Leaching Of Impurities Research Articles

Process and mechanism for synergistic treatment of spent carbon cathode and red mud by hydrothermal acid-leaching

Spent carbon cathode (SCC) and red mud (RM) are two kinds of solid wastes that are harmful to the environment and rich in valuable components from the aluminum industry. In this study, the valuable components of SCC and RM are co-treated by the hydrothermal acid-leaching. The synergistic treatment process is analyzed by phase characterization, thermodynamic calculation, single factor experiment, orthogonal experiment and kinetic study. The results show that the leaching of impurities by the synergistic treatment is better than that of hydrothermal acid-leaching alone. Under the optimal leaching conditions (liquid–solid ratio of 25 mL/g, temperature of 453 K, time of 270 min and acid concentration of 4 mol/L), the leaching efficiency of aluminum and iron reaches 89.70 % and 87.91 %, respectively. For aluminum, the time is the key factor affecting its leaching, the activation energy is 21.52 kJ/mol, and the leaching process is controlled by chemical reaction and solid product layer diffusion. For iron, the acid concentration is the key factor affecting its leaching, the activation energy is 2.82 kJ/mol, and the leaching process is controlled by the solid product layer diffusion. The leaching residue obtain by synergistic hydrothermal acid-leaching is C and SiO2. This process provides a new solution for the treatment and recovery of SCC and RM.

Desorption behavior and mechanism of yttrium ions from ion-adsorption type rare earths ore

Ion-adsorption type rare earths ore (IREO) is an important strategic resource that can be leached in-situ using electrolytes such as NH4+, Mg2+, and Al3+. However, the use of NH4+ was restricted due to ammonia-nitrogen pollution, regarding in-situ leaching agents still remain controversial. It is imperative to comprehensively and systematically investigate the desorption mechanism of rare earth elements (REEs) from a microscopic perspective, especially when using Mg2+ and Al3+ as leaching agents. In this manuscript, the desorption behavior and mechanism of Y3+ from ADY (IREO as adsorbents loaded with Y3+) were studied, along with a comparison of the Y3+ desorption capabilities of Mg2+ and Al3+ as leaching agents. The results showed that Y3+ could be effectively desorbed from IREO by both Mg2+ and Al3+, with Y3+ desorption yields of 93.1 % (pH 3.2, 0.06 mol/L) for Al3+ and 88.6 % (pH 6.0, 0.3 mol/L) for Mg2+, respectively. The superior Y3+ desorption capability of Al3+ arises from its higher valence, greater electronegativity, and smaller ionic radius compared to Mg2+. The higher valence imparts Al3+ greater charge density, while the greater electronegativity enables Al3+ to more readily substitute for Y3+. Additionally, the smaller ionic radius facilitates the entry of Al3+ into clay minerals interlayers. At high H+ concentrations, the Y3+ desorption capabilities of Mg2+ and Al3+ were both higher than at the original pH without acid addition, primarily due to the influence of H+, which could leach Y3+ from the un-exchangeable phase, but also significantly increased the leaching of impurities. The isotherms and kinetics demonstrated the desorption of Y3+ in the case of Mg2+ and Al3+ existing followed the Langmuir and pseudo-second-order models, indicating homogeneous, chemisorption-governed processes. Furthermore, ATR-FTIR, XPS, and DFT results revealed Y3+ desorption occurred by breaking SiOY bonds and ion exchange with Mg2+/Al3+ to form SiOMg/Al bonds.

Hydrometallurgical refining of metallurgical silicon

The paper presents the results of refining silicon of metallurgical grades based on leaching of impurities with inorganic acids. Silicon samples were studied by metallographic and X-ray fluorescent methods of analysis, as well as X-ray spectral microanalysis. To improve the quality of this alloying element, we carried out experimental work on its hydrometallurgical purification with solutions of various acids (10 % H2SO4 , HCl, HNO3 , 4 % HF) and their mixtures. Values of changes in the Gibbs energy were calculated for reactions of interaction with reagents of the main impurity inclusions recorded in the studied silicon samples (FeSi2 , Fe2Si, FeSi, AlFeSi, AlFeSi2 , Al3FeSi2 , FeSi2Ti, FeAlTiSi, TiSi2 , Ca2Si). The experiments were carried out on silicon samples with a particle size of –200 μm with constant stirring by a magnetic stirrer at a temperature of 60 °С, duration 1 h and L:S = 5:1. Determination of concentration of the impurity elements in the solution after leaching was made by the atomic emission method of analysis. When hydrofluoric acid is used as a solvent, the best results are obtained for purification of iron, aluminum, and titanium (concentration in solution, mg/dm3, respectively: 2380, 831, 145). The maximum concentration of calcium in the solution (147 mg/dm3 ) was achieved by hydrochloric acid treatment of fine silicon. The most effective for transferring impurities into solution is a mixture of sulfuric and hydrofluoric acids at a ratio of 1:1. Using a mixture of H2SO4 and HCl as a solvent (at a ratio of 1:3) made it possible to achieve sufficiently high mass concentrations of impurity elements in the leaching solution. The degree of silicon purification from iron was 33.32 %, aluminum – 54.64 %, calcium – 65.77 %, titanium – 15.64 %.

Leaching Behavior of the Main Metals from Copper Anode Slime during the Pretreatment Stage of the Kaldor Furnace Smelting Process

The Kaldor furnace smelting process is currently the mainstream process for treating copper anode slime, but the existence of copper, tellurium and other impurities has adverse effects on the recovery of gold and silver during the Kaldor furnace smelting stage. Therefore, it is necessary to pretreat the copper anode slime to remove these impurities before Kaldor furnace reduction smelting. However, the current pretreatment process of copper anode slime generally has the problem of low removal efficiency of copper and tellurium, and little research on the occurrence state of main metals in copper anode slime. Therefore, this study quantitatively determined the phase composition of Cu, Te, Pb, Bi, As, Sb, Se, Ag and Au, and hydrogen peroxide was introduced to enhance the leaching of impurities. The leaching behavior of each metal in copper anode slime was investigated in detail. The results demonstrate that Cu and Te in the copper anode slime mainly exist in the form of CuO and CuSO4 and Te and AuTe2, respectively. More than 99% of the Cu and 97% of the Te were leached out using 250 g/L H2SO4 and 28.8 g/L H2O2 with a leaching pressure of 0.8 MPa at 150 °C for 2 h, while the leaching of Au and Ag was both < 0.03%. The removal of Cu and Te and the enrichment of precious metals were achieved. This study provides a rich theoretical reference for the optimization of the Kaldor furnace process.

Analysis of the Process of Mineral Sequestration of CO2 with the Use of Fluidised Bed Combustion (FBC) Fly Ashes

There is a current focus on replacing the generally accepted conventional power generation technologies with more advanced ones that will better protect the natural environment. The need to limit CO2 emissions from power generation plants presents a problem that must be solved in many countries that use coal or lignite as basic fuels. One potential option is mineral sequestration performed using side products of fossil fuel combustion, such as fluidised bed combustion (FBC) fly ashes. Fluidised bed combustion (FBC) lignite fly ashes are characterised by a high storage capacity of 15.7%. Research conducted with the most commonly used method of direct mineral sequestration—CO2 trapping with fluidised bed combustion (FBC) ash in water suspension—has indicated a very high level of carbonation of CO2, reaching 11%. Calcite was the basic product of carbonation. The calcite content increased from 2% to 12% in the suspension subjected to treatment with CO2. Furthermore, CO2 reduced the pH and limited the leaching of impurities, such as Zn, Cu, Pb, Ni, As, Hg, Cd, Cr, Cl, and SO4. The fly ash suspensions subjected to CO2 treatment can be used in industry in the final stage of carbon capture and utilisation (CCU) technology, which will further contribute to the implementation of the circular economy.

Gold in the Oxidized Ores of the Olympiada Deposit (Eastern Siberia, Russia)

Native gold and its satellite minerals were studied throughout the 300 m section of oxidized ores of the Olympiada deposit (Eastern Siberia, Russia). Three zones are identified in the studied section: Upper Zone ~60 g/t Au; Middle Zone ~3 g/t Au; Lower Zone ~20 g/t Au. Supergene and hypogene native gold have been found in these zones. Supergene gold crystals (~1 μm), their aggregates and their globules (100 nm to 1 μm) predominate in the Upper and less in Middle Zone. Relic hypogene gold particles (flattened, fracture and irregular morphology) are sporadically distributed throughout the section. Spongiform gold occurs in the Lower Zone at the boundary with the bedrock, as well as in the bedrock. This gold formed in the process of oxidation of aurostibite, leaching of impurities and its further dissolution. Hypogene gold is commonly isolated but for supergene gold typically associated with ferric (hydr)oxides. New formation of gold occurred due to oxidation of sulfide ores and release of “invisible” gold, as well as dissolution, mobilization and re-deposition of metallic hypogene gold. A model for the formation of oxidized ores with the participation of meteoric and low-temperature hydrothermal waters has been proposed.

Гидрохимическая очистка золотосодержащих катодных осадков от примесей тяжелых цветных металлов

The purpose of this paper is to conduct the research on hydrochloric acid cleaning of gold-containing cathode deposits from the impurities of heavy non-ferrous metals and mathematical processing of the experimental data obtained by the method of dispersion analysis. The atomic absorption method is used to study the chemical composition of the cathode deposits. The method of dispersion analysis is used to process experimental data. The composition of cathode deposit impurities is studied using x-ray spectral microanalysis. The study of the chemical composition of cathode deposits has shown that their main components are gold, silver, copper, lead, as well as non-metallic impurity compounds (CaO, SiO2, etc.). It is found that the optimal concentration of hydrochloric acid for cleaning gold-containing cathode deposits from heavy non-ferrous metals is 371 kg/m3; the degree of copper transition to solution is 69.06%, lead - 93.9%. The calculation of the expected mass fraction of precious metals in the alloyed gold demonstrates an increase in the mass fraction of gold by 14.08%, silver - by 17.46%. The study of the chemical composition of cathode deposits has also revealed that the main impurities that affect their subsequent processing are copper and lead. The latter fall into the ingot of alloyed gold, which is the target product of gold-bearing ore processing and complicate subsequent refining. The dispersion analysis of experimental data shows that solvent concentration significantly affects the transition degree of heavy non-ferrous metals to the solution starting from the value of 20.1 kg/m3. It is shown that the proposed method allows to increase the content of precious metals in the alloyed gold by 31.54%, as well as to perform maximum transition of copper and lead to the solution. The use of acid leaching of impurities from cathode deposits obtained by cyanide-sorption technology is one of the promising directions for improving the quality of gold-containing alloys and hence the reduction of the cost of refining services.

Leaching Behaviors of Impurities in Titanium-Bearing Electric Furnace Slag in Sulfuric Acid

Titanium-bearing electric furnace slag (TEFS) was prepared from vanadium titanomagnetite and leached with sulfuric acid. The Ti leaching rate of vanadium titanomagnetite TEFS is significantly lower than that of ilmenite TEFS. The impurity content in vanadium titanomagnetite TEFS is higher than that in ilmenite TEFS. This might be one of the main factors resulting in the low leaching rate of Ti, so the leaching behaviors of various impurities under different conditions (temperature, acid/solid weight ratio, particle size, and initial sulfuric acid concentration) were investigated. The following trends were observed under different leaching conditions: The leaching rate of Fe increased rapidly and reached equilibrium quickly, that of Si increased quickly in the early stage and then decreased in the later stage, that of Ca increased initially and reached equilibrium later, and the leaching rates of Mg and Al increased gradually until the equilibrium was reached. The leaching rate of Fe was too rapid to be able to investigate its leaching kinetics, and the insoluble leached products of Si and Ca interfered with their leaching. The effects of leaching parameters on the leaching of impurities were further analyzed by X-ray diffraction (XRD) and scanning electron microscopy analysis. XRD data indicated that spinel is the major Mg- and Al-bearing mineral in TEFS. Mg and Al showed similar leaching behaviors, and their leaching conformed to a new model based on interface transfer and diffusion across the product layer, both of which affect the leaching rate.

Сернокислотное выщелачивание меди и свинца из золотосодержащих катодных осадков

The purpose of the paper is to study the chemical composition of cathode deposits obtained at gold-bearing ore processing by the cyanide-sorption technology; to conduct experimental studies of the sulfuric acid leaching of copper and lead from gold-bearing cathode deposits; to consider the effect of sulfuric acid concentration on the transition degree of copper and lead into solution. Mathematical processing of experimental data is performed by the correlation method. Chemical composition of the cathode deposits is studied by the atomic absorption analysis and X-ray spectral microanalysis. Having studied the chemical composition of the cathode deposits the main impurities influencing their further refining is identified. They are copper and lead, which should be removed before the following production of base gold bullion. The results of the experimental studies on sulfuric acid treatment of cathode deposits are as follows: the transition degree of copper into solution is 45.98%, lead - 3.65%, the optimal concentration of sulfuric acid is 165.4 kg/m 3 . The results of sulfuric acid leaching of impurities from the cathode deposits appears to be of low efficiency as lead can not be extracted into the solution due to the passivation of its surface with PbSO 4 film. The mathematical processing of experimental data by the correlation analysis has showed that the concentration of sulfuric acid affects the degree of copper and lead transition into the solution.

Leaching Process and Mechanism of Weathered Crust Elution-Deposited Rare Earth Ore

The leaching processes and mechanisms of weathered crust elution-deposited rare earth (RE) ores with ammonium sulfate were investigated for their high efficiency and low consumption exploitation. The leaching process is a typical reversible heterogeneous ion exchange reaction in liquid–solid systems. The raw ore and leached tailings were analyzed by SEM and FTIR. Results indicated that no dissolution or structural changes of the ores occurred during the leaching process. The migrations of RE3+, Al3+, and $$ {\mathrm{NH}}_4^{+} $$ in the leaching process were studied under various liquid–solid ratios. With increasing liquid–solid ratio, the content of $$ {\mathrm{NH}}_4^{+} $$ adsorbed on clay mineral by physical effect decreased, $$ {\mathrm{NH}}_4^{+} $$ adsorbed by ion-exchange increased, and the content of exchanged RE and Al increased until reaching equilibrium. The adsorption capacity of the RE ores for $$ {\mathrm{NH}}_4^{+} $$ remained about 0.61–0.63 mg/g. It was difficult to desorb $$ {\mathrm{NH}}_4^{+} $$ from RE ores with washing water alone. The leaching mechanism of Al was the same as RE, but the leaching of Al slightly lagged behind RE. At the optimal liquid–solid ratio of 0.4:1, the leaching efficiencies of RE and Al were 95.51% and 90.99%, respectively, and 56.65% of $$ {\mathrm{NH}}_4^{+} $$ remained in the leachate. After impurity removal and RE precipitation, the leachate can be reused by replenishing fresh leaching agent. The aim of this study is to enhance the leaching process of RE, restrain the leaching of impurities, and decrease the consumption of leaching agents.

Waste-Free Recycling of Secondary Bacor Resources1

Technology is developed for two-stage processing of secondary zirconium-containing mineral resource. A production scheme includes mechanical treatment of bacor waste and subsequent chemical leaching of impurities. The main processes in the first (mechanical) stage are crushing and selective grinding with separation of high-zircon concentrate (Al2O3–ZrO2 system) and aluminum-zirconia product leaner with respect to ZrO2 (R 2O–Al2O3–ZrO2–SiO2 system). In the second stage the latter are leached with a fluoric acid solution. The waste-free technology proposed for enrichment makes it possible to use valuable secondary resources entirely with preparation of two end products: enriched bacor refractory and a slag-forming mixture for steel smelting production.

A research on acid leaching of impurities from gold-containing cathode sediments

A research on acid leaching of impurities from gold-containing cathode sediments

ZERO-WASTE RECYCLING OF THE SECONDARY BACOR MATERIALS

The two-stage processing for the secondary zirconiumcontaining mineral raw materials was developed in the article. The process flow sheet includes both the Bacor scrap mechanical treatment and the subsequent chemical leaching of impurities. The main processes of the first (mechanical) stage are the crushing and selection extraction of the high-zirconium concentrate (Al2O3‒ZrO2 system) and more poor in ZrO2 alumina-zirconium product (R2O‒Al2O3‒ZrO2‒SiO2 system). At the second stage this product is leached by means of the hydrogen fluoride water solution. The zero waste enrichment technology proposed allows the full utilization of the valuable secondary raw materials with the two resulting products: the concentrated refractory Bacor and the slag-forming mixture for the steel making industry. Ill. 1. Ref. 6.

Leaching of Metal Ions from Blast Furnace Slag by Using Aqua Regia for CO2 Mineralization

Blast furnace slag (BFS) was selected as the source of Ca for CO2 mineralization purposes to store CO2 as CaCO3. BFS was dissolved using aqua regia (AR) for leaching metal ions for CO2 mineralization and rejecting metal ions that were not useful to obtain pure CaCO3 (as confirmed by XRD analysis). The AR concentration, as well as the weight of BFS in an AR solution, was varied. Increasing the AR concentration resulted in increased metal ion leaching efficiencies. An optimum concentration of 20% AR was required for completely leaching Ca and Mg for a chemical reaction with CO2 and for suppressing the leaching of impurities for the production of high-purity carbonate minerals. Increasing the liquid-to-solid ratio (L/S) resulted in the increased leaching of all metal ions. An optimum L/S of 0.3/0.03 (=10) was required for completely leaching alkaline-earth metal ions for CO2 mineralization and for retaining other metal ions in the filtered residue. Moreover, the filtrate obtained using 20% AR and an L/S of 0.3/0.03 was utilized as Ca sources for forming carbonate minerals by CO2 mineralization, affording CaCO3. The results obtained herein demonstrated the feasibility of the use of AR, as well as increasing pH, for the storage of CO2 as high-purity CaCO3.

Removal of total organic carbon (TOC) residues from power plant make-up water by activated carbon

Organic compounds decomposing in high temperature and pressure of a steam boiler plant water–steam cycle result in low molecular weight (LMW) organic acids and carbon dioxide. Subsequently a drop of pH value is observed in condensate which ultimately can cause corrosion. Organics may also contain for example chloride and release it to condensate. Thirdly decomposition products mask online cation conductivity measurements. This paper evaluates the use of activated carbon (AC) filtration as an option to remove the residues of organic compounds present in deionized make-up water. The experimental part was done using continuous flow bench scale AC filters (AC dry volume 3.75l, flow rate 25l/h, water temperature approximately 20°C) at a steam boiler desalination plant. Four commercial ACs were tested and all proved equally efficient removing approximately 42–45% of total and 58–68% of dissolved organic carbon after 30 days of operation. The most efficiently removed organic fractions were LMW neutral compounds, decomposition products of humic substances and hydrophobic compounds. Biopolymers were not effectively removed. Coconut shell based ACs leached more Ca, Mg and Na ions compared to coal based while for silica there were no differences. Pre-acid washing of ACs was efficient in reducing the initial leaching of impurities. However, the differences between acid washed and non-acid washed AC diminished with time. A mixed bed (MB) ion exchanger as a polishing treatment after AC filters is required to control the leaching of impurities.

Absorption losses in glasses and glass fibre waveguides

Glasses prepared from high purity starting materials were used for pulling optical waveguide fibre by a double crucible technique. The observed optical loss of the glasses and fibres can be accounted for by absorption bands arising from the presence of traces of transition metal ion impurities and the low energy tails of u.v. absorption bands. The relatively high loss of the fibres is attributed to leaching of impurities from the platinum crucibles.