Nanocrystalline materials based on titanium dioxide possess unique properties, including photocatalytic and antibacterial activities. Despite many approaches have already been utilized to fabricate and characterize pure and doped TiO2, a systematic description of its nanostructured samples depending on the synthesis method has not been presented yet. In this study, we shed new light on the process–structure relationships of nanocrystalline TiO2-based powders fabricated by extraction–pyrolytic, hydrothermal, and sol–gel techniques. The comprehensive analysis of the fabricated nanocrystalline TiO2-based powders with different anatase/rutile phase content is performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrothermal and sol–gel methods are also used to grow TiO2 particles doped with Cu and Er-Yb. The correlation between synthesis parameters (pyrolysis and annealing temperature) and properties of the produced materials is studied. Particular attention is paid to Raman spectroscopy and the detailed comparison of our obtained data with existing experimental and theoretical studies.

Printed circuit boards (PCBs) make up 3 to 5% of all electronic waste. The metal content of spent PCBs can reach 40%. They usually contain valuable metals, such as Ag, Au, and Pd, as well as other metals such as Cu, Sn, Pb, Cd, Cr, Zn, Ni, and Mn. However, the metallic part of a whole PCB is 40–60% including the Cu layers between the fiberglass–polymer layers. The paper describes the economics of the valuable metal (Ag, Au, Pd)-containing concentrate preparation from a raw PCB. We considered the influence of the pre-treatment method of PCBs before the extraction of valuable metals on the extraction self-cost change. The disintegration method is based on the high-energy impact of the particles of the material to be ground, thus causing the separation of the metallic components of the PCB. In the course of the work, single and double direct grinding using the method of disintegration was studied. For the calculation, the test batch of 10,000 kg of two types of PCB was taken for estimation of the self costs and potential profit in the case of complete valuable metals (Ag, Au, Pd) plus Cu extraction. It was shown that from 10,000 kg of studied PCB, it is possible to obtain 1144 and 1644 kg of metal-rich concentrate, which should be further subjected to electro-hydrochlorination for metals leaching. The novelty of this research lies in the fact that a technical and economic analysis has been carried out on a newly developed combined technology for processing electronic waste. This included mechanical processing and electrochemical leaching with the help of the active chlorine that is formed in situ. The real (not specially selected or prepared) waste PCBs were used for the process’s economical efficiency evaluation. The main findings showed that despite the high content of Cu in the studied PCBs, the commercial value was insignificant in relation to the total income from the Ag, Au, and Pd sale. A correlation was established between the self-cost decrease after separative disintegration of PCBs by metal content increase (by specific metals such as Au, Ag, Pd, and Cu) with the metal potential yield after extraction.

The development of environmentally friendly and energy-saving processes for recycling electronic waste (e-waste) is still relevant today. The research presented in this work relates to hydrometallurgy, namely, the electrochemical leaching of metals from e-waste under the action of alternating current (AC) into hydrochloric acid solutions of electrolytes, and can be used for leaching both noble and non-ferrous metals from secondary raw materials. The main object of the study was disintegrator-crushed mixed computer PCBs metal-rich powders with a particle size (d) of <90 µm. The impact of such leaching process parameters as temperature (Tel) and composition of the electrolyte solution, AC density (i) on the electrodes, experiment duration (tex) while maintaining a constant electrolyte temperature (60 °C, 70 °C, and 80 °C) on the metal (Au, Ag, Cu, Al, Ni, Pb, Sn, Ti, Zn, and Fe) leaching efficiency has been studied. In addition, under similar experimental conditions, but without external control of Tel, the kinetics of metal leaching from raw material powders obtained via PCBs single and double crushing in a disintegrator has been also presented. Comparison of raw material powders obtained from different batches of the source material showed both the variability of its chemical composition and the different kinetics of Au and Ag leaching under the same experimental conditions. The optimal conditions for pretreatment of the raw material obtained by single crushing in a disintegrator (CHCl = 6 mol·L−1, i = 0.88 A·cm−2, tex = 1 h, solid-to-liquid ratio—8.6 g·L−1 and without external control of Tel) were determined. It has been shown that this electrochemical pretreatment is accompanied by transition of only base metals into the electrolyte solution, making it possible to significantly reduce their concentration in the final solution. Under pretreatment conditions, the following degree of metal leaching (RMe) has been established: RCu = 98.2%, RAl = 62.8%, RNi = 53.4%, RPb = 93.2%, RSn = 98.0%, RTi = 88.5%, RZn = 61.6%, and RFe = 78.8%. As a result of a subsequent two-hour electrochemical treatment of a solid residue, the degree of leaching of gold and silver was 73.6% and 86.7%, respectively. The presented results provide a broader understanding of the possibility of using the proposed electrochemical hydrochlorination method for noble and base metals leaching from waste PCBs. The novelty and practical value of this research is a validation of the developed technology in laboratory conditions using the real batch of the PCBs. This approach may also be useful to researchers involved in the recycling of other types of secondary raw materials.

This paper presents the results of the leaching of metals from computer PCBs by electrochemical hydrochlorination using alternating current (AC) with an industrial frequency (50 Hz). Leaching was carried out with a disintegrator-crushed computer motherboard with a particle size (d) of <90 μm. In the course of the research, the leaching efficiency of metals including Fe, Sn, Mn, Al, Cu, Zn, Pb, Ni, Ti, Sb, Cr, Co and V was evaluated depending on process parameters, such as AC density, experiment duration, hydrochloric acid concentration in the electrolyte solution, solid/liquid ratio, electrolyte temperature, and the loading option of raw material (loading option 1 involving loading into the electrolyte solution, and loading option 2 involving loading into the filter containers attached to electrodes). The research results showed that AC superimposition significantly intensifies the leaching of metals. It was established that the complete leaching of metals including Al, Mn, Sn, Ti and Zn, under experimental conditions (loading option 2, CHCl = 6 mol·L−1, i = 0.80 A·cm−2, S/L = 8.6 g·L−1), is reached after 1.5 h, and that of Cu and Ni is reached after 2 h from the beginning of the experiment. At the same time, the degree of leaching of other metals after 2 h is Co-78.8%, Cr-84.4%, Sb-91.7%, Fe-98.9%, V-98.1% and Pb-5.1%. The paper also reports the results on the leaching of all abovementioned metals, as well as Ag and Pd, with disintegrator-crushed mixed computer PCBs with d < 90 μm and loading option 1.

Various metals and semiconductors containing printed circuit boards (PCBs) are abundant in any electronic device equipped with controlling and computing features. These devices inevitably constitute e-waste after the end of service life. The typical construction of PCBs includes mechanically and chemically resistive materials, which significantly reduce the reaction rate or even avoid accessing chemical reagents (dissolvents) to target metals. Additionally, the presence of relatively reactive polymers and compounds from PCBs requires high energy consumption and reactive supply due to the formation of undesirable and sometimes environmentally hazardous reaction products. Preliminarily milling PCBs into powder is a promising method for increasing the reaction rate and avoiding liquid and gaseous emissions. Unfortunately, current state-of-the-art milling methods also lead to the presence of significantly more reactive polymers still adhered to milled target metal particles. This paper aims to find a novel and double-step disintegration–milling approach that can provide the formation of metal-rich particle size fractions. The morphology, particle fraction sizes, bulk density, and metal content in produced particles were measured and compared. Research results show the highest bulk density (up to 6.8 g·cm−3) and total metal content (up to 95.2 wt.%) in finest sieved fractions after the one-step milling of PCBs. Therefore, about half of the tested metallic element concentrations are higher in the one-step milled specimen and with lower adhered plastics concentrations than in double-step milled samples.

Modern technologies for recycling electronic waste (e-waste) have high economic efficiency and environmental safety requirements. Among the existing technologies, hydrometallurgy is considered to be the most promising technology for e-waste recycling. Increasing attention paid to the chlorination method is associated with the complex recycling of low-grade ores containing noble metals and the raw materials of secondary polymetallic. In this paper, we propose a new scheme for leaching metals from computer printed circuit boards (PCBs) pre-crushed in a disintegrator: The processes of chlorine production and hydrochlorination are implemented in one reactor under the action of an alternating current (AC) of industrial frequency (50 Hz). Three fine fractions of raw material powders with particle size d < 90 µm, d = 90–180 µm, and d = 180–350 µm were used as research objects and the finest fraction of the raw material (d < 90 µm) was studied in more detail. It was found that complete leaching of gold is achieved from fractions of raw materials with a particle size d = 90–180 µm and d = 180–350 µm, containing 277 ppm and 67 ppm of the gold, respectively, at an experiment duration (tex) of 2 h, a current density (i) of 0.66 A·cm−2, and a solid/liquid (S/L) ratio of 8.6 g·L−1. Under the same conditions of the electrochemical leaching process from the fraction of raw materials with a particle size of d < 90 µm and a gold content of 824 ppm, the degree of metal leaching is 80.5%. At the same time, with an increase in particle size in the raw material fractions from d < 90 µm to d = 180–350 µm and a copper content in the raw material from 1.40% to 6.13%, an increase in the degree of its leaching from 81.6% to 95.2%, respectively, is observed. In the framework of the preliminary study presented in this work, for the finest raw material fraction with d < 90 μm the highest gold leaching degree (86.3%) was achieved under the following experimental conditions: tex= 4 h, CHCl = 6 M, i = 0.88 A·cm–2, S/L ratio—8.6 g·L–1 and the highest copper leaching degree (94.2%) was achieved under the following experimental conditions: tex = 2 h, CHCl = 6 M, i = 0.64 A·cm–2, and S/L ratio—2.9 g·L–1.

The significant increase in the demand for efficient electric energy storage during the past decade has promoted an increase in the production and use of Cd-containing batteries. On the one hand, the amount of toxic Cd-containing used batteries is growing, while on the other hand, Cd is on a list of critical raw materials (for Europe). Both of these factors call for the development of effective technology for Cd recovery from spent batteries. The present paper is aimed at providing a short review of the recent progress in Cd recovery from spent batteries. Statistical data from the past decade on the source of Cd, its global production, and Ni-Cd battery recycling are given in the introduction. A short overview of the pyro-and hydro-metallurgical methods of metal production is provided. Recent progress in Cd recovery by commercial methods during the past decade is reviewed.

Due to the unique properties and wide array of applications of nanocrystalline materials based on titanium dioxide, the study of new synthesis approaches remains relevant. In this study, within the framework of the extraction-pyrolytic method (EPM), we suggest using the mixtures of Ti- and Eu-containing organic extracts based on valeric acid as precursors for fabrication of nanocrystalline TiO2-based powders with different Eu content: 0.5 mol%, 5 mol%, and 50 mol%. The thermal behavior of individual metal-containing extracts and their mixture was studied by thermogravimetric analysis and differential scanning calorimetry (TGA–DSC). To characterize phase composition and morphology of produced materials, the X-ray diffraction (XRD) method and scanning electron microscopy (SEM) were used. Photoluminescence properties of Eu3+ ions in TiO2 nanocrystals have been studied. Photocatalytic activity of produced materials was tested in the reaction of methylene blue (MB) oxidation under UV-VIS irradiation. Correlation between synthesis parameters (Eu content and pyrolysis temperature) and properties of produced materials (phase composition, photoluminescence and photocatalytic properties) has been studied. It was demonstrated that the presence of a Eu-containing extract in the precursor mixture increases the anatase-to-rutile phase transformation temperature. The highest efficiency (degradation degree of MB 96%) was shown by TiO2 powder consisting of mixed polymorphs, anatase (main phase) and rutile, with 0.5 mol% Eu additive. It was shown that anatase-to-rutile phase transformation in TiO2:Eu3+ nanoparticles manifests in a degradation of Eu3+ luminescence intensity.

The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 powders. A titanium-containing precursor (extract) was prepared by liquid–liquid extraction using valeric acid C4H9COOH without diluent as an extractant. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), as well as the Fourier-transform infrared (FTIR) spectroscopy were used to determine the temperature conditions to fabricate TiO2 powders free of organic impurities. The produced materials were also characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The results showed the possibility of the fabrication of storage-stable liquid titanium (IV)-containing precursor, which provided nanocrystalline TiO2 powders. It was established that the EPM permits the production of both monophase (anatase polymorph or rutile polymorph) and biphase (mixed anatase–rutile polymorphs), impurity-free nanocrystalline TiO2 powders. For comparison, TiO2 powders were also produced by the precipitation method. The results presented in this study could serve as a solid basis for further developing the EPM for the cheap and simple production of nanocrystalline TiO2-based materials in the form of doped nanocrystalline powders, thin films, and composite materials.

The effect of 6 MeV gamma photons on thermally stimulated exoelectron emission (TSEE) spectra of MgO films was studied. The films were fabricated on Si/SiO2 substrates using the extraction-pyrolytic method. The crystalline structure and surface morphology of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). TSEE spectra of MgO films had emission peaks at about 450 oC and 525 oC. The area under the TSEE peaks increased after repeated TSEE measurements. In the case of gamma-irradiated films, the percentage increase in the area depended on the radiation dose, decreasing linearly with an increase in the radiation dose from 0 to 80 Gy. The results suggest that gamma radiation reduced the density of trapped electrons present in the as-grown MgO films or created competing hole traps that inhibited TSEE from the films.

Due to its to its optical, thermal, photocatalytic and electrophysical properties, nanocrystalline titanium oxide (TiO2) is widely used in various fields. In the present work, a series of pure and Gd-modified (0.5, 5, 50 mol%) TiO2 nanocrystalline powders were prepared by a novel synthesis approach – extraction-pyrolytic method (EPM). Metal containing extracts on the basis of valeric acid were used as precursors. Thermal behavior of produced individual and mixed precursors were investigated by thermogravimetric analysis (TGA) and high temperature differential scanning colometry (HDSC). Phase composition of pure and Gd-modified TiO2 powders were studied as a function of pyrolysis temperature (450o -850°C ) and gadolinium content by X-ray diffraction (XRD) method. Photocatalytic activity of produced powders was studied by photocatalytic degradation of methylene blue (MB) under UV/VIS light irradiation.

Interest in magnetic nanoparticles is primarily due to their practical use. In this work, for the production of nanocrystalline powders of pure and gadolinium doped iron oxides, the extraction-pyrolytic method (EPM) was used. As a precursor, either iron-containing extract (iron (III) caproate in caproic acid) or its mixture with gadolinium-containing extract (gadolinium (III) valerate in valeric acid) was used. The mixed precursor contained 0.5 mol %, 2.5 mol %, 12.5 mol %, 50 mol %, and 75 mol % gadolinium in relation to the iron content. The formation of iron oxide phases, depending on the preparation conditions, was investigated. According to the results obtained, it was demonstrated that the presence of more than 2.5 mol % gadolinium additive in the mixed precursor inhibits the magnetite-to-hematite transformation process during thermal treatment. Produced samples were characterized by XRD and SEM methods, and the magnetic properties were studied.

Alkaline nickel-cadmium batteries are among the most used industrial high-power sources. Despite stricter environmental requirements, nickel-cadmium batteries still remain as the main choice for highly reliable power sources for heavy-loaded equipment. Therefore, recovery of cadmium (Cd) from spent batteries is a challenge for the modern recycling industry, particularly as it displays high bio-toxicity. The present study describes a new green approach for Cd recovery from cadmium oxide (CdO). The paper discusses using a ternary chloride composition consisting of calcium, potassium and sodium chloride, thereby avoiding the release of Cd vapour from the reaction volume during the reduction reaction from CdO. For the protective slag layer during the reduction process (which occurs at 650 °C), a 0.515:0.0796:0.405 molar ratio of CaCl2:KCl:NaCl was chosen, with the aim of achieving a melting point at 483 °C. To describe phase and elemental composition of obtained products X-ray diffraction analysis and energy dispersive X-ray spectroscopy, respectively, were applied. Electron and optical microscopy were used for morphological observations. The presence of the metallic Cd was noted. During the reduction reaction, it was noted that slag separated into two parts: a protective upper layer and bottom layer. It was also noted that metallic Cd accumulated with increasing reaction time in the bottom part of the slag.

The effect of gamma irradiation on Gd2O3 films was studied using the thermostimulated exoelectron emission (TSEE) technique. The films were deposited on a glass and Si/SiO2 substrates using an extraction-pyrolytic method. Crystalline structure, chemical composition, film thickness and surface morphology were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films were irradiated by 10 MeV gamma photons and TSEE was measured from the irradiated films. It was found that gamma irradiation decreases TSEE intensity and the area below TSEE spectral curves. A linear correlation between the relative decrease in the area and the delivered dose was observed in a dose range of 0-10 Gy. These findings suggest that gamma radiation might decrease the density of trapped electrons present in the as-grown Gd2O3 films or create competing electron traps that inhibit TSEE from the films.

Due to its magnetic, electrical, absorption, and emission properties, nanoscale gadolinium oxide is widely used in various fields. In this research, nanocrystalline Gd2O3 powders and films on glass substrates have been produced by the extraction-pyrolytic method. X-ray diffraction analysis revealed the formation of single phase Gd2O3 with cubic crystal structure and the mean crystallite size from 9 to 25 nm in all produced materials. The morphology of samples has been characterized by scanning electron microscopy and transmission electron microscopy.

Noble metals supported on TiO2 (Degussa P25) modified with WO3 under the effect of feeding oxgen and ozone containing mixture to the reactor under UV-C irradiation were examined for their cataltic activit in thereaction of oxalic acid liquid phase oxidation. The samples were snthesized b extractive-proltic method b loading 4 wt.% WO3 and 1 wt.% of the active metal having particles size varing from 5 to 30 nm. The XPS, XRD, TEM and BET methods were emploed for their structural and chemical characterization. In the presence of oxgen under UV light the limiting step zero-order reaction rate of TiO2/WO3/Pt sample was highest among the tested catalsts and it was 2.3 times higher than that of the pure TiO2 under the same conditions. The increased activit of the composite catalsts was due to the more efficient separation of the electron-hole charge carriers generated during irradiation, which was combination from the beneficial effect of the WO3 and noble metal. Further, the effectiveness of the catalsts in regard to the photooxidation of oxalic acid in the presence of ozone is greater between 4-5 times for all tested samples. The highest activit under feeding of ozone was shown b TiO2/WO3/Pd that was ascribed to the highest ozone decomposition abilit of the palladium supported on TiO2 resulting in active oxgen atoms formation that facilitate the degradation of oxalic acid.

Titanium is widely used in specific applications due to its high strength, low density and good chemical stability. Despite it is one of the most abundant elements in the earth's crust, it is very expensive, because production of pure metallic titanium is very complex. Kroll process is the way how most of the titanium is produced nowadays. Shortages of this process are that it is batch process and it is very energy exhaustive, because titanium sponge material after reduction reaction needs complex post processing to isolate pure titanium. In this work we describe and experimentally investigate technology for Ti production from titanium tetrachloride using combined Kroll and electroslag process. Such process allows to achieve better reaction product separation by molten slag and process can potentially be continuous, thus technological process to produce metallic titanium can be significantly shortened.

In the present work, possibilities of the extraction–pyrolysis method (EPM) to produce FePt nanoparticles with the face-centered tetragonal (fct) phase were studied. A mixture of fine-disperse powder of carbonyl iron and n-trioctylammonium hexachloroplatinate [(С8Н17)3NH]2PtCl6 solution in toluene, preliminary produced by the solvent extraction method, is used as a precursor. Precursors with a different molar ratio of metals were used. The performed investigations show that as a result of pyrolysis in the air (Tpyr = 600°C, tanneal = 30 min), a FePt alloy with the fct phase is produced. Moreover, such phases as FePt3 and/or Fe3Pt with the cubic structure may be also present in the final products. The phase composition of the produced samples depends on the Fe:Pt molar ratio in the precursor. An increase of the fct phase part with the growth of the iron content from 40 to 60 mol% is observed. Also, with the Fe80%Pt20% molar ratio of the metals in the precursor, only the ordered fct phase along with a small amount of hematite and iron chloride exists in the produced sample. Magnetic measurements confirm the fct-FePt phase formation in all produced samples and evidence that the coercivity exceeds the value (3 kOe) at the 50 mol% Fe concentration in the precursor and significantly decreases with increasing the Fe concentration to 80 mol%.

The chemical synthesis is a leading route for the purposeful design of nanomaterials, whereas the tungsten oxides are employed in a variety of special applications. The production of nanomaterials by traditional synthetic methods is still a cumbersome multistep procedure. Here we propose an improved method to produce tungsten oxide nanoparticles via a pyrolytic process. A tungsten-containing precursor was prepared by liquid extraction using n-trioctylamine (C8H17)3N solution in toluene. We have shown that the conditions of thermal treatment of the W-based precursor determine the crystalline structure and nanomorphology of the final product. Monoclinic WO3 nanocrystallites are produced conducting the pyrolysis above 450 °C. The proposed method is a facile and versatile route to produce and control the phase composition and morphology of tungsten oxide-based nanomaterials.

Most common process for titanium production nowadays is Kroll process. This process has several drawbacks. Process is cyclical, and titanium comes out in sponge like form. This means that process is long, reaction is uncontrollable and requires post-processing of titanium sponge, which is energy consuming. In this work we present the idea to use Kroll process combined with electroslag process to produce titanium in continuous, more efficient process. Main idea is to use heated reactor where the initial reaction products (titanium tetrachloride and magnesium) are injected in liquid and gaseous phases, and reaction takes place above liquid slag in gaseous phase. Slag layer ensures titanium separation from unreacted magnesium and magnesium chloride, and other reaction waste products. Titanium droplets filtrate through the slag and is separated from the other fractions. In this paper we test the feasibility of this idea by studying the electroslag remelting of a titanium electrode in a specially prepared laboratory reactor. Chemical analysis is done to measure the composition of reaction products.