Behavior of Metallic Silver Nanoparticles in a Pilot Wastewater Treatment Plant
05 Apr 2011-Environmental Science & Technology (American Chemical Society)-Vol. 45, Iss: 9, pp 3902-3908
TL;DR: Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h, which must be considered in future risk assessments.
Abstract: We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present a...
Citations
More filters
TL;DR: It can be concluded that the therapeutic window for silver is narrower than often assumed, however, the risks for humans and the environment are probably limited.
Abstract: The antibacterial action of silver is utilized in numerous consumer products and medical devices. Metallic silver, silver salts, and also silver nanoparticles are used for this purpose. The state of research on the effect of silver on bacteria, cells, and higher organisms is summarized. It can be concluded that the therapeutic window for silver is narrower than often assumed. However, the risks for humans and the environment are probably limited.
1,787 citations
TL;DR: In this paper, the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity are discussed.
Abstract: Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentiall...
1,310 citations
TL;DR: The nature and extent of the transformations that occur in nanomaterials must be understood before significant progress can be made toward understanding the environmental risks posed by these materials.
Abstract: Increasing use of engineered nanomaterials with novel properties relative to their bulk counterparts has generated a need to define their behaviors and impacts in the environment. The high surface ...
1,028 citations
TL;DR: True validation of the modeled values is difficult because trace analytical methods that are specific for ENM detection and quantification are not available, and the modeled and measured results are not always comparable due to the different forms and sizes of particles that these two approaches target.
974 citations
Cites background or result from "Behavior of Metallic Silver Nanopar..."
...This result was confirmed (Kaegi et al., 2011) by means of X-ray absorption spectroscopy (XAS) measurements....
[...]
...However, as illustrated by the river water, for the purposes of risk assessment such concentrations have to be used while considering that the majority of the silver is present in wastewater is as a-Ag2S (Kaegi et al., 2011)....
[...]
...Transformation reactions rapidly change the initial form the ENM, which can be very pronounced as exemplified by the case of nano-Ag (Kim et al., 2010; Scheckel et al., 2010; Kaegi et al., 2011; Levard et al., 2012)....
[...]
TL;DR: A critical assessment of the current understanding of silver nanoparticle toxicity is provided and a set of pointers and guidelines for experimental design of future studies to assess the environmental and biological impacts of nanosilver are provided.
Abstract: Nanosilver, due to its small particle size and enormous specific surface area, facilitates more rapid dissolution of ions than the equivalent bulk material; potentially leading to increased toxicity of nanosilver. This, coupled with their capacity to adsorb biomolecules and interact with biological receptors can mean that nanoparticles can reach sub-cellular locations leading to potentially higher localized concentrations of ions once those particles start to dissolve or degrade in situ. Further complicating the story is the capacity for nanoparticles to generate reactive oxygen species, and to interact with, and potentially disturb the functioning of biomolecules such as proteins, enzymes and DNA. The fact that the nanoparticle size, shape, surface coating and a host of other factors contribute to these interactions, and that the particles themselves are evolving or ageing leads to further complications in terms of elucidating mechanisms of interaction and modes of action for silver nanoparticles, in contrast to dissolved silver species. This review aims to provide a critical assessment of the current understanding of silver nanoparticle toxicity, as well as to provide a set of pointers and guidelines for experimental design of future studies to assess the environmental and biological impacts of silver nanoparticles. In particular; in future we require a detailed description of the nanoparticles; their synthesis route and stabilisation mechanisms; their coating; and evolution and ageing under the exposure conditions of the assay. This would allow for comparison of data from different particles; different environmental or biological systems; and structure-activity or structure-property relationships to emerge as the basis for predictive toxicology. On the basis of currently available data; such comparisons or predictions are difficult; as the characterisation and time-resolved data is not available; and a full understanding of silver nanoparticle dissolution and ageing under different conditions is observed. Clear concerns are emerging regarding the overuse of nanosilver and the potential for bacterial resistance to develop. A significant conclusion includes the need for a risk-benefit analysis for all applications and eventually restrictions of the uses where a clear benefit cannot be demonstrated.
865 citations
Cites background or methods or result from "Behavior of Metallic Silver Nanopar..."
...The metal removal model in activated sludge systems includes such processes as physical entrapment of insoluble particles into the floc, active cellular uptake, binding to extra cellular polymers, and volatilization [39] which, according to the results of other studies [45,58], should be relevant also for nanoparticles....
[...]
...[45] metallic silver nanoparticles were transformed into Ag2S within 2 h (in a non-aerated tank)....
[...]
...[45] the behaviour of silver nanoparticles in a pilot wastewater treatment plant (WWTP) was investigated....
[...]
...However, due to sample preparation, nanoparticles cannot be observed in suspension, so if TEM is the only method used [83] the behaviour of the particles in suspension remains largely unknown....
[...]
...The most common one is transmission electron microscopy (TEM) [45,59,79,81,82]....
[...]
References
More filters
TL;DR: A software package for the analysis of X-ray absorption spectroscopy (XAS) data is presented, based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit.
Abstract: A software package for the analysis of X-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data analysis using theoretical standards from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of atomic absorption data. These programs enable high-quality data analysis that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
12,505 citations
TL;DR: The results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.
Abstract: Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.
5,609 citations
TL;DR: These nontoxic nanomaterials, which can be prepared in a simple and cost-effective manner, may be suitable for the formulation of new types of bactericidal materials.
5,309 citations
TL;DR: This is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and the results demonstrate thatsilver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.
Abstract: In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.
3,697 citations
TL;DR: The results of this study indicate that risks to aquatic organisms may currently emanate from nano- Ag, nano-TiO(2), and nano-ZnO in sewage treatment effluents for all considered regions and for nano-Ag in surface waters.
Abstract: Engineered nanomaterials (ENM) are already used in many products and consequently released into environmental compartments. In this study, we calculated predicted environmental concentrations (PEC) based on a probabilistic material flow analysis from a life-cycle perspective of ENM-containing products. We modeled nano-TiO2, nano-ZnO, nano-Ag, carbon nanotubes (CNT), and fullerenes for the U.S., Europe and Switzerland. The environmental concentrations were calculated as probabilistic density functions and were compared to data from ecotoxicological studies. The simulated modes (most frequent values) range from 0.003 ng L−1 (fullerenes) to 21 ng L−1 (nano-TiO2) for surface waters and from 4 ng L−1 (fullerenes) to 4 μg L−1 (nano-TiO2) for sewage treatment effluents. For Europe and the U.S., the annual increase of ENMs on sludge-treated soil ranges from 1 ng kg−1 for fullerenes to 89 μg kg−1 for nano-TiO2. The results of this study indicate that risks to aquatic organisms may currently emanate from nano-Ag, n...
2,258 citations