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Tetracycline (TC) contamination in water is one of the key issues in global environmental protection, and traditional water treatment methods are difficult to remove antibiotic pollutants.Therefore, efficient and environmentally friendly treatment technologies are urgently needed. In this study, activated persulfate (PS) using a biochar-loaded nano zero-valent iron (BC-nZVI) advanced oxidation system was used to investigate the degradation effect, influencing factors, and mechanism of TC. BC-nZVI was prepared using the liquid-phase reduction method, and its structure and properties were analyzed by various characterization means. The results showed that nZVI was uniformly distributed on the surface or in the pores of BC, forming a stable complex. Degradation experiments showed that the BC-nZVI/PS system could degrade TC up to 99.57% under optimal conditions. The experiments under different conditions revealed that the iron-carbon ratio, dosing amount, PS concentration, and pH value all affected the degradation efficiency. Free radical burst and electron paramagnetic resonance (EPR) experiments confirmed the dominant roles of hydroxyl and sulfate radicals in the degradation process, and LC–MS experiments revealed the multi-step reaction process of TC degradation. This study provides a scientific basis for the efficient treatment of TC pollution in water. [ABSTRACT FROM AUTHOR]

A facile strategy to construct superhydrophobic coatings was carried out by one‐pot process using novel nano zero‐valent iron and hydrogen peroxide as trigger in ethanol and Tris buffer mixed system containing dopamine and 1H,1H,2H,2H‐perfluorodecanethiol (PFDT) for the first time. The polydopamine (PDA) modified by PFDT composite coating can be deposited onto various substrates including glass slides, polyurethane sheets, polytetrafluoroethylene wafers, 304 stainless steel sheets, and polyurethane sponges, revealing excellent hydrophobicity with the water contact angles from 157.1° to 162.2° and the sliding angle lower than 1°. The flourier transformed infrared spectroscopy and x‐ray photoelectron spectroscopy information of the composite coating demonstrated the successful covalent interaction between catechol group in PDA and thiol group of PFDT via Michael addition reaction. As‐prepared PFDT/PDA composite coatings exhibited enhanced chemical stability in highly acidic solutions for 6 days, alkaline aqueous solutions for 5 days, salty solutions (3.5 wt%) for 28 days, and polar organic solvents for 24 h, respectively, as well as resistance to algae adhesion. The excellent corrosion resistance and chemical stability of the composite coating and their simple, time saving and inexpensive construction process are expected to be widely applied in various areas, including marine anti‐corrosion, anti‐fouling, and oil–water separation. [ABSTRACT FROM AUTHOR]

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Today, new energy sources alternative to fossil fuels are needed to meet the increasing energy demand. It is becoming increasingly important to constitute new energy sources from waste biomass through the liquefaction process. In this study, walnut shells (WS) were liquefied catalytically and non-catalytically under different parameters using the liquefaction method. In this process, the effect of silica fume/nano zero-valent iron (SF/NZVI) catalysts on the conversion rates was investigated. The catalyst was synthesized by reducing NZVI using a liquid phase chemical reduction method on SF. The SF/NZVI catalyst was characterized by scanning electron microscopy- energy dispersive X-ray (SEM–EDX), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The effect of various process parameters on the liquefaction process was investigated. In this context, the reaction temperature ranged from 300 to 400 °C, the solid/solvent ratio ranged from 1/1 to 1/3, the reaction time ranged from 30 to 90 min, and the catalyst concentration ranged from 1 to 6%. According to the results obtained, the most suitable operating conditions for non-catalytic experiments in liquefaction of WS were found to be temperature of 400 °C, reaction time of 60 min, and solid/solvent of 1/3. In catalytic conditions, the optimum values were obtained as temperature of 375 °C, reaction time of 60 min, solid/solvent ratio of 1/3, and catalyst concentration of 6%. The highest total conversion and (oil + gas) % conversion were 90.4% and 46.7% under non-catalytic conditions and 90.7% and 62.3% under catalytic conditions, respectively. Gas chromatography/mass spectrometry (GC/MS) analysis revealed the bio-oil was mainly composed of aromatic compounds (benzene, butyl-, indane and their derivatives,) and polyaromatic compounds (naphthalene, decahydro-, cis-, naphthalene, 1-methyl-.). The aim of increasing the quantity and quality of the light liquid product in the study has been achieved. [ABSTRACT FROM AUTHOR]

Aggregation and sharp reactivity decrease are the key problems of using nano zero-valent iron (nZVI) as a potential reaction medium for a permeable reactive barrier (PRB). In this study, nZVI particles encapsulated within an acrylonitrile–butadiene–styrene (ABS) matrix (nZVI/(ABS + EC)) was fabricated, which for the first time successfully simultaneously solved the above problems via accurately regulating the distribution of nZVI particles in the ABS matrix and regulating the contact between nZVI particles and the contaminated aqueous environment. In addition, the size and number of the pores throughout the ABS matrix were first regulated by ethyl cellulose (EC) for the purpose of controlling the contact between nZVI particles and the nitrate contaminant, affording apparent rate constants (kobs) for denitrification performance in the range of 0.0423 to 0.0820 min−1. The remediation of simulated nitrate-contaminated solution by nZVI/(ABS + EC) was suitably described by the first-order kinetics model, with kobs ranging from 0.0423 to 0.2036 min−1, and functional relationship models of kobs with the dosages of EC (dEC) and nZVI (dFe) during encapsulation were developed for the quantitative regulation of a sustainable denitrification performance. Results revealed that encapsulation prevents the aggregation of nZVI, rendering a sustainable denitrification performance of the material; the denitrification performance was demonstrated to be affected and quantitatively regulated by the encapsulation and application conditions. Using nZVI/(ABS + EC) as the reaction medium for PRB, the pore blocking of PRB can be avoided, and the sustainable remediation performance can be quantitatively regulated and predicted. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron（nZVI） is a kind of widely-concerned environmental remediation material，which expands the application scope of iron-based materials in site remediation and pollutant removal because it has both the reactive activity of nanoscale materials and the reductive property of zero-valent iron. Although nZVI is more effective，the more complex preparation process leads to increased environmental footprint and production costs，the preparation method of nZVI is becoming a key constraint to its development. The paper introduced the development of nZVI and carded the various preparation methods and characteristics of nZVI from the perspective of sustainable development. Furthermore，this paper examined the potential environmental consequences resulting from the preparation process of nZVI. On this basis，the sustainability of typical nZVI preparation was assessed，and potential unsustainable factors were quantified，highlighting the dependence of the preparation process on electrical energy sources. Based on the existing researching，the large-scale and potential methods of preparation of nZVI were prospected，such as laser ablation. Moreover，it illustrated the importance of choosing reasonable preparation method，emphasizing the indispensable position of the sustainability assessment of nZVI in the future development. It is hoped to provide a reference for researchers and policy makers in the selection and improvement of nZVI preparation methods.

Nano zero-valent iron (nZVI) has problems such as agglomeration, passivation and poor transportability, which affect the in situ remediation effect of Cr(VI) contaminated groundwater. To develop a low-cost, green nZVI modified material, a low-cost, green modification for nZVI was developed. The nZVI@BC reaction system was constructed by supporting nZVI with ball-milled biochar (BC) as carrier and then stabilized with carboxymethyl cellulose (CMC). CMC-nZVI@BC was synthesized as a novel high-efficiency, anti-passivation nano-scale remediation material. The nZVI before and after modification was characterized and analyzed, and the effects of CMC-nZVI@BC addition, initial concentration of Cr(VI), pH and temperature and chemical fraction of groundwater on the removal of Cr(VI) by CMC-nZVI@BC were investigated, and the mechanism of Cr(VI) removal by CMC-nZVI@BC was elucidated, and the following conclusions were obtained: (1) The best removal of Cr(VI) by nZVI@BC at the Fe and C mass ratio of 2∶1； the removal rate of 50 mg/L Cr(VI) by 0.6 g/L CMC-nZVI@BC within 3 h reached 99.9%, exhibiting a high removal rate and capacity of Cr(VI). (2) The main mechanism of Cr(VI) removal by CMC-nZVI@BC was reduction and precipitation. (3) In the range of 2 to 10, the pH value had a significant effect on the removal of Cr(VI) by CMC-nZVI@BC, with less effect of temperature. (4) The presence of \begin{document}${\mathrm{SO}}_4^{2-} $\end{document} promoted Cr(VI) removal, while \begin{document}${\mathrm{HCO}}_3^{-} $\end{document}, \begin{document}${\mathrm{NO}}_3^{-} $\end{document}, Ca2+, Mg2+ and humic acid, all had different degrees of inhibition on Cr(VI) removal. These results suggest that CMC-nZVI@BC can be an effective in situ remediation agent for Cr(VI) removal, offering the possibility of applying nZVI for in situ groundwater remediation.

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The aggregation of nanoscale zero-valent iron (NZVI) is one of the biggest challenges for its application when treating contaminants in aquatic environment. We report a study on synthesis of sodium carbonate-modified biochar (BC-600) combined with sodium alginate (SA)-modified NZVI (SA/NZVI@BC-600) for the removal of tetracycline (TC). When the initial concentration of TC was 20 mg/L, 100% TC was removed by SA/NZVI@BC-600 at an initial pH of 7 under room temperature of 25 °C within 90 min. In addition, the reactivity of the SA/NZVI@BC-600 composites toward TC removal was not obviously declined after 4 cycles. SA/NZVI@BC-600 shows high reactivity, stability, and reusability. This excellent performance of SA/NZVI@BC-600 was related to the addition of SA and BC-600. The best performance of the SA/NZVI@BC-600 system was observed under weakly acidic and neutral conditions. Increasing the initial concentration and lowering the reaction temperature had a slight negative effect on the removal of TC by SA/NZVI@BC-600. In addition, the presence of CO32− and HCO3− had a significant negative effect on the degradation of TC. Meanwhile, ·OH and ·O2− played the leading role in TC degradation. This study not only reported a novel strategy of synthesizing an excellent BC modified NZVI based catalyst but also evaluated its promising application for antibiotic degradation in aqueous solution. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alteration of wet and dry periods affects soil geochemical properties that drive contaminant availability and mobility. Consequently, the efficiency of soil remediation may vary, and thus soil management needs to consider these variations. This study reveals the effect of soil moisture manipulation on the behaviour of the toxic metalloids antimony (Sb) and arsenic (As) and the immobilisation efficiency of nanoscale zero-valent iron (nZVI), biochar (BC) and BC modified by iron or iron/ferrous sulphide (nZVI-BC and Fe/FeS-BC). Soil samples from an abandoned Sb mining site were tested under laboratory conditions. Two distinct (organic and mineral) soil layers were incubated with each of the amendments (2% w/w application rate) at 50% and 100% water holding capacity (WHC) of the soils for 10 weeks, and subsequently extracted with demineralised water and rainwater. The immobilisation efficiency of the tested amendments was significantly influenced by the different soil moisture regimes and type of contaminant. Sorption onto secondary Fe minerals was the dominant Sb/As immobilizing mechanism. The iron-based amendments showed up to 97% efficiency for Sb and up to 96% for As. However, Sb/As release was generally higher at 100% WHC and in the rainwater extracts compared to the other conditions, indicating that heavy rainfall and flooding of soils in-situ may increase contaminant availability and mobility. In the organic layer, enhanced formation and leaching of metalloid-DOC complexes and sorption competition of the negatively charged Sb/As species and DOC can be expected. Also, reductive dissolution of Sb or As-bearing metal oxides could lead to the observed higher Sb/As release under flooded conditions, resulting in exacerbated environmental and health risks. Therefore, it is crucial to (1) improve the sorption characteristics of the tested amendments and/or develop other effective amendments for Sb/As immobilisation in different water regimes in soil; (2) test the amendments under real field conditions to evaluate the long term wet/dry exposure; and (3) develop proper risk assessment and soil remediation strategy for the study area and similar sites. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we investigated the oxidative mechanisms of nano zero-valent iron (nZVI) enhanced potassium ferrate (K2FeO4), focusing on tributyltin (TBT) and triphenyltin (TPhT) as target pollutants. The addition of nZVI enhanced the degradation of both organic tin compounds by K2FeO4, exhibiting pseudo-first-order kinetics influenced by pH, carbonate, and fulvic acid. nZVI, as a reducing agent, facilitated the generation of stronger oxidizing species Fe (V) and Fe (IV) from K2FeO4 through electron transfer. The presence of hydroxyl radicals (OH) was confirmed by tert-butyl alcohol (TBA) verification. Intermediate products of TBT degradation by nZVI-enhanced K2FeO4 were identified using GC-MS, confirming de-alkylation leading to stepwise oxidation to inorganic tin ions. Due to excessively long Sn-C bonds in diphenyltin, rendering them unstable, Density Functional Theory (DFT) calculations were employed. Results indicated that Fe (IV) and Fe (V) predominantly attacked the Sn-C bonds of TPhT, while OH primarily targeted the benzene ring. HOMO energy levels suggested that Fe (V) was more prone to oxidizing TPhT than Fe (IV). Gibbs free energy calculations demonstrated that, in the presence of Fe (IV) and Fe (V), the energy barrier for breaking bonds and oxidizing into inorganic tin ions decreased, favoring the process over the self-decomposition of TPhT. Additionally, the lower energy barrier for OH indicated an easier degradation of TPhT. This study reveals that nZVI-enhanced K2FeO4 effectively removes TBT and TPhT, contributing to the understanding of the ferrate-mediated degradation mechanism of organic tin compounds. The findings offer insights and theoretical guidance for remediating organic tin pollution in aquatic environments.

Tetracycline (TC) contamination in water is one of the key issues in global environmental protection, and traditional water treatment methods are difficult to remove antibiotic pollutants.Therefore, efficient and environmentally friendly treatment technologies are urgently needed. In this study, activated persulfate (PS) using a biochar-loaded nano zero-valent iron (BC-nZVI) advanced oxidation system was used to investigate the degradation effect, influencing factors, and mechanism of TC. BC-nZVI was prepared using the liquid-phase reduction method, and its structure and properties were analyzed by various characterization means. The results showed that nZVI was uniformly distributed on the surface or in the pores of BC, forming a stable complex. Degradation experiments showed that the BC-nZVI/PS system could degrade TC up to 99.57% under optimal conditions. The experiments under different conditions revealed that the iron-carbon ratio, dosing amount, PS concentration, and pH value all affected the degradation efficiency. Free radical burst and electron paramagnetic resonance (EPR) experiments confirmed the dominant roles of hydroxyl and sulfate radicals in the degradation process, and LC–MS experiments revealed the multi-step reaction process of TC degradation. This study provides a scientific basis for the efficient treatment of TC pollution in water.

In this study, nPd/Fes were dispersed on peanut shells‐derived alkali‐modified biochar (BCalk) to obtain BCalk‐nPd/Fe composite for overcoming the instability, agglomeration, and oxidation of nPd/Fes. Results demonstrated that the dispersion stability and thermal stability of nPd/Fes were improved and the surface passivation layer was thinned by nanoparticles loading onto the alkalized biochar. Characterization analyses revealed of the improved 2,4‐D dichlorination by BCalk‐nPd/Fe. After biochar alkalization, more Si‐O‐Si sites on BCalk responsible for supporting nZVI particles were formed and coupled with nZVI to generate Si‐O‐Fe. Hence, nPd/Fes were immobilized on BCalk, while the increased oxygen‐containing surface functional groups promoted electron transport between nPd/Fes and 2,4‐D. Therefore, the BCalk‐nPd/Fe exhibited higher dechlorination efficiency toward 2,4‐D than that of nPd/Fe and BCraw‐nPd/Fe. About 99.25% and 89.11% of the 2,4‐D removal and dechlorination, respectively, were achieved after 150 min. Kinetic studies revealed that the removal of 2,4‐D using nPd/Fe, BCraw‐nPd/Fe, and BCalk‐nPd/Fe fitted well in the Langmuir–Hinshelwood kinetic model, and the order of rate constants was as follows: BCalk‐nPd/Fe > BCraw‐nPd/Fe > nPd/Fe. This study suggested that the prepared composites promoted detoxification and harmlessness of 2,4‐D contaminated wastewater and exhibited promising prospect in the efficient treatment of wastewater containing chlorinated organics. [ABSTRACT FROM AUTHOR]

Biochars loaded by nano zero-valent iron were environmentally friendly prepared using leaves of sycamore tree as raw materials and green tea filtrate as the reductant. The adsorption and removal of Cr (VI) on the prepared biochar samples was investigated in details for remediation of hexavalent chromium pollution in industrial wastewater. Modern instrumental analysis technologies were used to characterize the physical and chemical properties of the materials, such as micro morphology, functional groups, element composition and so on. Different Fe/C loading ratio, material dosage and initial Cr(VI) concentration were analyzed and compared to screen out the best preparation and adsorption conditions for the removal of Cr(VI). The results show that nano zero-valent iron particles are uniformly attached to the smooth and stretched surface of biochars, and the materials contain a variety of organic matters including phenols, olefins, aromatic compounds and alcohols. After loading nano zero-valent iron, the graphite structure of biochars remain the same, and the characteristic peaks of zero-valent iron can be found in XRD spectrum. The optimum preparation conditions are the pyrolysis temperature of 600 °C and the Fe/C loading ratio of 1: 24. Biochar loaded with nano zero-valent iron material (2.0 g) is added to 50 mL of Cr(VI) solution (10 mg/L), the maximum removal rate of Cr(VI) is 58.72% after the adsorption for 60 minutes. [ABSTRACT FROM AUTHOR]

Advanced oxidation process (AORs) is an effective method to remove a wide range of organic contaminants. However, an outstanding catalysis is needed to generate more free radicals. In this work, nano zero-valent iron (nZVI) modified with activated carbon and copper (AC-nZVI/Cu) was synthesized by liquid-phase reduction, and used to catalyze persulfate (PS) to remove norfloxacin (NOR). The effect of various factors, such as diverse adsorbents, pH, temperature, PS dosage, adsorbent dosage, and inorganic anions, on NOR removal efficiency were investigated. The results show that 30 mg/L NOR can be easily removed by 0.5 g/L AC-nZVI/Cu at 313 K through activating 0.5 mM PS, and the removal efficiency is as high as 96.84%. The electron paramagnetic resonance (EPR) analysis proves that numerous sulfate free radicals (·SO4 -) appear at the initial stage of the removal process. Furthermore, the quenching experiments manifested that ·SO4 - was the predominant radical special in acidic conditions, while adsorption of NOR was predominant under alkaline conditions. Importantly, compared with nZVI, AC-nZVI/Cu has excellent long-term stability because of the introduction of activated carbon and copper. The study laid the groundwork for further development of adsorbent and activator based on nZVI. [ABSTRACT FROM AUTHOR]

Applying nanotechnology, particularly nano zero-valent iron encapsulated by carboxymethyl cellulose (CMC-nZVI), is considered less expensive and provides high efficiency for the decolorization of textile wastewater. In this study, Congo red dye (CR) was used in synthesized wastewater to evaluate the treatment performance using different composition ratios of CMC-nZVI. At the initial CR concentration of 500 mg/L, decolorization efficiencies increased with the increase of CMC contents. The removal efficiencies reached almost completely at the CMC:Fe2+ ratio of 0.004 within 10 seconds after adding CMC-nZVI to the CR solution. The optimal decolorization rate was observed at the Fe concentration of 1 g/L, with the CR removal efficiency of approximately 90% and a removal capacity of 8.298 g CR/g nZVI. The core principle of dye decolorization is breaking down the chromophore groups (-NN-), which makes the color of the dye, into N–H bonds. CMC-nZVI is a promising key to solving the issues caused by dye-containing wastewater.

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H2O2, and pH on formaldehyde degradation were studied. The n-ZVI/TiO2 catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41 nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n‑ZVI/TiO2, and the Fe 2p spectrum of 2%n-ZVI/TiO2 indicated the presence of Fe0. The optimal conditions for the complete removal of formaldehyde within 30 min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5 g/L, 30 mM H2O2, and an initial pH of 3. After the reaction, the C–H functional group of formaldehyde was not observed due to the •OH radicals generated by Fe0 and H2O2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde. [ABSTRACT FROM AUTHOR]

A novel composite (nZVI/HNTs) was prepared via incorporating nano zero-valent iron (nZVI) on halloysite nanotubes (HNTs) for degrading tetracycline hydrochloride (TCH) with existence of persulfate (PS). The adsorption process of nZVI/HNTs to TCH conformed to the Freundlich isotherm model and pseudo-second-order kinetic model, and its maximum adsorption capacity was 76.62 mg·g−1. Furthermore, the nZVI/HNTs + PS system exhibited satisfactory degradation efficiency (84.21%) for TCH, and stable nZVI/HNTs (Fe leaching < 0.001 mg·L−1) could be reused. When nZVI/HNTs dosage, PS dosage and temperature increased, TCH degradation could be enhanced. After four cycling, nZVI/HNTs + PS system had still 65.8% degradation for TCH. The quenching tests and EPR analysis evidenced that SO4•− was predominant instead of •OH in such system. Three possible pathways of TCH degradation were provided through the liquid chromatograph-mass spectrometer (LC–MS) determination. Meanwhile, the biological toxicity prediction analysis indicated that the nZVI/HNTs + PS system would be an environment friendly treatment method toward TCH pollution. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, a novel peroxydisulfate (PDS) activator (CF-nZVI-JE) was prepared via in-situ loading nano zero-valent iron (nZVI) on Juncus effusus (JE) followed with wrapping a layer of cellulose film (CF). The CF-nZVI-JE had the same 3D structure as the JE, being easy to separate from aqueous solution. The loaded nZVI existed single nanoparticles with a size of 60–100 nm except chain-type agglomeration of nanoparticles due to the stabilization of JE fibers. The activation performance of the CF-nZVI-JE for PDS was evaluated with Rhodamine B (Rh B) as a representative pollutant. Under the optimal activating conditions, the degradation rate of Rh B reached 99% within 30 min in the CF-nZVI-JE/PDS system. After five cycles, the degradation rate of Rh B was still over 85%, suggesting that the CF-nZVI-JE had good reusability. More interestingly, SO4·− and ·OH radicals were simultaneously detected in the CF-nZVI-JE/PDS system, but only SO4·− existed in the JE-ZVI/PDS system, suggesting the different activation mechanism. Meanwhile, the introduction of CF not only facilitated to the mineralization of Rh B but also significantly reduced the release amount of iron ions. Hence, the CF-nZVI-JE can be employed as a promising PDS activator for the treatment of organic wastewater. HIGHLIGHTS The prepared CF-nZVI-JE had the same 3D structure as JE, which can stabilize nZVI.; nZVI existed as single nanoparticles and chain-type agglomeration of nanoparticles.; Rh B degradation was involved in SO4−· and HO· in the CF-nZVI-JE/PDS system.; CF-nZVI-JE facilitated the mineralization of Rh B compared with the nZVI-JE.; CF prevented the leakage of nZVI and reduced the release amount of iron ions.;

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.

In this study, nano zero-valent iron (nZVI) was used as the Fe2+ source in the Fenton reaction, and a UV-nZVI-H2O2 system was constructed to efficiently degrade and mineralize refractory organic matter in landfill leachate. The results showed that under the optimal conditions (initial pH = 3, UV = 14 W, nZVI = 0.5 g/L, and [H2O2] = 30 mM), the removal efficiencies of total organic carbon, absorbance at 254 nm, and color number were 61.38%, 83.89%, and 85.79%, respectively. Control experiments show that the UV-nZVI-H2O2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H2O2 system is related to a higher H2O2 utilization rate. The H2O2 residue in the UV-nZVI-H2O2 system was the lowest, and the effective utilization rate of H2O2 was as high as 98.80%. Alcohol quenching experiments and hydroxyl radical quantitative experiments showed that the dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO• and the yield of HO• was as high as 2007.80 μM, which was much higher than that in other systems. The results of spectra analysis showed that the low molecular weight, high fluorescence frequency organic matter, and relatively stable aromatic organic matter were significantly degraded after treatment with the UV-nZVI-H2O2 system and the aromatic degree, humification degree, molecular weight, and molecular polymerization degree of refractory organic matter were also significantly decreased. The mechanism of the UV-nZVI-H2O2 reaction includes homogeneous and heterogeneous Fenton reactions and adsorption and precipitation of organic matter by iron-based colloids. This study can provide theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate. [ABSTRACT FROM AUTHOR]

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Copyright of Hydrometallurgy of China is the property of Hydrometallurgy of China Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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.

Rainwater harvesting is a viable option for dealing with the global challenge of increasing water scarcity, but heavy metal contamination often prevents it from being widely used for drinking water purposes. Harvested rainwater collected from galvanized iron (GI) and tile roofs containing iron concentration of 0.46 and 0.38 mg/L respectively, were treated by two nano sorbents, CaCO3-nZVI and PUF/CaCO3-nZVI with the intention of making the iron concentration conform to drinking quality standards. The nano sorbents were synthesized and characterized using BET (Brunauer-–Emmett–Teller surface area), SEM-EDX (Scanning Electron Microscopy-Energy-Dispersive X-ray spectroscopy, and FTIR (Fourier Transform Infrared Spectroscopy). CaCO3-nZVI achieved iron removal efficacy of 88.69% and 89.21% for harvested rainwater from GI sheet roof and tiled roof respectively and the efficiency increased to 95.65% and 95.78% when treated with PUF/CaCO3-nZVI. In addition, the nano sorbents were found to have appreciable removal efficiency for other metals (Pb, Mn, Zn, Cu, Cd and Cr) present in the collected rainwater. The use of FTIR and EDX to characterise spent nano sorbents divulged that the iron was removed through sorption process. This study thus explored the potential of CaCO3-nZVI and PUF/CaCO3-nZVI for treating heavy metal contamination in roof-harvested rainwater. HIGHLIGHTS Developed a novel nanocomposite by impregnation and surface modification of nZVI.; PUF/CaCO3-nZVI reduced the iron concentration to acceptable limit for the potable water.; PUF/CaCO3-nZVI was able to simultaneously remove other heavy metals.; Novel nano composite reduced the turbidity of the samples to permissible limit.; PUF/CaCO3-nZVI outperformed conventional sorbents in iron removal.;

Sulfidated nano zero-valent iron supported by activated carbon (S-nZVI/AC) composites were synthesized via liquid phase reduction method, and then they were used for Cr(VI) elimination. Characterization results showed that Fe0 was the main component, besides, iron oxides and iron sulfides were also detected. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that S-nZVI nanoparticles were homogeneously distributed on the surfaces of AC. The influences of S/Fe ratio, C/Fe ratio, pH value, reaction temperature and co-existed ions (Cl−, SO42−, PO43− and NO3−) on Cr(VI) removal performances were investigated. Furthermore, the corresponding mechanisms were also discussed. The S-nZVI/AC composites exhibited good aging-resistance performances that Cr(VI) removal efficiency still maintained at 83.1% after being sealed in water for seven days, and they also had satisfying cycling stabilities that Cr(VI) removal efficiency only decreased less than 10% after four cycles. The good performances of S-nZVI/AC composites for Cr(VI) removal are attributed to the protection effect of iron sulfides and immobilization effect of AC, making S-nZVI/AC as a promising candidate for Cr(VI) elimination in effluents. HIGHLIGHTS S-nZVI/AC composites were synthesized and used for Cr(VI) elimination.; The influences of many experimental factors were investigated and discussed.; The S-nZVI/AC composites showed satisfying cycling stabilities.;

In the framework of wastewater treatment plants, sewage sludge can be directed to biochar production, which when coupled with an external iron source has the potential to be used as a carbon–iron composite material for treating various organic pollutants in advanced oxidation processes. In this research, "green" synthesized nano zero-valent iron (nZVI) supported on sewage sludge-based biochar (BC)–nZVI-BC was used in the Fenton process for the degradation of the recalcitrant organic molecule. In this way, the circular economy principles were supported within wastewater treatment with immediate loop closing; unlike previous papers, where only the water treatment was assessed, the authors proposed a new approach to wastewater treatment, combining solutions for both water and sludge. The following phases were implemented: synthesis and characterization of nano zero-valent iron supported on sewage sludge-based biochar (nZVI-BC); optimization of organic pollutant removal (Reactive Blue 4 as the model pollutant) by nZVI-BC in the Fenton process, using a Definitive Screening Design (DSD) model; reuse of the obtained Fenton sludge, as an additional catalytic material, under previously optimized conditions; and assessment of the exhausted Fenton sludge's ability to be used as a source of nutrients. nZVI-BC was used in the Fenton treatment for the degradation of Reactive Blue 4—a model substance containing a complex and stable anthraquinone structure. The DSD model proposes a high dye-removal efficiency of 95.02% under the following optimal conditions: [RB4] = 50 mg/L, [nZVI] = 200 mg/L, [H2O2] = 10 mM. pH correction was not performed (pH = 3.2). Afterwards, the remaining Fenton sludge, which was thermally treated (named FStreated), was applied as a heterogeneous catalyst under the same optimal conditions with a near-complete organic molecule degradation (99.56% ± 0.15). It could be clearly noticed that the cumulative amount of released nutrients significantly increased with the number of leaching experiments. The highest cumulative amounts of released K, Ca, Mg, Na, and P were therefore observed at the fifth leaching cycle (6.40, 1.66, 1.12, 0.62, 0.48 and 58.2 mg/g, respectively). According to the nutrient release and toxic metal content, FStreated proved to be viable for agricultural applications; these findings illustrated that the "green" synthesis of nZVI-BC not only provides innovative and efficient Fenton catalysts, but also constitutes a novel approach for the utilization of sewage sludge, supporting overall process sustainability. [ABSTRACT FROM AUTHOR]

Aiming at the potential hazard of the wastewater with the coexistence of selenium and antibiotics in selenium-enriched aquaculture, nano zero-valent iron (nZVI) was in situ synthesized on the N-doped porous biochar (NBC) prepared by shrimp shells, resulting in the composites (NBC-nZVI) with active functional components of NBC and nZVI. The samples were characterized by scanning electron microscopy (SEM), nitrogen adsorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Taking Se (IV) and ciprofloxacin (CIP) as the targeted pollutants, the simultaneous adsorption behavior of NBC-nZVI was investigated. The results showed that the removal performance of NBC-nZVI toward CIP and Se( IV) was superior to that of NBC and nZVI. Se (IV) was preferentially adsorbed on the surface of NBC-nZVI compared to CIP, which mediated the adsorption of CIP and improved the removal performance of NBC-nZVI to CIP. The adsorption of NBC-nZVI for Se(IV) was nearly immune to CIP. The adsorption behavior of NBC-nZVI toward CIP and Se( IV) in the bicomponent system followed the pseudo-second-order kinetics and Sips isotherm model, and the theo-retical maximum adsorption capacities for CIP and Se(IV) were 130.6,335.7 mg/g, respectively. [ABSTRACT FROM AUTHOR]

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.;

The co-contamination of soils with heavy metals and organic contaminants is a problem that requires a different and innovative approach to remediate these kinds of sites. The different nature of these two contaminant groups makes the problem complicated. Recently, zero-valent iron nanoparticles (nZVI) application has been integrated with bioremediation to be used for the remediation of halogenated organics. However, the use of this process for the remediation of co-contaminated soils has not been investigated. In this study, nZVI application integrated with bioremediation approaches (bioattenuation and biostimulation) was applied to Pb and naphthalene spiked soils in laboratory-scale reactors. Soil Pb fractions and naphthalene concentrations were monitored for 90 days. The nZVI decreased the mobility and bioavailability of Pb significantly by reducing exchangeable and carbonate bound fractions from 66.2 % to 25.8 – 37.2 % range. The nZVI also caused naphthalene degradation in the range of 38.8 – 58.5 %. Significant biodegradation of naphthalene occurred at samples subjected to nZVI and biostimulation. The highest overall naphthalene degradation (76.7 %) was obtained from the nZVI application which was integrated with biostimulation.

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]

Hexavalent chromium [Cr(VI)] is a highly toxic agent that seriously threatens the environment and human health. In-situ reduction and immobilization are potential strategies to treat Cr(VI)-contaminated soil. In this study, sodium alginate (SA) and carboxymethylcellulose (CMC) were used to modify nano-zero-valent iron (NZVI) to prepare SA-NZVI and CMC-NZVI to study its effect on the reduction efficiency of Cr(VI) in the soil. Scanning electron microscope (SEM) images found that compared with the agglomeration of NZVI and CMC-NZVI, SA-NZVI particles have a significant improvement, better dispersion, chain-like distribution, and a particle size of 50–100 nm. And the X-ray diffraction (XRD) pattern further showed that SA-NZVI has only Fe0 peaks and no Fe3O4 peaks, which further proved that it is pure nano-zero-valent iron. The batch tests showed that SA-NZVI could quickly and effectively reduce the Cr(VI) in the soil, and SA-NZVI could reduce the Cr(VI) by 96.68%. For Cr(VI)-contaminated soil, the Cr(VI) reduction rate of SA-NZVI was higher than NZVI and CMC-NZVI. After 28 d remediation, the fractions of Cr forms in soil, such as exchangeable (EX), carbonate-bound (CB), Fe-Mn oxides-bound (OX), and organic matter-bound (OM), were mainly transformed to residual fraction (RS) species because of the production of ferrochrome precipitates. X-ray photoelectron spectroscopy (XPS) showed that after SA-NZVI treatment, Cr(VI) was reduced to trivalent chromium [Cr(III)] and the formation of Cr(OH)3 precipitation. The research results provide a theoretical basis for applying SA-NZVI in Cr(VI) contaminated soil remediation. [ABSTRACT FROM AUTHOR]

The new composite material was synthesised bonding nano zero-valent iron (NZVI) with liquid-phase chemical reduction method on the support material obtained by carbonising the organic waste mandarin peel, and the surface characteristics of it were determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and zero point of charge (pHzpc). The effectiveness of the composite as an adsorbent in the removal of malachite green (MG) was investigated with different parameters. Equilibrium data were employed to different adsorption isotherms used in aqueous solutions, and the most suitable isotherm was found as Freundlich isotherm with the highest R2 =0.999 and the lowest chi-square (χ2) and residual root-mean-square error (RMSE) values. The maximum adsorption capacity was 909.09 mg/g according to Langmuir isotherm. When the kinetic data were analysed, the most appropriate kinetic model was determined as pseudo-second-order with the lowest χ2 and RMSE and the highest R2 (≥0.987) values. The adsorption process was carried out as endothermic (∆H°=145.79 kJ/mol) and spontaneously (∆G°≤−2.89kJ/mol) according to thermodynamic parameters. Also, it was possible to say that the irregularity at the adsorbent-adsorbate interface increased due to positive entropy. NZVI/carbonised mandarin peel (CMP) with high adsorption capacity could be used effectively to remove many industrial wastes. [ABSTRACT FROM AUTHOR]

Due to the bioavailability and movement of antimony in trophic web, the overexploitation of antimony mine resulted in antimony contamination that harmed the ecology nearby, raising concerns for public health. Whereas, most researches focused on the removal of antimony in the aqueous instead of the immobilization of antimony in the soil. Herein, the immobilized performance of biochar (BC) loaded with nano zero-valent iron (nZVI-BC) on antimony in the soil near the smelting area was researched through pot experiments for the first time, and its stabilization mechanism on antimony was investigated by valent state variation of antimony. The results demonstrated that BC restricted the cation exchange capacity and catalase activity in the soil, while nZVI-BC had a favorable and negative impact on two variables, respectively. The nZVI-BC showed more stable immobilization capacity on antimony over time than BC, whose exchangeable speciation only marginally rose (2%–6%), although the exchangeable speciation of antimony fell both from 15% to 2% after adding the BC and nZVI-BC, The electron attraction force between nZVI-BC and antimony was also intensified owing to the oxidation-reduction process, which was considered as the stabilizing principle of nZVI-BC on antimony in soil. Furthermore, the decreased bioaccumulation factor for the perennial ryegrass (0.46–0.21) and Galinsoga parviflora Cav. (0.26–0.17) stated that the BC effectively mitigated the bioaccumulation risk of antimony. [Display omitted] • NZVI-BC was applied to remediate Sb-contaminated soil in Sb mine area. • NZVI-BC presented more excellent and stable stabilized effect on Sb to BC. • The redox reaction and adsorption of nZVI-BC on Sb were stabilized principle. • The BC promotes plant growth, whereas so doesn't nZVI-BC. • BC and nZVI-BC reduced the bioavailability of Sb. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) has been shown to facilitate biofuel production, notably in hydrogen generation. However, its effect on bioethanol production is rarely studied, and even less so on its impact on hydrogen and ethanol co-production. This study therefore conducted ethanol-type hydrogen-producing fermentation with brown algae to explore the effect of nZVI. With the supplementation of nZVI, fermentation was accelerated and the production of hydrogen and ethanol were both significantly enhanced. At the optimal nZVI concentration of 100 mg/L, the production of hydrogen and ethanol increased by 71.44% and 65.11%, respectively. A high hydrogen yield of 2.32 mol/mol-mannitol was achieved. The ethanol yield (1.86 mol/mol-mannitol) reached 93% of the theoretical maximal yield with a high selectivity of 91.09%. Electron distribution analysis showed that nZVI increased the total electron amounts of fermentation, and directed more electrons to ethanol than hydrogen. The reduced redox potential (ORP) and increased NADH level further confirmed the role of nZVI. Moreover, nZVI fostered Fe2+ availability to hydrogen-producing bacteria, enhancing the enzymes hydrogenase and alcohol dehydrogenase, as well as cell biomass. The bioenergy conversion efficiency (BioECE) improved from 19.08% to 31.74% with 100 mg/L nZVI treatment. This study provided a first demonstration regarding the role of nZVI in hydrogen and ethanol co-production, highlighting the great potential of multiple bioenergy recovery from marine biomass. [Display omitted] • nZVI of 100 mg/L increased H 2 production by 71.44% and ethanol by 65.11%. • Maximal H 2 and ethanol yields reached 2.32 and 1.86 mol/mol, respectively. • nZVI promoted H 2 -ethanol co-production via electron donating and iron supply. • nZVI donated more electrons to ethanol than hydrogen synthesis pathway. • An efficient gas-liquid biofuel coproduction from marine biomass was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • An iron-rich encrustation layer (IEL) on anammox granular surface has been created. • IEL forms by the aggregation of gel networks and binding of iron species with EPS. • IEL leads to superior settling ability, heme content, and metabolic gene abundance. • IEL AnGS shows excellent nitrogen removal performance under high load stress. • IEL reduces shear force, enhancing the AnGS's resistance to high load stress. Anaerobic ammonia oxidation (anammox) is a cost-effective technology but its performance can be seriously inhibited by high load stress. This study has created an innovative iron-rich encrustation layer (IEL) on the surface of anammox granules (AnGS) through the addition of a certain amount of nano zero-valent iron. The IEL was formed through the aggregation of a gel network and the binding of iron species with extracellular polymeric substances (EPS), resulting in a significant increase in settling ability, EPS secretion, and heme content. Metagenomic analysis indicated a notable rise in the functional genes associated with nitrogen andiron metabolism in IEL AnGS. Under high load stress, the ammonia removal performance of AnGS without IEL severely declined. In contrast, IEL AnGS exhibited excellent ammonia removal efficiency of over 90%. The IEL served as a protective barrier for AnGS, effectively mitigating the strong shear forces, thereby enhancing their resistance to high load stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • nZVI was used in sediment microbial fuel cell (SMFC) to improve Cu2+ removal. • Cu precipitation was found on the surface of nZVI-based O 2 -releasing bead (ORB). • nZVI-based ORBs were added to the SMFC cathode to improve power generation. • The obvious change of Fe-O group improves participation of nZVI in the reaction. Membrane-less single-medium sediment microbial fuel cells (single-SMFC) can remove Cu2+ from sediment through electromigration. However, the high mass transfer resistance of the sediment and amount of oxygen at the cathode of the SMFC limit its Cu2+ removal ability. Therefore, this study used an oxygen-releasing bead (ORB) for slow oxygen release to increase oxygen at the SMFC cathode and improve the mass transfer property of the sediment. Resultantly, the copper removal efficiency of SMFC increased significantly. Response surface methodology was used to optimize the nano zero-valent iron (nZVI)-modified biochar as the catalyst to enhance the ability of the modified ORB (ORB m) to remove Cu2+ and slow release of O 2. The maximum Cu2+ removal (95 %) and the slowest O 2 release rate (0.41 mg O 2 /d·g ORB m) were obtained when the CaO 2 content and ratio of nZVI-modified biochar to unmodified biochar were 0.99 g and 4.95, respectively. When the optimized ORB m was placed at the single-SMFC cathode, the voltage output and copper removal increased by 4.6 and 2.1 times, respectively, compared with the system without ORB m. This shows that the ORB m can improve the migration of Cu2+ in the sediment, providing a promising remediation method for Cu-contaminated sediments. [ABSTRACT FROM AUTHOR]

For efficient and environmentally friendly removal of nitrate from groundwater, biochar-based nanoscale zerovalent iron composites were prepared, where biochar was derived from pine sawdust at 4 different pyrolysis temperatures. The results show that biochar with different pyrolysis temperatures played a great role in both nitrate removal efficiency and nitrate conversion rate to nitrogen gas for the prepared composites. Specifically, the composite with biochar pyrolyzed at 500 °C, ZB12-500, showed the best performance in both nitrate removal and conversion to nitrogen gas. With an initial solution pH from 5 to 10, ZB12-500 maintained high removal efficiencies varying from 97.29% to 89.04%. Moreover, the conversion of nitrate to nitrogen gas increased with the initial nitrate concentration, and it reached 31.66% with an initial nitrate concentration of 100 mg/L. Kinetics analysis showed that the nitrate removal process fit well with a two-compartment first-order kinetic model. Meanwhile, the test of nitrate removal by ZB12-500 in synthetic groundwater showed that HCO3− and SO42− limited nitrate removal but improved nitrate conversion to nitrogen gas. Furthermore, the nitrate removal mechanism suggested that biochar could facilitate electron transfer from zero valent iron to nitrate, which led to high nitrate removal efficiency. In addition, the interaction of ferrous ions and the quinone group of biochar could increase the nitrate conversion to nitrogen gas. Therefore, this study suggests that ZB12-500 is a promising alternative for the remediation of nitrate-contaminated groundwater. [ABSTRACT FROM AUTHOR]