Leaching Parameters Research Articles

Production of rare-earth oxides from Eskişehir-Beylikova complex ores

In this study, the production technology of rare-earth oxides from Eskişehir-Beylikova complex ore that contains barite, fluorite, rare-earth elements, and thorium were investigated. In this study, processes that can be used in production of thorium-free mixed rare earth oxides were tested. Roasting, leaching, solvent extraction and precipitation methods were used in this study, respectively. Roasting temperature and roasting duration were determined as 600 °C and 1 hour, respectively. The optimum leaching parameters were determined as 5 M HCl, 1 hour leaching duration, 1/3 solid/liquid ratio and 35 °C leaching temperature. In the obtained leach liquor, Adogen was 464 used for removal of iron and D2EHPA was used for the removal of thorium. As a result of solvent extraction stuies, the solution containing rare earth elements was precipitated under optimum conditions. After precipitation, the product contains 99.65% rare earth oxides.

再生製品の溶出パラメータ取得のためのバッチ溶出試験における最適な撹拌条件の検討

再生製品の溶出パラメータ取得のためのバッチ溶出試験における最適な撹拌条件の検討

Application of the Response Surface Methodology to Optimise the Leaching Process and Recovery of Rare Earth Elements from Discard and Run of Mine Coal

The supply shortage of rare earth elements (REEs) for use in numerous high-tech applications has become an incentive for the prospecting of REEs from coal and coal discard. In this study, an optimised leaching process for the recovery of REEs from coal using the Design Expert (DOE) is reported. Response surface methodology (RSM) was used to investigate the effect and to determine the optimal leaching parameters for the two non-calcined coal samples. An optimised REE leaching recovery of 18.95% and 41.35% was obtained for the non-calcined Run-of-Mine (ROM) coal and discard coal, respectively. This optimised recovery was obtained as the HCl concentration increased from 0.5 M to 2 M, leaching temperature increased from 30 °C to 50 °C, whilst the solid:liquid ratio decreased from 40 g/L to 10 g/L. Statistical analysis indicated that the leaching parameters studied were important and controlled the REE leaching recovery model. Optimisation results also indicate that the calcined coals at 700 °C have the highest leaching recovery of 94.73% (ROM) and 98.17% (discard), respectively. Calcination also increased the concentration of REEs in the ROM sample from 225 ppm to 347 ppm and discarded the sample from 245 ppm to 363 ppm at 700 °C. Given the effect of the lixiviants investigated, the leaching efficiency of HClO4 for REE recovery was significantly lower than HCl and HNO3 under optimal leaching conditions. The discard coal used in this study had a significantly higher potential for REE recovery than ROM coal because it had a higher REE abundance and greater recovery.

Mechanochemically assisted persulfate activation for the facile recovery of metals from spent lithium ion batteries

A novel mechanochemically assisted persulfate activation method was proposed in this study to enhance the leaching of valuable metals from lithium-ion batteries by combining ball-milling, advanced oxidation processes and sucrose reduction. By optimizing leaching parameters including temperature, pH, milling time and solid-to-liquid ratio, high leaching efficiencies of 97.1%, 94.0%, 87.6% and 93.8% can be achieved for Li, Ni, Co and Mn respectively. In the mechanochemical process, the breakage of covalent bonds in cathode material is facilitated by free radicals generated from zero valent iron activated ammonia persulfate as well as mechanochemical activation. To further explore the role of free radicals, the mechanism of ammonia persulfate activation by zero valent iron was elucidated, and SO4•- was identified as the dominant reactive oxygen species in the mechanochemical process. Meanwhile, the synergistic effect of mechanochemically driven crystal dissolution and sulfate radical facilitated bond cleavage was revealed by ab initio molecular dynamics simulation. Moreover, the released metal was reduced by sucrose to a lower valent state of high solubility to promote transfer to the aqueous phase during the subsequent leaching process with dilute sulfuric acid. In this work, the insight on the mechanism of mechanochemical processes strengthened by free radicals may provide an inspiration for the recovery of valuable metals from LIBs.

Recovery Cu ad Ce from copper slag by using flotation and chemical methods

Slag, which is now considered as a secondary source, attracts attention due to the metallic values they contain. Copper slags having economical operating grades in terms of Zn, Cu, Ce, Ni, Co, Mo, and V show complex mineralogy due to its thermal processing history. Various methods for the recovery of copper and other precious metals from this byproduct have been studied, and there are many operating flotation plants in industrial scale. However, in cases where physical or physo-chemical mineral processing methods are not sufficient, hydrometallurgical methods are applied. In this study, flotation was applied to copper slag with 0.9% Cu grade. Copper recovery and concentrate grade were found as around 40 and 22.7% Cu, respectively. Further, metal extractions were examined by conducting direct leaching tests. Gel formation was observed, when H2SO4was used in the leach process, therefore, the leach parameters were investigated using HCl. Cu and Ce extractions of around 70-80% were reached as a result of a test performed for 2 hours with the addition of 25 g/L H2O2 at a rate of 20-25% solids and 300 g/L HCl concentration. When the relationship of dissolved metals with each other wasexamined, dissolution behavior of Cu and Ce was quite similar to Al dissolution (R2=0.9).

Production of synthetic rutile from tin ore beneficiation byproduct through preoxidation and reductive leaching in hydrochloric acid

This paper examines the effectiveness of the method for producing synthetic rutile from ilmenite through pre-oxidation and reductive leaching of pre-oxidized ilmenite in hydrochloric acid. Thermodynamic simulation of the pre-oxidation of ilmenite concentrate was performed to evaluate the phases formed during the process as a function of temperature. The pre-oxidation experiments were performed at different temperatures between 700 and 1000 °C in a muffle furnace for 6 h. The optimum temperature of pre-oxidation was revealed to be at 700 °C where ilmenite transformed into hematite and rutile, which is in accordance with the result of the thermodynamic simulation. Series of the leaching experiments were carried out under variations of HCl concentration (5–8 M), leaching temperature (70–100 °C), solid/liquid ratio (1/5–1/20 g/mL), ilmenite ore particle size distribution, and duration of leaching (6–12 h). Taguchi method utilizing L16 orthogonal array was adopted in the leaching step to design and reduce the required number of experiments. Analysis of variance (ANOVA) indicated that the temperature and solid/liquid (S/L) ratio were the most influential leaching parameters for the dissolution of iron and titanium. The optimum conditions for maximising the dissolution of iron, while minimizing the dissolution of titanium were at a temperature of 80 °C, HCl of 6 M, S/L ratio of 1/20 g/mL, ore particle size distribution of 44–77 µm (-200 + 325 mesh), and leaching duration of 6 h. The leaching experiment conducted under these conditions resulted in iron extraction of 98.07% with co-extraction of titanium of 11.35%. The leach-residue contains 92.6% rutile, 2.9% hematite, and 2.5% cassiterite which can be classified as synthetic grade rutile.

Priority recovery of lithium and effective leaching of nickel and cobalt from spent lithium-ion battery

The cathode materials of spent lithium-ion batteries (LIBs) were recovered via reductive roasting, Na2CO3 leaching, and ammonia leaching. The effects of roasting parameters, Na2CO3 leaching parameters, and ammonia leaching parameters on the leaching efficiencies of metals were explored. The results show that the mineral phase of spent LIBs is reconstructed during reductive roasting, and more than 99% of Li can be preferentially leached via Na2CO3 leaching. Ni (99.7%) and Co (99.9%) can be leached via one-step ammonia leaching, and Mn cannot be leached. Thus, good leaching selectivity is achieved. The kinetic study shows that the leaching of Ni and Co conforms to chemical reaction control.

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.

Novel GO/Fe-Mn hybrid for the adsorptive removal of Pb(II) ions from aqueous solution and the spent adsorbent disposability in cement mix: compressive properties and leachability study for circular economy benefits.

GO/Fe-Mn hybrids were prepared by a single-pot chemical precipitation method and were characterized using FTIR, XRD, Raman, zeta potential, and FESEM, which confirmed the impregnation of Fe/Mn onto GO sheets. The synthesized hybrids were successively applied in removing the Pb(II) ions from aqueous solution and later utilizing the spent adsorbent to increase the properties of cement. The adsorption capability of the synthesized hybrid was seen in a set of batch studies to find out that about 15min of contact time was required to remove 99% of the contaminant at a pH of 5 ± 0.2 and a dose of 0.83g/L. The mechanism of the adsorption process for the synthesized hybrid was well described by Elovich kinetic model with an R2 of 0.99 and Langmuir isotherm model, also with an R2 of 0.99. The desorption studies conducted using 0.1M HCl solution showed significant stability of the hybrid with a drop of 12% in the removal efficiency of Pb after up to five adsorption-desorption cycles. This points to an efficient adsorbent having potential for economical use. Later, the spent adsorbent was mixed with cement at ratios of 0.05%, 0.1%, and 0.5%, and compressive strength tests were performed, which showed an increase in the strength by 7.62%, 16.11%, and 26.82% at 28days of curing time. The TCLP and SPLP tests performed on the hybrid and cement-spent adsorbent mix showed all the leaching parameters were well within the permissible limits. This development shows the potential for the use of spent adsorbent in a circular economy model.

Effect of organic and inorganic compounds on dissolution kinetics of chalcopyrite in hydrogen peroxide– Hydrochloric acid system

The addition of 2-Propanol as an organic substance and NaCl as an inorganic compound in hydrochloric acid with hydrogen peroxide as a strong leaching agent of chalcopyrite was investigated. The effects of the leaching parameters on copper extraction, such as stirring speed, H2O2 concentration, temperature, HCl concentration and solid/liquid ratio were studied. The maximum final copper extraction of 54.55% was obtained with 600 rpm stirring speed, 1.5 M H2O2, 0.5 M HCl, 600 rpm, 50 °C, 240 min of the reaction and particle size of −106 +75 µm. Further experiments were performed when the solid-to-liquid ratio (S/L), stirring speed, temperature, HCl, H2O2 and leaching time were kept constant to examine the influence of NaCl and 2-Propanol concentrations in the range of 0–0.5 M and 0–3 M, respectively. The results showed that the copper extraction was increased up to 58.11% with addition of NaCl. While copper extraction yield reached 94.25% in case of addition of 2-propanol with the optimum parameters(0.5 M HCl,50 °C, 1.5 M H2O2, 600 rpm, particle size −106 +75 μm, solid liquid ratio 2g/L, 3 M 2-propanol). The chalcopyrite leaching in hydrogen peroxide– hydrochloric acid system was found to be described by the interface transfer and diffusion across the product layer with activation energy of 77.14 kJ/mol. Addition of 2-propanol suggested that the reaction was under product layer diffusion control and decreased the activation energy of chalcopyrite leaching to 67.98 kJ/mol.

Gold leaching from waste mobile phone PCBs in a solution mixture of sodium persulfate and potassium iodide

Gold is one of the most fascinating resources in the waste mobile phones’ printed circuit boards (WMPPCBs). In this study, a new process for recovering Au from WMPPCBs by the Na2S2O8-KI system was developed. This process comprises a two-stage leaching process to provide a separation of copper and gold from WMPPCBs. 98% Cu and 78% Fe were dissolved by the 1st base metals' leaching (H2SO4-H2O2 leaching) step. The leaching of gold from the solid reside of 2nd leaching step was performed to study the effect of Na2S2O8 concentration, KI concentration, temperature, and solid-liquid ratio in Na2S2O8-KI leaching system. The results showed that removing most of Cu greatly promoted the leaching efficiency of gold in Na2S2O8-KI leaching system. The mechanism of gold leaching was studied by the thermodynamic analysis. Leaching kinetics data showed that gold leaching followed an intermediate-controlled mechanism with Ea, 30.3 kJ mol−1. The best conditions for leaching of gold in Na2S2O8-KI system were determined to be 0.02 M Na2S2O8, 0.15 M KI, 40 ℃, a solid-liquid ratio of 1: 20 (g/mL), and a stirring speed of 200 rpm. Under the optimal leaching parameters, the efficiency of gold leaching from WMPPCBs attained 96% after 120 min. Due to the non-toxic and low-cost properties of Na2S2O8, the Na2S2O8-KI leaching process is more sustainable than conventional processes (cyanide leaching et al.).

Inversion Analysis of Impervious Curtain Permeability Coefficient Using Calcium Leaching Model, Extreme Learning Machine, and Optimization Algorithms

The calcium leaching effect leads to a decrease in the impermeability of the impervious curtain. The inverse analysis strategy was introduced in this study because the calcium leaching parameters of the curtain are not easy to determine. An orthogonal design and the finite element method were used in the strategy. The time-series data of hydraulic head and leakage volume were applied to construct the objective function. The extreme learning machine (ELM) was proposed to build the reflection sets. Genetic algorithm (GA), simulated annealing (SA), sparrow search algorithm (SSA), and particle swarm optimization (PSO) were employed to accelerate the iterative search for the target parameters. The target parameters of the calcium leaching model were used for finite element verification by comparing the monitored and simulated values. The simulated values of hydraulic head and leakage by PSO show good agreement with measurements. The evolution of the curtain permeability coefficient in 100 years was analyzed. The results demonstrate the strategy’s feasibility in determining the curtain’s calcium leaching parameters and permeability coefficients.

Experimental and statistical modelling on copper recovery from low-grade mixed sulphide-oxide ore by direct leaching

ABSTRACT This study aims to investigate the recovery of copper from a low-grade source of an ore deposit in sulphuric acid solution. In this study, a full-factorial statistical design model and Artificial Neural Networks (ANN) are applied to develop an analytical approach to understand the dissolution parameters better. Temperature, time, particle size, and acid concentration were selected as the leaching parameters. The experimental design set by the full-factorial model was again trained with the ANN model to compare the predicted results. The correlation coefficients (R2) in both the models are 0.9962 and 0.99815, respectively, indicating both the models offered a well-aligned explanation for the variability of the experimental values to the predicted values. Therefore, the outcome of this study demonstrates that the proposed design model results are well-aligned with the experimental results, and 88% of copper metal can be recovered at a condition of 120 minutes, 90°C temperature, the particle size of -75 + 63 µm, and acid concentration of 1M.

Kinetics and mechanisms of leaching of rare earth elements from secondary resources

The study of the kinetics of REEs from secondary resources and the understanding of the mechanisms governing the leaching reactions are fundamental aspects for the design and the optimization of industrial processes. Despite their interest, the kinetic aspect of these valuable elements from secondary resources has not been reviewed yet. Therefore, a deep understanding of the major phenomena involved in the elementary stages of REEs leaching is extremely crucial and would allow setting up a comprehensive methodology for kinetics investigation. This review provides a state of the art on various kinetics approaches describing the leaching kinetics and mechanisms of REEs from secondary resources notably low-grade minerals, industrial residues as well as end-of-life products. Different existing kinetics models applied for the leaching were reviewed and deeply discussed. Meanwhile, comparative study of different leaching mechanisms was also realized for a better understanding of the REEs leaching reactions. More importantly, the effect of different leaching parameters on the kinetics was discussed for further optimization and development of REEs extraction processes from secondary resources. In addition, the comparison of different REEs secondary resources was provided in terms of content, availability and economic opportunities to target the most potentially and economically viable resources.

Development of Kinetic Parameters for Nitric Acid Leaching of Phlogopite and the Characterization of Solid Products

AbstractSouth Africa is a net importer of fertilizer products, importing all of its potassium, as well as 60–70% of its nitrogen requirements. Thus, domestic prices are impacted significantly by international prices, shipping costs, and exchange rates. Producing these fertilizers locally would be far more economical. Phlogopite, a rich source of potassium, is discarded in large quantities during mining operations; the objective of the present study, therefore, was to determine the acid-leaching characteristics and behavior of phlogopite as a means of releasing potassium. Phlogopite samples were leached with nitric acid (source of nitrogen for fertilizers) at various concentrations, temperatures, and reaction times. The feed phlogopite and leached residue samples corresponding to conversions of 14% (LP1), 44% (LP2), and 100% (LP3) were collected and analyzed using X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer–Emmett–Teller surface area and porosity analysis (BET), thermogravimetric analysis (TGA), and field emission gun-scanning electron microscopy (FEG-SEM). The feed phlogopite was highly crystalline. The absence of defects in the lattice meant that the motion of H+ atoms penetrating into the lattice was restricted, suggesting internal diffusion-controlled leaching. Furthermore, results obtained from the various analytical techniques corroborated each other in terms of the release of cations during leaching. All leaching experiments were conducted batchwise, in a closed system. The gravimetric data from the experiments were used to identify a suitable model which predicts accurately the leaching behavior. The reaction was found to be internal diffusion-controlled, and the D1 model, which represents one-dimensional diffusion through a flat plate, predicts the leaching behavior most accurately. The observed activation energies (Ea) and pre-exponential constants (k0) varied with initial nitric acid concentration ([H+]0).

Effect of ilmenite properties on synthetic rutile quality

Ilmenite (TiO2 > 52%) can be upgraded to synthetic rutile (TiO2 > 88%) using a reduction and leaching process. Australian ilmenites (FeTiO3) contain variable amounts of titanium dioxide, iron oxide and other impurities. Ilmenites from different deposits can have different physical and chemical properties that affect ilmenite reduction and the final TiO2 content in synthetic rutile (SR). The main aim of this study was to characterise feed ilmenites using a wide range of traditional and advanced analytical techniques and to determine the effects of feed properties on the quality of the SR. Three different ilmenite samples were upgraded to SR using a comparable ilmenite to coal ratio, heating rate, reduction temperature, holding time, cooling temperature and acid leaching parameters. Differential scanning calorimetry, thermogravimetric analysis, Brunauer–Emmett–Teller (BET) surface analysis and sizing analysis data indicated a difference in physical and surface properties among the samples. Head samples had a TiO2 content between 60% and 65% and Fe2O3 content between 25% and 34%. XRF assay by size data confirmed a variation in the content of TiO2, Fe2O3 and impurities among different size fractions. XRD phase analysis indicated the samples were composed of ilmenite, pseudorutile and rutile. SEM morphology studies revealed that ilmenite particle shapes were sub-angular, sub-rounded or rounded. The study found a linear relationship between the metallisation as a result of processing and feed BET surface area. Feed ilmenites with higher BET surface area and fewer impurities resulted in higher SR quality.

Optimizing the Leaching Parameters and Studying the Kinetics of Copper Recovery from Waste Printed Circuit Boards.

The study of copper (Cu) recovery is crucial for the entire recovery process of waste printed circuit boards (WPCBs), and Cu can be leached efficiently via a sulfuric acid–hydrogen peroxide (H2SO4–H2O2) system. To achieve high Cu recovery, it is important to evaluate the parameters of the leaching process and understand the Cu leaching kinetics. Applying statistical and mathematical techniques to the leaching process will further benefit the optimization of the Cu leaching parameters. Moreover, the leaching kinetics of Cu in the H2SO4–H2O2 solution is yet to be fully understood. Hence, in the present work, process parameters, such as temperature, H2SO4 and H2O2 concentrations, solid–liquid ratio, particle size, and stirring speed, were optimized statistically by the response surface methodology (RSM). The results showed that the leaching kinetics conformed to the Avrami model. The maximum Cu leaching efficiency was 99.47%, and it was obtained based on the following optimal conditions: 30.98 °C, 2.6 mol/L H2SO4, 1.87 mol/L H2O2, a solid–liquid ratio of 0.05 g/mL, 135 mesh, and 378 rpm. RSM was used for the optimization of the process parameters, and the leaching kinetics in this system was clarified. This study provides an important pathway for the investigation of other metal recoveries from WPCBs.

Biodissolution of metal values from complex sulfides using sulfur-oxidizing bacteria

Bioleaching of a complex sulfide sample was carried out using an acidophilic microorganism namely sulfur-oxidizing bacteria (SOB). Various leaching parameters like initial pH, elemental sulfur, and pulp density were varied in order to evaluate their significance on the bioleaching process. The evaluation was based on the dissolution of elements like copper, zinc, iron, and sulfur present in the complex sulfide sample. All three leaching parameters significantly affected the biodissolution rate of the above elements. The SOB could able to leach 22.2, 33.9, 27.1 and 50.2 %(w/w) of copper, zinc, iron, and sulfur, respectively, at the optimum condition of elemental sulfur, 8 g/L; initial pH, 2.0; and pulp density, 10 %(w/v). The equilibrium contact time of the bioleaching was found to be 25 days. The biodissolution rate of zinc and sulfur was found to be more than that of copper and iron. The leaching rate increased with the increase of elemental sulfur addition and it decreased with the increase of pulp density. However, it increased with the increase of pH from 1.5 to 2.0 and decreased upon further increase of pH due to the maximum bacterial activity at pH 2.0.

Влияние различных реагентов на эффективность подземного скважинного выщелачивания урана из руд Хиагдинского месторождения

To ensure Russia's energy security, it is necessary to produce cheap electricity. One of the directions of domestic energy development is its production at nuclear power plants. The source of raw materials for powering nuclear reactors is natural uranium extracted from rocky and hydrogenic (localized in loose sediments) deposits. Hydrogenic deposits have been explored in Transbaikalia, united into a single Khiagdin ore field and characterized by identical mining-geological, hydrogeological and technological parameters. During the operation, certain difficulties have been identified in the extraction of natural uranium, related both to the geological structure of the deposits and the temperature regime of groundwater, and to the economic performance of the enterprise. As a result of the confluence of these circumstances, the issue of transferring uranium to a mobile state during underground borehole leaching with the necessary dynamics that ensures the concentration of uranium in a productive solution, the processing of which will produce profitable mining enterprise products, is problematic. This article is devoted to the intensification of the leaching process using chemical activators that accelerate the conversion of uranium into a productive solution The relevance of the work is due to the need to activate the process of uranium leaching with the help of underground borehole leaching to ensure a more complete recovery of uranium and to reduce the period of field development with the use of chemical oxidants. The object of the study is technological processes of underground in-situ leaching with the use of chemical activators. The purpose of the study is improving the development efficiency of hydrogenous uranium deposits, reducing operating costs. The research objectives are to identify the most effective oxidants and regimes of their use, increasing the volume of uranium recovery in the productive solution. The research methodology included collecting information, its mathematical and statistical processing, carrying out research work and establishing a connection between mining-geological, hydrogeological and technological parameters of ore leaching. Research methods: mathematical and statistical analysis, laboratory research and the use of the results for experimental and industrial works

A study of copper leaching from the tailings of the Karagaily (Republic of Kazakhstan) concentrating factory using an electric hydropulse discharge

The method for using concentration plants tailings is proposed for the first time in this study. These tailings contain a number of valuable metals, such as Cu, Fe, Zn, etc., and are a potential raw material for obtaining concentrates of some elements. An electrohydropulse discharge was used to intensify the process of copper leaching and other metals. Ammonium bifluoride, the most effective of the ammonium salts used in copper leaching by the ammonization method, was chosen as the reagent. The influences of significant leaching parameters were studied and optimized using probabilistic deterministic planning of experiment. Based on the study findings, the following process conditions were found to be optimal: mass ratio of solid to liquid (S:L) of 1:1; Cu:F = 1:6; sulphuric acid concentration 40 g L-1; experiment duration 30 min; discharge voltage 10 kV and a leaching efficiency of 80-85 % could be achieved. Comparative features of tailings samples from the Karagaily (Republic of Kazakhstan) concentration plant were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic emission spectral analysis. The study results showed that copper was maximally transferred to the aqueous phase.