Nanoscale Zero-valent Iron Nanoparticles Research Articles

A combined experimental and DFT study on the zero valent iron/reduced graphene oxide doped QCM sensor for determination of trace concentrations of As using a Flow-batch system

A sensor based on a gold Quartz Crystal Microbalance (QCM) modified with nanoscale zero-valent iron nanoparticles (nZVI) anchored to reduced graphene oxide (rGO) was developed. An automated measurement microsystem was employed using QCM (modified and unmodified) as an arsine detector device. The QCM measurements of frequency changes are associated with total As concentration (III/V) in the samples. The gold surface QCM modification with nZVI/rGO improved the sensitivity in total As determination. The limit of detection (LOD) was 0.0062 ng mL−1 for QCM-Au/nZVI/rGO, 100 times higher than the unmodified QCM-Au sensor. Moreover, studies of adsorption energy and electron density of As with QCM-Au/nZVI/rGO and QCM-Au systems were performed. For this purpose, Density Functional Theory (DFT) methodology was used employing arsine adsorption on magnetite nanoparticles supported on graphene, and also on Au as models. This theoretical-experimental research allows us to acquire knowledge of the interaction of Au/nZVI/rGO with As and confirms the experimental results.

Lipid production and cellular changes in Fremyella diplosiphon exposed to nanoscale zerovalent iron nanoparticles and ampicillin

With the dramatic decrease in fossil fuel stocks and their detrimental effects on the environment, renewable energy sources have gained imminent importance in the mitigation of emissions. As lipid-enriched energy stocks, cyanobacteria are the leading group of microorganisms contributing to the advent of a new energy era. In the present study, the impact of Nanofer 25 s nanoscale zero-valent iron nanoparticles (nZVIs) and ampicillin on lipid production and cellular structural changes in Fremyella diplosiphon strain B481-SD were investigated. Total lipid abundance, fatty acid methyl ester (FAME) compositions, and alkene production as detected by high-resolution two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC/TOF–MS) was significantly higher (p < 0.05) in the individual application of 0.8 mg/L ampicillin, 3.2 mg/L nZVIs, and a combined regimen of 0.8 mg/L ampicillin and 3.2 mg/L nZVIs compared to the untreated control. In addition, we identified significant increases (p < 0.05) in monounsaturated fatty acids (MUFAs) in F. diplosiphon treated with the combination regimen compared to the untreated control, 0.8 mg/L of ampicillin, and 3.2 mg/L of nZVIs. Furthermore, individual treatment with 0.8 mg/L ampicillin and the combination regimen (0.8 mg/L ampicillin + 3.2 mg/L nZVIs) significantly increased (p < 0.05) Nile red fluorescence compared to the untreated control, indicating neutral membrane lipids to be the main target of ampicillin added treatments. Transmission electron microscopy studies revealed the presence of single-layered thylakoid membranes in the untreated control, while complex stacked membranes of 5–8 layers were visualized in ampicillin and nZVI-treated F. diplosiphon. Our results indicate that nZVIs in combination with ampicillin significantly enhanced total lipids, essential FAMEs, and alkenes in F. diplosiphon. These findings offer a promising approach to augment the potential of using the strain as a large-scale biofuel agent.

Nanoscale zero-valent iron mitigates arsenic mobilization and accumulation in Sinapis alba grown on a metal(loid)-polluted soil treated with a dunite mining waste-compost amendment

Background and aimThe use of amendments to immobilize metals in polluted soils is a widely accepted remediation approach, and in the framework of the circular economy, amendments produced from mining and/or biomass waste have gained relevance. However, the application of such amendments can also mobilize metalloids. Here we propose the combination of nanoscale zero-valent iron nanoparticles (nZVI) with dunite (mining waste) and compost for the remediation and restoration of soil affected by high concentrations of As and metals.MethodsTo this end, we treated pots containing the polluted soil with combinations of dunite, compost, and nZVI for 75 days. In addition, Sinapis alba was used to evaluate the effects of the amendments on pollutant accumulation in the plant. The mobility of the pollutants was monitored through TCLP extraction and by sampling pore water. Furthermore, pH, available P, and cation exchange capacity (CEC) were also determined.ResultsDunite application led to the immobilization of metals, and supplied Mg, thus improving CEC. On the other hand, compost increased nutrient content, and also promoted plant growth. However, this amendment caused a dramatic increase in As accumulation in the plants. Finally, the application of nZVI in combination with the other two amendments was found to be the most appropriate strategy since it not only prevented As mobilization and accumulation but also added nutrients to the soil, thus promoting plant growth.ConclusionThe combination of nZVI with dunite mining waste and compost proved effective for the remediation of soil simultaneously polluted by As and metals.

Mechanism enhanced active biochar support magnetic nano zero-valent iron for efficient removal of Cr(VI) from simulated polluted water

This work focused on the use of low-cost magnetic biochar adsorbent prepared from Litchi chinensis peel for the Cr(VI) amelioration through the reduction-adsorption process. This magnetic biochar was prepared by the pyrolysis process, where the nano zerovalent iron (nZVIO) was decorated on the surface of Litchi peel biochar (LPBC). The XRD and TEM studies indicated that the nano-scale zerovalent iron nanoparticles were crystalline having a particle size of 5 ± 0.1 nm. The BET analysis showed the mesoporous nature of the material with good surface area (124 m2/g) and also material has a magnetic saturation value of 0.176 emu/g, where as surface area of LPBC were 325 m2/g and Ms valie 1.1 emu/g respectively. Three factorial Box–Behnken experimental design was simulated for Cr(VI) removal by taking key parameters initial concentration, adsorbent dose, and initial pH as independent factors. The optimum values obtained from desirability function and given by the model were initial Cr(VI) concentration of 5.87 mg/L, 3.14 for pH, and 0.195 g/L for adsorbent dose, which resulted in approximately 95.38% removal of Cr(VI) in these optimum conditions. Langmuir isotherm and pseudo-second-order kinetics data were explained in the adsorption studies. The adsorbent has an adsorption capacity of 98.36 mg/g at the obtained optimized conditions. The thermodynamics study specified a spontaneous process for Cr(VI) removal. The adsorption mechanism was detailed by XPS analysis which indicated a reduction of Cr(VI) to Cr(III) then adsorption of Cr(III) on the adsorbent surface.

Zero-Valent Iron Nanoparticles Induce Reactive Oxygen Species in the Cyanobacterium, Fremyella diplosiphon.

Nanoscale zero-valent iron nanoparticles (nZVIs) are known to boost biomass production and lipid yield in Fremyella diplosiphon, a model biodiesel-producing cyanobacterium. However, the impact of nZVI-induced reactive oxygen species (ROS) in F. diplosiphon has not been evaluated. In the present study, ROS in F. diplosiphon strains (B481-WT and B481-SD) generated in response to nZVI-induced oxidative stress were quantified and the enzymatic response determined. Lipid peroxidation as a measure of oxidative stress revealed significantly higher malondialdehyde content (p < 0.01) in both strains treated with 3.2, 12.8, and 51.2 mg L–1 nZVIs compared to untreated control. In addition, ROS in all nZVI-treated cultures treated with 1.6–25.6 mg L–1 nZVIs was significantly higher than the untreated control as determined by the 2′,7′-dichlorodihydrofluorescein diacetate fluorometric probe. Immunodetection using densitometric analysis of iron superoxide dismutase (SOD) revealed significantly higher SOD levels in both strains treated with nZVIs at 51.2 mg L–1. In addition, we observed significantly higher (p < 0.001) SOD levels in the B481-SD strain treated with 6.4 mg L−1 nZVIs compared to 3.2 mg L–1 nZVIs. Validation using transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDS) revealed adsorption of nZVIs with a strong iron peak in both B481-WT and B481-SD strains. While the EDS spectra showed strong signals for iron at 4 and 12 days after treatment, a significant decrease in peak intensity was observed at 20 days. Future efforts will be aimed at studying transduction mechanisms that cause metabolic and epigenetic alterations in response to nZVIs in F. diplosiphon.

Mechanisms of enhanced hexavalent chromium removal from groundwater by sodium carboxymethyl cellulose stabilized zerovalent iron nanoparticles

Chromium (Cr) contamination poses serious threats to the environment and human health. Thus, batch and column experiments were performed to investigate hexavalent chromium [Cr (VI)] removal from solution and porous media using nanoscale zerovalent iron nanoparticles (NZVI) stabilized by sodium carboxymethyl cellulose (CMC). Batch experiments indicated that the mass ratio of Fe/CMC = 1, the presence of 150–200 mg L−1 CMC and lower ionic strength led to optimum Cr (VI) removal in aqueous solution. Column experiments demonstrated that Cr (VI) removal was enhanced with decreasing solution pH and increasing CMC-NZVI concentration. The presence of CMC can increase Cr (VI) removal by NZVI in both aqueous solution and porous media by complexation precipitation of Cr (VI) compounds and better dispersion of NZVI. X-ray photoelectron spectroscopy (XPS) analysis revealed that an appropriate amount of CMC supported the redox reaction of Cr (VI) and NZVI. The removal of Cr (VI) through columns was 20.8% and 88.5% under no additional CMC and optimized CMC content, respectively. However, Cr (VI) removal decreased to 64.6% under excessive CMC content. The CMC modified NZVI nanoparticles were characterized by XRD, XPS and TEM techniques. These findings imply that CMC can be used as an effective stabilizer on NZVI which can in turn be applied for the efficient removal of Cr (VI) from industrial wastewater and groundwater.

Facile preparation of magnetic graphene oxide/nanoscale zerovalent iron adsorbent for magnetic solid‐phase extraction of ultra‐trace quinolones in milk samples

A simple pH-responsive magnetic solid-phase extraction method was developed using graphene oxide-coated nanoscale zerovalent iron nanoparticles as an efficient adsorbent prior to high-performance liquid chromatography-tandem mass spectrometry for determination of ultra-trace quinolones in milk samples. Various parameters affecting maghemite synthesis and separation such as pH of sample solution, amount of magnetic adsorbent, eluent type, and volume were optimized. The limits of detection are from 3.1 to 13.3ng/L. The intra- and interprecision values are in the range of 2.9-6.9% and 7.6-15.1%, respectively. Recoveries are from 82.4 to 103.9%. Therefore, this simple and sensitive method is suitable for detecting ultra-trace quinolone residues in milk.

Impact of Zero-Valent Iron Nanoparticles on Fremyella diplosiphon Transesterified Lipids and Fatty Acid Methyl Esters.

Efforts to enhance the transformative potential of biofuels is an important step to achieving an environment-friendly and sustainable energy source. Fremyella diplosiphon is an ideal third-generation biofuel agent due to its ability to produce lipids and desirable essential fatty acids. In this study, the impact of Nanofer 25s nanoscale zero-valent iron nanoparticles (nZVIs) on total lipid content and fatty acid composition of F. diplosiphon strains SF33 and B481 was investigated. We observed significant increases (P < 0.05) in the growth of F. diplosiphon treated with 0.2–1.6 mg L–1 Nanofer 25s, indicating that trace concentrations of nZVIs were not toxic to the organism. Chlorophyll a, carotenoids, and phycobiliprotein levels were not altered in F. diplosiphon treated with nZVIs ranging from 0.4 to 1.6 mg L–1, confirming that these concentrations did not negatively impact photosynthetic efficacy. In addition, Nanofer 25s ranging from 0.2 to 1.6 mg L–1 had an optimal impact on SF33 and B481 total lipid content. We identified significant increases in unsaturated fatty acid methyl esters (FAMEs) from F. diplosiphon Nanofer 25s-treated transesterified lipids. Theoretical chemical and physical biofuel properties revealed a product with elevated cetane number and oxidative stability for both strains. Scanning electron microscopy and energy-dispersive X-ray spectroscopy validated the localization of nZVIs. Our findings indicate that Nanofer 25s nZVIs significantly enhance F. diplosiphon total lipid content and essential FAMEs, thus offering a promising approach to augment the potential of the cyanobacterium as a large-scale biofuel agent.

Insights into endocrine-disrupting Bisphenol-A adsorption from pharmaceutical effluent by chitosan immobilized nanoscale zero-valent iron nanoparticles

Bisphenol A (BPA) in the aquatic environment have adverse effects on human health and other living organisms. BPA at low traces can lead to cardiovascular disease, type II diabetes, and impaired hepatic enzymes. For efficient BPA removal, chitosan immobilized nanoscale zero-valent iron (nZVI-chitosan) nanoparticles were synthesized and used as adsorbent. Since the BPA removal efficiency depends on independent process variables like nZVI-chitosan dosage, initial BPA concentration, pH and contact time, experiments were conducted systematically. To characterize the interaction effect of these variables, the experimental matrix is designed using response surface methodology (RSM). The isothermal and kinetic model parameters are estimated using differential evolution optimization (DEO), and these parameters better represent adsorption behaviour. The batch adsorption experiments indicated that the BPA adsorption on to nZVI-chitosan follows pseudo 1st order kinetic models. The maximum extent of BPA adsorption was 65.16 mg/g based on the Langmuir isotherm model. DEO based model parameters better fit the non-linear models with high R2 and lower RMSE. The regenerability experiments indicate that synthesized nZVI-chitosan adsorbent can be used up to three cycles with removal efficiency over 50%. The thermodynamic studies indicated that ΔG° is negative signifying a favourable and spontaneous adsorption process. The inhibition effects of coexisting ions on BPA adsorption followed the order of Mn2+ > Ca2+ > Mg2+ > Fe2+ for cations and of SO42− > NO3− > Cl− for anions. The BPA removal from real pharmaceutical wastewater is 93.8% obtained for optimal initial BPA concentration of 6 mg/L, an adsorbent dosage of 1.5 g/L, with solution pH of 3 and adsorption time of 1 h, whereas this removal efficiency is 95% for synthetic wastewater.

Exploration of the reactivity of nanoscale zero-valent iron (NZVI) associated nanoparticles in diverse experimental conditions

The bimetallic nanoparticles have been used to improve the reactivity of Nanoscale Zero-Valent Iron (NZVI) during environmental contamination remediation. The main objective of this research was to determine the reactivity of the metal-doped NZVI (bimetallic) nanoparticles in aqueous solutions. In this study, FeCu, FeNi and FeAg bimetals were synthesized through the chemical reduction of ferric chloride with sodium borohydride then deposition of 1% (wt/wt) of the corresponding metal. The reactivity of these bimetallic nanoparticles in specific reaction conditions being; temperature, oxygen supply, pH, dosage and interferences (nitrate and phosphate) was studied. The results revealed that more iron dissolution was in acidic pH, high dosage (3 g/L) and continuous oxygen supply. Furthermore, nitrate was removed more in alkaline pH due to co-precipitation whereas phosphate was adsorbed more in acidic pH due to the positively charged surface that attracts negatively charged species. FeCu, FeNi and FeAg showed the best dissolution of iron in 90 °C, 5 °C and 25 °C respectively. Loaded metals (Cu, Ni, Ag) catalyzed NZVI reaction, promoted electrons’ transfer and minimized oxidation.

Nanoscale zero valent iron supported on MgAl-LDH-decorated reduced graphene oxide: Enhanced performance in Cr(VI) removal, mechanism and regeneration.

The scaled application of nanoscale zero-valent iron nanoparticles (nZVI or Fe° NPs) in environmental remediation is challenged by easy surface passivation and particle aggregation. To improve this situation and enhance their performance in Cr(VI) removal from water phase, we present one novel strategy to hybridize nZVI with layered double hydroxide (LDH) decorated reduced graphene oxide (rGO). The as-prepared ternary (Fe@LDH/rGO) composites possess better dispersibility, improved hydrophilicity and more positive surfaces that allows higher removal efficiency and capacity for Cr(VI) oxyanions. Composition proportion are optimized and influences of surroundings (solution pH, Cr(VI) concentration and temperature) are evaluated. Also, we demonstrate that Fe@LDH/rGO can be reused with suitable post-treatments, which combines alkaline solution desorption and NaBH4 revivification possess. Cr desorption and Fe leaching ratio during regeneration should be critical indicators that determine the recovery efficiency. Synergistic effect within this ternary system not only contributes to its superiorities in stability, but also continuous iron corrosion via the formation of micro Fe-C batteries, where rGO acts as cathode and alternative electron conductor. The present work suggests great potentials of Fe@LDH/rGO composites in groundwater remediation.

Porous-Carbon-Confined Formation of Monodisperse Iron Nanoparticle Yolks toward Versatile Nanoreactors for Metal Extraction.

All-in-one architectures in which uniform nanoscale zero-valent iron nanoparticles are wrapped in hollow porous carbon shells are highly desirable for environmental applications such as wastewater treatment and for use as catalysts, but their preparation remains a significant challenge. Herein, a spatially confined strategy for the in situ preparation of uniform Fe0 @mC (mC=micro/mesoporous carbon) yolk-shell nanospheres, in which the iron nanoparticles are encapsulated in thin, porous carbon shells, is reported. The elaborately designed Fe0 @mC yolk-shell nanospheres were obtained by utilizing silica- and phenolic-resin-coated magnetite nanoparticle core-shell structures as templates by means of selective etching and in situ thermal reduction. The highly dispersed iron nanoparticles with superior reduction capability can effectively remove metal pollutants (e.g., AuIII , AgI , and CuII ), the carbon shell acts as protective cover and prevents aggregation of iron nanoparticles, and the void space in the capsules serves as a reactor for reduction and catalytic reactions.

Dechlorination of p-Chlorophenol by Fe-Pd Nanoparticles Promoted by Poly (γ-glutamic acid)–Dopamine Composite

Palladium-doped nanoscale zerovalent iron nanoparticles (Fe-Pd NPs) was fabricated and stabilized by poly (γ-glutamic acid)–Dopamine composite (PGA-DA). The fabricated nanoparticles had high dechlorination activity towards p-Chlorophenol (p-CP). PGA-DA modified Fe-Pd NPs significantly outperformed PGA modified ones in catalytic activities even in weak alkaline condition. Fe-Pd NPs@PGA-DA (10 mg PGA-DA and 0.4 wt% Pd loading) could achieve 100 % p-CP removal within 60 min. It is worth mentioning that the presence of DA alone could overwhelm dechlorination capacity of Fe-Pd NPs toward p-CP. The coordination bonding between catechol and Fe ions was also investigated in detail. This study demonstrated that PGA-DA is a promising modifier and stabilizer for Fe-Pd NPs, which was expected to be applied in real environmental remediation technology.

Recyclable nanoscale zero-valent iron-based magnetic polydopamine coated nanomaterials for the adsorption and removal of phenanthrene and anthracene

In this study, nanoscale zero-valent iron nanoparticles (NZVIs) were coated with silica and polydopamine using a two-step process. The coated nanoparticles were applied as adsorbents for removal of two common polycyclic aromatic hydrocarbons pollutants, phenanthrene (PHE) and anthracene (ANT) from aqueous system. Adsorption kinetics followed a pseudo-second-order model. Isotherms and thermodynamics were investigated and the results indicated that the adsorption process fit best to the Freundlich model and exhibited the characteristics of an exothermal physical adsorption process. Owing to their superparamagnetic characteristics and stability, these adsorbents could be easily collected and recycled for reuse.

Ecotoxicological impact of two soil remediation treatments in Lactuca sativa seeds

Pharmaceuticals have been identified as environmental emerging pollutants and are present in different compartments, including soils. Chemical remediation showed to be a good and suitable approach for soil remediation, though the knowledge in their impact for terrestrial organisms is still limited. Therefore, in this work, two different chemical remediation treatments (Fenton oxidation and nanoremediation) were applied to a soil contaminated with an environmental representative concentration of ibuprofen (3 ng g−1). The phytotoxic impact of a traditional soil remediation treatment (Fenton oxidation) and of a new and more sustainable approach for soil remediation (nanoremediation using green nano-scale zero-valent iron nanoparticles (nZVIs)) was evaluated in Lactuca sativa seeds. Percentage of seed germination, root elongation, shoot length and leaf length were considered as endpoints to assess the possible acute phytotoxicity of the soil remediation treatments as well as of the ibuprofen contaminated soil. Both chemical remediation treatments showed to have a negative impact in the germination and development of lettuce seeds, exhibiting a reduction up to 45% in the percentage of seed germination and a decrease around 80% in root elongation comparatively to the contaminated soil. These results indicate that chemical soil remediation treatments could be more prejudicial for terrestrial organisms than contaminated soils.

Sorptive removal of arsenite [As(III)] and arsenate [As(V)] by fuller’s earth immobilized nanoscale zero-valent iron nanoparticles (F-nZVI): Effect of Fe0 loading on adsorption activity

Fuller’s earth immobilized nanoscale zerovalent iron (F-nZVI 1–8) were synthesized by borohydride reduction method. The iron loading of fuller’s earth immobilized nZVI was varied from 5 to 50% (w/w) in these F-nZVI 1–8. The F-nZVI 1–8 were characterized by FE-SEM–EDX, FTIR, BET, XRD and TGA. The FE-SEM analysis showed an increase in agglomeration of nZVI on the immobilized material with increase in the loading of Fe0. F-nZVI 1–8 were studied for adsorptive removal of As(III) and As(V) from aqueous solution, with an emphasis on the effect of Fe0 loading of adsorbent on arsenic remediation. Iron loading has a significant role in adsorption of As(III) and As(V) on F-nZVI, with increase in adsorption with optimum iron loading of 20% (w/w) on fuller’s earth (F-nZVI-4). However, increase in loading above 20%, resulted in no significant increase in As(III) and As(V) adsorption. The adsorption results fitted well with Langmuir and Freundlich isotherm models and the maximum adsorption capacity of F-nZVI-4 for As(III) and As(V) were observed to be 50.08 and 91.42mg/g, respectively. The adsorption isotherm and kinetic studies indicate a rapid removal of As(III) and As(V) from the aqueous solution in the presence of F-nZVI 1-8, with an substantially high rate of removal for arsenic with F-nZVI-4.

Nanoscale zero-valent iron particles for the remediation of plutonium and uranium contaminated solutions

In the current work the uptake of plutonium onto nanoscale zero-valent iron nanoparticles (nZVI) under anoxic conditions has been investigated. A uranyl solution was also studied under similar geochemical conditions to provide a comparative dataset. Following nZVI addition, a rapid and significant decrease in aqueous actinide concentration was recorded for both systems. The removal rate recorded for plutonium was slower, with 77% removal recorded after 1 h of reaction, compared to 99% recorded for uranium. Low aqueous contaminant concentrations (<25%) were then recorded for both systems until the end of the 7 day reaction period. XPS confirmed contaminant uptake onto the nZVI. For the plutonium system, the recorded photoelectron spectra exhibited Pu 4f lines centred at ∼439 and ∼427 eV, characteristic of Pu4+ and implying that chemical reduction of the sorbed plutonium had occurred, ascribed to the formation of PuO2. Similarly, with the U-system, the recorded U 4f photoelectron peaks were centred at energies of ∼380 and ∼391 eV, characteristic of U4+ in UO2. Results provide clear evidence that nZVI may be used as an effective material for the removal of plutonium from contaminated waters.

Removal of trichloroethylene DNAPL trapped in porous media using nanoscale zerovalent iron and bimetallic nanoparticles: Direct observation and quantification

Direct trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) removal inside pore areas using nanoscale zerovalent iron (NZVI) and bimetallic nanoparticles were first investigated in a water-saturated porous glass micromodel. Effects of nitrate, aqueous ethanol co-solvent, humic substance, and elapsed time on TCE DNAPL removal using NZVI were studied by direct visualization. The removal efficiency was then quantified by directly measuring the remaining TCE DNAPL blobs area using an image analyzer. As ethanol content of co-solvent increased, TCE DNAPL removal by NZVI was also increased implying sequential TCE DNAPL removal mechanisms: as dissolved TCE was degraded by NZVI, TCE dissolution from TCE blobs would be then facilitated and the TCE blob areas would be eventually reduced. The presence of nitrate and humic substance hindered the NZVI reactivity for the TCE DNAPL removal. In contrast, the TCE DNAPL removal efficiency was enhanced using bimetallic nanoparticles in a short-term reaction by generating atomic hydrogen for catalytic hydro-dechlorination. However, all TCE DNAPL removal efficiencies reached the same level after long-term reaction using both NZVI and bimetallic nanoparticles. Direct TCE DNAPL observation clearly implied that TCE blobs existed for long time even though all TCE blobs were fully exposed to NZVI and bimetallic nanoparticles.