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Silver nanoparticles (Ag NPs) could be prepared by effective and simple biosynthesis by using plant extracts. Water extracts from Thymus serpyllum L., Thymus vulgaris L., and Sambucus nigra L. were used for a green synthesis of Ag NPs. Progress of the syntheses, the structure of Ag NPs and their antibacterial actiivity were followed by UV-Vis spectroscopy, TEM analysis and agar well diffusion method. UV-Vis analysis showed that the reactions performed with various plants extracts need different temperatures (60–90 °C) to synthesize Ag NPs. The NPs prepared were approx. 30 nm in size, but Ag NPs smaller than 10 nm were detected, too. Pure plant extracts without nanoparticles had no antibacterial activity. Of the Ag NPs-containing samples, only those prepared by using extract from Sambucus nigra L. showed antibacterial activity against Escherichia coli and Staphylococcus aureus. Green synthesis is a promising way to prepare NPs with biological activities.

The increasing demand for batteries forced the development of energy storage systems that rely on materials consisting of abundant elements in the Earth’s crust. Switching from Li+ to K+ as the main ionic charge carrier needs highly conducting potassium-bearing electrolytes to realize K+ ion batteries (PIBs). The knowledge gained from the design of Li-ion batteries (LIBs) and Na-ion batteries (NIBs) may conceptually inspire also the establishment of PIBs. Considering, for instance, the hexatitanates Na2Ti6O13, Li2Ti6O13, and H2Ti6O13, which were previously investigated as components for LIBs and NIBs, here we investigated ion dynamics in the K-analog K2Ti6O13. Ionic transport in polycrystalline samples of K2Ti6O13 was studied in a moisture-free atmosphere by broadband impedance spectroscopy in a temperature range from 20 °C to 450 °C. The current study aims at establishing a correlation between structural features of K2Ti6O13 and long-range ionic transport. As expected for K+ transport in K2Ti6O13 with its geometrically obstructed structure, the overall activation energy of ion transport in the ternary oxide takes a rather high value of 0.97(2) eV. Almost the same result (0.95(3) eV) is obtained for the migration activation energy, which we extracted from the analysis of crossover frequencies of the corresponding conductivity isotherms. By comparing our results with those of Na2Ti6O13 (0.82 eV), Li2Ti6O13 (0.65 eV), and H2Ti6O13, we clearly see how the size of the mobile cation correlates with both specific conductivities and activation energies. This comparison points to K+ being the main charge carrier in K2Ti6O13. It also helps in laying the foundations to derive the relevant structure-property relationships in this class of materials.

The presented study proposes a new potential biosorbent- Thymus serpyllum L. (wild thyme) plant, which showed to be highly efficient in rapid adsorption of Cu(II) and Pb(II) ions. Apart from biochars, that are commonly used for adsorption, here we report the direct use of native plant. The highest adsorption capacity for Cu(II) and Pb(II) ions (qe = 12.66 and 53.13 mg g-1, respectively) was achieved after 10 and 30 minutes, respectively. The combination of characterization methods (SEM/EDX, TGA, FT-IR, XPS and ζ-potential measurements) confirmed the combined adsorption mechanism consisting of the ion exchange at the lower Cu(II) and Pb(II) concentrations and the complexation and chelation at higher concentrations. Moreover, the Cu-laden plant has been shown to be an efficient antibacterial agent against the bacteria E. coli and S. aureus. Thus, the sustainable resource can be used both to treat wastewater and be used in the fight against microbes afterwards.

In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from copper, antimony, and sulfur precursors by high-energy milling for only 30 min in a planetary mill is reported. XRD confirmed the orthorhombic crystal structure of CuSbS2. The crystallite size of CuSbS2 calculated by LeBail refinement of the X-ray powder diffraction data was 25 nm. The nanocrystalline chalcostibite CuSbS2 was also confirmed by transmission electron microscopy. The purity of CuSbS2 was verified by Raman spectroscopy. The synthesized chalcostibite exhibits the specific surface area value of 2.4 m2g−1. UV–Vis spectroscopy showed the optical bandgap of CuSbS2 as 1.54 eV with wide range of absorption in visible region. Photoresponse of CuSbS2 was confirmed by I–V measurements under dark and light illumination. The proposed mechanochemical synthesis provides an alternative approach to prepare also other ternary semiconductor nanomaterials. CuSbS2 semiconductor nanocrystals have the potential to be used as light absorbers in photovoltaics.

Chalcopyrite CuFeS2, a semiconductor with applications in chemical sector and energy conversion engineering, was synthetized in a planetary mill from elemental precursors. The synthesis is environmentally friendly, waste‐free and inexpensive. The synthesized nano‐powders were characterized by XRD, SEM, EDX, BET and UV/Vis techniques, tests of chemical reactivity and, namely, thermoelectric performance of sintered ceramics followed. The crystallite size of ∼13 nm and the strain of ∼17 were calculated for CuFeS2 powders milled for 60, 120, 180 and 240 min, respectively. The evolution of characteristic band gaps, Eg, and the rate constant of leaching, k, of nano‐powders are corroborated by the universal evolution of the parameter SBET/X (SBET‐specific surface area, X‐crystallinity) introduced for complex characterization of mechanochemically activated solids in various fields such as chemical engineering and/or energy conversion. The focus on non‐doped semiconducting CuFeS2 enabled to assess the role of impurities, which critically and often negatively influence the thermoelectric properties.

This study demonstrates scalable mechanochemical synthesis of rhodostannite Cu2FeSn3S8 nanocrystals. On the contrary to the previous reports focused on the synthesis of stannite Cu2FeSnS4 reporting the rhodostannite impurity, we succeeded in preparing stannite-free product after milling. Pure elements were used for a solvent-free production in a batch of 100 g using an eccentric vibratory mill. The progress of the synthesis was monitored by X-ray diffraction and magnetometry, which both confirmed a successful reaction progress until 6 h of milling. However, further treatment (until 10 h) did not result in an improvement, as quite a high saturation magnetization (7.8 emu/g) and clearly evident diffraction at around 44° in the XRD pattern of the product due to the presence of ferromagnetic un-reacted iron with content slightly above 5% was evidenced. The product is sulfur- and tin-deficient, with crystallite size of around 12 nm. In-depth SEM/EDS analysis has shown the inhomogeneity of Fe distribution due to unfinished reaction. The bandgap of the produced material was 1.29 eV. The spark plasma sintering treatment resulted in complete consumption of non-reacted iron, but partial decomposition to stannite Cu2FeSnS4 was observed. The product is an intrinsic semiconductor with high electrical resistivity, and is therefore unsuitable for thermoelectric application. However, its thermal conductivity is low, thus it could be used as an electrically and thermally insulating material.

Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu

An effort to prepare different non-stoichiometric Cu

CuFeS

Twelve Cu-based ternary (Cu-Me

Herein, the room-temperature sulfuric acid leaching of copper smelter slag powder in the presence of potassium dichromate was investigated, resulting in the selective extraction of copper with its separation from zinc and iron. To enhance the extraction of copper, mechanical activation in the planetary ball mill and attritor was used. The Taguchi method was applied to determine the optimal conditions for both mechanical activation and leaching. For mechanical activation in the attritor, a rotation speed of 1200 rpm, ball-to-powder ratio of 40 and milling time of 75 min were ideal. Under these conditions, the specific surface area (SBET) could be increased from 1.7 m2/g, for the starting slag, to 59.4 m2/g. According to ANOVA, the most important factor is the rotation speed. For comparison, the slag was subjected also to planetary ball milling using the same conditions and a specific surface area of 116 m2/g was obtained. Leaching conditions that maximize copper recovery and, independently, copper selectivity, were also found. The maximum copper recovery was 87.3%, while the maximum copper selectivity was 97.9%. The most influential parameters in leaching were the concentration of K2Cr2O7 and the liquid-to-solid ratio. The copper selectivity is attributed to better solubility of chalcopyrite (CuFeS2) in comparison with zinc ferrite (ZnFe2O4) and fayalite (FeSiO4) containing the other metals. This study provides a statistical approach for planning the experiments of pretreatment and leaching to efficiently recover valuable metals from secondary raw resources in an environmentally interesting fashion by using low concentrations of leaching agents and mechanical pretreatment.

Zn-Fe alloys have been extensively investigated in this study with a view to their application as biodegradable bone implants. Biogenic element zinc is a very appropriate metal because of the ideal degradation rate compared to those of Mg and Fe. Studied alloys were made by compressing metallic powders in a content ratio of 100% Zn, Zn-1% Fe, Zn-2% Fe, Zn-5% Fe and Zn-10% Fe and sintering at 350 ​°C for 1 ​h. Prepared samples were examined by optical microscopy, SEM and XRD. Corrosion behavior, mechanical testing and hemocompatibility were observed subsequently. The electrochemical performance of such materials was studied in the simulated body fluids. The enhanced corrosion rate was observed for all samples after iron addition due to the micro-galvanic effect between the pure Zn and Zn11Fe intermetallic phase. The corrosion rate of the Zn-5% Fe alloyed sample was more than 20-times higher (2.89 mmpy) compared to the pure Zn. However, alloying with more than 5 ​wt % of iron diminished the mechanical performance of the material. Therefore, the performed mechanical and hemocompatibility tests showed acceptable biocompatibility of zinc and Zn-1% Fe and Zn-2% Fe samples.

International audience; In this work, Cu-based sulfides (chalcopyrite CuFeS2, mohite Cu2SnS3, tetrahedrite Cu12Sb4S13, mawsonite Cu6Fe2SnS8, and kesterite Cu2ZnSnS4) were synthesized by industrial milling in an eccentric vibratory mill to demonstrate the scalability of their synthesis. For a comparison, laboratory-scale milling in a planetary mill was performed. The properties of the obtained samples were characterized by X-ray diffraction and, in some cases, also by Mössbauer spectroscopy. For the densification of powders, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric (TE) characterization which created the core of this paper. A comparison of the figure-of-merit ZT, representative of the efficiency of thermoelectric performance, shows that the scaling process of mechanochemical synthesis leads to similar values as compared to using laboratory methods. This makes the cost-effective production of Cu-based sulfides as prospective energy materials for converting heat to electricity feasible. Several new concepts that have been developed involving combinations of natural and synthetic species (tetrahedrite) and nanocomposite formation (tetrahedrite/digenite, mawsonite/stannite) offer sustainable approaches in solid-state chemistry. Mechanochemical synthesis is selected as a simple, one-pot, and facile solid-state synthesis of thermoelectric materials with the capability to reduce, or even eliminate, solvents, toxic gases, and high temperatures with controllable enhanced yields. The synthesis is environmentally friendly and essentially waste-free. The obtained results illustrate the possibility of large-scale deployment of energy-related materials.

Indole-based chalcones have been identified as interesting compounds with anticancer properties. In the present study, we report the synthesis and evaluation of new 1-methoxyindole and 2-alkoxyindole chalcone hybrids as antiproliferative agents active against colorectal carcinoma cell line. Among the 19 investigated molecules, four inhibit the proliferation of colorectal cancer cells HCT-116 with IC50 values

A completely solid-state mechanochemical synthesis of silver nanoparticles overcoming the problem with water insolubility of lichen metabolites hampering their use for the classical green synthesis...

Mechanochemistry is a multidisciplinary branch of science and has significantly developed within the last few years. In the Department of Mechanochemistry at the Institute of Geotechnics of Slovak Academy of Sciences in Kosice, Slovakia, the mechanochemical synthesis of advanced nanomaterials, namely chalcogenides and oxides, applicable in energy industry is performed. Furthermore, the treatment of waste, synthesis of antibacterially active nanoparticles, and performing organic reactions using mechanochemistry have been in the spotlight. The possibility to up-scale these processes using vibratory ball mill in collaboration with TU Clausthal in Germany has been successfully applied. These advancements are briefly reviewed in this paper.

The large-scale mechanochemical reduction of binary sulfides chalcocite (Cu2S) and covellite (CuS) by elemental iron was investigated in this work. The reduction of Cu2S was almost complete after 360 min of milling, whereas in the case of CuS, a significant amount of non-reacted elemental iron could still be identified after 480 min. Upon application of more effective laboratory-scale planetary ball milling, it was possible to reach almost complete reduction of CuS. Longer milling leads to the formation of ternary sulfides and oxidation product, namely cuprospinel CuFe2O4. The rate constant calculated from the magnetometry measurements using a diffusion model for Cu2S and CuS reduction by iron in a large-scale mill is 0.056 min−0.5 and 0.037 min−0.5, respectively, whereas for the CuS reduction in a laboratory-scale mill, it is 0.1477 min−1. The nanocrystalline character of the samples was confirmed by TEM and XRD, as the produced Cu exhibited sizes up to 16 nm in all cases. The process can be easily scaled up and thus copper can be obtained much easier from refractory minerals than in traditional metallurgical approaches.

The presented study proposes a new potential biosorbent- Thymus serpyllum L. (wild thyme) plant, which showed to be highly efficient in rapid adsorption of Cu(II) and Pb(II) ions with higher adsorption capacity towards Pb(II) ions. Apart from biochars, that are commonly used for adsorption, here we report the direct use of native plant. The influence of different parameters (pH, contact time, adsorbent dosage) on the adsorption process as well as the adsorption in a binary system of selected metal contaminants was examined. The highest adsorption capacity for Cu(II) ions (qe = 12.66 mg g− 1) was achieved after 10 minutes of adsorption at 16 g L− 1 adsorbent dosage at natural pH. The highest obtained adsorption capacity for Pb(II) ions was 53.13 mg g− 1 after 30 minutes at 12 g L− 1 adsorbent dosage at unadjusted pH. The combination of characterization methods (SEM/EDX, TGA, FT-IR, XPS and ζ-potential measurements) were applied to estimate the removal mechanism during the adsorption of Cu(II) and Pb(II) ions on the plant biosorbent surface. The characteristic shifts were observed in the thermogravimetric curves and FT-IR spectra and together with the changes of pH during adsorption process confirmed the combined adsorption mechanism consisting of the ion exchange at the lower Cu(II) and Pb(II) concentrations and the complexation and chelation at higher contaminants’ concentrations.

Ternary wittichenite Cu3BiS3 nanocrystals were prepared mechanochemically using a planetary ball mill from elemental copper, bismuth and sulfur in a stoichiometric ratio in only 5 min. The orthorhombic wittichenite Cu3BiS3 was nanocrystalline with an approximate crystallite size of 38 nm ± 9 nm, as confirmed by Rietveld refinement. The nanocrystalline character of orthorhombic Cu3BiS3 was also proven by transmission electron microscopy. The measured Raman spectrum confirmed the formation of pure wittichenite Cu3BiS3. The morphology characterization demonstrated the homogeneity of the sample. The value of the specific surface area for pure mechanochemically prepared Cu3BiS3 after 5 min was 2.7 m2g−1. The optical properties were investigated using UV–Vis absorption and micro-photoluminescence spectroscopy. From the absorption UV–Vis spectrum, the value of the bandgap energy was determined to be 1.52 eV, which creates an assumption for the use of wittichenite Cu3BiS3 in photovoltaic applications. The optoelectrical properties of the prepared Cu3BiS3 nanocrystals were verified by current–voltage measurements in the dark and under white light illumination. The photocurrent increased by 26% compared to the current in the dark at a voltage of 1 V. The achieved results confirmed a very fast and efficient way of synthesizing a ternary wittichenite Cu3BiS3, which can be used for applications in solar cells.

An efficient eco-friendly one-step mechanochemical synthesis of indole hybrid chalcones via the Claisen–Schmidt condensation of 1-methylindole-3-carboxaldehyde with various substituted acetophenones is described using liquid assisted grinding in a high-energy ball mill. The notable advantages of the present method are small organic solvent required (100 μL ethanol) and mainly shorter reaction time (15–60 min) as compared to the conventional method. Antiproliferative activity of synthesized chalcones was studied on several human cancer cell lines (MCF-7, HeLa, A549, MDA-MB-231, HCT116) and non-cancer lines (Cos-7 or BJ-5ta). 3,4,5-Trimethoxyphenyl 3g, 2,5-dimethoxyphenyl 3h, and 2,4,5-trimethylphenyl 3j chalcones showed considerable cytotoxicity, particularly, chalcones 3h and 3j were identified as the most potent and selective anticancer agents with IC50 values 7.9 and 6.6 μM, respectively, against the colon cancer HCT116 cell line.

Strontium ferromolybdate, Sr

Biodegradable metallic implants are materials that serve as a temporary implants and scaffolds. They degrade directly in vivo and therefore eliminate need for secondary surgical intervention. They are often made of metals such as magnesium, iron, zinc and can be modified by coating with the inorganic or polymeric layer. In this work iron-based biomaterial was prepared and modified with polymeric (polyethyleneimine, PEI) layer. Its degradation behavior was studied under conditions of simulated body fluids at 37 ± 0.2 °C in the form of static immersion tests. It has been shown that the surface modification caused an acceleration of degradation of the material and also had an influence on the corrosion mechanism.

Three immobilized polysaccharide chiral stationary phases, Chiralpak IA, Chiralpak IB and Chiralpak IC, were used for the study of enantioseparation of 36 derivatives of natural indole phytoalexins, in most cases bioactive, including racemic spirobrassinin, 1-methoxyspirobrassinin and 1-methoxyspirobrassinol methyl ether. Almost all analytes were baseline resolved at least on two different polysaccharide columns in normal phase mode. The effects of mobile phase composition, the analyte structure and the column temperature on the retention and enantioseparation were investigated. Evaluation of the corresponding thermodynamic parameters using van´t Hoff plots (ln k versus 1/T) in the temperature range -15 to 50 °C indicated that separations were enthalpy controlled in most cases, but some entropy controlled separations were also observed. Moreover, unusual phenomenon, an increase retention with increasing temperature accompanied with increased resolution was observed on the Chiralpak IC column. The elution order of enantiomers was determined in some cases and reversed elution order was also observed.

In the present study, a quick and environmentally friendly approach has been developed for the synthesis of CuS nanocrystals of different shape with antibacterial activity. The process is completed...

Out of many functionalities of zinc oxide, its magnetic properties are only sparsely explored. Herein we report on the evolution of ferromagnetism of undoped ZnO nanoparticles, depending on the zinc source used for the synthesis. We started from mechanochemical synthesis of phase pure nanocrystalline hydrozincite, Zn5(CO3)2(OH)6 (ZnHC) by milling a mixture comprising either Zn(NO3)2·6H2O or ZnCl2, and Na2CO3 for 10 min. Zinc oxide nanoparticles with specific surface over 70 m2/g were obtained by subsequent heating of ZnHC up to 300 °C. Ferromagnetism was observed only for ZnO nanoparticles derived from Zn(NO3)2, while those from ZnCl2 were conventionally diamagnetic. X-ray photoelectron, Raman, as well as electron paramagnetic resonance spectrograms consistently showed significantly higher concentration of oxygen vacancies in the Zn(NO3)2-derived ZnO. We also referred to the difference in the charging states of oxygen vacancies by detailed observation of EPR spectra. Since the formation of ZnO from ZnHC is topotactic, the difference in the lattice imperfection was discussed in terms of the hydration energy of the coexisting NO3− or Cl− anion. The present simple mechanochemical – thermal procedure offers a facile method for obtaining well-dispersed active ZnO nanoparticles. More importantly, the new synthesis method offers possibility of controlling their magnetic properties by choosing anionic species of the starting zinc source.

CuFeS2/TiO2 nanocomposite has been prepared by a simple, low-cost mechanochemical route to assess its visible-light-driven photocatalytic efficiency in Methyl Orange azo dye decolorization. The structural and microstructural characterization was studied using X-ray diffraction and high-resolution transmission electron microscopy. The presence of both components in the composite and a partial anatase-to-rutile phase transformation was proven by X-ray diffraction. Both components exhibit crystallite size below 10 nm. The crystallite size of both phases in the range of 10–20 nm was found and confirmed by TEM. Surface and morphological properties were characterized by scanning electron microscopy and nitrogen adsorption measurement. Scanning electron microscopy has shown that the nanoparticles are agglomerated into larger grains. The specific surface area of the nanocomposite was determined to be 21.2 m2·g−1. Optical properties using UV-Vis and photoluminescence spectroscopy were also investigated. CuFeS2/TiO2 nanocomposite exhibits strong absorption with the determined optical band gap 2.75 eV. Electron paramagnetic resonance analysis has found two types of paramagnetic ions in the nanocomposite. Mössbauer spectra showed the existence of antiferromagnetic and paramagnetic spin structure in the nanocomposite. The CuFeS2/TiO2 nanocomposite showed the highest discoloration activity with a MO conversion of ~ 74% after 120 min irradiation. This study has shown the possibility to prepare nanocomposite material with enhanced photocatalytic activity of decoloration of MO in the visible range by an environmentally friendly manner

In this work, it is demonstrated that visible-light photocatalytic activity for degrading methyl orange (MO) could be improved by co-milling of TiO2 (Degussa P25) with thiourea. The photocatalysts have been prepared by combined mechanochemical/thermal synthesis. Structures and morphology of the as-prepared TiO2 nanoparticles were characterized by X-ray powder diffraction, N2 adsorption–desorption isotherms, UV–Vis diffuse reflectance spectroscopy and scanning electron microscopy. It is shown that co-milling of TiO2 with thiourea favours formation of brookite phase and it results in the occurrence of more porous structures. The optical properties are modified and the band gap energy values of the samples become smaller, when thiourea is introduced. Ball-milled samples show better photocatalytic activities during oxidative discolouration of MO than that of the initial TiO 2. The discolouration degree is above 99% for ball-milled TiO2 /thiuourea nanoparticles, while it is 2% for pure and 15% for ball-milled TiO2 .

Chalcopyrite CuFeS2, a semiconductor with applications in chemical sector and energy conversion engineering, was synthetized in a planetary mill from elemental precursors. The synthesis is environmentally friendly, waste‐free and inexpensive. The synthesized nano‐powders were characterized by XRD, SEM, EDX, BET and UV/Vis techniques, tests of chemical reactivity and, namely, thermoelectric performance of sintered ceramics followed. The crystallite size of ∼13 nm and the strain of ∼17 were calculated for CuFeS2 powders milled for 60, 120, 180 and 240 min, respectively. The evolution of characteristic band gaps, Eg, and the rate constant of leaching, k, of nano‐powders are corroborated by the universal evolution of the parameter SBET/X (SBET ‐specific surface area, X‐crystallinity) introduced for complex characterization of mechanochemically activated solids in various fields such as chemical engineering and/or energy conversion. The focus on non‐doped semiconducting CuFeS2 enabled to assess the role of impurities, which critically and often negatively influence the thermoelectric properties., Energy materials: The parameter SBET /X (SBET – specific surface area, X – crystallinity degree) was applied to characterize surface and bulk changes in the mechanochemically synthesized chalcopyrite CuFeS2. The dependence of the rate constant of chemical leaching k as well as the optical band gap Eg on this parameter illustrates its general character applicable in such diverse fields like chemical engineering and semiconductor science.

In this paper the mechanochemical reduction of binary sulphides chalcocite (Cu2S) and covellite (CuS) by elemental iron wereinvestigated. The composition and properties of nano-powders prepared by high-energy milling were analyzed by X-ray diffraction,X-ray photoelectron spectroscopy and magnetic measurements. The XRD results showed that in case of chalcocite Cu2S the reactiontakes place until 360 minutes, as no elemental iron, could be identified afterwards. In case of covellite CuS, after 480 minutes of mechanochemicalreduction, a significant amount of non-reacted elemental iron could still be observed. The investigation of magneticproperties reveals significant decrease of saturation magnetization as a result of milling. XPS results showed a significant surfaceoxidation in both systems. Unlike the conventional high-temperature reduction of chalcocite and covellite, the mechanochemicalreduction is fast and ambient temperature and atmospheric pressure are sufficient for its propagation.

Apart from coal fly ash discussed in previous chapter, there are other by-products related to technological operations for which mechanochemistry can be efficiently used. Namely mechanochemical treatment of municipal solid waste incineration fly ash has been investigated in many studies. In addition, the high-energy ball milling procedure has been applied for the medical solid waste incineration fly ash, incineration bottom ash and palm oil fuel ash. Mechanochemical treatment leads to an efficient stabilization of heavy metals in the ash and decomposition of toxic polyhalogenated compounds (e.g., dioxins) present there. Further applications of mechanochemically treated miscellaneous ash in composites, metals recovery, or nanoparticles production are reviewed here.

Metallurgical waste is another very common type of technogenic waste. It includes metallurgical slags, tailings and other specific waste (e.g., AlP fumigation residue). The glassy state of blast furnace slag (the most common representative of the metallurgical slags) can serve as a source of silicon, but also of heavy metals, which can be efficiently leached out upon the assistance of high-energy ball milling. Due to milling, tailings can be embedded into composites with other waste materials (e.g., fly ash).