Nitric acid leaching of polymetallic middlings of concentration

Investigations into the nitric acid leaching of polymetallic middlings with the purpose of the maximal recovery of copper and zinc into the solution are performed. Using methods of mathematical planning of the experiment, the optimal process parameters are determined: ratio L: S = 5, the consumption of nitric acid is 80 cm3 per 20 g of the charge, and the process duration is 120 min. © 2013 Allerton Press, Inc

Effect of preliminary alkali desilication on ammonia pressure leaching of low-grade copper–silver concentrate

Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 0836-2020-0020Funding: This work was financially supported by the Russian Science Foundation Project No. The SEM-EDX analyses were funded by State Assignment, grant number 0836-2020-0020

Leaching kinetics of arsenic sulfide-containing materials by copper sulfate solution

The overall decrease in the quality of mineral raw materials, combined with the use of arsenic-containing ores, results in large amounts of various intermediate products containing this highly toxic element. The use of hydrometallurgical technologies for these materials is complicated by the formation of multicomponent solutions and the difficulty of separating copper from arsenic. Previously, for the selective separation of As from copper–arsenic intermediates a leaching method in the presence of Cu(II) ions was proposed. This paper describes the investigation of the kinetics of arsenic sulfide-containing materials leaching by copper sulfate solution. The cakes after leaching of arsenic trisulfide with a solution of copper sulfate were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analysis (EDS). The effect of temperature (70–90 °C), the initial concentration of CuSO4 (0.23–0.28 M) and the time on the As recovery into the solution was studied. The process temperature has the greatest effect on the kinetics, while an increase in copper concentration from 0.23 to 0.28 M effects an increase in As transfer into solution from 93.2% to 97.8% for 120 min of leaching. However, the shrinking core model that best fits the kinetic data suggests that the process occurs by the intra-diffusion mode with the average activation energy of 44.9 kJ/mol. Using the time-to-a-given-fraction kinetics analysis, it was determined that the leaching mechanism does not change during the reaction. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 − X) + [(1 − X) − 1/3 − 1] = 4,560,000Cu3.61e−44900/RT t. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.10.7347.2017/8.9Russian Science Foundation, RSF: 18-19-00186Funding: The research was funded by the Russian Science Foundation, grant number 18-19-00186. The SEM/EDS analyses were funded by State Assignment, grant number 10.7347.2017/8.9

Research features of opening of refractory arsenopyrite concentrates by using low-temperature roasting

The article describes an alternative pre-treatment method of refractory arsenopyrite concentrates using low temperature roasting. The process consists of carrying out oxidative roasting in the temperature range of 200-400 C - relatively low for traditional process. The calculation results of the equilibrium composition of roasting products are presented on the example of a flotation gold-bearing concentrate of the Uderey's deposit in the HSC Chemistry 6 program. The main concentrate minerals containing gold arepyrite (FeS2) and arsenopyrite (FeAsS). In addition, the concentrate of the Uderey's deposit is characterized by the presence of antimony in the form of Sb2S3. During the calculations of the equilibrium composition, the optimal conditions for low-temperature roasting were selected. It was found that under these conditions, the dissociation of higher sulfides occurs, arsenic goes into the form of trisulfide (As2S3) and some of the iron goes into the form of sulfate (FeSO4). All this suggests that the process of low-temperature roasting allows to open the refractory concentrate and get a cinder, the further processing of which will not cause special problems: the non-volatile form of arsenic trisulfide will not cause complications when cleaning exhaust gases, and iron sulfate will simplify further leaching processes. © Published under licence by IOP Publishing Ltd

Leaching kinetics of sulfides from refractory gold concentrates by nitric acid

The processing of refractory gold-containing concentrates by hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in the ores. This paper describes the investigation of the kinetics of HNO3 leaching of sulfide gold-containing concentrates of the Yenisei ridge (Yakutia, Russia). The effect of temperature (70–85 °C), the initial concentration of HNO3 (10–40%) and the content of sulfur in the concentrate (8.22–22.44%) on the iron recovery into the solution was studied. It has been shown that increasing the content of S in the concentrate from 8.22 to 22.44% leads to an average of 45% increase in the iron recovery across the entire range temperatures and concentrations of HNO3 per one hour of leaching. The leaching kinetics of the studied types of concentrates correlates well with the new shrinking core model, which indicates that the reaction is regulated by interfacial diffusion and diffusion through the product layer. Elemental S is found on the surface of the solid leach residue, as confirmed by XRD and SEM/EDS analysis. The apparent activation energy is 60.276 kJ/mol. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 - X) + [(1 - X)-1/3 - 1] = 87.811(HNO3)0.837(S)2.948e-60276/RT·t. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The research was funded by the Russian Science Foundation, grant number 18-19-00186. The SEM/EDS and microprobe analysis were funded by State Assignment, grant number 11.4797.2017/8.9

Development of a Two-Stage Hydrometallurgical Process for Gold–Antimony Concentrate Treatment from the Olimpiadinskoe Deposit

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R2) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As2S3 was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold–antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake. © 2023 by the authors.Russian Science Foundation, RSF: 075-03-2021-051/5, 22-79-10290, FEUZ-2021-0017This work was funded by the Russian Science Foundation Project No. 22-79-10290. The XRF and XRD analyses were funded by the State Assignment, grant No. 075-03-2021-051/5 (FEUZ-2021-0017)

Combined processing of Erdenet Ore-Dressing Plant pyrite concentrates

On the basis of studying pyrite concentrate substance composition, obtained at the same time during flotation of copper-porphyry ores of the Erdenetiin Ovoo deposit, the possibility is considered of extracting valuable components from it. © 2013 Springer Science+Business Media New York

Deposition of arsenic from nitric acid leaching solutions of gold—arsenic sulphide concentrates

At present, the processing of refractory gold–arsenic sulphide concentrates is becoming more relevant due to the depletion of rich crude ore reserves. In the process of the nitric acid leaching of arsenic sulphide minerals, solutions are formed containing 20–30 g/L of arsenic (III). Since market demand for arsenic compounds is limited, such solutions are traditionally converted into poorly soluble compounds. This paper describes the investigation of precipitating arsenic sulphide from nitric acid leaching solutions of refractory sulphide raw materials of nonferrous metals containing iron (III) ions using sodium hydrosulphide with a molar ratio of NaHS/As = 2.4–2.6, which is typical for pure model solutions without oxidants. The work studied the effect of temperature, the pH of the solution and the consumption of NaHS and seed crystal on this process. The highest degree of precipitation of arsenic (III) sulphide (95–99%) from nitric acid leaching solutions containing iron (III) ions without seed occurs with a pH from 1.8 to 2.0 and a NaHS/As molar ratio of 2.8. The introduction of seed crystal significantly improves the precipitation of arsenic (III) sulphide. An increase in seed crystal consumption from 0 to 34 g/L in solution promotes an increase in the degree of transition of arsenic to sediment from 36.2 to 98.1% at pH = 1. According to SEM/EDS and XRF sediment data, from the results of experiments on the effect of As2S3 seed crystal consumption, acidity and molar ratio of NaHS/As on the precipitation of arsenic (III) sulphide and the Fetotal/Fe2+ ratio in the final solution, it can be concluded that the addition of a seed accelerates the crystallisation of arsenic (III) sulphide by increasing the number of crystallisation centres; as a result, the deposition rate of As2S3 becomes higher. Since the oxidation rate of sulphide ions to elemental sulphur by iron (III) ions does not change significantly, the molar ratio of NaHS/As can be reduced to 2.25 to obtain a precipitate having a lower amount of elemental sulphur and a high arsenic content similar to that precipitated from pure model solutions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was financially supported by the Russian Science Foundation Project No. 20-79-00321. The SEM–EDS analyses were funded by State Assignment, Grant No. 0836-2020-0020

Nitric Acid Dissolution of Tennantite, Chalcopyrite and Sphalerite in the Presence of Fe (III) Ions and FeS2

This paper describes the nitric acid dissolution process of natural minerals such as ten-nantite, chalcopyrite and sphalerite, with the addition of Fe (III) ions and FeS2. These minerals are typical for the ores of the Ural deposits. The effect of temperature, nitric acid concentration, time, additions of Fe (III) ions and FeS2 was studied. The highest dissolution degree of sulfide minerals (more than 90%) was observed at a nitric acid concentration of 6 mol/dm3, an experiment time of 60 min, a temperature of 80 °C, a concentration of Fe (III) ions of 16.5 g/dm3, and an addition of FeS2 to the total mass minerals at 1.2:1 ratio. The most significant factors in the break-down of minerals were the nitric acid concentration, the concentration of Fe (III) ions and the amount of FeS2. Simultaneous addition of Fe (III) ions and FeS2 had the greatest effect on the leaching process. It was also estab-lished that FeS2 can be an alternative catalytic surface for copper sulfide minerals during nitric acid leaching. This helps to reduce the influence of the passivation layer of elemental sulfur due to the galvanic linkage formed between the minerals, which was confirmed by SEM-EDX. © 2022 by the author. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 075-03-2021-051/5, 20-79-00317, FEUZ-2021-0017Funding: This work was funded by the Russian Science Foundation Project No. 20-79-00317. The SEM-EDX, XRF, XRD analysis were funded by State Assignment, grant No. 075-03-2021-051/5 (FEUZ-2021-0017)

Pressure oxidation of arsenic (Iii) ions in the h3aso3-fe2+-cu2+-h2so4 system

The processing of low-grade polymetallic materials, such as copper–zinc, copper–lead– zinc, and poor arsenic-containing copper concentrates using hydrometallurgical methods is becom-ing increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in ores. Ferric arsenates obtained through hydrothermal precipitation are the least soluble and most stable form of arsenic, which is essential for its disposal. This paper describes the investigation of the oxidation kinetics of As (III) ions to As (V) which is required for efficient puri-fication of the resulting solutions and precipitation of low-solubility ferric arsenates. The effect of temperature (160–200 °C), the initial concentration of Fe (II) (3.6–89.5 mmol/dm3), Cu (II) (6.3–62.9 of mmol/dm3) and the oxygen pressure (0.2–0.5 MPa) on the oxidation efficiency of As (III) to As (V) was studied. As (III) oxidation in H3AsO-Fe2+-Cu2+-H2SO4 and H3AsO-Fe2+-H2SO4 systems was controlled by a chemical reaction with the apparent activation energy (Ea (≈84.3–86.3 kJ/mol)). The increase in the concentration of Fe (II) ions and addition of an external catalyst (Cu (II) ions) both have a positive effect on the process. When Cu (II) ions are introduced into the solution, their catalytic effect is confirmed by a decrease in the partial orders, Fe (II) ions concentration from 0.43 to 0.20, and the oxygen pressure from 0.95 to 0.69. The revealed catalytic effect is associated with a positive effect of Cu (II) ions on the oxidation of Fe (II) to Fe (III) ions, which further participate in As (III) oxidation. The semi-empirical equations describing the reaction rate under the studied conditions are written. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was financially supported by the Russian Science Foundation Project No. 20‐ 79‐00321