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

Efficacy of comprehensive dental treatment for lichenoid reactions of the mucoparodontal complex: A single-center pilot cohort study

Background. Lichenoid reactions of the oral mucosa are currently recognized as a serious issue for dentists of various specialties, since their knowledge and competence in the diagnosis and pathogenetic treatment of lichenoid lesions of the oral cavity are yet to be improved. Following the data on high oncogenic potential in some forms of lichenoid reactions of oral cavity mucous membranes, the issue should be given serious considerations, and dentists should keep oncology-related suspicion when receiving these patients.Objective. To evaluate the efficacy of comprehensive dental treatment for lichenoid reactions of the mucoparodontal complex.Methods. A single-center pilot cohort study was conducted to evaluate the efficacy of the comprehensive treatment (combination of pharmacotherapy and physiotherapy) of patients with lichenoid reactions of the oral mucosa. The observation group consisted of 49 patients (15 males, 34 females) aged 58.92 ± 0.82 years with verified diagnoses of oral mucosa lichenoid reactions. The suggested treatment included pharmacotherapy (highly-potent topical steroids, calcineurin inhibitors) and physiotherapy in the form of low level laser therapy (635 nm, 10 W) provided via Matrix laser (Matrix, Russia). Treatment efficacy was assessed by the total scale of treatment efficacy, registering indicators of the area of focal lesions and the severity of pain syndrome, as well as by changes in dental quality of life indicators according to OHIP-49-RU (Oral Health Impact Profile) in the Russian version. Statistical processing of the data involved Student’s t-test and Wilcoxon t-test. Differences were considered significant at p ≤ 0.05. Data statistical analysis was performed using SPSS 13.0 (SPSS Inc., USA).Results. During the follow-up period, the indicators of the total scale of treatment efficacy decreased significantly (p < 0.001) in 100% of patients and amounted (as medians and quartiles): 6.0 (4.0–7.0) points before treatment and 1.0 (1.0–2.0) points after treatment to be objectified by a significant reduction in the area of focal lesions (by 63.2%, p < 0.001) and in pain syndrome (spontaneous pain from 2.0 (1.5–3.0) points before treatment to 0.0 (0.0–1.0) points after treatment; induced pain from 3.0 (2.0–3.0) points to 1.0 (0.0–1.0) points). Along with the clinical improvement, the scores in dental quality of life improved from 83.11 ± 2.58 to 39.94 ± 0.86 points, according to OHIP-49 RU (Oral Health Impact Profile).Conclusion. Early detection and differentiation of lichenoid reactions in oral mucous membranes ensure timely treatment using the developed protocol of comprehensive treatment (combination of pharmacotherapy and physiotherapy). The efficacy of the protocol was confirmed clinically and justified in relation to quality of life

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

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

Technology for the hydrometallurgical processing of a complex multicomponent sulfide-based raw material

An analysis of the methods currently used for the metallurgical processing of polymetallic middlings from the beneficiation of sulfide ores shows that the oxidant which is the most promising for use as an agent to leach the middlings is nitric acid. A technology is developed to process hard-to-decompose middlings with the use of nitric acid. © 2013 Springer Science+Business Media New York

Sorption of Neptunium-237 on Thin-Layer Sorbents

In this work, we studied the sorption and diffusion of neptunium-237 in the MnO2-cellulose triacetate sorbent. Dependences of sorption on various parameters were obtained.Работа выполнена при финансовой поддержке РФФИ (проект № 20-03-00931)