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The pursuit of clean energy generation and environmental preservation is of utmost importance for societal progress. However, couple clean energy production and pollution control is still a difficulty. In this study, a novel electrospun composite mat, with nano zero valent iron (Fe 0 , nZVI) encapsulated into polyacrylonitrile (PAN) nanofibers was acted as a catalyst. The activation energy (E a ) for the hydrolysis of NaBH 4 to produce hydrogen is 22 kJ·mol -1 , hydrogen atom utilization efficiency (HGE) of NaBH 4 is 60.80%. Three kinds of organic dyes 4-nitrophenol (4-NP), methylene blue (MB), and Rhodamine B (RhB) were served as the model pollutant, to construct NaBH 4 -organic system for energy production and pollution reduction. The NaBH 4 -organic system demonstrates a collaborative capability to simultaneously remove organic pollutants and generate hydrogen, with a coupling equilibrium point between the two processes. The hydrogen generation rate (HGR) and HGE increased with the concentration of pollutants increased. The degradation of 4-NP, MB, and RhB followed pseudo-first-order kinetics, with RhB degrading dosage 20 and 44 times higher than 4-NP and MB, respectively. H 2 and H· contributed to the organic degradation. nZVI directly participated in the formation H 2 and H·. PAN@Fe 0 possessed good recyclability and moderate cost. The degradation process adhered to the classical surface reaction controlled Langmuir-Hinshelwood (L-H) model. The integration of synergistic production capacity and pollutant degradation aligns well with the principles of green chemistry and sustainable development. This study demonstrates a novel approach to no precursor loss catalysts preparation, efficient production clean H 2 , advanced treatment of dye-containing wastewater, carbon neutral operation of sewage treatment plant., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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.

Membrane-less single-medium sediment microbial fuel cells (single-SMFC) can remove Cu 2+ 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 Cu 2+ 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 Cu 2+ and slow release of O 2 . The maximum Cu 2+ 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 Cu 2+ in the sediment, providing a promising remediation method for Cu-contaminated sediments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This work combined the stability of the porous structure of metal-organic frameworks with the strong reducibility of nano zero-valent iron, for the controllable integration of NZVI into MOFs to utilize the advantages of each component with enhancing the rapid decontamination and scavenging of Cr(VI) from wastewater. Hence, four kinds of MOFs/NZVI composites namely ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, were prepared for Cr(VI) capture. The results indicated that the stable structure of ZIF67, MOF74, MIL101(Fe), CuBTC, was beneficial for the dispersion of NZVI that could help more close contact between MOFs/NZVI reactive sites and Cr(VI), subsequently, MOFs/NZVI was proved to be better scavengers for Cr(VI) scavenging than NZVI alone. The Cr(VI) capture achieved the maximum adsorption capacity at pH ~ 4.0, which might be due to the participation of more H + in the reaction and better corrosion of NZVI at lower pH. Mechanism investigation demonstrated synergy of adsorption, reduction and surface precipitation resulted in enhanced Cr(VI) scavenging, and Fe(0), dissolved and surface-bound Fe(II) were the primary reducing species. The findings of this investigation indicated that the as-prepared composites of ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, with high oxidation resistance and excellent reactivity, could provide reference for the decontamination and purification of actual Cr(VI)-containing wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study assessed the effectiveness of nano zero-valent iron loaded on biochar (BC-nZVI) during swine manure composting. BC-nZVI significantly reduced the abundance of antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and mobile genetic elements (MGEs). BC-nZVI modified the preference of MGEs to carry ARGs and MRGs, and the corrosion products of BC-nZVI could destroy cell structure, hinder electron transfer between cells, and weaken the association between ARGs, MRGs, and host bacteria. Functional genes analysis revealed that BC-nZVI down-regulated the abundance of genes affecting the transmission and metabolism of ARGs and MRGs, including type IV secretion systems, transporter systems, two-component systems, and multidrug efflux pumps. Furthermore, the BC-nZVI decreased genes related to flagella and pili production and cell membrane permeability, thereby hindering the transfer of ARGs, MRGs, and MGEs in the environment. Redundancy analysis demonstrated that changes in the microbial community induced by BC-nZVI were pivotal factors impacting the abundance of ARGs, MRGs, and MGEs. Overall, this study confirmed the efficacy of BC-nZVI in reducing resistance genes during swine manure composting, offering a promising environmental strategy to mitigate the dissemination of these contaminants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Decabromodiphenyl ether (BDE-209) is a common brominated flame retardant in electronic waste, and nano zero-valent iron (nZVI) is a new material in the field of environmental remediation. Little is known about how BDE-209 and nZVI combined exposure influences soil organisms. During the 28 days study, we determined the effects of single and combined exposures to BDE-209 and nZVI on the oxidative stress and metabolic response of earthworms (Eisenia fetida). On day 7, compared to CK, malondialdehyde (MDA) content increased in most combined exposure groups. To remove MDA and reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were induced in most combined exposure groups. On day 28, compared to CK, the activities of SOD and CAT were inhibited, while POD activity was significantly induced, indicating that POD plays an important role in scavenging ROS. Combined exposure to BDE-209 and nZVI significantly affected amino acid biosynthesis and metabolism, purine metabolism, and aminoacyl-tRNA biosynthesis pathways, interfered with energy metabolism, and aggravated oxidative stress in earthworms. These findings provide a basis for assessing the ecological impacts of using nZVI to remediate soils contaminated with BDE-209 from electronic waste., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Cu (II) is a toxic heavy metal commonly identified in groundwater contaminants. Bentonite-based cutoff wall is the most used method in isolating and adsorbing contaminants, while the bentonite in it easily to fail due to Cu(II) exchange. This study synthesized a novel material through the modification of calcium bentonite (CaB) utilizing sodium hexametaphosphate (SHMP) and nano zero-valent iron (NZVI). The characteristics, adsorption performance, and mechanism of the NZVI/SHMP-CaB were investigated comprehensively. The results showed that SHMP can disperse CaB and reduce flocculation, while NZVI can be further stabilized without agglomeration. The best adsorption performance of NZVI/SHMP-CaB could be obtained at the dosage of 2% SHMP and 4% NZVI. The NZVI/SHMP-CaB exhibited an outstanding removal efficiency of over 60% and 90% at a high Cu(II) concentration (pH = 6, Cu(II) = 300 mg/L) and acidic conditions (pH = 3-6, Cu(II) = 50 mg/L), respectively. The adsorption of Cu(II) by NZVI/SHMP-CaB followed a pseudo-second-order kinetic model, and fitting results from the Freundlich isothermal model suggested that the adsorption process occurred spontaneously. Besides the rapid surface adsorption on the NZVI/SHMP-CaB and ion exchange with interlayer ions in bentonite, the removal mechanism of Cu(II) also involved the chemical reduction to insoluble forms such as Cu 0 and Cu 2 O. The generated FePO 4 covered the surface of the homogenized NZVI particles, enhancing the resistance of NZVI/SHMP-CaB to acidic and oxidative environments. This study indicates that NZVI/SHMP-CaB is a promising alternative material which can be used for heavy metal removal from contaminated soil and water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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 m 2 /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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Nanoscale zero-valent iron (nZVI) is attracting increasing attention as the most commonly used environmental remediation material. However, given the high surface area and strong reducing capabilities of nZVI, there is a lack of understanding regarding its effects on the complex anaerobic methane production process in flooded soils. To elucidate the mechanism of CH 4 production in soil exposed to nZVI, paddy soil was collected and subjected to anaerobic culture under continuous flooding conditions, with various dosages of nZVI applied. The results showed that the introduction of nZVI into anaerobic flooded rice paddy systems promoted microbial utilization of acetate and carbon dioxide as carbon sources for methane production, ultimately leading to increased methane production. Following the introduction of nZVI into the soil, there was a rapid increase in hydrogen levels in the headspace, surpassing that of the control group. The hydrogen levels in both the experimental and control groups were depleted by the 29th day of culture. These findings suggest that nZVI exposure facilitates the enrichment of hydrogenotrophic methanogens, providing them with a favorable environment for growth. Additionally, it affected soil physicochemical properties by increasing pH and electrical conductivity. The metagenomic analysis further indicates that under exposure to nZVI, hydrogenotrophic methanogens, particularly Methanobacteriaceae and Methanocellaceae, were enriched. The relative abundance of genes such as mcrA and mcrB associated with methane production was increased. This study provides important theoretical insights into the response of key microbes, functional genes, and methane production pathways to nZVI during anaerobic methane production in rice paddy soils, offering fundamental insights into the long-term fate and risks associated with the introduction of nZVI into soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In this study, we synthesized nano zero-valent iron incorporated with a multifunctional molybdenum disulfide film (MoS 2 @nZVI). The material exhibited a 100.00 % removal efficiency for sulfamethoxazole (SMX) and achieved a k obs of 0.4485 min -1 within 10 min. The excellent degradation performance can be attributed to the incorporation of the MoS 2 film, which facilitated Fe 2+ regeneration. Simultaneously, the MoS 2 film assisted in proton accumulation and electron transfer, thereby amplifying the efficiency of SMX degradation across a wide pH range. Comprehensive experimental examinations and characterizations confirmed the selectivity and stability of the MoS 2 @nZVI catalysts, encompassing both degradation efficiency and structural stability. Interestingly, the MoS 2 @nZVI/PMS system for SMX degradation significantly involved a non-radical mechanism ( 1 O 2 ), along with radicals (SO 4 ·- , ·OH, and O 2 ·- ). The direct oxidation of PMS by Fe 2+ not only facilitated the generation of ·OH and SO 4 ·- but also actively engaged in a reaction with O 2 , leading to the production of O 2 ·- . The primary pathway for 1 O 2 production was established through the interplay between Mo 6+ and O 2 ·- , in conjunction with the direct electron transfer (DET) mechanism between PMS and SMX. The contributions of these active species to SMX degradation occurred in the following precedence: SO 4 ·-  >  1 O 2  > ·OH > O 2 ·- . Notably, the primary pathways for radicals and non-radicals were studied during separate reaction periods. This investigation proposed a promising approach for mitigating pharmaceutical pollutants using a transition metal sulfide-modified nZVI catalyst., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Antibiotics and antibiotic resistance genetic pollution have become a global environmental and health concern recently, with frequent detection in various environmental media. Therefore, finding ways to control antibiotics and antibiotic resistance genes (ARGs) is urgently needed. Nano zero-valent iron (nZVI) has shown a positive effect on antibiotics degradation and restraining ARGs, making it a promising solution for controlling antibiotics and ARGs. However, given the current increasingly fragmented research focus and results, a comprehensive review is still lacking. In this work, we first introduce the origin and transmission of antibiotics and ARGs in various environmental media, and then discuss the affecting factors during the degradation of antibiotics and the control of ARGs by nZVI and modified nZVI, including pH, nZVI dose, and oxidant concentration, etc. Then, the mechanisms of antibiotic and ARGs removal promoted by nZVI are also summarized. In general, the mechanism of antibiotic degradation by nZVI mainly includes adsorption and reduction, while promoting the biodegradation of antibiotics by affecting the microbial community. nZVI can also be combined with persulfates to degrade antibiotics through advanced oxidation processes. For the control of ARGs, nZVI not only changes the microbial community structure, but also affects the proliferation of ARGs through affecting the fate of mobile genetic elements (MGEs). Finally, some new ideas on the application of nZVI in the treatment of antibiotic resistance are proposed. This paper provides a reference for research and application in this field., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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., (© 2024. The Author(s).)

In this work, nano zero-valent iron (nZVI) was added to a lab-scale continuous stirring tank reactor (CSTR) for food waste slurry treatment, and the effect of dosing rate and dosage of nZVI were attempted to be changed. The results showed that anaerobic digestion (AD) efficiency and biomethanation stability were optimum under the daily dosing and dosage of 0.48 g/gTCOD. The average daily methane (CH 4 ) yield reached 495.38 mL/gTCOD, which was 43.65% higher than that at control stage, and the maximum CH 4 content reached 95%. However, under single dosing rate conditions, high nZVI concentrations caused microbial cell rupture and loosely bound extracellular polymeric substances (LB-EPS) precipitation degradation. The daily dosing rate promoted the hydrogenotrophic methanogenesis pathway, and the activity of coenzyme F 420 increased by 400.29%. The microbial analysis indicated that daily addition of nZVI could promote the growth of acid-producing bacteria (Firmicutes and Bacteroidetes) and methanogens (Methanothrix)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The presence of micropollutants in water bodies has become a growing concern due to their persistence, bioaccumulation and potential toxicological effects on aquatic life and humans. In this study, the performance of a column system consisting of zero-valent iron nanoparticles (nZVI) incorporated into a cationic resin and synthesized from green tea extract with the addition of persulfate for the elimination of selected pharmaceuticals and endocrine disruptors from wastewater is evaluated. Ibuprofen, naproxen, diclofenac and ketoprofen were the target pharmaceuticals from non-steroidal anti-inflammatory drugs group, while bisphenol A was the target endocrine disruptor. In this context, different real wastewater effluent matrices were investigated: anaerobic membrane bioreactor (AnMBR), upflow anaerobic sludge blanket reactor (UASB) after microfiltration, tertiary treated by conventional activated sludge system and saturated vertical constructed wetland followed by a sand filtration unit effluent (hybrid). The transformation products of diclofenac and bisphenol A were also identified. The experimental results indicated that the performance of the R-nFe/PS system towards the removal efficiency of the target compounds was enhanced in the order of effluents: tertiary > AnMBR ≈ hybrid > UASB. More than 70% removal was obtained for almost all target compounds when conventional tertiary effluent was used, while the maximum removal efficiency was about 50% in the case of filtered UASB. As far as we know, this is the first time that nZVI has been assessed in combination with persulfate for the removal of micropollutants in a continuous flow system receiving various types of real wastewater with different matrix characteristics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Endogenous partial denitrification (EPD) has drawn a lot of interest due to its abundant nitrite (NO 2 - -P) removal rate of EPD restricts its promotion and application. In this study, the potentiality of various nano zero-valent iron (nZVI) concentrations (0, 20, 40, and 80 mg/L) on NO 4 3- -P) removal rate of EPD restricts its promotion and application. In this study, the potentiality of various nano zero-valent iron (nZVI) concentrations (0, 20, 40, and 80 mg/L) on NO 2 - -N accumulation and PO 4 3- -P removal in EPD systems had been investigated. Results showed that nZVI improved NO 2 - -N accumulation and PO 4 3- -P removal, with the greatest nitrate-to-nitrite transformation ratio (NTR) and PO 4 3- -P removal rate of 97.74 % and 64.76 % respectively at the optimum nZVI level (80 mg/L). Microbial community analysis also proved that nZVI had a remarkable influence on the microbial community of EPD. Candidatus_Competibacter was contribute to NO 2 - -N accumulation which was enriched from 24.74 % to 40.02 %. The enrichment of Thauera, Rhodobacteraceae, Pseudomonas were contributed to PO 4 3- -P removal. The chemistry of nZVI not only compensated for the deficiency of biological PO 4 3- -P removal, but also enhanced NO 2 - -N enrichment. Therefore, nZVI had the huge potentiality to improve the operational performance of the EPD system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Nano zero-valent iron (NZVI) is commonly used in industrial wastewater treatment. However, its long-term impact mechanisms of metabolization in anaerobic systems are not well understood. This study investigated the effects of long-term and continuous addition of NZVI on methanogenic activity, microbial community, and transcription activity. The results demonstrated that low levels of NZVI (1000 mg/L) induced inhibition of methanogenesis after 80 days, while high levels of NZVI (5000 mg/L) immediately led to a sharp decrease of cumulative methane production and chemical oxygen demand removal, which arrived at a steady state (14.4 % of control and 17 %) after 30 days. NZVI adversely affected cell viability, adenosine triphosphate production, and fatty acid evolution of cell membranes played a crucial role in resisting chronic NZVI toxicity. Moreover, high NZVI levels hindered the transcription of key enzymes CoM and mcrA, while low NZVI levels maintained its high CoM and mcrA activity, but down-regulated the transcription of cdh and hdr. Besides, amino-utilizing bacteria was reduced under the high NZVI concentration, while low NZVI changed dominant genus with potential protein hydrolysis function from Candidatus Cloacamonas to Sedimentibacter. These results provide a guideline for proper NZVI utilization in wastewater treatment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Aerobic denitrification and its mechanism by P. stutzeri was investigated in the presence of nanoscale zero-valent iron (nZVI). The removal of nitrate and ammonia was accelerated and the nitrite nitrogen accumulation was reduced by nZVI. The particle size and dosage of nZVI were key factors for enhancing aerobic denitrification. nZVI reduced the negative effects of low carbon/nitrogen, heavy metals, surfactants and salts to aerobic denitrification. nZVI and its dissolved irons were adsorbed into the bacteria cells, enhancing the transfer of electrons from nicotinamide adenine dinucleotide (NADH) to nitrate reductase. Moreover, the activities of NADH-ubiquinone reductase involved in the respiratory system, and the denitrifying enzymes were increased. The expression of denitrifying enzyme genes napA and nirS, as well as the iron metabolism gene fur, were promoted in the presence of nZVI. This work provides a strategy for enhancing the biological denitrification of wastewater using the bio-stimulation of nanomaterials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Direct electron transfer and the involvement of atomic hydrogen (H ⁎ ) are considered the main mechanisms for reductive dechlorination promoted by nano zero-valent iron (nZVI) supported on highly conductive carbon. It is still unclear how precisely H ⁎ , the specific surface area, and the electrochemical characteristics contribute to biochar supported nano zero-valent iron (BC-nZVI) activity in chlorinated hydrocarbon contaminant removal. In this study, a range of BC-nZVIs were prepared by a liquid-phase reduction process, and the contributions of specific surface area and electrochemical performance to H ⁎ generation and electron transfer have been assessed. The mechanism of trichloroethylene (TCE) dechlorination by BC-nZVIs has been evaluated in terms of removal efficiency and the ultimate degradation products. The results have demonstrated that BC-nZVIs exhibit a higher specific surface area and TCE degradation efficiency compared with the bare nZVI. Ethane, ethylene, and acetylene were the principal TCE degradation products. The elimination of TCE was not significantly affected by differences in BC-nZVI specific surface area, but electron transfer and sustained generation of H ⁎ were dependent on the catalyst electrochemical characteristics. The electrochemical properties of biochar serve to lower the corrosion potential of nZVI, improving electronic transfer capability and reactivity and promoting direct electron transfer for the degradation of TCE. In addition, the enhanced electrochemical properties also facilitate the reaction of nZVI with water and can promote the sustained generation of H ⁎ . Generation of H ⁎ played a key role in reductive dechlorination over BC-nZVIs, which was related to the properties of the biochar support. This study focuses on the role of H ⁎ and electrochemical performance in TCE reductive dechlorination, and provides a theoretical foundation and experimental support for the practical application of BC-nZVIs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

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 CO 3 2- and HCO 3 - had a significant negative effect on the degradation of TC. Meanwhile, ·OH and ·O 2 - 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., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Effective in-situ technology to treat carcinogenic compounds in contaminated areas poses a major challenge. Our objective was to load nano-zero-valent iron (nZVI) onto leonardite char (LNDC), an alternative carbon source from industrial waste, for use as a persulfate (PS) activator for styrene treatment in soil and water. By adding a surfactant during synthesis, cetyltrimethylammonium bromide (CTAB) promotes a flower-like morphology and the nZVI formation in smaller sizes. Results showed that nZVI plays a crucial role in PS activation in both homogeneous and heterogeneous reactions to generate reactive oxygen species (ROS), which can remove 98% of styrene within 20 min. Quenching experiments indicated that singlet oxygen ( 1 O 2 ), superoxide radicals (O 2 •- ), and sulfate radicals (SO 4 •- ) were the main species working together to degrade styrene. XPS analysis also revealed a role of surface oxygen-containing groups (i.e., CO, C-OH) in activating PS for SO 4 •- and 1 O 2 generation. The possible reaction mechanism of PS activation by LNDC-CTAB-nZVI composite and factors affecting treatment efficiency (i.e., PS concentration, catalyst dosage, pH, and humic acid) were illustrated. The molarity/molality ratio of PS to nZVI should be set greater than 1 for effective styrene removal. GC-MS analysis showed that styrene was degraded to a less toxic benzaldehyde intermediate. However, the excessive use of PS and catalysts can harm plant growth, requiring a combining approach to achieve safer use for real applications. Overall results supported the use of the LNDC-CTAB-nZVI/PS system as an efficient in-situ treatment technology for soil and water remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In this study, nano zero-valent iron loaded on biochar (BC-nZVI) was analyzed for its effects on antibiotic resistance genes (ARGs) in composting. The results showed that BC-nZVI increased reactive oxygen species (ROS) production, and the peak values of H 2 O 2 and OH were 22.95 % and 55.30 % higher than those of the control group, respectively. After 65 days, the relative abundances of representative ARGs decreased by 56.12 % in the nZVI group (with BC-nZVI added). An analysis of bacterial communities and networks revealed that Actinobacteria, Proteobacteria, and Firmicutes were the main hosts for ARGs, and BC-nZVI weakened the link between ARGs and host bacteria. Distance-based redundancy analysis showed that BC-nZVI altered the microbial community structure through environmental factors and that most ARGs were negatively correlated with ROS, suggesting that ROS significantly affected the relative abundance of ARGs. According to these results, BC-nZVI showed potential for decreasing the relative abundance of ARGs in composting., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, novel walnut shell biochar-nano zero-valent iron nanocomposites (WSBC-nZVI) were synthesized using a combined pyrolysis/reduction process. WSBC-nZVI displayed a high removal efficiency (86 %) for carbamazepine (CBZ) compared with walnut shell biochar (70 %) and nano zero-valent iron (76 %) in the presence of persulfate (PS) (0.5 g/L catalyst, 10 mg/L CBZ, 1 mM persulfate). Subsequently, WSBC-nZVI was applied for the fabrication of the membrane using a phase inversion method. The membrane demonstrated an excellent removal efficiency of 91 % for CBZ in a dead-end system (2 mg/L CBZ, 1 mM persulfate). In addition, the effect of various operating conditions on the degradation efficiency in the membrane/persulfate system was investigated. The optimum pH was close to neutral, and an increase in CBZ concentration from 1 mg/L to 10 mg/L led to a drop in removal efficiency from 100 % to 24 %. The degradation mechanisms indicated that oxidative species, including 1 O 2 , OH, SO 4 - , and O 2 - , all contribute to the degradation of CBZ, while the role of 1 O 2 is highlighted. The CBZ degradation products were also investigated, and the possible pathways and the predicted toxicity of intermediates were proposed. Furthermore, the practical use of the membrane was validated by the treatment of real wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Chromium (Cr) accumulating in soil caused serious pollution to cultivated land. At present, nano zero-valent iron (nZVI) is considered to be a promising remediation material for Cr-contaminated soil. However, the nZVI impact on the behavior of Cr in the soil-rice system under high natural geological background value remains unknown. We studied the effects of nZVI on the migration and transformation of Cr in paddy soil-rice by pot experiment. Three different doses of nZVI (0, 0.001 % and 0.1 % (w/w)) treatments and one dose of 0.1 % (w/w) nZVI treatment without plant rice were set up. Under continuous flooding conditions, nZVI significantly increased rice biomass compared with the control. At the same time, nZVI significantly promoted the reduction of Fe in the soil, increased the concentration of oxalate Fe and bioavailable Cr, then facilitated the absorption of Cr in rice roots and the transportation to the aboveground part. In addition, the enrichment of Fe(III)-reducing bacteria and sulfate-reducing bacteria in soil provided electron donors for Cr oxidation, which helps to form bioavailable Cr that is easily absorbed by plants. The results of this study can provide scientific basis and technical support for the remediation of Cr -polluted paddy soil with high geological background., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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 intI1 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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

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 SO 4 •- 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., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO 2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H 2 O 2 , and pH on formaldehyde degradation were studied. The n-ZVI/TiO 2 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/TiO 2 , and the Fe 2p spectrum of 2%n-ZVI/TiO 2 indicated the presence of Fe 0 . 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 H 2 O 2 , 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 Fe 0 and H 2 O 2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO 2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

There are increasing concerns about microplastic (MP) pollution in the natural environment. Consequently, numerous physicochemical and toxicological studies have been conducted on the effects of MPs. However, few studies have concerned the potential impact of MPs on contaminated site remediation. We herein investigated the influence of MPs on the temporary and post heavy metal removal by iron nanoparticles, including pristine and sulfurized nano zero-valent irons (nZVI and S-nZVI). MPs inhibited adsorption of most heavy metals during the treatment of iron nanoparticles, and facilitated their desorption, such as Pb (II) from nZVI and Zn (II) from S-nZVI. However, such effects presented by MPs was usually less than those by dissolved oxygen (DO). Most desorption cases are irrelevant to the reduced formats of heavy metals involving redox reactions, such as Cu (I) or Cr (III), suggesting that the influence of MPs on metals are limited to those binding with iron nanoparticles through surface complexation or electrostatic interaction. As another common factor, natural organic matter (NOM) had almost no influence on the heavy metal desorption. These insights shed lights for enhanced remediation of heavy metals by nZVI/S-NZVI in the presence of MPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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 Fe 0 @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 Fe 0 @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 •- , 1 O 2 and • OH played a minor role. Importantly, the crucial role of the Fe 2+ /Fe 3+ cycle promoted by the Fe 0 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this study, nano zero-valent iron (nZVI) was used as the Fe 2+ source in the Fenton reaction, and a UV-nZVI-H 2 O 2 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 [H 2 O 2 ] = 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-H 2 O 2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H 2 O 2 system is related to a higher H 2 O 2 utilization rate. The H 2 O 2 residue in the UV-nZVI-H 2 O 2 system was the lowest, and the effective utilization rate of H 2 O 2 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-H 2 O 2 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-H 2 O 2 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-H 2 O 2 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., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Multi-metal contaminated soil has received extensive attention. The biochar and bentonite-supported nano zero-valent iron (nZVI) (BC-BE-nZVI) composite was synthesized in this study by the liquid-phase reduction method. Subsequently, the BC-BE-nZVI composite was applied to immobilize cadmium (Cd), chromium (Cr), and lead (Pb) in simulated contaminated soil. The simultaneous immobilization efficiencies of Cd, Cr(VI), Cr total , and Pb were achieved at 70.95 %, 100 %, 86.21 %, and 100 %, respectively. In addition, mobility and bioavailabilities of Cd, Cr, and Pb were significantly decreased and the risk of iron toxicity was reduced. Stabilized metal species in the contaminated soil (e.g., Cd(OH) 2 , Cd-Fe-(OH) 2 , Cr x Fe 1-x OOH, Cr x Fe 1-x (OH) 3 , PbO, PbCrO 4 , and Pb(OH) 2 ) were formed after the BC-BE-nZVI treatment. Thus, the immobilization mechanisms of Cd, Cr, and Pb, including adsorption, reduction, co-precipitation, and complexation co-exist with the metals. More importantly, bacterial richness, bacterial diversity, soil enzyme activities (dehydrogenase, urease, and fluorescein diacetate hydrolase), and microbial activity were enhanced by applying the BC-BE-nZVI composite, thus increasing the soil metabolic function. Over all, this work applied a promising procedure for remediating multi- metal contaminated soil by using the BC-BE-nZVI composite., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Excessive nitrate has been a critical issue in the water environment, originating from the burning of fossil fuels, inefficient use of nitrogen fertilizers, and discharge of domestic and industrial wastewater. Among the effective treatments for nitrate reduction, electrocatalysis has become an advanced technique because it uses electrons as green reducing agents and can achieve high selectivity through cathode potential control. The effectiveness of electrocatalytic nitrate reduction (NO 3 RR) mainly lies in the electrocatalyst. Iron-based catalysts have the advantages of high activity and low cost, which are well-used in the field of electrocatalytic nitrates. A comprehensive overview of the electrocatalytic mechanism and the iron-based materials for NO 3 RR are given in terms of monometallic iron-based materials as well as bimetallic and oxide iron-based materials. A detailed introduction to NO 3 RR on zero valent iron, single-atom iron catalysts, and Cu/Fe-based bimetallic electrocatalysts are provided, as they are essential for the improvement of NO 3 RR performance. Finally, the advantages of iron-based materials for NO 3 RR and the problems in current applications are summarized, and the development prospects of efficient iron-based catalysts are proposed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The integrated system of microbial electrosynthesis (MES) coupled with chain elongation has been considered a promising platform for carboxylic acids production. However, this biotechnology is still in its infancy, and many limitations are needed to be transcended, such as low electron transfer efficiency between cathode and microbes. In this study, nano zero-valent iron (NZVI) was employed to improve carboxylic acid production in the integrated system, and the promotion mechanisms were revealed. Results suggested that the highest production concentrations of acetate, butyrate, and caproate were observed at 7.5 g/L optimized NZVI dosage, increasing the total yield and coulomb efficiency by 23.7 % and 40.3 % compared to the control. Mechanism studies indicated that the hydrogen and electron released by the anaerobic corrosion of NZVI could be used as additional reducing equivalents, thereby enhancing the electron transfer performance. Besides, NZVI was also proven to facilitate the formation of electroactive biofilms according to the results of biofilm characterization and total DNA. In functional microbes' respect, the moderate NZVI enriched the chain elongator in biofilm, like Clostridium&#95;sensu-stricto&#95;12, and upregulated the activities of key enzymes of homoacetogenesis and chain elongation metabolic pathways, like carbon-monoxide dehydrogenase and hydroxyacyl-CoA dehydratase. This study provided the evidence and revealed how NZVI assisted carboxylic acid production from CO 2 via chain elongation in MES., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In order to reduce the content of Cr(VI) in the soil of the relocated chromium salt factory, the rice straw-derived hydrothermal carbon was prepared by hydrothermal method and loaded with nano zero-valent iron generated by liquid phase reduction, which effectively alleviated the self-aggregation problem of nano zero-valent iron (nZVI) in the treatment of Cr(VI) and improved the Cr(VI) reduction rate without changing the soil structure. The reduction effect of Cr(VI) in soil by key influencing factors such as carbon-iron ratio, initial pH value, and initial temperature was investigated. The results showed that nZVI modified hydro-thermal carbon composite (named RC-nZVI) had a good reduction effect on Cr(VI). Scanning electron microscope (SEM) and energy spectrum analysis showed that nZVI was evenly distributed on the surface of hydrothermal carbon, which effectively reduced the agglomeration of iron. Under the conditions of C/Fe = 1:2, 60 °C, with pH of 2, the average Cr(VI) content in soil decreased from 182.9 mg kg -1 to 21.6 mg kg -1 . Adsorption kinetics of Cr(VI) by RC-nZVI fit well with the pseudo-second-order model, and the kinetic velocity constant revealed that Cr(VI) reduction rate decreased with increasing initial Cr(VI) concentration. Cr(VI) reduction by RC-nZVI was mainly dominated by chemical adsorption.

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, [H 2 O 2 ] = 10 mM. pH correction was not performed (pH = 3.2). Afterwards, the remaining Fenton sludge, which was thermally treated (named FS treated ), 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, FS treated 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.

Activated carbon-supported nano-zero-valent iron (nZVI@AC) is considered to be one of the most promising materials for in-situ remediation of pollutants in aqueous environment, while liquid phase reduction (LPR) is one of the most commonly used preparation methods for nZVI@AC. However, the complex operation and the requirement of various agents limit the practical application of the traditional liquid-phase reduction (TLPR). In this study, an improved liquid phase reduction method (ILPR) was proposed, which was characterized by solid-state dosing of reducing agents. Compared with TLPR, ILPR simplified the preparation process, while there was no requirement of polyethylene glycol and ethanol. When the Cd(II) removal efficiency was used as the evaluation index, the preferred parameters of ILPR were as follows: AC/FeSO 4 ·7H 2 O mass ratio was 15:1; NaBH 4 dosage was 8 g; ultrasonic time was 1 h; stirring time was 20 min. Moreover, the Cd(II) removal efficiency of nZVI@AC prepared by ILPR (nZVI@AC-I) was greater than 92.00%, which was superior to that of nZVI@AC prepared by TLPR (nZVI@AC-T). The characterization results showed that the pore parameters, surface functional groups and iron contents of nZVI@AC-I and nZVI@AC-T were basically the same. However, the distribution of iron-containing particles on the surface of nZVI@AC-I was more uniform. Furthermore, the Fe 0 in nZVI@AC-I had a smaller particle size and a higher content. Overall, this study provided a promising approach for nZVI@AC preparation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The mobility of nano zero-valent iron (nZVI) will greatly affect its practical application as a remediation material for contaminated groundwater. One-dimensional (1D) column tests are commonly used in previous work to study its migration behavior, but the two-dimensional (2D) test is still very limited. This study reports a novel research system to study the 2D transport and retention behavior of colloids and solutes, which includes a 2D model test setup and the corresponding image analysis method. The transport behaviors of methyl orange (MO), nZVI, and phosphate-loaded nZVI (PnZVI) are studied using this system. The results show that the research system can reasonably describe the tempo-spatial concentration distribution of colloids and solutes. After phosphate adsorption, the mobility of nZVI is enhanced due to the increase in negative surface charge, which implies a potential environmental risk of nZVI to facilitate contaminant transport. The migration of PnZVI is not significantly influenced by its density, which is faster than MO in the longitudinal direction. The range of the plume of PnZVI in the longitudinal direction is larger than that of MO, which implies that PnZVI has a stronger longitudinal dispersion than MO.

This study evaluates the NO 3 - removal from groundwater through Heterotrophic Denitrification (HDN) (promoted by the addition of acetate and/or an inoculum rich in denitrifiers) and Abiotic Chemical Nitrate Reduction (ACNR) (promoted by pulse injection of zerovalent iron nanoparticles (nZVI)). HDN and ACNR were applied, separately or combined, in packed soil column experiments to complement the scarce research on pulse-injected nZVI in continuous-flow systems mimicking a Well-based Denitrification Barrier. Together with NO 3 - , the removal of two common pesticides (dieldrin and lindane) was evaluated. Results showed that total NO 3 - removal (>97%) could be achieved by either bioestimulation with acetate (converting NO 3 - to N 2 (g) via HDN) or by injecting nZVI (removing NO 3 - via ACNR). In the presence of nZVI, NO 3 - was partially converted to N 2 (g) and to a lower extent NO 2 - , with unreacted NO 3 - being likely adsorbed onto Fe-(oxy)hydroxides. Combination of both HDN and ACNR resulted in even a higher NO 3 - removal (>99%). Interestingly, nZVI did not seem to pose any toxic effect on denitrifiers. These results showed that both processes can be alterned or combined to take advantage of the benefits of each individual process while overcoming their disadvantages if applied alone. With regard to the target pesticides, the removal was high for dieldrin (>93%) and moderate for lindane (38%), and it was not due to biodegradation but to adsorption onto soil. When nZVI was applied, the removal increased (generally >91%) due to chemical degradation by nZVI and/or adsorption onto formed Fe-(oxy)hydroxides., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Nano zero-valent iron loaded porous carbon derived from microplastics was designed as heterogeneous catalyst for degradation of persistent organic pollutants. Controlled carbonization of microplastics with molten salt was conducted to tune the morphology of carbon product. Controlled carbonization induces higher carbon yield (from 17.73% to 52.24%) and larger surface area (from 403.72 m 2 /g to 601.82 m 2 /g). The catalyst (Fe/MMPC) was characterized by Raman, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope. Loading nano zero-valent iron onto porous carbon are verified in the catalyst. The process factors including Fe/MMPC dosage, H 2 O 2 , pH, anions, and temperature were studied to estimate the catalytic performance. Tetracycline degradation (81.8% within 10 min) is effectively obtained in the Fe/MMPC and H 2 O 2 system. The apparent rate constant is 0.1311-0.2999 min -1 under different temperature, and the activation energy of catalytic process is 22 kJ/mol. Pollutants including rhodamine B, p-nitrophenol, and butylxanthate are efficiently degraded in the catalytic system. The predominant species of catalytic reactions are hydroxyl radicals, which are mainly produced from H 2 O 2 activation enhanced by zero-valent iron in Fe/MMPC. This work offers an innovative strategy for microplastic management and wastewater treatment., (Copyright © 2022. Published by Elsevier Ltd.)

In this study, an aerosol-assisted Fe 0 /C (carbon supported zero-valent iron) composite was prepared and evaluated, which could effectively remove nitrate and exhibit high nitrogen selectivity. The results show that the selectivity of nitrogen for freshly prepared Fe 0 /C composites could reach 52.2% when pH at 7, compared to that of 7.7% for traditional nZVI. Meanwhile, the removal efficiency of nitrate was slightly increased from 63.5% to 69.9%. Furthermore, a variety of methods such as SEM, TEM, XRD, XPS, BET, FTIR and TGA were used to characterize the Fe 0 /C composites before and after reaction. Hence, the following key factors were determined for the effective conversion from nitrate to nitrogen: the surface of zero valent iron particle should be protected from oxidation and its genuine characteristics are well retained; the reaction should be controlled under an anaerobic condition; and the carbon as the carrier to support iron particles is very important; lower initial pH favors nitrogen generation. Various materials including aged Fe 0 /C composites, Fe 0 /SiO 2 (SiO 2 supported zero-valent iron) composites and nZVI particles in the deoxygenated and oxygenated systems were assessed for comparison., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The overuse of chromium (Cr) has significantly negatively impacted human life and environmental sustainability. Recently, the employment of nano zero-valent iron (nZVI) for Cr(VI) removal is becoming an emerging approach. In this study, carbonized melamine foam-supported nZVI composites, prepared by a simple impregnation-carbonization-reduction method, were assessed for efficient Cr(VI) removal. The prepared composites were characterized by XPS, SEM, TEM, BET and XRD. Batch experiments at different conditions revealed that the amount of iron added, the temperature of carbonization and the initial Cr(VI) concentration were critical factors. Fe@MF-12.5-800 exhibited the highest removal efficiency of 99% Cr(VI) (10 mg/L) at neutral pH among the carbonized melamine foam-supported nZVI composites. Its iron particles were effectively soldered onto the carbonaceous surfaces within the pore networks. Moreover, Fe@MF-12.5-800 demonstrated remarkable stability (60%, 7 days) in an open environment compared with nZVI particles.

The in-situ hydrogen supply by nano zero-valent iron (nZVI, nFe 0 ) corrosion provided a feasible way to improve the efficiency of biogas biological upgrading. This work studied the effects of nZVI at different dosages (0, 2, 4, 6, 8 and 10 g/L) on anaerobic digestion of kitchen wastewater by two buffer systems 2-[4-(2-hydroxyethyl) piperazin-1-yl] ethanesulfonic acid (HEPES) and sodium hydrogen carbonate (NaHCO 3 ). The addition of nZVI improved the content of methane (CH 4 ) and stability of anaerobic digestion process. In HEPES buffer system, the CH 4 was all increased and the maximum reached 90.51% with 10 g/L nZVI, higher than 32.25% compared to the control. The maximum hydrogen enrichment (HE) was 113 ppb after nZVI addition, indicating the mass transfer efficiency of hydrogen (H 2 ) was improved. Microbial community analysis showed that the total relative abundance of Methanobacterium and Methanolinea at 10 g/L nZVI was 53.72%, which was 1.62 times of the control group. However, in the NaHCO 3 buffer system with 10 g/L nZVI addition, the content of CH 4 and the loosely bound extracellular polymeric substances (LB-EPS) was lower than the control. The results indicated that the addition of nZVI was feasible for biogas upgrading, and the bidirectional effect of nZVI on the promotion or inhibition of bio-methanation might be related to the buffer system of the anaerobic process., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This study explores the green synthesis of nano zero-valent iron (nZVI) extracted from the peel of selected waste fruits: banana (BP), mango (MP), and pomegranate (GP), for the removal of nutrients from aqueous environments. The extract was prepared by heating de-ionised water at 60°C for 5 min, adding a reducing and a stabilising agent, FeCl 3 , then stirring with a N 2 gas flush solution to form iron nanoparticles, with a final drying step under N 2 conditions. Using a variety of characterisation techniques, it was determined that nZVI particles were successfully synthesised via the reduction of iron (III) to iron (0) and stabilised by the presence of phenolic compounds in the extract. The removal of 20 mg/L nutrients from an aqueous solution carried out using the nZVIs resulted in nitrate removal of 92% (nZVI-GP), 88% (nZVI-BP), and 72% (nZVI-MP) within 5 min, whereas ∼98% phosphate was removed by all three nZVIs within 60 min. The aging effect was also tested. Aging the nZVIs for >20 days resulted in less efficient phosphate adsorption after exposure for 250 min; ∼70% phosphate removal was achieved using the nZVIs under these conditions. The mechanisms and pathways of nitrate reduction, including the adsorption of phosphate by nZVI were demonstrated, and discussed. Leachability tests of the phosphate-loaded nZVIs revealed that 10%, 28%, and 48% phosphate was released from the nZVI-GP, nZVI-BP, and nZVI-MP particles, respectively. Using waste fruit is, therefore, a viable and sustainable alternative to the traditional sodium borohydride method to produce nZVIs for environmental application.

Antibiotic fermentation residue (AFR) has been categorized as hazardous waste in China. Anaerobic biohydrogen fermentation may be a promising technology for handling AFR, which could achieve dual goals of waste treatment and clean energy production at the same time. However, the low hydrogen yield and low removal efficiency of residual antibiotics are two major factors limiting the AFR biohydrogen fermentation process. This work firstly applied gamma radiation (50 kGy) to remove the residual antibiotic in AFR and improve the bioavailability of organic matters, then adding nano zero-valent iron (nZVI) (100-1000 mg/L) to further enhance the AFR biohydrogen fermentation performance. Results showed that residual deacetoxycephalosporin C in AFR was removed with a high efficiency of 98.6%, and hydrogen yield achieved 20.45 mL/g-VS added with the combined approach of gamma radiation pretreatment and 500 mg/L nZVI addition, which was 139.2% higher compared to the control experimental result. The combined approach also promoted the biohydrogen production rate, decreased the lag phase of hydrogen production, and increased the organics utilization. Microbiological analysis revealed that highly efficient hydrogen-producing genera Clostridium sensu stricto were enriched in much higher abundance with the combined approach, which might be the fundamental mechanism for the enhanced AFR fermentation performance., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Periodate (PI)-based advanced oxidation processes have recently received increasing attentions. Herein, PI was readily activated by nano zero-valent iron (nZVI) and subsequently led to the enhanced oxidation of organic contaminants, with the removal performance of sulfadiazine (SDZ) in the nZVI/PI process even higher than that in the nZVI/peroxydisulfate process under identical conditions. Kinetic experiments indicated that the decay of SDZ was susceptible to the dosage of nZVI and PI, but was barely affected by pH values (4.0-7.0) under buffered conditions, suggesting the promising performance of the nZVI/PI process in a relatively wide pH range. Selective degradation of contaminants and 18 O-isotope labeling assays collectively demonstrated that iodate radical ( • IO 3 ), high-valent iron-oxo species (Fe(IV)) and hydroxyl radical ( • OH) were responsible for the abatement of organic contaminants. More importantly, due to the relatively weak steric hindrance effect of PI, PI easily adsorbed on the surface of nZVI and no iron leaching was detected throughout the reaction, implying that PI activation induced by nZVI was a surface-mediated process. Besides, PI was not transformed into harmful reactive iodine species. This study proposed an environmental-friendly approach for PI activation and shed new lights on the PI-based processes., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Arsenic (As) and antimony (Sb) are usually coexistent in mine wastes and pose a great threat to human health. The As immobilization by nano zero-valent iron (nZVI) is promising, however, the stabilization for co-occurring As and Sb is not known. Herein, the immobilization and transformation of As and Sb in nZVI-treated sediments were evaluated using complementary leaching experiments and characterization techniques. Raw sediment samples from a gold-antimony deposit revealed the co-existence of ultrahigh As and Sb at 50.3 and 14.9 g/kg, respectively. Leaching results show that As was more efficiently stabilized by nZVI than Sb, which was primarily due to the soluble fraction that was readily absorbed by nZVI of As was higher. As the nZVI treatment proceeds, the oxidation and reduction of As and Sb occur simultaneously as evidenced by XPS analysis. The primary oxidant, hydroxyl radicals, was detected by EPR studies, proving the occurrence of nZVI induced Fenton reaction. This study sheds light on differences in the interaction and immobilization of nZVI with Sb and As in co-contaminated sediments., (Copyright © 2021. Published by Elsevier B.V.)

In this paper, the effects of several groundwater components (heavy metals, inorganic anions, and organics) on the cytotoxicity of nanoscale zero-valent iron (NZVI) towards Escherichia coli (E. coli) under aerobic/anaerobic conditions were studied. The results showed that NZVI exhibited much higher toxicity in anaerobic conditions than aerobic conditions. Under the state of air-saturation, corrosion of NZVI occurred rapidly, at the same time, it could stably and continuously generate Fe (Ⅱ) and trigger reactive oxygen species (ROS), which led to oxidative stress in E. coli. While in the deareated state, the TEM images showed that the integrity of the cell membrane was destroyed, which validated that the main mechanism of NZVI cytotoxicity was the rapid membrane damage of E. coli. The presence of Cr (Ⅵ) reduced the toxicity of NZVI through oxidation-reduction with NZVI, especially under anaerobic conditions. In contrast, the presence of Cd (Ⅱ) could be adsorbed onto NZVI to increase the cytotoxicity of NZVI. The presence of phosphate and humic acid greatly improved the survival rate of E. coli through the complex reaction with Fe (Ⅱ), especially under aerobic conditions. On the one hand, the formed Fe (II)-phosphate/humic acid complex could reduce the production of ROS. On the other hand, the complex accumulated on the outer surface of E. coli cells could provide steric hindrance to impede the contact between NZVI and cell. These findings were crucial for practical significance to evaluate environmental risk during the groundwater remediation process by using NZVI., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, the biochar (BC) supported Fe-Cu bimetallic stabilized by PVP (Fe-Cu/PVP/BC) were prepared and utilized to enhance the nitrate (NO 3 - ) removal and the selectivity toward nitrogen (N 2 ). Results showed the optimum Fe:Cu:BC ratio and the dosage of the BC (pyrolysis at 700 °C) supported Fe-Cu bimetallic stabilized by polyvinylpyrrolidone (PVP) (Fe-Cu/PVP/BC 700 ) were respectively 1:2:3 and 1 mg L -1 with the selectivity toward N 2 of 31 %. This was mainly due to the synergy among Fe 0 , Cu 0 and BC in the Fe-Cu/PVP/BC. The addition of Fe 0 could reduce the NO 3 - through providing electron. The Cu 0 and BC improved the selectivity of NO 3 - to N 2 through forming [Cu-NO 2 - ads ] and adjusting redox potential. The addition of Fe-Cu/PVP/BC could supply electrons for denitrification and enhance the relative abundances of Azospira and Thauera related to denitrification to improve NO 3 - removal. This result was further confirmed by the variations of denitrifying functional genes (narG, nirK, nirS and nosZ). This research provided an effective method to improve NO 3 - removal during surface water treatment in constructed wetlands (CWs) by adding Fe-Cu/PVP/BC., (Copyright © 2021 Elsevier Ltd. All rights reserved.)