Precious Metals Research Articles

Age and petrogenesis of the Madi intrusion in the Huashi area, northern margin of the North China Craton: Implications for magma evolution and Nb–Ta mineralization

Although the mineralization of rare earth elements (REEs) and rare metals is intimately associated with the extreme fractionation of granitic magmas, the metallogenic intrusions of many granite-hosted Nb–Ta deposits have undergone fluid–melt interaction. Nevertheless, the precise mechanisms by which fluid–melt interaction influences mineralization remain poorly understood. The present investigation examines the issues of the fluid–melt interaction in highly fractionated granites with Nb–Ta mineralization, utilizing data from the newfound Huashi deposit in the northern margin of the North China Craton (NNCC). The Huashi Nb–Ta–Rb–Li deposit hosted in the Madi intrusion consists of two lithologies that have evolved continuously, namely medium–fine grained granite (MGG) in the lower section and alkali-feldspar granite (AG) at the top. The ages of the MGG and AG were determined using LA–ICP–MS columbite U–Pb dating, yielding values of 182.9 ± 1.7 Ma and 184.7 ± 1.3 Ma, respectively. The Madi intrusion has high SiO2, Al2O3, and total alkali contents, along with low CaO, MgO, MnO, and TFe2O3 contents and high Al2O3 / (CaO + Na2O + K2O) (A/CNK) values, classifying it as highly peraluminous granite with a high-K calc-alkaline affinity. Additionally, the intrusion also exhibits enrichment in Rb, U, Th, and Nb alongside significant depletion in Sr, Ba, Ti, Eu, and P, with a noticeable tetrad effect of REEs. The investigation of mica and feldspar minerals in the Madi intrusion using electron probe microanalysis (EPMA) indicates that the mica is mainly zinnwaldite, while the plagioclase belongs to albite. In summary, the Madi intrusion exhibits a highly I-type fractionated granite affinity. The extreme fractionation, intense fluid–melt interaction, and hydrothermal alteration of the intrusion contribute to the formation of the Huashi deposit.

Study the Potential of Mineral Ceramics Based on Aluminium Oxide in Replacing Metal Alloys

Modern metal alloys used in the tooling industry often consist of expensive and rare metals, impacting affordability and sustainability. This research explores the potential of mineral ceramics, mainly composed of readily available aluminum oxide (Al2O3), as an alternative for high-performance engineering ceramics. This research highlights the advantages and disadvantages of mineral ceramics over various metal alloys. Further exploration could refine properties and expand industrial adoption, contributing to a more responsible and efficient materials landscape.

Effects of Mixed Metal Exposure on MRI Metrics in Basal Ganglia.

Welding fumes contain various metals. Past studies, however, mainly focused on Manganese (Mn)-related neurotoxicity. This study investigated welding-related mixed metal exposure effects on MRI metrics in the basal ganglia (BG) and their dose-response relationship. Subjects with (N = 23) and without (N = 24) a welding exposure history were examined. Metal exposure was estimated with exposure history questionnaire and whole blood metal levels. T1 (weighted-intensity and relaxation time; estimates of brain Mn accumulation), diffusion tensor imaging [Axial (AD), mean (MD), radial diffusivity (RD), and fractional anisotropy (FA); estimates of microstructural differences] metrics in BG [caudate nucleus, putamen, and globus pallidus (GP)] and voxel-based morphometry (for volume) were examined and related with metal exposure measures. Compared to controls, welders showed higher GP R1 (1/T1; p = 0.034) but no differences in blood metal and T1-weighted (T1W) values in any ROIs (p's > 0.120). They also had higher AD and MD values in the GP (p's < 0.033) but lower FA values in the putamen (p = 0.039) with no morphologic differences. In welders, higher blood Mn and Vanadium (V) levels predicted higher BG R1 and T1W values (p's < 0.015). There also were significant overall metal mixture effects on GP T1W and R1 values. Moreover, GP AD and MD values showed non-linear associations with BG T1W values: They increased with increasing T1W values only above certain threshold of T1 values. The current findings suggest that Mn and V individually but also metal mixtures jointly predict GP T1 signals that may in turn contribute to altered DTI metrics in the BG after certain exposure threshold levels.

Photodriven Ammonia Synthesis from Manganese Nitrides: Photophysics and Mechanistic Investigations.

Ammonia synthesis from N,N,O,O-supported manganese(V) nitrides and 9,10-dihydroacridine using proton-coupled electron transfer and visible light irradiation in the absence of precious metal photocatalysts is described. While the reactivity of the nitride correlated with increased absorption of blue light, excited-state lifetimes determined by transient absorption were on the order of picoseconds. This eliminated excited-state manganese nitrides as responsible for bimolecular N-H bond formation. Spectroscopic measurements on the hydrogen source, dihydroacridine, demonstrated that photooxidation of 9,10-dihydroacridine was necessary for productive ammonia synthesis. Transient absorption and pulse radiolysis data for dihydroacridine provided evidence for the presence of intermediates with weak E-H bonds, including the dihydroacridinium radical cation and both isomers of the monohydroacridine radical, but notably these intermediates were unreactive toward hydrogen atom transfer and net N-H bond formation. Additional optimization of the reaction conditions using higher photon flux resulted in higher rates of the ammonia production from the manganese(V) nitrides due to increased activation of the dihydroacridine.

Gold and Gold Alloys Electropolishing in Choline Chloride-Glycerol Deep Eutectic Solvents

Electropolishing (EP) is a finishing technique used to reduce the roughness of metallic surfaces while enhancing their brightness. This process enables the treatment of complex shaped parts and reduces processing time compared to conventional mechanical polishing methods. Electropolishing of precious metals typically requires the use of electrolytes containing cyanides and other toxic compounds, which reduces its attractiveness from an industrial perspective. Deep Eutectic Solvents (DES) are emerging as a good alternative for the chemical and electrochemical dissolution of valuable metals, like gold, silver and copper. However, their use in the specific context of electrochemical polishing of precious alloys has not been considered so far. This work aims to evaluate the effectiveness of choline chloride-based DES in electropolishing 18K gold alloys. Their performance will be assessed in terms of roughness reduction, brightness enhancement and color preservation, all characteristics associated with the presence of a uniform dissolution.

Niobium Interlayer Coating: Is it a Practical Approach to Tune the Protective Pt Loading in PEM Water Electrolyzers?

Proton exchange membrane (PEM) water electrolysis is a pioneering and promising method for sustainable green hydrogen generation. However, the high cost of PEM water electrolyzer components poses a significant barrier to the commercialization and widespread application of this technology. In this research, a novel Niobium-Platinum coating is developed for the porous transport layer (PTL) to reduce the precious metal loading. Niobium (Nb)-based coating was applied as an interlayer between Pt and titanium (Ti) felt substrates to increase the adhesion of Pt. For this study, pulsed laser deposition (PLD) technique was applied for the first time to coat Nb and Pt multilayers onto Ti felt substrates. The results demonstrate that incorporating a Nb coating as an interlayer lead to reducing the Pt loading, which holds promise for the practical application of PTLs in PEM water electrolyzers.

Mineral policy and sustainable development goals: Volatility forecasting in the Global South's minerals market

This paper aims to evaluate the volatility of precious metals, specifically Palladium, Gold, and Platinum, within the context of the global minerals market. The research focuses on understanding the price dynamics of these metals and their implications for sustainable development, particularly in the Global South. The study employs a comprehensive approach, utilizing advanced machine learning and deep learning models such as GRU, Huber, Lasso, LSTM, Random Forest, Ridge Regression, SVM, ANN, and XGBoost. These models are assessed based on their forecasting accuracy for different time horizons, using metrics such as RMSE and MAPE. The findings reveal that the ANN, XGBoost, and LSTM models exhibit robust performance in forecasting the volatility of precious metals across various time horizons. The research highlights the unique volatility patterns of each metal and underscores the effectiveness of machine learning techniques in capturing these dynamics. The study acknowledges limitations such as the exclusion of macroeconomic and geopolitical factors in the forecasting models. Future research is suggested to integrate these factors to enhance forecasting accuracy. The study's findings are pivotal for investors, policymakers, and market regulators, especially in the context of the Global South and sustainable development. The research offers valuable insights for risk management strategies, investment planning, and policy formulation aimed at promoting market stability and sustainable economic growth. The study emphasizes the importance of selecting appropriate forecasting models based on specific time horizons and market requirements.

Upcycling the Spent Graphite Anode Into the Prelithiation Catalyst: A Separator Strategy Toward Anode-Free Cell Prototyping.

The substantial manufacturing of lithium-ion batteries (LIBs) requires sustainable, circular, and decarbonized recycling strategies. While efforts are concentrated on extracting valuable metals from cathodes using intricate chemical process, the direct, efficient cathode regeneration remains a technological challenge. More urgently, the battery supply chain also requires the value-added exploitation of retired anodes. Here, a "closed-loop" approach is proposed to upcycle spent graphite into the prelithiation catalyst, namely the fewer-layer graphene flakes (FGF), upon the exquisite tuning of interlayer spacing and defect concentration. Since the catalytic FGF mitigates the delithiation energy barrier from calcinated Li5FeO4 nanocrystalline, the composite layer of which cast on the polyolefin substrate thus enables a customized prelithiation capability (98% Li+ utilization) for the retired LiFePO4 recovery. Furthermore, the hydrophobic polymeric modification guarantees the moisture tolerance of Li5FeO4 agents, aligning with commercial battery manufacturing standards. The separator strategy well regulates the interfacial chemistry in the anode-free pouch cell (LiFePO4||Cu), the prototype of which balances the robust cyclability, energy density up to 386.6Wh kg-1 as well as the extreme power output of 1159.8W kg-1. This study not only fulfills the sustainable supply chain with graphite upcycling, but also establishes a generic, viable protocol for the anode-free cell prototyping.

Enhancing Oxygen Evolution Reaction Performance with rGO/CoNi-Prussian Blue-Derived Oxyhydroxide Nanocomposite Electrocatalyst: A Strategic Synthetic Approach.

Electrochemical water splitting is a promising approach in the development of renewable energy technologies, providing an alternative to fossil fuels. It has attracted considerable attention in recent years. The benchmark materials used in water splitting are precious metals that are expensive and scarce. Therefore, this work proposes a strategic electrochemical synthesis of a reduced graphene oxide and cobalt-nickel hexacyanoferrate (rGO/CoNiHCF)-derived composite (rGO/CoNiPBd-OOH) to achieve optimized OER performance. The optimum rGO/CoNiHCF was fabricated with the Co:Ni precursors in a 3:1 ratio with a ferricyanide solution of pH = 1.0. Using an alkaline electrochemical treatment, the well-distributed globular particles of CoNiHCF over rGO sheets were converted into layered frameworks of metallic (oxy)hydroxide species, giving the final rGO/CoNiPBd-OOH nanocomposite. This nanocomposite presented favorable kinetic activity resulting in a Tafel slope of 33 mV dec-1, while rGO, CoNiPBd-OOH, and RuO2 exhibited slopes of 80, 47, and 51 mV dec-1, respectively. Although the benchmark RuO2 electrocatalyst showed a lower overpotential (240 mV dec-1) at a current density of 10 mA cm-2, the rGO/CoNiPBd-OOH performed well with an overpotential of 346 mV, combined with superior stability compared to CoNiPBd-OOH and RuO2, maintaining a current density of 10 mA cm-2 for 15 h with an overpotential loss of 6.92%. This work successfully presents an "all-electrochemical" synthesis of a rGO/CoNiHCF-derived material with remarkable electrocatalytic activity for OER assisted by a strategic preparation methodology, which helped to understand the influence of synthetic parameters and choose their conditions to achieve the optimum OER performance.

Geochemical and mineralogical characterization and resource potential of the Namib Pb-Zn tailings (Erongo Region, Namibia)

In Southern Africa, historic mining and mineral processing of base metal deposits have almost exclusively focussed on the extraction of major metals, leading to the loss of remaining valuable raw materials into tailings dumps and waste rock piles. At the Namib Pb-Zn mine (Erongo Region, Namibia), historic base metal tailings deposits are present as unreclaimed exposed waste piles. The tailings comprise silt- (fraction A: d50 = 25 to 48 μm) to sand-sized (fraction B: d50 = 86 to 185 μm; fraction C: d5o = 210 to 230 μm) material and contain major concentrations of base metals (Pb av. 1.15 mass%, Zn av. 3.20 mass%), S (av. 9.95 mass%), as well as lower values of other metals (Cu av. 490 μg/g, Cd av. 133 μg/g, Ag av. 22 μg/g), and critical elements like Sb (av. 14.7 μg/g) and In (14.3 μg/g). Former mineral processing only targeted the extraction of galena and sphalerite. As a consequence, qualitative mineralogical composition of the tailings is similar to that of the primary ore. Ca-Fe-Mg(-Mn) carbonates, quartz, micas, chlorite, minor graphite, magnetite, and rare parisite relate to the former host rock and gangue matrix, whereas Fe-rich sphalerite, galena, magnetite, pyrite with minor pyrrhotite, rare arsenopyrite, marcasite, cassiterite, and accessory scheelite are original constituents of the primary ore. Reprocessing of such a material would be challenging, but a mixed Pb-Zn concentrate enriched in Cd and Ag might be obtained. In future, possible reprocessing of Namib tailings and associated disposal of wastes into an appropriately designed repository would not only generate valuable metal commodities, but such activities would also eliminate a major metal pollution source from the local environment.

Evaluation of heavy metals and their potential risk to human health from seafood in Escravos Estuary, Southern Nigeria

In this study, we investigated the levels of heavy metals in sediment, shrimps, silver catfish and their potential bioaccumulation, trophic transfer and the associated risk to human health from the Escravos estuary in southern Nigeria. The values of heavy metals in shrimps and silver catfish were disproportionately higher than the allowable limits for seafood, with values in the gills and the rest of the fish higher than those of the muscle, liver and gonads. Furthermore, the increased BSAF for Cd, Cr and Cu in the study, underscore the uptake of metals from sediments into shellfish. High EDI and HR values from silver catfish for adults and children indicate immediate health risks, with the values for children considerably high, emphasizing the urgent need for regulatory measures and continuous monitoring of seafood from the estuary to protect the health of coastal population within the subregion.

A Combined Physical-Mechanical and Hydrometallurgical Approach for Recovering Valuable Metals from Spent Lithium-ion Batteries

In this work, the chemical composition of electrode materials from two samples of lithium-ion batteries (LiB) is comprehensively investigated. The material balance of the physical and mechanical processing of the LiBs mixture is determined. The developed dry process scheme made it possible to extract the following components (wt.%): 15.6 plastic (ABS), 1.89 electronic materials (PP), 59.1 black mass (three types), 6.43 plastic (PVC), 2.97 Al, 6.31 Cu and 7.1 magnetic fraction (Fe). The thermodynamics of reductive leaching of LiCoO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in the H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;-HCOOH system was studied. It was calculated that the Gibbs energy of the leaching reaction at 363 K is -327.4 kJ/mol, the equilibrium constant is 2.02×10&amp;lt;sup&amp;gt;44&amp;lt;/sup&amp;gt;. All these factors showed the potential of using formic acid as a reducing agent instead of the commonly used hydrogen peroxide solution. It is known to be unstable, since when the solution is heated from 20 to 50&amp;lt;sup&amp;gt;0&amp;lt;/sup&amp;gt; C, the decomposition of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; increases 20 times, and the presence of copper sulfate, which usually accompanies the decomposition of the black mass in a sulfuric acid medium, leads to the destruction of 76% of hydrogen peroxide. Therefore, from a practical point of view, it was of interest to study the kinetics of cobalt dissolution from the cathode material in the H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;-HCOOH system. It was shown that the Crank-Ginstling-Braunstein equation agrees satisfactorily with the experimental data, which indicates intra-diffusion limitation of dissolution. The activation energy was determined. The optimal composition and conditions of the leaching solution for dissolving cobalt, lithium and associated transition metals from the black mass were determined. The thermodynamics and kinetics of dissolution of Ag, Au and Pd from electrode materials in a bromide-bromine solution were also studied.

Estimation of the effectiveness of geological exploration projects for base and precious metals, completed in 2023 at the expense of the Russian Federal budget

Estimation of the effectiveness of geological exploration projects for base and precious metals, completed in 2023 at the expense of the Russian Federal budget

Separation of Co(II), Mn(II), and Ni(II) by solvent extraction with Cyanex 272 and D2EHPA from the sulfuric acid leaching solution of spent lithium-ion batteries

Spent lithium-ion batteries contain valuable metals such as cobalt, lithium, manganese and nickel. Smelting reduction of spent LIBs at high temperature results in metallic alloys. Therefore, it is necessary to recover the valuable metal ions present in the sulfuric acid leaching solutions of the metallic alloys. In this work, solvent extraction experiments were performed to separate the three metal ions, Co(II), Mn(II) and Ni(II) present in the leaching solutions of the metallic alloys. Synthetic sulfate solutions were prepared and commercial organophosphorous extractants were employed. First, both Co(II) and Mn(II) were completely extracted in one stage by using 40% saponified 0.3 M Cyanex 272, leaving Ni(II) in the raffinate. The small amount of Ni(II) co-extracted into Cyanex 272 was removed by two stages of cross-current scrubbing using pure CoSO4 solution. The effect of pH and CoSO4 concentration of the scrubbing solution on the scrubbing of Ni(II) was investigated. The Co(II) and Mn(II) present in the scrubbed Cyanex 272 were completely stripped by 0.05 M H2SO4 solution. Batch simulation experiments for the three stage of counter-current extraction with 1 M D2EHPA verified that Mn(II) and Co(II) were completely separated by selective extraction of Mn(II) into D2EHPA, leaving Co(II) in the raffinate. By consecutive extraction with Cyanex 272 and D2EHPA, pure solutions of Co(II), Mn(II) and Ni(II) with purity higher than 99.9% can be recovered from the starting solutions. A process was proposed for the treatment of sulfuric acid leaching solutions of spent LIBs containing Co(II), Mn(II) and Ni(II) by solvent extraction.

On Self-Positioning and Self-Fixation of Parts Made of Alloys with Shape Memory Effect under Component Assembling

Introduction Violation of mutual positioning and fixation of parts worsens the operation of the equipment. Traditional approaches to solving the problem under consideration have been sufficiently studied: interchangeability of parts and the use of special equipment. Both methods involve a significant number of additional elements and assembly operations. Fixation is often provided by means of force fitting and welding. Disadvantages of these methods include assembly, residual and other stresses, engineering constraints, etc. To solve these problems, alloys with thermoelastic phase transformations are used, which provide shape memory effects (SME) to manifest themselves. This article describes, for the first time, self-positioning and self-fixation using the example of parts specially made from an alloy with SME. Materials and Methods. The pin element under pressing mandrels the blind hole of the cup and enters the seat. The alloy with SME was Ti-55.7wt%Ni. The temperature of the onset of its austenitic transformation was As = 95°C ± 5°C. The elemental composition was determined by a Shimadzu EDX-8000 X-ray fluorescence spectrometer, the phase composition — by a Shimadzu XRD-7000 diffractometer. The temperature was specified through differential scanning calorimetry. The range was 20–300°C, the heating rate was 5 deg/min. A Guide T120 thermal imager and a RangeVision DIY 3D scanner with structured illumination were used. After pressing the pin into the cup at different angles, the alignment and deviations between the axes of the cup and the pin were examined. Then, the cup was heated to 110–120°C, cooled, and control measurements were taken.Results. Values of the deflection angle after pressing were 0.2–11°. With a rigid structure and an installation angle of 0°, the pin deflected in the mounting hole by 0.2–0.5°. The axes shifted and did not intersect. The pin was not always completely pressed in. This indicated uneven deformation of the metal and different stress values around the hole. Such a unit would soon fail. The pin took the required position after heating the cup to 110–120°C (this temperature was higher than at the end of the reverse martensitic transformation). The angular deviation of the axes was noted to be 0.03–0.1°. The maximum misalignment (0.04 mm) corresponded to high positioning accuracy. Heating during the reverse martensitic transformation created internal stresses that returned the initial geometry of the cup. They also formed the forces that positioned and fixed the pin in the hole. That is, it is the parts that provide positioning and fixation (this is selfpositioning and self-fixation).Discussion and Conclusion. For self-positioning and self-fixation of parts due to the shape memory effect, it is necessary to avoid sharp transition lines between the surfaces of parts during design, select rounded corners or fillets, and get a clean surface without burrs. Self-fixation and self-positioning reduce defects and inaccuracies during assembly. The use of certain alloys increases the profitability of equipment production.

Controlled Etching of Gold Nanorods Within Mesoporous Silica Shells at Mild Conditions

AbstractSurface plasmon resonance of precious metal gold nanorods can be tuned by controlling the aspect ratio, and they find widespread applications in biotechnology, imaging, sensing, optoelectronics, photonics, and catalysis. Here, a method is proposed for the controlled etching of gold nanorods within mesoporous silica shells by using a certain concentration of H2O2 at room temperature. In the experiments, the amount of HCl is varied to adjust the acidity and/or change the amount of H2O2 to control the speed of corrosion, achieving controllable adjustment of the aspect ratio of the gold nanorods. The extinction spectra show that under the action of H2O2 and HCl, the longitudinal plasmonic resonance of the gold nanorods shifted to shorter wavelengths, and the intensity of the longitudinal plasmonic resonance decreased. The more hydrochloric acid or hydrogen peroxide added, the faster the corrosion rate of the gold nanorods, and the faster the blue shift of the longitudinal plasmonic resonance. In addition, the intensity of the extinction spectra at 320 nm increased linearly versus time, which can also be used to monitor the etching process. By corroding gold nanorods to control the plasmonic resonances, gold nanorods can find broader applications.

Tourmaline geochemical and B isotopic constraints on pegmatite Li mineralization and exploration

Pegmatite–related deposits represent one of the most significant types of mineral deposits housing rare–metal elements such as Li, Be, Nb, Ta, Rb, Cs, and Sn. Although extensively studied for almost two centuries, the mechanism controlling the rare–metal mineralization in pegmatites remains controversial. In addition to the enrichment of rare–metal elements in the source region, differentiation processes (e.g., fractional crystallization and liquid immiscibility) after emplacement may have also contributed to the concentration and mineralization of rare–metal elements. However, compared to fractional crystallization, the role of liquid immiscibility in pegmatite mineralization has received limited attention. In this study, the element and boron (B) isotopic compositions of tourmalines from different textural zones (Zones I–VI) of the rare–metal–mineralized Koktokay No. 3 pegmatite, Altai, NW China, as well as from the altered country rock and the border zone, were analyzed to evaluate the role of liquid immiscibility in the generation of Li–mineralized pegmatites. Tourmalines display a variety of compositions, ranging from schorl and elbaite in the outer zones to elbaite in the inner zones of the Koktokay No. 3 pegmatite. Tourmalines from Zones I–III exhibit no obvious internal textures, whereas some tourmalines from Zones IV–VI have replacement textures or abrupt zonations. The distinction is attributed to the absence and presence of exsolving fluids during their formation, respectively. Tourmalines in Zones I–III and VII–VIII display less variable δ11B values (–15.07 ‰ to –12.21 ‰ and –14.16 ‰ to –13.10 ‰, respectively), reflecting a negligible B isotope fractionation produced by fractional crystallization during the pegmatite evolution. By contrast, tourmalines in Zones IV–VII exhibit more significant variations in δ11B values (–14.83 ‰ to –8.09 ‰) compared to those in Zones I–III and VII–VIII. The high δ11B tourmalines in Zones IV–VII were most likely crystallized from the fluids exsolving from the highly evolved pegmatite–forming magma. Their occurrence indicates the fluid exsolution occurring between zones IV and V, where Li mineralization began in the Koktokay No. 3 pegmatite. The mineralization of rare–metal elements is closely linked to the evolution of magma into a coexisting magma–fluid system. In addition, Li–mineralized pegmatites are characterized by tourmalines with Fe3+Al-1 substitution and higher Zn, Li, Li/Sr, and V/Sc than barren pegmatites. These differences are believed to be due to the higher fO2 and greater extent of magmatic differentiation in Li–mineralized pegmatites compared to the barren ones. These findings provide new insights into using the geochemical compositions of tourmalines as a guide for exploring Li–mineralized pegmatites.

Facilitating Charge Separation of Donor–Acceptor Conjugated Microporous Polymers via Position Isomerism Strategy for Efficient CO2 Photoconversion

Photoreduction of CO2 into the chemical feedstocks of fuels provides a green way to help solve both the energy crisis and carbon emission issues. Nevertheless, undesirable charge separation and migration, as well as rapid reverse charge recombination results in the unsatisfactory photocatalytic activity of most conjugated microporous polymers (CMPs). Herein, a pair of donor–acceptor (D-A) CMPs for CO2 photoconversion was developed through position isomerism by altering linkage sites. The results show that Py-D27F with 2,7-site linkage exhibits a completely conjugated structure and a large molecular dipole moment, thus significantly accelerating charge separation and transfer. As a result, Py-D27F achieves a higher yield of 320.9 μmol g−1 h−1 for CO2-to-CO photoreduction (without the addition of any photosensitizers and precious metals), which is about three-fold greater than that of Py-D36F (3,6-site linkage). This study provides a valuable idea for exploring outstanding CMP photocatalysts for the efficient processing of photocatalysis.

Альтернативные формы инвестирования на современном этапе

e article is devoted to the marginal use of alternative investment forms: gold, precious metals, coins and diamonds at the current stage, as well as their detailed characteristics in conditions of high volatility and uncertainty of financial markets. The study reveals the dynamics, main advantages, disadvantages and extrapolar trends of the above-listed forms of investment. The article focuses on the profitability of the main financial instruments with significant risks and economic unpredictability for private investors, and its correlation with official inflation is presented. In order to hedge and diversify risks, a comparative analysis of the main financial indicators of the market and an algorithm for the profitability of a conditional balanced portfolio of a private investor are presented. The final results of the study provide a description of the fundamental factors of the growth in demand for diamonds in the long term and prove the effectiveness and convenience of this instrument.

Toxicity factors, ecological and health risk assessments of heavy metal in the urban soil: a case study of an agro-machinery area in a developing country.

The contribution of heavy metals in surface soils by the influences of agro-machinery factories is a significant growing concern. Heavy metals were analyzed by inductively coupled plasma mass spectrometry technique to assess human and ecological risks. The concentrations of Fe, Cd, Cr, Cu, As, Pb, Mn, Ni, and Zn in soil ranged from 18,274-22,652, 2.06-4.92, 24.8-41.9, 126.8-137.5, 9.20-25.2, 17.8-46.1, 114.4-183.1, 86.9-118.1, and 101.6-159.6mg/kg, respectively. The enrichment factor values of heavy metals were greater than 1.5, suggesting severe anthropogenic activities such as untreated waste discharging, burning of metallic wastes, wear, and tear, and dismantling of old batteries for heavy metals enrichment in studied soil. The contamination factor indicates considerable to very high contamination of heavy metals in soil. Moderate to high ecological risk was observed for analyzed metals which mainly originated from the maintenance and repairing of various engines in the workshop and welding and soldering of metallic substances. The target hazard quotient (THQ) was ranged from 6.99E-04 to 2.21E-01 for adults and 5.59E-03 to 1.82E + 00 for children, respectively; indicating children were more sensitive to heavy metals exposure from soil dust. The carcinogenic risk of As (1.72E-05) exceeded the USEPA acceptable limits indicating cancer risk to the residence. The current emphasized the significance of intensive heavy metals monitoring in surface soils around the agro-machinery areas due to their potential health risks associated with children.