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Nowadays, the problem of heavy metal pollution in vegetables is received wide attention. In this work, attapulgite clay (ATTP), as a cheap and readily available inorganic mineral material, was modified with nano zero-valent iron (nFe0@ATTP) for heavy metal immobilization in soil. Batch experiments were employed to evaluate the optimal remediation performance by ATTP before and after modified with nFe0 through planting Pakchoi (Brassica chinesis L.) in Cd, Cr, and Pb contaminated soil from Changsha. The results showed that amendments can all increase the pH value of soils, and notably decrease the concentration of extractable Cd, Cr, and Pb in soil. The germination rate and root length of Pakchoi were promoted, and the activities of peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) contents were notably reduced besides superoxide dismutase (SOD) activity after treatments with ATTP and nFe0@ATTP. Vicia faba -micronucleus test indicated that the application of amendments reduced the toxicity of heavy metals on the genetic material of Vicia faba root tip cells. The nFe0@ATTP were found to well convert Cd, Cr, and Pb into less bioavailable state in soil, thus blocking heavy metal uptake by plants. This material could be a promising amendment for heavy metals contaminated soil. Unlabelled Image • Attapulgite (ATTP) was successfully modified with nano zero-valent iron (nFe0@ATTP). • ATTP modified by nFe0 can improve the ability to immobilize Cd, Cr, and Pb in soil. • The activity of POD, CAT, and MDA content were reduced besides SOD after treatment. • The amendments can well convert Cd, Cr, and Pb into less bioavailable state in soil. [ABSTRACT FROM AUTHOR]

Oxytetracycline has posed a serious environmental nuisance, and seeking environmental decontamination materials is the priority task to deal with antibiotic water contamination. Herein, boron-doped biochar loaded nano zero-valent iron composites (nZVI/BBC) were fabricated as activators of PDS for oxidative degradation of oxytetracycline hydrochloride (OTC), and the main removal mechanism was explored in detail. The results showed that Boron-doped biochar with borate ester structure (BC 2 O) and degree of defects are the main active sites for improving PDS activation properties. BBC could effectively prevent nZVI agglomeration and reduce nZVI passivation. The effects of calcination temperature of BBC, loading ratio and dosage of nZVI/BBC, PDS concentration, initial solution pH, pollutant concentration, and interfering ions on OTC removal by nZVI/BBC were also systematically investigated, and the optimal reaction conditions were screened: 10 wt% loading of nZVI in the composite, 1 g/L dosage of nZVI/BBC, 1 mM dosage of PDS and solution pH= 5. The cycling test showed that the removal rate of OTC by nZVI/BBC decreased from 95.3% to 70.2% after five cycles, indicating that there is excellent stability of this material. Among them, the catalyst of 10%nZVI/BBC displayed the optimal PDS activation performance, owing to the synergistic adsorption-double oxidation system, BBC as well as nZVI. The free radical quenching experiment and free radical trapping experiment proved that the degradation of OTC mainly followed the free radical pathway and SO 4 •− and •OH were the primary active species in the catalytic system. This study provides a practical reference for the treatment of actual antibiotic wastewater. • Boron-doped biochar with borate ester structure and degree of defects are the main active sites for PS activation properties. • Boron-doped biochar effectively prevents nZVI agglomeration and reduces nZVI passivation. • nZVI/BBC exhibits a synergistic adsorption-double oxidation effect, facilitating activation of PDS and degradation of OTC. • 10 wt%nZVI/BBC possesses excellent stability in OTC degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • La@nZVI/rGO can efficiently and steadily activate PMS to degrade OFX. • The key role of La coating in regulating the PMS activation mechanism was explored. • 1O 2 for La@nZVI/rGO while ̇OH/SO 4 ̇− for nZVI/rGO were observed and confirmed. • La coating can break the limitation of rapid passivation and inactivation of nZVI. The nano zero-valent iron (nZVI)/peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) are promising for removal of antibiotic contaminants in groundwater. However, the inherent defects of rapid passivation and inactivation limit the efficient and steady application of nZVI. Herein, the lanthanum@nZVI/rGO (La@nZVI/rGO) was synthesized in which nZVI was coated with La and distributed evenly on reduced graphene oxide (rGO) matrix. The introduction of La coating protected the nZVI from direct contact with PMS molecules thus the La@nZVI/rGO appeared efficient and steady activization of PMS to degrade ofloxacin (OFX) without rapid inactivation. The removal rate was promoted to 96.5 % compared with the uncoated nZVI/rGO (only 85.2 %). The degradation reaction represented steady and continuous activation of PMS with pseudo-first-order kinetics (0.0451 min−1). While the two-stage kinetics of nZVI/rGO/PMS with initial 0.2581 min−1 and instant 0.0024 min−1 resulted from the rapid inactivation of nZVI. The reaction of La@nZVI/rGO/PMS exhibited minimal leaching of Fe ions (less than 1.8 µg/L) while it reached 6.4 mg/L in nZVI/rGO/PMS. XRD and XPS analyses further demonstrated the excellent durability of La@nZVI/rGO and the obvious passivation of nZVI/rGO. ESR and quenching tests confirmed that La coating regulated the PMS activation and ROS generation mechanism. The degradation was dominated by 1O 2 -induced non-free radical process in La@nZVI/rGO/PMS system and different from radical oxidation in nZVI/rGO/PMS. Moreover, the dissolved oxygen and XPS analysis revealed the important role of La coating and oxygen vacancy in the catalytic degradation. This work could provide a novel understanding of the nZVI with protective coating in AOPs environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • nZVI exposure increased the antibiotic resistome in anaerobic digestion. • Efflux pump and rRNA methyltransferase shaped the antibiotic resistome variation. • Improved adaptability of efflux pump benefited the anaerobes withstanding nZVI. • Increased acquisition of rRNA methyltransferase preserved the structure of protein. • Polyspecificity of multidrug resistance drove the ARGs evolution in anaerobes. Nano zero-valent iron (nZVI) assisted anaerobic digestion (AD) is considered an effective approach for mediating antibiotic resistance genes (ARGs) dissemination in activated sludge. However, little is known about the mechanisms that drive antibiotic resistomes evolution in relation with their physiological roles distinct from protection of bacteria against antimicrobials. Metagenomic sequencing showed that efflux pumps and rRNA methyltransferase genes were the most prevalent ARGs in anaerobes, being responsible for the variations of antibiotic resistome upon nZVI addition. Particularly, to withstand the oxidative stimuli derived from initially 9 days nZVI exposure, genes involved in the two component systems (PhoRB , BaeSR , EvgSA) and global regulator networks (MarA , SoxS) were increased, activating the chromosomally encoded intrinsic efflux pumps expression. Furthermore, to benefit for survival, the polyspecific efflux pumps were involved in the microbial physiological adaptations of enhanced siderophores, lipid moieties, and quorum sensing molecules exportation, which induced the adaptative efflux pumps expression. On the other hand, to maintain the protein synthesis under oxidative condition, genes encoding Rsm, Erm, and Rlu family methyltransferases were notably up-regulated via horizontal transfer, inducing the acquired rRNA methylation resistance. Importantly, after prolonged exposure to nZVI for 18 and 27 days, the antibiotic resistomes were measurably decreased, due to the recovered oxidative state and increased membrane rigidity. Overall, these findings provide a deep understanding on the necessity of antibiotic resistome evolution for anaerobes to adapt to nZVI exposure for survival, which can be introduced to improve the ARGs risks analysis. [ABSTRACT FROM AUTHOR]

Electro-Fenton reaction mechanism by the porous fiber electrodes of NZVIF-800 for degradation and sterilization. [Display omitted] • Nano-zero-valent iron based electrostatic spinning fiber electrode was fabricated. • Electrode showed great electro-Fenton activity for secnidazole and real wastewater. • Decomposition process of secnidazole and organics in real wastewater was revealed. • Electrode exhibited strong sterilization ability for the actual wastewater matrix. In this study, a novel metal–organic framework (MOF) derived fiber electrode (NZVIF-800) was successfully fabricated by a novel electrostatic spinning and pyrolysis procedure. The NZVIF-800 electrode exhibited great catalytic activity in a heterogeneous electro-Fenton (EF) system for organic degradation, in which the secnidazole (SCZ) was completely degraded within 60 min with excellent stability (no significant change after eight cycles). Importantly, the NZVIF-800 electrode was also highly effective for decontaminating actual pharmaceutical wastewater, in which the TOC and COD removal reached 38% and 47%, respectively, after 4 h EF reaction. Based on experimental analysis, microstructure characterization, and theoretical calculations, the detailed reaction mechanism of the NZVIF-800 electrode was revealed. The impressive EF performance was mainly attributed to the in situ generation of active nano-zero-valent iron (NZVI) derived from the MOF pyrolysis and the confinement effect of the encased carbon layer that could effectively inhibit the loss and inactivation of Fe active sites. The degradation pathways of organic pollutants in simulated and real wastewater were proposed in detail. Significantly, the EF system with NZVIF-800 electrode exhibited strong sterilization ability for the wastewater matrix as evidenced by the colony condition, OD 600 values, and Illumina MiSeq sequencing platform analysis (up to 95% sterilization efficiency within 4 h), expanding its application scope for actual wastewater treatment. [ABSTRACT FROM AUTHOR]

Microplastics pollution in environments has become a major concern and it has been proven to have adverse impacts on plants, so there is an urgent to find approaches to alleviate the detrimental effects of microplastics. In our study, we investigated the influence of polystyrene microplastics (PSMPs) on the growth, photosynthesis, and oxidative defense system changes of ryegrass, as well as the behavior of MPs at roots. Then three types of nanomaterials were applied to alleviate the adverse impact of PSMPs on ryegrass, which were nano zero-valent iron (nZVI), carboxymethylcellulose-modified-nZVI (C-nZVI) and sulfidated nZVI (S-nZVI), respectively. Our results suggested that PSMPs had significant toxicity to ryegrass, leading to decrease of shoot weight, shoot length and root length. Three nanomaterials regained the weight of ryegrass to a varying extent and made more PSMPs aggregate near roots. In addition, C-nZVI and S-nZVI facilitated the entrance of PSMPs into the root and promoted the chlorophyll a and chlorophyll b contents in leaves. Analysis of antioxidant enzymes and malondialdehyde content indicated that ryegrass coped well with the internalization of PSMPs, and all three types of nZVI could alleviate PSMPs-stress in ryegrass. This study elaborates the toxicity of MPs on plants and provides a novel insight into the fixing of MPs by plants and nanomaterials in environments, which needs to be further explored in future research. [Display omitted] • PSMPs decreased biomass, length and photosynthetic pigments of plants. • Three types of nZVI all alleviated the toxicity of PSMPs. • Three types of nZVI all promoted plant growth under exposure of PSMPs. • C-nZVI and S-nZVI facilitated the internalization of PSMPs. • S-nZVI might have a more alleviation on the oxidative stress when exposed to PSMPs. [ABSTRACT FROM AUTHOR]

Aging effects play a crucial role in determining applications of green-synthesised iron-based nanoparticles in wastewater treatment from laboratory scale to practical applications. In this study, iron-based nanoparticles (Ec-Fe-NPs) were synthesised using the extract of Eichhornia crassipes and ferric chloride. Scanning electron microscopy (SEM) revealed that the fresh Ec-Fe-NPs were spherical and had a narrow particle size range (50 to 80 nm). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrated that the Ec-Fe-NPs were mainly amorphous in nature and consisted of Fe0, FeO, Fe2O3 and Fe3O4. As they aged, the particle size of the liquid Ec-Fe-NPs gradually increased and then tended to stabilise. Ec-Fe-NPs that were aged for 28 days were only 19% less efficient than fresh material at removing Cr(VI). Extracts aged up to 28 days were also tested, and their antioxidant capacity was found to be 15.4% lower than that of the fresh extracts. Furthermore, the removal efficiency of Cr(VI) using iron-based nanoparticles synthesised with the aged extracts was 67.2%. Finally, the active components of the extracts, which were responsible for the reactivity and stability of the iron-based nanoparticles, were identified by liquid chromatography–mass spectrometry. Overall, green-synthesised iron-based nanoparticles show promise for Cr(VI) removal from wastewater in practical applications. [ABSTRACT FROM AUTHOR]

As the functional material, iron nanoparticles effectively promote anaerobic digestion (AD) process, including the hydrolysis-acidification process and the biogas production. In this study, nano zero-valent iron (nZVI) and Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) were added to AD reactors respectively. The AD process was evaluated by the reactors performances, including pH, biogas yields and compositions, as well as the removal ratio of total solids (TS), volatile solids (VS) and soluble chemical oxygen demand (sCOD). Three models (first-order kinetic model, transfer function model and Cone model) were used to explore the kinetics of AD biogas production. The results showed that adding appropriate dose of nZVI or Fe 3 O 4 NPs enhanced anaerobic digestibility of sludge. The highest cumulative biogas yield of 140.34 L with 0.5 g L−1 nZVI and 137.13 L with 1 g L−1 Fe 3 O 4 NPs were obtained by the 80 days of mesophilic operation, respectively. Cumulative biogas productions of these two reactors were significantly enhanced up to 15.70% and 13.44%. TS removal rates reached >70% in all AD reactors with iron nanoparticles, and the highest sCOD removal rates of nZVI and Fe 3 O 4 NPs digesters on the 80th day were 88.22% and 77.63%, respectively. The results of the three-day fermentation experiment and the kinetic parameters showed that the nZVI or Fe 3 O 4 NPs enhanced the hydrolysis-acidification process of the AD, which eventually promoted biogas production. The Cone model was satisfied with the experimental results, which could be used to evaluate the kinetics of AD with iron nanoparticles more reasonably. Unlabelled Image • Addition of nZVI and Fe 3 O 4 NPs upgraded the sludge biogas production. • The optimum dosage for biogas generation was 0.5 g L−1 of nZVI and 1 g L−1 of Fe 3 O 4 NPs. • nZVI and Fe 3 O 4 NPs improved the sCOD and VS removal efficiencies. • nZVI and Fe 3 O 4 NPs promoted the hydrolysis-acidification process of the sludge. • Cone model best fitted the biogas results in AD with iron nanoparticles addition. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr), one of the most common heavy metals, is widely found in contaminated soil and groundwater. Nano zero-valent iron (nZVI) is used to treat Cr(VI) in polluted groundwater. However, due to agglomeration, rapid sedimentation, and limited mobility of nanoparticles in the aquatic environment, nZVI is not widely used in groundwater treatment. In this study, we used sodium alginate (SA) to modify nZVI to generate dispersed SA-nZVI. SA-nZVI particles were found to embed in the polymer material and exist as an amorphous state with a diameter less than 100 nm. Compared with traditional nZVI and carboxymethyl cellulose (CMC)-nZVI, SA-nZVI had better stability and higher absolute zeta potential. The presence of SA enhanced mobility of nZVI and effectively prevented sedimentation and aggregation. Furthermore, SA-nZVI had a higher Cr(VI) removal rate than (CMC)-nZVI under both acidic and alkaline conditions. XPS analysis showed that Cr(VI) was reduced to Cr(III) and formed Cr(OH) 3 as precipitates after treatment with SA-nZVI. In addition, NO 3 − had no effect on the final removal rate of Cr(VI) by SA-nZVI. These results suggest that SA-nZVI has high penetration and a high removal rate in Cr(VI) removal and can be used to stabilize nZVI to remediate Cr(VI)-contaminated groundwater in the future. • Sodium alginate was used to disperse nZVI to develop a new type nZVI material (SA-nZVI). • SA-nZVI has higher penetration and higher removal rate than traditional nZVI in chromium removal. • SA-nZVI is a promising material for Cr(VI) contaminated groundwater remediation [ABSTRACT FROM AUTHOR]

In this study, the synergetic effects in a Fenton-like system catalyzed by nano zero-valent iron (nZVI Fenton-like system) were studied using nitrobenzene (NB) as a model contaminant. The results showed that homogeneous and heterogeneous Fenton processes existed simultaneously in the nZVI Fenton-like system, and a synergetic removal effect between these processes played a considerable role in NB removal. Through quantitative analysis, 36.5% of NB degradation was attributed to the synergetic degradation effect, which was caused by a synergetic catalytic effect between nZVI and dissolved iron ions (Fe3+ and Fe2+ ). In the bulk solution, the Fe3+ /Fe2+ redox rate was accelerated by nZVI, resulting in the efficiency improvement of homogeneous catalysis; in the surface of nZVI, these dissolved iron ions promoted the electrons transfer from nZVI core to shell, enhancing the efficiency of heterogeneous catalysis. The synergetic catalytic effect also improved the utilization-rate of H2 O2 by reducing the decomposition caused by Fe3+ /Fe2+ redox compared to that in the homogeneous Fenton system. Based on these results, a possible mechanism of synergetic effects in the nZVI Fenton-like system was proposed. These results could provide insight into an nZVI Fenton-like system. [ABSTRACT FROM AUTHOR]

Abstract Stable surfactant foam might play a vital role in the effective remediation of diesel oil contaminated soil-a major environmental hazard. This paper, first of its kind, is reporting the remediation of diesel-contaminated desert soil, coastal soil and clay soil by aqueous alkylpolyglucoside phosphate (APG-Ph) surfactant foams stabilized by Fe0 and Fe 3 O 4 nanoparticles. Zero-valent iron (Fe0, ∼28 nm) and iron oxide (Fe 3 O 4 , ∼20 nm) nanoparticles are synthesized by liquid-phase reduction and precipitation methods, respectively. The effect of these nanoparticles on foamability, foam stability, surface tension and remediation of diesel-contaminated soils are examined at various concentrations (volume %) of alkylpolyglucoside phosphate (APG-Ph) surfactant and nanoparticles (mg/l). The maximum values of foamability and foam stability recorded for 0.1 vol % APG-Ph foam stabilized by 3.5 mg/l Fe0 are 108.3 and 110.4 mL, respectively. At the same conditions, the Fe 3 O 4 results in 99.4 and 87.5 mL, respectively, depicting the better performance of Fe0. Reduction in surface tension of 0.1 vol % APG-Ph solution (50.75 mN/m) with the addition of 3.5 mg/l Fe0 (9.51 mN/m) and Fe 3 O 4 (19.45 mN/m) nanoparticle is observed. Both the nanoparticles enhance remediation. The foam formed with 0.1 vol % APG-Ph and stabilized by 3.5 mg/l Fe0 shows the maximum diesel removal efficiency of 95.3, 94.6, and 57.5% for coastal soil, desert soil and clay soil, respectively. On the other hand, Fe 3 O 4 (3.5 mg/l) stabilized APG-Ph foam of the same concentration shows merely 76.0, 79.6 and 51.6% diesel removal efficiency for coastal soil, desert soil, and clay soil, respectively. The rate of diesel removal by zero-valent iron and iron oxide nanoparticle stabilized foams are found to be well described by the first order kinetic model. Higher foamability, foam stability, and reducing capacity accompanying lower surface tension, compared to those of the Fe 3 O 4 nanoparticle stabilized foam, could explain higher diesel removal efficiency of the Fe0 nanoparticle stabilized foam. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Disorder mining and massive consumption of Sb-bearing ores have caused a dramatic rise in the accumulation of Sb related pollution in China over the past decade. The combination of iron-based adsorption and electrokinetics was applied in the batch and column experiments to enhance removal of Sb(V) anions from the feed water. Activated carbon supported nano zero-valent iron (AC-nZVI) was prepared as the filling adsorbent for the adsorption experiments. The maximum monolayer-adsorption capacity of AC-nZVI was 20.49 mg/g according to the Langmuir isotherm results. Sufficient dose of adsorbent with sufficient dose and pH ranging from 4 to 5 were favored in the equilibrium adsorption. Electrokinetics clearly had enhanced Sb(V) removal from the feed water with the maximum removal efficiency of 96.42% being achieved in the coupling system. The variable changes significantly affected the removal results of Sb(V) ions in the coupling experiments at a batch mode. The antimony species can be effectively removed from the stock solution in the continuous process. The flow rate of 40 mL/min was favored in facilitating the excellent performance of the assembled units at a minimum operating cost. The adsorbent regenerated within three cycles is still reliable in terms of removing Sb in a continuous treatment process. [ABSTRACT FROM AUTHOR]

Highlights • NZVI particles anchored on kaolinite was applied in Fenton oxidation process. • NZVI@K possess high adsorption capacity and good ability in H 2 O 2 decomposition. • A tentative mechanism was proposed for activate H 2 O 2 and reactive species. • Decreasing decolorization obeys the order of sulfate > nitrate > chloride > bicarbonate. • After four consecutive cycles, decolorization rate by was still remains at 72.5%. Abstract Herein, nano zero-valent iron (NZVI) particles were anchored on kaolinite (K) for preparation of a mesoporous heterogeneous catalyst (marked as NZVI@K) in Fenton-like oxidation of Acid Black 1 (AB1) dye. The properties of morphological, physico-chemical and textural of catalyst were characterized using powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscope (TEM), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDS) techniques. Results indicated that NZVI particles with 40–80 nm diameter were incorporated successfully on K surface and iron was predominantly in Feo form. Prior oxidation experiments, adsorption studies were performed to determine the equilibrium point and also modeling (kinetic and isotherm) of the process. Fenton-like oxidation showed a better performance in decolorization of AB1, compared to adsorption process. The excellent reusability and high stability were found for NZVI@K during four consecutive use cycles. Under optimum operational conditions (pH: 2.0, catalyst dose: 0.3 g/L, H 2 O 2 amount: 4.0 Mm), over 98% of dye (30 mg/L) and 76% of TOC were removed within 120 min reaction. A tentative mechanism was proposed for decomposition of H 2 O 2 and production of reactive oxidizing species, based on the results of quenching tests. Decreasing decolorization rate in the presence of anions obeys the order of bicarbonate > chloride > nitrate > sulfate. A significant synergistic effect was detected when NZVI@K were coupled with H 2 O 2. Reducing removal efficiency and the scavenging effect were observed at excessive concentrations of both catalyst and oxidant. Integration of adsorption and oxidation processes using NZVI@K coupled with H 2 O 2 can be introduced as a promising technique for efficient decolorization of wastewaters, due to high adsorption capacity, good catalytic activity and minimal iron leaching. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

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This work aims to investigate the degradation of 2,4,6 trinitrotoluene (TNT) as a model typical nitro‐aromatic compound. The degradation process was carried out by hydroxyl radical that was produced via hydrogen peroxide activated by nano zero‐valent iron (Fe0). The nanoparticles as a source of ferrous ions were synthesized by precipitation method using a starch coating as a stabilizer. The transmission electron microscope analysis revealed that the size of the Fe0 particles is about 40 nm. The operating parameters were optimized using central composite design as a kind of response surface methodology. The degradation efficiency of 91% during 10 minutes and mineralization efficiency of 83% during 40 minutes were obtained under the experimental conditions of 30 mg/L TNT, 104.8 mg/L Fe0, 675 mg/L H2O2, and pH of 3.5. Finally, redwater treatment as real nitro‐aromatic wastewater was evaluated by this process, and 63% removal efficiency was attained after 40 minutes in the optimum condition. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 477–482, 2019 [ABSTRACT FROM AUTHOR]

Abstract In this study, the effects of surface modification of nZVI and arsenic (As) loading on the mobility of the three types of As-loaded nZVI (As-loaded pristine, chitosan-modified and polyaniline-modified nZVI) in quartz sand-packed columns were investigated. Breakthrough curves and retention profiles for the three types of As-loaded nZVI were analyzed by the Tufenkji-Elimelech equations and the HYDRUS-1D model. The mobility of both types of As-loaded modified nZVI was higher than the As-loaded pristine nZVI at both low and high As loadings. Compared to low As loading, the mobility of the three types of As-loaded nZVI was higher at high As loading. The values of the calculated and the fitted retention parameters of the three As-loaded nZVI were lower when As loading was higher or nZVI was modified, which were in line with the experimental column findings. The mechanisms of As-loaded nZVI transport were probably due to ripening and sedimentation. The As in the effluent was mainly from the As-loaded nZVI particles when nZVI was detected and was from the As release when no nZVI was detectable. It was evident that the mobility of the three types of As-loaded nZVI particles were severely limited (the maximum transport distance was less than 60 cm), regardless of surface modification and As loading. Therefore, the As release from the As-loaded nZVI could cause potentially wide pollution and should be paid more attention regarding to the application of nZVI in As remediation. Graphical abstract Image 1 Highlights • Surface modification and high As loading enhanced the mobility of As-loaded nZVI. • The transport mechanisms of the As-loaded nZVI were the ripening and sedimentation. • Arsenic in the effluent was from the As release when nZVI was not detected. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a novel Gum Tragacanth-based carbon dots-nano zero-valent iron composite was prepared via cost-effective and green one-step hydrothermal method. A new composite was applied for its potential as a novel heterogeneous Fenton-like catalyst in order to remove bio-refractory antibiotics from aqueous solution. The morphological, structural, electrochemical and physicochemical properties of the new composite were evaluated using TEM, SEM, DLS, Cyclic voltammetry, XRD and FTIR techniques. Development of nano-scale metallic iron particles encapsulated in carbon dot films with an average size of ∼237 nm was observed. Using experimental design and response surface methodology, at optimum process conditions ([H 2 O 2 ] of 20 mM, time of 60 min and amount of catalyst of 765 mg/l), a superior catalytic performance of the composites were confirmed by removing rate of amoxicillin and ciprofloxacin equal to 90% and 51%, respectively. From the mechanism study using FTIR analysis, it can be concluded that composite reacts with H 2 O 2 and due to oxidation, different iron oxides are produced indicating nano zero-valen iron particles is reduced and convert H 2 O 2 to OH• radicals. The encapsulation of nano zero-valent iron in biopolymer based carbon dots can enhance air/water stability and prolong the reactivity of nano zero-valent iron with H 2 O 2. Results indicate that carbon dots-nano zero-valent iron composite-mediated heterogeneous Fenton oxidation technology is an effective strategy for pollutant abatement. Highlights • Synthesize nano zero-valent iron encapsulated in bio-polymer based carbon dots. • NZVI@CD catalyst preparation via one-pot hydrothermal route without chemicals. • Heterogeneous catalytic Fenton reaction using NZVI@CD for antibiotic removal. • Removal of 90% of AMX and 51% of CIP were achieved. • Activation of hydrogen peroxide to produce hydroxyl radicals using NZVI@CD. [ABSTRACT FROM AUTHOR]

We prepared nano zero-valent iron/biochar composites (nZVI/BC) to remove nitrate from groundwater with harmless products. Results show nZVI/BCs derived from different mass ratios of Fe(0) to biochar exhibited different nitrate removal efficiencies, and the mass ratio of 1:2 developed the nZVI/BC with optimum nitrate removal. The nZVI/BC maintained preferable nitrate removal (75.0%–97.0%) over a wide pH range 2–12. Nitrate removal amount declined due to serious corrosion and clogging of nZVI/BC’s surface when initial nitrate concentration exceeded 40 mg/L. The nitrate removal process followed a first-order kinetic reaction. As regards real groundwater, the nZVI/BC removed more nitrate than both pure Fe(0) nanoparticles and biochar. Reaction product analysis revealed 60.1% of removed nitrate selectively became dinitrogen. X-ray photoelectron spectroscopy measurements suggested that nitrate-oxidized Fe(0) resulted in significant increase of magnetite on the surface of nZVI/BC. The redox potential and pH of long duration in reaction changed around −210 mV and 8–9, respectively. These changes facilitated the selective reduction of nitrate to dinitrogen. We also proposed that biochar may provide favorable circumstances for nitrate reduction by directly mediating redox potential, pH and electron transfer, which establishes a possible mechanism for the enhanced removal and selective reduction of nitrate. Our study suggests that nZVI/BC would be a promising alternative for the remediation of nitrate-contaminated groundwater. [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.

[Display omitted] • nZVI was adopted for the first time to remove ARGs at the maturation stage of composting. • The addition of nZVI reduced iARGs and eARGs in composting by 51–99%. • The removal of iARGs was due to the decreased abundance of host bacteria and intI 1. • The addition of nZVI improved the quality of the compost. Applying compost to soil may lead to the spread of antibiotic resistance genes (ARGs) in the environment. Therefore, removing ARGs from compost is critical. In this study, for the first time, nano zero-valent iron (nZVI) was added to compost during the maturation stage to remove ARGs. After adding 1 g/kg of nZVI, the abundance of total intracellular and total extracellular ARGs was decreased by 97.62% and 99.60%, and that of total intracellular and total extracellular mobile genetic elements (MGEs) was decreased by 92.39% and 99.31%, respectively. A Mantel test and network analysis indicated that the reduction in potential host bacteria and intI 1 after nZVI treatment promoted the removal of intracellular and extracellular ARGs. The addition of nZVI during composting reduced the horizontal transfer of ARGs and improve the total nitrogen and germination index of compost, allowing it to meet the requirements for organic fertilizers. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (NZVI) is widely used for reducing chlorinated organic pollutants in water. However, the stability of the particles will affect the removal rate of the contaminant. In order to enhance the stability of nano zero-valent iron (NZVI), the particles were modified with F-127 as an environmentally friendly organic stabilizer. The study investigated the effect of the F-127 mass ratio on the colloidal stability of NZVI. Results show that the sedimentation behavior of F-NZVI varied at different mass ratios. A biphasic model was used to describe the two time-dependent settling processes (rapid sedimentation followed by slower settling), and the settling rates were calculated. The surface morphology of the synthesized F-NZVI was observed with a scanning electron microscope (SEM), and the functional groups of the samples were analyzed with Fourier Transform Infrared Spectroscopy (FTIR). Results show that the F-127 was successfully coated on the surface of the NZVI, and that significantly improved the stability of NZVI. Finally, in order to optimize the removal rate of 2,4-dichlorophenol (2,4-DCP) by F-NZVI, three variables were tested: the initial concentration 2,4-DCP, the pH, and the F-NZVI dosage. These were evaluated with a Box-Behnken Design (BBD) of response surface methodology (RSM). The experiments were designed by Design Expert software, and the regression model of fitting quadratic model was established. The following optimum removal conditions were determined: pH = 5, 3.5 g·L−1 F-NZVI for 22.5 mg·L−1 of 2,4-DCP.

In this paper, the ability of nZVI to remove heavy metals (Cd, Cu, Ni, Pb, Zn) from multicomponent aqueous solutions was investigated through batch experiments. The experimental data were fitted to a second-order kinetic model based on solid capacity. The data for copper and lead fitted well into the second-order kinetic model, thus suggesting that the adsorption had a physical character. The values of the removal ratio and the second-order rate constant indicated that the order of adsorption priority of nZVI was as follows: Pb>Cu>Zn>Cd>Ni. The adsorption isotherm data were described by the most conventional models (Henry, Freundlich, and Langmuir). Equilibrium tests showed that copper and zinc were removed from the solution by adsorption processes, i.e., complexation and competitive adsorption. The test results suggested that the removal processes using nZVI are more kinetic than equilibrium. The study demonstrated that nZVI is favorable reactive material; however, comprehensive investigation should be performed for further in situ applications in PRB technology.

Fenton's reagent has been widely used to enhance sludge dewaterability. However, drawbacks associated with hydrogen peroxide (H 2 O 2 ) in Fenton's reagents exist, since it is a hazardous chemical and shows carcinogenicity, explosivity, instability, and corrosivity. Moreover, initial acidification and subsequent neutralization are needed as optimal conditions for homogeneous Fenton conditioning and final filtrate discharge. In this study, a Fenton-like process for the enhanced dewaterability of waste activated sludge with in-situ generation of H 2 O 2 and without extra pH adjustment was firstly proposed, namely citric acid (CA)-assisted oxygen activation in an air/nano zero-valent iron (nZVI) system and chemical re-coagulation with polydiallyldimethylammonium chloride (PDMDAAC). Using the response surface methodology (RSM), the optimal doses of CA, nZVI, and PDMDAAC were determined to be 13, 33, and 9 mg g −1 dry solids (DS), respectively. This composite conditioner showed a good dewatering capability compared with the raw sludge, e.g. the capillary suction time decreased from 130.0 to 9.5 s. The enhanced sludge dewaterability was further confirmed by laboratory-scale diaphragm filter press dewatering tests, which produced a lower cake moisture content compared with the raw sludge, and the final pH of the filtrate was close to neutrality. The citric acid promoted the production of H 2 O 2 and Fe(II)/Fe(III) species, the degradation of protein in tightly-bound extracellular polymeric substances, and the decomposition of protein-N in the solid phase of sludge, resulting a greater conversion of bound water to free water. The results of electron spin resonance indicated that the hydroxyl radicals were mainly responsible for the decomposition of proteinaceous compounds. The subsequent chemical re-coagulation with PDMDAAC can make the zeta potential of sludge samples less negative, reduce the repulsive electrostatic interactions, and agglomerate the smaller particles into larger aggregates, thus enhancing sludge dewaterability. [ABSTRACT FROM AUTHOR]

A new carbonized pomelo peel biosorbent (MCPP) modified with nanoscale zero-valent iron (NZVI) and cetyl-trimethyl ammonium bromide was prepared and employed for the adsorption of molybdate (Mo(VI)) from aqueous solution. We investigated the effects of various conditions on Mo(VI) adsorption and evaluated the results based on adsorption kinetics models and isotherm equations. The kinetic data fitted to the pseudo-second-order model. The Langmuir model best described the adsorption of Mo(VI) on MCPP. The values of changes in Gibbs free energy, standard enthalpy, and standard entropy revealed that the adsorption process was feasible, spontaneous and endothermal. X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopy measurements suggested that Mo(VI) adsorption occurred via both the reduction and surface adsorption. Thus, biochar, prepared from fruit residue, can be applied to remove Mo(VI) from aqueous solutions. More importantly, our results provide a sustainable approach for Mo(VI) removal from wastewater by means of functional modification. [ABSTRACT FROM AUTHOR]

Novel ternary nanocomposite based on nano zero-valent iron (nZVI) and graphene-TiO 2 nanowires (Fe@GNW) was successfully synthesized for both reduction and photocatalytic oxidation of metronidazole (MNZ). Fe@GNW exhibits synergetic effects and significant properties, such as facilitating the photogenerated charges separation, enhancing the surface activity of nZVI, improving the adsorbent ability of catalyst, possessing the magnetic property for facile recycling. Due to the formation of micro-graphene-nZVI batteries and heterogeneous photo-Fenton system, Fe@GNW showed a superior activity in removal of MNZ (99.3%) compared with TiO 2 nanowires (43.0%) and graphene-TiO 2 nanowires (67.6%). Moreover, Fe@GNW retained excellent stability without apparent loss in catalytic activity after five cycles. MNZ removal by Fe@GNW experienced a two-stage process of reduction-adsorption and photocatalytic oxidation, which could be well-described by a revised pseudo-first order kinetics. The decomposition pathways of MNZ were proposed based on the analysis of intermediates. The quenching tests demonstrated that h + and OH are responsible for MNZ decomposition. New insights into the mechanism of the enhanced reduction and photodegradation of MNZ were proposed. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron (NZVI) supported by carbonized pomegranate peel (CPP) was synthesized by liquid-phase chemical reduction and characterization of the composites was carried out with Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, pHzpc (zero point of charge) and Brunauer–Emmett–Teller. NZVI/CPP composites were tested as adsorbents in the disposal of malachite green (MG) with certain parameters. The maximum adsorption value of MG was obtained as 99.7% for the adsorbent dose of 0.15 g in 30 min of equilibration time. The most suitable isotherm was obtained as the Langmuir isotherm (R² = 0.98) with the analysis of equilibrium data, and the maximum adsorption capacity (qm) was found as 32.47 mg/g. The pseudo-second-order kinetic model (R² ≥ 0.994) was found to be the best fit to the experimental data in comparison with the other models. The experimental results obtained at different temperatures were analyzed and adsorption was determined to occur endothermically and spontaneously due to the ΔH° value of 110.27 kJ/mol and ΔG° ≤ –0.89 kJ/mol, respectively. The positive values of ΔS° indicated that the irregularity in the interface between the NZVI/CPP adsorbent and the MG solution increased. NZVI/CPP may be used instead of active carbon for dye removal in industrial wastes due to its low cost and good performance. [ABSTRACT FROM AUTHOR]

In this study, nanoscale zero-valent iron (nZVI) with a considerably high surface area (182.97 m 2 ·g −1 ) and featured morphology of chain structure has been synthesized and well characterized. The as-prepared nZVI on can totally remove Cr(VI) under anoxic condition after 20 min reaction, whereas only 43% of Cr(VI) was removed after 60 min reaction under oxic condition. Noteworthily, the nZVI exhibits excellent removal capacity of Cr(VI) (123.85 mg/g) and fast removal rate (0.017 g·mg −1 ·min −1 ), much better than those reported in the literatures except for that reported by Li et al. (2008) [1] . Experimental results have confirmed that only FeCr 2 O 4 with low compactness was generated under anoxic and acidic conditions in the new process. And it is evident that the formation of the passivation layer which contains oxides and hydroxides (or (oxy)hydroxides) of iron and chromium were well hindered. Furthermore, the as-prepared nZVI has shown fast removal of traced Cr(VI) from the Cr-spiked drinking water or actual Cr-contaminated lake water. Accordingly, we proposed a new reaction process of Cr(VI) reduction by nZVI under anoxic condition. And we firstly make clear the detailed process of Cr(VI) removal by the as-prepared nZVI via X-ray photoelectron spectrometer (XPS) analysis in time scale. Meanwhile, the excellent Cr(VI) removal performance of the as-prepared nZVI could be attributed to (i) the high surface area, (ii) large quantity of active sites of nZVI, and (iii) fast electron transfer from the nZVI/FeCr 2 O 4 to Cr(VI). The present work not only provides the potential materials for the application to the rapid and high-efficient removal of Cr(VI) from aqueous solution, but also proposed a new avenue for hindering the passivation of Fe 0 . And a detailed mechanism of the Cr(VI) removal by nZVI was proposed for the first time. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation of 4-chlrophenol (4-CP) using UVA-LED assisted persulfate and hydrogen peroxide activated by the nZVI (Nano Zero Valent Iron) in a batch photocatalytic reactor was investigated. The reaction involved a lab-scale photoreactor irradiated with UVA-LED light emitted at 390 nm. The efficiency of the reaction was evaluted in terms of 4-CP degradation and mineralization degree at different pH of solution, initial concentrations of nZVI, persulfate, hydrogen peroxide and 4-CP. In UVA-LED/H2O2/nZVI process, complete degradation of 4-CP (>99%) and 75% mineralization was achieved at pH of 3, hydrogen peroxide concentration of 0.75 mM, nZVI dosage of 1mM and initial 4-CP concentration of 25mg/L at the reaction time of 30 min. The optimum conditions obtained for the best 4-CP degradation rate were at an initial concentration of 25mg/l, persulfate concentration of 1.5mM, nZVI dosage of 1mM, pH of 3 and reaction time of 120min for UVA-LED/persulfate/nZVI process. It was also observed that the 4-CP degradation rate is dependent on initial 4-CP concentrations for both processes. The pseudo-first-order kinetic constant at 25mg/L initial concentration of 4-CP was found to be 1.4×10−1 and 3.8×10−2 in UVA-LED/H2O2/nZVI and UVA-LED/persulfate/nZVI processes, respectively. Briefly, the UVA-LED/H2O2/nZVI process enhanced the degradation rate of 4-CP by 3.67-times in comparison to UVA-LED/persulfate/nZVI process at 30min contact time, which serves as a new and feasible approach for the degradation of 4-CP as well as other organic contaminants containing wastewater. [ABSTRACT FROM AUTHOR]

Organosolv lignin was used as stabilizer to synthesize Bentonite-Lignin nano zero-valent iron (BL-nZVI). Then FTIR, XRD, SEM and TEM were carried out to characterize this new material. Results proved that organosolv lignin can effectively prevent the aggregation of nano zero-valent iron particles. BL-nZVI was applied as particle electrodes and formed a three-dimensional (3D) electrode system with ruthenium/iridium coated titanium plates and acted as tertiary treatment process to dispose the pulp and paper secondary wastewater. The removal efficiency of the chemical oxygen demand (COD) and color of the effluent were selected as indicators to check the performance of the system. It was found that the removal efficiency of COD and color depended on the current density, electrolysis time, distance of electrode plates, initial pH value and particle electrode dosage. The optimal parameters of each factor were also determined by a series of single factor experiments. Under the optimum conditions, removal efficiency of COD and color can reach 87.6% and 93.1% respectively. Possible mechanism of the 3D electrode system with BL-nZVI particle electrodes for treatment of pulp and paper wastewater was also proposed. [ABSTRACT FROM AUTHOR]

Recently, nano zero-valent iron (nZVI) has emerged as an effective adsorbent for the removal of arsenic from aqueous solutions. However, its use in various applications has suffered from reactivity loss resulting in a decreased efficiency. Thus, the aim of this study was to develop an effective arsenic adsorbent as a core/shell structural nZVI/manganese oxide (or nZVI/Mn oxide) to minimize the reactivity loss of the nZVI. As the major result, the arsenic adsorption capacities of the nZVI/Mn oxide for As(V) and As(III) were approximately two and three times higher than that of the nZVI, respectively. In addition, the As(V) removal efficiency of the nZVI/Mn oxide was maintained through 4 cycles of regeneration whereas that of the nZVI was decreased significantly. The enhanced reactivity and reusability of the nZVI/Mn oxide can be successfully explained by the synergistic interaction of the nZVI core and manganese oxide shell, in which the manganese oxides participate in oxidation reactions with corroded Fe and subsequently retard the release of aqueous iron providing additional surface sites for arsenic adsorption. In summary, this study reports the successful fabrication of a core/shell nZVI/Mn oxide as an effective adsorbent for the removal of arsenic from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this study, nano zero valent iron (NZVI) modified MCM-41-zeolite A (Fe-MCM-41-A) composite as a novel adsorbent was prepared by precipitation method and applied for tetracycline (TC) removal from aqueous solution. The adsorbent was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and N 2 -BET analysis. Hysteresis loops indicated that the sample has a desirable magnetic property and can be separated quickly. Adsorption studies were carried out to evaluate its potential for TC removal. Results showed that the optimal Fe-MCM-41-A dosage, initial pH and reaction time at initial TC concentration of 100 mg L −1 solution are 1 g L −1 , pH = 5, and 60 min respectively, at which the removal efficiency of TC was 98.7%. The TC adsorption results fitted the Langmuir isotherm model very well and the adsorption process could be described by a pseudo-second-order kinetic model. A maximum TC adsorption capacity of 526.32 mg g −1 was achieved. This study demonstrates that Fe-MCM-41-A is a promising and efficient material for TC adsorption from aqueous solution. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) is extensively used as a peroxymonosulfate (PMS) activator but suffers from the ease of oxidation and agglomeration due to its high surface energy and inherent magnetism. Here, green and sustainable yeast was selected as a support material to firstly in-situ prepare yeast-supported Fe0@Fe 2 O 3 and used for activating PMS to degrade tetracycline hydrochloride (TCH), one of the common antibiotics. Due to the anti-oxidation ability of the Fe 2 O 3 shell and the support effect of yeast, the prepared Fe0@Fe 2 O 3 /YC exhibited a superior catalytic activity for the removal of TCH as well as some other typical refractory contaminants. The chemical quenching experiments and EPR results demonstrated SO 4 •− was the main reactive oxygen species while O 2 •−, 1O 2 and •OH played a minor role. Importantly, the crucial role of the Fe2+/Fe3+ cycle promoted by the Fe0 core and surface iron hydroxyl species in PMS activation was elucidated in detail. The TCH degradation pathways were proposed by LC-MS and density functional theory (DFT) calculation. In addition, the outstanding magnetic separation property, anti-oxidation ability, and high environmental resistance of the catalyst were demonstrated. Our work may inspire the development of green, efficient, and robust nZVI-based materials for wastewater treatment. [Display omitted] • Yeast-supported Fe0@Fe 2 O 3 was firstly prepared and used for peroxymonosulfate (PMS) activation and tetracycline hydrochloride (TCH) degradation. • SO 4.•− was the main reactive oxygen species while O 2 •−, 1O 2 and •OH played a minor role. • The crucial role of the Fe2+/Fe3+ cycle promoted by Fe0 core and surface iron hydroxyl species in PMS activation was elucidated in detail. • The outstanding magnetic separation property, anti-oxidation ability and high environmental resistance of the catalyst were also demonstrated. [ABSTRACT FROM AUTHOR]

• The bimetallic Cu-, Ag- or Cr-nZVI was prepared with the impregnation method; • XANES/EXAFS provide bonding distance and coordination number of metal loaded nZVI; • Thermal effects on radius and thickness of core-shell sphere nZVI were demonstrated by SAXS; • Comparison of degradation efficiency of p-nitrophenol (4-NP) into aminophenol (4-AP) is Cu- > Ag- > Cr-coated nZVI; • The reductive reaction mechanisms of 4-NP degradation and Cu ion adsorption onto nZVI are proposed. p-Nitrophenol (4-NP) is an organic pollutant found in wastewater discharged from agricultural facilities worldwide. This pollutant is considered as hazardous and toxic by the US Environmental Protection Agency (USEPA). The spherical chain-shaped nanophase zero-valent-iron (nZVI) with different metal (Ag, Cr, Cu) loadings was used for wastewater simulation to form bimetallic nanocatalyst (BNC). Moreover, the nZVI and BNC was synthesized and characterized for 4-NP removal. The as-synthesized nZVI and BNCs were used to degrade 4-NP in wastewater, where a higher conversion of 4-NP to aminophenol (4-AP) was observed. The core-shell shape of nZVI@Cu BNCs was also investigated with small angle X-ray scattering (SAXS) to demonstrate the parameters of core-shell model in SAS View. Experimentally, the Cu removal efficiencies at different loading ratios were nZVI@Cu-800> nZVI@Cu-400> nZVI@Cu-200> nZVI@Cu-100. The thermal induced aggregations of nZVI were demonstrated with SAXS, where the 55 °C group displayed 181% increase in size when compared with the 25 °C group. The XANES/EXAFS spectra revealed the presence of Cu 2 O in nZVI@Cu, a phenomenon which provided the reductive degradation mechanism of the chemical reactions. In this study, heavy metal absorbed onto nZVI and BNCs reduced 4-NP heavy metal contaminants to less toxic 4-AP. Thus, the as-synthesized nZVIs could effectively convert harmful 4-NP in wastewater into useful and high-value 4-AP by-products. [Display omitted] [ABSTRACT FROM AUTHOR]

Nano zero-valent iron has drawn great attention for the degradation of organic dyes due to its high reactivity, large specific surface area, lightweight, and magnetism. However, the aggregation and passivation of iron nanoparticles may prohibit the wide use of it. A new composite material was prepared by loading nano zero-valent iron (nZVI) on montmorillonite (MMT) to overcome the above shortcomings and it was further used for the removal of Rhodamine 6G (Rh 6G) under microwave treatment in the present work. The effects of various parameters, including the initial concentration of Rh 6G, microwave power, and pH value were investigated. The new composite material (nZVI/MMT) showed an excellent degradation ability for removing Rh 6G, and the removal amount reached 500 mg/g within 15 min. The degradation rate reached 0.4365 min−1, significantly higher than most previous reports using other removal methods for Rh 6G.

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Monoethanolamine (shortly ethanolamine (ETA)), usually used as a corrosion inhibitor, is a contaminant of wastewater from the secondary cooling system of nuclear power plants (NPPs) and is not readily biodegradable. We conducted various experiments, including treatments with nano zero-valent iron (nZVI), nano-iron/calcium, and calcium oxide (nFe/Ca/CaO) with ozone (O) or hydrogen peroxide (HO) to reduce the concentration of ETA and to decrease the chemical demand of oxygen (COD) of these wastewaters. During this study, wastewater with ETA concentration of 7465 mg L and COD of 6920 mg L was used. As a result, the ETA concentration was reduced to 5 mg L (a decrease of almost 100%) and COD was reduced to 2260 mg L, a reduction of 67%, using doses of 26.8 mM of nZVI and 1.5 mM of HO at pH 3 for 3 h. Further treatment for 48 h allowed a decrease of COD by almost 97%. Some mechanistic considerations are proposed in order to explain the degradation pathway. The developed hybrid nano zero-valent iron-initiated oxidation process with HO is promising in the treatment of ETA-contaminated wastewaters. [ABSTRACT FROM AUTHOR]