Effects Of Nanoscale Zero-valent Iron Research Articles

Priming effects of nZVI on carbon sequestration and iron uptake are positively mediated by AM fungus in semiarid agricultural soils

We investigated the priming effect of nanoscale zero-valent iron (nZVI) on carbon sink and iron uptake, and the possible mediation by AMF (arbuscular mycorrhizal fungi, Funneliformis mosseae) in semiarid agricultural soils. Maize seed dressings comprised of three nZVI concentrations of 0, 1, 2 g·kg−1 and was tested with and without AMF inoculation under high and low soil moistures, respectively. The ICP-OES observations indicated that both low dose of nZVI (1 g·kg−1) and high dose of nZVI (2 g·kg−1) significantly increased the iron concentrations in roots (L: 54.5–109.8 %; H: 119.1–245.4 %) and shoots (L: 40.8–78.9 %; H: 81.1–99.4 %). Importantly, the absorption and translocation rate of iron were substantially improved by AMF inoculation under the low-dose nZVI. Yet, the excess nanoparticles as a stress were efficiently relieved by rhizosphere hyphae, and the iron concentration in leaves and stems can maintain as high as about 300 mg·kg−1 while the iron translocation efficiency was reduced. Moreover, next-generation sequencing confirmed that appropriate amount of nZVI clearly improved the rhizosphere colonization of Funneliformis mosseae (p < 0.001) and the development of soil fungal community. Soil observations further showed that the hyphae development and GRSP (glomalin-related soil protein) secretion were significantly promoted (p < 0.05), with the increased R0.25 (< 0.25 mm) by 35.97–41.16 %. As a return, AMF and host plant turned to input more organic matter into soils for microbial growth and Fe uptake, and such interactions became more pronounced under drought stress. In contrast, high dose of nZVI (2 g·kg−1) tended to agglomerate on the surface of hyphae and spores, causing severe deformation and inactivation of AMF symbionts. Therefore, the priming effects of nZVI on carbon sequestration and Fe uptake in agricultural soils were positively mediated by AMF via the feedback loop of the plant-soil-microbe system for enhanced adaptation to global climate change.

Coupling effect of nanoscale zero-valent iron and sodium lauroyl sarcosinate on the biogas biological upgrading from kitchen wastewater by anaerobic digestion

In this study, nanoscale zero-valent iron (nZVI, 6 g/L) and sodium lauroyl sarcosinate (SLS, 0, 10, 30, 50 and 70 mg/L) were used to promote anaerobic digestion of kitchen wastewater for methane (CH4) generation. The maximum CH4 content, yield and BMP were 96.23%, 250 mL/gVS and 82.46% at SLS dosage of 30 mg/L, respectively; addition of > 50 mg/L SLS resulted in prolonging lag phase time of methane production due to the degradation intermediate lauric acid (LA). In addition, SLS reduced the surface tension of liquid by forming molecular film at the interface, promoting the continuous gas-liquid contact and improving the mass transfer efficiency of hydrogen (H2). The pH values in the two systems remained in the range of 7.54–7.62 and 7.20–7.30, respectively. Enzyme activity assays showed that nZVI/SLS co-addition increased the activities of dehydrogenase (by 13.26∼34.36%) and coenzyme F420 (by 35.37∼82.93%), compared to control. The co-addition of nZVI/SLS could increase extracellular polymeric substances (EPS) production by anaerobic microorganisms; compared with the control, the ratio of protein/polysaccharide increased, indicating that the microbial flocculation ability was promoted. Microbial community structure showed that the relative abundance of Methanomicrobiales and Methanolinea visibly increased from 6.88% and 3.08–17.56%∼30.22% and 5.18∼7.67%, respectively, after the SLS addition.

Rhizosphere effect of nanoscale zero-valent iron on mycorrhiza-dependent maize assimilation.

Rhizosphere effect of nanoscale zero-valent iron (nZVI) is crucial but little reported. Maize seeds were dressed with four nZVI concentrations (0, 1.0, 1.5, 2 g kg-1 ) and inoculated with arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). The SEM images illuminated that excessive nZVI particles (2 g kg-1 ) were agglomerated on the surface of hyphae and spore, causing severe deformation and inactivation of AMF symbionts and thereafter inhibiting water uptake in maize seedlings. This restrained the scavenging effects of enzymatic (superoxide dismutase, peroxidase) and non-enzymatic compounds (proline & malondialdehyde) on ROS, and leaf photoreduction activity andgas exchange ability (p < 0.05). Interestingly, the inoculation with AMF effectively alleviated above negative effects. In contrast, appropriate dose of nZVI, that is, ≤1.5 g kg-1 , can be evenly distributed on the hyphae surface and form the ordered symbionts with AMF. This help massively to enhance hyphae growth and water and nutrient uptake. The enhanced mycorrhizal infection turned to promote rhizosphere symbiont activity and leaf Rubisco and Rubisco activase activity. Light compensation point was massively lowered, which increased photosynthetic carbon supply for AMF symbionts. Particularly, such priming effects were evidently enhanced by drought stress. Our findings provided a novel insight into functional role of nZVI in agriculture and AMF-led green production.

Effect of Nanoscale Zero-Valent Iron on Arsenic Bioaccessibility and Bioavailability in Soil.

Hand-to-mouth activity is considered to be the main way for children to come into contact with contaminated soil, and bioavailability is an important factor affecting their health risk. To reduce soil As risk to humans by oral exposure, nanoscale zero-valent iron (nZVI) has been extensively studied for immobilizing As-contaminated soil, but its efficiency has not been investigated using in vitro assay and its influence on As-RBA. In this study, two contaminated soil samples (A and B) were amended with 1% and 2% (w/w) nZVI for 56 days to study its effect on As fraction by sequence extraction, As bioaccessibility by SBRC assay, and As relative bioavailability (RBA) by the mouse liver and kidney model. Based on the sequence extraction, the As associated with the E1 (exchangeable fraction) and C2 (carbonate fraction) fractions were decreased from 3.00% to 1.68% for soil A and from 21.6% to 7.86% for soil B after being treated with 2% nZVI for 56 days. When assessing As bioaccessibility in all soils treated with nZVI by SBRC assay, it was found that As bioaccessibility was significantly higher in the gastric phase (GP) and lower in the intestinal phase (IP) (p < 0.05), and the bioaccessible Fe concentration decreased significantly from the gastric to intestinal phase at the same time. Based on the mouse liver–kidney model, the As-RBA in soil A increased from 21.6% to 22.3% and 39.9%, but in soil B decreased from 73.0% to 55.3% and 68.9%, respectively. In addition, there was a significant difference between As bioaccessibility based on GP or IP of SBRC assay and As-RBA in two soils after being treated with nZVI for 56 days. To more accurately assess the effects of nZVI human arsenic exposure, As-RBA should be considered in concert with secondary evidence provided through fraction and bioaccessibility assessments. In addition, it is necessary to develop a suitable in vitro assay to predict As-RBA in nZVI-amended soils.

Coupled mechanism of enhanced and inhibitory effects of nanoscale zero-valent iron on methane production and antibiotic resistance genes in anaerobic digestion of swine manure

In this study, the turning point for nanoscale zero-valent iron’s (NZVI) promotion and inhibition effects of methane production coupled with the reduction of antibiotic resistance genes (ARGs) was investigated. Adding 150 mmol/L NZVI increased methane production by maximum of 23.8 %, which was due to the chemical reaction producing H2 and enhancement of direct interspecies electron transfer (DIET) by NZVI. NZVI350 dramatically repressed methane generation by 48.0 %, which might be associated with the large quantity of reactive oxygen species (ROS) and excessive H2 inhibiting the functioning of microorganisms. The fate of ARGs was significantly related to daily methane production, indicating that the more methane production finally generated, the less the abundance of ARGs at last left. The reduction of ARGs was enhanced by maximum of 61.0 %, which was attributed to the inhibition of vertical gene transfer (VGT) and horizontal gene transfer (HGT) caused by steric hindrance associated with NZVI corrosion.

Effects of nZVI and Fe3O4 NPs on anaerobic methanogenesis, microbial communities and metabolic pathways for treating domestic wastewater at ambient temperature

Anaerobic methanogenesis from domestic wastewater is one of the promising way to wastewater resource utilization. In this study, the effects of nanoscale zero-valent iron (nZVI) and nano ferroferric oxide (Fe3O4 NPs) on organic matter removal, methanogenesis, microbial communities, and metabolic pathways in the anaerobic biofilm system for treating domestic wastewater at ambient temperature were studied. The results showed nZVI and Fe3O4 NPs not only promoted the hydrolytic fermentation process of the anaerobic biofilm system, but also facilitated the removal of refractory organic matter. Especially, Fe3O4 NPs improved the methanogenic efficiency, shortened the lag time, and entered the rapid methanogenic stage rapidly. Fe3O4 NPs formed direct interspecies electron transfer (DIET) and symbiotic relationship between the acetic acid oxidizing bacteria and the methanogenic bacteria. Furthermore, Fe3O4 NPs promoted the biosynthesis of F420. In the Fe3O4 NPs system, the CO2-reduced methanogenesis, as the main methanogenic pathway, was enhanced.

Effects of Nanoscale Zero-Valent Iron on Soil-Leaching of Trinitrotoluene Contaminated Soil in Acid Rain Conditions

The study of effects of nanoscale zero-valent iron (nZVI) on soil-leaching of trinitrotoluene (TNT) contaminated soil in the acid rain conditions is aim to the determination of the effect of nZVI which used as treatment material on soil leaching of TNT contaminated soil in raining condition. Research methodology, soil leaching batch reactor was designed for TNT remediation in soil with nZVI. The reactor was divided into three compartments for the different series of the experiment. Three compartments of the experiments were used for 1) TNT-contaminated soil column (without leaching), 2) TNT-contaminated soil was leached with rainwater, and 3) TNT-contaminated soil was mixed with nZVI and leached with rainwater. The leachants in the experiment were distilled water (pH 6-6.5) and artificial rainwater (pH≈5). The results of this study found the highest TNT removal efficiency was obtained from in the leaching column with nZVI, followed by the leaching column without nanoparticles and non-leaching column at 100.00, 37.25, and 10.65 % respectively. The leachant (artificial rain) which was slightly acidic in pH could remove some of TNT. The leachant improved solubility and transformation of nitro group in TNT to amino group by H ions addition. The results of the current study can be used to predict the circumstances of leaching TNT on-site in the rainy season.

Experimental study of the effect of nanoscale zero-valent iron injected on the permeability of saturated porous media

Abstract In a comparison of modified nanoscale zero-valent iron (NZVI), bare NZVI used to remediate deep contaminated groundwater source areas has more advantages. However, the influence of injected bare NZVI deposition on the permeability of aquifer remains unclear, together with which are still the key factors of engineering cost and contamination removal. Hence, this study sought to assess a method of measuring hydraulic conductivity with a constant head device and to examine the permeability loss mechanism of NZVI injected into different saturated porous media, using column tests. The results showed that it was feasible to determine hydraulic conductivity by the constant head device. The permeability loss caused by NZVI injection increased with a decrease in the grain size of the porous media, and was determined by the amount and distribution of NZVI deposition. The NZVI distribution area had a good linear correlation with dispersivity of the porous media. Additionally, although surface clogging occurred in all porous media, the amount of NZVI deposition at the injection point was largest in fine sand, so that its permeability loss was the most; this was more likely to cause hydraulic fracturing and expand the area of the contaminant source zone. These results have implications for NZVI field injection for successful groundwater remediation.

Adsorption of Sb(III) from Aqueous Solution by nZVI/AC: A Magnetic Fixed-Bed Column Study.

The effectiveness of nanoscale zero-valent iron(nZVI) immobilized on activated carbon (nZVI/AC) in removing antimonite (Sb(III)) from simulated contaminated water was investigated with and without a magnetic fix-bed column reactor. The experiments were all conducted in fixed-bed columns. A weak magnetic field (WMF) was proposed to increase the exclusion of paramagnetic Sb(III) ions by nZVI/AC. The Sb(III) adsorption to the nZVI and AC surfaces, as well as the transformation of Sb(III) to Sb(V) by them, were both increased by using a WMF in nZVI/AC. The increased sequestration of Sb(III) by nZVI/AC in the presence of WMF was followed by faster nZVI corrosion and dissolution. Experiments were conducted as a function of the pH of the feed solution (pH 5.0–9.0), liquid flow rate (5–15 mL·min−1), starting Sb(III) concentration (0.5–1.5 mg·L−1), bed height nZVI/AC (10–40 cm), and starting Sb(III) concentration (0.5–1.5 mg·L−1). By analyzing the breakthrough curves generated by different flow rates, different pH values, different inlet Sb(III) concentrations, and different bed heights, the adsorbed amounts, equilibrium nZVI uptakes, and total Sb(III) removal percentage were calculated in relation to effluent volumes. At pH 5.0, the longest nZVI breakthrough time and maximal Sb(III) adsorption were achieved. The findings revealed that the column performed effectively at the lowest flow rate. With increasing bed height, column bed capacity and exhaustion time increased as well. Increasing the Sb(III) initial concentration from 0.5 to 1.5 mg·L−1 resulted in the rise of adsorption bed capacity from 3.45 to 6.33 mg·g−1.

Enhancement effect of nanoscale zero-valent iron addition on microbial degradation of BDE-209 in contaminated mangrove sediment

Chemical and biological methods have been employed to remedy polybrominated diphenyl ether contamination, but the removal of decabromodiphenyl ether (BDE-209) by either method still has limitations. The present study aims to evaluate the combined effect of nanoscale zero-valent iron (nZVI) (from 0.1 to 10%) reduction and microbial debromination on BDE-209 removal in mangrove sediments under an anaerobic condition. During the 12-months incubation, nZVI significantly enhanced BDE-209 removal, with 17.03% to 41.99% reduction in sterilized sediments. The reduction was even higher in non-sterilized sediments with living indigenous microorganisms, achieving 15.80%, 33.50%, 55.83% and 66.95% removal of BDE-209 at 0 (control without nZVI), 0.1%, 1% and 10% nZVI, respectively. In control sterilized sediments, no debromination was found, and debromination occurred according to spiked levels of nZVI, with BDE-153 being the dominant congener. The concentrations of debrominated congeners in non-sterilized sediments also increased with nZVI levels, but were significantly higher than the respective sterilized sediment. The relative proportions of different debrominated congeners in non-sterilized sediments depended on nZVI levels, with BDE-99 being the dominant congener in low nZVI amended sediments but shifted to BDE-153 under high nZVI. Higher concentrations of ferrous iron (Fe2+) were detected in both sterilized and non-sterilized sediments spiked with more nZVI, and their concentrations significantly correlated with BDE-209 removal. Growth of total bacteria in sediments with 1% and 10% nZVI was inhibited within first two months, but their numbers resumed to that in the control at the end of 12 months. The present study demonstrates the synergy between chemical and microbiological methods, and a combination of nZVI and indigenous microorganisms could be an efficient and feasible mean to remedy BDE-209 in contaminated sediments.

Modelling the Effect of Nanoscale Zero-Valent Iron (nZVI), Biochar (BC) and Nanoscale Zero-Valent Iron/Biochar (nZVI/BC) on the Adsorption/Reduction of Nitrobenzene (NB)

In most instances, there exists an inaccuracy in interpretation of adsorption/reduction of substances using linear technique as it can only provide an approximate value of the measured parameter; the specific adsorption rate. This paper provides for the first-time modelling of the effect of nZVI/BC, nZVI and Biochar (BC) on the adsorption/reduction of nitrobenzene as modelled using Pseudo-1st order (PFO), Pseudo-2nd Order (PSO), Elovich and Avrami models. Pseudo-1st Order was the best model for nZVIBCg, whereas Pseudo-2nd Order was the best model for nZVI and BC on Nitrobenzene (NB) removal based on statistical dependencies that were used such as root-mean-squire error (RMSE), bias factor (BF), Akaike information criterion (AICc) and the adjusted coefficient of determination. Justifiably from the results, coupling nZVI and BC together will help in reducing more of NB than when individual compounds are used.

Assessment of sulfamethoxazole removal by nanoscale zerovalent iron

Removal of pharmaceutical compounds, such as sulfamethoxazole (SMX) from the aquatic environments, is critical in order to mitigate their adverse environmental and human health effects. In this study, the effectiveness of nanoscale zerovalent iron (nZVI) particles for the removal of SMX was investigated under varying conditions of initial solution pH (3, 5, 7 and 11) and nZVI to SMX mass ratios (1:1, 5:1, 10:1, 13:1, 25:1). Batch kinetic studies, which were well represented using both pseudo-first-order and pseudo-second-order kinetic models (R2 > 0.98), showed that both solution pH and mass ratios strongly influenced SMX removal. At a fixed mass ratio of 10:1, removal efficiencies were higher in acidic conditions (83% to 91%) compared to neutral (29%) and alkaline (6%) conditions. A similar trend was observed for removal rates and removal amounts. For mass ratios between 1:1 and 10:1, an optimum pH existed (pH 5) wherein highest removal efficiencies were attained. Increasing the mass ratio above 10:1 resulted in virtually complete removal efficiencies at pH 3 and 5, and 70% at pH 7. Analysis of SMX speciation and zeta potential of nZVI particles provided insights into the role of pH on the efficiencies, rates and extents of SMX removal. Total organic carbon analysis and mass spectrometry measurements of SMX solution before and after exposure to nZVI particles suggested the transformation of SMX via redox reactions, which are likely the dominant process compared to adsorption. Five transformation products were observed at m/z 156 (TP1), 192 (TP2), 256 (TP3), 294 (TP4) and 296 (TP5). TP1, TP2 and TP3 were further identified using ion fragment analysis. Overall, results from this study indicate a strong potential for SMX removal by nZVI particles, and could be useful towards identifying reaction conditions for optimum SMX transformation.

Combined effect of nanoscale zero-valent iron and linear alkylbenzene sulfonate (LAS) to the freshwater algae Scenedesmus obliquus

With wide use of nanoparticles, co-exposure of aquatic organisms to nanoparticles and organic pollutants often takes place in the environment. However, the combined effects are still rarely understood. In this study, in order to study the interaction and biological effects of nanoscale zero-valent iron (nZVI) and linear alkylbenzene sulfonate (LAS), which acts as a typical surfactant, the freshwater algae Scenedesmus obliquus was exposed to nZVI and LAS individually and in combination for 96 h. According to the inhibition rate of the algae, the toxic effects were investigated by dose-response analysis. Then the combined effect of nZVI and LAS was evaluated using three evaluation models including toxicity unit (TU), additional index (AI), and mixture toxicity index (MTI). The results showed that the 96 h IC50 of nZVI and LAS to Scenedesmus obliquus was 2.464 mmol L-1 and 0.332 mmol L-1, respectively. When nZVI coexisted with LAS at toxic ratio 1:1, the 96 h IC50 value was 1.658 mmol L-1 (shown with nZVI), and the partly additive effect of nZVI mixed with LAS was confirmed. However, when the toxic ratio of nZVI:LAS was 4:1, it showed synergistic effect. In addition, when nZVI mixed with LAS at toxic ratio 1:4, the joint effect is antagonistic effect. In addition, the content of chorophyll in Scenedesmus obliquus, especially the content of chlorophyll a, was decreased with the increase of mixture dose. However, the protein levels did not show significant changes at different mixture doses.

Effectiveness of nanoscale zero-valent iron for the immobilization of Cu and/or Ni in water and soil samples

In the last few years, the effectiveness of nanoscale zero-valent iron (nZVI) as a treatment for polluted waters and soils has been widely studied. However, little data are available on its efficacy for metal immobilization at low and moderate doses. In this study, the effectiveness of two doses of commercial nZVI (1 and 5%) to immobilize Cu and/or Ni in water and acidic soil samples was evaluated. The influence of the nanoremediation technology on iron availability, physico-chemical soil properties and soil phytotoxicity was also assessed. The results show that the effectiveness of nZVI to immobilize Cu and Ni in water and soil samples was determined by the dose of the nanomaterial and the presence of both metals. Nickel immobilization was significantly decreased by the presence of Cu but the opposite effect was not observed. nZVI showed better immobilization capacity in water than in soil samples. In water, the dose of 5% completely removed both metals, whereas at a lower dose (1%) the percentage of immobilized metal decreased, especially for Ni in Cu + Ni samples. In soil samples, 5% nZVI was more effective in immobilizing Ni than Cu, with a 54% and 21% reduction of leachability, respectively, in single contaminated samples. In Cu + Ni soil samples, nZVI treatment led to a significant decrease in Ni immobilization, similar to that observed in water samples. The application of nZVI induced a dose-dependent increase in available Fe—a relevant effect in the context of soil rehabilitation. Germination assays of Medicago sativa and Vicia sativa seeds revealed that treatment with nZVI did not induce phytotoxicity under the experimental conditions tested, and that the phytotoxicity induced by Ni decreased significantly after the treatment. Thus, the use of nZVI emerges as an interesting option for Cu and/or Ni immobilization in water samples. The effectiveness of nZVI to remove Cu from acidic soil samples was moderate, while for Ni it was strongly dependent on the presence of Cu. These observations therefore indicate that the results in water samples cannot be extrapolated to soil samples.

Impact of nZVI on the formation of aerobic granules, bacterial growth and nutrient removal using aerobic sequencing batch reactor

Abstract The aim of this study was to investigate the effect of nanoscale zero-valent iron (nZVI) on the formation of aerobic granules, nutrient removal and bacterial growth during the treatment process of the municipal wastewater. For this purpose, two sequencing batch reactors (SBR) were simultaneously and automatically operated in a cyclic batch mode with four phases per cycle: feed, react, settle and decant. The sequancial operation of the reactors consisted four cycles per day and lasted for sixty days in which 10 mg/L of nZVI particles were added to the infflent of reactor 2. The reactors were fed with synthetic wastewater (3 liters per cycle) and acclimated with seed sludge collected from a full-scale municipal wastewater treatment plant in Istanbul. The effluent of the reactors was regularly analyzed for nitrate, nitrite, ammonia, phosphate and COD concentrations. In addtion to that, their removal pathways including the direct adsorption to nZVI, utilization by microorganisms and adsorption within the generated granules were discussed. The removal efficiency of COD, ammonia and phosphate kept increasing, and almost a complete removal was observed after the formation of aerobic granules on day 50. Furthermore, after the addition of nZVI to R2 on day 24th, the removal efficiency of ammonia, COD and phosphate slightly improved. The addition of nZVI stimulated the production of Extracellular Polymeric Substances (EPS) in R2 including protein and carbohydrate generation. NGS analysis showed that the addition of nZVI into R2 increased the growth rate of some bacterial species such as Rhizobiales and Xanthomonadales and decreased others such as Clostridiales, confirming that the effect of nZVI on the bacterial growth was genera dependent. The aerobic granules were successfully formed in the reactors in less than 50 days and the addition of nZVI improved to some extent the size and settling rate of the formed granules in R2.

Exploring the effects of nanoscale zero-valent iron (nZVI) on the mechanical properties of lead-contaminated clay

Nanoscale zero-valent iron (nZVI) is a well-known efficient nanomaterial for the immobilization of heavy metals and has been widely applied in the remediation of contaminated groundwater and soils. In this study, a series of field emission scanning electron microscopy (FESEM) analyses, vane shear tests, triaxial compression tests, and oedometer tests was conducted on lead-contaminated clay using four dosages of nZVI treatment (0.2%, 1%, 5%, and 10%). The geotechnical properties, including basic index properties, stiffness, shear strength, and compressibility, were assessed after the reaction procedure. FESEM analysis was performed to explore the potential mechanisms of nZVI treatment in terms of morphological characteristics. It was found that the plasticity index decreased gradually with increasing nZVI dosage. Treating contaminated soil with nZVI caused an increase in the vane shear strength, stiffness, and friction angle. The compression index increased gradually because of the nZVI treatment. Based on the FESEM analysis, a conclusion can be deduced that larger aggregates and conjoined structures resulting from nZVI treatment can lead to the strengthening of lead-contaminated clay.

Influence of nanoscale zero-valent iron and magnetite nanoparticles on anaerobic digestion performance and macrolide, aminoglycoside, β-lactam resistance genes reduction

The effect of nanoscale zero-valent iron (NZVI) and magnetite nanoparticles (Fe3O4 NPs) on anaerobic digestion (AD) performance was investigated through a series of 100-day semi-continuous mesophilic anaerobic digestions. The results indicated that biogas production had increased by 24.44% and 21.66% with the addition of 0.5 g/L Fe3O4 NPs and 1.0 g/L NZVI, respectively. Besides, the abundance of five widespread antibiotic resistance genes (ARGs) (ermF, ermA, ermT, aac(6′)-IB, blaOXA-1) was also studied. The decrease in abundance of aac(6′)-IB and blaOXA-1 was observed during the AD process with an average removal rate of 95.69% and 44.82%, respectively. Most of the ARGs, especially ermA and ermT, were less abundant in NZVI group compared with control group. The overall results suggested that the addition of NZVI and Fe3O4 NPs contributed to a better sludge anaerobic digestion performance, and NZVI was beneficial to the removal of some ARGs.

Physiological effects of zero-valent iron nanoparticles in rhizosphere on edible crop, Medicago sativa (Alfalfa), grown in soil.

We investigated the effects of nanoscale zero-valent iron (nZVI) that has been widely used for groundwater remediation on a terrestrial crop, Medicago sativa (Alfalfa), and comprehensively addressed its development and growth in soil culture. Root lengths, chlorophyll, carbohydrate and lignin contents were compared, and no physiological phytotoxicity was observed in the plants. In the roots, using an omics-based analytical, we found evidence of OH radical-induced cell wall loosening from exposure to nZVI, resulting in increased root lengths that were approximately 1.5 times greater than those of the control. Moreover, germination index (GI) was employed to physiologically evaluate the impact of nZVI on germination and root length. In regard to chlorophyll concentration, nZVI-treated alfalfa exhibited a higher value in 20-day-old seedlings, whereas the carbohydrate and lignin contents were slightly decreased in nZVI-treated alfalfa. Additionally, evidence for translocation of nZVI into plant tissues was also found. Vibrating sample magnetometry on shoots revealed the translocation of nZVI from the root to shoot. In this study, using an edible crop as a representative model, the potential impact of reactive engineered nanomaterials that can be exposed to the ecosystem on plant is discussed.

Effect of nanoscale zero-valent iron on the change of sludge anaerobic digestion process

ABSTRACT Nanoscale zero-valent iron (NZVI), which is increasingly used for environmental remediation, has potential positive impact on Anaerobic Digestion (AD). In this study, the changes of three phases in the AD of sludge have been analysed. The addition of NZVI (1000 mg/L) in the experimental reactors resulted in an enhanced operational performance, i.e. TCOD, SCOD removal and biogas production increased by 23.13%, 12.60% and 29.55% respectively. The addition of NZVI also kept pH at an appropriate level, enhanced the use of volatile fatty acids (VFAs) and the activity of the characteristic enzyme relative to the blank group. The Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) were employed to investigate the changes in surface morphology and elements of the sludge. The infrared spectra analysis showed that NZVI promoted AD of sludge. The results from the three-phase change reflected that the addition of NZVI not only promoted AD of sludge but also improved the resource utilization of sludge.

Roles of extracellular polymeric substances in the bactericidal effect of nanoscale zero-valent iron: trade-offs between physical disruption and oxidative damage

Increased EPS encountered trade-offs between enhanced membrane disruption and decreased oxidative damage to mitigate the bactericidal effect of nZVI.