nZVI Particles Research Articles

Chromate removal by surface-modified nanoscale zero-valent iron: Effect of different surface coatings and water chemistry

This study investigated the correlation between the colloidal stability and reactivity of surface-modified nano zero-valent iron (SM-nZVI) as affected by the surface coating (i.e., polyacrylic acid [PAA] and starch) under various geochemical conditions. Generally, the colloidal stability of nZVI was enhanced with increasing loading of surface coating, while there is an optimum loading for the most efficient Cr(VI) removal by SM-nZVI. At lower loadings than the optimum loading, the surface coating could enhance the particle stabilization, facilitating the Cr(VI) reduction by providing more available surface sites. However, the over-loaded surface coating on the surface of nZVI particles decreased the Cr(VI) reduction due to the occupation of the reactive sites and the inhibition of the mass transfer of Cr(VI) ions from water to the particle surface by providing the electrostatic or steric repulsion. The effects of Ca2+ ions or humic acid (HA) on the colloidal stability and reactivity of PAA-modified nZVI (P-nZVI) and starch-modified nZVI (S-nZVI) were examined. Differing stability behavior and reactivity were observed for different SM-nZVI. It was found that the presence of Ca2+ or HA altered surface chemistry of SM-nZVI, the particle-particle interaction and the particle-contaminant interaction, and hence influencing the stability behavior and reactivity of the particles.

Photoelectrochemical Solar Cells Prepared From Nanoscale Zerovalent Iron Used for Aqueous Cd2+ Removal

Nanoscale zerovalent iron (nZVI) particles have been widely studied in the environmental sciences for wastewater treatment. These types of nanoparticles react in aqueous media producing metal oxides, which can be photoactive in the ultraviolet energy region. This prompted us to examine alternatives for the preparation of nanomaterials using nZVI in the presence of 6 and 30 ppm of Cd2+ in aqueous solutions. These Cd2+ concentrations are representative of contaminated regions of Puerto Rico such as the Las Cucharillas Marsh in Catano. Comprehensive chemical and physical characterization of the resulting nZVI products after their exposure to Cd2+ was done. Further studies of the resulting nanostructures were completed using a photoelectrochemical solar cell (PSC) as the photoanode material. Incident photon-to-current efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) analysis of these PSCs showed active photochemical properties in the ultraviolet range for the sample exposed to 30 ppm of Cd2+...

Synthesis of iron-based nanoparticles and comparison of their catalytic activity for degradation of phenolic waste water in a small-scale batch reactor

In the present work, iron-based nanoparticles were synthesized by sol–gel method (iron oxide I), modified co-precipitation method (iron oxide II), reduction of FeSO4 by NaBH4 (nano zero-valent iron I, nZVI I), and reduction of FeSO4 by NaBH4 in presence of chelating ligand EDTA (nZVI II) for use as a catalyst for degradation of phenol. Particle characterization was performed for each set of samples by UV–vis spectra, X-ray diffraction, Fourier transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM). FESEM was performed with iron oxide II and particle size was found to be 36.5 nm. The average particle diameter obtained for nZVI was in the range of 141–150 nm. nZVI(II) has been found to be most efficient with respect to high percentage degradation of phenol in an hour under optimum operating condition at room temperature which were as follows: catalyst concentration = 0.05 g/l, pH 3, phenol:hydrogen peroxide (50%) concentration = 1:14 (stoichiometric ratio), temperature = ambient. Brunauer–Emmett–Teller (BET) surface area measurement also showed higher surface area for nano zero-valent iron (nZVI) particles than compared to other iron oxides. The initial phenol concentration was varied in the range of 50–400 mg/l. Degradation efficiency was found decreasing with increasing initial concentration of phenol. Iron oxide I and II can be successfully recovered and reused.

Nano zerovalent iron particles induce pulmonary and cardiovascular toxicity in an in vitro human co-culture model

Despite promising environmental applications for nano zerovalent iron (nZVI), concerns remain about the potential accumulation and toxic effects of nZVI particles. Here, we use an alveolar-capillary co-culture model to investigate a possible link between low-level epithelial exposure to nZVI and pulmonary and cardiovascular toxicity. While nZVI was unable to pass through the epithelial barrier into the endothelium, nZVI exposure did cause oxidative and inflammatory responses in both epithelial and endothelial cells. Therefore, toxic effects induced by nZVI are not restricted to epithelial cells but can be transferred into the endothelium. Communication between A549 and EA.hy926 cells is responsible for amplification of nZVI-induced toxic responses. Decreases in transepithelial electrical resistance and zonula occludens proteins after epithelial exposure to nZVI impaired epithelial barrier integrity. Increases in oxidized α1-antitrypsin and oxidized low-density lipoprotein in the co-culture model suggest that nZVI exposure increases the risk of chronic obstructive pulmonary disease and atherosclerosis. Therefore, inhalation of nZVI has the potential to induce cardiovascular disease through oxidative and inflammatory mediators produced from the damaged lung epithelium in chronic lung diseases.

Combined nano-biotechnology for in-situ remediation of mixed contamination of groundwater by hexavalent chromium and chlorinated solvents

The present report describes a 13month pilot remediation study that consists of a combination of Cr(VI) (4.4 to 57mg/l) geofixation and dechlorination of chlorinated ethenes (400 to 6526μg/l), achieved by the sequential use of nanoscale zerovalent iron (nZVI) particles and in situ biotic reduction supported by whey injection. The remediation process was monitored using numerous techniques, including physical–chemical analyses and molecular biology approaches which enabled both the characterization of the mechanisms involved in pollutant transformation and the description of the overall background processes of the treatment. The results revealed that nZVI was efficient toward Cr(VI) by itself and completely removed it from the groundwater (LOQ 0.05mg/l) and the subsequent application of whey resulted in a high removal of chlorinated ethenes (97 to 99%). The persistence of the reducing conditions, even after the depletion of the organic substrates, indicated a complementarity between nZVI and the whey phases in the combined technology as the subsequent application of whey phase partially assisted the microbial regeneration of the spent nZVI by promoting its reduction into Fe(II), which further supported remediation conditions at the site. Illumina sequencing and the detection of functional vcrA and bvcA genes documented a development in the reducing microbes (iron-reducing, sulfate-reducing and chlororespiring bacteria) that benefited under the conditions of the site and that was probably responsible for the high dechlorination and/or Cr(VI) reduction. The results of this study demonstrate the feasibility and high efficiency of the combined nano-biotechnological approach of nZVI and whey application in-situ for the removal of Cr(VI) and chlorinated ethenes from the groundwater of the contaminated site.

Adsorptive removal of arsenate from aqueous solutions by biochar supported zero-valent iron nanocomposite: Batch and continuous flow tests

Arsenate (As(V)) removal ability by nanoscale zero-valent iron (nZVI) is compromised by aggregation of nZVI particles. In this work, pine derived biochar (PB) was used as a supporting material to stabilize nZVI for As(V) removal. The biochar supported nZVI (nZVI/BC) was synthesized by precipitating the nanoparticles on carbon surfaces. Experiments using batch and continuous flow, completely mixed reactors (CMRs) were carried out to investigate the removal of As(V) by the nZVI/BC from aqueous solutions. Batch experiments showed that nZVI/BC had high As(V) removal capacity in a wide range of pH (3–8). Kinetic data revealed that equilibrium was reached within 1h and the isotherm data showed that the Langmuir maximum adsorption capacity of the nZVI/BC for As(V) at pH 4.1 was 124.5gkg−1. As(V) (100mgL−1) adsorption in anoxic condition was about 8% more than in oxic conditions, where As(V) reduction was observed in anoxic condition. The performance of the nZVI/BC in flowing condition was evaluated in CMRs at influent As(V) concentrations of 2.1 and 5.5mgL−1 and the adsorbent removed 100% and 90% of the As(V), respectively. Furthermore, the nZVI/BC composite is magnetic which facilitates collection from aqueous solutions.

Influence of fulvic acid on the colloidal stability and reactivity of nanoscale zero-valent iron

This study investigated the effect of fulvic acid (FA) on the colloidal stability and reactivity of nano zero-valent iron (nZVI) at pH 5, 7 and 9. The sedimentation behavior of nZVI differed at different pH. A biphasic model was used to describe the two time-dependent settling processes (i.e., a rapid settling followed by a slower settling) and the settling rates were calculated. Generally, the settling of nZVI was more significant at the point of zero charge (pHpzc), which could be varied in the presence of FA due to the adsorption of FA on the nZVI surface. More FA was adsorbed on the nZVI surface at pH 5–7 than pH 9, resulting in the varying sedimentation behavior of nZVI via influencing the electrostatic repulsion among particles. Moreover, it was found that there was a tradeoff between the stabilization and the reactivity of nZVI as affected by the presence of FA. When FA concentration was at a low level, the adsorption of FA on the nZVI surface could enhance the particle stabilization, and thus facilitating the Cr(VI) reduction by providing more available surface sites. However, when the FA concentrations were too high to occupy the active surface sites of nZVI, the Cr(VI) reduction could be decreased even though the FA enhanced the dispersion of nZVI particles. At pH 9, the FA improved the Cr(VI) reduction by nZVI. Given the adsorption of FA on the nZVI surface was insignificant and its effect on the settling behavior of nZVI particles was minimal, it was proposed that the FA formed soluble complexes with the produced Fe(III)/Cr(III) ions, and thus reducing the degree of passivation on the nZVI surface and facilitating the Cr(VI) reduction.

Electrospun membrane composed of poly[acrylonitrile-co-(methyl acrylate)-co-(itaconic acid)] terpolymer and ZVI nanoparticles and its application for the removal of arsenic from water

We present a facile approach to immobilizing nanoscale zero valent iron (nZVI) particles onto an electrospun membrane based on poly[acrylonitrile-co-(methyl acrylate)-co-(itaconic acid)] (hereinafter referred to as AN/MA/IA).

Stability of green tea nanoscale zero-valent iron

Colloidal suspension of nano zero-valent iron (nZVI), obtained as a result of mixing green tea (GT) solution with iron solutions (FeCl2 and FeSO4 separately to form two suspensions: GT-nZVIFeCl2 and GT-nZVIFeSO4 ) was assessed in terms of stability. The particles of suspensions had a tendency rapidly aggregation to form larger aggregates, and then settled. The absolute value of zeta potential (ζ) of suspensions did not exceed 17 mV. To prevent the aggregation of nZVI particles, the pHs were changed by the addition of Na2 CO3 to obtain higher values of ζ. For both suspensions, the zeta potential at a satisfactory level was obtained at pH values higher than 7.5. Then, the potential was lower than −40 mV for GT-nZVIFeCl2 and lower than −25mV for GT-nZVIFeSO4 . This means that the first suspension had a better stability than second. The isoelectric point (IEP) of GT-nZVIFeCl2 was in the range from 4.5 to 5, while in the case of GT-nZVIFeSO4 all measured ζ were negative. To investigate the effect of increased ionic strength (IS) on the stability of suspensions at different pH values, NaCl and MgSO4 were added to the irons solutions. The final IS in the GT-nZVI was 12 mM. In both of the suspensions the absolute values of ζ were lower than previous and were about 25 and 20 mV, for GT-nZVIFeCl2 and GT-nZVIFeSO4 , respectively.

Bactericidal effect of starch-stabilized zero-valent iron nanoparticles onEscherichia coli

Aims: The present study reports the antibacterial efficiency of starch-stabilized nano scale zero-valent iron (S-NZVI) particles on Escherichia coli. Materials and Methods: NZVI was synthesized using NaBH 4 and FeSO 4 .7H 2 O, and characterized by scanning electron microscopy, as well as X-ray diffraction. The effects of concentration, contact time, dissolved oxygen, and stabilization were tested. E. coli was determined by the pour plate method. Results: The results revealed that the complete inactivation (100%) of E. coli was occurred at using 100 mg/l of NZVI after 30 min under anaerobic condition. The inactivation efficiency was decreased in an aerobic condition. When NZVI concentration increased to 500 and 1000 mg/L, complete inactivation was achieved under both anaerobic and aerobic condition. In general, E. coli inactivation efficiency using NZVI was strongly dependent on the contact time and the concentration of NZVI particles with its maximum efficiency at 500 mg/L within 120 min. Stabilization-NZVI by starch did not improve its bactericidal activity and the inactivation of E. coli by stabilized nanoparticles required higher concentration compared to that by nonstabilized nanoparticles. Conclusion: The present study showed that nonstabilized Fe 0 nanoparticles have higher bactericidal efficiency than that of S-NZVI. This investigation also suggests that NZVI can be used as an effective and strong agent for antimicrobial applications.

Low temperature synthesis of highly stable and reusable CMC-Fe2+(-nZVI) catalyst for the elimination of organic pollutants

Removal of organic pollutants in Fenton process using nano zero valent iron (nZVI) has certain drawbacks such as formation of sludge, difficulty in recovery/reuse of nZVI and high concentration of Fe2+/Fe3+ ions into the final effluent. The challenge is to stabilize the nZVI and control leaching of Fe2+/Fe3+ ions without compromising the primary objective of removal of organic pollutants. This study demonstrates low temperature synthesis of carboxymethyl cellulose (CMC) stabilized nZVI hybrid (CMC-Fe2+(-nZVI)). In this hybrid, Fe2+ ion present on the surface of nZVI is sandwiched between CMC and nZVI. At low temperature (∼10°C), CMC provides excellent control over the size (<7nm) of CMC-Fe2+(-nZVI). The new orientation of peaks in the UV–Vis absorbance spectra of CMC, Fe2+-CMC and CMC-Fe2+(-nZVI) further supported the formation of CMC-Fe2+(-nZVI) hybrid. Similarly, ATR-FTIR spectra of CMC and CMC-Fe2+(-nZVI) showed significant shift in the functional groups of –CO and OH and confirmed their chelation with Fe2+ central ion. Redox properties of CMC-Fe2+(-nZVI) when evaluated with cyclic voltammetry (CV) showed distinct oxidation and reduction peaks due to the formation of Fe2+ and Fe3+ ions. Furthermore, the redox properties and performance of CMC-Fe2+(-nZVI) catalyst was assessed in Fenton process using phenol as a representative pollutant. Cyclic stability of CMC-Fe2+(-nZVI) was performed at the scan rate of 60mV/s and only less than 1% reduction in stability was observed at the end of 100 cycles. The Fe2+(-nZVI) particle was effectively stabilized by CMC and only trace amount of Fe2+ was observed in solution at the end of the reaction. In addition, reuse of CMC-Fe2+(-nZVI) led to complete phenol removal and this sustained for more than 50 cycles.

Agar agar-stabilized milled zerovalent iron particles for in situ groundwater remediation

Submicron-scale milled zerovalent iron (milled ZVI) particles produced by grinding macroscopic raw materials could provide a cost-effective alternative to nanoscale zerovalent iron (nZVI) particles for in situ degradation of chlorinated aliphatic hydrocarbons in groundwater. However, the aggregation and settling of bare milled ZVI particles from suspension presents a significant obstacle to their in situ application for groundwater remediation. In our investigations we reduced the rapid aggregation and settling rate of bare milled ZVI particles from suspension by stabilization with a “green” agar agar polymer. The transport potential of stabilized milled ZVI particle suspensions in a diverse array of natural heterogeneous porous media was evaluated in a series of well-controlled laboratory column experiments. The impact of agar agar on trichloroethene (TCE) removal by milled ZVI particles was assessed in laboratory-scale batch reactors. The use of agar agar significantly enhanced the transport of milled ZVI particles in all of the investigated porous media. Reactivity tests showed that the agar agar-stabilized milled ZVI particles were reactive towards TCE, but that their reactivity was an order of magnitude less than that of bare, non-stabilized milled ZVI particles. Our results suggest that milled ZVI particles could be used as an alternative to nZVI particles as their potential for emplacement into contaminated zone, their reactivity, and expected longevity are beneficial for in situ groundwater remediation.

Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

Kinetic removal of Cr6+ by carboxymethyl cellulose-stabilized nano zerovalent iron particles

Carboxymethyl cellulose (CMC) was used in the chemical reduction method for producing dispersible nano zerovalent iron (nZVI) particles served as reactive, mobile and convenient adsorbent. CMC-stablized nZVI particles at CMC:Fe2+ = 0.0034 molar ratio were characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy assisted with probe ultrasonication dispersing tool. FTIR depicted that the CMC monomers were adsorbed onto nZVI particles primarily through carbonyl head groups via monodentate bonding. The botryoidally clusters were the predominant morphology of CMC-stablized nZVI particles under SEM observation. Those spherical particles were evenly dispersed at sizes less than 100 nm under TEM analysis. nZVI particles stabilization with CMC (at CMC:Fe2+ molar ratio of 0.0050) prevented the aggregation and resulted in high catalytic reactivity observed at pseudo-first order constant value, K1 of 0.0196 min-1 for Cr6+ removal in contaminated aqueous. This study demonstrates that CMC-stablized nZVI particles has the potential to become an effective agent for in-situ subsurface environment remediation.

NZVI injection into variably saturated soils: Field and modeling study

Nano-scale zero valent iron (nZVI) has been used at a number of contaminated sites over the last decade. At most of these sites, significant decreases in contaminant concentrations have resulted from the application of nZVI. However, limited work has been completed investigating nZVI field-scale mobility. In this study, a field test was combined with numerical modeling to examine nZVI reactivity along with transport properties in variably saturated soils. The field test consisted of 142L of carboxymethyle cellulose (CMC) stabilized monometallic nZVI synthesized onsite and injected into a variably saturated zone. Periodic groundwater samples were collected from the injection well, as well as, from two monitoring wells to analyze for chlorinated solvents and other geochemistry indicators. This study showed that CMC stabilized monometallic nZVI was able to decrease tricholorethene (TCE) concentrations in groundwater by more than 99% from the historical TCE concentrations. A three dimensional, three phase, finite difference numerical simulator, (CompSim) was used to further investigate nZVI and polymer transport at the variably saturated site. The model was able to accurately predict the field observed head data without parameter fitting. In addition, the numerical simulator estimated the mass of nZVI delivered to the saturated and unsaturated zones and distinguished the nZVI phase (i.e. aqueous or attached). The simulation results showed that the injected slurry migrated radially outward from the injection well, and therefore nZVI transport was governed by injection velocity and viscosity of the injected solution. A suite of sensitivity analyses was performed to investigate the impact of different injection scenarios (e.g. different volume and injection rate) on nZVI migration. Simulation results showed that injection of a higher nZVI volume delivered more iron particles at a given distance; however, the travel distance was not proportional to the increase in volume. Moreover, simulation results showed that using a 1D transport equation to simulate nZVI migration in the subsurface may overestimate the travel distance. This is because the 1D transport equation assumes a constant velocity while pore water velocity radially decreases from the well during injection. This study suggests that on-site synthesized nZVI particles are mobile in the subsurface and that a numerical simulator can be a valuable tool for optimal design of nZVI field applications.

Nanoscale zero-valent iron particles modified on reduced graphene oxides using a plasma technique for Cd(II) removal

Nanoscale zero-valent iron particles supported on reduced graphene oxides (NZVI/rGOs) from spent graphene oxide (GO)-bound iron ions were developed by using a plasma reduction method to improve the reactivity and stability of NZVI. The specific surface area (SSA) of NZVI/rGOs was 117.97 m2 g−1, while the SSA of NZVI particles was 59.59 m2 g−1. The adsorption kinetics was quite fast, which could be completed within 50 min. The adsorption capacity of NZVI/rGOs toward Cd(II) was 425.72 mg g−1, which was higher than other adsorbent materials. Moreover, the NZVI/rGOs could be regenerated by the plasma reduction technique and maintained high removal performance after four cycles. NZVI/rGOs also showed high removal capability toward Cd(II) in the simulated Cd(II)-bearing effluent. The above experimental results show that the NZVI/rGO can be efficient materials for the purification of Cd(II)-contaminated water in the environmental pollution management.

Impact of nanoscale zero valent iron on bacteria is growth phase dependent.

The toxic effect of nanoscale zero valent iron (nZVI) particles on bacteria from different growth phases was studied. Four bacterial strains namely Escherichia coli strains JM109 and BW25113, and Pseudomonas putida strains KT2440 and F1 were experimented. The growth curves of these strains were determined. Bacterial cells were harvested based on the predetermined time points, and exposed to nZVI. Cell viability was determined by the plate count method. Bacterial cells in lag and stationary phases showed higher resistance to nZVI for all four bacterial strains, whereas cells in exponential and decline phases were less resistant to nZVI and were rapidly inactivated when exposed to nZVI. Bacterial inactivation increased with the concentration of nZVI. Furthermore, less than 14% bacterial inactivation was observed when bacterial cells were exposed to the filtrate of nZVI suspension suggesting that the physical interaction between nZVI and cell is necessary for bacterial inactivation.

Structural Evolution of Nanoscale Zero-Valent Iron (nZVI) in Anoxic Co(2+) Solution: Interactional Performance and Mechanism.

The structures of nanoscale zero-valent iron (nZVI) particles evolving during reactions, and the reactions are influenced by the evolved structures. To understand the removal process in detail, it is important to investigate the relationships between the reactions and structural evolution. Using high resolution-transmission electron microscopy (HR-TEM), typical evolved structures (sheet coprecipitation and cavity corrosion) of nZVI in anoxic Co2+ solutions were revealed. The system pH (pH measured in mixture), which controls the stability of coprecipitation and the nZVI corrosion rate, were found to be the determining factors of structural evolutions. X-ray photoelectron spectroscopy (XPS) results indicated that the formation and dissolution of sheet structure impacts on the ratio of Fe(0) on the nZVI surface and the surface Co2+ reduction. The cavity structure provides the possibility of Co migration from the surface to the bulk of nZVI, leading to continuous removal. Subacidity conditions could accelerate the evolution and improve the removal; the results of structurally controlled reactions further indicated that the removal was suspended by the sheet structure and enhanced by cavity structure. The results and discussion in this paper revealed the “structural influence” crucial for the full and dynamical understanding of nZVI reactions.

Degradation of γ-Hexachlorocyclohexane Using Carboxymethylcellulose-Stabilized Fe/Ni Nanoparticles

Carboxymethylcellulose (CMC)-stabilized and Ni-doped nanoscale zero valent iron (nZVI) particles (CMC-Fe/Ni) were synthesized to remove γ-hexachlorocyclohexane (γ-HCH) in aqueous solution. Fourier transform infrared spectroscopy results suggested that the CMC molecules were adsorbed onto iron primarily through carboxylate groups by monodentate complexation, and hydroxyl groups were also involved in the interactions between CMC and iron. The adsorbed CMC made the zeta potential of Fe/Ni nanoparticles more negative. At reaction pH of 8.3, the absolute value of zeta potential of the CMC-Fe/Ni was almost twice that of the bare one. The stability of colloidal nanoparticles was greatly enhanced as initial CMC concentration increased from 0 to 0.1 % (w/w) and did not increase further with higher CMC doses. Batch studies showed that 99.9 % of 10 mg/L γ-HCH was removed after 4 h at a mono nZVI loading level of 0.1 g/L, while the γ-HCH could be completely removed in 5 min using CMC-Fe/Ni, which exhibited a 13 times greater k obs as compared to that using bare Fe/Ni. Within 20 h, 60 mg/L γ-HCH was totally removed through 6 cycles of consecutive treatment using CMC-Fe/Ni. GC-MS analysis showed that 3,4,5,6-tetrachlorocyclohexene was the main intermediate and chlorobenzene was the final product when using mono nZVI. When treating by Fe/Ni nanoparticles, 1,2,3,4,5-pentachlorocyclohexene, 3,4,5,6-tetrachlorocyclohexene, and 1,4-dichlorobenzene were formed as intermediates and benzene and chlorobenzene as the final products. Possible degradation pathways were proposed based on the identified intermediates, and dehydrochlorination, dichloroelimination, and hydrogenolysis were involved in dechlorination.

Photoelectrochemistry of Nano Zerovalent Fe Based CdFe2O4 / FexOy Produced from Cd2+ Water Remediation

Iron nanoparticles are a new generation of materials for environmental remediation. Various metallic ions including Pb2+, Cr6+, Ni2+, As3+, As5+, Cd2+, Cu2+, Zn2+ and Ba2+ had been fixated from water using this new technology.1 Nanoscale zero-valent iron (nZVI) had been studied as an alternative for decontamination processes. In nZVI reaction, metallic iron is oxidized in presence of water. During this reaction, other metal ions can be removed from the aqueous media by chemical absorption.4 In this process, iron oxides such as hematite (α-Fe2O3) are produced.5 This α-Fe2O3 have been broadly study for catalytic applications due to its highly active photochemical properties and resistance to corrosion, but the excited electrons have a short lifetime and the charge mobility is low.6 Approaches such as doping with other metals and changing the structural arrangement of the system had been employed to overcome α-Fe2O3 challenges regarding to the electron transfer processes. Previous studies from our group proves that the incorporation of cadmium (Cd) ions in the oxidized nZVI produce a changes in the structure of the system associated to iron oxides species (FexOy) and cadmium ferrite (CdFe2O4) formation. This can be done without using high temperatures to complete the preparation of the material, a common practice in the literature. Additional to these changes, cadmium species have been also studied for their photochemical applications. Regardless of all this information, there are few reports, which employ these particles as photocatalysts. nZVI particles were used in Cd2+ remediation as a proof of concept for further use at the Las Cucharillas Marsh. Our group had done experiments in Cd2+ concentrations between 1 and 6ppm. This led us to explore the effect of higher Cd2+ concentration on the nZVI. Moreover, an alternative use of the remediation nZVI product was evaluated. This led to its possible use in photoelectrochemical cells. A challenge in this device is to optimize the quantum conversion efficiency, which is affected by the electron transfer processes in the system. We used the CdFe2O4 / FexOy produced from nZVI in a photoelectrochemical cell to further understand their properties. The Cd concentration employed is similar to contaminated area with this heavy metal at Las Cucharillas Marsh, Cataño, Puerto Rico. The soil in this region is mainly acidic, i.e. between pH 2 and 5. Soil analysis, using ICP following the EPA 6010B method; have shown Cd2+ concentrations between 1 and 33ppm (mg/kg) in different regions of the marsh. The nZVI have been treated in different Cd2+ solution between 1 and 30 ppm, based on the concentrations found in the Las Cucharillas Marsh. The nZVI treated in a Cd2+ 30ppm solution were evaluated as anode materials for photoelectrochemical cells. This materials was characterized by different techniques such as XPS, XRD, electron microscopy, FT-IR, UV-Vis, cyclic voltammetry, and electrochemical impedance spectroscopy.