The effect of sulfate and nitrate ions on the passivation and activation of silver in alkaline solutions

Lesnykh, N. N.; Tutukina, N. M.; Маршаков, И. К.

doi:10.1134/s0033173208050032

Cited by 4 publications

(5 citation statements)

References 3 publications

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“…For Ag, the formation of such complexes has also been described in the past, 28 and the sulfate ions could also play a role in the formation of soluble complexes. 29 Combining the results obtained from the different reactions discussed so far, we propose a reaction pathway for the hydrothermal synthesis of AgCuO 2 , as illustrated in Figure 3. At the beginning of the reaction, the dissolution of CuSO 4 in the 1 M KOH solution induces the precipitation of CuO, 30 as confirmed by the reflections at the beginning of the reaction (Figure 2b).…”

Section: ■ Experimental Sectionmentioning

confidence: 69%

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Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction

Liu

Grendal

Skjærvø

et al. 2020

Crystal Growth & Design

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AgCuO 2 is an interesting semiconductor oxide with appealing optical and electronic properties.While the oxide has been synthesized in bulk by different approaches, no study on the formation mechanism has been carried out to date. We present an in situ time-resolved X-ray diffraction 2 study of the hydrothermal synthesis of AgCuO 2 from AgO and CuO. The effects of reaction pH and temperature on the reaction pathways and products have been studied. While pH is a key parameter for the successful synthesis of AgCuO 2 , temperature affects mainly the reaction kinetics. A reaction pathway is proposed that involves a series of dissolution-precipitation reactions, mediated by Cu and Ag hydroxy complexes. Finally, we have compared different approaches to obtain the reaction activation energy, which was calculated to be 70.6±5.1 kJ/mol. Nevertheless, our results show that new models need to be developed for the type of reaction presented here.

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Section: ■ Experimental Sectionmentioning

confidence: 69%

“…For Cu, it is known that it can form soluble hydroxide complexes in basic solutions. For Ag, the formation of such complexes has also been described in the past, and the sulfate ions could also play a role in the formation of soluble complexes …”

Section: Resultsmentioning

confidence: 87%

Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction

Liu

Grendal

Skjærvø

et al. 2020

Crystal Growth & Design

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Section: Resultsmentioning

confidence: 99%

“…Crystal defects have been reported to increase the chemical reactivity of Ag nanoparticles and surface passivation has been shown to reduce the electro-catalytic property. 27 In order to assess the contribution of surface reactivity to the toxicity of Ag nanoplates more directly, we asked whether surface coating with cysteine could reduce this material's toxicity. Utilizing the cytotoxicity that is induced by 10 μg/mL Ag nanoplates, we demonstrated that increasing the cysteine concentration from 10 to 1000 μM leads to a progressive reduction and even elimination of PI uptake (Figure 6a).…”

Section: Resultsmentioning

confidence: 99%

Surface Defects on Plate-Shaped Silver Nanoparticles Contribute to Its Hazard Potential in a Fish Gill Cell Line and Zebrafish Embryos

et al. 2012

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We investigated and compared nano-size Ag spheres, plates, and wires in a fish gill epithelial cell line (RT-W1) and in zebrafish embryos to understand the mechanism of toxicity of an engineered nanomaterial raising considerable environmental concern. While most of the Ag nanoparticles induced N-acetyl cysteine sensitive toxic oxidative stress effects in RT-W1, Ag nanoplates were considerably more toxic than other particle shapes. Interestingly, while Ag ion shedding and bioavailability failed to explain the high toxicity of the nanoplates, cellular injury required direct particle contact, resulting in cell membrane lysis in RT-W1 as well as red blood cells (RBC). Ag nanoplates were also considerably more toxic in zebrafish embryos in spite of their lesser ability to shed Ag into the exposure medium. In order to elucidate the “surface reactivity” of Ag nanoplates, high-resolution transmission electron microscopy was performed and demonstrated a high level of crystal defects (stacking faults and point defects) on the nanoplate surfaces. Surface coating with cysteine was used to passivate the surface defects and demonstrated a reduction of toxicity in RT-W1 cells, RBC, and zebrafish embryos. This study demonstrates the important role of crystal defects in contributing to Ag nanoparticle toxicity in addition to the established roles of Ag ion shed from spherical nanoparticles. The excellent correlation between the in vitro and in vivo toxicological assessment illustrates the utility of using a fish cell line in parallel with zebrafish embryos to perform a predictive environmental toxicological paradigm.

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“…An additional advantage of the electrolytic method is that the oxidation of silver may be accompanied by its deposition onto a cathode. The oxidation of silver in alkaline media in the presence of chlorides, nitrates, sulfates, and borates has been extensively studied [6][7][8][9][10][11][12]. However, the formation of passivating fi lms composed of silver oxides on the surface of the metallic phase has been frequently observed.…”

mentioning

confidence: 99%

On anodic dissolution of silver coatings deposited on base metals

2012

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Potentiodynamic polarization and potentiostatic electrolysis techniques were employed to study the anodic oxidation of silver and a number of other metals (copper, iron, nickel, and tin) in sulfi te media, both individually and in Ag-M binary electrodes. The conditions in which silver is dissolved with a nearly 100% current effi ciency were found.It is known [1] that a considerable part of metallic silver used for technical and decorative purposes is in the form of surface fi lms deposited onto various substrates. The role of substrates is played by various metals and metal alloys, including copper, iron, nickel, brass, and tin. The optimal process for recovery of silver from scrap articles of this kind is that in which the substrate metal is not dissolved.The conventional methods for recovery of silver [2][3][4][5] are based on its dissolution in the presence of oxidants in solutions of acids or complexing agents, with the subsequent recovery of silver in the form of insoluble salts or its reduction to the metal. The main shortcomings of these methods are the gross expenditure of reagents and the dissolution nonselectivity: substrate metals pass into solution together with silver.A substantially lower expenditure is characteristic of techniques based on the anodic oxidation of silver. In processing of materials containing considerable amounts of base metals, selective transfer of silver into solution is possible in an alkaline medium in which many transition metals form insoluble hydroxides. An additional advantage of the electrolytic method is that the oxidation of silver may be accompanied by its deposition onto a cathode. The oxidation of silver in alkaline media in the presence of chlorides, nitrates, sulfates, and borates has been extensively studied [6][7][8][9][10][11][12]. However, the formation of passivating fi lms composed of silver oxides on the surface of the metallic phase has been frequently observed. Silver is commonly dissolved in special electrolytes [13], including those containing such complexing agents as thiourea [14], rhodanide [15,16], and amino acids [17].A promising complexing agent for these purposes is sodium sulfi te, because sulfi te complexes of silver(I) are rather stable [18]. Compared with the cyanide widely used in hydrometallurgy of silver, the sulfi te ion forms stable complexes with a substantially smaller number of metal ions [18]. In addition, the sulfi te by itself creates an alkaline medium (pH ≈ 9-10) in solution. All this gives reason to expect a high selectivity in recovery of silver(I) into solutions in the presence of other metals.It is known that sulfi te ions are unstable against atmospheric oxygen. The fi nal oxidation product is the sulfate ion (SO 3 2-+ 2OH --2e = SO 4 2-+ H 2 O, E 0 = -0.90 V [19]). Probably, just the widely accepted opinion about fast oxidation by oxygen has hindered development of methods using sulfi te ions as complexing agents, including those for recovery of silver. The kinetics of SO 3 2-oxidation in aqueous solutions was studied in [20,...

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The effect of sulfate and nitrate ions on the passivation and activation of silver in alkaline solutions

Cited by 4 publications

References 3 publications

Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction

Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction

Surface Defects on Plate-Shaped Silver Nanoparticles Contribute to Its Hazard Potential in a Fish Gill Cell Line and Zebrafish Embryos

On anodic dissolution of silver coatings deposited on base metals

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The effect of sulfate and nitrate ions on the passivation and activation of silver in alkaline solutions

Cited by 4 publications

References 3 publications

Reaction Pathway of the Hydrothermal Synthesis of AgCuO2 from In Situ Time-Resolved X-ray Diffraction

Reaction Pathway of the Hydrothermal Synthesis of AgCuO2 from In Situ Time-Resolved X-ray Diffraction

Surface Defects on Plate-Shaped Silver Nanoparticles Contribute to Its Hazard Potential in a Fish Gill Cell Line and Zebrafish Embryos

On anodic dissolution of silver coatings deposited on base metals

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Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction

Reaction Pathway of the Hydrothermal Synthesis of AgCuO₂ from In Situ Time-Resolved X-ray Diffraction