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Mechanisms of Heavy Metal Separation in Bioelectrochemical Systems and Relative Significance of Precipitation
Published in Sonia M. Tiquia-Arashiro, Deepak Pant, Microbial Electrochemical Technologies, 2020
Silver is widely used in jewelry, electronics and photographic industries. It is a precious metal and only exists in nature with limited amounts. The high concentration of some silver compounds is toxic to aquatic life (Naddy et al. 2007). Several methods such as ion exchange, chemical reduction and electrolysis are available to recover or remove silver from aqueous solution (Blondeau and Veron 2010).
Electrochemistry
Published in W. John Rankin, Chemical Thermodynamics, 2019
When silver tarnishes, it combines with sulfur, and a thin layer of black silver sulfide forms on the surface. One way to clean the silver is to physically remove the silver sulfide by polishing with an abrasive or chemical that reacts with the silver sulfide. In both cases, some silver is lost. Another method is to reverse the chemical reaction and turn the silver sulfide back into silver. In this case, the silver remains in place and is not lost. To do this, the item is placed on a sheet of aluminium foil on the bottom of a container and a strong solution of sodium bicarbonate and sodium chloride is added to cover the item. The tarnish will soon begin to disappear. The reaction is faster if the solution is warm.
Regulatory Aspects of Nanotechnology for Food Industry
Published in Lohith Kumar Dasarahally-Huligowda, Megh R. Goyal, Hafiz Ansar Rasul Suleria, Nanotechnology Applications in Dairy Science, 2019
C. Ramkumar, Angadi Vishwanatha, Rahul Saini
Presence of nanoparticles in foods has been linked to colitis, obesity, food allergies, diabetes, colon cancer, and immune dysfunction. Disposal of nanoparticle embedded packaging material may be a matter of environmental concern. The possible contamination of water sources and consumption of fish or other plant and animal foods produced using such contaminated water are likely to be of considerable risk. Nano-silver particles, for example, have a potential for bioaccumulation and persistence and therefore be an environmental hazard. Silver is classified as a hazard because of its toxicity.
Surface morphology of silver thin films exposed to water vapour and/or oxygen in vacuum
Published in Transactions of the IMF, 2022
H. Ohara, M. Kawamura, Y. Abe, T. Kiba
Silver has excellent properties including the highest optical reflectance in the visible light range and the highest electrical conductivity among all metals.1 However, it is prone to agglomeration when heated and tends to degrade under humid conditions.2–5 To address these issues, a protective layer is typically used.6–10 The authors previously reported that an ultrathin aluminium surface layer can be applied to suppress agglomeration. It is believed that the surface layer prevents the formation of a water-absorbing layer on the silver surface directly, thereby retaining the properties of silver. The reflection spectrum of the Al-deposited silver film after the environmental test was almost the same as that of the as-deposited silver film.4,5 Examples of the degradation of Ag nanostructures in a humid atmosphere have been reported by several research groups.11–14 The morphology of silver nanostructures significantly changes in highly humid environments; however, in dry argon, their shape is retained for a long time.12 Furthermore, a reduction in the size of silver nanostructures and the formation of tiny new nanoparticles around them has been reported.11 It is speculated that these changes in shape are caused by the ionisation of silver, its movement through the water layer, and its reduction to metal. The degradation mechanism, however, remains unclear. The effects of oxygen and the presence of water on silver ionisation have been considered to be generally the same as in other metals; however, experimental evidence is yet to be found because the effects of water vapour and oxygen are not separable on experiments in air.
Kinetics of fresh and fermented palm wine (Raphia hookeri) biosynthesized silver nanoparticles and their antibacterial activities
Published in Journal of the Chinese Advanced Materials Society, 2018
Elias E. Elemike, Michael A. Ogbe, Damian C. Onwudiwe, Modupe B. Ayeni, Chinedum O. Mgbemena
Among noble metal nanomaterials, AgNPs have received considerable attention due to their attractive physiochemical properties. The surface plasmon band (SPBs) and large effective scattering cross section of individual AgNPs make them ideal candidates for molecular application. [9,10] In addition, the strong toxicity that silver exhibits in various chemical forms to a wide range of micro-organisms is also very well known. [11]
Characterisation of PET nonwoven deposited with Ag/FC nanocomposite films
Published in Surface Engineering, 2018
WenZheng Xu, XiaoHong Yuan, AnFang Wei, Quan Feng, QuFu Wei
Due to its better adhesion to substrates, low-temperature deposition and environmental friendliness, the magnetron sputtering technique has become a new technology for the surface functionalisation of the textiles, which can prepare metal films, metal oxide films, ceramic films, polymer films and nanocomposite films [5–12]. Metallic silver has excellent electrical, optical and chemical properties. Surface silver-plated textile materials with conductive, antibacterial, excellent electromagnetic shielding properties were successfully prepared by magnetron sputtering [13,14]. But the surface of silver film was rapidly oxidised upon contact with ozone or atomic oxygen at 300 K and ambient pressure [15], Ando and Miyazaki [16] have found that the moisture penetration enhanced the silver migration, improving the crystallinity of the silver layer and decreasing the interfacial adhesion force between the silver layers and substrate. Therefore, it is an urgent demand to develop a material that can be used to block the water vapour and oxygen contact with the silver layer. Polytetrafluoroethylene (PTFE) has excellent thermal and chemical stability, as well as low surface energy, which can be successfully deposited by magnetron sputtering. Huang et al. [17] explored the surface functionalisation of silk fabric by PTFE sputter coating, the contact angle of the PTFE-coated fabric showed a significant increase from 68° to about 138°. Wi et al. [18] employed the PTFE sputtering technique to introduce water repellency onto the surfaces of cotton fabrics and the water contact angle was up to 125°. Schurmann et al. prepared PTFE-Ag nanocomposite films by co-sputtering. The films could be used as optoelectronic materials. It was found that the resistivity changed from 107 to 10−3 V cm−1 when the percolation threshold of silver was at a filling factor of 0.35. The thin composite films showed a high optical absorption in the visible region and a red shift with an increase in silver filling [19].