Fe0 Particles Research Articles

Carbothermally synthesized, lignin biochar-based, embedded and surface deposited nano zero-valent iron composites: Comparative material characterization, selective gas adsorption and nitroaromatics remediation

Biochar (BC) with nanoscale zero valent iron (nZVI) incorporation offers advantageous materials for water purification. Even though the most common approach for nZVI incorporation is the deposition on the carrier surface, embedding in the support matrix has also been reported. However, the behavior of the embedded material in contaminant removal has not been adequately studied while characteristics and the remediation capabilities of the two materials have not been compared. Present study focuses on preparing and extensively characterizing two materials: nZVI embedded in (Lig-e-nZVI) and surface deposited on (Lig-s-nZVI) lignin BC with subsequent comparative study of remedial action for two nitroaromatics, p-nitroaniline (pNA) and p-nitrophenol (pNP). The synthesis of Lig-e-nZVI and Lig-s-nZVI involved simultaneous and subsequent pyrolysis of lignin and carbothermal reduction of the iron salt, respectively. Lig-e-nZVI showed enhanced porosity. XRD confirmed the formation of Fe0. HR-TEM images proved the core-shell structure of nZVI, and an interlayer spacing of 0.36nm of the shell verified that the Fe0 particles are encapsulated with graphene while an iron carbide inner layer was also observed, thinner in Lig-e-nZVI and thicker in Lig-s-nZVI. Band gap energy of 2.54eV suggested a photocatalytic activity of both materials. Best fitted Sips isotherms showed 23.1 and 13.1mgg-1 capacities for Lig-s-nZVI in pNP and pNA adsorption respectively. Highest stability was portrayed by Lig-e-nZVI over 4 regeneration cycles. The physicochemical features of the developed materials further enable selective gas adsorption. Findings provide new insights into physicochemical characteristics and remedial actions of differently synthesized nZVI-BC composites.

Pyrolytic conversion of nylon-6 and red mud into N-doped carbon composite and its application into azo-dye degradation

The continuous growth of the global population and industries has led to the mass generation of plastic and industrial waste, posing significant environmental challenges due to their incompatibility with conventional waste management practices. This study investigates the thermochemical conversion of plastic (nylon-6) and industrial waste (red mud) into value-added products, presenting a waste-to-resource conversion strategy. Nylon-6 and red mud were co-pyrolyzed, resulting in a metal-carbon composite characterized as porous N-doped graphitic carbon with embedded Fe0 particles. Application of the composite to an amaranth solution demonstrated its ability to activate persulfate, facilitating amaranth oxidation at a rate (kobs = 1.78 min−1) significantly higher than other Fe-based catalysts. Quenching experiments verified the generation of OH· and SO4·- radicals during activation, with the latter playing a dominant role in amaranth degradation. The composite exhibited robust reusability, maintaining an amaranth removal efficiency of >80 % after five reaction cycles. Additionally, red mud significantly enhanced syngas (H2 and CO) generation from nylon-6, suggesting a catalytic effect. In conclusion, the proposed thermochemical approach offers a viable method for converting waste materials into valuable products, including environmental catalysts and gas fuels.

Facilely tuning the coating layers of Fe nanoparticles from iron carbide to iron nitride for different performance in Fenton-like reactions

In this study, a series of Fe-based materials are facilely synthesized using MIL-88A and melamine as precursors. Changing the mass ratio of melamine and MIL-88A could tune the coating layers of generated zero-valent iron (Fe0) particles from Fe3C to Fe3N facilely. Compared to Fe/Fe3N@NC sample, Fe/Fe3C@NC exhibits better catalytic activity and stability to degrade carbamazepine (CBZ) with peroxymonosulfate (PMS) as oxidant. Free radical quenching tests, open-circuit potential (OCP) test and electron paramagnetic resonance spectra (EPR) prove that hydroxyl radicals (OH) and superoxide radical (O2−) are dominant reactive oxygen species (ROSs) with Fe/Fe3C@NC sample. For Fe/Fe3N@NC sample, the main ROSs are changed into sulfate radicals (SO4−) and high valent iron-oxo (Fe (IV)=O) species. In addition, the better conductivity of Fe3C is beneficial for the electron transfer from Fe0 to the Fe3C, thus could keep the activity of the surface sites and obtain better stability. DFT calculation reveals the better adsorption and activation ability of Fe3C than Fe3N. Moreover, PMS can also be adsorbed on the Fe sites of Fe3N with shorter FeO bonds and longer SO bonds than on Fe3C, the Fe (IV)=O is thus present in the Fe/Fe3N@NC/PMS system. This study provides a novel strategy for the development of highly active Fe-based materials for Fenton-like reactions and thus could promote their real application.

Approach enhancing nitrate removal from actual municipal wastewater by integrating electric-magnetic field with Fe0 in UMSR reactor

This study aimed to investigate the effectiveness of combining zero-valent iron (Fe0) with an electric-magnetic field (EMF) with an intensity of 48-mT generated by an alternating current (AC) of 6 V and 50 Hz applied deep within a reactor using actual wastewater obtained from a secondary stage of a wastewater treatment plant (WWTP). The lab-scale experiment was conducted using the UMSR reactor, maintaining a controlled temperature of 25 ± 2 °C and a hydraulic retention time (HRT) of 5-hour, with a dissolved oxygen (DO) level below 1.5 mg/L. Fine Fe0 particles with a size of ≤ 0.3 µm were added into the reactor at a concentration of 3 g/L. The actual wastewater had an approximate nitrate nitrogen (NO3–-N) concentration of 30 ± 2 mg/L, and the substrate mass ratio of carbon to nitrogen (C:N) was at 1:1. The results examined the performance of the EMF-Fe0 system in terms of nitrate removal efficiency and the enrichment of denitrifying bacteria, achieving a nitrate removal rate of 67 % with an effluent NO3–-N concentration of 10 mg/L and a chemical oxygen demand (COD) concentration of 11.8 mg/L at removal rate of 60 %. Illumina sequencing revealed various enriched denitrifying bacteria after coupling EMF with Fe0, including autotrophic Nitrospira (NOB) at 4 %, denitrification bacteria like Hydrogenophaga at 1.3 %, Hyphomicrobium at 1 %, and Sphingobium at 5 %, along with thermophilic bacteria Thermus at 1.1 % and Meiothermus at 3.5 %. PICRUSt predicted bacterial functions and analyzed interactions, while KEGG and GO analyses linked nitrogen removal pathways to specific species, genes, and enzymes in the EMF-Fe0 system.

Ingenious use of autocatalytic hydrodeoxygenation for the separation and recovery of oil and iron from rolling oil sludge

This paper introduces a transformative hydrodeoxygenation process for the simultaneous recovery of oil and iron from hazardous rolling oil sludge (ROS). Leveraging the inherent catalytic capabilities of iron/iron oxide nanoparticles in the sludge, our process enables the conversion of fatty acids and esters into hydrocarbons under conditions of 4.5 MPa, 330 °C, and 500 rpm. This reaction triggers nanoparticle aggregation and subsequent separation from the oil phase, allowing for effective resource recovery. In contrast to conventional techniques, this method achieves a high recovery rate of 98.3% while dramatically reducing chemical reagent consumption. The reclaimed petroleum and iron—ready for high-value applications—are worth 3910 RMB/ton. Moreover, the process facilitates the retrieval of nanoscale magnetic Fe and Fe0 particles, and the oil, with an impressive hydrocarbon content of 87.8%, can be further refined. This energy-efficient approach offers a greener, more sustainable pathway for ROS valorization.

Synthesis of Iron-Carbon (Fe<sup>0</sup>-C) Nanocomposite and its Use for the Removal of Rhodamine-B and Hexavalent Chromium from Aqueous Solutions

Contamination of water resources by industrial effluents consisting of organic (e.g., dyes) and inorganic (e.g., heavy metals) pollutants is a significant environmental challenge. Treatment techniques that can efficiently target multiple co-contaminants are critically needed to achieve both performance and cost efficiency. In this study we employed a novel approach to synthesize a nanocomposite material consisting of a zerovalent iron (Fe0) core and a carbon shell (C), and investigated its ability to simultaneously remove toxic hexavalent chromium (Cr (VI)) and rhodamine B dye (RhB) in batch aqueous solutions. Advanced characterization techniques revealed the uniform distribution of carbon on Fe0 particles in the size range of 60-85 nm. The batch removal experiments showed a Cr (VI) removal of 50% and RhB removal reached 93% in mixed matrix systems. The removal capacity increased from 16 to 33 mg/g for Cr (VI) and from 2.4 to 5.5 mg/g for RhB when the particles were tested in a mixed matrix compared to those in individual contaminant systems. Removal of contaminants was achieved most likely due to the combined adsorptive and reductive properties of the nanocomposite. Overall, the study demonstrated the strong potential of Fe0-C nanocomposite particles in targeting and treating both organic and inorganic contaminants. Results from this study may be useful in developing and optimizing nanocomposite materials for the removal of multiple contaminants in complex aqueous matrices.

Exsolution versus particle segregation on (Ni,Co)-doped and undoped SrTi0.3Fe0.7O3-δ perovskites: Differences and influence of the reduction path on the final system nanostructure

Exsolution is one of the most successful functionalization techniques to improve the catalytic activity of electrodes in solid oxide fuel and electrolyzer cells (SOFC/SOEC). The objective of this technique is to produce the highest possible number of metallic nanoparticles on the surface of a host-oxide, without significantly altering its structure. In this work, we compare three similar SOFC electrodes: STF (SrTi0.3Fe0.7O3), STFN (Sr0.93Ti0.3Fe0.63Ni0.07O3), and STFNC (Sr0.93Ti0.3Fe0.56Ni0.07Co0.07O3), revealing that there is a significant difference between Ni–Fe/Ni–Co–Fe nanoparticle formation in STFN/STFNC and pure Fe0 particle formation in STF, which is evidenced by the size and amount of produced nanoparticles, but also by their anchoring to the host-oxide. The terms exsolution and particle segregation will be used, respectively, to distinguish these phenomena. Next, we explore two different reduction methods and observe that the characteristics of exsolution do not only depend on temperature, atmosphere and reduction times, but also on the reduction path taken to reach such conditions.

Oxygen-Vacancy-Rich Fe@Fe3O4 Boosting Fenton Chemistry

Iron-based materials are widely applied in Fenton chemistry, and they have promising prospects in the processing of wastewater. The composition complexity and rich chemistry of iron and/or oxides, however, hamper the precise understanding of the active sites and the working mechanism, which still remain highly controversial. Herein, iron oxides of four different model systems are designed through a conventional precipitation method plus H2 reduction treatment. These systems feature Fe@Fe3O4 with abundant oxygen vacancy, Fe0 and Fe3O4 particles with interface structures, and Fe3O4-dominated nanoparticles of different sizes. These materials are applied in the decomposition of methyl orange as a model reaction to assess the Fenton chemistry. The Fe@Fe3O4 with core–shell structures exhibits significantly higher decomposition activity than the other Fe3O4-rich nanoparticles. A thin Fe3O4 layer formed by auto-oxidation of iron particles when exposed to air can boost the activity as compared with the Fe0 and Fe3O4 particles with interface structures but poor oxygen vacancy. The unique hetero-structure with the co-existence of both metallic iron and oxygen vacancy displays excellent redox propensity, which might account for the superior Fenton activity. This finding provides a new perspective to understand and design highly efficient iron-based Fenton catalysts.

Advanced Oxidation Processes Coupled to Nanofiltration Membranes with Catalytic Fe0 Nanoparticles in Symmetric and Asymmetric Polyelectrolyte Multilayers.

The in situ synthesis of Fe0 particles using poly-(acrylic acid) (PAA) is an effective tool for fabricating catalytic membranes relevant to advanced oxidation processes (AOPs). Through their synthesis in polyelectrolyte multilayer-based nanofiltration membranes, it becomes possible to reject and degrade organic micropollutants simultaneously. In this work, we compare two approaches, where Fe0 nanoparticles are synthesized in or on symmetric multilayers and asymmetric multilayers. For the membrane with symmetric multilayers (4.0 bilayers of poly (diallyldimethylammonium chloride) (PDADMAC)/PAA), the in situ synthesized Fe0 increased its permeability from 1.77 L/m2/h/bar to 17.67 L/m2/h/bar when three Fe2+ binding/reducing cycles were conducted. Likely, the low chemical stability of this polyelectrolyte multilayer allows it to become damaged through the relatively harsh synthesis. However, when the in situ synthesis of Fe0 was performed on top of asymmetric multilayers, which consist of 7.0 bilayers of the very chemically stable combination of PDADMAC and poly(styrene sulfonate) (PSS), coated with PDADMAC/PAA multilayers, the negative effect of the Fe0 in situ synthesized can be mitigated, and the permeability only increased from 1.96 L/m2/h/bar to 2.38 L/m2/h/bar with three Fe2+ binding/reducing cycles. The obtained membranes with asymmetric polyelectrolyte multilayers exhibited an excellent naproxen treatment efficiency, with over 80% naproxen rejection on the permeate side and 25% naproxen removal on the feed solution side after 1 h. This work demonstrates the potential of especially asymmetric polyelectrolyte multilayers to be effectively combined with AOPs for the treatment of micropollutants (MPs).

Vapor-deposited digenite in Chang’e-5 lunar soil

Frequent impacts on the Moon have changed the physical and chemical properties of the lunar regolith, with new materials deposited from the impact-induced vapor phase. Here, we combined nanoscale chemical and structural analysis to identify the mineral digenite (4Cu2S·CuS) in Chang’e-5 lunar soil. This is the first report of digenite in a lunar sample. The surface-correlated digenite phase is undifferentiated in distribution and compositionally distinct from its hosts, suggesting that it originated from vapor-phase deposition. The presence of an Al-rich impact glass bead suggests that a thermal effect provided by impact ejecta is the main heat source for the evaporation of Cu-S components from a cupriferous troilite precursor, and the digenite condensed from these Cu-S vapors. A large pure metallic iron (Fe0) particle and high Cu content within the studied Cu-Fe-S grain suggest that this grain was most likely derived from a highly differentiated and reduced melt.

Quantifying the effects of submicroscopic metallic iron on VIS–NIR spectra of lunar soils

Metallic iron (Fe0) particles with sizes ranging from a few nanometers to the submicroscopic scale and formed by space weathering are specific components of lunar soil. Previous studies have suggested that the iron significantly alters the optical properties of lunar soil. For example, nanophase metallic iron (npFe0) causes both reddening and darkening of the lunar soil spectrum, and submicroscopic metallic iron (SMFe) only causes darkening. Here, we prepared SMFe particles with an average size of ∼180 nm embedded within melt glasses through carbothermal reduction experiments to analogize agglutinated glasses in the lunar soil. We evaluated the effect of SMFe content on visible and near-infrared (VIS–NIR) reflectance spectra of these lunar soil samples simulants. The spectral data show that SMFe content plays a key role in the optical properties of samples, including the average reflectance in the VIS-NIR range (400–2150 nm), and the absorption depth at ∼2 μm. A small amount (0.05 wt%) of SMFe mainly causes significant spectral darkening, and the average reflectance is reduced by 50% when the SMFe content rises to 0.36 wt%. Both the average reflectance and the absorption depth at ∼2 μm show a negative correlation with the SMFe content. We developed a quantitative model relating the spectral characteristics and the SMFe abundance based on experimental results. Thus, the SMFe contents play a key role in altering spectral characteristics of airless bodies during remote sensing spectroscopic detection.

Mature lunar soils from Fe-rich and young mare basalts in the Chang’e-5 regolith samples

Space weathering on airless bodies produces metallic iron (Fe0) particles in the rims of mineral grains, which affect visible and near-infrared spectra and complicate the identification of surface materials. The Chang’e-5 mission provides an opportunity to couple information gained from its returned samples with in situ observations and orbital monitoring to gain insight on the details of space weathering on extremely Fe-rich basalts. By putting together all these data, we could extract a soil maturity index (Is/FeO) at the Chang’e-5 landing site of ~66 ± 3.2, indicative of a formation age for the Xu Guangqi crater, whose ejecta dominate the site, of 240–300 Myr ago. In addition, abundant large Fe0 particles were found in the sample, indicating that both the inherited Fe0 particles from late-stage mare basalts and the dense clustering of oversaturated Fe0 in extremely FeO-rich (>17 wt%) basalts contribute to observed Fe0 abundances. We suggest that space weathering of Fe-richer basalt generates Fe0 particles with a larger grain size and faster production rate.

Effect of Fe0 particle size on buffering characteristics and biohydrogen production in high-load photo fermentation system of corn stover

The aim of this work was to study the effects of Fe0 particle sizes (700 nm, 100 nm and 50 nm) addition on biohydrogen production, liquid culture characteristics and photosynthetic bacterial respond in the high-load photo fermentation system of corn stover within the concentration range of 200–1500 mg/L. Results showed that Fe0 with particle size of 700 nm had a better promotion effect on hydrogen production than 100 nm and 50 nm. The highest hydrogen yield of 74.32 ± 3.48 mL/g TS and hydrogen production rate of 3.31 ± 0.11 mL/g·h TS corn stover were obtained at 1000 and 1500 mg/L Fe0-700 nm, which were significantly increased by 92.88 % and 133.88 % compared with the control group. Further analysis indicated that Fe0 addition effectively alleviated pH drop, enhanced nitrogenase activity, promoted cell growth, and accelerated the consumption of acetic acid and butyric acid.

Treatment of refractory organics in biologically treated landfill leachate by a zero valent iron enhanced Peroxone process: Degradation efficiency and mechanism study.

A zero valent iron (ZVI) enhanced Peroxone process (ZVI/Peroxone) was used to treat biologically treated landfill leachate (BTL). The treatment efficiency of the ZVI/Peroxone process was compared to single (ZVI, O3 and H2O2) and dual (ZVI/H2O2, Fe0/O3 and Peroxone) processes. The results showed that ZVI can greatly enhance the treatment capability of the Peroxone process, and the color number (CN), absorbance at 254 nm (UV254), and total organic carbon (TOC) removal efficiencies were 98.82, 84.30 and 66.38%, respectively. In the ZVI/Peroxone process, higher O3 and ZVI dosages improved organics removal, and H2O2 could promote organics removal within a certain dosage range. However, too much H2O2 decreased treatment efficiency. The best treatment performance by the ZVI/Peroxone process was obtained under acidic conditions. The three-dimensional excitation and emission matrix analysis showed that BTL mainly contained two fluorescent substances, which were fulvic-like substances in the ultraviolet region (Ex/Em = 235-255 nm/410-450 nm) and fulvic-like substances in the visible light region (Ex/Em = 310-360 nm/370-450 nm). Fluorescent substances could be substantially degraded by the ZVI/Peroxone process during the early stages of the reaction. An analysis of ZVI morphology and element valency changes showed that the micro Fe0 particles used in this study remained highly reactive during the process. The ZVI enhanced the homogenous Fenton, heterogeneous Fenton, and coagulation-flocculation effects during the Peroxone process.

Surface and Defect Chemistry of Porous La0.6Sr0.4FeO3−δ Electrodes on Polarized Three-Electrode Cells

Even though solid oxide fuel/electrolysis cells (SOFC/SOEC) are already commercially available, the effect of electrochemical polarization on the electrochemical properties and overpotentials of individual electrodes is largely unexplored. This is partly due to difficulties in separating anode and cathode impedance features and overpotentials of operating fuel cells. For this, we present a novel three-electrode geometry to measure single-electrode impedance spectra and overpotentials in solid oxide cells. With this new design, we characterise polarised porous La0.6Sr0.4FeO3−δ (LSF) electrodes by simultaneous impedance spectroscopy and ambient pressure XPS measurements. With physically justified equivalent circuit models, we can show how the overpotential-dependent changes in the impedance and XPS spectra are related to oxygen vacancy and electronic point defect concentrations, which deterimine the electrochemical properties. The results are overall in very good agreement with the key findings of several previous studies on the bulk defect chemistry and surface chemistry of LSF. They show for example the exsolution of Fe0 particles during cathodic polarisation in H2 + H2O atmosphere that decrease the polarization resistance by roughly one order of magnitude.

Efficient adsorption and reduction of Cr(VI) from aqueous solution by Santa Barbara Amorphous-15 (SBA-15) supported Fe/Ni bimetallic nanoparticles

Nanoscale zero-valent iron (nZVI or Fe0) can rapidly reduce Cr(VI) contaminants in the water environment, but the agglomeration and passivation of the Fe0 system have adverse effects on its application. In this study, a novel mesoporous Santa Barbara Amorphous-15 supported Fe/Ni bimetallic composite (SBA-15@Fe/Ni) is proposed to remove Cr(VI). The proposed material can enhance the stability and removal capacity of the nZVI system. The results show that the unique six-way through-hole structure of SBA-15 provides a place for the dispersion of Fe0 particles. Meanwhile, SBA-15 effectively alleviates the accumulation of Fe0 particles. The removal efficiency of SBA-15@Fe/Ni is better than two single systems (SBA-15 and Fe/Ni). The removal efficiency of SBA-15@Fe/Ni towards Cr(VI) can reach 97.62% after 60 min at pH 4.0. SBA-15@Fe/Ni still maintains excellent performance in the presence of various competitive ions (Cl-, SO42-, CO32–, NO3–). At 298 K, the maximum removal capacity of SBA-15@Fe/Ni towards Cr(VI) is 180.99 mg/g. The possible removal process of SBA-15@Fe/Ni towards Cr(VI) is divided into the following steps: First, Cr(VI) is attracted into the vicinity of the SBA-15@Fe/Ni channel by the electrostatic attraction; Second, the reduction of Cr(VI) occurs after contacting with the Fe/Ni system, and its driving force mainly comes from nZVI and Fe(II); Furthermore, the introduction of Ni can promote Cr(VI) reduction through electron transfer and catalytic hydrogenation. In conclusion, adopting SBA-15@Fe/Ni to treat chromium contamination is an effective and promising approach.

Role of reactor type on Cr(VI) removal by zero-valent iron in the presence of pyrite: Batch versus sequential batch reactors

This study was conducted to understand the role of application sequence of pyrite and zero-valent iron (Fe0) (simultaneous vs. sequential) on chromium (VI) removal by Fe0. In batch experiments, pyrite and Fe0 were homogeneously mixed in batch reactors maintained at a constant total solids loading of 2 g L−1. In sequential batch experiments, however, the first reactor containing variable doses of pyrite was operated for 20 min, and the liquid fraction from the first reactor was then subsequently loaded into the second reactor containing a fixed Fe0 dose of 1.2 g L−1. The batch reactors achieved much higher Cr(VI) removal efficiency than sequential batch reactors under similar operating conditions due to discrepancies in Fe redox cycling activities between these two systems. In batch reactors, the Fe0 particles deposited on pyrite surface due to electrostatic attraction between negatively charged pyrite and positively charged Fe0, thus, rendering the overall solids surface charge neutral at optimum pyrite and Fe0 doses. As a result, the whole system behaved like a composite material, with pyrite functioning as a support material for Fe0. This stimulated Fe redox cycling more effectively to generate new Fe(II) sites on Fe0 for enhanced Cr(VI) removal relative to Fe0 only system. In sequential batch reactors, however, the Fe redox cycling activity was limited, but significantly increased with increasing pyrite dose in the first reactor. Overall, our results indicate that the stimulatory effect of pyrite on Cr(VI) removal by Fe0 may be much higher if the reactors are operated in batch mode.

Influencing factors for the preparation of Fe0 in lunar soil simulant using high-temperature carbothermic reduction

Metallic iron (Fe0) within lunar soil grains can affect their visual and near-infrared spectra, adhesion, biological toxicity, and electrostatic migration characteristics. The Fe0 particle therefore is an important component of lunar soil. This study devised a high-temperature carbothermic reduction method for preparing Fe0 via graphite reduction of Chinese Lunar Regolith Simulant (CLRS-2) in an argon atmosphere, which is similar to the Fe0 in the agglutinitic glass of lunar samples. The X-ray diffraction and electron microscopy data show that the mixture of lunar soil simulants and graphite heated at high temperature rapidly quenched to form a glassy phase with dispersed Fe0 particles, the microstructure of which is consistent with the α-Fe (bcc) in lunar soil. This paper also discusses the main influencing factors for preparing Fe0, such as the ratio of raw materials, heating temperature, and holding time. The optimal experimental conditions are a graphite-to-CLRS-2 mass ratio of 1.0: 27.0 (Fe/C = 2.0: 2.6), reduction temperature of ∼1600 °C, and holding time of ∼4 h, which produce single-phase α-Fe with an average particle size of ∼180 ± 10 nm and no residual impurities (e.g., graphite).

Degradation of diclofenac via sequential reduction-oxidation by Ru/Fe modified biocathode dual-chamber bioelectrochemical system: Performance, pathways and degradation mechanisms

A sequential reduction-oxidation for DCF degradation was proposed by alternating anaerobic/aerobic conditions at Ru/Fe-biocathode in a dual-chamber bioelectrochemical system (BES). Results showed that Ru/Fe-electrode was successfully fabricated by in-situ electro-deposition, which was rough and uniformly distributed with Ru0 and Fe0 particles. The morphologic changing and biocompatibility were favorable to increase the surface area and enhance microbial adhesion on Ru/Fe-electrode. At an applied voltage of 0.6 V, the potential and impedance of Ru/Fe-biocathode were −0.80 V and 26 Ω, respectively, lower than that of carbon-felt-biocathode. It led to a higher DCF degradation efficiency of 93.2% under anaerobic conditions, which was superior to that of 88.0% under aerobic conditions. Using NaHCO3 as carbon source, DCF removal efficiency increased with increasing applied voltage, but decreased with increasing initial DCF concentration. Thirteen intermediates were measured, and two degradation pathways were proposed, among which sequential reduction-oxidation of DCF was the main pathway, dechlorination intermediates were first generated by [H] attacked under anaerobic conditions, further oxidized by microbes and OH attacked under aerobic conditions, achieving 69.6% of mineralization. After 4 d of reaction, microcystis aeruginosa growth inhibition rate decreased from 22.9 to 8.0%, signifying a significant reduction in biotoxicity. Bacteria (e.g. Nitrobacter, Nitrosomonas, Pseudofulvimonas, Aquamicrobium, Sulfurvermis, Lentimicrobiaceae, Anaerobineaceae, Bacteroidales, Hydrogenedensaceae, Dethiosulfatibacter and Azoarcus) for DCF degradation were enriched in Ru/Fe-biocathode. Microbes in Ru/Fe-biocathode had established defense mechanisms to acclimate to the unfriendly environment, while Ru/Fe-biocathode possessed higher nitrification and denitrification activities than carbon-felt-biocathode, and Ru/Fe-biocathode might be of aerobic and anaerobic biodegradation activities. DCF could be mineralized by the synergistic reaction between Ru/Fe and bacteria under sequential anaerobic/aerobic conditions.

Using nano-scale Fe0 particles and organic waste to improve the nutritional status of tree seedlings growing in heavy metal-contaminated soil

The rehabilitation of heavy metal-contaminated lands is a challenging issue worldwide. The application of effective eco-friendly techniques and materials is necessary for amending the contaminated soils, and the in-situ results should be examined. The present study investigated the effect of zero-valent iron-nanoparticles (Fe0-NPs) and cellulosic wastes (CW) on the lead (Pb) and cadmium (Cd) uptake and nutrients’ (N, P, K) concentration of maple seedlings in contaminated soil. First, one-year-old seedlings were planted in pots containing unpolluted soil (volume = 3 Kg), and then the soil was contaminated by adding Pb (0, Pb100, Pb200, and Pb300 mg kg-1) and Cd (0, Cd10, Cd20, and Cd30 mg kg-1) solutions. The CW (0, 10, 20, 30 g/100g soil) and Fe0-NPs (0, 1, 2, 3 mg kg-1) treatments were applied to the soil before and after Pb and Cd addition, respectively. The biomass of seedlings and the concentration of nitrogen, potassium, and phosphorus in leaves were measured. Leaves, stems, and roots were digested to measure the Pb and Cd concentrations. Results showed that CW and Fe0-NPs improved N, P, and K concentrations in leaves at all levels of contamination. The lowest concentration of Pb and Cd in all organs and treatments was observed in the highest level of Fe0-NPs. The cellulosic waste and Fe0-NPs (the highest level only) significantly increased the soil pH at all levels of contamination. Our findings suggested that the use of Fe0-NPs (3 mg kg-1) and CW (30g/100g soil) could be appropriate for reducing the bioavailability of Pb and Cd in contaminated soil and improving the growth of maple seedlings.