Dissolution Of Silver Research Articles

Electrochemical Separation of Pb-Ag-Sb Alloys in the KCl-PbCl2 Melt

Anode dissolution of lead, silver, antimony and liquid lead-bismuth-antimony alloys has been studied by the polarization method depending on the alloy composition in the molten KCl-PbCl2 eutectic. Lead was found to dissolve and to form Pb2+ ions within the whole range of anode current densities in the Pb-Ag-Sb (49.0–28.0-23.0) and Pb-Ag-Sb (11.0-55.0-34.0) melts. The limiting diffusion current of lead dissolution was observed at the anode current density of 0.34 А cm−2 in the Pb-Ag-Sb (5.0-65.0-30.0) alloy. At the anode current densities exceeding these values the antimony dissolution was observed. To define a mechanism of metals electro dissolution, the number of electrons participating in the electrode reactions was calculated. Based on the polarization curves analysis the regime of electrochemical separation of lead alloys was selected. Metallic lead and the remaining Ag-Sb-Pb alloy with the valuable components concentration exceeding 90 wt% were obtained in the laboratory-scale electrolytic cell.

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.

Vapor-Phase-Deposited Ag/Ir and Ag/Au Film Heterostructures for Implant Materials: Cytotoxic, Antibacterial and Histological Studies.

Using gas-phase deposition (Physical Vapor Deposition (PVD) and Metal Organic Chemical Vapor Deposition (MOCVD)) methods, modern implant samples (Ti alloy and CFR-PEEK polymer, 30% carbon fiber) were functionalized with film heterostructures consisting of an iridium or gold sublayer, on the surface of which an antibacterial component (silver) was deposited: Ag/Ir(Au)/Ti(CFR-PEEK). The biocidal effect of the heterostructures was investigated, the effect of the surface relief of the carrier and the metal sublayer on antibacterial activity was established, and the dynamics of silver dissolution was evaluated. It has been shown that the activity of Ag/Ir heterostructures was due to high Ag+ release rates, which led to rapid (2-4 h) inhibition of P. aeruginosa growth. In the case of Ag/Au type heterostructures, the inhibition of the growth of P. aeruginosa and S. aureus occurred more slowly (from 6 h), and the antibacterial activity appeared to be due to the contribution of two agents (Ag+ and Au+ ions). It was found, according to the in vitro cytotoxicity study, that heterostructures did not exhibit toxic effects (cell viability > 95-98%). An in vivo biocompatibility assessment based on the results of a morphohistological study showed that after implantation for a period of 30 days, the samples were characterized by the presence of a thin fibrous capsule without volume thickening and signs of inflammation.

Formation of plasmonic core/shell nanorods through ammonia-mediated dissolution of silver(i)oxide for ammonia monitoring.

Due to the expansion of the aquaculture industry in the world and the importance of controlling ammonia in fish breeding water, high levels of which impose significant damage to fish farming, it is crucial to develop affordable, rapid, and on-site methods for timely and accurate detection of ammonia. In this study, a colorimetric sensor based on the formation of gold/silver core/shell nanorods (NRs) was developed for the rapid detection of ammonia. The sensor functioned by the specific dissolution of silver(i) oxide by ammonia, which triggered the activation of silver ions and the subsequent formation of gold/silver core/shell NRs in the presence of a reducing agent (i.e., ascorbic acid (AA)). This led to changes in the surface composition, size, and aspect ratio of the NRs, which was accompanied by a vivid color change from green to red/orange in less than a minute. The colorimetric sensor was optimized by adjusting the effective parameters, including ascorbic acid, silver ion, and sodium hydroxide concentration as well as pH and reaction time. After the optimization process, the sensor was found to have a linear range from 50 to 800 μmol L-1 (0.85-13.6 ppm). In addition, the application of the sensor was validated by measuring the ammonia content in water samples from rearing ponds for rainbow trout, sturgeon, and tilapia before and after feeding. The sensor's label-free, rapid, user-friendly, naked-eye, and cost-effective operation makes it an attractive option for on-site environmental monitoring of ammonia.

(Invited) Sustainable Recycling of Metals from Solar Cells

The share of solar energy is increasing worldwide, leading to a widespread use of solar panels. Knowing that the 80 Mt of waste solar panels will be produced by 2050, sustainable processes must be designed in order to deal with the inevitable increase of waste solar cells in the coming years.The main advantage associated with recycling is to avoid the inevitable dispersion of hazardous materials in the environment occurring when the solar cells are landfilled. It also reduces the need for primary mineral resources and may reduce the supply risk for important components like silicon wafers, for which the production is concentrated in a few countries. The recycling process applied plays a major role to allow reducing the carbon footprint of solar cells, advocating in favour of sustainable practices for solar cells recycling.Mono-crystalline solar cells representing 90% of the market, it is therefore this kind of solar cells that are more likely to reach their end-of-life soon. Mono-crystalline solar cells are made of an aluminium frame surrounding the solar module. Underneath a glass layer, layers of ethylene vinyl acetate (EVA) encapsulate the solar cell. The solar cell in itself is made of a silicon wafer with aluminium and silver electrode as well as a silicon nitride anti-reflective coating. Recycling of the metals, particularly silver, is the main economic driver for solar cells recycling.Recycling mono-crystalline solar cells involves a mechanical removal of the aluminium frame and the junction box prior to removal of the glass and EVA layers. Different process were evaluated to get rid of EVA. Solvent-assisted dissolution allowed EVA dissolution but it requires the use of harmful solvents and often leads to breakage of the solar cell. Pyrolysis allows to recover the wafer intact while removing the glass and polymers layers. Provided that the thermal treatment is applied under an inert atmosphere, EVA decomposition leads to relatively non-toxic chemicals such as acetic acid. Recent developments include laser assisted would lead to efficient and straightforward removal of EVA.The removal of metals from the solar cells involves the use of harsh chemicals such as hydrofluoric acid for the removal of silicon nitride, nitric acid to solubilise silver and sodium hydroxide for the dissolution of aluminium. Recently, the use of aqueous brines was introduced to recover silver and aluminium from solar cells. A green and re-usable oxidising agent such as iron(III) chloride can be used to oxidise and dissolve silver, as evidenced in Figure 1, which shows a solar cells before (up) and after (down) etching, revealing the removal of the white silver lines.Using water as a solvent, silver dissolution is impossible due to the low chloride content. By increasing the chloride content, oxidation of silver and its dissolution becomes possible due to the formation of iron-chloride and silver-chloride complexes which have a different redox behaviour and a higher solubility. Overall, silver is completely dissolved in about 10 minutes without using any acids or harmful chemical. Silver can be easily recovered by precipitation or cementation, while the oxidising agent can be regenerated using oxygen from air or via electrolytic means. The objective of this presentation is to give an overview of the current recycling options and provide some guidance on the best and more sustainable practices for the complete recycling of solar cells. The choice is guided by techno-economic analysis and life cycle assessment as well as experimental demonstration of the recycling on real waste solar cells. Figure 1

Stability of Carbon Supported Silver Electrocatalysts for Alkaline Oxygen Reduction and Evolution Reactions.

Ag-based electrocatalysts are promising candidates to catalyze the sluggish oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFC) and oxygen evolution reaction (OER) in unitized regenerative fuel cells. However, to be competitive with existing technologies, the AEMFC with Ag electrocatalyst must demonstrate superior performance and long-term durability. The latter implies that the catalyst must be stable, withstanding harsh oxidizing conditions. Moreover, since Ag is typically supported by carbon, the strict stability requirements extend to the whole Ag/C catalyst. In this work, Ag supported on Vulcan carbon (Ag/VC) and mesoporous carbon (Ag/MC) materials is synthesized, and their electrochemical stability is studied using a family of complementary techniques. We first employ an online scanning flow cell combined with inductively coupled plasma mass spectrometry (SFC-ICP-MS) to estimate the kinetic dissolution stability window of Ag. Strong correlations between voltammetric features and the dissolution processes are discovered. Very high silver dissolution during the OER renders this material impractical for regenerative fuel cell applications. To address Ag stability during AEMFC load cycles, accelerated stress tests (ASTs) in O2-saturated solutions are carried out in rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) setups. Besides tracking the ORR performance evolution, an ex situ long-term Ag dissolution study is performed. Moreover, morphological changes in the catalyst/support are tracked by identical-location transmission electron microscopy (RDE-IL-TEM). Voltammetry analysis before and after AST reveals a smaller change in ORR activity for Ag/MC, confirming its higher stability. RRDE results reveal a higher increase in the H2O2 yield for Ag/VC after the ASTs. The RDE-IL-TEM measurements demonstrate different degradation processes that can explain the changes in the long term performance. The results in this work point out that the stability of carbon-supported Ag catalysts depends strongly on the morphology of the Ag nanoparticles, which, in turn, can be tuned depending on the chosen carbon support and synthesis method.

Integrating Navajo Pottery Techniques To Improve Silver Nanoparticle-Enabled Ceramic Water Filters for Disinfection.

Point-of-use treatment technologies can increase access to safe drinking water in rural areas. Sustained use of these technologies is uncommon due to oversight of community needs, user-perceived risks, long-term maintenance, and conflict with traditional practices. Nanosilver-enabled ceramic water filters are unique due to the use of locally sourced materials available at or near the target community; however, technical limitations persist (e.g., nanosilver's uncontrolled release and passivation from sulfide or chloride). This work aims to overcome these limitations by impregnating nanosilver onto ceramics with a Navajo pottery rosin, collected from pinyon trees with a third-generation artisan. Here, we investigate this sustainable and novel material for drinking water treatment; the study ranges from a proof of concept to testing under realistic conditions. Results show that when embedded in a thin film, the biopolymer controlled ionic silver dissolution and prevented silver passivation from sulfide and chloride. When applied to ceramic filters, the biopolymer effectively immobilized nanosilver in a range of waters. Over a 25 day study to emulate household-use conditions, this coating method sustained disinfection of a coculture of Gram-positive and Gram-negative bacteria while controlling biofouling. Overall, the use of this Navajo pottery material can facilitate adoption while providing the needed technological advancement to these widely used treatment devices.

Alkaline pretreatment of a polymetallic sulfide (Fe-Pb-Mn) ore containing silver increases the efficiency of cyanidation by decreasing elemental sulfur content and by exposing sulfide surfaces

Polymetallic sulfide ores are often not amenable to cyanide leaching due to the presence of several elements and minerals capable of interfering with this process. Thus, various strategies, such as chemical pretreatments, are often studied to improve the efficiency of cyanidation. Beyond the results of such strategies, it is important to understand the changes occurring on the mineral samples during these pretreatments. Herein, an alkaline pretreatment was applied to a silver concentrate (∼8 kg Ag/t) composed of polymetallic sulfides (Fe-Pb-Mn), which increased the silver extraction during subsequent cyanidation from 40% to 80% and decreased the cyanide consumption in half (from approximately 60 to 30 kg NaCN/t). X-ray diffraction (XRD) and ICP-MS indicated that the pretreatment could remove significant amounts of elemental sulfur, which is a known cyanicidal agent. The dissolution of significant amounts of sulfur was confirmed by chemical analysis, which also demonstrated that the dissolution of iron, lead, manganese, and silver were negligible during pretreatment. At surface level, X-ray photoelectron spectroscopy (XPS) demonstrated that the pretreatment exposes fresh sulfide surfaces (e. g. pyrite). In addition, the XPS spectra indicated that the pretreatment facilitated the exposure of clean mineral surfaces. The presence of cleaner surfaces suggested a more uniform and less hindered diffusion of leaching agents through the mineral. Indeed, fitting the extraction data to the shrinking core model showed that pretreated samples featured a nearly ideal diffusion-controlled process, while in the case of untreated samples this fitting was less adequate. During cyanidation of both untreated and pretreated samples, lead build-up was detected on the surface (readsorption), which suggested that this phenomenon does not affect the efficiency of a leaching process. This study highlights the importance of combining bulk analytical methods with surface-sensitive techniques to obtain a more complete understanding of leaching processes.

Sequential recovery of copper, nickel, gold, silver and zinc from WPCBs of obsolete mobile phones through hydrometallurgical recycling

Waste printed circuit board (WPCB) of an obsolete mobile phone is a valuable source of base and precious metals. Alternatively, WPCBs also contain various lethal and toxic constituents which introduce ecological impacts while landfilling and incineration. Recycling WPCB is essential to reduce the environmental effects and to recover valuable metals. This article employs a hydrometallurgical route for the sequential recovery of copper, nickel, gold, silver and zinc from WPCBs through leaching, solvent extraction and cementation processes. Initially, the metal clads of WPCBs are used for the leaching of copper, nickel and other base metals without any selective dissolution of gold and silver. Optimal results revealed that dilute nitric acid at room temperature provides effective leaching (99.9%) of copper, nickel and zinc by leaving precious metals gold and silver in the residue. The utilization of phenolic oxime as a solvent extraction reagent revealed the selective recovery of copper and nickel from the leach liquor individually. The availed residue is dissolved in the halide salts in the presence of acidic conditions showing the quantitative dissolution of gold and silver. Solvent extraction with amide-based reagents recovered gold by leaving the silver-rich raffinate. A cementation technique with copper powder is implemented for the precipitation of silver. The proposed approach delivers an effective, eco-friendly and economically feasible process for the sequential recovery of metallic values from WPCBs of obsolete mobile phones.

Heterostructures Based on Noble Metal Films with Ag and Au Nanoparticles: Fabrication, Study of In Vivo Biocompatibility and Antibacterial Activity

In this work, approaches to the formation of multifunctional film heterostructures based on noble metals for the modification of the surface of implant materials (titanium alloy TiAl6V4 and carbon-fiber-reinforced polyetheretherketone CFR-PEEK) are developed. Such heterostructures consist of continuous layers of platinum (Pt) or iridium (Ir) and antibacterial components on their surface, namely silver (nanoparticles or discontinuous films) and gold (nanoparticles). Chemical or physical gas-phase deposition methods were used for their preparation. The influence of the concentration and form of the antibacterial component on the antibacterial activity and in vivo biocompatibility of the film structures was evaluated for the first time. Differences in the dynamics of silver dissolution depending on Ag concentration in the sample and the type of bottom surface (the noble metal layer = Ir, Pt or TiAl6V4) surfaces allowed us to better understand the nature of the antibacterial action against Staphylococcus aureus and Pseudomonas aeruginosa (S. aureus and P. aeruginosa) of Ag/M heterostructures. From in vivo histological studies using rats, the best biocompatibility was shown by the Ag/M heterostructure with a prolonged release of the low fraction of antibacterial component (Ag).

Electrochemical Mechanism of Oxidative Dissolution of Silver Nanoparticles in Water: Effect of Size on Electrode Potential and Solubility.

For the first time, an electrochemical mechanism of oxidative dissolution of silver nanoparticles in aqueous solutions is suggested and substantiated. The dissolution is caused by the occurrence of two interrelated electrochemical processes: (1) silver oxidation on a microanode and (2) oxygen reduction on a microcathode. According to the suggested model, the standard electrode potential of a nanoparticle decreases with a decrease in its size, which leads to an increase in the electromotive force of the oxidative dissolution of silver. A proportional dependence of the solubility of nanoparticles on their standard potential is revealed. An empirical equation is derived that relates the solubility of AgNPs to their electrode potential and size. In the course of oxidation, silver nanoparticles undergo aggregation with a gradual increase in the potential to the value characteristic of the bulk metal. This leads to the deceleration and practical cessation of the dissolution.

Research into percolation leaching of copper and silver from aged tailings

This paper investigates the extraction of silver by percolation leaching of a pelletized sample of aged tailings with organic binder Alcotac® CB6. Laboratory studies of percolation leaching were conducted using a column with a height of 0.5 m and an internal diameter of 56 mm. Pelletization was performed in a drum-type pelletizer with the consumption of Alcotac® CB6 (BASF, Germany) of 800 g/t and the pellet moisture content of 8–10% and size of 8–10 mm. The sample composition was analyzed taking into account the data obtained by optical tests, electron microscopy, X-ray diffraction, local X-ray spectrometry, X-ray fluorescence analysis, and inductively coupled plasma mass spectrometry. The research object was aged tailings of the Zhezkazgan processing plant (Ulytau region, the Republic of Kazakhstan), where copper is mostly represented by oxidized minerals (78.47%) and sulfide minerals (21.53%). The results of physical and chemical analyses conducted to determine the material composition of samples are presented, along with observations over percolation leaching of copper and silver from Zhezkazgan aged tailings. The copper leaching studies included two stages using a sulfuric acid solution as a solvent. The subsequent stage was silver dissolution by cyanide leaching. Copper extraction into the solution comprised 88.55% with a sulfuric acid consumption of 80.0 kg/t; silver extraction comprised 75.31% with a sodium cyanide consumption of 0.55 kg/t. The conducted studies showed the efficiency of using Alcotac® CB6 for percolation leaching of pre-pelletized aged tailings. During leaching, the pelletized material exhibits sufficient porosity and permeability, thus providing access of cyanic solutions to the surface of precious metals.

Antibacterial properties of photochemically prepared AgTiO2 membranes.

Biofouling reduces the membrane performance and has become a problem in many applications. One of the strategies to reduce biofouling is to apply antibacterial materials to the membrane surface, which prevents the attachment and growth of microorganisms. In this study, the surface of flat ceramic supports was covered with TiO2 powder, and silver was applied by photoreduction using a CH3COOAg solution at room temperature. After the photoreduction, AgOx and metallic silver were found on the TiO2 as analyzed by XPS. While a negligible amount of silver was released from the prepared AgTiO2 membranes into water, the dissolution of silver was enhanced in a 0.09 M NaCl solution. The AgTiO2 membranes inhibited the growth of Escherichia coli in dark conditions. The inhibition cannot be explained only by the concentration of silver ions released from the membranes. Microscopic observation showed that direct contact with AgTiO2 kills E. coli. The results showed the possibility of improving the antibacterial activity of membranes by applying an AgTiO2 coating.

Quantifying Silver Dissolution in Primary and Secondary AgO-Zn Batteries

Printable AgO-Zn batteries are highly attractive for wearable devices for their safe chemistry, high energy density, and rechargeability. However, silver dissolution from AgO cathodes limits the shelf life and cycle life of primary and secondary AgO-Zn cells. In this study, factors including electrolyte, cell configuration, and cycling rate on silver dissolution were investigated systematically via precise identification and quantification of dissolved silver species in AgO-Zn cells. The mechanism of silver dissolution is studied by characterizing both dissolved silver species and cathode surfaces with chemical analysis including Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. We found that reducing the complexation step within the two-step reaction of AgO to [Ag(OH)2+x]−x is key to mitigating the silver dissolution, which can be controlled by selecting the proper electrolytic species as well as cycling rate and creating rough surfaces of cathodes.

Silver dissolution and precipitation in an Na2O–ZnO–B2O3 metallization paste glass

AbstractThermally stimulated interactions between silver and glass, that is, silver dissolution as Ag+ and precipitation as Ag0 were studied in two glass series of molar target composition xAg2O–(19 − x)Na2O–28ZnO–53B2O3 with x = 0, 0.1, 0.5, 5 and (19Na2O–28ZnO–53B2O3)+yAg2O with y = 0.01, 0.05. These act as model for low‐melting borate glasses being part of metallization pastes. The occurrence of metallic silver precipitates in melt‐quenched glass ingots demonstrated that silver dissolved only in traces (< 0.01 mol%) in the glasses. The dissolved silver was detected by means of Raman spectroscopy and energy‐dispersive X‐ray spectroscopy. Increasing x in the batch could not lead to a significant increase of the silver ion fraction in the glass as possible in binary silver borate glasses. In situ observation of heated AgNO3 mixed with the base glass frit in a hot stage microscope showed that Ag0 precipitation occurs already at the solid state. At higher temperatures, small droplets of liquid silver were found to move freely within the melt, whereas coalescence caused a stepwise increase of their size. These results contribute to the understanding of formation of silver precipitates in metallization pastes described in the literature.

Efficient recycling of metals from solar cells using catalytic etchants

Due to the recent trend towards increasing renewable energy production, a large proportion of this demand will be addressed by solar energy. This greater consumption of solar cells will inevitably result in an equally large amount of end-of-life material that should be recycled to recover the valuable metal components. In the present work, the dissolution of silver and aluminium from silicon solar cells was investigated using copper(II) chloride and iron(III) chloride as redox catalysts, dissolving up to 95% of the target metals within 10 min. A mixed hydro- and ionometallurgical approach was taken, with a 2-step selective leaching process. Initially, aluminium and other lower value metals are removed using iron(III) or aluminium(III) chloride in water, with the help of ultrasound to delaminate the aluminium layer. Silver is then leached using iron(III) chloride in a choline chloride: water brine. A high recovery of silver (95%) with high purity (98 wt%) is possible just by adding water to the leach liquor to precipitate silver chloride. Use of brines for the processing of metals is a new and interesting approach to replace mineral acids by cheaper and environmentally friendlier solvents.

A comprehensive mechanistic analysis of silver dissolution with the monoethanolamine-copper-ammonium system and the development of a novel leaching technology

In the present research, the novel system of monoethanolamine-copper-ammonium was electrochemically studied to improve our knowledge of the reaction mechanism of silver dissolution. This paper introduces the effect of varying the concentration of monoethanolamine (MEA), ammonium sulfate, copper sulfate and temperature on the silver leaching kinetics and mechanism. The study has been complemented with thermodynamic analysis, characterization techniques (FESEM-EDS), leaching tests with H2O2 as oxidizing agent and electrochemical techniques such as Tafel, linear voltammetry and open circuit potential. The results demonstrate that it is possible to dissolve silver inhibiting the Cu(OH)2 precipitation in the system by increasing the concentration of MEA up to 1.5 M. The anodic polarization of silver reveals that an increase in the MEA concentration from 0.05 to 1.5 M, promotes the silver oxidation kinetics, maintaining the concentrations of 0.3 and 0.8 M of CuSO4 and (NH4)2SO4, respectively. Furthermore, the Tafel analysis shows that an increase in temperature from 15 to 45 °C minimizes the charge transfer coefficient and increases the silver oxidation kinetics using a leaching solution which avoids the precipitation of copper hydroxide species. The electrochemical results reveal the catalytic role of MEA during the silver dissolution and the possibility to eliminate the use of cupric ions while an energetic condition higher than 0.4 V vs SHE is maintained. In the case of silver sulfide dissolution, the results revealed that the reductive decomposition of silver sulfide is favored at a more cathodic potential than −0.6 V vs SHE with the MEA-Na2SO4-(NH4)2SO4 system, this cathodic pre-treatment facilitates the accelerated dissolution of silver from Ag2S using the same MEA leaching system. Finally, it is possible to dissolve 81 % of metallic silver using a conventional batch reactor with the MEA-Na2SO4-(NH4)2SO4-H2O2 novel system at room temperature.

Enhancement of the Negative Capacitance Associated with the Dissolution of Silver by Salt Concentrations by Means of Anodic Stripping Voltammetry

The amount of anodically dissolved charge of silver by linear sweep stripping voltammetry has been observed to be smaller than that of the potentiostatically deposited charge. The imbalance in the charge is opposite to the participation in the double-layer capacitance. This can be explained in terms of the negative capacitive current, which is caused by dipoles of generated redox charge (Ag+) with counterions (NO3−). Lower concentrations of counterions may suppress the capacitance to retain the equality of the charge. This prediction is examined in this work by the oxidation of silver film at various concentrations of NO3− by anodic stripping voltammetry. The capacitance decreased with a decrease in the salt concentrations less than 0.05 mol dm−3. Low concentrations of salts prevent loss of the anodic charge in electroanalysis. This dependence was related with the lifespan of generated silver nitrate dipoles and is described theoretically.

When function is biological: Discerning how silver nanoparticle structure dictates antimicrobial activity

SummarySilver nanomaterials have potent antibacterial properties that are the foundation for their wide commercial use as well as for concerns about their unintended environmental impact. The nanoparticles themselves are relatively biologically inert but they can undergo oxidative dissolution yielding toxic silver ions. A quantitative relationship between silver material structure and dissolution, and thus antimicrobial activity, has yet to be established. Here, this dissolution process and associated biological activity is characterized using uniform nanoparticles with variable dimension, shape, and surface chemistry. From this, a phenomenological model emerges that quantitatively relates material structure to both silver dissolution and microbial toxicity. Shape has the most profound influence on antibacterial activity, and surprisingly, surface coatings the least. These results illustrate how material structure may be optimized for antimicrobial properties and suggest strategies for minimizing silver nanoparticle effects on microbes.

Assessment of the principal factors influencing the silver cyanidation process by using Plackett-Burman experimental design

For decades, the cyanidation process is frequently used for gold and silver extraction, as well as metal extraction as a sub-product of lead, zinc, and copper metallurgy. The present study focuses on the factors that influence silver extraction efficiency, which represents the rate of silver dissolution in a sodium cyanide solution. The screening design of Plackett and Burman has been performed to investigate the variables that have the most impact on the extraction of metal namely temperature, pH, free cyanide concentration, dissolved oxygen level, pulp density, lead nitrate ratio (Pb(NO3)2ratio), and setting time.To evaluate the meaning of the seven variables, twelve experiments were carried out and the result revealed that for a 95% confidence level, the chosen parameters for the model are meaningful in their whole. The following three factors were significant (P<0.05) when it comes to the silver cyanidation process including, setting time, pulp density, and free cyanide concentration. The variance analysis (ANOVA) using a Fisher test has shown that the setting time was considered to have the most significant effect for a significance level of 1% (Fstatistics=22.8328 > Fc=21.2). Likewise, for a 95% confidence level, both pulp density and free cyanide concentration have a major influence on the response. The Pareto diagram results clearly show that pulp density and setting time represent 20% of factors that have 80% effect on the silver extraction. Model validation verified that no statistically relevant distinction was made between the predicted and experimental results with the determination coefficient R2=0.93, this mean that the metal extraction is better fitted to the model and the predictability of the model is adequate to explain 93% of the variation in the dependent variable as a function of factor variation.