Fe0 Particles Research Articles

Reductive sequestration of chromate by hierarchical FeS@Fe0 particles

Nanoscale Fe0 (nFe0) can detoxify Cr(VI)-bearing wastewater and groundwater, but rapid passivation is a negative factor for large-scale remediation applications. In this study, a magnetic FeS@Fe0 hybrid material was fabricated by immobilization of iron sulfide (FeS) onto Fe0 particles to improve the Cr(VI) removal capacity. The solid characterization confirmed that Fe0 particles were encapsulated by amorphous iron monosulfide. The Cr(VI) uptake by FeS@Fe0 hybrid particles was found to follow pseudo-second-order rate kinetics, and the Langmuir isotherm was most appropriate to describe Cr(VI) sorption. Meanwhile, the FeS@Fe0 hybrid particles showed a much higher efficiency towards Cr(VI) sequestration compared to individual nFe0. Moreover, the results of batch experiments with various adsorbent doses indicated that the reactivity of FeS@Fe0 varies with different FeS-to-Fe0 molar ratios. The reaction rate constants for Cr(VI) removal first increased with an increasing FeS-to-Fe0 ratio from 0/1 to 1/9, and then decreased for the FeS-to-Fe0 ratio increased further 1/5 or 1/3. For environmental parameters, there was a negative effect of increasing the solution pH and dissolved oxygen on Cr(VI) removal. Furthermore, a mechanistic analysis revealed that Cr(VI) reduction occurred predominantly at the solid-liquid interface, and that Fe(II) regenerated from FeS@Fe0 corrosion may account for 52% of the Cr(VI) reduction, while electrons from Fe0 and FeS account for the rest. After treatment, Cr(VI) was completely transformed and immobilized as solid Fe-Cr hydroxide precipitates, thus avoiding secondary contamination. The FeS@Fe0 hybrid material has a better potential for treating Cr(VI)-bearing wastewater than nano Fe0.

Use of iron and bio-oil wastes to produce highly dispersed Fe/C composites for the photo-Fenton reaction.

This work describes the synthesis, characterization, and application of an active heterogeneous photo-Fenton system obtained from two different wastes, i.e., laterite (an iron mining waste) and the acid aqueous fraction (AAF) from bio-oil production. AAF with high acidity (ca. 3molH+ L-1) and organic concentration (25wt.%) obtained from biomass flash pyrolysis was used for the efficient extraction of Fe3+ from laterite waste. After extraction, the mixture Fe3+/AAF was dried and treated at different temperatures, i.e., 500, 650, and 800°C, to obtain Fe/C reactive composites. Mössbauer, XRD, TG, elemental analyses, and SEM/EDS showed the presence of highly disperse Fe oxide nanoparticles at 500 and 650°C and Fe0 particles in the material obtained at 800°C with carbon contents varying from 74 to 80%. The three composites were tested as heterogeneous catalysts in the photo-Fenton reaction for the oxidation of the model dye contaminant methylene blue, showing high activities at neutral pH.

Particles and enzymes: Combining nanoscale zero valent iron and organochlorine respiring bacteria for the detoxification of chloroethane mixtures

Nanoscale zero valent iron (nZVI) and organochlorine respiring bacteria (ORB) are two technologies used to detoxify chlorinated aliphatic hydrocarbons (CAHs). nZVI can rapidly detoxify high CAH concentrations, but is quickly oxidised and unable to degrade certain CAHs (e.g., 1,2-dichlorothane). In contrast, ORB can dechlorinate CAHs resistant to nZVI (e.g., 1,2-dichlorothane) but are inhibited by other CAHs of concern degradable by nZVI (e.g., chloroform and carbon tetrachloride). Combining the two was proposed as a unique treatment train to overcome each technology's shortcomings. In this study, this combined remedy was investigated using a mixture of 1,2-dichloroethane, degradable by ORB but not nZVI, and 1,1,2-trichloroethane, susceptible to both. Results indicated that nZVI rapidly dechlorinated 1,1,2-trichloroethane when supplied above 0.5g/L, however ORB were inhibited and unable to dechlorinate 1,2-dichloroethane. pH increase and ionic species associated with nZVI did not significantly impact ORB, pinpointing Fe0 particles as responsible for ORB inhibition. Below 0.05g/L nZVI, ORB activity was stimulated. Results suggest that combining ORB and nZVI at appropriate doses can potentially treat a wider range of CAHs than each individual remedy. At field sites where nZVI was applied, it is likely that in situ nZVI concentrations were below the threshold of negative consequences.

Core/Shell Iron/Oxide Nanoparticles for Improving the Magneto‐Dielectric Properties of Polymer Composites

A simple method to obtain high magnetic permeability (μr), high dielectric permittivity (ϵr), and low loss polymer composites with core/shell iron/metal oxide particles is developed. Magnetic iron (Fe0) particles with protective SiO2 shells are synthesized in aqueous environment at room temperature. The shells provide electrical insulting layers which decrease energy loss and also prevent the possibility of μr decrease due to Fe0 oxidation. Furthermore, Fe0 particles could also be coated with TiO2 shells which allow ϵr to be tuned. The ϵr and μr of the resulting polydimethylsiloxane composites are optimized for core‐shell particle doping. The value of ϵr is up to 9.8 and most importantly, the μ is close to 2 at 1 GHz with 43 wt% doping of core‐shell particles. The dielectric loss of the composites is less than 0.02.

Mg(OH)2 Supported Nanoscale Zero Valent Iron Enhancing the Removal of Pb(II) from Aqueous Solution.

In this article, a novel composite (Mg(OH)2 supported nanoscale zerovalent iron (denoted as nZVI@Mg(OH)2) was prepared and characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy method. The morphology analysis revealed that Mg(OH)2 appeared as self-supported flower-like spheres, and nano Fe0 particles were uniformly immobilized on the surface of their "flower petals", thus aggregation of Fe0 particles was minimized. Then the Pb(II) removal performance was tested by batch experiments. The composite presented exceptional removal capacity (1986.6 mg/g) compared with Mg(OH)2 and nanoscale zerovalent iron due to the synergistic effect. Mechanisms were also explored by a comparative study of the phase, morphology, and surface valence state of composite before and after reaction, indicating that at least three paths are involved in the synergistic removal process: (1) Pb(II) adsorption by Mg(OH)2 (companied with ion exchange reaction); (2) Pb(II) reduction to Pb0 by nanoscale zerovalent iron; and (3) Pb(II) precipitation as Pb(OH)2. The hydroxies provided by Mg(OH)2 can dramatically promote the role of nanoscale zerovalent iron as reducer, thus greatly enhancing the whole Pb(II) sequestration process. The excellent performance shown in our research potentially provides an alternative technique for Pb(II) pollution treatment.

Adsorption and degradation of 2,4-dichlorophenoxyacetic acid in spiked soil with Fe0 nanoparticles supported by biochar

This work studies the adsorption and degradation of 2,4-dichlorophenoxyacetic (2,4-D) in spiked soil with nanoscale Fe0 particles (nFe0) and biochar derived from maize straw. When biochar concentration was high, the adsorption capacity of soil was enhanced. Furthermore, 2,4-D degraded completely at loading rates of 0.33 and 0.17 g/L nFe0 plus biochar (initial 2,4-D concentration of 10 mg/g) within 40 h, according to equilibrium data. Additionally, the theoretical concentration of chloridion was approximately 84%. Further analysis indicated that the effect of nFe0 on 2,4-D degradation was weaker in soil columns than that in soil slurry. By contrast, 2,4-D degradation is positively influenced by biochar application, which prevented the aggregation and corrosion of Fe nanoparticles. Although the enhanced capacity for 2,4-D adsorption on the soil decelerated dechlorination rate, long-term nFe0 activity was generated. After 72 h, the efficiency of 2,4-D degradation was approximately 53.2% in the soil columns with biochar support.

Selective Oxidation of Amorphous Carbon by CO2to Produce Fe@C Nanoparticles from Bulky Fe/C Matrices

In this work, a bulky Fe0/carbon matrix obtained by a low cost and simple reduction/carbonization of Fe3+ salt with sucrose was treated with CO2 to selectively oxidize the amorphous carbon to release the graphite like carbon coated magnetic Fe0 particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, X-ray diffraction (XRD), BET, thermogravimetric analysis (TG) (in CO2) and particle size analyses showed that the treatment with CO2 of the Fe/carbon bulky composite led to the selective oxidation of the more amorphous carbon with the formation of 125-132 nm Fe@C nanoparticles with surface areas of 217 m2 g−1.

Discussing porosity loss of Fe0 packed water filters at ground level

The use of granular metallic iron (Fe0) as filter material is gaining acceptance in the field of water treatment. Few works have been directed at developing design guidance for efficient Fe0 filters. This note consolidates earlier works and provides the scientific basis for the design and evaluation of Fe0 filters for water treatment at any scale. The approach assumes uniform corrosion of individual Fe0 particles and utilizes the radius loss (X=R0−R) to asses the extent of porosity loss in the whole system. Results corroborate that, for R0⩽1.0mm, sustainable filters must content less than 53% Fe0 (v/v). A universal equation of Fe0 filters is provided given X as a function of the initial radius R0, the initial volume of Fe0, the initial porosity of the filter and the coefficient of volumetric expansion (O2 availability). This equation should be routinely incorporated in simulations for modeling the hydraulic conductivity of Fe0 filters. The model improves the discussion of published data on porosity loss.

Nitrate reduction by chelating resin‐supported Fe and Fe/Ni nanoparticles: comparison of reactivity and effect of co‐existing inorganic anion

AbstractBACKGROUNDNitrate is a potential harmful contaminant to humans, and widely detected in ground and surface water. The aim of this study was to accelerate nitrate reduction using chelating resin‐supported Fe/Ni nanoparticles.RESULTSThe results of X‐ray diffraction indicated that the presence of Ni can prevent the oxidation of nanoscale Fe0 particles by O2. The nitrate removal efficiency (98.3%) and the rate constant (Kobs = 0.0166 mg−1 L min−1) using supported Fe/Ni nanoparticles were increased greatly compared with those using supported Fe nanoparticles (21.3% and 7.93 × 10−4 mg−1 L min−1, respectively). The co‐existing Cl− caused a slight increase in nitrate reduction by the supported Fe nanoparticles, but SO42−, PO43−, HCO3− and humic acid caused obvious inhibition of NO3− removal. Due to Ni catalysis, however, the effects of these co‐existing anions and humic acid on nitrate reduction by supported Fe/Ni nanoparticles could be ignored, except HCO3−. Moreover, the Fe/Ni nanoparticles showed good performance for nitrate reduction in drinking water.CONCLUSIONThe supported Fe/Ni nanoparticles were more reactive than Fe nanoparticles. The co‐existing anions and humic acid showed less effect on nitrate reduction. The supported Fe/Ni nanoparticles have a potential application for nitrate reduction. © 2014 Society of Chemical Industry

Adsorption Mechanism of Humic Acid on Cu/Fe Bimetallic Particles and Its Influence on the Reduction of Nitrobenzene in Groundwater

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe0 particles, the adsorption on Cu/Fe is faster than that on Fe0. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe0, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe0. The adsorption enthalpy on Cu/Fe is lower than that on Fe0, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe2O3) and magnetite (Fe3O4) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe0, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe0, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.

Influence of Preparation Conditions on Characteristics, Reactivity, and Operational Life of Microsized Fe/Cu Bimetallic Particles

The effect of the preparation conditions on the physicochemical characteristics, operating life, and reactivity of Fe/Cu bimetallic particles was studied significantly by using a model pollutant (p-nitrophenol), scanning electron microscopy–energy dispersive spectrometry, and X-ray diffraction spectrometry. The results suggest that the higher reactivity and longer operating life of Fe/Cu bimetallic particles were obtained under the optimal preparation conditions. Furthermore, under the optimal preparation conditions, Cu was not easily dropped from the Fe0 particle, and the weight ratio of Cu on the surface of the Fe/Cu bimetallic particles increased significantly. Moreover, their optimal theoretical Cu mass loading could be decreased from 0.89 to 0.41 g Cu/g Fe, which favors the reduction of production costs. In addition, two batch experiments with Fe/Cu bimetallic particles prepared under optimal and nonoptimal conditions were set up to comparatively investigate the improvement of operating life and reactivity of Fe/Cu particles when optimized preparation conditions were carried out. As a result, it was proven that the reactivity and operating life of Fe/Cu bimetallic particles could be improved significantly through the optimization of preparation conditions.

Application of zerovalent iron impregnated chitosan-caboxymethyl-β-cyclodextrin composite beads as arsenic sorbent

Nano zerovalent iron impregnated chitosan-carboxymethyl β-cyclodextrin complex has been successfully tested for arsenic removal. Addition of chitosan enhances the stability of Fe0 particles and the carboxymethyl β-cyclodextrin gives the composite more active sites to interact with the target ions. Removal of arsenic(III) and arsenic(V) was studied through batch adsorption at pH 6.0 under equilibrium and dynamic conditions. Prepared beads were characterized by FT-IR, SEM, BET and XPS. The rate of reduction can be expressed by pseudo-second-order reaction kinetics plus the equilibrium data were well fitted to Langmuir adsorption models. Equilibrium is achieved after 3h and As(III) and As(V) were reduced to <20μg/L which accounts 99% of the total removal below the Bangladesh standard (50μg/L). The adsorption capacity was calculated from Langmuir model and found to be 18.51mg/g and 13.51mg/g for As(III) and As(V), respectively. The adsorbent can be separated magnetically and thus reused successfully for the removal of total inorganic arsenic from water. So, this adsorbent can be a potential material for the remediation of contaminated surface and ground water.

Treatment of a Trichloroethylene Source Zone using Persulfate Activated by an Emplaced Nano-Pd–Fe0 Zone

Recently, metal nanoparticles have attracted attention as promising peroxygen activators for the rapid and effective remediation of organic contaminants. In this work, a one-dimensional physical model experiment was designed to investigate the mobility of the metal nanoparticles in porous media and the potential use of metal nanoparticles as peroxygen activators for in situ treatment of source zones. We found that our synthesized nano-Pd–Fe0 particles were mobile in a non-geological porous medium and relatively immobile in a geological porous medium. In addition, we observed that iron-based bimetallic nanoparticles were able to remain in suspension in an ideal aqueous system much longer (>6 weeks) than iron-based monometallic nanoparticles (<1 h). To overcome the nano-Pd–Fe0 particle delivery issue in geological porous media, an activation zone approach was adopted. Nano-Pd–Fe0 particles were injected in order to create a zone to activate persulfate for the treatment of a trichloroethylene source zone. Trichloroethylene mass destruction was only 9 % higher in the nano-Pd–Fe0 activated persulfate system compared to the non-activated persulfate system as revealed by a short-duration chloride concentration spike in the effluent. In addition, the nano-Pd–Fe0 activation zone was rapidly deactivated after being exposed to persulfate as visually observed by a color change, indicating that the longevity of the activation zone is limited.

Inhibition of sulfate reducing bacteria in aquifer sediment by iron nanoparticles

Batch microcosms were setup to determine the impact of different sized zero valent iron (Fe0) particles on microbial sulfate reduction during the in situ bio-precipitation of metals. The microcosms were constructed with aquifer sediment and groundwater from a low pH (3.1), heavy-metal contaminated aquifer. Nano (nFe0), micro (mFe0) and granular (gFe0) sized Fe0 particles were added to separate microcosms. Additionally, selected microcosms were also amended with glycerol as a C-source for sulfate-reducing bacteria. In addition to metal removal, Fe0 in microcosms also raised the pH from 3.1 to 6.5, and decreased the oxidation redox potential from initial values of 249 to −226 mV, providing more favorable conditions for microbial sulfate reduction. mFe0 and gFe0 in combination with glycerol were found to enhance microbial sulfate reduction. However, no sulfate reduction occurred in the controls without Fe0 or in the microcosm amended with nFe0. A separate dose test confirmed the inhibition for sulfate reduction in presence of nFe0. Hydrogen produced by Fe0 was not capable of supporting microbial sulfate reduction as a lone electron donor in this study. Microbial analysis revealed that the addition of Fe0 and glycerol shifted the microbial community towards Desulfosporosinus sp. from a population initially dominated by low pH and metal-resisting Acidithiobacillus ferrooxidans.

Progress of Removing Heavy Metals by Zero Valent Iron Nanoparticles from Wastewater

Heavy metal pollution is a serious threat to human health. Because of the development of nanotechnology, removal of heavy metal is more convenient and effective. nanozero valent iron (Fe0) particles have high activity and specific surface area. At present, Fe0 nanoparticles have been used in the processing of refractory organics, heavy metals, inorganic salts, soil restoration, and other areas of the environment. But the dispersion and stability of the Fe0 nanoparticles are poor. We can improve physical and chemical properties of Fe0 by adding carrier materials to make iron nanoparticles have better stability, dispersion and the treatment effect. This paper mainly introduced the situation of removing heavy metals by the Fe0 nanoparticles and hybridized Fe0 particles. Hybridized Fe0 has good performance and high removal efficiency to heavy metals. We also discussed what are inadequate and need to be further researched.

Preparation of nanoscale zero-valent iron supported on chelating resin with nitrogen donor atoms for simultaneous reduction of Pb2+ and [formula omitted

Polymeric ion exchanger has been proven to be an excellent carrier for metal nanoparticles due to chemical stability and robust mechanical strength. However, polymeric ion exchanger containing non-diffusible negatively or positively charged groups can only permit cation or anion contaminants to permeate into the polymer phase due to Donnan exclusion effect. In this study, zero-valent iron nanoparticles (NZVI) were immobilized within a chelating resin DOW 3N with pyridine functional groups through NaBH4 reduction. TEM indicated that Fe0 particles were clearly discrete and well dispersed on the surface of DOW 3N with grain size ranging from 10 to 30nm. The reduction ability of NZVI-DOW 3N for Pb2+, NO3- and their mixture were evaluated, respectively. The results showed that NO3- and Pb2+ can be reduced efficiently. In a binary solution, the removal efficiencies of NO3- and Pb2+ can reach 87% and 97%, respectively.

Degradation of sulfamethoxazole by persulfate assisted micrometric Fe0 in aqueous solution

Persulfate (PS) chemical activation using micrometric Fe0 particles (MIPs) was tested on sulfamethoxazole (SMX) solution (39.5μM). MIPs load (0.89–17.85mM), PS content (0.4–1.0mM), pH (5.50–8.30) and alkalinity (bicarbonate) were investigated for the improvement of SMX degradation. Optimum conditions for the enhancement of the reaction stoichiometric efficiency (RSE=5.2%) were developed. HPLC–MS results confirmed that SMX was converted into its reduced form through cleavage of the isoxazole N–O bond by two routes: (i) electron abstraction upon sulfate radicals (SRs) attack yielding non stable radical cation SMX+ or (ii) electron addition through Fe0 oxidation yielding unstable radical anion SMX−. In both cases, the final transformation product was identified as b-aminoenone after acceptance of electrons originated from the MIPs surface and protons present in the acidic medium. This suggested that PS activated into SRs was responsible of the rapid degradation of SMX and its transformation product as well in contrast to Fe0 alone. Different water matrices were evaluated in order to understand the role that dissolved ions play on the reaction degradation rate. Successive experiments (n=3) of 1h each conducted on remaining Fe0 showed complete SMX degradation. The extent of SMX mineralization under the experimental conditions reached 37% making from Fe0/PS system an excellent source of SRs able to sustain oxidation reactions in aqueous media of slightly acidic pH.

Microwave-induced Degradation of Chlorobenzene Using Fe0 and TiO2 Coated on Cordierites as Catalyst

In this research, MW is used to irradiate and induce Fe0/cordierite (Fe0 coated cordierite particles) and TiO2/cordierite (TiO2 coated cordierite particles) for improving the catalytic decomposition rate to remove chlorobenzene (CB) dissolved in aqueous solution. Laboratory results show that when 30 W of microwave energy is applied for 300 sec the irradiation of microwave than without microwave irradiation improves the CB removal efficiency by 3.2 times (57.4% vs. 18.2%) for Fe0/cordierite and 2.7 times (43.3% vs. 15.8%) for TiO2/cordierite. Hence, applying the microwave induced cordierite coated Fe0 or TiO2 particles is a new application that has been proved effective to remove chlorine-containing organic pollutants.

Mössbauer study of carbon coated iron magnetic nanoparticles produced by simultaneous reduction/pyrolysis

Magnetic iron nanoparticles immersed in a carbon matrix were produced by a combined process of controlled dispersion of Fe3 + ions in sucrose, thermal decomposition with simultaneous reduction of iron cores and the formation of the porous carbonaceous matrix. The materials were prepared with iron contents of 1, 4 and 8 in %wt in sucrose and heated at 400, 600 and 800°. The samples were analyzed by XRD, Mossbauer spectroscopy, magnetization measurements, TG, SEM and TEM. The materials prepared at 400° are composed essentially of Fe3O4 particles and carbon, while treatments at higher temperatures, e.g. 600 and 800° produced as main phases Fe0 and Fe3C. The Mossbauer spectra of samples heated at 400° showed two sextets characteristic of a magnetite phase and other contributions compatible with Fe3 + and Fe2 + phases in a carbonaceous matrix. Samples treated at temperatures above 600° showed the presence of metallic iron with concentrations between 16–43%. The samples heated at 800° produced higher amounts of Fe3C (between 20% and 58%). SEM showed for the iron 8% sample treated at 600–800°C particle sizes smaller than 50 nm. Due to the presence of Fe0 particles in the carbonaceous porous matrix the materials have great potential for application as magnetic adsorbents.

Enhanced Degradation of Chlorobenzene in Aqueous Solution Using Microwave‐Induced Zero‐Valent Iron and Copper Particles

Microwaves were applied to reduce the activation energy of chlorobenzene in aqueous solution and enhance its removal using nanoscale zero-valent iron (Fe0) or zero-valent copper (Cu0) particles as dielectric media. When Fe0 and Cu0 particles absorb microwave energy, the electrical potential difference causes the metal electrons to rotate faster, thus producing more heat. The microwave-irradiated metal particles reduced the chlorobenzene activation energy by 6.1 kJ/mol (13.3 kJ/mol versus 19.4 kJ/mol) for Fe0 and 5.4 kJ/mol (15.8 kJ/mol versus 21.4 kJ/mol) for Cu0 and enhanced the chlorobenzene removal 4.1 times (82.8% versus 20.4%) for Fe0 and 3.7 times (72.1% versus 19.5%) for Cu0. The Fe0 has a higher standard reduction potential than Cu0; it is capable of removing more chlorobenzene than Cu0 (82.8% versus 72.1%). Using the microwave-induced nano-scale iron or copper particle is effective in treating toxic organic substances, as demonstrated in this study.