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The reactivity of iron atoms, clusters, and nanoparticles (nZVI) is of increasing interest owing to their important practical applications, ranging from the steel industry to water remediation technologies. Here, we provide an overview of computational methods and models that can be applied to study nanoscale zero-valent iron (nZVI) reactions and discuss their benefits and limitations. We also report current progress in calculations through recent examples treating the reactivity of nZVI particles. Finally, we consider the potential use of highly accurate methods with favorable scaling (such as quantum Monte Carlo or random phase approximation), which are currently considered too computationally expensive but are expected to become more amenable in the future as computer power increases. © 2014 The Authors International Journal of Quantum Chemistry Published by Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Highlights: [•] Comparisons of reusability, stability and dissolved iron in solution of four nanoparticles. [•] The modified nZVI can be effectively used for BDE209 removal. [•] SiO2@FeOOH@Fe particles displayed better reusability and stability. [Copyright &y& Elsevier]

[Display omitted] • Facile procedures were proposed to prepare nZVI entrapped in the matrix of CDP. • The nZVI efficiently removes PNP in water by degradation and adsorption. • The nZVI performs well under pH 3.0–10 conditions. • The nZVI performs well against the interferences of water constituents. • The nZVI display stability and long-term performance in groundwater. Nano zero-valent iron (nZVI) materials usually have low selectivity in water toward target contaminants (e.g., p -nitrophenol) and nontarget water constituents (e.g., nitrates and dissolved organic matter-DOM). Here we prepared the selective nZVI entrapped in the matrix of cyclodextrin polymer (CDP), using in situ impregnation and aqueous KBH 4 reduction of FeCl 3 in the matrix of CDP. The nZVI-CDP composites feature the network structure of CDP with mainly 40–80 nm nZVI particles entrapped in the network and 300 nm iron particles coated on the network surface. nZVI entrapped displays high stability and selective CDP facilitates the access of p -nitrophenol to nZVI, both accounting for the high selectivity of the composites. Chemical degradation of the nZVI materials, combined with adsorption, contributed to the p -nitrophenol removal. The nZVI materials usually exhibited similar or higher p -nitrophenol removal at different levels of nitrates, DOM or sulfides. Column experiments showed that the nZVI materials completely decontaminated 63 column volumes of groundwater containing p -nitrophenol, 6-fold higher than mixed nZVI and CDP. The nZVI materials were estimated to have potential performance duration of averaging 109 d, indicating the long-term performance in groundwater. [ABSTRACT FROM AUTHOR]

Antibiotic fermentation residue (AFR) has been categorized as hazardous waste in China. Anaerobic biohydrogen fermentation may be a promising technology for handling AFR, which could achieve dual goals of waste treatment and clean energy production at the same time. However, the low hydrogen yield and low removal efficiency of residual antibiotics are two major factors limiting the AFR biohydrogen fermentation process. This work firstly applied gamma radiation (50 kGy) to remove the residual antibiotic in AFR and improve the bioavailability of organic matters, then adding nano zero-valent iron (nZVI) (100–1000 mg/L) to further enhance the AFR biohydrogen fermentation performance. Results showed that residual deacetoxycephalosporin C in AFR was removed with a high efficiency of 98.6%, and hydrogen yield achieved 20.45 mL/g-VS added with the combined approach of gamma radiation pretreatment and 500 mg/L nZVI addition, which was 139.2% higher compared to the control experimental result. The combined approach also promoted the biohydrogen production rate, decreased the lag phase of hydrogen production, and increased the organics utilization. Microbiological analysis revealed that highly efficient hydrogen-producing genera Clostridium sensu stricto were enriched in much higher abundance with the combined approach, which might be the fundamental mechanism for the enhanced AFR fermentation performance. [Display omitted] • Radiation removed 98.6% of antibiotics in antibiotic fermentation residue (AFR). • Radiation combined with nano-Fe0 was developed to enhance H 2 fermentation of AFR. • The combined approach improved H 2 yield by 139.2%, reaching 20.45 mL/g-VS added. • The combined approach created a more effective metabolic pathway for H 2 production. • The combined approach enriched more H 2 -producing bacteria, especially Clostridium. [ABSTRACT FROM AUTHOR]

Periodate (PI)-based advanced oxidation processes have recently received increasing attentions. Herein, PI was readily activated by nano zero-valent iron (nZVI) and subsequently led to the enhanced oxidation of organic contaminants, with the removal performance of sulfadiazine (SDZ) in the nZVI/PI process even higher than that in the nZVI/peroxydisulfate process under identical conditions. Kinetic experiments indicated that the decay of SDZ was susceptible to the dosage of nZVI and PI, but was barely affected by pH values (4.0–7.0) under buffered conditions, suggesting the promising performance of the nZVI/PI process in a relatively wide pH range. Selective degradation of contaminants and 18O-isotope labeling assays collectively demonstrated that iodate radical (•IO 3), high-valent iron-oxo species (Fe(IV)) and hydroxyl radical (•OH) were responsible for the abatement of organic contaminants. More importantly, due to the relatively weak steric hindrance effect of PI, PI easily adsorbed on the surface of nZVI and no iron leaching was detected throughout the reaction, implying that PI activation induced by nZVI was a surface-mediated process. Besides, PI was not transformed into harmful reactive iodine species. This study proposed an environmental-friendly approach for PI activation and shed new lights on the PI-based processes. [Display omitted] • nZVI efficiently activates periodate to degrade organic contaminants. • IO 3 , Fe(IV) and •OH collectively contribute to the oxidation of contaminants. • nZVI activates periodate through a surface-mediated pathway. • Nontoxic iodate was generated instead of harmful reactive iodine species. [ABSTRACT FROM AUTHOR]

Sodium dodecyl sulfate stable nanoscale zero-valent iron (SDS-nZVI) was synthesized by the sodium borohydride reduction method, characterized with SEM and XRD. SDS-nZVI was used for the removal of Cr (VI) from aqueous solutions at different conditions in a batch process. XRD analysis indicated the presence of iron oxide and iron-chromium hydroxide coprecipitation on the surface of SDS-nZVI after reaction some time. The reaction kinetics, mechanism, isotherms, and thermodynamics for Cr (VI) removal of aqueous solution via SDS-nZVI were investigated. The pseudo-second-order model was relatively suitable for describing the reaction process. Intraparticle diffusion model was used to analysis the mechanism, the results indicated that there were two processes (bulk diffusion and surface diffusion) controlling the reaction rate, while only one was rate limiting in any particular time range. The fitted Temkin and D-R model satisfactorily explanted the experimental data in the range of 303–343 K. The maximum removal capacity of SDS-nZVI for Cr (VI) was obtained for 336.7 mg g−1at 303 K. The overall removal process was endothermic. These results demonstrated that SDS-nZVI could potentially be used as an effective material for environmental remediation. [ABSTRACT FROM PUBLISHER]

Abstract: To decrease aggregation and enhance the mobility of nano zero-valent iron (NZVI) used for in-situ groundwater remediation, the surface of such NZVI must be modified using organic stabilizers, which can provide electrostatic repulsion, and steric or electrosteric stabilization. However, the stability of the nanoparticles can also be affected by groundwater components such as cations and humic acid (HA). In this study, the effect of Ca2+ on the colloidal stability of NZVI coated with three types of stabilizers (i.e., polyacrylic acid (PAA), Tween-20 and starch) was evaluated in the absence or presence of HA. Differing stability behavior was observed for different surface-modified NZVIs. The presence of Ca2+ exerted a slight influence on the settling of NZVI modified with PAA or Tween-20, in the absence or presence of HA. However, the presence of Ca2+ caused significant aggregation and sedimentation for starch-modified NZVI in the absence of HA, and induced an even higher degree of aggregation and sedimentation in the presence of HA. It is presumed that, in the absence of HA, starch-modified NZVI particles undergo attachment with each other via Ca2+ complexation with the coated starch molecules on the surface of the particles, thus enhancing the aggregation and the following sedimentation of starch-modified NZVI. However, in the presence of HA, spectroscopic analysis of the starch-modified NZVI aggregates indicated that the bridging interaction of HA with Ca2+ was the predominant mechanism for the enhanced aggregation. [Copyright &y& Elsevier]

Abstract: To enhance colloidal stability of nano zero-valent iron (NZVI) used for groundwater remediation, the surfaces of such NZVI can be modified via coating with organic stabilizers. These surface stabilizers can electrostatically, sterically, or electrosterically stabilize NZVI suspensions in water, but their efficacy is affected by the presence of humic acid (HA) in groundwater. In this study, the effect of HA on the colloidal stability of NZVI coated with three types of stabilizers (i.e., polyacrylic acid (PAA), Tween-20 and starch) was evaluated. Differing stability behaviors were observed for different surface-modified NZVIs (SM-NZVI) in the presence of HA. Fluorescence spectroscopic analysis probed the possible interactions at the SM-NZVI-HA interface, providing a better understanding of the effect of HA on SM-NZVI stability. The adsorption of HA on the surface of PAA-modified NZVI via complexation with NZVI (rather than the PAA stabilizer) enhanced the electrosteric repulsion effect, increasing the stability of the particles. However, for NZVI modified with Tween-20 or starch, HA could interact with the surface stabilizer and apparently play a “bridge” role among the particles, which might induce aggregation of the particles. Therefore, the stability behavior of NZVI modified with Tween-20 or starch might have resulted from the combined effect of “bridging” and “electrosteric” exerted by HA. [Copyright &y& Elsevier]

Abstract: Nano zero-valent iron (NZVI) offers a promising approach for arsenic remediation, but the spent NZVI with elevated arsenic content could arouse safety concerns. This study investigated the fate of As(V)-treated NZVI (As-NZVI), by examining the desorption potential of As under varying conditions. The desorption kinetics of As from As-NZVI as induced by phosphate was well described by a biphasic rate model. The effects of As(V)/NZVI mass ratio, pH, and aging time on arsenic desorption from As-NZVI by phosphate were investigated. Less arsenic desorption was observed at lower pH or higher As(V)/NZVI mass ratio, where stronger complexes (bidentate) formed between As(V) and NZVI corrosion products as indicated by FTIR analysis. Compared with the fresh As-NZVI, the amount of phosphate-extractable As significantly decreased in As-NZVI aged for 30 or 60 days. The results of the sequential extraction experiments demonstrated that a larger fraction of As was sorbed in the crystalline phases after aging, making it less susceptible to phosphate displacement. However, at pH 9, a slightly higher proportion of phosphate-extractable As was observed in the 60-day sample than in the 30-day sample. XPS results revealed the transformation of As(V) to more easily desorbed As(III) during aging and a higher As(III)/As(V) ratio in the 60-day sample at pH 9, which might have resulted in the higher desorption. [Copyright &y& Elsevier]

Abstract: Heavy metal removal using nano zero-valent iron (NZVI) has drawn growing attention due to the ease of application and high removal efficiency. However, uncertainties regarding its fate and transport in subsurface environments have raised concerns that require further exploration. In this study, aggregation, sedimentation, and Cr/As desorption of three types of NZVIs were investigated under various conditions. It was found that the aggregation behavior of the NZVIs differed from one another in regard to reaction time and ionic strength, associated with the respective critical size for sedimentation. Sedimentation of NZVIs was positively related to the concentrations and average particle sizes. The sedimentation kinetics of NZVI followed two concomitant processes, i.e., (1) direct sedimentation of larger particles, and (2) initial aggregation and then sedimentation of smaller particles. When loaded with Cr/As, NZVIs tended to deposit faster, possibly due to the precipitation of Cr/As onto the nanoparticle surfaces resulting in larger particle sizes. Moreover, desorption of Cr/As from Cr/As loaded NZVIs was detected in the presence of typical groundwater ions, as well as natural organic matter, and poses a potential risk to the subsurface environment. The desorption of Cr was linearly related to the release of iron ions, while As desorption was mitigated when the immobilization of Cr increased. [Copyright &y& Elsevier]

Abstract: The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO2@FeOOH@Fe). The characteristics of SiO2@FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy, and Brunnaer–Emmett–Teller surface area analysis. The mean particle size of the reactive mesoporous silica microspheres was 450nm, and its specific surface area was 383.477m2 g−1. The degradation of dcabromodiphenyl ether (BDE209) was followed pseudo-first-order kinetics, and the observed reaction rate constant could be improved by increasing the SiO2@FeOOH@Fe dosage and by decreasing the initial BDE209 concentration. The stability and longevity of the immobilized Fe nanoparticles were evaluated by repeatedly renewing the BDE209 solution in the reactor. The stable degradation of BDE209 by SiO2@FeOOH@Fe was observed within 10 cycles. Agglomeration-resistance and magnetic separation of SiO2@FeOOH@Fe were also performed. The improved dispersion of SiO2@FeOOH@Fe in solution after one-month storage and its good performance in magnetic separation indicated that SiO2@FeOOH@Fe has the potential to be efficiently applied to environmental remediation. [Copyright &y& Elsevier]

Abstract: Due to the increasing levels of polybrominated diphenyl ethers (PBDEs) in the environment and their persistent toxicity, methods of removing PBDEs from the environment have become a necessary. Nanoscale zero-valent metallic particles (S-NZVI) were prepared from steel pickling waste liquor by chemical deposition and used to remove BDE209 in a water/tetrahydrofuran (4/6, v/v) solution. Nanoscale zero-valent iron particles (NZVI), nanoscale zero-valent and Ni/Fe particles were also prepared. These particles were characterized by BET, TEM, SEM, XRD, and EDS. The crystalline structure of S-NZVI was different from NZVI. However, the BET surface area of S-NZVI was the same as that of NZVI. The degradation rate of BDE209 by S-NZVI followed a pseudo-first order kinetics. The removal efficiency increased with increasing metal dosage but decreased with increasing initial BDE209 concentration. High reaction rate was observed at more water content solvent, indicating that hydrogen ion was the driving force of reaction. Comparing different nanoscale Fe-based materials, the removal of BDE209 by S-NZVI was found more effective than NZVI. By evaluating the cost and the significance of reclaimable iron resource, S-NZVI was found to give better compensation compared to other metals. Thus, the degradation of BDE209 by S-NZVI is both feasible and efficient. [Copyright &y& Elsevier]

Abstract: In this study, a synthesized cation exchange resin supported nano zero-valent iron (NZVI) complex forming NZVI–resin was proposed for the decoloration of an azo dye Acid Blue 113 (AB 113), taking into account reaction time, initial dye concentration, NZVI dose and pH. From results, the successful decoloration of the AB 113 solution was observed using a NZVI–resin. Increasing the iron load to 50.8mgg−1, the removal efficiencies of the AB 113 concentration increased exponentially. With an initial dye concentration of 100mgl−1 and nano iron load of 50.8mgg−1, the best removal efficiencies were obtained at 100 and 12.6% for dye concentration and total organic carbon, respectively. Color removal efficiency was dependent on initial dye concentration and iron load. Moreover, the removal rates followed modified pseudo-first order kinetic equations with respect to dye concentration. Thus, the observed removal rate constants (k) were 0.137–0.756min−1 by NZVI loads of 4.9–50.8mgg−1. Consequently, the NZVI–resin performed effectively for the decoloration of AB 113 azo dye, offering great potential in the application of NZVI–resins in larger scale column tests and further field processes. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the fixation of aqueous Ni2+ ions by nanoparticles of zero-valent iron (nZVI) prepared using the borohydride reduction method. The uptake of Ni2+ was tested under various experimental conditions like initial concentration, time, pH, and repetitive application of nZVI. Part of the experiments was devoted to comparing the extent of uptake of Ni2+ ions with those of Cu2+, Cd2+, Zn2+, and Sr2+ ions, which belong to a wide range of standard reduction potentials. Particle size analysis of nZVI in aqueous solution indicated that the material suffered extensive aggregation, much above the extent of aggregation known for dry nZVI. Nevertheless, nZVI showed fast uptake kinetics and very high uptake capacity. The overall results demonstrated the high fixation capability of nZVI towards the studied transition metal ions in aqueous solution. The same conclusion is, however, not valid for the removal of Sr2+ ions. [Copyright &y& Elsevier]

In this paper, the effects of several groundwater components (heavy metals, inorganic anions, and organics) on the cytotoxicity of nanoscale zero-valent iron (NZVI) towards Escherichia coli (E. coli) under aerobic/anaerobic conditions were studied. The results showed that NZVI exhibited much higher toxicity in anaerobic conditions than aerobic conditions. Under the state of air-saturation, corrosion of NZVI occurred rapidly, at the same time, it could stably and continuously generate Fe (Ⅱ) and trigger reactive oxygen species (ROS), which led to oxidative stress in E. coli. While in the deareated state, the TEM images showed that the integrity of the cell membrane was destroyed, which validated that the main mechanism of NZVI cytotoxicity was the rapid membrane damage of E. coli. The presence of Cr (Ⅵ) reduced the toxicity of NZVI through oxidation-reduction with NZVI, especially under anaerobic conditions. In contrast, the presence of Cd (Ⅱ) could be adsorbed onto NZVI to increase the cytotoxicity of NZVI. The presence of phosphate and humic acid greatly improved the survival rate of E. coli through the complex reaction with Fe (Ⅱ), especially under aerobic conditions. On the one hand, the formed Fe (II)-phosphate/humic acid complex could reduce the production of ROS. On the other hand, the complex accumulated on the outer surface of E. coli cells could provide steric hindrance to impede the contact between NZVI and cell. These findings were crucial for practical significance to evaluate environmental risk during the groundwater remediation process by using NZVI. [Display omitted] • NZVI exhibited much higher toxicity in anaerobic conditions than aerobic conditions. • Mechanisms of cell inactivation were different under aerobic/anaerobic conditions. • Cr(VI) reduced the toxicity of NZVI, while Cd(II) increased the toxicity of NZVI. • Phosphate and HA alleviated the toxicity of NZVI through complexation with Fe(II). • Each component showed different influence under aerobic/anaerobic conditions. [ABSTRACT FROM AUTHOR]

In this study, the biochar (BC) supported Fe–Cu bimetallic stabilized by PVP (Fe–Cu/PVP/BC) were prepared and utilized to enhance the nitrate (NO 3 −) removal and the selectivity toward nitrogen (N 2). Results showed the optimum Fe:Cu:BC ratio and the dosage of the BC (pyrolysis at 700 °C) supported Fe–Cu bimetallic stabilized by polyvinylpyrrolidone (PVP) (Fe–Cu/PVP/BC 700) were respectively 1:2:3 and 1 mg L−1 with the selectivity toward N 2 of 31 %. This was mainly due to the synergy among Fe0, Cu0 and BC in the Fe–Cu/PVP/BC. The addition of Fe0 could reduce the NO 3 − through providing electron. The Cu0 and BC improved the selectivity of NO 3 − to N 2 through forming [Cu–NO 2 − ads ] and adjusting redox potential. The addition of Fe–Cu/PVP/BC could supply electrons for denitrification and enhance the relative abundances of Azospira and Thauera related to denitrification to improve NO 3 − removal. This result was further confirmed by the variations of denitrifying functional genes (narG , nirK , nirS and nosZ). This research provided an effective method to improve NO 3 − removal during surface water treatment in constructed wetlands (CWs) by adding Fe–Cu/PVP/BC. [Display omitted] • A new type of nanocomposite Fe–Cu/PVP/BC was prepared. • The 31 % N 2 selectivity was observed at 1 mg L−1 Fe–Cu/PVP/BC with Fe:Cu:BC of 1:2:3. • Fe–Cu/PVP/BC showed excellent removal efficiency on NO 3 −, TN and TP. • Fe–Cu/PVP/BC had a positive effect on microorganisms and functional genes in CWs. [ABSTRACT FROM AUTHOR]

Oil palm fronds (OPFs) are generally cast off as solid waste, which comprise of unused valuable product, fermentable sugars that can be utilised for biohydrogen generation. The OPF juice consisting of mainly glucose, sucrose, xylose, and fructose (TC = 51.53g/L) was utilised as a substrate for biohydrogen production using local strain, Clostridium butyricum JKT37 in batch anaerobic fermentation. The aim of this research was to optimise the initial pH and total carbohydrate (TC) concentration with the addition of nano zero-valent iron (nZVI) in OPF juice for enhanced biohydrogen yield (HY) and production rate (HPR). The optimal parameters obtained in this study were a pH of 6.5, 12.8 g/L TC, and 50 mg/L nZVI, which resulted in an optimum HY, HPR, and TC utilisation of 2.71 mol H 2 /mol sugar, 88.75 mL H2 /L OPF h−1, and 88.28%, respectively. The optimised condition showed a 1.85-fold increase in hydrogen productivity as compared to the control (raw unadjusted OPF juice TC). The predominant acidogenic by-products were butyric, acetic, lactic, and formic acid. Although lactic acid is one of the major constituents of volatile fatty acids (VFAs), hydrogen production was feasible with the optimum level of factors. The HY and HPR improved by 45.39% and 85.20%, respectively, compared to fermentation of raw OPF juice. nZVI nanoparticle was used in this study as a catalyst in dark fermentation to improve biohydrogen production and accelerate the fermentation process. This study demonstrated that nZVI nanoparticle could effectively shorten the lag time and facilitated the hydrolysis and utilisation of OPFs. [Display omitted] • Biohydrogen was produced via mesophilic fermentation by Clostridium butyricum JKT37. • Optimum parameters were pH of 6.5, TC of 12.8g/L and nZVI concentration of 50mg/L. • 50 mg/L nZVI increases 46% of biohydrogen yield than positive control without nZVI. • Maximum biohydrogen yield of 2.71 mol H 2 /mol sugar obtained at optimum condition. [ABSTRACT FROM AUTHOR]

The use of nanoparticles in fertilisation has confirmed positive effects on plant growth and yield. Simultaneously, there is still little research into the effects of nanoparticles on the antioxidant system of plants. Due to the positive effect of nano zinc oxide on plants and the special property of nano zero-valent iron, these particles were selected for the research. The nano zero-valent iron is crucial for plants as it is present in agglomerations on the surface of roots where it increases the absorptive surface of the rhizosphere and causes elongation of the roots. The study aims to determine the influence of selected nanoparticles as a potential improvement for conventional fertilisation by magnesium (Mg), calcium (Ca), phosphorus (P) and nitrogen (N). After the cultivation, the influence of nanoparticles on the accumulation of macronutrients in plant tissues, biometric parameters, and physiological response (chlorophyll and antioxidant system) of radish (Raphanus sativus) were assessed. The solution used in this study helped to increase the content of nitrates (V) in radish roots by 31.7–73.2% compared to conventional fertilisation. Nevertheless, nanoparticles supplementation resulted in a decrease in the concentrations of magnesium, iron (Fe) and zinc (Zn) in plants. The high dose of used fertilisers increased the thickness and length of tubers by approximately 50.0%, compared to the control samples. The "Macro 2 + nano" variant caused an increase of plant biomass up to 70.0%. The analysis of the antioxidant system showed that the application of macronutrients with nanoparticles increased the concentration of polyphenols in plant tubers by 46.0–55.6%. Interestingly, while implemented conditions caused a 1.5-fold increase in CAT activity in leaves, at the same time the decrease in CAT activity in plant roots was observed. Based on the obtained results of the enzymatic antioxidant system and biometric parameters of plants, it can be concluded that (in laboratory conditions) nZVI and nanoZnO are efficient components of fertilisers. However, the effects on other organisms must be investigated before implementing a method for widespread use. [ABSTRACT FROM AUTHOR]

Abiotic and biotic remediation of chlorinated ethenes (CEs) in groundwater from a real contaminated site was studied using biochar-based composites containing nanoscale zero-valent iron (nZVI/BC) and natural resident microbes/specific CE degraders supported by a whey addition. The material represented by the biochar matrix decorated by isolated iron nanoparticles or their aggregates, along with the added whey, was capable of a stepwise dechlorination of CEs. The tested materials (nZVI/BC and BC) were able to decrease the original TCE concentration by 99% in 30 days. Nevertheless, regarding the transformation products, it was clear that biotic as well as abiotic transformation mechanisms were involved in the transformation process when nonchlorinated volatiles (i.e., methane, ethane, ethene, and acetylene) were detected after the application of nZVI/BC and nZVI/BC with whey. The whey addition caused a massive increase in bacterial biomass in the groundwater samples (monitored by 16S rRNA sequencing and qPCR) that corresponded with the transformation of trichloro- and dichloro-CEs, and this process was accompanied by the formation of less chlorinated products. Moreover, the biostimulation step also eliminated the adverse effect caused by nZVI/BC (decrease in microbial biomass after nZVI/BC addition). The nZVI/BC material or its aging products, and probably together with vinyl chloride-respiring bacteria, were able to continue the further reductive dechlorination of dichlorinated CEs into nonhalogenated volatiles. Overall, the results of the present study demonstrate the potential, feasibility, and environmental safety of this nanobioremediation approach. [Display omitted] • Novel nano iron-biochar composite (nZVI/BC) was tested to remediate contaminated groundwater. • NZVI/BC followed by biostimulation transformed chlorinated ethenes (CEs). • CEs were dechlorinated into less toxic nonhalogenated volatiles. • 16S rRNA sequencing revealed development of an organohalide-respiring community. • Living bacterial biofilm was detected on nZVI/BC using fluorescence microscopy. [ABSTRACT FROM AUTHOR]

Nano zerovalent iron (nZVI) is one of the most broadly applied nanomaterials in the fields of groundwater remediation which benefits from its high reactivity for pollutants. However, its successful application faces challenges due to its tendency to agglomerate or form passive (oxy)hydroxide corrosion. With the emerging microplastics (MPs) pollution in groundwater system in recent years and considerable data vacancy on its potential physicochemical and ecological effects, it complicates the situation for groundwater remediation. Hereby, we investigated the effects on metal removal by nZVI in groundwater in the presence of various MPs. The removal capacity of Cu (II), Cr (VI), Pb (II) and Zn (II) by nZVI was found to be inhibited to different degrees in the presence of MPs. Desorption of metallic ions was observed dependent on various metal species, with the highest desorption rate in Zn (II). Amongst all MPs investigated, including polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC), PVC poses the most adverse impact on metal desorption, attributing to its promotion of nZVI aging through electrostatic attraction. This study focused on the impact of MPs to metal remediation, beyond the general aspect of MPs hazard such as its toxic effects or delivery of contaminants. Moreover, groundwater was investigated to make a useful supplement to the research of MPs which primarily focuses on surface water. [Display omitted] • Microplastics (MPs) pose aging effects to nZVI for groundwater remediation. • Effects of MPs on the nZVI's efficiencies are metal specific. • PVC poses the most adverse effects ascribed to its passivation effects on nZVI. [ABSTRACT FROM AUTHOR]

Soils containing a large proportion of industrial waste can pose a health risk due to high environmentally available concentrations of toxic metal(loid)s. Nano zero-valent iron (nZVI) and amorphous manganese oxide (AMO) were applied as immobilising amendments (1 wt%) to soils with different industrial origin of As and Sb, and leaching of As, Sb, Pb, and Zn was investigated using a single extraction with deionised water. The different industrial impact was reflected in the mineralogy, chemical composition and pH of these soils. Water-soluble As ratios positively correlated with pH in all experimental treatments. A significant decrease of water-soluble As ratios was observed in all nZVI-amended soils (~65–93% of the control) except for one sample with the lowest solution pH. Nano zero-valent iron was also successful in Sb immobilisation (~76–90% of the control). Highly variable results were obtained for AMO, which only led to a decrease of water-soluble As in soils with solution pH of ≥7 (~70–80% of the control), probably due to lower stability of AMO in acidic conditions. In each case, nZVI was more efficient at decreasing water-soluble As ratios than AMO. Dissolved Pb concentrations remained unchanged after the application of nZVI and AMO, and the decrease of Zn leaching using AMO was controlled mainly by soil pH increase induced by its application. According to the calculated saturation indices, tripuhyite (FeSbO 4) was predicted to be the key mineral controlling Sb solubility in mine soils. Secondary Fe (hydr)oxides either originally present or newly formed due to nZVI oxidation were instrumentally identified at different stages of their transformation and metal(loid) retention. To conclude, nZVI is suitable for application to contaminated soils at a wide pH range, while the use of AMO for decreasing As leaching is limited to soils with pH ≥ 7. [Display omitted] • Soil natural pH affects the stability or functionality of immobilising agents. • Leaching of As significantly decreased in nZVI-treated soil in a wide range of pH. • Nano zero-valent iron as a perspective amendment for Sb immobilisation in soils. • Amorphous Mn oxide efficiently immobilised As at pH > 7. • Mineralogical investigations revealed different stages of nZVI transformation. Nano zero-valent iron application and iron oxidation products proved to be efficient for immobilising As, Sb and Zn in contaminated soils. [ABSTRACT FROM AUTHOR]

• nZVI promoted the removal efficiency of the anammox reactor. • Addition of nZVI improved the AnAOB abundance from 42.1% to 52.5%. • nZVI increased the c-di-GMP synthesized protein from 148 rpmr to 252 rpmr. • nZVI decreased the c-di-GMP degradation protein from 238 rpmr to 204 rpmr. • Enrichment of c-di-GMP is beneficial to the formation of sludge particles. The addition of nano zero-valent iron (nZVI) has been proven to improve the efficiency of the anammox process, however, the mechnism is not clear. Here, the effect of nZVI on anammox microbial community was studied by metagenomic sequencing methods. It was found that 50 mg/L nZVI indeed promoted the removal of NH 4 + and NO 2 − of the anammox reactor and significantly improved the relative abundance of AnAOB (Ca. Brocadia) from 42.1% to 52.5%. What's more, 50 mg/L nZVI increased the abundance of c-di-GMP synthesized protein from 148 rpmr to 252 rpmr in the microbial community and decreased the abundance of c-di-GMP degradation protein from 238 rpmr to 204 rpmr, which indirectly led to the enrichment of c-di-GMP in the microbial community. The enrichment of c-di-GMP reduced the motility of microorganisms in the reactor and promoted the secretion of extracellular polymers by bacteria, which is beneficial to the formation of sludge particles in the anammox reactor. In conclusion, this research clarified the mechanism of nZVI promoting the anammox process and provided theoretical guidance for the engineering application of anammox. [Display omitted] [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (Fe0) has been widely used to remove Uranium (U(VI)). In order to enhance the performance of Fe0 toward U(VI) removal, the Fe0 was assembled into graphene oxide (GO) sheets via 3-aminopropyl triethoxysilane (APTES) as Fe0/APTES-GO composites. The Fe0/APTES-GO composites were triumphantly prepared, characterized and analyzed by means of Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) together with Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). SEM and TEM-EDS results manifested that Fe0 particles were encapsulated into rolled-up GO, which greatly improved the stability of Fe0. Batch experiment showed that only a small amount of Fe2+ was leached in the first two leaching cycles of Fe0/APTES-GO composites. The removal capacity of Fe0/APTES-GO composites was up to 1357.99 mg/g at pH = 4.1 and T = 50 °C, which was mainly attributed to the reducing activity of Fe0 and an abundance of functional groups (i.e., –COOH, C–OH and –OH) on the Fe0/APTES-GO composites. The electrostatic potential (ESP) from the calculation also supported that U(VI) tended to be reduced at the back side of the GO-Fe0 cluster. [Display omitted] • Maximum removal capacity of Fe0/APTES-GO for U(VI) reaches 1357.99 mg/g. • Main removal mechanism of Fe0/APTES-GO is the reduction of U(VI) to U(IV). • Fe0/APTES-GO composites have excellent recycling effect and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • nZVI enhanced CH 4 yield of sludge in an anaerobic continuous stirred tank reactor. • nZVI promoted CH 4 bioconversion by serving as trace element and electron donors. • Organics-degrading bacteria and hydrogenotrophic methanogens were enriched. • Subsequent digested sludge dewaterability were enhanced at nZVI 160 mg/g-TS. Underlying mechanism of continuous nano zero-valent iron (nZVI) supply in functional microbes enrichment and methane bioconversion of waste activated sludge were investigated in a lab-scale continuous stirred tank reactor (CSTR). Results indicated that methane productivity strongly relied on nZVI dosage (R = 0.998, p (0.05) < 0.001) and leached Fe2+ concentration (R = 0.943, p (0.05) = 0.005). The higher nZVI dosage, the higher methane productivity and organic removal were achieved. The methane production rate reached 77.6 ± 9.7 mL/g-VS/d at 160 mg-nZVI/g-TS, increasing by 2.3 times than the phase without nZVI supply. The corrosion/dissociation of nZVI, except for serving as trace element and electron donors (H 2 /[H]), increased system buffering capacity (2835–3410 mg CaCO 3 /L), and decreased oxidation reduction potential from − 152 mV to − 240 mV. Such thermodynamically favorable environment facilitated the proliferation of organics-degrading bacteria (Firmicutes , Chloroflexi , Smithella , etc.) and hydrogenotrophic methanogen (Methanobacterium). As a result, more large organic molecules such as proteins and polysaccharides were hydrolyzed into short-chain fatty acids, thus enhancing the methanogenesis. Furthermore, the continuous supply of nZVI regulated the colloidal properties of sludge flocs by altering particle size distribution and zeta potential via flocculation effect of the released Fe2+ (136.4 ± 12.1 mg/L). The dewaterability of digested sludge was improved to a certain extent, with capillary suction time dropping to 84.8 ± 4.1 s. This study provided a more systematic understanding of the role of nZVI in promoting methane bioconversion and subsequent digested sludge dewatering and volume reduction, thus expanding the potential application of nZVI in real-world scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] • The caproate concentration can be improved by 100% when 5 g/L NZVI was added. • NZVI addition can increase ethanol utilization, reduce butyrate and butanol. • NZVI can provide extra electron donor and prevent pH to fall below 5.4. • Oscillibacter Marseille-P3260 was found to be the key chain elongator with NZVI. Chain elongation produce medium chain carboxylates, which are important precursors to many pharmaceuticals, antimicrobials and biofuels. Results in the presented investigations show that the supply of nano zero-valent iron (NZVI) can enhance caproate production. The highest caproate concentration achieved amounted to 27.2 mmol/L when 5 g/L NZVI were added, which was about 100% higher than the control. The study also showed increase of ethanol oxidation and decrease of butyrate and butanol with NZVI addition. Mechanism study showed NZVI can stimulate caproate production by preventing pH to fall below 5.4 through displacement reaction. Electron balance analysis displayed that NZVI provides extra electron by promoting ethanol oxidation and its dissolution. H 2 was the potential electron shuttle between NZVI and chain elongators; High throughput sequencing showed function of NZVI on reshaping of microbial communities, especially enriching Oscillibacter Marseille-P3260 , a kind of chain elongator and Corynebacterium which possesses fatty acid biosynthesis and iron utilization. [ABSTRACT FROM AUTHOR]

Prolonged exposure to inorganic arsenic (As) via drinking water is a major concern as it poses significant human health risks. Removal of As is crucial but requires effective and environment-friendly clean-up technology to avoid any additional risk to the environment. In this study, we developed Australian smectite (smec)-supported nano zero-valent iron (nZVI) composite for arsenate i.e., As(V) sorption. We used a range of tools, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and energy dispersion X-ray (EDS) spectroscopy to characterise the material. SEM and TEM images and elemental mapping of the composite reflect that the smectite layer was surrounded by a chain of iron nanobeads evenly distributed on clay particles, which is quite exceptional among currently available nZVIs. The maximum As(V) sorption capacity of this composite was 23.12 mg/g in the ambient conditions. Using X-ray photoelectron spectroscopy we unveiled chemical states of As and Fe before and after the sorption process. Additionally, the release of iron nanoparticles from the composite at various pHs (3−10) were found negligible, which demonstrates the effectiveness of smec-nZVI to remove As(V) from contaminated water without posing any secondary pollutant. ga1 • Novel smectite-supported nZVI composite was synthesised for arsenate removal. • TEM reveals nano iron-bead chain linking multiple clay layers together. • XPS analysis shows that Fe0 peak is prominent in nZVI and composite samples. • Removal efficacy of arsenate is relatively greater at acidic conditions. [ABSTRACT FROM AUTHOR]

In this paper, the polyaniline/attapulgite composite supported nano zero-valent iron (nZVI/PANI/ APT) composites were synthesized by one-step oxidation using Fe3+ as oxidant and iron source. nZVI/PANI/APT was used as a catalyst to activate persulfate (Ps) for the simultaneous removal of Cr(VI) and orange G6 (OG6) from aqueous solutions. The main factors (different composite materials, pH value, Ps concentration, etc.) affecting the removal performance of Cr(VI) and OG6 were evaluated as well. The experimental results revealed that the nZVI/PANI/APT composites can effectively remove Cr(VI) and OG6 simultaneously at a relatively low Ps concentration, the removal efficiencies of Cr(VI) and OG6 were 99.7% and 99.4% after 60 min, respectively. PANI/APT as the supporter matrix could decrease the aggregation of nZVI and increase its reactivity. A good synergistic effect between Cr(VI) reduction and OG6 oxidation was achieved by nZVI/PANI/APT combined Ps system. nZVI not only can be as a reductant for removal Cr(VI) and OG6 but also play as a catalyst to activate Ps and generate radicals for the degradation OG6. The presence of persulfate could not significantly decline nZVI reactivity for Cr(VI) reduction but remarkably promote OG6 oxidation. Moreover, kinetic and thermodynamic analyses were used to study the removal process, and the possible removal mechanism of Cr(VI) and OG6 was discussed by using the UV-Vis spectrum and liquid chromatography-mass spectrometry techniques. The nZVI/PANI/APT-persulfate heterogeneous Fenton system combines the nZVI reduction with the Fenton-like oxidation, which can be used for the treatment of industrial wastewater containing heavy metal ions and organic dyes. [ABSTRACT FROM AUTHOR]

Carboxylate chain elongation is a burgeoning research area for producing added value bio-products from organic fraction of municipal solid waste. Effect of nano zero-valent iron (NZVI) on chain elongation and its possible mechanism was investigated. Highest caproate concentration, 28.0 mmol·L−1 was achieved with 2 g·L−1 NZVI amendment, which is about 16.7% higher than the control. Promoted ethanol utilization was considered as the main reason for the increment of caproate production and hydrogen generation. Electron balance analysis shows that NZVI did not improve the total electron recovery efficiency but favoured the electron flow toward longer carboxylate chain product, i.e. caproate. Finally, full-length 16s rRNA sequencing of bacterial community showed NZVI reshaped the bacterial community by exerting reduction selectivity. And Oscillibacter and Clostridium could be the potential functional species for carboxylate chain elongation. Unlabelled Image • Nano zero-valent iron showed enhancement on chain elongation. • 2 g/L NZVI addition showed highest caproate concentration. • NZVI amendment enhanced electron transfer to high molecule carboxylate. • Oscillibacter & Clostridium are potential functional species for chain elongation. [ABSTRACT FROM AUTHOR]

Azo dyes and Chlorinated Organic Compounds (COCs) like trichloroethylene (TCE) are environmental contaminants found in textile industry effluents and groundwater sites respectively. Both compounds are carcinogenic to humans and hazardous to the environments they contaminate and are difficult to treat by conventional wastewater processes. In this study, electrocatalytically active nanocomposite membranes were fabricated and evaluated for their ability to remove azo dyes. Nano zero-valent iron (nZVI) particles were grown and stabilized within a network of dispersed single and double-walled carbon nanotubes (SW/DWCNTs), and this mixture was filtered onto the surface of a microfiltration polyethersulfone (PES) support membrane to form a porous, conductive, reactive surface nanocomposite. These catalytic surface nanocomposites were tested as a cathode alongside a graphite anode with -2 V applied for their ability to remove methyl orange (MO) dye in both a batch system and a continuous dead-end filtration system. In a well-mixed batch, it was found that complete removal of 0.25 mM MO (7.5 mMoles in 30 mL) by the charged membranes occurred within 2–3 h of operation. The performance of these nZVI-SW/DWCNT cathodes alongside controls suggests that the application of an applied current regenerates the spent reactivity of the embedded iron nanoparticles. Systems using nZVI-SW/DWCNT membranes achieved ~ 87 mol % removal of methyl orange and demonstrated a 2.7 times greater removal rate than batch tests of analogous parameters, and 1.6 times greater than other continuous tests using membrane surface composites that lacked nZVI. Furthermore, the application of voltage to the membrane thin film surface composite increases the transmembrane flux through system, allowing for increased throughput at a given feed pressure. The results of these experiments show promise in the continuous removal of contaminants from wastewaters through reductive degradation, such as azo dyes and chlorinated organic compounds. Continuous regeneration of nZVI reactivity on a membrane surface offers substantial advantages over single-use approaches for the treatment of azo dyes and COCs in solution. Image 1 • Nano zero-valent iron (nZVI) particles were grown on single and double-walled CNTs. • Electrocatalytic MF membranes were formed from nZVI-CNT composites. • Electrocatalytic MF membranes remove methyl orange. • Electrically conductive MF membranes electrochemically reduce organic compounds. • nZVI are regenerated by applied potential to continuously reduce organic compounds. [ABSTRACT FROM AUTHOR]

The present study aimed to develop a multifunctional nanoparticle platform with properties that are beneficial in imaging, targeting, and synergistic cancer phototherapy. To this end, we synthesized novel nanoparticles composed of polydopamine, nano zero-valent iron (nZVI), and reduced graphene oxide (rGO). We immobilized nZVI on the surface of GO (nZVI/GO), then further modified nZVI/GO with dopamine to form polydopamine-conjugated nZVI/rGO (nZVI/rGO@pDA). Because nZVI/rGO@pDA absorbs near infrared radiation (NIR) and binds biomolecules of cancer cells, this platform is highly efficacious in photothermal and photodynamic cancer therapy and enables specific targeting of breast cancer cells. Use of nZVI/rGO@pDA at a low concentration (10 μg/mL) resulted in irreversible damage to MCF-7 cells under NIR irradiation (808 nm) without inducing cytotoxic effects in normal cells. Furthermore, nZVI/rGO@pDA showed high sensitivity in magnetic resonance imaging (MRI), comparable to nZVI@pDA, even at low concentration. Monitoring the treatment response through evaluation of MRI signal intensity of nZVI/rGO@pDA in phototherapeutic therapy revealed that the novel material combines the advantages of nZVI, rGO, and pDA to provide specific targeting capabilities, excellent biocompatibility, and cancer phototherapeutic and tumor imaging abilities. Thus, this platform offers great potential in terms of imaging and therapeutic effects in phototherapy treatment for breast cancer. [ABSTRACT FROM AUTHOR]

The extracellular polymeric substances coating magnetic powders-supported nano zero-valent iron (nZVI@EPS@Fe 3 O 4) was synthesized, using reduction and adsorption to treat Sb(V) wastewater. The adsorption performance and mechanism were investigated under aerobic and anaerobic conditions. The adsorption capacity of nZVI@EPS@Fe 3 O 4 (79.56 mg/g at pH = 5) was improved compared to that of the original materials (60.74 mg/g). The spectral analysis shows that both nZVI and EPS@Fe 3 O 4 in nZVI@EPS@Fe 3 O 4 played an important role in reducing Sb(V) to Sb(III) and adsorbing Sb. The reducibility and adsorption capacity of nZVI@EPS@Fe 3 O 4 towards Sb(V) remained strong under aerobic condition (62% Sb(III), 79.56 mg/g), although they were slightly weaker than those under anaerobic condition (74% Sb(III), 91.78 mg/g). nZVI@EPS@Fe 3 O 4 showed good performance in regeneration experiments. nZVI@EPS@Fe 3 O 4 is promising as a cost-effective and highly efficient material for Sb(V)-contaminated water. This study is meaningful in understanding the redox behaviour of nZVI composites in aerobic and anaerobic conditions. • nZVI@EPS@Fe 3 O 4 improved Sb adsorption capacity compared to original materials. • Reducibility/adsorbability were compared under aerobic/anaerobic conditions. • Sb(V) reducibility/adsorbability remained strong under aerobic condition. • Functional groups on magnetic EPS were also responsible for Sb(V) reduction. • nZVI@EPS@Fe 3 O 4 showed great recycling performance. [ABSTRACT FROM AUTHOR]

Paddy soil and irrigation water are commonly contaminated with hexavalent chromium [Cr(VI)] near urban industrial areas, thereby threatening the safety of agricultural products and human health. In this study, we develop a porous and high specific area bone char (BC) to support nanoscale zero-valent iron (nZVI) and apply it to remediate Cr(VI) pollution in water and paddy soil under anaerobic conditions. The batch experiments reveal that BC/nZVI exhibits a higher removal capacity of 516.7 mg/(g•nZVI) for Cr(VI) than nZVI when normalized to the actual nZVI content, which is 2.8 times that of nZVI; moreover, the highest nZVI utilization is the nZVI loading of 15% (BC/nZVI15). The Cr(VI) removal efficiency of BC/nZVI15 decreases with increasing pH (4 - 10). Coexisting ions (phosphate and carbonate) and humic acid can inhibit the removal of Cr(VI) with BC/nZVI15. Additionally, BC exhibits a strong advantage in promoting Cr(VI) removal by nZVI compared to the widely used biochar and activated carbon. Our results demonstrate that reduction and coprecipitation are the dominant Cr(VI) removal mechanisms. Furthermore, BC/nZVI15 shows a significantly higher reduction and removal efficiency as well as a strong anti-interference ability for Cr(VI) in paddy soil, as compared to nZVI. These findings provide a new effective material for remediating Cr(VI) pollution from water and soil., (Copyright © 2020. Published by Elsevier B.V.)

P-chlorophenol (P–CP) is a recalcitrant toxicant in wastewater. Recently, the use of composite materials and environmentally friendly technology in the degradation of pollutants in wastewater has attracted widespread attention. For the first time, the nano zerovalent iron nano zerovalent iron (NZVI)-loaded muscovite (NZVI@muscovite), a novel composite material, was synthesized by liquid-phase reduction. The different physicochemical properties of NZVI@muscovite indicated that the muscovite could support NZVI of 40–50 nm sizes. The NZVI@muscovite had a low agglomeration degree, good dispersibility, and improved catalytic activity. In addition, the optimization experiments of P–CP degradation demonstrated that NZVI@muscovite actively degraded P–CP at a pollutant:catalyst ratio of 714 mg:1 g. This ratio was higher than that of the other composite materials under optimal operating conditions. Adsorption and degradation by Fenton-like reaction were the main mechanisms underlying P–CP degradation. This study extended the use of NZVI@muscovite as an efficient composite material for the degradation of P–CP in an aqueous environment. Unlabelled Image • Nano zerovalent iron/muscovite (NZVI@muscovite) were synthesized • NZVI@muscovite composite was characterized in detail • NZVI@muscovite degraded P-CP at a pollutant: catalyst ratio of 714 mg:1 g • NZVI@muscovite degraded P-CP was adsorption-Fenton-like reaction [ABSTRACT FROM AUTHOR]

• EPS@nZVI showed great Sb adsorption capacity even under nonacidic conditions. • EPS can protect inner Fe0 from being passivated by air. • Coated EPS did not inhibit electron transfer of nZVI. • EPS can inhibit Fenton reaction of nZVI, improving reducibility of nZVI. • Besides nZVI, functional groups on EPS were responsible for Sb(V) reduction. In this work, we prepared microbial extracellular polymeric substances-coated nano zero valent iron (EPS@nZVI) for Sb(V) removal. Batch adsorption experiments showed that the synthesized EPS@nZVI had superior maximum adsorption capacity (202 mg/g at pH = 5) for Sb(V), much higher than that of bare nZVI especially under nonacidic conditions. The adsorption results fit the pseudo-second-order kinetic model and the Redlich-Peterson model well, implying that the adsorption was more like a chemical adsorption process. The spectral analysis showed that EPS could protect inner Fe0 from air, preventing nZVI from generating a passivation layer on the surface, and decreasing the concentration of hydroxyl radicals in aqueous environment, which increased the reactivity of nZVI and strengthened the reducibility and adsorbability of nZVI. The coated EPS can improve the reactivity of nZVI instead of inhibiting its electron transfer. Moreover, the electrostatic repulsion between EPS@nZVI and Sb(OH) 6 − was decreased compared to that of bare nZVI after the introduction of EPS. The functional groups of EPS could play a significant role in the reduction adsorption, especially under alkaline conditions where nZVI was passivated. This work proved that EPS@nZVI has great prospects in simultaneously combining the reduction activity of nZVI in water and its stability in air. [ABSTRACT FROM AUTHOR]

In recent years, with the rapid development of economy and industry, the increasing pollution of pentavalent vanadium (V(V)) in water has led to potential dangers to human health, which cannot be ignored. In this study, nano zero-valent iron (nZVI) was successfully stabilized by biochar (BC) to remediate vanadium(V(V)) contaminated wastewater. The removal process of V(V) from water by the synthesized nZVI/BC under different conditions was systematically discussed. The results showed that the removal efficiency of V(V) increased with the increase of nZVI/BC dosage, which was related to the corresponding increase of reaction sites. Moreover, the removal capacity (48.5 mg/g) was independent on the pH of solution in the range of 2.0∼10.0 and the adsorption kinetic fitted well with the pseudo-second-order model (R 2 = 0.9998). When the initial V(V) concentration was below 25 mg/L, the removal efficiency of V(V) was higher than 99%. The removal mechanism of V(V) by the nZVI/BC composite was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The results showed that the interaction between nZVI/BC and V(V) was primarily controlled by electrostatic attraction, redox and precipitation processes. In a word, the nZVI/BC composite can be used as an effective alternative for V(V) removal from wastewater. [ABSTRACT FROM AUTHOR]

The chloride ion (Cl−) is a matrix ion that plays crucial roles in radical-based oxidation processes used to treat brackish or saline water. Here, the effects of the formation of reactive chlorine species on the performance of and reaction mechanisms involved in persulfate/nano zero-valent iron process were evaluated by investigating the reaction kinetics and performing reactive species scavenging tests. The phenol oxidation rate increased markedly in the early reaction stage in the presence of 25–200 mM of Cl−. This was because excess sulfate radicals (SO 4 −) reacted with Cl− to produce short-lived reactive chlorine species such as Cl and Cl 2 − rather than being scavenged by Fe2+ or other SO 4 −. The reactive chlorine species caused OH to form through radical propagation reactions. The total numbers of reactive species involved in phenol oxidation were higher at brackish to weakly saline Cl− concentrations than at lower and higher Cl− concentrations. At high Cl− concentrations (>400 mM), the phenol oxidation rate decreased because most of the SO 4 − reacted with Cl− to give large amounts of weaker oxidants such as Cl 2 − and HOCl. Acceleration of Fe corrosion by Cl− negligibly affected the persulfate/nano zero-valent iron oxidation process. Image 1 • The amount of reactive chlorine species formed affects the persulfate/NZVI process. • Low to intermediate Cl− concentrations cause high total reactive species yields. • HOCl contribution to oxidation becomes important in the presence of excess Cl−. • Accelerated Fe corrosion caused by Cl− does not affect the persulfate/NZVI process. [ABSTRACT FROM AUTHOR]

• nZVI@BC enhanced the reductive defluorination and inhibited the infiltration of TA. • TA bio-dehalogenation was accompanied by side-chain rupture, oxidation, and ring opening. • Defluorination accounted for 42.2% of biodegradation in the nZVI@BC system. • TA removal was positively correlated with bacterial diversity and activity. • Functional microbes with iron oxidation and reductive dehalogenation contributed to TA removal. The main aim of this study was to investigate the effect of a nano zero-valent iron-modified biochar-amended composite riverbed (nZVI@BC-R) on inhibited infiltration and enhanced biodegradation of fluoroglucocorticoids (FGCs) in a river receiving reclaimed water. The results demonstrated that the removal efficiency of triamcinolone acetonide (TA), a representative FGC, increased from 38.40% and 77.91% to 91.60% in the nZVI@BC-R compared with that of a natural soil riverbed (S-R) and biochar-amended soil riverbed (BC-R). The main removal mechanism was attributed to adsorption and biodegradation, of which the contribution rates were 32.2% and 59.4% in nZVI@BC-R, 18.9% and 19.5% in S-R, and 24.4% and 53.5% in BC-R, respectively. The removal process could be described by a two-compartment, first-order dynamic model with decay rate constants for adsorption and biodegradation of 4.02700, 22.44400, and 29.07300 d−1 and 0.00286, 0.01562, and 0.03484 d−1 in the S-R, BC-R and nZVI@BC-R, respectively. The mechanism of defluorination accounted for 42.2% of biodegradation in the nZVI@BC-R, which was accompanied by side-chain rupture, oxidation, and ring opening. Functional microbes with iron oxidizing ability and reductive dehalogenating genera, namely Pseudoxanthomonas , Pedobacter , and Bosea , contributed to the high removal rate of TA, particularly in the nZVI@BC-R. Overall, the nZVI@BC-R provided an effective method to inhibit glucocorticoids infiltration into groundwater. [ABSTRACT FROM AUTHOR]