Application Of Nanoscale Zero-valent Iron Research Articles

Effects and mechanisms of nZVI on CO2 and CH4 emissions in uncontaminated and pentachlorophenol-contaminated soils

With the increasing application of nanoscale zero-valent iron (nZVI) for in situ soil remediation, its effects on soil functionality and ecosystem need to be thoroughly evaluated. Herein, we investigated the effects of nZVI on CO2 and CH4 emissions from uncontaminated and pentachlorophenol (PCP)-contaminated soils and the underlying microbial mechanisms by designing a 68-day anaerobic soil culture experiment; thereafter, the effects of above aged nZVI on soil CO2 and CH4 emissions in the following 20 days were further studied. In the uncontaminated soil, 1–10 g/kg nZVI treatments reduced soil CO2 emission by 17.4–82.6% and increased soil CH4 emission by 10.8%–119.7%, but these effects disappeared after the nZVI was aged. The emissions of soil CO2 and CH4 were significantly inhibited by the PCP contamination (100 mg/kg) mainly due to the toxicity to related soil microorganisms. The applications of 1–10 g/kg nZVI significantly reduced CO2 emissions from the PCP-contaminated soil by 24.0–86.7%, while 10 g/kg nZVI markedly increased soil CH4 emission by 1875.4% and restored the methanogenic activity to the control level after the nZVI was aged. The 10 g/kg nZVI treatment enriched hydrogenotrophic methanogen (Methanobacterium) and organics-degrading bacteria by releasing H2, increasing soil pH, and decreasing soil Eh; the abundance of genes encoding key enzymes (Mcr, Mtr, Hdr, Mta, and Mtb) in all methanogenic pathways significantly increased after the nZVI treatment, indicating that nZVI could have a broad promoting effects on soil methanogenic processes. The findings demonstrate that the addition of nZVI for in situ remediation of organochlorines-contaminated soils will affect soil greenhouse gas emissions and provide basic data for safe nZVI applications.

NZVI-Based Nanomaterials Used for Phosphate Removal from Aquatic Systems.

In the last decade, the application of nanoscale zero-valent iron (nZVI) has garnered great attention as an adsorbent due to its low cost, non-toxicity, high porosity, and BET-specific surface area. In particular, the immobilization of nZVI particles onto inorganic and organic substrates (nanocomposites) decreased its agglomeration, allowing them to be effective and achieve greater adsorption of pollutants than pristine nanoparticles (NPs). Although nZVI began to be used around 2004 to remove pollutants, there are no comprehensive review studies about phosphate removal from aquatic systems to date. For this reason, this study will show different types of nZVI, pristine nZVI, and its nanocomposites, that exist on the market, how factors such as pH solution, oxygen, temperature, doses of adsorbent, initial phosphate concentration, and interferents affect phosphate adsorption capacity, and mechanisms involved in phosphate removal. We determined that nanocomposites did not always have higher phosphate adsorption than pristine nZVI particles. Moreover, phosphate can be removed by nZVI-based nanoadsorbents through electrostatic attraction, ion exchange, chemisorption, reduction, complexation, hydrogen bonding, and precipitation mechanisms. Using the partition coefficient (PC) values, we found that sepiolite-nZVI is the most effective nanoadsorbent that exists to remove phosphate from aqueous systems. We suggest future studies need to quantify the PC values for nZVI-based nanoadsorbents as well as ought to investigate their phosphate removal efficiency under natural environmental conditions.

Carbothermal Synthesis of Sludge Biochar Supported Nanoscale Zero-Valent Iron for the Removal of Cd2+ and Cu2+: Preparation, Performance, and Safety Risks

The practical application of nanoscale zero-valent iron (NZVI) is restricted by its easy oxidation and aggregation. Here, sludge biochar (SB) was used as a carrier to stabilize NZVI for Cd2+ and Cu2+ removal. SB supported NZVI (SB-NZVI) was synthesized using the carbothermic method. The superior preparation conditions, structural characteristics, and performance and mechanisms of the SB-NZVI composites for the removal of Cd2+ and Cu2+ were investigated via batch experiments and characterization analysis. The optimal removal capacities of 55.94 mg/g for Cd2+ and 97.68 mg/g for Cu2+ were achieved at a Fe/sludge mass ratio of 1:4 and pyrolysis temperature of 900 °C. Batch experiments showed that the SB-NZVI (1:4-900) composite had an excellent elimination capacity over a broad pH range, and that weakly acidic to neutral solutions were optimal for removal. The XPS results indicated that the Cd2+ removal was mainly dependent on the adsorption and precipitation/coprecipitation, while reduction and adsorption were the mechanisms that play a decisive role in Cu2+ removal. The presence of Cd2+ had an opposite effect on the Cu2+ removal. Moreover, the SB-NZVI composites made of municipal sludge greatly reduces the leaching toxicity and bio-availability of heavy metals in the municipal sludge, which can be identified as an environmentally-friendly material.

Reciprocal interferences of heavy metal and dissolved organic matter on their immobilizations by modulating the interfacial interactions with nanoscale zero-valent iron

With the increasing application of nanoscale zero-valent iron (nZVI) in environmental remediation, exploring the reciprocal effects of heavy metals (HMs) and dissolved organic matter (DOM) on their immobilizations by nZVI is crucial for predicting carbon dynamics and contaminant behavior in the environment. By using manifold analyses, the reciprocal effects of HMs (Cr(VI) and Cd(II)) and humic acid (HA) on their immobilizations by modulating the interfacial interactions with nZVI were systematically investigated. It was found that the previous interaction of HA especially its contained nonfluorescent substances (i.e., lipids, polysaccharides, and lignin) with nZVI improved the immobilization of HMs on nZVI; the previous interaction of Cd(II) with HA or nZVI promoted the sequestration of organic carbon (up to 1.8-fold) especially the aromatic carbon and humic-like fluorophores of HA by nZVI, but Cr(VI) had no such effect. The oxidized iron complexes on nZVI dominated the ultimate immobilizations of HA and HMs. The increased immobilizations of unsaturated hydrocarbons and quinone ketones by the formed nZVI-HM complexes decreased the reduction capability but enhanced the photochemical stability of the residual aqueous HA. These findings are of significance to understanding nZVI interactions with DOM and HMs and the effects on the carbon cycle and HM immobilization in the environment.

Nanocelluloses affixed nanoscale Zero-Valent Iron (nZVI) for nickel removal: Synthesis, characterization and mechanisms

Application of nanoscale Zero-Valent Iron (nZVI) for heavy-metal enrichment and recovery have been hampered by aggregation induced by its high surface energy and intrinsic magnetic interactions. Herein, we present nanocelluloses (NC) affixed nZVI composite (NC-nZVI) with enhanced efficiency for Nickel(Ni) removal. The anchoring of nZVI at the functional sites of biomass derived NC was initiated by one-step liquid-phase reduction method, generating varied morphology and dispersion status of nZVI. Among developed composites, cellulose nanocrystals (CNC) modified nZVI (CNC-nZVI) showed most evenly distributed nZVI with uniform particle size. Characterizations with FTIR, XPS and XRD demonstrated that bindings between NC and nZVI were through hydrogen bonds, electrostatic attractions, coordination-covalent bonds and/or steric hindrance. For Ni2+ removal, 0.2 g/L CNC-nZVI achieved 98.5% removal rate at 100 mg/L initial Ni2+ concentration and pH = 5.0, significantly higher than bare nZVI (P < 0.05). The removal efficiency remained over 80% under wide pH range (3–5) and varied interference ions (NO3-, Cl- and Ca2+), indicating potential practical applicability. The observed "hollow-out" structure from scanning transmission electron microscopy after reactions with Ni2+ and Tafel extrapolation curves inferred that CNC activated diffusion path and accelerated electronic transfer from nZVI. The superior removal performance of NC-nZVI and abundance of raw materials offer promising prospects for environmental remediation and wastewater treatment.

Effects of green synthesized and commercial nZVI on crystal violet degradation by Burkholderia vietnamiensis C09V: Dose-dependent toxicity and biocompatibility

The increasingly common remedial application of nanoscale zero-valent iron (nZVI) to alleviate specific contaminant issues may inadvertently lead to nZVI accumulation in wastewater. This is a potential concern, because the effect of nZVI on the common microbes essential for wastewater biotreatment is not known. This is further complicated when there are many ways available to synthesize nZVI, which may interreact with bacteria differently. Thus, in this study, the different effects of nZVI synthesized by Eucalyptus leaves (EL-nZVI) and a commercially synthesized nZVI on the biodegradation of crystal violet by Burkholderia vietnamiensis C09V (B.V. C09V) was studied. At high dose (1000 mg/L), EL-nZVI and commercial nZVI both significantly inhibited the removal of crystal violet by B.V. C09V, decreasing removal rates by 10.5 and 13.1% respectively. Optical density (OD600) and soluble protein assays indicated that the growth of B.V. C09V improved under low doses (100 mg/L), but remained inhibited under high doses (500 and 1000 mg/L) of both commercial and EL-nZVI. Enzymes were also sensitive to nZVI, where the commercial variant exerted a greater effect on both the activity of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) than EL-nZVI, indicating that EL-nZVI was less toxic than commercial nZVI. LIVE/DEAD staining also showed that the number of apoptotic cells was significantly higher when exposed to commercial nZVI rather than EL-nZVI. Furthermore, scanning electron microscopy (SEM) confirmed that direct contact between nZVI and cells at 1000 mg/L nZVI caused cell membrane disruption. Whereas, at 100 mg/L EL-nZVI, B.V. C09V grew better due to the formation of dense biofilms around the suspended EL-nZVI at a. Fourier transform infrared spectra (FTIR), confirmed an abundance of oxygen-containing functional groups on the surface of EL-nZVI which provided better biocompatibility than commercial nZVI. Overall, while dose was the most significant factor influencing nZVI toxicity, surface composition and morphology was also important. These new findings suggest chemical synthesis of metal nanoparticles should be replaced by biosynthetic routes to maintain viable microbial pollution during wastewater treatment.

Removal of Polycyclic Aromatic Hydrocarbons in a Heterogeneous Fenton Like Oxidation System Using Nanoscale Zero-Valent Iron as a Catalyst

Oil and gas effluents contains highly toxic and harmful organic pollutants. Therefore, it is necessary to eliminate and/or reduced the concertation of organic pollutants to a technologically acceptable levels before their discharge into water streams. This study investigates the application of nanoscale zero-valent iron (nZVI), and hydrogen peroxide (H2O2) for removal of organic pollutants from real oily produced water. Batch studies were performed and effect of different operating parameters, including concentration of nZVI and H2O2, pH and reaction time were studied. Moreover, optimization of independent variables was performed using central composite design (CCD) in response surface methodology (RSM). The experimental set up provided maximum removal efficiencies of 89.5% and 75.3% for polycyclic aromatic hydrocarbons (PAHs) and chemical oxygen demand (COD), respectively. The optimum values of independent variables such as concentrations of nZVI, and H2O2, contact time and pH were obtained as 4.35 g/L, 1.60 g/L, 199.9 min and 2.9, respectively. Predicted PAHs and COD removal efficiencies at the optimum values of independent variables were found as 89.3% and 75.7%, respectively which are in line with the experimental values. The study indicates that application of heterogeneous Fenton like oxidation system using nZVI as a catalyst is an efficient treatment method for removal of organic pollutants from real produced water.

Application of nanoscale zero-valent iron in hexavalent chromium-contaminated soil: A review

Abstract Chromium (Cr) is a common toxic heavy metal that is widely used in all kinds of industries, causing a series of environmental problems. Nanoscale zero- valent iron (nZVI) is considered to be an ideal remediation material for contaminated soil, especially for heavy metal pollutants. As a material of low toxicity and good activity, nZVI has been widely applied in the in situ remediation of soil hexavalent chromium (Cr(vi)) with mobility and toxicity in recent years. In this paper, some current technologies for the preparation of nZVI are summarized and the remediation mechanism of Cr(vi)-contaminated soil is proposed. Five classified modified nZVI materials are introduced and their remediation processes in Cr(vi)-contaminated soil are summarized. Key factors affecting the remediation of Cr(vi)-contaminated soil by nZVI are studied. Interaction mechanisms between nZVI-based materials and Cr(vi) are explored. This study provides a comprehensive review of the nZVI materials for the remediation of Cr(vi)-contaminated soil, which is conducive to reducing soil pollution.

Enhanced removal of Cr(VI) from wastewater by nanoscale zero valent iron supported on layered double hydroxides

The application of nanoscale zero-valent iron (NZVI) in a promising remediation strategy was challenged by easy aggregation and surface passivation. To enhance their performance of Cr(VI) removal, layered double hydroxides (LDHs) supported NZVI (NZVI@LDH) with different loading amount via an in-situ way was successfully synthesized. The structural characterization and morphology revealed LDHs could stabilize and uniformly disperse NZVI on the surface of LDHs layer, however, superabundant NZVI still leaded to a visibly aggregation. Cr(VI) removal by NZVI@LDH was higher than that of the sum of NZVI and LDHs, revealing a synergistic effect within this system. The results of Cr(VI) removal displayed with the growth of iron loading amount, the removal efficiencies were raised firstly but declined afterwards. Kinetics studies for all samples showed Cr(VI) removal well fitted pseudo-second-order model and isotherm data was well described by Langmuir model. The effects of initial concentration and pH on Cr(VI) removal were also examined. Cr(VI) in the wastewater was reduced by NZVI to Cr(III), NZVI was oxidized into Fe(II) and Fe(III). The excellent removal performance suggested a promising strategy in sewage water remediation.

Groundwater Chemistry Has a Greater Influence on the Mobility of Nanoparticles Used for Remediation than the Chemical Heterogeneity of Aquifer Media

The application of nanoscale zerovalent iron (nano-ZVI) particles for groundwater remediation has spurred research into the influence of the collector heterogeneity on the nano-ZVI mobility. The chemical heterogeneity of surfaces within aquifer media affects their surface charge distribution and their affinity for nano-ZVI. The groundwater chemistry affects the properties of both aquifer surfaces and the nano-ZVI particles. Commercial poly(acrylic acid)-coated nano-ZVI (PAA-nano-ZVI) particles were tested in column experiments using two solution chemistries and silica collectors with different degrees of chemical heterogeneity, achieved by ferrihydrite coating. A porous media filtration model was used to determine the attachment efficiency of PAA-nano-ZVI particles, and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to describe the interactions between PAA-nano-ZVI particles and the aquifer "collectors". The mobility of PAA-nano-ZVI particles suspended in ultrapure water depended on the extent of ferrihydrite coating on the collector surfaces. The mobility of PAA-nano-ZVI particles under environmentally relevant conditions was independent of the collector chemical heterogeneity. The size of PAA-nano-ZVI aggregates doubled, inducing gravitational sedimentation and possibly straining as mechanisms of particle deposition. There was no repulsive energy barrier between particles and collectors, and the DLVO theory was unable to explain the observed particle attachment. Our results suggest that the groundwater chemistry has a greater influence on the mobility of PAA-nano-ZVI particles than the collector chemical heterogeneity. A better understanding of polymer adsorption to nanoparticles and its conformation under natural groundwater conditions is needed to further elucidate nanoparticle-collector interactions.

Effect of Flow Rate and Particle Concentration on the Transport and Deposition of Bare and Stabilized Zero-Valent Iron Nanoparticles in Sandy Soil

Efficient application of nanoscale zero-valent iron (nZVI) particles in remediation processes relies heavily on the ability to modify the surfaces of nZVI particles to enhance their stability and mobility in subsurface layers. We investigated the effect of sodium carboxy-methyl-cellulose (CMC) polymer stabilizer, pH, particle concentration, and flow rate on the transport of nZVI particles in sand columns. Breakthrough curves (BTCs) of nZVI particles indicated that the transport of nZVI particles was increased by the presence of CMC and by increasing the flow rate. The relative concentration (RC) of the eluted CMC–nZVI nanoparticles was larger at pH 9 as compared to RC at pH 7. This is mainly attributed to the increased nZVI particle stability at higher pH due to the increase in the electrostatic repulsion forces and the formation of larger energy barriers. nZVI particle deposition was larger at 0.1 cm min-1 flow due to the increased residence time, which increases the aggregation and settlement of particles. The amount of CMC–nZVI particles eluted from the sand columns was increased by 52% at the maximum flow rate of 1.0 cm min-1. Bare nZVI were mostly retained in the first millimeters of the soil column, and the amount eluted did not exceed 1.2% of the total amount added. Our results suggest that surface modification of nZVI particles was necessary to increase stability and enhance transport in sandy soil. Nevertheless, a proper flow rate, suitable for the intended remediation efforts, must be considered to minimize nZVI particle deposition and increase remediation efficiency.

Bioremediation vs. Nanoremediation: Degradation of Polychlorinated Biphenyls (PCBS) Using Integrated Remediation Approaches

Integration of physicochemical and biological approach represented by sequential application of nanoscale zerovalent iron (nZVI dispersion) and bioaugmentation by bacterial strains isolated from the PCB-contaminated site seems to be an innovative way to remove the PCB contamination, which still persists in the environment. First, nanoremediation of the minimal mineral medium artificially contaminated with Delor 103 and of historically contaminated sediment was performed in 70% and 46% PCB removal efficiency. Integrated remediation was carried out as bionanoremediation initiated by addition of bacterial strains and finished by addition of nZVI dispersion Nanofer 25S. Nanobioremediation initiated by nZVI and followed by the addition of bacterial strains A. xylosoxidans, S. maltophilia, and O. anthropi was more effective and led to the increase of PCB degradation to 75%, 85%, and 99%. The bacterial mixed culture (BMC) consisted of 7 bacterial strains with PCB-degrading activity was used for integrated remediation, as well. By the nanobioremediation of the historically contaminated sediment, 78% degradation of PCBs was achieved by combining the nZVI and BMC, with the addition of non-ionic surfactant Triton X-100. The sediment was periodically reinoculated with fresh nZVI dispersion and BMC inoculum. The possible toxic effects of nZVI in concentration used in integrated remediation 2 g l−1 were evaluated on bacterial strains used for integrated remediation. The cell concentrations of the bacterial strains A. xylosoxidans, S. maltophilia, and O. anthropi, expressed as CFU ml−1, decreased in the presence of nZVI by 75%, 52%, and 61%, respectively.

Nanoscale zero-valent iron supported on biochar for the highly efficient removal of nitrobenzene

The application of nanoscale zero-valent iron (nZVI) in the remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation and iron leaching. To address this issue, nZVI was distributed on oak sawdust-derived biochar (BC) to obtain the nZVI/BC composite for the highly efficient reduction of nitrobenzene (NB). nZVI, BC and nZVI/BC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For nZVI/BC, nZVI particles were uniformly dispersed on BC. nZVI/BC exhibited higher removal efficiency for NB than the simple summation of bare nZVI and BC. The removal mechanism was investigated through the analyses of UV-Visible spectra, mass balance and XPS. NB was quickly adsorbed on the surface of nZVI/BC, and then gradually reduced to aniline (AN), accompanied by the oxidation of nZVI to magnetite. The effects of several reaction parameters, e.g., NB concentration, reaction pH and nZVI/BC aging time, on the removal of NB were also studied. In addition to high reactivity, the loading of nZVI on biochar significantly alleviated Fe leaching and enhanced the durability of nZVI.

Applications of nanoscale zero-valent iron and its composites to the removal of antibiotics: a review

Nanoscale zero-valent iron (nZVI, nFe0) particles have been investigated in recent years as a promising material for the removal of antibiotics from water environment. Although the potential benefits of nZVI in environmental remediation are considerable, there is a distinct need to rationally apply zero-valent iron-based (nano)materials to antibiotics removal in hydrosphere. This review supplied current opinions about the most recent works, which have been carried out toward the applications of various zero-valent iron-based (nano)materials (e.g., pristine nZVI, surface-modified nZVI, porous material-supported nZVI, inorganic clay mineral-supported nZVI and material-encapsulated nZVI) to the removal of antibiotics from water. The corresponding interaction mechanisms between the various zero-valent iron-based (nano)materials and the antibiotics, including adsorption, reduction, oxidation and other special interaction mechanisms, were discussed. The key influencing factors affecting the reactivities of the zero-valent iron-based (nano)materials with antibiotics (e.g., solution pH, solution temperature, nZVI dosage, coexisting oxy-anions and cations) were highlighted. It demonstrated that the zero-valent iron-based (nano)materials possess high reactivities with antibiotics and have great application prospects in water environmental remediation.

Stabilization of nanoscale zero-valent iron in water with mesoporous carbon (nZVI@MC)

Two challenges persist in the applications of nanoscale zero-valent iron (nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxidation. Herein, we report the nZVI incorporated into mesoporous carbon (MC) to enhance stability in aqueous solution and mobility in porous media. Meanwhile, the reactivity of nZVI is preserved thanks to high temperature treatment and confinement of carbon framework. Small-sized (~16 nm) nZVI nanoparticles are uniformly dispersed in the whole carbon frameworks. Importantly, the nanoparticles are partially trapped across the carbon walls with a portion exposed to the mesopore channels. This unique structure not only is conductive to hold the nZVI tightly to avoid aggregation during mobility but also provides accessible active sites for reactivity. This new type of nanomaterial contains ~10 wt% of iron. The nZVI@MC possesses a high surface area (~500 m2/g) and uniform mesopores (~4.2 nm) for efficient pollutant diffusion and reactions. Also, high porosity of nZVI@MC contributes to the stability and mobility of nZVI. Laboratory column experiments further demonstrate that nZVI@MC suspension (~4 g Fe/L) can pass through sand columns much more efficiently than bare nZVI while the high reactivity of nZVI@MC is confirmed from reactions with Ni(II). It exhibits remarkably better performance in nickel (20 mg/L) extraction than mesoporous carbon, with 88.0% and 33.0% uptake in 5 min, respectively.

The Application of Nanoscale Zero-Valent Iron Promotes Soil Remediation While Negatively Affecting Soil Microbial Biomass and Activity

The use of nanoscale zero-valent iron particles (nZVI) for soil remediation is gaining increased attention. However, there are concerns about the potential adverse effects of nZVI on soil microbial communities and, hence, soil quality. The objective of this study was to assess the impact of the application of nZVI on soil microbial parameters (as bioindicators of soil quality) during the nanoremediation of a soil artificially contaminated with lindane (10 mg γ-HCH kg-1 DW soil) and zinc (1,500 mg Zn kg-1 DW soil). nZVI were also applied to non-contaminated soil. The following nZVI doses were applied twice: 0, 0.25, 0.5, 1 and 2 mg nZVI g-1 DW soil. Nine weeks after nZVI application, the following parameters were determined in soil samples: lindane concentration, extractable Zn concentration, microbial biomass carbon (CMB), bacterial and fungal abundance (gene copy numbers by qPCR), enzyme activities (β-glucosidase, β-glucosaminidase, xylosidase, acid phosphatase, arylsulphatase and Leu-aminopeptidase) and bacterial richness by ARISA profiles. The application of nZVI reduced lindane and extractable Zn concentrations following a dose-dependent pattern. The presence of contaminants reduced soil microbial biomass and activity. The application of nZVI negatively affected the microbial quality of the contaminated soil but not of the non-contaminated soil. This observation might reflect a “stress-on-stress” effect, i.e. the already stressed microbial populations present in the contaminated soil were more sensitive to the application of nZVI (a second stress) than those present in the non-contaminated soil.

Multivariate optimization of ciprofloxacin removal by polyvinylpyrrolidone stabilized NZVI/Cu bimetallic particles

A combined system of polyvinylpyrrolidone (PVP) and nanoscale zerovalent iron (NZVI) with copper (Cu) bimetallic particles (PVP-NZVI/Cu) was designed for ciprofloxacin (CIP) reduction under weak magnetic field (WMF) condition. The surface morphology and physicochemical properties of the novel catalytic materials were further characterized. In addition, the catalytic reactivity of PVP-NZVI/Cu was determined in the presence or absence of WMF. Experimental results demonstrated that the catalytic performance of PVP-NZVI/Cu system was enhanced by the introduction of WMF with maximum removal rate of CIP reaching 95.6% (120 min). Kinetic analysis exhibited that the degradation of CIP in compliance with pseudo-first-order kinetics. Eventually, the degradation products of CIP after reacting with the PVP-NZVI/Cu nanocomposites were determined by the mass spectrometry (MS). Quantitative analysis of PVP-NZVI/Cu adsorption and Fenton oxidation during the CIP removal process were also evaluated. The roles of PVP-NZVI/Cu adsorption/Fenton oxidation were dynamically changed and the Fenton oxidation was observed to be greatly strengthened as the removal process proceeded. The study provided a new insight into the removal of CIP by NZVI, which has prospect for the practical application of NZVI.

Chemical pathways of Nanoscale Zero-Valent Iron (NZVI) during its transformation in aqueous solutions

The current application of Nanoscale Zero-Valent Iron (NZVI) is subject to the countermeasure of water contamination that escalates with increasing population. Some of the NZVI advantages include; environmental friendliness, high reactivity and cost-effectiveness. NZVI was synthesized through the reduction of a ferric ion by sodium borohydride in anoxic medium and the resulting particles were characterized by the Transmission Electron Microscope with Energy-dispersive X-ray (TEM-EDX). The NZVI evolution and dissolution in water were examined through a series of batch experiments conducted in varying experimental conditions which include; pH, temperature, dosage, oxygen and interferences. The dissolution of iron was enhanced in the acidic pH due to the presence of H+ ions thus favoring release of hydrogen gas. More iron ions were present in the lowest temperature (5 °C) due to decreased crystallization and proton assisted dissolution. Furthermore, highest NZVI dosage (3 g/L) resulted in the highest iron ions concentrations in solution due to the increased number of nanoparticles hence providing surface-active sites. Ultimately, more iron ions were present in limited oxygen supply condition involving initial air saturation showed due to decreased crystallization and precipitation which were favored in continuous supply. These results are a useful guidance during real-life application of NZVI.

Ligand-mediated contaminant degradation by bare and carboxymethyl cellulose-coated bimetallic palladium-zero valent iron nanoparticles in high salinity environments

The application of nanoscale zero-valent iron (nZVI) for the degradation of contaminants has been extensively investigated, however, few studies have focused on degradation in high salinity environments. In this study, the ability of bare and carboxymethyl cellulose (CMC)-coated bimetallic Pd-nZVI particles to degrade 33′44′-tetrachlorobiphenyl in high saline water (SW) is examined with particular attention given to the effects of ethylenediaminetetraacetic acid (EDTA) on the rate of degradation. EDTA enhances the reactivity of Pd-nZVI in SW, with evidence provided to link this to the removal of the passivating layer. Additionally, a conceptual model is proposed which provides a quantitative description of the removal of these iron oxide layers in the presence of EDTA. An optimum EDTA to bare Pd-nZVI molar ratio of 0.1 exists, with insufficient EDTA unable to remove the passivating layer whilst excess EDTA results in Fe loss and enhanced agglomeration due to magnetic attraction of the bare Fe(0) particles. In contrast, CMC-coating of Pd-nZVI assemblages actually impedes degradation, despite the coated particles displaying a smaller average size compared to uncoated particles, with even the presence of EDTA in this case not significantly improving degradation. The reduced reactivity in the presence of CMC is primarily attributed to the effect of CMC on the association of Pd with nZVI particles. In particular, the presence of CMC reduced the total amount of Pd incorporated with the stabilized particles compared to the non-stabilized particles. Additionally, the presence of CMC results in less Pd present in its reactive zero-valent oxidation state.

Synthesis, characterization and application of nanoscale zero-valent iron in the degradation of the azo dye Disperse Red 1

In this work, a multivariate response surface methodology (RSM), was applied to analyze the effects of the synthesis variables that affect the reactivity of nanosized zero valent iron particles (NZVI), obtained by chemical reduction with sodium borohidride on the decoloration of azo dye Disperse Red 1 (DR1). Statistical analysis and data interpretation revealed that the generated model showed significant regression and fitting. The conditions that generated NZVI with higher reactivity correspond to [Fe 2+]:[BH4−] molar ratio=1:3, higher rates of reducing agent addition and lower pH (2–3). NZVI particles synthesized under the optimal conditions were characterized via XRD, BET surface area and electron microscopy. The results showed that the nanostructured material had composition, morphology and crystallinity typical of zero-valent iron, with BET surface area of ​​45m2g−1 and an average particle size of 60nm. NZVI yielded high color removal in fairly short time (around 98% in 10min). Latter combination with H2O2 allowed high mineralization.