•Lincomycine, sulfamethoxazole, and iopromide adsorbed onto CNT.•Freundlich isotherm model well fit adsorption of all target compounds.•Adsorption of target compounds more onto single walled CNT than ...multi-walled CNT.•Higher specific surface area of single walled CNT causing it to adsorb more organics.
Engineered carbon nanotubes (CNTs) have shown a great promise for many remediation applications. The adsorption of two antibiotics (lincomycine and sulfamethoxazole) and one contrast medium (iopromide) on single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) was investigated using batch adsorption experiments. These selected pollutants have high detection frequencies in aquatic environments. The adsorption results were compared with those of conventional powdered activated carbon (PAC). Adsorption isotherms for all pollutants on CNTs and PAC were nonlinear and could be described reasonably well with the Freundlich isotherm model. The adsorption generally followed the order SWCNT>PAC>MWCNT. The relatively low adsorption on MWCNT was probably due to its lower specific surface area than other carbon materials. However, correlation of adsorption to the surface area of carbon materials suggests other factors such as properties of adsorbate and type of interaction between pharmaceuticals and CNTs may also contribute to the adsorption processes. Implications of the adsorption results for the removal of pharmaceuticals from aqueous solution using CNTs are briefly discussed.
This study introduces graphited nanodiamond (G-ND) as an environmentally friendly, easy-to-regenerate, and cost-effective alternative catalyst to activate persulfate (i.e., peroxymonosulfate (PMS) ...and peroxydisulfate (PDS)) and oxidize organic compounds in water. The G-ND was found to be superior for persulfate activation to other benchmark carbon materials such as graphite, graphene, fullerene, and carbon nanotubes. The G-ND/persulfate showed selective reactivity toward phenolic compounds and some pharmaceuticals, and the degradation kinetics were not inhibited by the presence of oxidant scavengers and natural organic matter. These results indicate that radical intermediates such as sulfate radical anion and hydroxyl radical are not majorly responsible for this persulfate-driven oxidation of organic compounds. The findings from linear sweep voltammetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy analyses suggest that the both persulfate and phenol effectively bind to G-ND surface and are likely to form charge transfer complex, in which G-ND plays a critical role in mediating facile electron transfer from phenol to persulfate.
Increased production of carbon nanotubes (CNTs) and their widespread application in industrial and consumer products have led to a rise in the release of CNTs into the aquatic environment. CNTs have ...a very strong adsorption affinity for various environmental contaminants; therefore, they may also influence the toxic effects of other pollutants, such as toxic metals. In this study, the effect of two different functionalized carbon nanotubes, carboxylate and polyethyleneimine modified multi-walled carbon nanotubes (C-MWCNTs and N-MWCNT, respectively) on lead toxicity and bioaccumulation was investigated with a freshwater zooplankton Daphnia magna. The acute toxicity results indicate that the different surface properties of the two types of MWCNTs have different effects on lead toxicity to D. magna. The negatively charged C-MWCNT showed a notable decrease in lead toxicity (LC50 value increased from 0.15 mg L-1 to 1.08 mg L-1 in the presence of 10 mg L-1 C-MWCNT), whereas the positively charged N-MWCNT had only a slight effect on lead toxicity (LC50 value increased from 0.15 mg L-1 to 0.16 mg L-1 in the presence of 10 mg L-1 N-MWCNT). The decrease of lead toxicity was related with the reduced bioavailability of free metal form (Pb2+) caused by greater adsorption of lead onto the MWCNTs. The present study suggests that there is a need to consider carefully the complex interaction of CNTs with toxic metals in future ecotoxicological studies.
•There were no significant differences in the acute toxicities of As(V) and Cu.•However, the bioaccumulations of As(V) and Cu were reduced by silver nanoparticle.•Only Cd acute toxicity and ...bioaccumulation were enhanced by silver nanoparticle.
Citrate-coated AgNPs (c-AgNPs) have negatively charged surfaces and their surface interactions with heavy metals can affect metal toxicity in aquatic environments. This study used Daphnia magna to compare the acute toxicities and bioaccumulation of As(V), Cd, and Cu when they interact with c-AgNPs. The 24-h acute toxicities of As(V) and Cu were not affected by the addition of c-AgNPs, while bioaccumulation significantly decreased in the presence of c-AgNPs. In contrast, both the 24-h acute toxicity and bioaccumulation of Cd increased in the presence of c-AgNPs. These toxicity and bioaccumulation trends can be attributed to the interactions between the AgNP surface and the heavy metals. As(V) and c-AgNPs compete by negative charge, decreasing As(V) toxicity. Copper adheres readily to c-AgNP citrate, decreasing Cu bioavailability, and thus reducing Cu toxicity and bioaccumulation. Citrate complexes with divalent cations such as Ca and Mg reduce the competition between divalent cations and Cd on biotic ligand, increasing toxicity and bioaccumulation of Cd. This study shows that surface properties determine the effect of c-AgNPs on heavy metal toxicities and bioaccumulations; hence, further studies on the effect of nanoparticle by it surface properties are warranted.
The indiscriminate use of zinc oxide nanoparticles (ZnO NPs) in daily life can lead to their release into soil environment. These ZnO NPs can be taken up by crops and translocated to their edible ...part, potentially causing risks to the ecosystem and human health. In this study, we conducted pot experiments to determine phytotoxicity, bioaccumulation and translocation depending on the size (10 – 30 nm, 80 – 200 nm and 300 nm diameter) and concentration (0, 100, 500 and 1000 mg Zn/kg) of ZnO NPs and Zn ion (Zn2+) in bok choy, a leafy green vegetable crop. After 14 days of exposure, our results showed that large-sized ZnO NPs (i.e., 300 nm) at the highest concentration exhibited greater phytotoxicity, including obstruction of leaf and root weight (42.5 % and 33.8 %, respectively) and reduction of chlorophyll a and b content (50.2 % and 85.2 %, respectively), as well as changes in the activities of oxidative stress responses compared to those of small-sized ZnO NPs, although their translocation ability was relatively lower than that of smaller ones. The translocation factor (TF) values decreased as the size of ZnO NPs increased, with TF values of 0.68 for 10 – 30 nm, 0.55 for 80 – 200 nm, and 0.27 for 300 nm ZnO NPs, all at the highest exposure concentration. Both the results of micro X-ray fluorescence (μ-XRF) spectrometer and bio-transmission electron microscopy (bio-TEM) showed that the Zn elements were mainly localized at the edges of leaves exposed to small-sized ZnO NPs. However, the Zn elements upon exposure to large-sized ZnO NP were primarily observed in the primary veins of leaves in the μ-XRF data, indicating a limitation in their ability to translocate from roots to leaves. This study not only advances our comprehension of the environmental impact of nanotechnology but also holds considerable implications for the future of sustainable agriculture and food safety.
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•Size of ZnO NPs affects phytotoxicity and bioaccumulation/translocation in bok choy.•Smaller ZnO NPs show greater bioaccumulation and translocation abilities.•However, large-sized ZnO NPs (300 nm) exhibit higher phytotoxicity than smaller ones.•μ-XRF and bio-TEM provide information on the distribution of ZnO NPs within leaves.
The industrial-scale production of Buckminster fullerene C60 elicits concerns over its impact on human health and ecosystems because of the reported, albeit debatable, toxicity. Assessment of the ...overall environment risk requires a good estimate of the level of exposure and careful characterization of the physicochemical properties of C60 in natural aqueous environments. The reported study investigates the role of various environmental factors, i.e., ionic composition, natural organic matter (NOM), and light in dispersion of C60 in the aqueous phase by simple mixing. The presence of NOM greatly enhances C60 dispersion, and the dispersion process is further accelerated by sunlight. At typical NOM concentrations found in natural waters, C60 concentrations of a few to tens of milligrams per liter can occur within 10 days of mixing, regardless of its extremely low water solubility. The rate of dispersing decreases with the increase of ionic strength. However, calcium ions significantly increase C60 concentration in the aqueous phase. Results from UV/vis absorbance characterization strongly suggest that C60 may have been chemically modified when dispersed in an NOM solution in the presence of sunlight. This reaction pathway has significant implication on the fate, transport, and environmental impact of C60 fullerene.
Nanoscale zerovalent iron (nZVI)-based materials are increasingly being applied in environmental remediation, thereby lead to their exposure to aquatic and terrestrial biota. However, little is known ...regarding the toxic effects of surface-modified nZVI on multiple species in the ecosystem. In this study, we systematically compared the toxicities of different forms of nZVIs, such as bare nZVI, carboxymethyl cellulose (CMC)-stabilized nZVI, tetrapolyphosphate (TPP)-coated nZVI and bismuth (Bi)-doped nZVI, on a range of aquatic and terrestrial organisms, including bacteria (Escherichia coli and Bacillus subtilis), plant (Arabidopsis thaliana), water flea (Daphnia magna) and earthworm (Eisenia fetida). The Bi- and CMC-nZVI induced adverse biological responses across all the test systems, except E. fetida, varying from cell death in E. coli and B. subtilis to inhibition of the physiological states in D. magna and A. thaliana. The particle characterization under exposure conditions indicated that the surface modification of nZVI played a significant role in their toxicities by changing their physicochemical properties. The underlying mechanisms by which nZVI induces toxicity might be a combination of oxidative stress and another mechanism such as cell membrane disruption, chlorosis and hypoxia. Overall, our findings could provide important implications for the development of environment-friendly nanomaterials and direct further ecotoxicological researches regarding interspecies exploration.
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•The toxicity of surface-modified nZVIs was investigated with suitable model species.•Bi- and CMC-nZVI caused toxic effects on the tested organisms, except for earthworm.•Oxidative stress via the Fenton reaction mainly contributed to the toxicity endpoints.•Membrane disruption, chlorosis and hypoxia could be additional toxic factors.
The development of methods to monitor manufactured nanomaterials in the environment is one of the crucial areas for the assessment of their risk. More specifically, particle size analysis is a key ...element, because many properties of nanomaterial are size dependent. The sizing of nanomaterials in real environments is challenging due to their heterogeneity and reactivity with other environmental components. In this study, the fractionation and characterization of a mixture of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) of three different sizes were investigated using asymmetrical flow field-flow fractionation (AF4) coupled with UV-Vis spectrophotometry. In particular, the effects of electrolyte composition and natural organic matter (NOM) on the particle size and stability were evaluated. The fractogram peaks (i.e., stability) of three different AgNPs decreased in the presence of both 10 mM NaCl and 10 mM CaCl2, while increased with increasing concentration of humic acid (HA). In addition, the hydrodynamic diameters of AgNPs in both electrolytes slightly increased with an increase of HA concentration, suggesting the adsorption (coating) of HA onto the particle surface. It is also interesting to note that an increase in the particle size depended on the types of electrolyte, which could be explained by the conformational characteristics of the adsorbed HA layers. Consistent these results, AgNPs suspended in lake water containing relatively high concentration of organic carbon (TOC) showed higher particle stability and larger particle size (i.e., by approximately 4 nm) than those in river water. In conclusion, the application of AF4 coupled with highly sensitive detectors could be a powerful method to characterize nanoparticles in natural waters.
In this study, 40nm silver nanoparticles (AgNPs) were synthesized using the citrate reduction method and then the surface of AgNPs was modified by conjugating Cytochrome C (Cyto C) to improve ...stability and to enhance bioactivity and biocompatibility of AgNPs. It is known that Cyto C may undergo conformational changes under various conditions of pH, temperature, ionic strength, etc., resulting in aggregation of the particles. These parameters also affect the size and size distribution of Cyto C–conjugated AgNPs (Cyto C–AgNP). ζ-potential measurement revealed that the adsorption of Cyto C on the surface of AgNPs is saturated at the molar ratio Cyto C/AgNPs above about 300. Asymmetrical flow field-flow fractionation (AsFlFFF) analysis showed that hydrodynamic diameter of AgNPs increases by about 4nm when the particle is saturated by Cyto C. The aggregation behavior of Cyto C–AgNP at various conditions of pH, temperature and ionic strength were investigated using AsFlFFF and UV–vis spectroscopy. It was found that the aggregation of Cyto C–AgNP increases with decreasing pH, increasing temperature and ionic strength due to denaturation of Cyto C on AgNPs and reduction in the thickness of electrostatic double layer on the surface of Cyto C–AgNP.
Asymmetrical flow field-flow fractionation (AsFlFFF) of Cytochrome C–conjugated silver nanoparticles. Display omitted
•AsFlFFF was employed for size analysis of Cyto C–AgNP, and to study aggregation behavior.•Hydrodynamic diameter of AgNP increases by ~5nm when saturated by Cytochrome C.•Aggregation of AgNP increases with decreasing pH and increasing ionic strength.
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•SWNano was developed to predict fate and transport of ENPs in sewers.•Attachment efficiency of TiO2 ENPs-SPMs in sewage was experimentally estimated.•Significant proportions of ...dispersed TiO2 ENPs can heteroaggregate in the sewer.•Assessing ENPs in sewers should precede that in natural water environments.
A new model, SWNano (Sewer-Water Nano), has been developed in the present study that quantitatively simulates the spatio-temporal changes in the concentrations of TiO2 ENPs of dispersed and aggregated forms in the sewage water and sediment of a sewer network. As a brief example of SWNano applications, a small section of the entire sewer network of Seoul, Korea, was chosen to study where the sewage water was experimentally characterized. The predictions of SWNano present important findings that i) heteroaggregation is the most significant process following the advective transport among the fate and transport processes in the sewer pipes, ii) the heteroaggregation of TiO2 ENPs with SPMs in the sewage water can substantially (a few % to more than 50%) reduce the freely dispersed TiO2 ENPs depending on the magnitude of attachment efficiency, and iii) accurate determination of attachment efficiency is of critical importance in predicting the quantity of individual forms of ENPs exiting the sewer system. The predictions strongly suggest that the fate and transport of TiO2 ENPs in the sewer networks be taken into account to improve the assessment of exposure to TiO2 ENPs in the aquatic ecosystems, which warrants further development and use of models like SWNano.
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