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This study aims to develop three-dimension reduced graphene oxide aerogel supported nano zero-valent iron (rGOA-nZVI) by hydrothermal and liquid phase reduction approach and applies it to the removal of two typical dyes, methylene blue (MB) and methyl orange (MO) from aqueous solutions. The obtained magnetic rGOA-nZVI composites were characterized by scanning electron microscopy (SEM), atomic force microscopy, Brunauer-Emmett-Teller, X-ray diffraction and Fourier transform infrared spectroscopy, and its removal efficiencies for MB and MO from aqueous solutions were evaluated. The removal processes of MB and MO could be completed within 30 min, which were well described by the pseudo-second order kinetic model. The rGOA-nZVI nanocomposites exhibited remarkable performance for the removal of MB (the maximum adsorption amount, qmax = 3918 mg/g) and MO (qmax = 667 mg/g) in a wide pH range (pH 1.0-10.0). Furthermore, rGOA-nZVI is stable and recyclable with high dye removal efficiencies (> 90%) after five cycles. The removal mechanisms were demonstrated with SEM and XRD analyses before and after MB and MO removal. This study showed that rGOA acts as an excellent carrier for nZVI, and the rGOA-nZVI nanocomposites are efficient materials for the advanced treatment of dye wastewater over a wide pH range. [ABSTRACT FROM AUTHOR]

Introduction: Crude oil and petroleum hydrocarbon contamination is commonly found in the soil and groundwater during the various processes of mining, processing, and utilization due to issues such as inefficient environmental management, random wastewater discharge, and storage tank leakage.To address this issue, we will use corn stalk biochar (SBC) and surfactants to improve the stability and chemical reactivity of nZVI, thereby enhancing its ability to remove pollutants, and explore the adsorption effect and mechanism of composite materials for petroleum hydrocarbons.Methods: Modified corn stalk biochar (SBC) was synthesized through high-temperature carbonization and KOH activation. Subsequently, the iron/carbon composite PN-nZVI@SBC (PNMSBC) was prepared by loading nano zero-valent iron modified with dual surfactants, and it was adopted to adsorb total petroleum hydrocarbons(TPH) in groundwater. The physical and chemical properties, surface patterns, and elemental mapping of PNMSBC particles were analyzed using SEM, EDS, TEM,XRD, BET, and FTIR spectroscopy. Kinetics and isotherm tests were performed to evaluate the adsorption properties of the composites. TPH adsorption was dependent on ionic strength, initial TPH concentration, as well as pH. The adsorption mechanism combining XPS and EPR spectroscopy was explored.Results: The characterization results by SEM and TEM showed that the particle size of nZVI particles modified by surfactants became smaller, and the dispersibility was enhanced. The characterization results by XRD and FTIR confirmed the successful preparation of the composites. The BET results showed that MSBC and PNMSBC were mesoporous structures. The characterization results indicated that Polyvinylpyrrolidone (PVP) and Sodium oleate (NaOA) inhibited the oxidation of nZVI while effectively improving its reactivity. The result of the experiments on adsorption showed that the removal of TPH by PNMSBC followed Freundlich isotherm and pseudo-second-order kinetic models, thus suggesting that the main adsorption processes comprise chemisorption and multilayer heterogeneous adsorption. The adsorption capacity of PNMSBC was increased by the abundance of macro and microporous structures. To be specific, a maximum Langmuir adsorption capacity (qm) was achieved as 75.26 g/g. The result of batch experiments indicated that PNMSBC continuously removed considerable TPH under a wide pH range from 2 to 6. The adsorption mechanism of PNMSBC includes surface adsorption, oxidation, complexation, and electrostatic interaction.Discussion: In brief, PNMSBC has a promising application for the adsorption of TPH in groundwater remediation.

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Nowadays, antibiotics are extensively used in human and animal medicine. The unconscious consumption of antibiotics and their mixing with water sources without adequate treatment have caused environmental problems. Several chemical and physical treatment methods applied for the removal of antibiotics from aqueous media offer alternative solutions by improving the treatment process and using new materials. As in many areas, nanomaterials are also used in treatment methods such as sorption, degradation, and oxidation. Among the nanomaterials, nano zero-valent iron (nZVI) is frequently preferred in treatment processes due to its abundance, cheapness, ease of application, and high removal performance. Besides its many advantages, nZVI agglomerates in the aqueous phase and exhibits unstable behaviors. This limits the surface area required for antibiotic removal and reduces the removal efficiency. In recent years nZVI has been used in water treatment technologies by being modified with many support materials such as bentonite to minimize particle agglomeration. Bentonite is clay-based support material that provides high removal efficiency and reduces the cost of treatment due to its abundance in nature. In this study, antibiotic pollution and treatment methods in water resources were reviewed and the antibiotic removal performances of bentonite-supported nVZI were investigated. In the studies, it was concluded that the antibiotic removal efficiency increased with the use of support materials.

Biochar prepared by thermal decomposition of sewage sludge is a new adsorbent for sludge resource utilization and aquatic environmental treatment. In this study, sewage sludge was used as raw material for the preparation of pyrolysis sludge-based biochar. In addition, montmorillonite (Mt) and nano zero-valent iron (nZVI) were used to modify sludge-based biochar in different combinations to improve its adsorption capacity of nitrogen and phosphorus in water, and the best modification scheme was selected. The physicochemical properties of the biochar were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that Mt and nZVI could improve the specific surface area and enrich the surface functional groups. The results on kinetics and equilibrium isotherms showed that sludge-based biochar modified by Mt coupled with nZVI (nZVI@MBC) had the best adsorption effect on NH4+ and PO43−. And its theoretical maximum saturation adsorption capacity for NH4+ and PO43− was 34.84 mg·g−1 and 294.12 mg·g−1, respectively. Our results were in the forefront of existing literature on modified sludge-based biochar. The adsorption mechanisms of nZVI@MBC for NH4+ and PO43− mainly include ligand exchange, electrostatic attraction and ionic bond. In addition, nZVI@MBC can also remove PO43− by chemical precipitation and coprecipitation of iron corrosion products. HIGHLIGHTS Preparing a sludge-based biochar modified by Mt coupled with nZVI.; nZVI@MBC has excellent adsorptive capacity for NH4+ and PO43−.; Mt can greatly improve the cation exchange capacity of nZVI@MBC due to its unique structure.; nZVI increased the adsorption site and reactivity of nZVI@MBC, and can be precipitated with PO43−.; The presence of BC and Mt alleviates the defect of easy agglomeration passivation of nZVI in water.;

Nowadays, antibiotics are extensively used in human and animal medicine. The unconscious consumption of antibiotics and their mixing with water sources without adequate treatment have caused environmental problems. Several chemical and physical treatment methods applied for the removal of antibiotics from aqueous media offer alternative solutions by improving the treatment process and using new materials. As in many areas, nanomaterials are also used in treatment methods such as sorption, degradation, and oxidation. Among the nanomaterials, nano zero-valent iron (nZVI) is frequently preferred in treatment processes due to its abundance, cheapness, ease of application, and high removal performance. Besides its many advantages, nZVI agglomerates in the aqueous phase and exhibits unstable behaviors. This limits the surface area required for antibiotic removal and reduces the removal efficiency. In recent years, nZVI has been used in water treatment technologies by being modified with many support materials such as bentonite to minimize particle agglomeration. Bentonite is clay-based support material that provides high removal efficiency and reduces the cost of treatment due to its abundance in nature. In this study, antibiotic pollution and treatment methods in water resources were reviewed and the antibiotic removal performances of bentonite-supported nZVI were investigated. In the studies, it was concluded that the antibiotic removal efficiency increased with the use of support materials. [ABSTRACT FROM AUTHOR]

Carbonized bacterial cellulose embedded with highly dispersed nano zero-valent iron (nZVI), denoted as nZVI@CBC, was prepared through one-step in situ carbothermal treatment of bacterial cellulose adsorbing iron(III) nitrate. The structure characteristics of nZVI@CBC and its performance in removing hexavalent chromium Cr(VI) were investigated. Results showed the formation of nZVI@CBC with a surface area of 409.61 m2/g at 800 °C, with nZVI particles of mean size 28.2 nm well distributed within the fibrous network of CBC. The stability of nZVI was enhanced by its carbon coating, despite some inevitable oxidation of exposed nZVI. Batch experiments demonstrated that nZVI@CBC exhibited superior removal efficiency compared to bare nZVI and CBC. Under optimal conditions, nZVI@CBC exhibited a high Cr(VI) adsorption capacity of up to 372.42 mg/g. Therefore, nZVI@CBC shows promise as an effective adsorbent for remediating Cr(VI) pollution in water. • Carbonized bacterial cellulose embedded with nZVI was prepared. • The nZVI@CBC is a coating structure, which shows enhanced stability against oxidation. • Cr(VI) removal on nZVI@CBC was much higher than that on CBC and nZVI. • The maximum adsorption capacity toward Cr(VI) was up to 372.42 mg/g under optimal conditions. • The adsorption and reduction were responsible for Cr(VI) adsorption. [ABSTRACT FROM AUTHOR]

In the present study, attapulgite (ATP)-maintained nanoscale zero-valent iron (nZVI) at different Fe/ATP mass ratios (1:3 and 1:5) was synthesized by liquid phase reduction for its use to remove chromium Cr(VI) in aqueous solution. The morphology, crystalline structure, chemical composition, and valent states of these nZVI/ATP composites were evaluated before and after the reaction. Obtained characterization data indicated an effective dispersion of nZVI on ATP surface, preventing the agglomeration of nZVI particles. Results showed that the introduction of ATP has higher Cr(VI) removal efficacy as compared to the bare nZVI or ATP. At Cr(VI) initial level of 40 mg L−1, the remediation efficacy of Cr(VI) in nZVI/ATP(1:3) reached 91.63%, which was substantially higher than that of bare nZVI (48.68%) and ATP (2.52%). Co-precipitation and reduction of Cr-containing metal deposited onto nZVI/ATP were found as the major reaction mechanisms. At lower initial level of Cr(VI) (20 mg L−1), the reduction was the dominant process where Fe(II) was the major form of iron in the reaction product. However, adsorption was the major mechanism at higher initial level of Cr(VI) (100 mg L−1) whereas the reaction product mainly comprised the ferric form of iron (Fe(III). The main reaction product was the FeCr2O4 under low or high Cr(VI) concentrations which can reduce the risk of secondary pollution because of its high stability. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) coated with magnetite and an imidazolium-based ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6)) core/shell nanoparticles (NPs) (nZVI@Fe3O4@HMIMPF6) were successfully green synthesized for the first time using industrial iron waste. Polyphenols were extracted from dried leaves of Camellia sinensis and applied as the reducing agent for nZVI synthesis. Synthesized NPs were characterized by FT-IR, XRD, VSM, BET, SEM, TEM, and mapping analysis. According to the results, NPs were in the size range of less than 30 nm and the values of a s , BET = 3.5975 m 2 g - 1 , V m (BET monolayer capacity) = 0.8265 cm 3 STP g - 1 , C = 47.378, total pore volume ( p p 0 = 0.990) = 0.14998 cm 3 g - 1 and mean pore diameter = 16.68 nm were obtained. These NPs were used for the Cr (VI) removal from aqueous samples. Taguchi orthogonal array design was used to optimize the various affecting variables on the efficiency of Cr (VI) removal. Results showed that about 90.0% of Cr (VI) were removed at the optimum conditions. Kinetic and isotherm studies were conducted, and the pseudo-second order kinetic model was determined as the most appropriate kinetic model. The equilibrium data displayed proper linearity with the Freundlich isotherm model (R2 = 0.9697), and the maximum adsorption capacity was found to be 56.49 mg g - 1 (in terms of CrO42− ions). Also, Redlich-Peterson, Sips, and Toth as three-parameter isotherm models were compared to two-parameter models using MATLAB's fmincon function. Thermodynamic studies showed negative ΔG°, ΔH° = 50.255 kJ mol−1, and ΔS° = + 0.1799 kJ mol−1 K−1 indicating spontaneous and endothermic adsorption process. According to the results, the nZVI @ Fe 3 O 4 @ IL NPs can be recovered by an external magnet and exhibit good applicability for Cr (VI) removal from real samples. Article Highlights: Core-shell structures of nZVI @ Fe 3 O 4 @ IL were synthesized for the first time Steel slag and waste rusted iron shavings were used as ferrous ion sources Polyphenols were extracted fromCamellia sinensisand used for biosynthesis of nZVI The obtained NPs were used for the removal of Cr (VI) ions from aqueous samples Two and three parameter isotherm models, kinetic and thermodynamic studies were investigated [ABSTRACT FROM AUTHOR]

In this study, the reduction of the chemical oxygen demand (COD) for the wastewater contaminated by phenolic compounds was investigated using three techniques: batch adsorption, electrochemical processing, and adding a granular third electrode (GTE) to an electrochemical process. The COD removal rate of the simulated phenolic wastewater with a phenol concentration range from 500 to 1,500 mg/L was measured. The actual samples from the Al-Daura Refinery (Iraq) oil refinery wastewater (ORW) were examined as a case study. Adsorption was conducted with either nanoparticle zero-valent iron (nFe0) or silty clay-supported for nFe0 (SC-nFe0) as an efficient adsorbent. The electrochemical process and electrochemical process with nFe0 or SC-nFe0 as a GTE were also investigated. The influences of various parameters (e.g., time, pH, nFe0 and SC-nFe0 dose, phenol concentration, temperature, current density, and electrode distance) were examined to determine the optimal operating conditions of each process. The maximum removal rate of the COD in adsorption with nFe0 and SC-nFe0 was 89.5% and 84.2%, respectively. When using the electrochemical process and GTE in an electrochemical process with nFe0 or SC-nFe0, the maximum removal rates were 79.8%, 93% and 94%, respectively. All of the proposed processes achieved an excellent COD removal rate when applied to actual petroleum refinery wastewater and rates higher than those attained in the refinery wastewater treatment plant. [ABSTRACT FROM AUTHOR]

• Porous and high specific area bone char-supported zero-valent iron was synthesized. • BC exhibits a stronger ability in promotingprom nZVI for Cr(VI) removal compared to biochar and activated carbon. • BC enhances nZVI to remediate Cr(VI) contamination in waters and soils. • Reduction and coprecipitation are the dominant Cr(VI) removal mechanisms. 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. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • FF removal by nZVI-AC was dominated by adsorptive and reductive reaction. • Strong synergistic effect between AC and nZVI accelerated electron transfer towards adsorbed FF. • FF was adsorbed onto nZVI-AC mainly through hydrogen bonding, π–π interactions and π–π EDA interaction. • nZVI-AC was superior efficient in detoxifying FF. Antibiotics, especially halogenated antibiotics, inevitably discharged into environment are of great concern worldwide. Nanoscale zerovalent iron (nZVI)-based materials have been promising for the removal of halogenated antibiotics, but their susceptibility to oxidation and aggregation badly limits their application. Herein, activated carbon (AC)-supported nZVI (nZVI-AC) was synthesized to remove florfenicol (FF), a widely used broad-spectrum halogenated antibiotic, under ambient conditions. nZVI-AC had the strongest adsorption affinity to FF and most conductive to FF, and the reaction rate constant (k 1) of FF removal by nZVI-AC (0.320 min−1) was increased by 106.7 times with the support of AC (0.003 min−1). Freundlich and DA models showed good fits for FF adsorption by nZVI-AC, and hydrogen bonding, van der Waals forces and chemisorption were the dominant mechanisms for FF adsorption. The van der Waals forces and chemisorption contributed to the enhanced adsorption capacity of the composite system, and the strong synergistic effect of AC and nZVI in nZVI-AC accelerated electron transfer towards adsorbed FF, thus facilitating the further dehalogenation. The removal of FF by nZVI-AC was dependent on solution pH and CrO 4 2− concentrations, and suppressed by humic acid, while barely affected by Cd2+. Escherichia coli survival assessment and theoretical simulation evaluation demonstrated the superior efficacy of nZVI-AC in detoxifying FF with the detection of non-toxic FF intermediates. By comprehensively analyzing the environmental factors, removal mechanisms and potential degradation pathways of FF treated by nZVI-AC, this study provides further insights into the risk assessment of intermediates and their toxicity, assigning new perspectives for practical application of nZVI-based technologies to efficiently remove the amount and also reduce the toxicity of FF and other emerging contaminants in water. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) particles have been identified as one of the potential candidate for the removal of various metal ions. This study addresses the effectiveness of nZVI on iron removal from an aqueous solution containing Fe2+/Fe3+ in the ratio of 2.5:0.5, which is not studied so far. Liquid-phase reduction technique was utilized to synthesize the nZVI. The characterization of nZVI and its interaction with iron in aqueous solution was found using transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive X-ray (SEM–EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV–Vis spectroscopy) and Fourier transform infrared spectroscopy (FTIR). It was found that the nZVI particles were largely spherical with size varying from 80–99 nm. Abundant oxygen functional groups detected in the FTIR spectrum serve as the accessible sites for iron adsorption. SEM and XRD studies provided a clear image of core-shell structure of nZVI. The study also investigated the role of pH, iron concentration, nZVI dosage and contact time on the uptake behaviour of contaminant iron. A removal efficiency of 63% was achieved in 3 h, with optimum nZVI loading of 5 g l−1, from a solution having initial iron concentration of 0.5 mg l−1 at natural solution pH 6.85. This efficiency was increased to 70% at optimum pH 10. The batch study revealed that adsorption kinetics followed pseudo-second-order kinetics with R2 value of 0.99 and data followed Dubinin–Radushkevich isotherm. Outcomes of the study recommend that nZVI could turn into a promising adsorbent for iron removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

This research investigates the adsorption capacity of a novel composite material, namely nano zero-valent iron coated coffee grounds (nZVI-CG), for removal of zinc (Zn) and nickel (Ni). nZVI particles were synthesized and immobilized to the surface of waste coffee grounds (CG) using the ultrasonic-assisted liquid phase method. Characterization of synthesized nZVI-CG composite and bare CG showed that nZVI coating has increased the surface area significantly. Batch tests were conducted to examine the effects of pH, reaction time and initial metal concentrations on Zn2+ and Ni2+ removal. At an initial metal concentration of 10 mg-Ni/L and 10 mg-Zn/L, nZVI-CG removal rates for Zn2+ and Ni2+ were observed as 98.89% and 97.29%, respectively; while removal rates of bare CG have remained at 51% (Zn2+) and 48.1% (Ni2+). Moreover, acidic conditions were observed to deteriorate Ni2+ and Zn2+ adsorption since most functional groups of the metals were protonated. Increasing initial nickel and zinc concentrations decreased removal rates. While the model fittings improved with increasing pH, in the case of nZVI-CG, Langmuir isotherm gave the best fits for Ni2+ and Zn2+ at pH 5 and 7. Also, our experimental results followed the pseudo-second-order kinetic model, regardless of the used adsorbent. Consequently, our results showed that nZVI-CG composite material is a promising alternative adsorbent for pilot scale metal removal/recovery applications. [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]

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]

Nano zero-valent iron (NZVI) particles were prone to forming aggregates owing to their intrinsic magnetism and van der Waals force. In this work, a composite material containing mesoporous silica MCM-41 and NZVI was prepared to avoid the problem of NZVI aggregation. The structures and morphologies of the as-prepared composite were confirmed using X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, N2adsorption–desorption, and X-ray photoelectron spectroscopy techniques. It was found that NZVI particles were well dispersed in the composite, although the size of NZVI particle was larger than that of bare NZVI. Moreover, the composite was used as adsorbent for removing Pb(II) from aqueous solution at room temperature. The effects of contact time, initial solution pH, and adsorbent dosage on the removal efficiency of Pb(II) were studied using batch adsorption experiments. The results indicated the composite exhibited enhanced adsorption properties, with the maximum adsorption capacity of 416.17 mg/g for Pb(II) removal from aqueous solution. In addition, the adsorption isotherms and adsorption kinetics were also investigated systematically, it was found that the isothermal data were well fitted to Langmuir model, and the kinetic data were well suitable to pseudo-second-order kinetics model. [ABSTRACT FROM PUBLISHER]

Encapsulating nano zero-valent iron particles with biomass-derived carbon is a promising strategy to achieve efficient uranium extraction by avoiding agglomeration and oxidation of nano zero-valent iron. Herein, we develop distinctive carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel for reduction-assisted uranium extraction. The nano zero-valent iron particles encapsulated in konjac glucomannan-derived carbon are composed of γ-Fe and a small part of α-Fe, in which γ-Fe with a stable carbon shell reduces the passivation rate, and the konjac glucomannan-derived carbon support prevents the nano zero-valent iron particles from agglomerating. U(VI) enrichment ratio via carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel reached up to 90.1% within 60 min in 200 mg/L uranium-containing wastewater, with U(VI) enrichment capacity of 720.8 mg/g. The mechanistic research revealed the oxygen-containing functional groups on konjac glucomannan-derived carbon confine UO 2 2+, electrons on the nano zero-valent iron particles further transferred to konjac glucomannan-derived carbon, thereby realizing the reduction and fixation of uranium. Carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel can be a promising adsorption-reduction coupling material for multi-environment systems, providing a successful example for the purification of uranium-containing wastewater. [Display omitted] • Bio-assembly technology improved nZVI particles dispersibility. • KGMC encapsulated carbon-coated nZVI particles to enhance the stability of nZVI. • Fast adsorption kinetics: 75.7% removal efficiency was achieved in 10 min. • The presence of coexisting ions and organics scarcely affected the enrichment of uranium by nZVI@KGMC. [ABSTRACT FROM AUTHOR]

In this study, a series of chitosan-stabilized nano zero-valent iron (CNZVI) composites with different amounts of chitosan were prepared and characterized by Fourier transform infrared spectra, X-ray diffraction, and transmission electron microscopy. The adsorption capacity of these composites was evaluated by the removal experiment of cadmium ion (Cd2+) from aqueous solution. These results showed that the as-prepared CNZVI8composite with loose aggregate structure has the maximum adsorption capacity for Cd2+. Furthermore, batch adsorption experiments of Cd2+on CNZVI8composite were performed under various conditions, such as contact time, adsorbent dosage, initial Cd2+concentration, and the initial pH of solution. The data revealed that the maximum adsorption capacity of CNZVI8is 124.74 mg/g. The removal efficiency of Cd2+increased with the increase in solution pH value, and reaches 99.9% at pH 6. In addition, the adsorption isotherm and the adsorption kinetics of Cd2+on CNZVI8were also investigated, suggesting that the isothermal data were well fitted to the Langmuir model and the kinetic data were well suitable to the pseudo-second-order kinetic model. [ABSTRACT FROM PUBLISHER]

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]