Sulfuric Acid Leaching Process Research Articles

Selective removal of iron from sulfuric acid leaching solution of aerospace magnetic material scraps by jarosite process

Aerospace magnetic material scraps are abundant in cobalt and nickel. Sulfuric acid leaching process is an efficient method for extracting them. But it is a non-selective process, a significant amount of iron dissolves in the solution. This study focuses on the selective removal of iron from this solution using the jarosite process. Eh-pH diagram of K-S-Fe-H2O system was established. Based on thermodynamic analysis, H2O2 is used to oxidize Fe2+ into Fe3+, achieving efficient and selective removal of iron from the solution containing cobalt and nickel. The optimal conditions are as follows: temperature 95°C, K2SO4 dosage coefficient 1.5, seed dosage 10 g/L, time 90 min, pH 1.76, and endpoint pH controlled at approximately 3. Under these conditions, the iron removal efficiency is above 99%, while the loss ratios of cobalt and nickel are below 2%. The product is characterized by XRD and SEM-EDS. Results indicate that the product is jarosite ((K,H3O)Fe3(SO4)2(OH)6), exhibiting an ellipsoid structure with the mean particle size in the range of 0.2–5.0 μm. Temperature, pH value and seed dosage significantly affect reaction rate, particle size and crystallinity, and K2SO4 dosage mainly affects reaction rate and the morphology of jarosite. The jarosite crystallization kinetics can be described by the Avrami equation, with an Avrami index (n) of approximately 2.5 and the apparent activation energy of 42.68 kJ/mol.

An unconventional approach for the efficient recovery of iron, cobalt, copper and silicon from copper slag

High-grade heavy metal elements in copper slag (CS) are worth recovering. Unfortunately, the high viscosity of leaching solution, low leaching efficiency, difficult filtration and low separation efficiency of valuable components exist in the traditional sulfuric acid leaching process. In this study, the above problems are solved by sulfuric acid pretreatment + curing + water leaching. Moreover, iron, cobalt and copper ions in solution are separated by stepwise precipitation. The final iron, cobalt, copper and silicon recoveries are 99.01 %, 98.45 %, 93.13 % and 99.52 %, respectively. Thermodynamic calculations show that H4SiO4 can be converted to insoluble SiO2 to improve filtration properties under curing conditions of sulfur dioxide partial pressures of 10−20∼0 atm, oxygen partial pressures of 10−20∼0 atm and 400–600k. Simulation studies of the phase equilibria of the components of the leach solution by Visual MINTEQ showed that the oxidation of Fe2+ to Fe3+ is necessary for the removal of Fe2+ from the solution by precipitation. This study provides a new idea for the efficient utilization of CS.

Study on the treatment of pyrolysis products from the nitric acid pressure leach liquor of laterite

As the demand for nickel increases sharply, it is of great significance to extract valuable metals such as nickel and cobalt from lateritic nickel ore with huge reserves. Based on the nitric acid pressure leaching process (NAPL) of laterite nickel ore, a clean process of laterite nickel ore treatment is proposed. The process includes concentration and crystallization of pressure leaching solution of nitric acid, pyrolysis of mixed nitrate crystal, alkaline leaching of mixed oxides and acid leaching of alkaline leaching residue. Based on previous work, the high-pressure alkaline leaching process of pyrolysis products (mixed oxides) and atmospheric pressure sulfuric acid leaching process of alkaline leaching residue were studied in this paper. First, the Eh-pH diagrams of metal-water system of common elements in laterite nickel ore was summarized according to the reaction equations of different substances in aqueous solution, and the subsequent wet leaching process was guided. The following alkaline leaching experiments showed that under the conditions of 300 g/L NaOH concentration, 3.5 mL/g liquid–solid ratio, 160 °C leaching temperature and 1 h leaching temperature, 85.0 % of aluminum in mixed oxides can be leached and scandium can be enriched by 13 times. Finally, under the conditions of initial sulfuric acid concentration of 4 M, temperature of 100 °C, leaching time of 30 min and liquid–solid ratio of 4 mL/g, the leaching rates of Al, Ni, Mg, Co, Mn, Fe and Sc in alkaline leaching residue were 92.0 %, 97.5 %, 98.4 %, 92.3 %, 62.7 % and 68, respectively. A new procedure for treating lateritic nickel ore is proposed, allowing for thorough recovery and usage of important components. The technique is green and environmentally benign, resulting in closed-loop production of laterite-nickel ore treatment with numerous application possibilities.

Application of Plackett-Burman Design in the Screening of Factors Acting on the Sulfuric Leaching Process of Rare Earths from Moroccan Phosphogypsum

As the main waste of the phosphates industry (200–300 million tons per annum produced globally), phosphogypsum (PG) is a major environmental concern (85% of PG is disposed of on land or at sea). The valorization of PG as a secondary source of rare earth elements (REE) is one of the most recent valorization options under investigation. This study investigated the sulfuric acid leaching process of REE from a Moroccan PG. Plackett -Burman design was used to statistically screen significant factors affecting the leaching efficiency of REE named the studied response (Y). Seven factors considered potentially influential were studied as the model variables : Sulfuric acid concentration (X1); Solid to liquid ratio (X2); Drying temperature (X3); Leaching time (X4); Stirring speed (X5); Temperature (X6), Particle size (X7). According to the results, the predicted values of the fitted model were in good agreement with the experimental values by a coefficient of determination (R2) equal to (99 %). drying temperature has a statistically insignificant effect with p=0.336 > 0.05. All the other six variables have significant effects (p < 0.05), but 97,91 % of Y was affected only by the following four factors: X1 (63.71%), X4 (17.94%), X2 (9.98%) , X5 (6.24% ).

Facile and complete sulfuric acid leaching of zinc ferrite assisted by copper powder: Leaching mechanism and kinetics investigation

Zinc ferrite is a dominant phase in mass solid wastes generated from zinc or iron production, which causes the obstacle of metal recovery and recycling. A facile and efficient sulfuric acid leaching process of zinc ferrite assisted by copper powder was proposed in this study. The effects of factors on the leaching of zinc ferrite and copper were investigated. The results showed that zinc ferrite and copper were coupled and leached. The complete dissolution of zinc ferrite was obtained with wide ranges of leaching conditions. The shortest time for the complete dissolution of zinc ferrite was 10 min at 80 ℃ under the conditions: copper to zinc ferrite molar ratio of 1.5, sulfuric acid concentration of 100 g/L, liquid to solid ratio of 30 mL/g, and copper powder of + 38.5–20 μm. The least consumption of copper to realize the complete dissolution of zinc ferrite was 27.15%. The leaching kinetics was studied by the shrinking core model. It was found that zinc ferrite leaching assisted by copper was controlled by surface chemical reaction. The apparent activation energies for zinc, iron, and copper are 56 kJ/mol, 56 kJ/mol, and 50 kJ/mol, respectively. Characterization of the leaching residues and determination of iron and copper species in the leaching solution showed galvanic corrosion took place between zinc ferrite and copper, enhancing their acid dissolution.

Thermodynamics Study for Selective Leaching of Copper and Zinc from Complex Secondary Raw Materials Using Oxidative Sulfuric Acid Leaching

This study focuses on evaluating the optimal process conditions for selectively leaching copper and zinc from complex secondary raw materials using the oxidative sulfuric acid leaching process. The research includes both physical and chemical characterization of the materials and a comprehensive thermodynamic analysis to assess the thermodynamic properties and behaviors of the system under investigation. The physical characterization involves determining parameters such as bulk density, moisture content, and granulometric composition of the samples. Elemental composition analysis is performed using X-ray fluorescence spectrometry (XRF) and energy dispersion spectroscopy (EDX), while the phase composition is determined through X-ray diffraction (XRD) analysis. Additionally, the materials' morphology is examined using scanning electron microscopy (SEM). Fraction diagrams are created using Hydra/Medusa software to assess the phase distributions of zinc and copper during the leaching process. The stability of the metals and potential chemical reactions within a defined temperature range is analyzed using Eh-pH diagrams with the HSC 9 Chemistry Software. Based on the thermodynamic analysis conducted, it is determined that effective leaching of copper and zinc from the complex secondary raw materials is achievable. Furthermore, the results indicate that the leaching process is relatively insensitive to temperature variations. The optimization of the leaching process should primarily focus on achieving optimized consumption of the oxidizing agent.

Process optimization and mechanism of high-efficiency germanium extracting from zinc oxide dust containing germanium enhanced by ultrasound

Aiming at the problem of low extraction efficiency of germanium in zinc oxide dust, a process of strengthening germanium leaching by ultrasonic wave in sulfuric acid leaching process was proposed. The effects of acidity, temperature, time, liquid-solid ratio, ultrasonic power and amount of iron powder on germanium leaching were investigated by response surface method, and the ultrasonic enhanced leaching process was optimized. Based on process mineralogy analysis, and germanium phase distribution analysis, which is obtained by self-establishment step-by-step extract method, the studied zinc oxide dust contains 94.1% germanium oxide and germanate, 5.13% germanium sulfide and 0.77% insoluble germanium. The results showed sulfuric acid concentration 131 g/L(1.34 mol/L), temperature 78 °C, time 22 min, liquid-solid ratio 7.6:1, ultrasonic power 270 W, iron powder content 0.71%. The leaching efficiency of germanium is 95.19%, which is 5.79% higher than that of conventional leaching method. It was found that ultrasound can destroy the particle size, reduce the cluster structure of leached products by 13.5%, inhibit the agglomeration of particles, and promote the leaching of germanate and germanium sulphide. This study is of great significance for the production of germanium.

Simultaneous extraction of uranium and niobium from a low-grade natural betafite ore

Abstract This work efficiently investigated the simultaneous extraction of uranium (U) and niobium (Nb) from a low-grade natural betafite ore by using novel technique, namely, sulfatizing roasting coupled to sulfuric acid leaching process. First, the sulfatizing roasting was adopted to alert the properties of the raw ore, aiming to destroy the crystal structure of the ores and convert the valuable elements to soluble sulfate compounds. Moreover, the influences of the parameters affecting the sulfatizing roasting including roasting temperature, amount of sulfuric acid, and roasting time were studied. The results indicated that the extraction of U and Nb from the ores with sulfatizing roasting was an order of magnitude higher than the extraction of U and Nb from the ores without roasting under the same test conditions. Then, the effects of amount of sulfuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time on U and Nb recoveries were systematically investigated. To verify the process parameters of extracting U and Nb for the novel technique, three validating tests were conducted, and the results showed that over 95% of U and 85% of Nb were leached out under the optimal conditions. The novel technique was proven as advantageous since it conspicuously improved the leaching rates of U and Nb and promoted the refractory natural betafite ores to become an economic source for uranium.

Extraction of alumina and silica from high-silica bauxite by sintering with sodium carbonate followed by two-step leaching with water and sulfuric acid.

Efficient utilization of high-silica bauxite and minimization of bauxite residue are of great significance for the sustainable development of the alumina industry. In this paper, a novel process is proposed to extract Al2O3 and SiO2 from high-silica bauxite without residue discharge, that is, sintering bauxite with Na2CO3 followed by two-step leaching with water and sulfuric acid. The effects of the sintering parameters on the process were investigated, and the phase transformations during sintering and leaching were revealed by using phase diagram, thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) methods. When the mixture of the high-silica bauxite and Na2CO3 with mole ratio of Na2O/(Al2O3 + SiO2) of 1 was sintered at 950 °C for 30 min, diaspore and kaolinite were primarily converted into Na1.95Al1.95Si0.05O4 and an amorphous phase, respectively. In the water leaching process, Na1.95Al1.95Si0.05O4 was dissolved while the amorphous phase underwent some transformations to form the water leaching residue, resulting in ∼84% of Al2O3 being extracted for alumina production. In the sulfuric acid leaching process, the amorphous phase in the water leaching residue dissolved, resulting in ∼13% of Al2O3 and ∼86% of SiO2 being extracted for the production of polyaluminium ferric sulfate (PAFS) and silica gel, respectively. The silica gel had a high purity, containing more than 88% of SiO2 after drying.

Extraction of Molybdenum and Uranium from Low-Grade Molybdenum Bearing Ore Containing Uranium through Mechanical Activation Following Acid Leaching

ABSTRACT Extraction of molybdenum (Mo) from jordisite is difficult due to the amorphous state of MoS2. In this study, mechanical activation was employed to pretreat this type of ore with a low Mo content of 0.26%, and then molybdenum and uranium were both extracted from the milled ore using sulfuric acid. The effects of milling time, oxidant, and optimal leaching conditions were investigated in the laboratory. The results show that the mechanical activation will reduce the particle size and increase the specific surface area of the ore under certain milling conditions. Mechanical activation without oxidants in a hypoxia environment is not conductive to the recovery of molybdenum. When the oxidant of MnO2 is added during the milling process, the Mo recovery will increase greatly. The effect of mechanical activation on U recovery is not so obvious. The phenomenon of agglomerate will occur during the milling process, which will reduce Mo recovery seriously, especially when the milling time is more than 120 min. The Mo and U recovery can reach 84.52% and 61.39%, respectively, after optimization of sulfuric acid leaching process conditions.

Innovative application of two-stage sulfuric acid leaching for efficient recovery of Ti from titanium-bearing electric furnace slag

A two-stage sulfuric acid leaching process was developed to efficiently recover Ti from a titanium-bearing electric furnace slag (TEFS) made from V-Ti magnetite, which has a high content of impurities and low Ti content. The efficiency of the recovery mechanism was investigated. Anosovite and gangue minerals in the TEFS reacted with sulfuric acid and generated several solid substances such as TiOSO4, CaSO4, sulfates of Mg and Al, and silicate in the first-stage of the acidolysis, which formed the product layer and hindered the diffusion of sulfuric acid. Moreover, a high content of the impurities caused the gangue minerals to closely wrap around the anosovite, which hindered the acidolysis. By adopting a two-stage acid-leaching process, soluble sulfates, which are the most abundant product of acidolysis, were dissolved in water during the first-stage of the water leaching, which exposed the unreacted anosovite, diopside, and spinel. Accordingly, sulfuric acid completely reacted with the unreacted minerals during the second-stage acidolysis. The Si- and Ca-containing products of the acidolysis mainly existed in the form of silicate and CaSO4 and were later converted to silica gel and gypsum, respectively, after the second-stage water leaching. With this innovative process, the leaching rate of Ti improved significantly, achieving a 99.33% total leaching rate. Moreover, lowering the initial sulfuric acid concentration to 48% still yielded a total leaching rate of 98.04%, with the Ti grade of the final residue dropped to 3.14%.

Recovery of tungsten and titanium from spent SCR catalyst by sulfuric acid leaching process

The widespread use of selective catalytic reduction (SCR) catalysts has resulted in a large accumulation of spent SCR catalysts. These spent catalysts present a significant risk of environmental hazards and potential for resource recovery. This paper presents a feasible process, which works using atmospheric pressure leaching, of tungsten and titanium recovery from spent SCR catalysts. In this new method, titanium and tungsten are simultaneously leached with sulfuric acid as the leaching agent. After hydrolysis and calcination, titanium-tungsten powder with low impurity and reconstructed pore properties was obtained. The optimal conditions for the leaching of Ti and W were as follows: temperature, 150 °C; reaction time, 60 min; H2SO4 concentration, 80 %; mass ratio of H2SO4/TiO2, 3:1; and diluted H2SO4 concentration, 20 % after reaction. With these optimum conditions, the leaching efficiency of Ti and W were found to be 95.92 % and 93.83 %, respectively. The ion speciation and reaction mechanism of W were studied by Raman spectroscopy, FTIR, and UV–vis. The formation of heteropolytungstate with a Keggin structure is essential for the synergistic leaching of Ti and W, as the heteropolytungstate can be stably dissolved in the acid solution. During the hydrolysis process, heteropolytungstate gradually decomposed into Ti4+ and WO42− due to the formation of insoluble Ti(OH)4 from Ti4+ in the solution. This study demonstrated an effective method for synergistic recovery of titanium and tungsten from the spent SCR catalyst.

Cost-Effective and High Purity Valuable Metals Extraction from Water Leaching Solid Residues Obtained as a By-Product from Processing the Egyptian Boiler Ash

The water leaching solid residues (WLSR) obtained from salt-roasting Egyptian boiler ash are considered an essential secondary resource for (13%) nickel and (5.6%) zinc extraction. Hence, the current study aims for the cost-effective and high purity Ni, Zn, Fe and Mg metal ion extraction from (WLSR) using a sulfuric acid leaching process. The factors affecting the percentage recovery of Ni, Zn, Fe and Mg from WLSR, including leaching temperature, time, acid concentration and solid/liquid ratio, have been investigated. The obtained leaching solutions were analyzed chemically using ICP, and the different precipitates were analyzed mineralogically using XRD and EDX analysis and chemically using XRF. The maximum percentage recovery of Ni, Zn, Fe and Mg was 95.02%, 90.13%, 66.29% and 75.73%, which was obtained under the optimum leaching conditions of 8% H2SO4 concentration and 1/15 solid/liquid ratio at 85 °C for 240 min. The effect of pH, Fe2O3 dosage as nucleating agent and the precipitation duration on iron removal and Ni and Zn loss have been thoroughly studied. It has been found that >95% of the contained iron impurity can be removed, while nickel and zinc losses are around 4.2% and 3.8%, respectively. Additionally, a pH of 6 and 0.45 mol/L concentration of H2C2O4 was utilized to precipitate Mg as MgC2O4.2H2O, demonstrating that the precipitation efficiency of Mg reaches 96.9%. Nickel and zinc precipitation efficiency was 92.25% and 85.51%, respectively, by raising the solution pH to approximately 9. The kinetic of Ni and Zn dissolution has been investigated to explain the mechanism prevalent and the factors influencing the leaching process. It has been found that the nickel leaching kinetic is controlled by both diffusion through an inert porous layer and by chemical reaction with an activation energy of 20.25 kJ.mol−1. Meanwhile, the kinetic of zinc leaching is controlled by solid product layer diffusion with an activation energy of 11.67 kJ mol−1.

Comparison and evaluation of vanadium extraction from the calcification roasted vanadium slag with carbonation leaching and sulfuric acid leaching

Calcification roasting process for vanadium extraction has advantages in environmental protection, low cost of roasting additives, easy reutilization of the tailings. During the calcification roasting process, the vanadium spinel contained in the converter vanadium slag transforms into calcium vanadate. Carbonation leaching and sulfuric acid leaching used for extracting vanadium from the calcification roasted slag were compared and evaluated in detail, and effects of leaching parameters and the leaching kinetics were investigated. It was found that grinding the roasted slag particles below 94 μm can ensure a higher vanadium recovery. Leaching temperature, concentration of the ammonium carbonate, solid to liquid ratio all impacted the recovery of vanadium significantly. Under the conditions of temperature of 353 K, ammonium carbonate concentration of 200 g/L and solid to liquid ratio of 1:20 g/mL, 73.67% of the vanadium was extracted in 60 min. In the sulfuric acid leaching process, the aqueous pH value played a vital role and it was better to conduct the leaching at temperatures below 323 K. The sulfuric acid leaching reactions progressed fast and under a solid to liquid ratio of 1:10 the leaching efficiency of vanadium reached around 84% at 313 K and pH 2.50 in less than 30 min. Both leaching processes can be well described by the kinetic equation of 1/5(1 − α)−5/3 − 1/4(1 − α)-4/3 + 1/20 = kt, which represents the leaching process is controlled by diffusion of the two reactants in both directions. The difference lies in that the solid layer which the reactants pass through is mainly composed of silicate phases and Fe-rich phases in the ammonium carbonate leaching process, while in the sulfuric acid leaching process, calcium sulfate which instantaneously generates and tightly wraps the unreacted core, plays a dominant role in limiting the diffusion of the reactants. The ammonium carbonate leaching performs better in selectivity over the vanadium than the sulfuric acid leaching, but collection of ammonia and enrichment of vanadium-bearing solution should be considered..

Energy-efficient leaching process for preparation of aluminum sulfate and synergistic extraction of Li and Ga from circulating fluidized bed fly ash

ABSTRACT Sequential leaching and extraction of precious metals from high aluminum (Al) circulating fluidized bed (CFB) fly ash in China, which associated with lithium (Li) and gallium (Ga), is one of the most significant ways for value-added utilization. However, industrial application has been limited due to serious corrosion of equipment, significant energy consumption, and complex purification processes. To sufficiently leach valuable metals from CFB fly ash, a novel energy-efficient sulfuric acid (H2SO4) leaching process using dilution heat was developed, and the effects of iron (Fe) amount in the raw materials on the extraction process of Al, Li, and Ga as well as the as-prepared Al-based products were studied to efficiently obtain the qualified aluminum sulfate (Al2(SO4)3) products. The leaching behavior of each target element was systematically investigated by the laboratory and pilot-scale experiments. The extraction efficiencies for Al, Li, and Ga were 95.2%, 94.2%, and 87.7%, respectively, when the acid leaching process was conducted at the temperature of 140°C for 2 h, with the H2SO4 concentration of 40% and the solid-to-liquid ratio of 1/3, In the Pilot-scale experiment, the temperature of the reaction system can reach 120°C, 140°C, and 160°C by regulating the amount of H2SO4 added to release different heat, and efficient leaching of the target elements was achieved by the energy-efficient sulfuric acid leaching process. To obtain qualified Al2(SO4)3 products from fly ash, carbothermal reduction magnetic separation, and acid leaching were used for Fe removal from raw fly ash, and the Fe content in the as-prepared Al2(SO4)3 products was only 0.45% and 0.29%, which reached the standards of Class II qualified products and Class II first-grade products, respectively. This paper might provide an energy-efficient process for efficient and high-value utilization of solid waste fly ash.

A New Route to Upgrading the High-Phosphorus Oolitic Hematite Ore by Sodium Magnetization Roasting-Magnetic Separation-Acid and Alkaline Leaching Process

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P2O5 at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P2O5, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

Optimal Factor Evaluation for the Extraction of Alumina from Clays by Sulfuric Acid Leaching Process Using Box–Behnken Design Methodology

Optimal Factor Evaluation for the Extraction of Alumina from Clays by Sulfuric Acid Leaching Process Using Box–Behnken Design Methodology

Augmenting metal leaching from copper anode slime by sulfuric acid in the presence of manganese(IV) oxide and graphite

Copper anode slime (CAS) is a solid byproduct of copper electrorefining process, from which the recoveries of base metals (copper, nickel), high-value rare elements (tellurium, selenium) and precious metals (silver, gold) often witnessed problems because of the complexity of constituent phases in the slime. In the present study, a sulfuric acid leaching process in the presence of manganese(IV) oxide (MnO2) as oxidant and graphite as catalyst has been developed to augment metal recoveries from CAS. The leaching efficiencies of copper, nickel, tellurium, selenium and silver from CAS, and manganese from MnO2 achieved were 99.9%, 98.2%, 90.8%, 81.9%, 80.7%, and 84.1%, respectively, after leaching under the conditions: 2.0 M H2SO4 concentration, 90 °C temperature, 0.8/0.8/1 MnO2/graphite/CAS mass ratio and 6 h reaction time. These leaching efficiencies are higher than that in the absence of only graphite (99.8% Cu, 97.7% Ni, 76.8% Te, 69.4% Se, 67.2% Ag and 55.9% Mn), showing that graphite plays an important role to augment the leaching reactions. Negligible amount of Se and Ag leaching was noted without MnO2. The recyclability test of graphite showed that it can be recycled without loss of its catalytic performance. Thus, the process presented in this study shows good potential of sustainable metal recovery from CAS.

Study on Ultrasonically-Enhanced Sulfuric Acid Leaching of Nickel from Nickel-Containing Residue

In this paper, nickel-containing residue, a typical solid waste produced in the battery production process, was used to study the cavitation characteristics of ultrasonic waves in a liquid–solid reaction. The ultrasonically-enhanced leaching technology for multicomponent and complex nickel-containing residue was studied through systematic ultrasonic-conventional comparative experiments. An ultrasonic leaching kinetics model was established which provided reliable technological guidance and basic theory for the comprehensive utilization of nickel-containing residue. In the study, it was found that ultrasonically-enhanced leaching for 40 min obtained the same result as conventional leaching for 80 min, and the Ni extraction degree reached more than 95%. According to the kinetic fitting of the leaching process, it was found that the sulfuric acid leaching process belonged to the diffusion-controlled model of solid product layers under conventional and ultrasonic conditions, and the activation energy of the reaction was Ea1 = 17.74 kJ/mol and Ea2 = 5.04 kJ/mol, respectively.

Enhanced process route to remove fluorine and uranium from copper concentrades by selective sulfuric acid leaching

The main Cu-bearing mineral in copper concentrates consumed in smelters around the world is chalcopyrite (CuFeS2). Minor participation in this consumption is copper concentrates containing secondary copper minerals, such as chalcocite (Cu2S) and bornite (Cu5FeS4). The main issues concerning these copper concentrates are the amount of impurities, such as, fluoride and uranium. These impurities cause a lot of problems for smelters owners, such as equipment corrosion, gas treatment necessity and radionuclides residues generation, leading them to impose restrictions to buy fluoride and uranium copper concentrates. This study proposes a selective atmospheric sulfuric acid leaching process route to extract the maximum of fluoride and uranium and a minimum of copper from two types of copper concentrates, one having chalcocite/bornite as main Cu-bearing minerals, named as chalcocite/bornite concentrate, and another with chalcopyrite as the main Cu-bearing mineral, named as chalcopyrite concentrate. The results show that it is possible to reduce significantly the amount of fluoride and uranium in both samples. These two samples required the addition of sulfuric acid until reaching a pH of (3.5 ± 0.2), which means consumption of 23 kg and 9 kg of H2SO4 97.5 wt% per ton of chalcocite/bornite concentrate or chalcopyrite concentrate, respectively. The addition of aluminum sulfate increases the fluoride extraction, whereas it did not raise the uranium extraction. Chalcocite/bornite concentrate showed a slow kinetic to have fluoride leached, whereas chalcopyrite concentrate presented a fast kinetic to have uranium leached. It was possible to extract 60% of fluoride and 35% of uranium from chalcocite/bornite concentrate and around 10% of fluoride and 60% of uranium from chalcopyrite concentrate. As expected, the copper leached from chalcocite/bornite concentrate was higher (~4.5% of total Cu) than from chalcopyrite concentrate (~0.3% of total Cu). Moreover, it was proposed a complete process route to reduce the amount of fluoride and uranium comprising of acid leaching, copper recovery from the liquor by cementation with powder Fe and liquor treatment by raising the pH up to 9.0 by addition of calcium hydroxide pulp.