Silver Content Research Articles

Recovery of pure silver from spent silver electroplating solutions via electrochemical process and zinc cementation

Recycling of spent silver electroplating solutions has been investigated via electrowinning and electrorefining in comparison to zinc cementation technique in this research. Two different compositions of transparent and dark waste solutions were used having the remaining silver contents of 17.71 g⸳L-1 and 33.36 g⸳L-1 respectively. The waste solutions were used as an electrolyte in the first step of electrowinning at low current density of 0.015 A⸳cm-2. It was found that increasing electrowinning time from 4 h to 24 h increased the recovery of silver cathode for both types of waste solutions. The optimum electrowinning time was higher than 8 h, giving the recovery of higher than 97.5% and 98.5% purity for 24 h electrowinning. Through the subsequent electrorefining, the electrowon silver cathode was set as the anode, while HNO3 + AgNO3 electrolyte containing high silver content of 120 g Ag/L was used. By controlling the potential at 0.8 V, silver crystal of high purity > 99.9% was obtained. The highest recovery was 99.11% when using silver cathode obtained from electrowinning of the transparent waste solution. Zinc cementation however led to loss of silver in the precipitate form on the zinc metal surface, giving only 86.16% recovery.

Electrosynthesis of silver metallonanocomposites in the 1-vinyl-1.2.4-triazole copolymer matrix with methacrylic acid

Silver nanocomposites were synthesized by the electrochemical method in the matrix of a copolymer of 1-vinyl-1,2,4-triazole with methacrylic acid, by combining the process of electrochemical polymerization with cathodic precipitation of metals on metal electrodes. In the electronic spectra of nanocomposites, absorption bands appear with a maximum in the region of 417–421 nm, which is typical for systems with zero valence silver. The IR spectra show that the polymer structure hardly changes during the formation of nanocomposites and films. The presence of silver in the amorphous polymer phase is indicated by the results of X-ray diffraction studies. The silver content in nanocomposites is 0–9%, which leads to an increase in the viscosity of nanocomposite solutions compared to solutions of the initial copolymers. Transmission electron microscopy data show that the synthesized nanocomposites consist of particles with a diameter of 1–12 nm, predominantly spherical.

Highly transparent antibacterial hydrogel‐polymeric contact lenses doped with silver nanoparticles

AbstractBiocompatible polymers such as poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) are used to prepare hydrogels for biomedical applications, including optical applications such as the manufacture of sensing devices, cosmetic and smart, and medical contact lenses, among others. In this study, three contact lenses were prepared by doping PVP‐PVA supportive hydrogel with 0.1, 0.5, and 1 wt% of laboratory‐manufactured Ag NPs. The work demonstrates the evaluation of vision correction through each lens and the effect of changing the concentration of silver on its refractive index. The simulation involved the design and simulation of an aberrated human eye based on the Liou and Brennan model (LBM), and the insertion of the contact lenses for vision correction using the ZEMAX optical design program. This work also included a study of the antimicrobial properties of the resulting hydrogel contact lenses doped with Ag NPs. The resulting refractive index of one PVP‐PVA‐Ag lens was relatively high at 532 nm = 1.604, which made the lens provide the highest image contrast (the lowest MTF curve degradation) of 0.883 ± 0.027 at 20 cycles/mm and an RMS nearly the Airy disc diameter of 3.983 μm. PVA was used in combination with PVP for stabilizing Ag NPs to give the contact lenses an antibacterial property. Finally, the optimum contact lens with a 1 wt% Ag NPs concentration showed the highest inhibition activity.

Silver Nanoparticles Capped with Poly[(maleic anhydride)-co-(vinyl acetate)

Anhydride containing functional co-polymer, Poly[(maleic anhydride)-co-(vinyl acetate)] (pMAVAc) was synthesized by free radical polymerization reaction presence of methyl ethyl ketone (MEK) media with benzoyl peroxide radical initiation at 80 ◦C. Surface modification of pMAVAc was carried out with silver to obtain size specific silver nanocomposites by well-known chemical-reduction approach. Structural characterizations of the samples were performed spectroscopic measurement and surface morphology identification using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM), respectively. Results obtained from the ATR-FTIR analysis, detection of the characteristic spectrum data of the co-polymer composition in pMAVAc-AgNPs nanocomposite is proof that the co-polymer structure remains unchanged after treatment. The size and morphological properties of the silver nanoparticles were compatible with the characteristic nanomaterial structure and their average size was found to be 35 nm. In addition, as expected, MAVA-AgNPs nanocomposite, the detection of 79.73% Ag by mass is evidence of the high silver content in the material, and it was concluded that the co-polymer was successfully coated with silver. In recent years, considering the increasing importance of biocompatible nanomaterials in drug delivery systems and in pharmaceutical industry, the synthesized nanocomposites are thought to be a useful drug carrier system with potential antibacterial activity.

Optical characteristics of silver-based nano-composites fabricated by an environmentally friendly method

This work presents a simple and environmentally friendly method of synthesis of chitosan and Ag nanocomposites. The structure of the obtained organic matrix was determined by Fourier-transform infrared spectroscopy (FTIR). Formation of chitosan- chitin copolymer was discovered. Nanocomposite films with silver content of 9–71 wt.% were prepared. The microstructure and elemental composition of the obtained films were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The prepared films are characterized by uniform distribution of silver nanoparticles in the organic matrix. Optical properties were studied by diffuse reflectance spectroscopy. The diffuse reflectance spectra of the films have maxima. The increase of the Ag 0 concentration in the nanocomposite films was found to lead to the maximum shift of the diffuse reflectance spectra to longer wavelengths. The optical transitions energies were estimated using the Kubelka–Munk function in combination with the Tauc method.

Yeast-As Bioremediator of Silver-Containing Synthetic Effluents.

Yeast Saccharomyces cerevisiae may be regarded as a cost-effective and environmentally friendly biosorbent for complex effluent treatment. The effect of pH, contact time, temperature, and silver concentration on metal removal from silver-containing synthetic effluents using Saccharomyces cerevisiae was examined. The biosorbent before and after biosorption process was analysed using Fourier-transform infrared spectroscopy, scanning electron microscopy, and neutron activation analysis. Maximum removal of silver ions, which constituted 94-99%, was attained at the pH 3.0, contact time 60 min, and temperature 20 °C. High removal of copper, zinc, and nickel ions (63-100%) was obtained at pH 3.0-6.0. The equilibrium results were described using Langmuir and Freundlich isotherm, while pseudo-first-order and pseudo-second-order models were applied to explain the kinetics of the biosorption. The Langmuir isotherm model and the pseudo-second-order model fitted better experimental data with maximum adsorption capacity in the range of 43.6-108 mg/g. The negative Gibbs energy values pointed at the feasibility and spontaneous character of the biosorption process. The possible mechanisms of metal ions removal were discussed. Saccharomyces cerevisiae have all necessary characteristics to be applied to the development of the technology of silver-containing effluents treatment.

Tuning thermoelectric figure of merit in Ag doped nanostructured PbSnTeSe alloy by entropy and band engineering phenomena

Advanced thermoelectric materials with novel chemistry and structure that exhibit superior functional properties are in high demand in today's scientific scenario. Engineered configurational entropy in bulk thermoelectric materials through complex chemical disorder is an emerging and potential approach to achieve exceptional thermoelectric properties over traditional material systems. In the current study, mechanical alloying (MA) and spark plasma sintering (SPS) were used to synthesize the high-density (>96%) nanocrystalline lead tin tellurium selenium (PbSnTeSe) high entropy alloy (HEA) with varied atomic concentrations of silver (Ag) doping (0–0.9 at%). The high entropy, band engineering and nanostructuring approach synergistically show a remarkable decrease to ultralow thermal conductivity (0.814 W/mK), resulting in a substantial increase in the power factor (14.16×10−4W/mK2). Thus, an excellent figure of merit (ZT=0.891) is achieved in PbSnTeSe doped with 0.9Ag HEA at 573 K, which is estimated as a 225% increase over the pristine PbSnTeSe HEA (ZT=0.396).

Acid-Base and Photocatalytic Properties of the CeO2-Ag Nanocomposites

In this work, CeO2 nanoparticles, as well as CeO2 nanocomposites with plasmonic silver nanoparticles, were synthesized using a simple sol-gel process. The concentration of silver in the composites varied from 0.031-0.25 wt%. Cerium hydroxide dried gel was calcined at temperatures from 125 to 800 °C to obtain CeO2. It was shown that, at an annealing temperature of 650 °C, single-phase CeO2 nanopowders with an average particle size in the range of 10-20 nm can be obtained. The study of acid-base properties showed that with an increase in the calcination temperature from 500 to 650 °C, the concentration of active centers with pKa 9.4 and 6.4 sharply increases. An analysis of the acid-base properties of CeO2-Ag nanocomposites showed that with an increase in the silver concentration, the concentration of centers with pKa 4.1 decreases, and the number of active centers with pKa 7.4 increases. In a model experiment on dye photodegradation, it was shown that the resulting CeO2 and CeO2-Ag nanopowders have photocatalytic activity. CeO2-Ag nanocomposites, regardless of the silver concentration, demonstrated better photocatalytic activity than pure nanosized CeO2.

Uptake of Silver by Jarosite and Natrojarosite Family Compounds at 22 °C, 97 °C and 140 °C

The jarosite family of minerals are part of the alunite supergroup with the general formula AB3(TO4)2(OH)6. Jarosite family minerals are known to incorporate silver (Ag), but the extent to which this occurs, and at what temperature range, is not well constrained. To address this knowledge gap, jarosite compounds with the A site filled with K, Na, Ag and H3O were synthesised at 22 °C, 97 °C and 140 °C to simulate low-, moderate- and high-temperature environments, respectively. The compounds were characterised by XRD, SEM, chemical analysis and Raman spectroscopy. All of the synthesised compounds took up Ag. In general, higher temperatures of synthesis increased alkali and Ag occupancy of the A site of the products. Silver contents increased with the increasing concentration of Ag in the starting solutions at all temperatures. The order of preference for occupancy of the A site in the synthesised solids is K > Na > H3O > Ag at all temperatures, which is consistent with the reported order of ΔGf of −3309 kJ/mol, −3270 kJ/mol, −3247 kJ/mol and −2948 kJ/mol for jarosite, natrojarosite, hydroniumjarosite and argentojarosite, respectively. The results of this study show that Ag can be incorporated in jarosite and natrojarosite at low-to-high temperatures, and therefore, jarosite family minerals can be important stores of Ag in in natural and engineered environments.

Synthesis and investigation of structural and optical properties of CdO: Ag nanoparticles of various concentrations

This study discussed the effects of doping with silver (Ag) on the optical and structural properties of CdO nanoparticles at different concentrations 0, 1, 2, 3, 4, 5 wt% prepared by the precipitation method. The materials were annealed at 550˚C for 1 h. The structural, topographical, and optical properties were diagnosed by X-ray diffraction analysis, atomic force instrument, and visible and ultraviolet spectrometers. The results show that the average diameter of the grains depends on the percentage of added silver to the material, as the diameter decreased from 88.8 to 59.7 nm, and it was found that the roughness increased from 5.56 to 26.5. When studying the optical properties, it was noted that the energy gap was 2.53ev for the pure sample and decreased to 2.38 When 5% of silver concentration was added to cadmium oxide

Facile One-Step Electrospinning Process to Prepare AgNPs-Loaded PLA and PLA/PEO Mats with Antibacterial Activity.

Nanofibers can play an important role in developing new kinds of medical applications. Poly(lactic acid) (PLA) and PLA/poly(ethylene oxide) (PEO) antibacterial mats containing silver nanoparticles (AgNPs) were prepared by a simple one-step electrospinning method that allows AgNPs to be synthesized simultaneously with the preparation of the electrospinning solution. The electrospun nanofibers were characterized by scanning electron microscopy, transmission electron microscopy and thermogravimetry, while silver release over time was monitored by inductively coupled plasma/optical emission spectroscopy. The antibacterial activity was tested against Staphylococcus epidermidis and Escherichia coli by colony forming unit (CFU) count on agar after 15, 24 and 48 h of incubation. AgNPs were found to be mainly concentrated in the PLA nanofiber core, and the mats showed steady but slow Ag release in the short term; in contrast, AgNPs were uniformly distributed in the PLA/PEO nanofibers, which released up to 20% of their initial silver content in 12 h. A significant (p < 0.05) antimicrobial effect towards both tested bacteria, highlighted by a reduction in the CFU/mL counts, was observed for the nanofibers of PLA and PLA/PEO embedded with AgNPs, with a stronger effect exerted by the latter, confirming the more efficient silver release from these samples. The prepared electrospun mats may have good potential for use in the biomedical field, particularly in wound dressing applications, where a targeted delivery of the antimicrobial agent is highly desirable to avoid infections.

The research on photocatalytic oxygen evolution of Bi4Ti3O12 microsphere by different Ag-loading content

The search of catalysts with high efficiency for photocatalytic oxygen evolution by water splitting has always attracted great attention of global scientists. In this study, Ag/Bi4Ti3O12 (Ag/BTO) nanocomposites with surface plasmon resonance (SPR) effect were synthesized by a solvothermal method. Compared with BTO, Ag/BTO narrowed the band gap, improved the absorption intensity in 400–700 nm region, increased the separation efficiency of photo-induced electron-hole pairs, reduced the energy barrier (from 2.18 to 1.39 eV) of the key step (O* → OOH*) from water splitting, and remarkably enhanced the photocatalytic water oxidation ability. The oxygen evolution rate of visible-light-driven 3-Ag/BTO with an appropriate silver content is 2623.51 μmol∙g−1∙h−1, which is 8.39 times higher than that of BTO without any sacrificial agent. Moreover, the excellent performance of 3-Ag/BTO is also obviously higher than that of most reported photocatalysts.

Serum levels of chemical elements and carious lesions in children after antitumor therapy

Aim. To study serum concentrations of trace and macro elements and their correlations in children and adolescents after antitumor therapy, depending on the presence or absence of caries.Materials and methods. The study included 98 patients aged 4 to 17 years who were in remission after an antitumor therapy performed for acute leukemia or lymphomas. Patients with carious tooth lesions were included in group 1 (n = 34) and without caries – in group 2 (n = 64). We used inductively coupled plasma mass spectrometry to calculate the content of essential, conditionally essential and toxic elements in blood serum. The median and interquartile range were calculated, the Mann-Whitney U-test was applied to compare groups, and the Kendall rank correlation coefficient (τ) was calculated for tandem elements.Results. In both groups, the concentrations of the studied elements were within the reference ranges. In group 1, compared with group 2, higher concentrations of potassium, arsenic, iodine and boron and lower concentrations of lithium and tungsten (p &lt; 0.05) were noted. There were no differences in the concentration of phosphorus, calcium, magnesium, manganese, gold, silver, platinum, aluminum, beryllium, bismuth, cadmium, cobalt, chromium, copper, iron, mercury, lithium, molybdenum, nickel, rubidium, antimony, tin, vanadium, zinc, zirconium and thallium between the groups. Significant correlation coefficients in both groups were obtained for the iron/manganese tandem (τ = 0.24, p &lt; 0.05). Different values of τ were got for nickel/ manganese, cobalt/iron, manganese/phosphorus, beryllium/lithium tandems: τ = 0.342 and τ = 0.14; τ = 0.363 and τ = 0.033; τ = –0.111 and τ = –0.326; τ = –0.365 and τ = 0.42, respectively, for groups 1 and 2.Conclusion. In patients in remission after antitumor therapy, an association of caries with an increase (within reference values) in the concentration of essential (potassium, iodine) and conditionally essential elements (arsenic, boron), a decrease in the concentration of lithium and tungsten; as well as a change in the ratio of nickel/manganese, cobalt/iron, manganese/ phosphorus and change the direction of the correlation in the beryllium/lithium tandem was revealed.

Synergistic Antimicrobial Activity of Silver Nanoparticles with an Emergent Class of Azoimidazoles

The combination of two or more agents capable of acting in synergy has been reported as a valuable tool to fight against pathogens. Silver nanoparticles (AgNPs) present a strong antimicrobial action, although their cytotoxicity for healthy cells at active concentrations is a major concern. Azoimidazole moieties exhibit interesting bioactivities, including antimicrobial activity. In this work, a class of recently described azoimidazoles with strong antifungal activity was conjugated with citrate or polyvinylpyrrolidone-stabilized AgNPs. Proton nuclear magnetic resonance was used to confirm the purity of the compounds before further tests and atomic absorption spectroscopy to verify the concentration of silver in the prepared dispersions. Other analytical techniques elucidate the morphology and stability of AgNPs and corresponding conjugates, namely ultraviolet-visible spectrophotometry, scanning transmission electron microscopy and dynamic light scattering analysis. The synergistic antimicrobial activity of the conjugates was assessed through a checkerboard assay against yeasts (Candida albicans and Candida krusei) and bacteria (Staphylococcus aureus and Escherichia coli). The conjugates showed improved antimicrobial activity against all microorganisms, in particular towards bacteria, with concentrations below their individual minimal inhibitory concentration (MIC). Furthermore, some combinations were found to be non-cytotoxic towards human HaCaT cells.

Comparison of Plasma Trace Elements Between 2 Captive Humboldt Penguin (Spheniscus humboldti) Populations.

Environmental pollutants and their effect on wildlife health play an important role in the conservation of endangered species and can be clinically relevant in captive animals too. Data on relevant concentrations of trace elements in captive birds with no known exposures are rare. For this study, silver, arsenic, gold, barium, cadmium, cobalt, chromium, copper, iron, mercury, magnesium, manganese, molybdenum, thallium, selenium, and zinc were measured by inductively coupled plasma mass spectrometry in lithium heparinized plasma samples from 18 Humboldt penguins at 2 zoological collections in Germany. The results showed that the plasma concentrations of silver, arsenic, gold, cadmium, cobalt, chromium, mercury, and selenium differed significantly (P ≤ 0.05) between the 2 penguin collections. The results indicate that the location of the birds has a strong influence on the plasma trace element concentrations. Well water used in the enclosures was suspected to be associated with these significant differences. Trace elemental concentrations in feed (eg, marine fish) and contamination from enclosure construction materials may also play a role. This study could provide a basis for further comparative, biomonitoring, toxicity, and reference interval studies.

Relationship of bioelemental status and changes in the functional state of the lungs in EMERCOM firefighters of Russia

BACKGROUND: Firefighters are characterized by constant interaction with smoke and various combustion products, which, entering the body can, affect the state of the respiratory system.&#x0D; AIM: To study the relationship of the bioelemental status with alterations in the functional state of the lungs in firefighters of the Ministry of Emergency Situations of Russia.&#x0D; METHODS: The work analyzed the data of 97 people from the territorial fire departments of the city of Saint Petersburg, directly involved in firefighting. The firefighters underwent a comprehensive medical examination, including an assessment of the bioelemental status in hair samples by inductively coupled plasma mass spectrometry.&#x0D; RESULTS: As a result of the study, an increase in the content of toxic trace elements in firefighters was revealed in comparison with persons who did not participate in extinguishing the fire. Against the background of an increase in toxic trace elements, there was a decrease in vital ones. The relationship between the concentration of toxic trace elements and the state of the bronchopulmonary system in firefighters was revealed. The interrelation of the concentration of aluminum, silver and cadmium with a decrease in the diffusion capacity of the lungs, broncho obstructive changes and pulmonary fibrosis is shown. A significant increase in the content of silver was found in firefighters with broncho-obstructive changes compared to those with normal bronchial conduction.&#x0D; CONCLUSION: The study illustrated the relationship between the levels of silver, aluminum, and cadmium and development of functional changes in the lungs..

The Effect of Silver Content in ZnO–Ag Nanoparticles on Their Photochemical and Antibacterial Activity

The development of new materials with antibacterial properties is a promising direction in the field of nanotechnology. In this work, ZnO–Ag nanoparticles with a silver content of 0.1–50 at % have been fabricated by the exploding wire method. ZnO–Ag nanoparticles absorb visible light and destroy the model dye Rhodamine B. The introduction of silver into nanoparticles has made it possible to shift the main absorption edge to 1.59–2.74 eV. The determined optimal content of silver in nanoparticles of 12 at % has ensured the degree of Rhodamine B decoloration by 85% within 60 min of exposure to visible light and has completely stopped the growth of E. coli bacteria at a concentration of 15.6 µg/mL. In addition, nanoparticles containing 12 at % silver have sterilized a sample of natural water contaminated with microorganisms. The results obtained offer an efficient method for the synthesis of antibacterial nanocomposites with heterojunctions employing a high-performance technique for producing nanoparticles, namely, the exploding wire method.

Study of electrostatic separation to concentrate silver, aluminum, and silicon from solar panel scraps

PV modules generally contain several metals that are considered critical and/or strategic and can be recovered. They also contain harmful and toxic metals that pose a threat to the environment and human health, which makes the significance of recycling even greater. This study used mechanically processed waste Si–C (polycrystalline silicon) photovoltaic (PV) panels to obtain highly concentrated recycled metals of interest. The PV panels were comminuted and granulometrically separated before the concentration of the metals of interest could be studied in an electrostatic separator. Some parameters of the electrostatic separator were evaluated, such as the applied voltage, rotation speed of the roll, as well as distance and angle of the electrodes for better separation of the metals of interest (copper, silver, aluminum, and silicon). The results were evaluated by X-ray fluorescence analysis and the proportions of each element in the samples were compared. The results obtained showed that in the comminution and particle size separation process, the greatest mass of material (49.22%) is concentrated in the smallest particle size category, which is smaller than 0.5 mm. This particle size also has higher concentrations of silicon, silver, and aluminum. The best results with the electrostatic separator were obtained using an electric potential difference of 38 kV and a rotation speed of 75 rpm (rotation per minute), where it was possible to concentrate silicon, silver, and aluminum.

The Effect of Silver Content in ZnO–Ag Nanoparticles on Their Photochemical and Antibacterial Activity

The Effect of Silver Content in ZnO–Ag Nanoparticles on Their Photochemical and Antibacterial Activity

Gold-rare metal and associated mineralization in the western part of Bolshevik Island, Severnaya Zemlya archipelago

The presented studies are aimed to determine the formation patterns of the gold-rare metal mineralization within one of the most inaccessible Arctic islands of the Russian Federation, Bolshevik Island of the Severnaya Zemlya archipela-go. The relevance of the work is determined by the high probability of discovering a significant in terms of metal reserves deposit, which is proved by many researchers on the example of known large deposits to be a typical feature of sites with gold-rare metal formation. Obviously, only the possibility of discovering and subsequent development of a deposit of a highly liquid type of mineral, gold, can ensure the profitability of mining production on Severnaya Zemlya. It is established that the main geological, mineralogical, and geochemical features of the gold-rare metal mineralization in the Kropotkinsko-Nikitinskaya metallogenic zone of Bolshevik Island correspond to that of similar ore sites in Russia and the world. The occurrences of other formation types revealed in this metallogenic zone suggest a certain zoning in their distribution: mineralization is located in the apical parts of granitoids and in the nearest halo of hornfelses. At a distance, with an exit from the hornfelsed zone, there are occurrences of a cassiterite-sulphide formation with elevated gold and silver content at the top of the ore column, together with an increased amount of polymetallic ores. Occurrences of gold-quartz and gold-sulphide-quartz formations are localized in fault zones, as a rule, farther from granitoids. The total vertical range of gold mineralization exceeds 300 m. The assignment of all types of mineralization in the Kropotkinsko-Nikitinskaya metallogenic zone of Bolshevik Island to a single hydrothermal process is emphasized by the similar isotope composition of lead galena from heterogeneous occurrences, which determines the age of all mineralization at 200-300 Ma.