Iron-based Nanoparticles Research Articles

Comparison of degradation mechanisms of microcystin-LR using nanoscale zero-valent iron (nZVI) and bimetallic Fe/Ni and Fe/Pd nanoparticles

Microcystin-LR (MC-LR) as a drinking water contaminant was degraded using iron-based nanoparticles such as nZVI, Fe/Ni and Fe/Pd. Batch experiments showed that 28.0% of MC-LR with the initial concentration of 5mgL−1 was removed using nZVI, while more than 90% of MC-LR was removed using either bimetallic Fe/Ni or Fe/Pd after degrading for 120min. In addition, the results indicated that Fe0 was oxided to iron oxide or hydroxide after reacting with MC-LR, while Ni or Pd acted as the catalysis to prevent Fe0 corrosion and generating hydrogen via water reduction. Degradation of MC-LR by iron-based nanoparticles fitted well to the pseudo-first order kinetic model and the degradation was a diffusion-controlled reaction with low activation energies (8–21kJmol−1). Finally, the degradation mechanisms of MC-LR using iron-based nanoparticles were proposed according to the LC–MS analysis. In nZVI case, when the MC-LR was quickly adsorbed on nanoparticles, electron transfer and H2 generated from iron corrosion were generated and broke down the Adda composition of MC-LR. Based on corrosion in the Fe0–H2O system, bimetallic Fe/Ni and Fe/Pd further utilized the abundant hydrogen radical decomposed from H2 under the catalysis of Ni or Pd, and destroyed the Adda to form small molecules.

Reductive reactivity of borohydride- and dithionite-synthesized iron-based nanoparticles: A comparative study

In this study sodium dithionite (NaS2O4) and sodium borohydride (NaBH4) were employed as reducing agents for the synthesis of nanosized iron-based particles. The particles formed using NaBH4 (denoted nFe(BH4)) principally contained (as expected) Fe(0) according to XAS and XRD analyses while the particles synthesized using NaS2O4, (denoted nFe(S2O4)) were dominated by the mixed Fe(II)/Fe(III) mineral magnetite (Fe3O4) though with possible presence of Fe(0). The ability of both particles to reduce trichloroethylene (TCE) under analogous conditions demonstrated remarkable differences with nFe(BH4) resulting in complete reduction of 1.5mM of TCE in 2h while nFe(S2O4) were unable to effect complete reduction of TCE in 120h. Moreover, acetylene was the major reaction product formed in the presence of nFe(S2O4) while the major reaction product formed following reaction with nFe(BH4) was ethylene, which was further reduced to ethane as the reaction proceeded. Considering that effective Pd reduction to Pd(0) requires the presence of Fe(0), this is consistent with our finding that Fe(0) is not the dominant phase formed when employing dithionite as a reducing agent under the conditions employed in this study.

Heterogeneous Fenton-like oxidation of malachite green by iron-based nanoparticles synthesized by tea extract as a catalyst

Abstract The green synthesis of functional iron nanoparticles (Fe NPs) by tea extracts was used as a catalyst for the Fenton-like oxidation of malachite green (MG), where more than 85% of MG was removed. The new findings are that the removal of MG by Fe NPs was based on the adsorption of MG onto iron oxide and degradation of MG by iron nanoparticles. This was confirmed by adsorption and degradation kinetics, indicating that: firstly, the adsorption kinetics follows the pseudo-first-order model; and secondly, degradation kinetics fitted well to the pseudo-second-order model. Morphology, size and changes in the Fe NPs surface were characterized using SEM, XRD, and FTIR techniques, showing that Fe 2 O 3 and Fe 3 O 4 was formed and green tea extract contained a high concentration of caffeine/polyphenols. It acted as both reducing and capping agents in the synthesis of Fe NPs. To further confirm the removal mechanism of MG by the functional Fe NPs, the degraded products were identified by FTIR and GC–MS analysis. Finally the mechanism of Fenton-like oxidation of MG based on both adsorption and degradation was proposed.

Cobalt- and iron-based nanoparticles hosted in SBA-15 mesoporous silica and activated carbon from biomass: Effect of modification procedure

Ordered mesoporous silica of SBA-15 type and activated carbon, prepared from waste biomass (peach stones), are used as host matrix of nanosized iron and cobalt particles. The effect of preparation procedure on the state of loaded nanoparticles is in the focus of investigation. The obtained materials are characterized by Boehm method, low temperature physisorption of nitrogen, XRD, UV–Vis, FTIR, Mossbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic behaviour of the samples is tested in methanol decomposition. The dispersion, oxidative state and catalytic behaviour of loaded cobalt and iron nanoparticles are successfully tuned both by the nature of porous support and the metal precursor used during the samples preparation. Facile effect of active phase deposition from aqueous solution of nitrate precursors is assumed for activated carbon support. For the silica based materials the catalytic activity could be significantly improved when cobalt acetylacetonate is used during the modification. The complex effect of pore topology and surface functionality of different supports on the active phase formation is discussed.

Magnetic resonance imaging reveals detailed spatial and temporal distribution of iron-based nanoparticles transported through water-saturated porous media

The application of engineered nanoparticles (ENP) such as iron-based ENP in environmental systems or in the human body inevitably raises the question of their mobility. This also includes aspects of product optimization and assessment of their environmental fate. Therefore, the key aim was to investigate the mobility of iron-based ENP in water-saturated porous media. Laboratory-scale transport experiments were conducted using columns packed with quartz sand as model solid phase. Different superparamagnetic iron oxide nanoparticles (SPION) were selected to study the influence of primary particle size (dP=20nm and 80nm) and surface functionalization (plain, –COOH and –NH2 groups) on particle mobility. In particular, the influence of natural organic matter (NOM) on the transport and retention behaviour of SPION was investigated. In our approach, a combination of conventional breakthrough curve (BTC) analysis and magnetic resonance imaging (MRI) to non-invasively and non-destructively visualize the SPION inside the column was applied. Particle surface properties (surface functionalization and resulting zeta potential) had a major influence while their primary particle size turned out to be less relevant. In particular, the mobility of SPION was significantly increased in the presence of NOM due to the sorption of NOM onto the particle surface resulting in a more negative zeta potential. MRI provided detailed spatially resolved information complementary to the quantitative BTC results. The approach can be transferred to other porous systems and contributes to a better understanding of particle transport in environmental porous media and porous media in technical applications.

A field application of nanoparticle-based invert emulsion drilling fluids

Application of nanotechnology in drilling fluids for the oil and gas industry has been a focus of several recent studies. A process for the in situ synthesis of nanoparticles (NPs) into drilling fluids has been developed previously in our group and showed that calcium-based NPs (CNPs) and iron-based NPs (INPs), respectively, with concentrations of 0.5–2.0 wt% can dramatically improve filtration properties of commercial drilling fluids in a laboratory environment. In this work, a modified process for the emulsion-based synthesis of NPs on a 20 m3 volume and its subsequent full-scale field testing are presented. Comparison between NP carrier fluids prepared under controlled environment in the laboratory and those prepared on a large scale in a mixing facility revealed very little variation in the main characteristics of the drilling fluid; including the size of the solid constituents. Transmission electron microscopy photographs suggest an average CNP particle size in the carrier fluid of 51 ± 11 nm. Results from the full-scale field test showed that total mud losses while drilling with CNP-based invert emulsion were on average 27 % lower than in the case of conventional fluids. This loss prevention falls within the range observed in the laboratory.

Reductive decolorization of acid blue 113 azo dye by nanoscale zero-valent iron and iron-based bimetallic particles

In this study, effectively reductive decolorization of wastewater with synthesized C.I. Acid Blue 113 (AB113) was obtained by nanoscale particles of zero-valent iron (NZVI), bimetallic iron/nickel (nFe/Ni) and iron/zinc (nFe/Zn) which were prepared in the laboratory with large surface area and reductive potential. The particle size was identified less than 100nm by field emission scanning electron microscope (FESEM) that nickel was homogeneously distributed with iron element by FESEM mapping for nFe/Ni sample. Moreover, the surface areas of bimetallic nanoparticle samples such as nFe/Ni and nFe/Zn were significantly increased than that of NZVI. The effects of experimental variables such as nanoparticle dosage, initial dye concentration, and metal composition on AB113 decolorizing were investigated. From the results, the synthesized AB113 wastewater of high color and total organic carbon (TOC) was successfully reductive decolorized using three iron-based nanoparticle samples. The optimal conditions were obtained the best color removal efficiencies in 30 min while an initial dye concentration of 100 mg l−1 and nFe/Ni dosage of 0.2g l−1. Besides, a modified pseudo-first-order kinetic equation was developed to describe the color removal efficiency affected by both initial dye concentration and nanoparticle dosage. The higher nanoparticle dosage, the higher color and TOC removal efficiencies were obtained within the nanoparticle dosage of 0.2g l−1. Furthermore, among three iron-based nanoparticle samples, nFe/Ni preformed the best color and TOC removal as well as durability.

Immobilization of Chromium in Tannery Sludge Using Iron-Based Nanoparticles and Nanobiocomposites

This paper presents the efficacy of zero-valent iron nanoparticles (ZVINs), magnetic iron oxide nanoparticles (MINs), zero-valent iron nanoparticles/sugarcane bagasse (ZVIN-SB) composite and magnetic iron oxide nanoparticles/sugarcane bagasse (MIN-SB) composite in immobilizing chromium present in tannery sludge. The optimized values for the immobilization of chromium by the adsorbents were found to be 48 h, 100 g/kg and 7, respectively, for time, adsorbent dosage and pH. The maximum uptake capacity was found to be 429.75, 539.25, 587.25 and 625.8 mg/kg, respectively, for ZVIN, MIN, ZVIN-SB and MIN-SB. The desorption study of the unamended sludge and sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB was carried out with three different desorbing media (0.1 N HCL, DIW and 0.1 N NaOH). It was found that the cumulative concentration of leachate chromium was more in basic condition than in neutral and acidic conditions. In column studies, the concentration of leachate chromium attained 0 mg/L at 24, 15, 18 and 14 pore volumes, respectively, for the sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB. The experimental adsorption data fitted well with pseudo-first-order kinetics. The zero-order kinetics accurately predicted the experimental desorption capacity (q e) of the sludge amended by ZVIN, MIN, ZVIN-SB and MIN-SB. The Fourier transform infrared spectroscopy (FTIR) analysis showed that the amine, carboxyl, iron compounds, etc. present in the adsorbents were the chief causes for the immobilization of chromium. The X-ray diffraction (XRD) analysis of the sludge showed the presence of trivalent chromium compounds at a higher concentration.

The mechanism for degrading Orange II based on adsorption and reduction by ion-based nanoparticles synthesized by grape leaf extract

Biomolecules taken from plant extracts have often been used in the single-step synthesis of iron-based nanoparticles (Fe NPs) due to their low cost, environmental safety and sustainable properties. However, the composition of Fe NPs and the degradation mechanism of organic contaminants by them are limited because these are linked to the reactivity of Fe NPs. In this study, Fe NPs synthesized by grape leaf extract served to remove Orange II. Batch experiments showed that more than 92% of Orange II was removed by Fe NPs at high temperature based on adsorption and reduction and confirmed by kinetic studies. To understand the role of Fe NPs in the removal process of azo dye, surface analysis via X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were employed, showing that the Fe NPs were composed of biomolecules, hydrous iron oxides and Fe0, thus providing evidence for the adsorption of Orange II onto hydrous iron oxides and its reduction by Fe0. Degraded products such as 2-naphthol were identified using LC–MS analysis. A degradation mechanism based on asymmetrical azo bond cleavage for the removal of Orange II was proposed.

Synthesis of Ni/Fe Nanoparticles Utilizing PVP–SDS Bound Micelles as a Template to Remove PCB77

In the present study, Ni / Fe nanoparticles were synthesized using bound micelles as a template and 3, 3′, 4, 4′-tetrachlorobiphenyl (PCB77) as the target contaminant. The dual bound micelles, which are composed of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS), were found to be superior to single-component templates for the dispersion of metallic ions and thus directed the synthesis of Ni / Fe nanoparticles with improved properties. After characterization of the different nanoparticles, it was found that the sustained effectiveness of PVP–SDS bound micelles afforded specialized structures with two gradations of Ni / Fe nanoparticles, correlating to more active sites and higher activity. The improved activity of the Ni / Fe nanoparticles was finally exhibited by the higher ratio (99.3% in 72 h) and efficiency (k obs of 0.0674 h-1) of PCB77 removal. Herein, the utilization of PVP–SDS bound micelles is proposed as a template for the improvement of iron-based nanoparticles and correlated research.

Effects of cyclodextrin on the morphology and reactivity of iron-based nanoparticles using Eucalyptus leaf extract

Plant extract is used as an eco-friendly alternative to chemical and physical methods for the synthesis of nanoparticles. Improving both the dispersion and reactivity of nanoparticles using plant extract still remains a challenge. We demonstrate a green method for stabilizing the plant-mediated synthesized iron-based nanoparticles (Fe NPs) using β-cyclodextrin (βCD). The synthesized Fe NPs exhibited a highly efficient removal of azo-dye from aqueous solution (up to 215.1mgg−1 for Direct black G). The effect of βCD on the morphology and reactivity of Fe NPs was confirmed by various techniques, which indicated that adding βCD caused particle size to decrease from 60 to 20nm with a narrower size distribution. It also led to changes in the surface capping of Fe NPs. We concluded that βCD not only capped the Fe NPs with a hydrophobic property, but also enhanced the water solubility of the lipophilic biomolecules due to their host-guest interaction. This process provides new insights into biocompatible cyclodextrin controlling morphology and reactivity in the green synthesis of Fe NPs.

Large-Diameter Single-Wall Carbon Nanotubes Formed Alongside Small-Diameter Double-Walled Carbon Nanotubes

Samples containing a majority of either single-wall carbon nanotubes (SWCNTs) or double-walled carbon nanotubes (DWCNTs) are prepared in the same catalytic chemical vapor deposition conditions but using slightly different catalytic materials, based on alumina impregnated with iron and molybdenum salts. There is a sharp SWCNTs-to-DWCNTs transition. By contrast to the usual findings, the selectivity is not correlated to the size of the iron-based catalyst nanoparticles, nor does the transition occur upon a decreasing carbon/catalyst ratio. The result is attributed to the increasing MoO3 concentration inducing modifications of the gas atmosphere, such as the formation of more reactive C2 species through C2H4 dissociation, which thus favors the nucleation and growth of a DWCNT. In the DWCNT sample, the average diameter of the SWCNTs is higher than the average outer diameter of the DWCNTs, which is uncommon, as many authors stress that SWCNTs show a lower diameter than DWCNTs. The study could provide guidelines for the synthesis of very small diameter DWCNTs.

Mesoscale assemblies of iron oxide nanocubes as heat mediators and image contrast agents.

Iron oxide nanocubes (IONCs) represent one of the most promising iron-based nanoparticles for both magnetic resonance image (MRI) and magnetically mediated hyperthermia (MMH). Here, we have set a protocol to control the aggregation of magnetically interacting IONCs within a polymeric matrix in a so-called magnetic nanobead (MNB) having mesoscale size (200 nm). By the comparison with individual coated nanocubes, we elucidate the effect of the aggregation on the specific adsorption rates (SAR) and on the T1 and T2 relaxation times. We found that while SAR values decrease as IONCs are aggregated into MNBs but still keeping significant SAR values (200 W/g at 300 kHz), relaxation times show very interesting properties with outstanding values of r2/r1 ratio for the MNBs with respect to single IONCs.

Reactivity of iron-based nanoparticles by green synthesis under various atmospheres and their removal mechanism of methylene blue

The reduction degradation pathway of MB molecules.

The Study of Iron-based Nanoparticles Stability in Biological Fluids by Stripping Voltammetry

The possibility of application of voltammetric methods for evaluating the stability of nanoparticles in biological fluids has been shown for the first time. The kinetics of degradation both of uncoated nanoparticles and with different coatings in a simulated solution of gastric juice in a wide range of time has been studied. It has been shown that by using carbonaceous coatings nanoparticles resistance increases 2-4 times, and when modifying the surface with aryldiazonium salts - 5-6 times.

Heterogeneous Fenton oxidation of 2,4-dichlorophenol using iron-based nanoparticles and persulfate system

Nanoscale zero-valent iron (nZVI) has received attention for its potential applications in contaminated site remediation due to its reactivity. However, it is still unclear how nZVI acts as a catalyst to generate sulfate radicals in heterogeneous Fenton oxidation of 2,4-dichlorophenol (DCP). In this paper, various Fe materials such as Fe2+, nano-ZVI, and nano-Fe3O4 (nFe3O4) were used as heterogeneous catalysts, where the removals of DCP by Fe2+, nZVI, and nFe3O4 were 11.9%, 9.0%, and 5.5%, while the degradation of DCP in the presence of persulfate increased to 34.4%, 37.8%, and 5.8%, respectively. These data indicate nZVI can potentially generate sulfate radicals. UV, SEM, EDS and XRD demonstrated that changes on the surface of nZVI occurred owing to the Fe2+ leaching. It was further observed that DCP degradation increased when the dosage of nZVI and persulfate concentration also increased. However, it decreased when the initial pH and DCP concentration increased. More than 98% of DCP degradation was achieved within 180min under optimum conditions, but less than 40% of chemical oxygen demand (COD) was removed. The degradation of DCP follows the pseudo-first-order kinetics and it is a chemical control reaction with an activation energy of 91.5kJmol−1. Finally, a possible mechanism of DCP degradation using the nZVI/PS system was proposed.

Fenton-like oxidation of 2,4-DCP in aqueous solution using iron-based nanoparticles as the heterogeneous catalyst

In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe2+ was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe2+ leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed.

Fe3+ ions anchored to Fe@O-MWCNTs as double impact T2 MRI contrast agents

Fe3+ ions were anchored via complexation onto the oxidized multiwall carbon nanotubes containing encapsulated iron-based nanoparticles (Fe@O-MWCNTs) yielding hybrids Fe(III)/Fe@O-MWCNTs for application as MRI contrast agents. After washing, no free Fe3+ ions were observed in the solution. A 120 mg Fe3+ was coordinated by each 1 gram of Fe@O-MWCNTs with a formation of stable hybrids. Relaxation times T1 and T2 of water protons were measured for the suspensions of hybrids. At 7.1 T relaxivity, r2 of Fe@O-MWCNT and Fe(III)/Fe@O-MWCNT was 25 and 35 s–1ml mg–1, respectively, whereas at 0.4 T r2-values were equal. Additionally, T1/T2 ratio was found in a range of 17–104, which is a promising value in the light of application of the proposed materials as potential T2 MRI contrast agents.

Iron-based nano-particles for Lipolase immobilization and stabilization

Iron-based nano-particles for Lipolase immobilization and stabilization

Oxidizing capacity of periodate activated with iron-based bimetallic nanoparticles.

Nanosized zerovalent iron (nFe0) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO4-) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO4- to iodate (IO3-). nFe0 without bimetallic loading led to similar IO4- reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO4- is activated by bimetallic nFe0 (e.g., nFe0-Ni and nFe0-Cu). The organic degradation kinetics in the nFe0-Ni(or Cu)/IO4- system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective nature of oxidant in the nFe0-Ni(or Cu)/IO4- system. The comparison with the photoactivated IO4- system, in which iodyl radical (IO3•) is a predominant oxidant in the presence of methanol, suggests IO3• also as primary oxidant in the nFe0-Ni(or Cu)/IO4- system.