The influence of mechanical activation of chalcopyrite on the selective leaching of copper by sulphuric acid

In this paper chalcopyrite, CuFeS2, has been selective leached by H2SO4 as leaching agent (170 g/dm3) in procedure of hydrometallurgical production of copper. Mechanical activation of the chalcopyrite resulted in mechanochemical surface oxidation as well as in the mineral surface and bulk disordering. Furthermore, the formation of agglomerates during grinding was also occured. Surface changes of the samples using infrared spectroscopy and scanning electron microscopy methods were investigated before and after leaching. The leaching rate, specific surface area, structural disorder as well as copper extraction increased with the mechanical activation of mineral

Influence of the milling parameters on the mechanical work intensity in planetary mills

The formation of ZnSe via a mechanically-induced self-sustaining reaction (MSR) from a Zn/Se mixture showed that only size reduction and mixing of the reactants without product formation occurred during the induction period prior to ignition. Therefore, all mechanical energy supplied by the planetary mill during this time, called the ignition time (t ig), was used exclusively in the activation of the reactants. This system was chosen to study the dependence of t ig on the main parameters characterising the milling intensity of planetary mills. The variation of the ignition time with the process conditions reflected changes in the mechanical dose rate of the planetary mill. A direct relationship between the inverse of the ignition time and the power of the planetary mill was established, which allows the validation of theoretical models proposed in the literature for the energy transfer in milling devices and the comparison of milling equipment efficienciesCSIC No. 2009SK0002Gobierno de España No. MAT2011-2298

Hallmarks of mechanochemistry: From nanoparticles to technology

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).Slovak Grant Agency VEGA 2/0009/11, 2/0043/11Slovak Agency for Science and Development APVV VV-0189-10, VV-0528-11Russian Foundation for Basic Research 10-03-00942a, 12-03-00651aMinistry of Science and Higher education in Poland CUT/c-1/DS/KWC/2008-2012, PB1T09B02330, NN209145136, NN20914893

Mechanochemical synthesis of nanocrystalline lead selenide

Mechanochemical synthesis of lead selenide PbSe nanoparticles has been performed by high-energy milling of lead and selenium powder in a planetary ball mill Pulverisette 6 (Fritsch, Germany) and in an industrial eccentric vibratory mill ESM 654 (Siebtechnik GmbH, Germany). Structural properties of the synthesized lead selenide were characterized by X-ray diffraction, which confirms crystalline nature of PbSe nanoparticles (JCPDS 6-354). The average size of PbSe crystallites of 37 nm was calculated from XRD data by Williamson-Hall method. The methods of particle size distribution analysis, specific surface area measurement, scanning electron microscopy and transmission electron microscopy were used for characterization of surface, mean particle size, and morphology of PbSe. An application of industrial mill verified a possibility of the synthesis of a narrowband-gap semiconductor PbSe at ambient temperature and in a relatively short reaction time

Influence of the milling parameters on the mechanical work intensity in planetary mills

The formation of ZnSe via a mechanically-induced self-sustaining reaction (MSR) from a Zn/Se mixture showed that only size reduction and mixing of the reactants without product formation occurred during the induction period prior to ignition. Therefore, all mechanical energy supplied by the planetary mill during this time, called the ignition time (t ig), was used exclusively in the activation of the reactants. This system was chosen to study the dependence of t ig on the main parameters characterising the milling intensity of planetary mills. The variation of the ignition time with the process conditions reflected changes in the mechanical dose rate of the planetary mill. A direct relationship between the inverse of the ignition time and the power of the planetary mill was established, which allows the validation of theoretical models proposed in the literature for the energy transfer in milling devices and the comparison of milling equipment efficiencies. © 2012 Elsevier B.V.Peer Reviewe

Mechanochemistry of Solids: New Prospects for Extractive Metallurgy, Materials Science and Medicine

In this review paper recent advances in chalcogene mechanochemistry are described. Three selected areas are being covered, i.e. metallurgy, materials science, and medicine. In extractive metallurgy, the processing of copper arsenic mineral enargite ($Cu_3AsS_4$) with the aim of its dearsenification and subsequent preparation of a new anticancer drug ($Na_3AsS_4$) and of copper in nanocrystalline state ( ≈ 20 nm) illustrate the non-traditional prospect of ore treatment. In material science, the new nanocrystalline semiconductors were synthesized mechanochemically, e.g. selenides of zinc and lead (ZnSe, PbSe) and bismuth sulphide ($Bi_2S_3$). Metal and chalcogene were applied as reaction precursors. In some cases, the amino acids (cystine, cysteine) were applied as sulphur precursor, in order to provide reactive sites on synthesized solid (PbS) for bioconjugation and to prevent agglomeration. The concept of nanomilling is described as a way to prepare effective substances for cancer treatment in medicine. In vitro activity of realgar ($As_4S_4$) as an example is described. In all three areas the focus is aimed also on industrial applications where suitable large-scale mills are described. The described examples represent the contemporary aim of mechanochemists - to prepare substances with the desired properties in a reproducible way under easy-operating, environmentally friendly and essentially waste-free conditions

Photocatalytic Properties of Mechanochemically Synthesized Nanocrystalline ZnAl2O4ZnAl_2O_4 and CdSe

Nanocrystalline powders of $ZnAl_2O_4$ and CdSe were prepared via mechanochemical synthesis. Powder slurries were coated as thin films on $SiO_2$ thin layer chromatography (TLC) sheet by capillary method. The photocatalytic activity of the film coating was tested in a self-made gas-phase flat-plate continuous-flow photocatalytic reactor with toluene as model air contaminant. The tested nanocrystalline $ZnAl_2O_4$ turned out to be poor oxidation photocatalyst under UV irradiation. CdSe displays considerable photocatalytic activity under visible light, where $TiO_2$ is inactive. The nonconventional one-step mechanochemical route to $ZnAl_2O_4$ and CdSe synthesis offers several advantages compared to traditional processing routes, including low-temperature solid state reactions at ambient temperature, absence of organic templates contamination and low expenses

Study of the Mechanochemical Reduction of Ilmenite Concentrate by Addition of Aluminum

Mechanochemical reduction of ilmenite concentrate $(FeTiO_{3})$ with elemental aluminum powder was performed by high-energy milling in an industrial eccentric vibratory ball mill ESM 656-0.5 ks (Siebtechnik, Germany). The mechanochemically reduced ilmenite with various times of milling was characterized by X-ray diffraction analysis, which confirmed the presence of the $Al_2O_3$ and $Fe_2Ti$ phases after 120 min of milling. Thermal analysis evidenced the completion of a mechanochemical reduction during milling. After 360 min of milling, the $Fe_2Ti$ phase decomposed to α-(Fe,Ti) alloy, which was proven by $\text{}^{57}Fe$ Mössbauer spectroscopy. X-ray photoelectron spectroscopy detected the amorphous TiO phase in product after mechanochemical reduction, which is in accordance with thermodynamic prediction. Decreasing of specific surface area after 60 min of milling resulted from growing layers of the solid products of $FeTiO_3$ mechanochemical reduction

Magnetizace jako efektivní nástroj pro kinetickou evaluaci mechanochemické syntézy chalkopyritu CuFeS2

Copper, iron, and sulphur in elemental form were applied for mechanochemical synthesis of chalcopyrite CuFeS2. Products of synthesis were characterized by XRD method and evaluated by Rietveld analysis. A mixture of cubic (JCPDS 75-6866) and tetragonal (JCPDS 37-0471) phases of chalcopyrite with almost identical diffractograms were identified. Both phases are nanocrystalline with sizes 13 nm and 7 nm for laboratory and industrial milling, respectively. For determination of iron consumption during the synthesis, method of magnetometry has been applied. Based on magnetization data reflecting time dependent incorporation of elemental iron into chalcopyrite nanostructure, the kinetics of the synthesis was evaluated. From kinetic data the rate constant of reaction k, as well as the conversion degree R were determined. High conversion degree of mechanochemical synthesis performed in a laboratory mill (R = 100%), as well as in an industrial mill (R = 96%) offer the possibility to scale-up the process of synthesis in preparation of this perspective magnetic semiconductor. The method of magnetometry was proved to be an effective tool for following the processes of synthesis where iron particles are incorporated.Měď, železo a síra v elementární formě byly použity pro mechanochemickou syntézu chalkopyritu CuFeS2. Produkty syntézy byly charakterizovány metodou XRD a hodnoceny analýzou společnosti Rietveld. Byla zjištěna směs krychlových (JCPDS 75-6866) a tetragonálních (JCPDS 37-0471) fází chalkopyritu s téměř totožnými difraktogramy. Obě fáze jsou nanokrystalické s velikostí 13 nm pro laboratorní a 7 nm pro průmyslové mletí. Pro stanovení spotřeby železa během syntézy byla použita metoda magnetometrie. Na základě magnetizačních dat odrážejících na čase závislou inkorporaci elementárního železa do chalkopyritové nanostruktury byla vyhodnocena kinetika syntézy. Z kinetických údajů byla stanovena rychlostní konstanta reakce k a také konverzní stupeň R. Vysoký stupeň konverze mechanochemické syntézy prováděné v laboratorní válcovně (R = 100 %), jakož i v průmyslové válcovně (R = 96 %) nabízí možnost rozšířit proces syntézy při přípravě tohoto perspektivního magnetického polovodiče. Ukázalo se, že metoda magnetometrie je účinným nástrojem pro sledování procesů syntézy, při nichž jsou obsaženy částice železa