Features of the Behavior of Precious Metals in the Sulfide-Alkaline Leaching of Arsenic-Antimony Concentrates

Для минерально-сырьевой базы металлургии цветных и благородных металлов месторождения полиметаллических руд являются основным источником сырья. На фоне глобальной тенденции к снижению доли богатых руд в общем объеме добычи и переработки и ухудшению качественных характеристик рудного сырья ведется отработка запасов руд, содержащих в виде примесей мышьяк и сурьму. Авторами была изучена возможность применения ASL‑технологии при атмосферном давлении для гидрометаллургического кондиционирования низкокачественного медного концентрата. Исследования осуществлялись на флотационном концентрате следующего состава (%): 16,1 Cu; 5,3 Zn; 23,8 Fe; 0,84 Pb; 1,36 As; 0,21 Sb; 1,94 SiO2; 0,82 Al2O3, до 24,0 г/т Ag, до 4,0 г/т Au. В результате выполненных исследований были выявлены особенности поведения благородных металлов в сульфидно-щелочной среде в процессе выщелачивания мышьяково-сурьмянистых концентратов Учалинского ГОКа. Установлена доминирующая роль сульфида натрия при образовании полисульфид- и тиосульфат-ионов, выполняющих роль окислителей золота и серебра. Анализ кинетических показателей свидетельствует о лимитировании процесса выщелачивания благородных металлов скоростью химической реакции при отсутствии внутридиффузионных ограничений, обусловленных возможной пассивацией теннантита, формирующимися вторичными сульфидами меди. Определены минимальные пороговые концентрации сульфида и полисульфидов, при которых возможен переход в раствор выщелачивания золота и серебра: для сульфида более 20 г/л‑1, для полисульфидов более 2 М. При проведении ASL‑процесса с указанными параметрами кек выщелачивания представляет собой кондиционный медно-цинковый концентрат, содержащий 0,2 % мышьяка и благородных металлов до 100 г/т. Потери благородных металлов в ходе процесса отсутствуютFor the mineral resource base of metallurgy of non-ferrous and noble metals, deposits of polymetallic ores are the main source of raw materials. Against the backdrop of a global trend towards a decrease in the share of rich ores in the total volume of mining and processing, and a deterioration in the quality characteristics of ore raw materials, ore reserves containing arsenic and antimony as impurities are being developed. The authors studied the possibility of using ASL technology at atmospheric pressure for hydrometallurgical conditioning of low-quality copper concentrate. The studies were carried out on a flotation concentrate of the following composition (%): 16.1 Cu; 5.3 Zn; 23.8 Fe; 0.84 Pb; 1.36 As; 0.21 Sb; 1.94 SiO2; 0.82 Al2O3, up to 24.0 g/t Ag, up to 4.0 g/t Au. As a result of the studies carried out, the features of the behavior of noble metals in the sulfide-alkaline environment during the leaching of arsenic-antimony concentrates of the Uchalinsky GOK were revealed. The dominant role of sodium sulfide in the formation of polysulfide and thiosulfate ions, which act as oxidizers for gold and silver, has been established. An analysis of the kinetic parameters indicates that the process of leaching of precious metals is limited by the rate of a chemical reaction in the absence of intradiffusion restrictions due to the possible passivation of tennantite by the formed secondary copper sulfides. The minimum threshold concentrations of sulfide and polysulfides were determined, at which a transition to the gold and silver leaching solution is possible: for sulfide more than 20 g/l‑1, for polysulfides more than 2 M. The obtained product after ASL process was copper-zinc concentrate containing 0.2 % arsenic and precious metals up to 100 g/t. There are no losses of precious metals during the proces

One-Pot Synthesis of Hyperbranched Polyurethane-Triazoles with Controlled Structural, Molecular Weight and Hydrodynamic Characteristics

We report a simple and convenient approach to the one-pot synthesis of hyperbranched polyurethane-triazoles with desirable properties. This method is based on in situ generation of an AB2 + A2 + B4 azide-acetylene monomer mixture of known composition, due to quantitative reactions of urethane formation between isophorone diisocyanate (IPDI), 1,3-diazidopropanol-2 (DAPOL) (in the first stage) and propargyl alcohol (in the second stage). The obtained monomer mixture can be involved in step-growth polymerization by azide-alkyne cycloaddition without additional purification (in the third stage). The properties of the resulting polymers should depend on the composition of the monomer mixture. Therefore, first the model revealing the correlation between the monomer composition and the ratio and reactivity of the IPDI and DAPOL active groups is developed and proven. In addition, the newly developed structural kinetic model considering the substitution effect at polyaddition of the complex mixture of monomers allows the prediction of the degree of branching of the target polymer. Based on our calculations, the hyperbranched polyurethane-triazoles were synthesized under found conditions. All products were characterized by 1H NMR, FTIR, SEC, DLS, DSC, TGA and viscometry methods. It was shown that the degree of branching, molecular weight, intrinsic viscosity, and hydrodynamic radius of the final hyperbranched polymers can be specified at the first stage of one-pot synthesis. The obtained hyperbranched polyurethane-triazoles showed a degree of branching from 0.21 to 0.44 (calculated DB-0.25 and 0.45, respectively)

Synthesis, Antibacterial Activity, and Cytotoxicity of Azido-Propargyloxy 1,3,5-Triazine Derivatives and Hyperbranched Polymers

A new method for the synthesis of azido-propargyloxy derivatives of 1,3,5-triazine has been developed utilizing the nitrosation of hydrazyno-1,3,5-triazines. New hydrazines (2-hydrazino-4,6-bis(propargyloxy)-1,3,5-triazine and 2,4-dihydrazino-6-propargyloxy-1,3,5-triazine) were synthesized and characterized via FTIR, NMR spectroscopy and elemental analysis. The hyperbranched polymers with azide (diazide monomer) and propargyloxy terminal groups were obtained via the azide-alkyne polycycloaddition reaction of diazide and monoazide AB2-type monomers. The antibacterial activity against Escherichia coli bacteria of 2,4,6-trispropargyloxy-1,3,5-triazine, 2-azido-4,6-bispropargyloxy-1,3,5-triazine, and 2,4-diazido-6-propargyloxy-1,3,5-triazine and their hyperbranched polymers was studied. Only 2,4-diazido-6-propargyloxy-1,3,5-triazine has weak antibacterial activity in comparison with ampicillin. The cytotoxicity of these compounds against M-HeLa, FetMSC, and Vero cell lines was also studied. 2,4,6-trispropargyloxy-1,3,5-triazine does not show any cytotoxic effect (IC50 ≥ 280 µM). It was shown that the presence of an azide group in the compound directly affects the cytotoxic effect. Hyperbranched polymers have a less cytotoxic effect against M-HeLa (IC50 > 100) in comparison with monomers (IC50 = 90–99 µM). This makes it possible to use these polymers as the basis for biocompatible materials in biomedical applications

Unusual Tri‑, Hexa‑, and Nonanuclear Cu(II) Cage Methylsilsesquioxanes: Synthesis, Structures, and Catalytic Activity in Oxidations with Peroxides

Three types of unusual cagelike copper­(II) methylsilsesquioxanes, namely, nona- [(MeSiO_1.5)₁₈(CuO)₉] <b>1</b>, hexa- [(MeSiO_1.5)₁₀(HO_0.5)₂(CuO)₆­​(C₁₂H₈N₂)₂­(MeSiO_1.5)₁₀(HO_0.5)_1.33­​(CH₃COO_0.5)_0.67(CuO)₆­(C₁₂H₈N₂)₂] <b>2</b>, [(MeSiO_1.5)₁₀(CuO)₆­​(MeO_0.5)₂­(C₁₀H₈N₂)₂] <b>3</b>, and trinuclear [(MeSiO_1.5)₈­​(CuO)₃(C₁₀H₈N₂)₂] <b>4</b>, were obtained in 44%, 27%, 20%, and 16% yields, respectively. Nuclearity and structural fashion of products was controlled by the choice of solvent system and ligand, specifically assisting the assembling of cage. Structures of <b>1</b>–<b>4</b> were determined by single-crystal X-ray diffraction analysis. Compounds <b>1</b> and <b>4</b> are the first cage metallasilsesquioxanes, containing nine and three Cu ions, respectively. Product <b>1</b> is the first observation of nonanuclear metallasilsesquioxane ever. Unique architecture of <b>4</b> represents early unknown type of molecular geometry, based on two condensed pentamembered siloxane cycles. Topological analysis of metal clusters in products <b>1</b>–<b>4</b> is provided. Complex <b>1</b> efficiently catalyzes oxidation of alcohols with <i>tert</i>-butylhydroperoxide TBHP to ketones or alkanes with H₂O₂ to alkyl hydroperoxides in acetonitrile

Cardiac myosin activation with omecamtiv mecarbil in systolic heart failure

BACKGROUND The selective cardiac myosin activator omecamtiv mecarbil has been shown to improve cardiac function in patients with heart failure with a reduced ejection fraction. Its effect on cardiovascular outcomes is unknown. METHODS We randomly assigned 8256 patients (inpatients and outpatients) with symptomatic chronic heart failure and an ejection fraction of 35% or less to receive omecamtiv mecarbil (using pharmacokinetic-guided doses of 25 mg, 37.5 mg, or 50 mg twice daily) or placebo, in addition to standard heart-failure therapy. The primary outcome was a composite of a first heart-failure event (hospitalization or urgent visit for heart failure) or death from cardiovascular causes. RESULTS During a median of 21.8 months, a primary-outcome event occurred in 1523 of 4120 patients (37.0%) in the omecamtiv mecarbil group and in 1607 of 4112 patients (39.1%) in the placebo group (hazard ratio, 0.92; 95% confidence interval [CI], 0.86 to 0.99; P = 0.03). A total of 808 patients (19.6%) and 798 patients (19.4%), respectively, died from cardiovascular causes (hazard ratio, 1.01; 95% CI, 0.92 to 1.11). There was no significant difference between groups in the change from baseline on the Kansas City Cardiomyopathy Questionnaire total symptom score. At week 24, the change from baseline for the median N-terminal pro-B-type natriuretic peptide level was 10% lower in the omecamtiv mecarbil group than in the placebo group; the median cardiac troponin I level was 4 ng per liter higher. The frequency of cardiac ischemic and ventricular arrhythmia events was similar in the two groups. CONCLUSIONS Among patients with heart failure and a reduced ejection, those who received omecamtiv mecarbil had a lower incidence of a composite of a heart-failure event or death from cardiovascular causes than those who received placebo. (Funded by Amgen and others; GALACTIC-HF ClinicalTrials.gov number, NCT02929329; EudraCT number, 2016 -002299-28.)