were determined. Selective and efficient extractions of 93.9% and 94.9% zinc from zinc sulfide ore and mixed ore were also achieved, respectively.
The catalytic and galvanic effects of pyrite on the dissolution kinetics of a zinc sulfide concentrate in an acidified ferric sulfate medium were assessed. The effects of particle size, oxidant concentration (ferric ion), and amount of pyrite added with respect to the original amount of zinc concentrate was explored, while temperature (70 °C), hydrogen potential (pH = 1.0) and agitation speed (600 rpm) of the leach solution were held constant. A process based on the galvanic coupling between pyrite and sphalerite at solution potentials above 500 mV to ensure rapid and complete sphalerite dissolution in a ferric sulfate medium is proposed. As a result, the highest zinc extraction in the shortest possible time was obtained through minimizing the formation of a passivating film, which inhibits further reaction, and by a synergetic effect between pyrite and sphalerite. The rate of zinc leaching was considerably improved by doping with pyrite in the presence of Fe3 +. The results have demonstrated that it was possible to achieve 98.9% zinc extraction with doping pyrite in 6 h and 85% zinc extraction without pyrite in 7 h, both results being for a fine grain size. Ferric leaching reached 75% Zn extraction with doped pyrite and 70% without it, both in 7 h using a coarse grain size. Scanning electron microscopy (SEM) images show a passivating layer on the sphalerite surface after ferric leaching without pyrite, while in presence of pyrite this layer was not observed and the pyrite surface was not attacked. The galvanic interaction between pyrite and sphalerite particles can be explained by the difference between their Fermi energies and the electrochemical potential of the solution. During this process pyrite remains mostly unleached, acting as a redox catalyst (electron-accepting) for sphalerite (electron-donating) dissolution. This diminishes the typical passive behavior of sphalerite in a ferric solution enhancing considerably the kinetics of sphalerite. This confirms that the difference between the rest potentials of pyrite and sphalerite is the driving force that improves zinc dissolution. For an industrial hydrometallurgical operation, using an appropriate sphalerite-pyrite concentrate does not necessarily represent a significant cost because the ore contains both sulfides.
Employing the ammonium jarosite by eliminating iron in the digestion solution of the clinker that was obtained from baking the zinc oxide ore using ammonium sulfate as raw material and NaOH as reaction medium, the wet chemistry method was adopted to decompose the ammonium jarosite, which was aim to achieve the comprehensive utilization of it. The influences of the decomposition temperature, time, decomposition pH value and liquid-solid ratio on the conversion rate of the ammonium jarosite were investigated, and the appropriate reaction conditions were also gained. The XRD, SEM and components analysis were used to characterize the decomposition product. The results indicated that the decomposition product was ferric oxide hydrate that was decomposed to Fe2O3 in dying but not completely. The morphology of Fe2O3 was almost the same to that of the ammonium jarosite with more rough surface.
ZnSO4 solution was used as a raw material, which was obtained from zinc oxide ores roasted using (NH4)2SO4 and then digested in water. The main components in solution were ZnSO4, Fe2(SO4)3, Al2(SO4)3 and so on. NH4HCO3 was used as purifier reagent. Aiming to obtain refined ZnSO4 solution, the ammonium jarosite method and hydrolysis method were adopted to eliminate Fe3+ and Al3+ from the solution. The influences of pH values, the reaction temperature and time on the iron removal rate were discussed, and after the removal of iron, the ammonium jarosite slags were obtained. The pH value of solution was adjusted to precipitate Al3+ and Al(OH)3 was yielded out. The XRD, SEM and chemical components analysis were used to characterize the ammonium jarosite and Al(OH)3 slags. The results showed that the ammonium jarosite particles with regular shape growes well, and the size of Al(OH)3 slags is heterogeneous.
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.
Some effective parameters on the copper extraction from Küre chalcopyrite concentrate were optimized by using response surface methodology (RSM). Experiments designed by RSM were carried out in the presence of ammonium persulfate (APS) and different types of impeller in an autoclave system. Ammonium persulfate concentration and leaching temperature were defined numerically and three types of impellers were defined categorically as independent variables using experimental design software. The optimum condition for copper extraction from the chalcopyrite concentrate is found to be ammonium persulfate concentration of 277.77 kg/m3, leaching temperature of 389.98 K and wheel type of impeller. The proposed model equation using RSM has shown good agreement with the experimental data, with correlation coefficients R 2 and R adj 2 for the model as 0.89 and 0.84, respectively.
Although the classification of hydrometallurgical processes is arbitrary, it is convenient to consider two general areas: (1) the leaching of ores, and (2) the leaching of concentrates. In some cases these ores or concentrates may be subjected to some pretreatment such as roasting or reduction to improve the extraction. By definition, an ore deposit is a naturally occurring mineral deposit which can be treated economically. Under this definition the leaching of low-grade materials, normally considered to be waste products, would fall into the first category and would, if leached at a profit, be termed an ore. Ores within this definition may be subdivided into low-grade materials and moderate-to-high-grade ores. The first would refer to materials of sufficiently low grade that it is not economic to subject them to additional treatment such as fine grinding and concentration, although sizing may be carried out. The diagram in Figure 3.1–1 illustrates the classification of hydro-metallurgical treatment according to the above definition.
Recent studies on chloride leaching of sphalerite are rewieved. The kinetics of oxygen leaching of sphalerite in concentrated ammonium chloride solutions in the presence of cupric ion has been studied. A pure sphalerite and a zinc concentrate have been tested. 80-130 °C temperature range, the dissolution occurred according to a mixed model which assumed both diffusion through sulfur layer and a surface reaction in the shrinking core model. This is described mathematically as: [1-(1-X)1/3] + B [1 -2/3 X-(1-X)2/3] = krt. The effect of temperature, cupric concentration and particle size on the dissolution rate were determinated. The activation energy of the rate constant kr for the pure sphalerite and zinc concentrate was found to be 66.4 and 67.6 kJ/mol respectively. The dissolution rate increased as the 0.43 power of the cupric cloride concentration. The results obtained for the effect of particle size show, such as it is predicted by the kinetic mixed model, that the rate constant kr is inversely related, and the parameter B is directly related, to particle radius.
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.
Ammonium persulfate oxidation as well as anodic oxidation using chemical lead anodes were evaluated for manganese ion removal. Chemical oxidation employing ammonium persulfate can be used.
This paper describes a new approach for examining the kinetics and mechanism of zinc dissolution from sphalerite concentrate in acidic-ferric sulfate solution in the presence of manganese dioxide. A literature search was performed to access the possible action of the two oxidizing agents, i.e., ferric ion and manganese dioxide. The possibility of galvanic coupling between ZnS and MnO9 and the cyclic action of the redox couple, Fe2+/Fe3+, on these two minerals were theoretically examined based on corrosion principles. Expressions for the mixed potential (Em) and the mixed current (im) were derived for the relevant corrosion and galvanic couples. Leaching experiments were conducted to establish which of the above phenomena is operative during leaching. The results indicated that the dissolution mostly occurs by the action of ferric ion on ZnS producing ferrous ions. The presence of MnO2 enables a quick conversion of ferrous to ferric, which maintains the rate of Zn dissolution. The process has promising features for commercial exploitation.
This paper examines the influence of cobalt and silver ion concentration on the extraction and kinetics of zinc dissolution from sphalerite. The mechanism involves catalysis of a galvanic oxidation! reduction that produces elemental sulfur in place of SO2 gas.
A 95% maximum zinc recovery was achieved under the experimental conditions. The apparent activation energy suggested a diffusion controlled reaction. The research indicates that cobalt ions are more effective than silver ions because the replacement of zinc ions is facilitated by dimensional similarities between the zinc and cobalt.
In this 1976 extractive metallurgy lecture of the Metallurgical Society of AIME, the sulfide minerals associated with copper, nickel, zinc, lead, and molybdenum concentrates are described according to their thermodynamic stability zones on Eh-pH diagrams. From these zones, the chemistry associated with various thermodynamically feasible decomposition paths is discussed, and process developments associated with the most favorable decomposition paths are briefly reviewed. The advantages of hydrometallurgical extraction of Cu, Ni, Zn, Pb, and Mo sulfide minerals, especially from the viewpoint of environmental pollution, are pointed out.
The hydrometallurgical processing of zinc sulphide concentrates with sulphuric acid in the presence of manganese dioxide (manganese ore has been employed) and subsequent electrolytic co-deposition of cathodic zinc metal and anodic manganese dioxide is described.The influence of various parameters on the reaction has been studied. Optimum conditions for rapid and efficient reaction have been determined.The simultaneous electrowinning of zinc at the cathode and γ-MnO2 at the anode from the leach liquor was studied. The effects of variation of current density, temperature, electrolyte composition etc. have been described in detail. During leaching 99% extraction of zinc, 98% of manganese, and 96% liberation of elemental sulphur was achieved. 80–90% anodic and cathodic current efficiencies can be obtained under optimum conditions with impurity levels of only a trace of manganese in the zinc deposit and vice-versa.The anodically deposited manganese dioxide was the γ-battery active variety and was found to be satisfactory.The results indicate the potential for the development of a technique for zinc and manganese dioxide production in a single cell.
The purpose of this paper is to review the leaching of base metal sulfides and of uranium oxides by acidic ferric ion media. A description is also given of the preparation, regeneration, and properties of such leaching media. From the discussion of the kinetics of reaction of various minerals with ferric ion, it emerges that, for many minerals, the reaction rates are sufficiently rapid to be of commercial interest for recovering the sought-after metal. A brief discussion of actual and proposed commercial processes using ferric ion leaching is also given.
The bench scale pressure leaching of a sphalerite concentrate in the presence of different surfactants under high pulp density conditions has been studied. The surfactants were used as dispersants for liquid sulfur, which is a by-product of the elevated-temperature leaching process. The leaching times were 35 or 60 min. The surfactants used were orthophenylene diamine (OPD), lignin sulfonic acid and metaphenylene diamine (MPD). Over 99% zinc extraction was achieved in the presence of OPD for all leaching times and surfactant concentrations. Lignin sulfonic acid and MPD resulted in 86–94% and 95–98% zinc extraction, respectively. In the absence of any surfactant, the extraction was about 50% after 60 min of leaching. Iron extraction increased from 40%, in the absence of any surfactant, to about 80% in the presence of OPD and 62–70% in the presence of lignin sulfonic acid or MPD.
Direct chemical oxidation (DCO) is an emerging technology in which the organic components of hazardous or mixed waste streams are mineralized to carbon dioxide by the nearly omnivorous oxidant peroxydisulfate. Following treatment, the expended oxidant may be electrochemically regenerated to lower costs and minimize secondary waste; however, due to the varied contents of potential waste streams, trace chemical species may slowly accumulate in the system. To verify that the electrochemical recycling step was not adversely affected, the effect that several species have on the efficiency of this peroxydisulfate regeneration step has been measured. The organic additives formaldehyde, formic acid, and oxalic acid were tested, as well as the inorganic ions phosphate, nitrate, fluoride, chloride and thiocyanate. Changes in the peroxydisulfate formation potential in the presence of these additives were measured using chronopotentiometry, with current densities from 0.5 to 2.0 Acm–2, and additive concentrations of 0.1mm to 0.1m. Also, a real-time technique using a rotating disc electrode was developed to measure these additives' effect on the formation kinetics of peroxydisulfate. In addition, the effect that various additives had on the rate of electrochemical peroxydisulfate generation was measured in a large-scale electrolysis cell. None of the additives caused a significant reduction in the potential or the efficiency of the peroxydisulfate generation step, although the presence of formic acid appeared to increase the efficiency. In addition, the presence of thiocyanate completely blocks the reduction of peroxydisulfate on platinum. This information is currently being applied in scale-up testing of this technology for use in treating hazardous waste or the organic components of mixed waste.
Laboratory studies have been conducted on chloride leaching as a possible route for the simultaneous recovery of copper, zinc,
and lead from an off grade and complex chalcopyrite concentrate (from Sikkim, India) associated with appreciable amounts of
sphalerite, galena, and pyrite. The effects of temperature, concentration, and quantity of ferric chloride, stirring speed,
and leaching time on metal dissolution have been investigated. Leaching tests have also been conducted with in-dividual (HC1,
NaCl, CuCl2, FeCl3) and mixed chlorides (two-, three-, and four-component mix-tures). Results show the possibility of recovering not only 99
pct Cu and 89 pct Zn but also 82 pct Pb and 58 pct elemental S by treatment of the concentrate with 4 M FeCl3 at 383 K (110 °C) for 7.2 ks (2 hours) employing 25 pct excess FeCl3 and a stirring speed of 700 rev min−1. Though 64 pct iron of the concentrate is found to dissolve, the pyrite seems to remain unattacked. Kinetic studies indicate
that the chalcopyrite, sphalerite, and galena of the concen-trate dissolve simultaneously in the FeCl3 lixiviant as if each mineral is separately leached, and the Cu and Zn dissolution reactions are under chemical control (linear
kinetics). The addition of NaCl to the chloride lixiviants is found to be beneficial only up to a common salt concen-tration
of 100 g/l. Leaching of the copper concentrate with CuCl2 or mixed FeCl3-CuCl2-NaCl has not been as effective as its direct leaching with 4 M FeCl3.
The methods of BET, SEM, XRD and EPR were used for studying the changes in surface and bulk properties of sphalerite produced by mechanical activation in a vibrating mill. By leaching the mechanically activated samples with a 4% solution of hydrogen peroxide 65–100% recovery of zinc into the leach solution was achieved in the course of 120 min at atmospheric pressure and room temperature.In the process of mechanical activation of sphalerite the combined influence of surface area and bulk properties leads to a positive effect on the leaching kinetics and to further phenomena, among which their influence on the reaction course without having any side effects on the environment is the most significant.
Lead smelter slags from two different sources have been leached using sulfurous acid/oxygen as the leachant so as to dissolve zinc and copper values but not the contained iron. The differences in the leaching behaviour are explained in terms of the different slag compositions. The mixed control shrinking core model adequately described the relationship between fractional extraction and time.
Although considerable research has been reported on the hydrometallurgical behavior of zinc sulfide in chloride media, the electrochemical nature of the dissolution reaction involving a ferric/ferrous couple and the accelerating effects of the chloride ion and of cupric chloride have not been fully elucidated. It is shown that the decrease in dissolution rate of sphalerite in the presence of ferrous ions is due to a decreased cathodic half cell potential and therefore a less favorable mixed potential. The addition of chloride ion to the anodic half cell significantly increases the cell current, indicating that chloride ion plays a direct role in the anodic dissolution of ZnS and has relatively little effect on the cathodic half cell. It is also shown that Ag+ has no effect on the dissolution of ZnS in a ferric chloride electrolyte. In addition the data suggests that cupric ion may accelerate the dissolution of sphalerite through a mechanism other than simply providing an additional oxidizing reagent to complement ferric ion. This investigation has demonstrated the utility of a relatively simple, dual cell technique for the study of electrochemical leaching reactions by separating the two half reactions. Although this technique would not replace standard leaching experiments, it does provide a useful complementary approach, and in some cases can provide data that would be particularly difficult or impossible to obtain through typical, standard leaching experiments.
During the leaching of several sphalerite concentrates in acidic ferric sulfate solution, the dissolution rate of zinc decreases with time and overall conversion does not exceed 305. The growing elemental sulfur layer on the surface of each particle was found to be the cause of this passivation. To eliminate this phenomenon, a small addition of lignosulphonate (1 g/l) into the leaching solution was found to be effective. A conversion of over 60% was obtained.
Rev. ed. of: Vogel's textbook of quantitative inorganic analysis. 4th. ed. 1978 Incluye bibliografía e índice
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