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In pursuance to achieve green future, electrochemical water splitting can be potential technology to address the global need to replace the polluting fossil fuels. In order to search non precious and non noble metal based electrocatalysts we successfully synthesized Iron Oxide-Molybdenum Di-sulfide (Fe2O3−MoS2) via two step facile synthesis route. Fe2O3−MoS2 exhibits significant lower overpotential, 202 mV, to drive 10 mA cm−2 current density and the value is superior to the individual components, Fe2O3 and MoS2. The low charge transfer resistance 13.9 Ω signifies the faster charge transfer at the electrolyte-catalyst-interface facilitating HER performance. The sample also shows good stability and durability under the acidic medium. The higher value (10.3 mFcm−2) of electrocatalytic double layer capacitance Cdl corresponding to Fe2O3−MoS2 composite further confirms the ample availability of electrocatalytic active sites. The study establishes a successful TMO –TMD composite as a potential candidate for HER performance in acidic medium and opens up new opportunities for finding proper electrocatalyst towards 'green hydrogen'. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) are a preferred noble metal due to the fact that they have many different applications, including catalysis, nanoelectronics, and clinical practice. Applications for AuNPs include antitumor, gene delivery, and cancer treatment, drug delivery, catalysis, antioxidant, antimicrobial, and improving analytical performance. AuNPs are also used in biosensors, electronic devices, conducting, textiles, and surface-enhanced Raman spectroscopy. AuNPs can be easily synthesized using various techniques, depending on the desired shape and size. Their surfaces can be easily modified and attached with multiple molecules such as drugs, antibodies, protein, carbohydrates, and lipid. Numerous biological techniques, including those involving fungi, plants, bacteria and algae, were used to create AuNPs. There are various benefits to the biological synthesis of AuNPs, such as being simple, cost-effective, single-step, environmentally friendly, and less toxic to the cells. This review examined the role of Streptomycetes in synthesizing AuNPs from published articles and their application in the field of nanomedicine by searching PubMed, Google Scholar, and Web of Science database until June 2022. Finally, we summarize future prospect for green synthesized NPs as an alternative for nanomedicine. [ABSTRACT FROM AUTHOR]

Precious metals, such as gold, silver, platinum, palladium, and rhodium, play a significant role in our modern life. Due to the dwindling of natural resources, secondary resources, such as waste, hold significant importance as an alternative resource for these precious metals. Over the years, silica nanoparticle has taken great interest due to their unique properties, high thermal stability, high surface area, and homogenous pore size distribution. Recent studies showed that silica is mainly used in drug delivery, absorbent, hydrogen storage, and chromatography support. Functionalized silica nanosphere was used in the adsorption of Au(III) from an aqueous solution. The adsorbent was characterized by using SEM, XRD, and FTIR. Various parameters were carefully studied, such as pH, kinetic, and isothermal. The functionalization process did not significantly alter the physicochemical characteristic of the silica nanosphere. The results showed that functionalized silica nanosphere exhibit a fast reaction kinetics for the adsorption of Au(III). According to the results, Au(III) was chemically adsorbed onto the adsorbent, and the reaction followed a pseudo-second-order kinetic model. The equilibrium data fitted well with the Langmuir isotherm model with a maximum adsorption capacity of 103 mg g−1. This study highlighted a simple process of functionalizing silica-based adsorbent that could allow the adsorption of precious metals onto the adsorbent. The adsorbent performed excellently in recovering precious metals, providing insight into a sustainable way to acquire precious metals. [ABSTRACT FROM AUTHOR]

The constant accumulation of Waste Electric and Electronic Equipment (WEEE) at an accelerating pace pose a threat to the environment and people. On the other hand, the WEEE and specifically their component Waste Printed Circuit Boards (WPCBs) are rich in Precious Metals (PMs) and Base Metals (BMs), more than ten times their content in natural ores. Such an opportunity has already attracted the minerals processing industry (e.g., metallurgical companies) to the WEEE recycling problem solving. However, analogically to virgin mining, the presently more or less worthless parts of WPCBs also pose a health threat since they contain toxic pollutants. The key to efficient metal recovery from WPCBs is selective processes for fragmentation and separation which are accurate for both metals and non-metals. Fragmentation is a prerequisite for accurate separation. The closed-circuit grinding (size reduction) method is preferred in the case of WPCB processing, and a prospective technology for carrying it out is High Intensity Impact Milling (HIIM). In this paper, the HIIM (disintegrator) technology is compared with commonly known technologies for selective WPCB size reduction. The HIIM demonstrated possibility to adjust the size reduction process to different materials and replication of the initial results obtained under laboratory conditions. [ABSTRACT FROM AUTHOR]

The coals from the Raichikhinskoe (North-Eastern open pit) and Yerkovetskoe (Yerkovetsky open pit) coal deposits in the Amur Oblast were studied. Based on the results of analytical studies, the content of rare metals, including trace and precious metals in coals and rock interlayers was estimated. The concentration of some rare elements in lignite was found to be higher than the Clarke content. The content of strontium and the sum of REE+Y+Sc in lignite ash of the North-Eastern open pit of the Raichikhinsky deposit were at the level of the minimum commercial content. Increased concentrations of lithophile elements in the coals of the studied deposits and the features of the geological structure of the area suggest their accumulation in the coals as a result of the run off mainly from the acidic (granite) flanks of the Zeya-Bureya Basin. [ABSTRACT FROM AUTHOR]

Biomass derivatives are very promising as one renewable energy source to overcome the limited fossil fuel reserves. Bioethanol is one of the renewable energy resources from the second-generation feedstock that is attractive for further research. Besides, ethanol is also widely used in various applications as a solvent, chemical commodity, cosmetic and pharmaceutical industries, and others. Ethanol can be produced by the hydrogenation of acetic acid. In this work, the focus is on the supported nickel and copper-based as non-noble metallic catalysts to replace the precious metals such as Pt, Pd, and Ru. The nickel and copper-based catalysts were prepared to carry out the hydrogenation of acetic acid to enable ethanol formation. The catalysts were characterized by XRD, N2 physisorption, and TPD-NH3. The catalyst activity was investigated through hydrogenation of acetic acid solution in a batch reactor at 250 °C, 120 bar, for 18h. The highest ethanol yield was obtained at 64.52 mol% by Ni-In/TiO2 catalyst. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures based on noble metals have potential for highly sensitive chemical sensing platforms. In this study, silver coated 150nm silica nanoparticles have been investigated for mercury sensing in aqueous medium. Thickness of silver shell and size of silica core has been found to significantly impact optical properties of core shell plasmonic nanostructures. UV-Vis absorption spectra have been used to identify the sensitivity of silver nanoshells to Hg2+. Silver forms amalgam with Hg and the redox potentials are appropriate for galvanic replacement reaction with Hg2+. Due to amalgamation a blue shift in the localized surface Plasmon resonance is expected and which has been confirmed from UV-Vis results. Selectivity of the sensor has been established for calcium, barium, iron and cobalt metal ions since silver does not form amalgam with majority of transition metal ions. [ABSTRACT FROM AUTHOR]

Advanced research in the development of Quantum dots (QD) and studying their optical properties have been a trend in recent years. QDs have offered an emergent opportunity in the field of Photovoltaics, Sensors, Batteries, etc. Surface plasmon excitations of metal nanostructures and long-lived excitations of semiconductor quantum dots (QD) make them excellent candidates for studies of optical coupling at the nanoscale level. Compared with plasmons in metals, plasmons in graphene have more advantages. This paper reports about the microwave-assisted hydrothermal synthesis of Graphene Quantum Dot (GQD) with Citric acid as the precursor and subsequently studied the sample characteristics using XRD, FTIR, UV Visible Spectroscopy, XPS, and TEM. The XRD pattern of as-synthesized GQD confirmed the presence of a broad peak at 2θ = 24.56° which is related to the structure of GQD with no impurity. The use of graphene-based light matter interaction has been proven as a promising aspect due to the strong optical absorption of light at a single-atom level. [ABSTRACT FROM AUTHOR]

Exploring new strategies for noble metals and plasmonic nanostrucutres for sensing applications is a highly active area due to recent advances in nanofabrication methodologies. It has become possible to synthesize plasmonic nanostructures with different shapes such as nanorods, nanoholes, metal nanostructures with hollow interior, nanorice and nanocubes etc. These nanostructures have unique optical properties and we can access different region of spectrum using them. Due to unique biocompatibility and resistant to oxidation silver and gold based plasmonic nanostructures have been utilized for biological and chemical sensing platforms with impressive sensitivity and selectivity for precursors. This review summarizes the recent strategies to develop efficient sensors using spherical as wells as non-spherical gold and silver Plasmonic nanostructures including silica based nanoshells. [ABSTRACT FROM AUTHOR]

Lithium ion batteries are widely used in portable electronic devices, electric vehicles and renewable energy storage. They can be harmful to the environment if disposed of improperly. Recycling lithium ion batteries is an important solution to reduce their impact on the environment. Currently, there are several methods of recycling lithium ion batteries, including chemical recycling and physical recycling. Chemical recycling involves dismantling batteries and separating the components through chemical reactions such as hydrolysis and pyrolysis. These methods can be effective in recovering precious metals such as nickel, cobalt and manganese, but they are expensive and energy intensive. On the other hand, physical recycling involves the use of different technologies to separate battery components according to their physical properties, such as density and magnetism. These technologies include gravimetric separation, flotation separation and magnetic separation. Physical recycling methods are less expensive and more environmentally friendly, but may be less effective in recovering precious metals. In general, the recycling of lithium-ion batteries is an important solution for protecting the environment and conserving natural resources. However, continued efforts are needed to improve recycling methods and increase public awareness of the importance of battery recycling. [ABSTRACT FROM AUTHOR]

The article is devoted to solving an urgent problem - the development of effective water purification methods from heavy metal ions from industrial wastewater. Currently, more attention is paid to technologies that allow the disposal of precious metals, the organization of circulating water supply, and obtaining sludge safe for disposal. Experimental studies of nickel ion extraction from industrial wastewater of a galvanic enterprise have been carried out. The process of formation of ferromagnetic compounds of nickel and iron has been studied. The influence of the purification process of its conditions - the concentration and ratio of nickel and magnetite ions, temperature, pH of the medium - has been studied. The optimal parameters of the wastewater treatment process from nickel ions with an initial concentration of up to 30 g/l were determined. The possibility of obtaining ferromagnetic reagents from spent industrial iron-containing solutions is shown. Different compositions of reagents were studied, and the most optimal reagent was selected, including magnetite and sodium silicate—a study of the physicochemical properties of sludge formed during the purification process. Studies have shown that the residual concentration of nickel in the solution after applying the proposed purification technology is in the range of 0.14 to 0.6 mg/l. The technology developed by us and described in the article allows removing nickel with an efficiency of up to 95.78%. [ABSTRACT FROM AUTHOR]

Waste PCB is a complicated and valuable electronic waste. E-waste production is increasing at a high alarming rate in industries. Now, it is more important to recycle and reuse it. WPCB contains various noble metals such as copper, nickel, aluminum, lead, zinc, etc. If these wastes are dumped in lands, it's hazardous to land. So, it is important to recycle it. There are various processes to recycle it, but not all the process are environmental friendly. In this study, we discussed about the two process namely chemical leaching and bioleaching. Chemical leaching involves the use of hydrochloric acid, malic acid and citric acid whereas the bioleaching involvbes the production of organic acid using Aspergillus niger. The main aim is to extract the valuable metals such as copper and nickel from the waste PCB. The effect of time and concentration on leaching were investigated. The characterization of the E-waste was studied and the leaching recovery percentage was found. This study also shows that comparative study between chemical leaching and bioleaching. [ABSTRACT FROM AUTHOR]

Aurum and argentum are the most useful metal of all the minerals mined from the Earth. Both of them are noble metal. This research verify the aurum's nobleness compared with argentum based on the adsorption energy of hydrogen atom on the metal surfaces. The adsorption energy can be obtained by studying a simple surface reaction, the adsorption of molecule hydrogen on the metal surfaces. The calculation of adsorption energy was done computationally based on Density Functional Theory. This research found that aurum has the most positive adsorption energy compared with argentum. The more positive the adsorption energy, the harder it will be for hydrogen atom to adsorp to the surface. This result indicates that aurum is more noble than argentum. [ABSTRACT FROM AUTHOR]

5 wt.% of noble metals (Ag and Cu) were introduced onto commercial zinc oxide (ZnO) via an electrochemical method. The catalysts were characterised by XRD, FTIR, BET and UV-Vis DRS. The introduction of noble metals has increased the surface area and decreased the band gap of the catalysts which contributed to excellent photocatalytic performance. The performance on photodegradation of 2,4-dichlorophenol (2,4-DCP) under visible light irradiation was highest with 5% Cu-ZnO (82%) followed by 5% Ag-ZnO (79%) and ZnO (55%). The lowest band gap energy with the largest surface area of 5% Cu-ZnO probably contributed significantly to the best photocatalytic degradation of 2,4-DCP. In evaluating an aqueous phase for photocatalytic reaction, the pH solution is an important regulating parameter. Therefore, the effect of pH on the degradation of 2,4-DCP by 5% Cu-ZnO and 5% Ag-ZnO was examined in this work. Besides, the optimum pH for the reaction is usually determined by the catalyst's points zero charge (pHPZC). The pHPZC of 5% Cu-ZnO and 5% Ag-ZnO were found to be 4.4 and 4.5, respectively. Thus, both catalysts worked the best in an acidic condition (pH 3). [ABSTRACT FROM AUTHOR]

Physico-chemical processes of argon-chloride roasting taking place in raw charge for obtaining lightweight porous aggregate - agloporite on the basis of flotation tailings from copper enrichment plants have been studied. The influence of temperature and duration of the roasting process as well as the influence of the amount of added sulphochloride additive consisting of phosphogypsum and chloride-containing alkaline waste of soda production on the extraction degree of noble and residual metals was studied and the optimum conditions of metal extraction were determined. It is shown that the maximum extraction of residual metals at the charge firing with the addition of up to 30% of phosphogypsum and chloride-containing alkaline waste of soda production with the optimum temperature of 1100-1150 0C and holding time of 30-40 minutes makes 92.9 - 98.8%. It has been established that temperature, duration of chlorination time, amount and type of chlorinating waste have a significant influence on the degree and rate of metal chloride distillation. [ABSTRACT FROM AUTHOR]

This study examined the adsorption of heavy metals and precious metals from aqueous solution by livestock biomass as biosorbents and their treatment effect with reducing chemicals. The adsorption of copper, lead and cadmium was carried out using sheep wool, sheep manure and sheep fat. The copper adsorption was highest among three biosorbents. Sheep wool was treated with an aqueous solution of Na2S, NaOH, NaHSO3, and NaBH4 to enhance the adsorption ability. The Na2S treatment of sheep wool dramatically enhanced the adsorption amount of Au(III) and Cr(III) and was several effective for Cu(II) and Cr(IV). All adsorption results were confirmed with the Langmuir isotherm model in the equilibrium and Pseudo-second order model in the kinetics. From the adsorption properties and ESCA analysis of sheep wool adsorbed each metal, it was confirmed that Au(III) interacted with thiol and amino groups, Cu(II) and Cr(III) with a carboxyl group, and Cr(VI) with the amino group of sheep wool. [ABSTRACT FROM AUTHOR]

Historical ore exploitations generated mining waste with useful metal content, near Baia Mare, Romania. Central Flotation Pond (CFP) represents a secondary resource, but also a risk factor of pollution for the environment: groundwater, surface water, soil, air. CFP was inventoried by the Permanent Secretariat of the International Commission for the Protection of Danube River (ICPDR) as high risks spot in Romania with immediate effects on Somes-Tisa sub-basin, due to the content of dangerous substances: cyanide, heavy metals (Pb, Zn, Mn). The report of the European Commission delivered as a result following causes and effects of Aurul (historical pond in Baia Mare area) accident evaluation. Complex ores and concentrates which incorporate a variety of recoverable metals can be effectively processed by using hydrometallurgical routes. This paper took into account data regarding researches based on simply treating by aqueous solutions using different leaching media (e.g. mineral acids, deep eutectic solvents), keeping low processing costs. Also, in hydrometallurgical plants, solutions and slurries generally are transferred easily in closed pipeline systems which indicate another cost advantage. The main objective is to develop an eco-friendly technology to the heavy and precious metals recovery, an alternative to polluting technologies such as cyanide, according to legislative, environmental and economic framework. This can be achieved by extraction of metals from ores using hydrometallurgical processes. The technological flow sheet proposes a step-leaching process using both common acids (H2SO4, HNO3) and deep eutectic solvents (maline, ethaline), followed by precipitation and electrochemical processes for useful elements recovery. Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS) method highlighted the presence of Ag, Cu, Pb, Fe in electrochemical deposits obtained from leachates. [ABSTRACT FROM AUTHOR]

The optical properties of 4 liquid metals Ga, Hg, Cs and Rb are calculated in core-shell bimetallic nanoparticles system over size parameters. The localized surface plasmon resonance (LSPR) of liquid and noble metal for different sizes and shell thickness are effectively tuned over electromagnetic spectrum. In addition, by using Mie Theory size is optimized in terms of structural parameters. The optical frequencies of these core-shell nanostructures are observed to be shifting in UV-Visible-NIR region with enhanced optical efficiencies. Two LSPR peaks are observed for Hg@Au core-shell nanoparticles in UV and Visible region simultaneously. For Cs and Rb almost same plasmonic response is observed, however efficiencies of Rb are better than all other nanoparticles. The calculated absorption and scattering efficiencies of all different compositions for respective applications are discussed. [ABSTRACT FROM AUTHOR]

The multimetallic nanostructures of a noble metal such as gold, silver, and copper have attracted great attention in alloys and core-shell configuration due to the enhanced plasmonic effect. In this theoretical study, the optical properties of bare NiFe and NiFe@Au core-shell NPs have been calculated using extended Mie theory. The core-size of nanostructures is considered 5 nm to 25 nm and shell thickness systematically varied as 3, 5, 7 and 10 nm. It is observed that the localized surface plasmon resonance peaks are red-shifted with increasing shell thickness and blue-shifted with increasing core-sizes. Further, broadening in LSPR peaks is found, as the size of core-NiFe NPs increased and optical efficiency increases with Au-shell thickness. The LSPR peaks at λmax show the absorption spectra in the range of 508-541 nm wavelengths and hence, absorption peaks are found in the visible region. In addition, LSPR peaks of NiFe (permalloy) coated with Au NPs are influenced by changing the refractive index of the embedded medium. Hence, the optical response of NiFe coated with Au nanospheres can be tuned and controlled in the visible region of the electromagnetic spectrum. From the results, it is revealed that varying either NiFe-core or Au-shell thickness and embedded medium could result in obtaining tunable light absorption in UV-visible and may find application in optical imaging, sensing, medical, and novel functional and biomagnetic devices. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are a widely developed noble metal nanoparticle that possesses antimicrobial activity. The advantages of AgNPs is their nature and ability to inhibit microbial growth, making them a potential alternative material to overcome the problem of antibiotic resistance. The synthesis of AgNPs can be done through a biosynthesis process using plant extracts as a bio-reductant. The extract preparation can affect the synthesis process, including the reaction rate and AgNP size. In this study, AgNPs were obtained through the biosynthesis process using 3 different extract preparations from Diospyros discolor Willd. (Bisbul) as the reducing agent. The extract was prepared by different extraction methods, including water extract, crude water extract, and methanol-water extract fraction. The formation of AgNPs was confirmed using an ultraviolet-visible spectrophotometer. The dispersity and zeta potential from the nanoparticles was confirmed using Particle Size Analyzer (PSA). The results obtained showed that all of the extract preparations can produce AgNPs. Depending on their characteristics, different extract preparations tend to have different reaction speeds, sizes, and distributions of the AgNPs formed. The activities of AgNPs against Staphylococcus aureus and Escherichia coli were also tested. The result showed that all AgNPs synthesized using the extracts had good antimicrobial activity, but the crude water extract and methanol-water extract had the strongest activity. Based on their spectral features, these two extracts tend to produce small sized particles and monodispersed distribution. [ABSTRACT FROM AUTHOR]

Nowadays, the toughest challenges faced by a human are increasing pollution which leads to global warming. This global warming is occurred due to environmental pollution which leads to a tremendous change in the climatic conditions. This paper is based on the pollution control method in the 4-stroke S.I. Engine which runs on Petrol and CNG by using a catalytic converter. This catalytic converter is fabricated by using stainless steel wire mesh (SS-304) which is economically low cost compared with contemporary catalyst such as Rhodium, Platinum and Palladium.(SS-304) The stainless-steel wire meshcoated copper (which is the metal catalyst agent)by using electroplating which provides high conductivity, withstand to higher temperatures (thermal resistance) and flexible.This coated SS-304 wire mesh is reduced the emissions such as CO2, HC, NOx, CO from the bike. [ABSTRACT FROM AUTHOR]

The use of noble metals within nanophotonics and nanoplasmonics in general is a well established practice. However, when the thickness of the metals used, in particular gold, decreases, their quality suffers. In particular, the influence of the adhesion layers becomes significant. In this papers we present our approach towards obtaining up to 10 periods of gold/alumina layers, with 20 nm period and 50% filling fraction. Using organic adhesion layers, the Au behaves very close to the theoretical limit, demonstrating that these layers minimally influence the Au properties. Initial attempts into patterning these multi-layer structures show the possibility of obtaining simple one-dimensional designs having down to ca. 100 nm linewidth. Results and challenges in using our approach are also presented. [ABSTRACT FROM AUTHOR]

In this work, the effect of electrode materials on the voltage generation as well as the internal resistance of the nanogenerators have been studied. Piezo-electric polycrystalline tetragonal nanowires of Pb(Zr0.52Ti0.48)O3 (PZT) grown by hydrothermal technique were used as the generating material. As an electrode material noble metal gold (Au) as well as copper (Cu) were used. It has been found that the voltage generated by using copper electrode is maximum around ∼1 V. It has also been observed that output power of the nanogenerator enhances from 80 nW to 350 nW with a concomitant reduction of internal resistance. An effective dependence on work function of the electrode material has been established. [ABSTRACT FROM AUTHOR]

We here investigate the optical properties of liquid metal nanosphere for its potential use in plasmonic applications. Due to liquid state and reactivity its efficiency is limited to a narrow range of spectra. The liquid core is coated with noble metal (Silver) to provide stability and broadband plasmonic properties. We discuss theoretically localized surface plasmon resonance (LSPR) peak, absorption and scattering efficiencies using Mie theory. The influence of core size and shell thickness on optical spectra of core-shell nanoparticle shows shifting of peak positions from NIR to Visible region of EM spectrum with increasing size. The enhancement in scattering efficiencies is also observed. These results can be useful for applications like soft electronics, sensors, optical imaging etc. [ABSTRACT FROM AUTHOR]

Optical spatial resolution limit prohibits an accurate spectroscopic characterization of an object at nanoscale. Plasmonic assisted microscopy at nanoscale, however, can overcome the Abbe's diffraction limit utilizing the confinement of localized electric field in the close proximity of noble metal nanoclusters. We report the phonon imaging of GaN nanowire (NW) of ∼225 nm and studies of Mg doping in GaN with the help of Au nanoparticle assisted plasmonic tip-enhanced Raman spectroscopy (TERS) in the near-field well below the diffraction limit, for the first time. We also image InN nanorods in the sub-diffraction limit using surface optical phonon mode to differentiate the orientation of the one-dimensional nanostructures. A smallest size of 25 nm Si NW is imaged using TERS and is analyzed for the deviation of the phonon behavior with respect to that for NWs with larger diameter as well as in the ensemble for far-field measurements. The challenge in phonon imaging of nanostructures having varying polarizability with different fractional ionic component (FIC) is also discussed while analyzing a one order larger sized, at least in one dimension, AlN (FIC ≈0.72) nanotip as compared to the Si NW (FIC ≈0). In this regard, imaging GaN NW in the sub-diffraction limit with FIC ≈0.5 for GaN may be appreciated. [ABSTRACT FROM AUTHOR]

Noble metals (Au and Ag) are the primary raw materials which have vast potential application ranging from across biosensor, biomedicine, science, and engineering fundamental. However, alloying them will enhance the efficiency and applicability of noble metals. Employing the linear-weight (LW) technique to construct a dielectric function of a binary solution is still disputed. However, this method is still widely used to examine Localized Surface Plasmon Resonance (LSPR) of Au-Ag binary solution. In this work, the calculation of electromagnetic response such as Localized Surface Plasmon Resonance (LSPR) of bimetallic Au-Ag nanorod was performed by means of MNPBEM package. We utilized nanorod-shaped with two different excitation modes, namely, Transverse Mode (TM) and Longitudinal Mode (LM), and various compositions to investigate their LSPR shifting anomalies. Moreover, we employed the LW technique to construct their dielectric function and analyze the LSPR anomalies. Interestingly, we found that using LW approximation, the resonance peak of TM is separate into two peaks. These peaks originated from the free electron of Au and Ag respectively, however, some of LSPRs peak did not occur amongst peak of pure Au and Ag. Practically, using LW method the resonance peak should be located amongst their individual elements. This work has provided the limitation of using silver fraction and the related aspect ratios to predict the LSPR spectra of Au and Ag on nanorod-shaped. [ABSTRACT FROM AUTHOR]

Rapid industrial development uses the catalyst in response to reaction speed in a process. The process uses catalysts in the oil and gas industry is Continuous Catalytic Cracking Platforming, in which the process produces Pt/Al2O3 catalyst waste approximately 2000-3000 kg/year. Recovery of platinum metal is needed to save the cost of purchasing platinum catalysts because platinum is very costly and it is categorized as hazardous and toxic material waste. The method used for platinum recovery is microwave-assisted digestion method. With this method, the Pt/Al2O3 spent catalyst is treated in an isolated, high-temperature, and high-pressure vessel. Platinum metal is one of the precious metals in which it is relatively inactive even to mineral acid. This metal can only be readily dissolved in aqua regia with high-temperature and high-pressure condition. This experiment is used to find out the digestion parameters effect (temperature, solid/liquid ratio, and contact time) and to see if the spent catalyst can be destructed perfectly with its various condition. The highest percentage of platinum recovery achieved is 94.06% with 0.1 gram of spent catalyst used at 220°C. For the kinetic study, surface chemical reaction is the most suitable kinetic model for digestion and has an activation energy value of 13.35 kCal/mol. [ABSTRACT FROM AUTHOR]

Our understanding of the geological evolution of West Papua (or the Bird's Head Peninsula and Bird's Neck) predominantly stems from a systematic mapping campaign conducted by Indonesian and Australian geologists during the 1970's and 80's, together with the findings of mineral and hydrocarbon exploration by Dutch geologists in the early 1900's. Most of the research that has been conducted since these initial, but comprehensive studies have been associated with continued exploration for hydrocarbons (e.g., around the Salawati and Bintuni Basins) and precious metals (e.g., associated with Grasberg–Ertsburg). Here we present an overview of research conducted over the past five years that was largely funded by several oil exploration companies. Our research did not focus on oil exploration, but instead attempted to update our understanding of the age of magmatic, metamorphic and deformation events, and to improve our knowledge of the regional stratigraphy of West Papua. These new data have been used to develop new tectonic models and paleogeographic maps that provide a framework for future studies in the region to build upon. [ABSTRACT FROM AUTHOR]

Printed Circuit Boards waste has been confirmed contained precious metal like gold. Gold from PCB waste can be separated using H2O2-H2SO4 to reduce nonprecious metal and continued by microwave-assisted aqua regia leaching to improve the yield of HAuCl4. HAuCl4 has been purified by an adsorption-desorption process using Mg/Al- Hydrotalcite. Based on Mg and Al mole fraction and analysis of water content, the empirical formula of Mg/Al hydrotalcite is Mg0.5173Al0.4827(OH)2(NO3)0.4827•0.5072H2O. Gold nanoparticles have been synthesized using glutamic acid and trisodium citrate. Surface plasmon resonance of gold nanoparticles has been characterized using UV-Vis spectroscopy. [ABSTRACT FROM AUTHOR]

In this work, silver nanoparticles (Ag NPs) were deposited on a heated glass substrate by using thermal evaporation technique without any additional annealing process. Ag NPs show stronger plasmonic increment of photoluminescence in comparison with other noble metals. The characterization techniques such as SEM, XRD, and UVVis. were used to analyse optical and morphological studies of these deposited metal NPs. Growth of nanospheres in Ag thin films were revealed by SEM. The substrate temperatures were varied from 150°C, 250°C to 350°C. Under some conditions, the Ag NPs exhibit a broad absorption in visible region. This is attributed to their LSPR effect i.e. Localized Surface Plasmon Resonance effect. Here, substrate temperature is the key parameter for controlling Ag NPs size and shapes. [ABSTRACT FROM AUTHOR]

Research interest is on liquid mercury nanoparticles to show plasmonic response for the purpose of their use in plasmonic applications. The liquid metal mercury is having many applications in like high intensity discharge lamps, electrical switches etc is presently studied by using Mie theory for its LSPR based optical properties with noble metal Ag in the form of core-shell nanostructures. The simultaneous two dipole resonance peaks shown by Hg@Ag nanospheres offers unique properties which can have interesting applications. The calculated optical frequencies are found in UV-visible region of EM spectrum. [ABSTRACT FROM AUTHOR]

Tungsten trioxide (WO3), an important n-type metal oxide semiconductor was intensively studied due to its physical and chemical proprieties in the field of gas sensors. To improve gas sensitivity and selectivity, noble metals such as Au are incorporated in metal oxides structures. The aim of this work is to prepare Au-incorporated WO3 thin films as sensing layers of resistive sensors using Pulsed Laser Deposition (PLD) technique. Au and WO3 targets were irradiated at 213 nm wavelengths in oxygen atmosphere. Thin films of Au incorporated WO3 have been explored to find the properties in terms of morphology and crystallinity. The XRD, SEM coupled with EDX and Raman spectroscopy studies indicate that the properties of thin films are strongly dependent on deposition conditions. The optical band gap of Au-doped WO3 was increased from 2.7eV to 2.82eV with increasing oxygen pressures. [ABSTRACT FROM AUTHOR]

Mining activity entails accumulation of sulfide–bearing mill wastes with high concentrations of ore elements (Fe, Cu, Zn, Cd) and impurities (As, Hg, Be, and Tl). The volumes of hazardous sulfide-containing mining waste in non-equipped storage facilities according to modern standards reach several billion tons in Russian Federation. The handling of abandoned waste in our country is not currently regulated, the question remains open: there is no established methodology for estimating stockpiles and handling of waste stored in old unaccounted storages. Also, the abandoned mine wastes can be considered as “man-made deposits” due to high content of valuable components and their volumes. This paper reports on the results of the complex geophysical and geochemical investigation of three abandoned mine tailings Western Siberia, Russia. Today, all objects are in an abandoned state, located on the territory of settlements, are free to visit by the local population, and are also used as recreation areas. The aim of the work was to assess the volumes of man-made bodies, the resources of valuable and toxic components for further calculation of environmental damage and the economic feasibility of processing the waste. When comparing the concentrations of non-ferrous, rare and noble metals, as well as non-metals (As, Sb) in waste with concentrations in the ores of these deposits, high concentrations of Zn, Cu, Pb, As, and Sb were noted. According to the most conservative estimates, three small abandoned dumps in the territory of two Russian cities contain up to 26 % As from his annual production (AP), 7.6 % In, 6.5 % Sb, 0.74 % Hg, 0.52 % Ag, 0.22 % Zn. Of course, we present these figures here only to demonstrate the resources of dumps in the mining regions of the Russian Federation. A separate big question is the probability of their extraction. The information on the contents of potentially toxic components (As, Hg, Be, Tl) in such objects becomes extremely relevant. Further work in this direction is related to the compilation of a register of such objects, the calculation of economic feasibility and environmental damage. [ABSTRACT FROM AUTHOR]

Waste electronic equipment has become one of the fastest growing waste streams in the world. Mobile phones make up a large proportion of this waste. They cause not only ecological threat, but also a serious waste of resources, including copper. That is why new and effective ways of processing this waste and reusing recovered metals are increasingly being sought. Most modern research on the recovery of non-ferrous and precious metals from mobile phones has focused on hydrometallurgical and biometallurgical techniques. This article presents the impact of ozone on the leaching process of selected metals from printed circuit boards of used mobile phones. The trend of changes occurring during the leaching of e-waste in H2SO4 and HCl using O3, monitored for 20 min, is presented. An increase in the concentration of selected metals in the solution indicates a positive effect of the additional oxidizing agent, which is ozone. Additionally, the results of these e-waste leaching in aqua regia are presented. The purpose of leaching was to check the initial metals content in PCB waste and the content of these metals in samples that had previously been subjected to acid leaching experiments at various parameters. The content of metals after leaching in aqua regia was determined using microwave plasma atomic emission spectroscopy (MPAES) (Agilent MP-AES 4200). Currently, electronic waste is a huge problem worldwide. The continuous development of more reliable, advanced technologies has shortened the life cycle of the product, as a result of which consumers buy new electronic devices while rejecting old ones. Old, useless electronic devices are thrown away. These activities have led to an increase in the amount of electronic waste in the world. Electronic waste, including mobile phones, contain many valuable metals, including copper, gold, silver, palladium and others. [ABSTRACT FROM AUTHOR]

A large number of precious metals such as molybdenum, gold, uranium and much more are obtained from sulfide ores. Currently, a large number of hydrometallurgical methods are used to extract precious metals, which in turn are outdated in this field. In this regard, it is necessary to develop new modern methods for extracting all valuable components from sulfide ores. One of these methods is the process of bio-leaching with the use of microorganisms. The use of this method in mining companies will help reduce the risk of environmental pollution, and there is also an economic benefit associated with the involvement of recycling of waste from mining companies.This article describes the granulometric analysis of molybdenum ore from the Shantobe Deposit. When the ore was sifted, it turned out to be of 9 classes of size. Study of the chemical analysis of the solution of the Evaporation map No.5 for the content of chemical elements in it. The use of acidophilic culture Acid.ferrooxidans, which was produced using the nutrient medium Silverman -Lyngren (9K).The growth of this microbiological culture was judged by the change in color to brown, which indicated that the solution contains Fe3+. [ABSTRACT FROM AUTHOR]

Biohydrometallurgical technologies are widely used for the extraction of non-ferrous and precious metals from sulfide ores and concentrates including gold-bearing refractory concentrates. Biohydrometallurgical treatment of gold-bearing sulfide concentrates is based on the oxidation of sulfide minerals by acidophilic microorganisms oxidizing ferrous iron and sulfur. This makes it possible to increase gold extraction by subsequent cyanidation as biooxidation results in disruption of crystal lattice of sulfide minerals and gold finely dispersed in these minerals becomes available for dissolving by cyanide. In the present study, the possibility of processing of gold-bearing pyrite-arsenopyrite concentrate containing of 56% of pyrite, 14% of arsenopyrite, and 45.5 g/t of gold by tank biooxidation was studied. Biooxidation in continuous mode was performed at 40°C in laboratory scale reactors using association of acidophilic microorganisms. Residence time was 6 days. Pulp densities (solid to liquid ratio, S : L) were 1.5 : 10 and 1: 10. At pulp density of 1.5 : 10, biooxidation was not stable, probably due to high sulfide minerals content in the concentrate, while oxidation at a pulp density of 1 : 10 was stable, which was indicated by liquid phase parameters (pH, Eh, ferric and ferrous iron concentrations). Thus, biooxidation to obtain solid residue, which was used for further gold extraction was performed at a pulp density of 1 : 10. Biooxidation made it possible to oxidize 63% of pyrite and 95% of arsenopyrite. Gold recovery by cyanidation increased from 57% (from unoxidized concentrate) to 83% (from solid residue of biooxidation). Liquid phase of the pulp containing high concentration of Fe3+ ions (up to 22 g/L) was used for oxidative leaching of substandard copper-zinc concentrates. Three samples of copper-zinc concentrates containing 17 and 2.9%, 16 and 5.3%, and 6.2 and 7.3% of Cu and Zn were studied. Leaching of these concentrate performed at 80°C, pulp density of 1 : 10 for 3 h made it possible partially leach both copper and zinc. Copper content in the solid residues increased or did not change significantly, while zinc content decreased in comparison with the concentrates, as copper sulfide minerals of the concentrates (chalcopyrite and tennantite) are more refractory to oxidative leaching than zinc sulfide (sphalerite). Copper and zinc content in the residues was 17 and 1.45%, 16.7 and 2.9%, and 6.15 and 3.95%. Decrease in zinc content in substandard concentrates, which cannot be successfully conditioned by flotation, using alternative approach including hydrometallurgical methods is promising for the production of high-grade copper concentrates. Thus, in the present study, it was demonstrated that biooxidation of sulfide gold-bearing concentrates may be used not only to increase gold extraction rate, but also to obtain solutions with high Fe3+ content, which can be used for oxidative leaching of other mineral raw materials. [ABSTRACT FROM AUTHOR]

At present, multicomponent systems, such as metal-oxide nanocomposites, deserve great attention. Their creation is caused by the need to isolate the core from the effects of external influences, or to fix any substances on the outer layer, thereby imparting unique functional properties. Such nanocomposites are widely used in various fields of science and technology: from creating photonic crystals and solar cells based on them, to transporting drugs, and using in magnetic-resonance and computed tomography as contrast agents for the diagnosis of various neoplasms. The synthesis of nanocomposites containing noble metal nanoparticles was carried out using the sol-gel method and chemical reduction method. The obtained nanocomposites were investigated by a complex of modern analysis methods: scanning electron microscopy, differential scanning calorimetry and thermogravimetry, X-ray phase analysis. As a result of studies, it was found that silver and gold nanoparticles in nanocomposites are located on the surface of silicon dioxide microspheres and have a cubic face-centered crystal lattice with the Fm-3m space group, and an average size of about 10 nm and 50 nm, respectively. As a result of the studies, the possibility of the formation of multicomponent systems based on nanostructured silicon dioxide with gold and silver nanoparticles immobilized on its surface was shown. [ABSTRACT FROM AUTHOR]

We report herein new Pt and bi-/tri-metallic alloy clusters. For the Pt clusters, we have precisely synthesized the cationic Pt17 clusters, [Pt17(CO)12(PPh3)8]n+ (n = 1, 2), protected by CO and triphenylphosphine (PPh3) by a simple method. The study on the synthesized clusters revealed that [Pt17(CO)12(PPh3)8]n+ (n = 1, 2) have geometrical structures similar to that of previously reported Pt17(CO)12(PEt3)8 (PEt3 = triethylphosphine) and they [Pt17(CO)12(PPh3)8]n+ (n = 1, 2) possessed discretized electronic structures. For the bimetallic cluster, we have established a method to selectively synthesize hetero-biicosahedral [Au24Pd(PPh3)10(SC2H4Ph)5Cl2]+ (SC2H4Ph = phenylethanethiolate), in which a Pd atom replaces the central Au atom in one icosahedral Au13 core. The theoretical study on the related cluster suggested that [Au24Pd(PPh3)10(SC2H4Ph)5Cl2]+ has dipole moment and is comparatively stable during cluster reduction. For the trimetallic cluster, we succeeded in the compositionally selective synthesis of [Au∼20Ag∼4Pd(SC2H4Ph)18]0 and [Au∼20Ag∼4Pt(SC2H4Ph)18]0. Single crystal X-ray structural analysis revealed the precise position of each metal element in these metal clusters. In this study, it was demonstrated that reacting with thiol at an elevated temperature is important to direct the metal elements to the most stable positions. [ABSTRACT FROM AUTHOR]

This conference contribution is focused on decoration of WS2 nanotubes (NT-WS2) with gold and silver nanoparticles via facile routes implying direct reaction of tungsten disulfide with water-soluble AuIII and AgI species at 100°C. The underlying mechanism of these interactions will be discussed in details based on extensive studies of reaction mixtures and resulting metal–NT-WS2 nanocomposites, including thorough X-ray photoelectron spectroscopy (XPS) analysis. Surprising features in optical spectra of the designed nanocomposites would be reported, including suppression of plasmon resonance in tiny noble metal nanoparticles (< 10 nm in diameter) grown onto NT-WS2. The plasmonic features of individual gold nanoparticles on the surface of disulfide nanotube were also characterized by electron energy loss spectroscopy in scanning transmission electron microscopy mode (STEM-EELS). Photoresistive NO2−sensing response of NT-WS2 under green light illumination (λmax = 530 nm) and its enhancement by plasmonic gold "nanoantennas" will be reported as well. [ABSTRACT FROM AUTHOR]

Additives have been synthesized and tested to reduce the content of CO and NOx oxides in the gases of regeneration of FCC without the use of noble metals. The following can be used as additives to reduce CO: mixed oxides based on copper, cerium, magnesium and aluminum. According to the efficiency (89.7-95.5%) of the reduction in the CO content, mixed oxides based on copper and cerium are comparable with the additive based on platinum KO-10 (96.8%). All additives to reduce CO lead to an increase in the formation of NOx oxides. Additives based on mixed oxides (47.0%) are less conducive to this compared to platinum based additives (71.0%). Zeolite ZSM-5 modified with copper and iron can be used as an additive with the function of joint reduction of CO and NOx oxides. The effectiveness of reducing CO is close to 100%, and for NOx oxides it is 45.9%. [ABSTRACT FROM AUTHOR]

Rechargeable metal-air batteries have come up with high theoretical energy density as compared to existing lithium and sodium ion batteries. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the two processes, related to water splitting, over which metal-air batteries run. Since both processes are sluggish, hence, they require a catalyst and since the existing precious-metal based catalysts are selective and expensive, there is a need to find a suitable bifunctional catalyst for the same. Motivated by enhanced structural stability imparted by the polyanionic groups along with many reports on electrocatalytic activity of Cobalt phosphate based materials, we tried to look into the electrocatalytic behavior of Na2CoPO4F and Na4Co3(PO4)2P2O7. Both materials were synthesized via solution combustion route resulting in carbon coated and amorphous particles. The ORR/OER properties of the materials were studied in alkaline solution showing bifunctional behavior. An onset potential of 0.854 V and 0.771 V vs. RHE was observed for Na2CoPO4F and Na4Co3(PO4)2P2O7 with a current density of 5.84 mA cm-2 and 3.4 mA cm-2 respectively. The onset potential during OER was observed to be 1.591 V and 1.596 V vs. RHE for Na2CoPO4F and Na4Co3(PO4)2P2O7 respectively. As an application, aqueous Na-air battery was fabricated using Na2CoPO4F as an aircathode showing good (dis)charge behavior. [ABSTRACT FROM AUTHOR]

To bring solar/electrical-to-hydrogen energy conversion processes into reality by fabricating non noble metal catalyst is an important agenda of researchers now a days through hydrogen evolution reaction (HER) by electrochemical method. Non noble metal catalyst such as CuMoO4 nanoparticles were successfully synthesized by hydrothermal process. Synthesized sample were characterized by XRD, Raman and FT-IR analysis. Morphology of the sample was observed by SEM and HR-TEM analysis. HER was performed by modification of synthesized CuMoO4 on Glassy Carbon Electrode. [ABSTRACT FROM AUTHOR]

International Temperature Scale-1990 (ITS-90) is formulated based on various phase transition temperatures of high pure substances to cover the temperature range from 0.65 K to 1357.77 K (-272.5 °C to 1084.62 °C), where kelvin is defined on triple point of water (TPW) at 273.16 K and the higher defined fixed point is freezing point of copper at 1357.77 K. To extend the temperature scale at higher temperatures, metal-carbon eutectic fixed points are extensively being developed as the reference standards upto 3000 °C for thermometry and radiometry applications. The assignment of the eutectic melting transition temperatures to these metal-carbon eutectics is challenging as the melting plateaus are not as flat and wide as the conventional high pure metal fixed points. This paper presents the method to determine eutectic melting transition temperature by calculating inflection point for Fe-C and Co-C eutectic fixed point cells developed at CSIR-NPL, the national metrology institute (NMI)of India. The noble metal Type-S thermocouple calibrated on ITS-90 fixed points was used to measure and determine the melting transition temperatures of Fe-C and Co-C cells, and the associated uncertainties in determination of transition temperatures were evaluated. [ABSTRACT FROM AUTHOR]

This research study reviews the treatment and recyclability of e-waste such as PCBs, e-plastics and CRTs. Land filling and incineration were found to be not good management methods as they do not deal with the toxic gases found in e-waste. Hydrometallurgy processing methods was developed and used in the extraction of base and precious metals. Since precious metal leaching is affected by copper content, to maximize precious metal leaching, a 2 step base metal leaching stage was employed. The first step mainly focused on the removal of Pb and Fe and the second step was to extract copper, zinc and nickel. First stage used nitric acid and the second stage used sulphuric acid and hydrogen peroxide. Lead recovery was almost 90% and copper recovery amounted to almost 95%. Precious metal leaching utilized ammonium thio-sulphate as the lixiviant and gold recovery was low, but silver recovery was significantly high. [ABSTRACT FROM AUTHOR]

Electronic waste is becoming a serious environmental and economical concern worldwide. The annual growth rate of about 4-5 % in 2016 is one of the fastest growing waste stream in municipal wastes and only about 20% of e-waste is recycled. The rapid growth in the use of electronic equipment caused by various socio-economic reasons has contributed significantly to the generation of large quantity of e-waste. After the use-phase, the electronic devices become electronic waste (e-waste); consequently, it is important to consider e-waste as a secondary supply for the recovery of these metals. Electronic equipment contains precious and strategic metals such as Au, Ag, Pt, Cu, Nb, Ta and others. After the use-phase, the electronic devices become electronic waste (e-waste); consequently, it is important to consider e-waste as a secondary supply for the recovery of these metals. This paper presents a hydrometallurgical recovery procedure of Ag from used computer keyboards. After collection of the raw material the main plastic sheet component (mylar) containing printed Ag circuits was separated and trimmed to a smaller pieces to fit into the container. To remove the silver from the mylar concentrated nitric acid and hydrogen peroxide were used. Subsequent steps and operations were used to convert the sample into metallic form. Final yield reached up to 1.35 % of Ag. [ABSTRACT FROM AUTHOR]

Annually about 300 metric tonnes of gold are used in electronic devices in the world. After the end of use, they become e-waste and are recycled or put on the landfills. Recycling rate of e-waste in Slovakia was in 2017 according to Eurostat only 36.7 %. Recent studies show that yields from e-waste (mainly computers, mobile phones) are much higher than in metal ores and thus can be considered as valuable secondary sources of precious and base metals. In presented paper five different parts of computer e-waste were investigated for possible gold recovery, namely CPUs, CPU sockets, BGA chips, pins from motherboards and flexible wires from monitors. All parts were mechanically pre-treated with suitable techniques to maximize gold concentration in samples. For gold recovery two-step hydrometallurgy leaching process was applied. In first step base metals were dissolved (Cu, Ni, Zn, Sn and Pb) using either HCl + H2O2 mixture or HNO3. Second step consisted in applying Aqua Regia to dissolve gold. For precipitation of dissolved gold sodium metabisulfite was used. All gold obtained was weighted in dust form. Relative yields from all parts are as follow: flexible wires – 3.27 %, BGA chips – 0.93 %, CPUs – 0.20 %, MB pins – 0.06 %, CPU sockets 0.01 %. [ABSTRACT FROM AUTHOR]

Sulfide ore processing is characterized by significant losses of non-ferrous and precious metals into various wastes including flotation tailings, which is presently considered as promising source of different metals along with low grade ores. Old flotation tailings, which have been accumulated in significant quantities during the exploration of some mineral deposits, usually contain a wide range of minerals, including sulfides (pyrite, chalcopyrite, sphalerite), sulfates, hydroxides, hydroxysulfates, etc. Thus, sulfide flotation tailings are complex polymineralic aggregates formed during long-term storage containing various base metals. Different hydrometallurgical methods including bioleaching and acid leaching were proposed to extract metals from different samples of flotation tailings. In the same time, pregnant solutions obtained during leaching of old flotation tailings often contained high concentrations of iron ions, which can be by an order of a magnitude higher than concentrations of base metals, that impedes further extraction of non-ferrous metals from pregnant solutions Thus, processing of old flotation tailings should provide selective extraction of valuable metals and obtaining solutions appropriate for further extraction of non-ferrous metals. The goal of the present work was to study the possibility of selective extraction of non-ferrous metals from old flotation tailings using acid leaching. Leaching was performed with sulfuric acid solutions (from 0.5 to 10%) and distilled water. Leaching was carried out using glass columns, which were loaded with 100 g of old tailings, and leaching was performed with 100 mL of acid solutions. The sample of old flotation samples contained 0.22% and 0.17% of copper and zinc, respectively, as well as 17% of iron. Percolation leaching made it possible to extract of 55 to 69 % of Zn and of 51 to 76% of Cu. Zn concnetrations in pregnant solution were of 1.3 to 1.6 g/L, while Cu concentrations were of 1.6 to 2.4 g/L. Ferric iron ions concentrations in the pregnant solutions were of 0.5 to 9.8 g/L, while total concentrations of ferric and ferrous iron were of 1.5 to 25.1 g/L. Iron ion concentration corellated with sulfuric acid concentration. Thus, it was shown, that extraction of both non-ferrous metals and iron depended on sulfuric acid cocnetration in leach solution. In the same time, copper and zinc extraction were close to maximum, when sulfuric acid concentration was 2.5%. Increase in sulfuric concentration above 2.5% led to the increase in iron concetration in the pregnant solutuion. Thus, it was possible to reach selective leaching of non-ferrous metals and to obtain solutions with relatively low concentrations of iron ions. High iron concentration in pregnant solutions impedes further Cu and Zn extraction. Therefore, indicated regularities may be used for the development methods of hydrometallurgical processing of old flotation tailings for the obtaining the solutions appropriate for non-ferrous metal extraction. [ABSTRACT FROM AUTHOR]

The biosynthesis of noble metal nanoparticles using microorganisms (“green synthesis of nanoparticles”) has recently become widespread for medical applications. The characteristics of the resulting nanoparticles depend on the microorganisms used and the process conditions. Screening of a number of methylotrophic bacterial communities of a practical biotechnological value was carried out to determine those ones, which were able to synthesize silver and palladium nanoparticles at high rate and efficiency. In several studied natural communities containing bacteria of the genera Methylobacterium, Methylococcus, Methylobacter and from 2 to 5 related cultures, silver or palladium nanoparticles are formed from salts. The yield and parameters of silver and palladium nanoparticles are affected by the concentration of exopolysaccharides and components of the cytoplasm of cells, which are realized in the culture liquid during the lysis of microorganisms that produce them. It was found that the ratio of microorganisms in the community significantly affects the size of the synthesized metal nanoparticles and their organic shell. The characteristic range of sizes of nanoparticles is unique and corresponds to a certain composition of the community, all other things being equal. A number of studied communities of microorganisms withstand several times more concentrated initial solutions of silver and palladium salts in comparison with monocultures belonging to the communities under study. Optimization of conditions for controlled cultivation of methylotrophic bacterial communities for the synthesis of nanoparticles (medium composition, contact time with salts, growth phase, pH, illumination, etc.) using extremely simple media with methanol as the sole carbon source allows obtaining samples of silver or palladium nanoparticles from 3 nm up to 130 nm with the dominance of a certain fraction. The optimum conditions of biosynthesis providing maximum nanosilver and nano-palladium yields have been selected. [ABSTRACT FROM AUTHOR]

Today, waste of electrical and electronic equipment is a big problem because it contains heavy metals such as copper, cadmium or nickel that cause neurological diseases. In addition, such waste also contains precious metals such as gold and silver, which makes this material really attractive for recovery. One of the fastest-generated groups of electrical and electronic waste is mobile phones. In 2008, the global sale of smartphones reached the level of 140 million units, while in 2015 it is rapidly growing to the level of 1500 million units. The lifespan of phones is also shortened to 8-12 months, which means that in the near future the number of mobile phones will continue to grow. The generated amount of electronic waste, including mobile phones, supports the search for an effective way of processing this waste. The dominant materials in used mobile phones are printed circuit boards (PCBs), which consist of a non-conductive substrate or laminate, conductive copper substrate printed on a laminate or inside a laminate and components attached to the substrate (chips - Ga, In, Ti, Si, Ge, As, Sb, Se and Te), connectors (Au, Ag) and capacitors (Ta, Al). Economically, the most important metals that can be recovered are copper, gold and silver. There are many methods to recover such metals based on pyrometallurgical and hydrometallurgical processes. Hydrometallurgical methods used to recover metals from electronic waste have many advantages over other methods. The paper presents an overview of hydrometallurgical studies of metal recovery from PCBs using various acids. Furthermore, the results of the leaching of printed circuit boards of used cell phones with H2SO4, HCl and HNO3 are presented. Research focused on the recovery of metals such as copper, iron, zinc, tin, aluminum and nickel. [ABSTRACT FROM AUTHOR]