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•Role of oxides in La/Co/(Sr) US/pyrolytically synthesized oxide powders is examined.•The particles become more spherical with increased temperature.•The aggregation of the particles ...is less pronounced with increased temperature.•Csp is higher for the samples containing Sr as perovskite structure promoter.•Capacitive stability and rate capability are lower for the samples of higher Csp.
The role and influence of strontium and its oxide on structure and capacitive response of materials containing mixed lanthanum cobalt oxides, LC, and lanthanum strontium cobalt oxides, LSC, as a capacitive materials were investigated in this study. The mixed oxides were synthesized by the single-step ultrasonic spray pyrolysis (USP) technique. The microstructures and electrochemical properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, potentiostatic electrochemical impedance spectroscopy and galvanostatic charge/discharge cycling. It was found that strontium oxide induces the formation of the perovskite structure of promoted pseudocapacitive behavior over an enhancement of redox transitions of cobalt. The measurements showed that the capacitive stability and rate capability were lower for the samples of higher specific capacitance. Among the prepared materials, the LSC prepared at a USP temperature 600 °C showed the best capacitive characteristics in 0.10 M KOH due to having the most defined spherical perovskite structure leading to well-defined reversible charge–discharge performances.
The automotive industry is in the process of transformation from the traditional production of vehicles with engines powered by the combustion of fossil fuels to vehicles powered by electric energy. ...This revolutionary transformation will generate a growing demand for metallic raw materials that are a crucial part of batteries—nickel and cobalt, among others. Providing enough raw materials for e-mobility in a sustainable way will be a challenge in the years to come. The region of South-Eastern Europe (SEE) and Turkey is relatively rich in lateritic Ni-Co deposits, and this region has the potential to partially replace the import of nickel and cobalt intermediates to the European Union from distant overseas locations. Possibilities for the sustainable sourcing of nickel and cobalt from the SEE region are reviewed in this paper, with an overview of the global demand and production of these metals, lateritic mineral resources of SEE, the current status of production, and the prospective development of nickel and cobalt production in this region.
Flotation tailings rich in carbonate minerals from the tailings deposit of the copper mine Majdanpek (Serbia) were applied for neutralization of the water taken from the extremely acidic Lake Robule ...(Bor, Serbia). Tests conducted in Erlenmeyer flasks showed that after neutralization of the lake water to pH 7, over 99% of aluminum (Al), iron (Fe), and copper (Cu) precipitated, as well as 92% of Zn and 98% of Pb. In order to remove residual Mn and Ag, the water was further treated with NaOH. After treatment with NaOH, all concentrations of the metals in the lake water samples were below discharge limits for municipal wastewater according to the national legislation of the Republic of Serbia. The results of this work suggest that mining waste could be used for active neutralization of the acid mine drainage. The use of the mining waste instead of lime could reduce the costs of the active treatment of the acid mine drainage.
Pt/TiO2 composites were synthesized by single-step ultrasonic spray pyrolysis (USP) at different temperatures. In an in-situ method, Pt and TiO2 particles were generated from tetra-n-butyl ...orthotitanate and chloroplatinic acid, and hydrothermally-prepared TiO2 colloidal dispersion served as Pt support in an ex-situ USP approach. USP-synthesized Pt/TiO2 composites were generated in the form of a solid mixture, morphologically organized in nesting huge hollow and small solid spheres, or TiO2 core/Pt shell regular spheroids by in-situ or ex-situ method, respectively. This paper exclusively reports on characteristic mechanisms of the formation of novel two-component solid composites, which are intrinsic from the USP approach and controlled precursor composition. The generation of the two morphological components within the in-situ approach, the hollow spheres and all-solid spheres, was indicated to be caused by characteristic sol-gel/solid phase transition of TiO2. Both the walls of the hollow spheres and the cores of all-solid ones consist of TiO2 matrix populated by 10 nm-sized Pt. On the other hand, spherical, uniformly-sized, Pt particles of a few nanometers in size created a shell uniformly deposited onto TiO2 spheres of ca. 150 nm size. Activities of the prepared samples in an oxygen reduction reaction and combined oxygen reduction and hydrogen evolution reactions were electrochemically tested. The ex-situ synthesized Pt/TiO2 was more active for oxygen reduction and combined oxygen reduction and hydrogen reactions in comparison to the in-situ Pt/TiO2 samples, due to better availability of Pt within a core/shell structure for the reactions.
Introduction/purpose: Hydrogen is the most abundant element in the universe (75 % by mass) and the lightest element (with a density of 0.00082 g/cm3 ) which consists of only one proton and one ...electron. Because of its presence in many different forms such as gaseous hydrogen, its plasma species, water, acid, alkaline, ammonia and hydrocarbons, it has various applications in different industrial disciplines. Methods: Different hydrometallurgical and pyrometallurgical methods are considered in order to point out many different processes such as formation of hydrogen, reduction of metallic oxides and chlorides, and electrochemical reactions such as hydrogen overvoltage and the spillover effect. Ultrasonic spray pyrolysis enables the formation of very fine aerosols which can be used for the production of metallic powders. Results: Hydrogen formation was observed during the dissolution of metallic alloys with hydrochloric acid. The reduction of metallic oxides and metallic chlorides by hydrogen leads to the formation of metallic powders. Metallic powders were collected by a new developed electrostatic precipitator. Conclusion: Hydrogen can be applied in different reduction processes for the production of metallic powders. Recycling processes can be used for the formation of hydrogen. A new research strategy for powder production is proposed combining recycling of the black mass of used Li-Ion batteries, ultrasonic spray pyrolysis, and hydrogen reduction.
Introduction/purpose: Ultrasonic spray pyrolysis (USP) is usually used for the preparation of submicronic and nanosized gold powders. This is a simple method for a synthesis from an aerosol ...containing dissolved metallic salts such as gold chloride, gold nitrate, and gold-acetate, obtained in the ultrasonic field using frequencies ranging from 0.8 to 2.5 MHz. Methods: The USP method combines aerosol formation in an ultrasonic field, transport of an aerosol with a carrier gas to the reactor and final reduction of HAuCl4 with a used gas such as hydrogen and carbon monoxide. The thermal decomposition of gold acetate takes place in a neutral atmosphere such as nitrogen and argon at elevated temperatures. The chemical reduction of HAuCl4 takes place in the aqueous phase using sodium citrate and sodium boride after heating water solution. Results: Powders of gold were obtained at room temperature using hydrogen reduction in an ultrasonic field at room temperature from HAuCl4 using a frequency of 0.8 MHz. The obtained gold particles were analysed using scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). The formed particles are round and agglomerated. An increase in temperature to 260°C and 500°C leads to the formation of spherical and cylindrical gold particles. Conclusion: New improved equipment for an ultrasonic spray pyrolysis synthesis of gold powder from HAuCl4 with hydrogen reduction was offered by PRIZMA, Kragujevac, Serbia, enabling a controlled reduction process with better prevention of piezo transducers in an ultrasonic field and increased aerosol production and its transport to the reaction furnace.
Introduction/purpose: Bauxite residue as a waste product from the aluminium industry produced through the Bayer process is mainly composed of iron oxide, titanium oxide, silicon oxide and undissolved ...alumina together with a wide range of other oxides and a minor content of rare earth elements, gallium, vanadium and scandium, which vary according to the country of origin of the bauxite. The extraction of valuable elements from bauxite residues and the minimisation of bauxite residues during different treatments are an open research field. Methods: Different hydrometallurgical and pyrometallurgical methods were used for the treatment of bauxite residues. In this study, the results of the hydrometallurgical treatment of bauxite residue from Alumina Zvornik using sulfuric acid and hydrochloric acid will be shown in order to study the change of the mineralogical composition. Leaching efficiency will be calculated using the ICP OES analysis. The XRD-Analysis was used for the characterization of the initial material and solid residues studying the change of the mineralogical phases. Results: Leaching of bauxite residues with sulphuric and hydrochloric acid leads partially to the change of mineralogical structure and the transfer of elements into a liquid phase. Natural precipitation of iron is observed over time. Silica gel formation is confirmed during leaching of bauxite residues with hydrochloric acid. Conclusion: A new research strategy for treating bauxite residue is needed in order to ensure a complete change of the initial minearlogical structure and the most efficient transfer of metals into a liquid phase.
Introduction/purpose: Cobalt is a strategic metal for industrial application. Cobalt recovery from oxidic ores such as laterite and sulphidic ores, and from secondary materials during acidic ...treatment and precipitation is a highly used strategy ensuring different products such as cobalt hydroxide, cobalt oxide, and finally metallic cobalt. Methods: Familiarity with cobalt behavior in hydrometallurgical processes such as dissolution at atmospheric and high pressure, precipitation, neutralization, filtration and hydrogen reduction is most important for cobalt recovery from ores and secondary materials. Pyrometallurgical methods such as roasting and flash smelting are applied for the treatment of sulphidic ores combined with solvent extraction and electrolysis in order to obtain cathodic cobalt. Results: Powders of nickel-cobalt hydroxide were obtained from ores using sulphuric acid under high pressure in an autoclave and after precipitation with MgO. Solvent extraction was used to separate cobalt from nickel. The final step of cobalt recovery from a solution is using electrolysis. Cobalt and cobalt compounds such as cobalt carbonate and cobalt hydroxide can be obtained from secondary materials in hydrometallurgical operations. Conclusion: Hydrometallurgical and pyrometallurgical processes are mostly applied for cobalt recovery from primary ores (oxidic and sulphidic compounds) and from secondary materials (cemented tungsten carbide, polycrystalline diamond blanks, and waste cathodic materials from lithiumion batteries). / Введение/цель: Кобальт является стратегическим металлом в промышленном применении. Извлечение кобальта из оксидных руд, таких как латеритные и сульфидные руды, а также из вторичных материалов во время кислотной обработки и осаждения является широко используемым методом, обеспечивающим получение различных соединений, таких как гидроксид кобальта, оксид кобальта и металлический кобальт. Методы: Гидрометаллургические процессы, такие как растворение при атмосферном и высоком давлении, нейтрализация, осаждение и извлечение водородом, использовались для выщелачивания кобальта из руд и вторичных материалов. Пирометаллургические процессы, такие как обжиг и автогенная плавка сульфидных руд, сочетались с экстракцией растворителем и электролизом при получении катодного кобальта. Результаты: Порошки гидроксида никеля и кобальта получены из руды с использованием серной кислоты при высоком давлении в автоклаве и осаждением оксидом магния. Никель и кобальт разделяли с помощью экстракции растворителем. Конечный раствор с кобальтом использовали в процессе электролиза для получения кобальта. Кобальт и его соединения, такие как карбонат кобальта и гидроксид кобальта, получены из вторичного сырья с помощью гидрометаллургических операций. Выводы: Гидрометаллургические и пирометаллургические процессы в основном используются для выделения кобальта из первичных руд (оксидных и сульфидных соединений) и вторичных материалов (цементированные карбиды вольфрама, поликристаллические алмазные пластины и отходы катодных материалов литий-ионных аккумуляторов). / Uvod/cilj: Kobalt je strategijski metal u industrijskoj primeni. Njegovo izdvajanje iz oksidnih ruda, zvanih lateriti, i sulfidnih ruda, kao i sekundarnih materijala tretiranjem kiselinom i precipitacijom najčešće je korišćen metod koji obezbeđuje različite produkte kao što su kobalt hidroksid, kobalt oksid imetalni kobalt. Metode: Hidrometalurški procesi, kao što su rastvaranje pri atmosferskom i visokom pritisku, neutralizacija, precipitacija i redukcija vodonikom korišćeni su za izdvajanje kobalta iz ruda i sekundarnih materijala. Pirometalurški procesi, kao što su prženje i autogeno topljenje sulfidnih ruda, kombinovani su sa solvent ekstrakcijom i elektrolizom za dobijanje katodnog kobalta. Rezultati: Prahovi nikal-kobalt hidroksida dobijeni su iz ruda korišćenjem sumporne kiseline pri visokom pritisku u autoklavu i precipitacijom sa magnezijum oksidom. Nikal i kobalt razdvajani su korišćenjem solvent ekstrakcije. Finalni rastvor sa kobaltom korišćen je u procesu elektrolize za dobijanje kobalta. Kobalt i njegova jedinjenja kao što su kobalt karbonat i kobalt hidroksid dobijaju se iz sekundarnih sirovina pomoću hidrometalurških operacija. Zaključak: Hidrometalurški i pirometalurški procesi većinom su primenjeni za izdvajanje kobalta iz primarnih ruda (oksidna i sulfidna jedinjenja) i sekundarnih materijala (cementirani karbidi volframa, polikristalne dijamantske pločice i otpadni katodni materijali iz litijumjonskih baterija).
Introduction/purpose: Carbonation of minerals (olivine and wollastonite) and secondary materials such as slag under high pressure in autoclaves has high importance due to environmetal problems. ...Methods: The most important for this process is to have a good knowledge of the behavior of carbon dioxide in water solution under high pressure, the precipitation of silica, dissolution of metals such as nickel and magnesium as well as subsequent filtration. Results: The carbonation process of olivine und slag under high pressure (from 40 to 80 bar) in an autoclave was successfully performed at 175°C, with and without additivies. Conclusion: A comparative analysis has confirmed better carbonation of slag (max. 300 kg/ton) in comparison to that of olivine (max. 70 kg/ton) under the same conditions.
Introduction/purpose: Dissolution of nonferrous metals from oxidic ores such as laterite, high silicon bauxite and eudialyte during acidic treatment was connected with silica gel formation. Methods: ...Familiarity with behavior of silica in hydrometallugical processes such as dissolution at atmospheric and high pressure, precipitation, neutralization and filtration is most important for the recovery of metals from water solution. Results:. Gel formation was avoided using dry digestion and a carbonation process of olivine under high pressure in an autoclave. Conclusion: Fine silica was prepared from olivine in water solution at 175°C and 120 bar for 4 hours in an autoclave using some additives such as sodium bicarbonate and oxalic acid. / Введение/цель: Растворение цветных металлов из оксидных руд, таких как латерит, боксит с высоким содержанием кремния и эвдиалит, во время кислотной обработки было связано с образованием силикагеля. Методы: Ознакомление с поведением кремнезема в гидрометаллургических процессах, таких как растворение при атмосферном и высоком давлении, осаждение, нейтрализация и фильтрация, оказалось весьма важным при извлечении металлов из водного раствора. Результаты: Предотвращение гелеобразования стало возможным благодаря использованию раствора с высокой концентрацией кислот («сухой раствор») и абсорбции диоксида углерода из оливина при высоком давлении в автоклаве. Выводы: Изготовление мелкодисперсного порошка кремнезема из оливина в водном растворе было достигнуто при 175 ° С и 120 бар и в течение 4 часов в автоклаве с использованием добавок, таких как бикарбонат натрия и щавелевая кислота. / Uvod/svrha: Rastvaranje obojenih metala iz oksidnih ruda, kao što su lateriti, boksiti sa visokim sadržajem silicijuma i eudialit, korišćenjem kiselina povezano je sa stvaranjem gela od silicijum-dioksida. Metode: Sličnost sa ponašanjem silicijum-dioksida u hidrometalurškim procesima, kao što su rastvaranje pri atmosferskom i visokom pritisku, taloženje, neutralizacija i filtriranje, od velikog je značaja za izvlačenje metala iz rastvora. Rezultati: Izbegavanje formiranja gela omogućeno je korišćenjem rastvaranja velikim koncentracijama kiselina ("suvo rastvaranje") i apsorpcijom ugljen-dioksida od olivina pri visokom pritisku u autoklavu. Zaključak: Priprema finog praha silicijum-dioksida iz olivina u vodenom rastvoru postignuto je na 175°C i 120 bara za 4 sata u autoklavu korišćenjem dodataka kao što su natrijumbikarbonat i oksalna kiselina.
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