Fate of Zinc Oxide and Silver Nanoparticles in a Pilot Wastewater Treatment Plant and in Processed Biosolids

Ma, Rui; Levard, Clément; Judy, Jonathan D.; Unrine, Jason M.; Durenkamp, Mark; Martin, Ben; Jefferson, Bruce; Lowry, Gregory V.

doi:10.1021/es403646x

Cited by 330 publications

(259 citation statements)

References 32 publications

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“…It is thus essential to understand clearly the different mechanisms that can be involved in the fate of Ag NPs in the environment, in order to establish a regulation to minimize their environmental impact [117], and to design processes that could be used for the depollution of heavily contaminated effluents [118]. Notably, research is still ongoing to determine whether Ag NPs have a significant impact when they reach wastewater treatment plants [119][120][121], or if chemical changes (and notably sulfidation) [122,123] inactivate them.…”

Section: Fate Of Silver Nanoparticles In the Environmentmentioning

confidence: 99%

Antibacterial activity of silver nanoparticles: A surface science insight

2015

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Summary Silver nanoparticles constitute a very promising approach for the development of new antimicrobial systems. Nanoparticulate objects can bring significant improvements in the antibacterial activity of this element, through specific effect such as an adsorption at bacterial surfaces. However, the mechanism of action is essentially driven by the oxidative dissolution of the nanoparticles, as indicated by recent direct observations. The role of Ag + release in the action mechanism was also indirectly observed in numerous studies, and explains the sensitivity of the antimicrobial activity to the presence of some chemical species, notably halides and sulfides which form insoluble salts with Ag + . As such, surface properties of Ag nanoparticles have a crucial impact on their potency, as they influence both physical (aggregation, affinity for bacterial membrane, etc.) and chemical (dissolution, passivation, etc.) phenomena. Here, we review the main parameters that will affect the surface state of Ag NPs and their influence on antimicrobial efficacy. We also provide an analysis of several works on Ag NPs activity, observed through the scope of an oxidative Ag + release.

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Section: Fate Of Silver Nanoparticles In the Environmentmentioning

confidence: 99%

Antibacterial activity of silver nanoparticles: A surface science insight

2015

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“…Phosphate adsorption to magnetite nanoparticles was also found to occur and to inhibit dissolution, though the study only considered a low pH environment (Daou et al 2007). A study on the transformation of ZnO and Ag in wastewater treatments plants found that Ag was converted to Ag 2 S, indicating that Ag is less likely to react with phosphates; whereas ZnO was transformed to ZnS, Zn 3 (PO 4 ) 2 , and Zn associated with Fe oxyhydroxides (Ma et al 2014). Interestingly, a study on the effect of phosphate impurities in TiO 2 found that its presence improved the suspension stability of TiO 2 (Liu et al 2013a, b).…”

Section: Transformationsmentioning

confidence: 99%

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

2014

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A comprehensive assessment of the environmental risks posed by engineered nanomaterials (ENMs) entering the environment is necessary, due in part to the recent predictions of ENM release quantities and because ENMs have been identified in waste leachate. The technical complexity of measuring ENM fate and transport processes in all environments necessitates identifying trends in ENM processes. Emerging information on the environmental fate and toxicity of many ENMs was collected to provide a better understanding of their environmental implications. Little research has been conducted on the fate of ENMs in the atmosphere; however, most studies indicate that ENMs will in general have limited transport in the atmosphere due to rapid settling. Studies of ENM fate in realistic aquatic media indicates that in general, ENMs are more stable in freshwater and stormwater than in seawater or groundwater, suggesting that transport may be higher in freshwater than in seawater. ENMs in saline waters generally sediment out over the course of hours to days, leading to likely accumulation in sediments. Dissolution is significant for specific ENMs (e.g., Ag, ZnO, copper ENMs, nano zero-valent iron), which can result in their transformation from nanoparticles to ions, but the metal ions pose their own toxicity concerns. In soil, the fate of ENMs is strongly dependent on the size of the ENM aggregates, groundwater chemistry, as well as the pore size and soil particle size. Most groundwater studies have focused on unfavorable deposition conditions, but that is unlikely to be the case in many natural groundwaters with significant ionic strength due to hardness or salinity. While much still needs to be better understood, emerging patterns with regards to ENM fate, transport, and exposure combined with emerging information on toxicity indicate that risk is low for most ENMs, though current exposure estimates compared with current data on toxicity indicates that at current production and release levels, exposure to Ag, nZVI, and ZnO may cause toxicity to freshwater and marine species.

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“…Under acidic conditions (pH of 5), phosphate and Ca 2+ released from HAP resulted a rapid transformation of about 80% ZnO NPs to crystalline scholzite within 4 h. Under neutral and basic conditions (pH of 7 and 9), a slower crystalline to amorphous phase transformation of about 60% ZnO NPs within 30 days was achieved by forming inner-sphere Zn adsorption complexes at the HAP surface. Considering the abundance of insoluble phosphate containing minerals such as HAP in the environment and the fact of Zn phosphate as an important and a persistent transformation product of ZnO NPs [16,17], chemical transformations of ZnO NPs induced by phosphate containing minerals plays a significant role in the behavior, fate and toxicity of ZnO NPs in the environment.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, two field studies have been conducted to investigate chemical transformations of ZnO NPs in wastewater treatment systems. Three transformed species of ZnO NPs including Zn 3 (PO 4 ) 2 , ZnS and Zn associated Fe oxy/hydroxides (Zn-FeOOH) were identified in sludge and biosolids generated by wastewater treatment [16,17]. Zn 3 (PO 4 ) 2 was observed persistent in sludge and biosolids, while the ratio of ZnS and Zn-FeOOH depended on the redox state and water content of the biosolids [17].…”

Section: Introductionmentioning

confidence: 98%

“…Three transformed species of ZnO NPs including Zn 3 (PO 4 ) 2 , ZnS and Zn associated Fe oxy/hydroxides (Zn-FeOOH) were identified in sludge and biosolids generated by wastewater treatment [16,17]. Zn 3 (PO 4 ) 2 was observed persistent in sludge and biosolids, while the ratio of ZnS and Zn-FeOOH depended on the redox state and water content of the biosolids [17]. Therefore, both laboratory and field researches have demonstrated the importance of the chemical transformation of ZnO NPs to Zn 3 (PO 4 ) 2 and validated the role of phosphate in the transformation of ZnO NPs in the environment.…”

Section: Introductionmentioning

confidence: 99%

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