Zero-valent Iron Research Articles

Magnet-assisted nanoscale zerovalent iron soil washing in chlorpyrifos-contaminated soil remediation: Proof of concept

Chlorpyrifos (CPF)––a widely used organophosphate pesticide––is banned in many countries due to its persistence in the environment and high toxicity. Residue levels often vastly exceed safety thresholds, posing significant risks to human health and ecosystems. This persistent contamination challenges farmers, especially those transitioning to organic practices. Here, we propose magnet-assisted soil washing with nanoscale zerovalent iron (nZVI) for the rapid remediation of CPF-contaminated soil. Soil mixed with water and nZVI facilitates CPF adsorption and degradation, with the CPF-sorbed nZVI being magnetically separated. We tested various nZVI conditions (inactivated [IZ] and activated [AZ], with and without hydrogen peroxide [H2O2]) against controls, including untreated soil and conventionally washed soil. The control experiments showed that conventional washing without nZVI removed 50.54 ± 3.48 % of the CPF via volatilization, leaving CPF residues in the soil (25.44 ± 2.12 %) that were above the maximum contamination level (MCL). Inactivated nZVI increased the removal by 24.38 ± 0.78 % via CPF sorption, but the MCL was still exceeded. However, AZ or nZVI with H2O2 achieved complete CPF removal (>99.95 %) within 180 min, reducing its concentration to below the MCL (<0.03 mg/kg). Thus, CPF sorption followed by either reductive dechlorination or oxidative degradation proved effective. Additionally, nZVI demonstrated reusability for three rounds while mitigating CPF toxicity, improving seed germination and plant growth. This method offers a promising solution for rapid soil decontamination, supporting the transition to organic farming.

Overlooked pyrite-mediated heterogeneous Fenton processes: Mechanisms of surface hydroxyl radical generation and associated decontamination performance

Pyrite-based Fenton-like processes have been extensively studied for wastewater decontamination; however, most relevant studies placed excessive emphasis on the homogeneous Fenton reaction mediated by aqueous Fe2+, resulting in the proposed technologies facing issues such as additional acid requirements for pH adjustment and excessive iron sludge production. Herein, through in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), custom dual-chamber reactor experiments, and a series of control experiments, significant hydroxyl radical generation was identified during the pyrite/H2O2 process, while the dominant reactive iron species was verified to the structural Fe sites on the pyrite surface, rather than structural Fe(II) in secondary iron minerals and surface adsorbed Fe2+. Consequently, even with significant suppression of the homogeneous Fenton pathway, the pyrite/H2O2 process exhibited significant degradation efficiency for sulfamethoxazole (SMX) at pH 4. Moreover, the pyrite/H2O2 process was found to selectively remove 50 μM of pollutants with high affinity for pyrite (bisphenol A, carbamazepine, nitrobenzene, and SMX), even in the presence of 50–100 mM methanol. Compared to the typical iron-based reductive catalyst (zero-valent iron, ZVI), pyrite mediated a Fenton process with greater potential for practical applications at pH 4, achieving a 43.75-fold reduction in iron sludge production and almost doubling the H2O2 utilization efficiency. Additionally, in contrast to ZVI, minimal iron oxide formed on the pyrite surface during the oxidation process. Thus, after seven cycles of degradation experiments, the decontamination efficiency of the pyrite/H2O2 process remained stable. These findings are crucial for understanding the complex environmental behavior of pyrite in both natural and engineering processes and provide a new perspective for the efficient utilization of pyrite resources as well.

Rapid Oxidative Dissolution of Zerovalent Iron Induced by Sulfite for Efficient Removal of Arsenate and Arsenite: Selective Formation of Scorodite.

In this study, we proposed a moderate oxidation strategy for accelerating the oxidative dissolution of zerovalent iron (ZVI) using sulfite (S(IV)), thereby improving the removal of As(V) and As(III). Results revealed that, in the presence of 2.0 mM S(IV), both As(V) and As(III) were selectively converted into scorodite at pH0 3.0-7.0, while As(III) oxidation and As(V) immobilization were impressed over pH0 8.0-10.0. Batch experiments, radical quenching experiments, and electron spin resonance (ESR) measurements demonstrated that ZVI initially boosted S(IV) activation to generate SO4•-, •OH, and protons, and in turn, ZVI was further oxidized more intensely by these radicals than by oxygen. Concurrently, substantial protons derived from S(IV) oxidation neutralized hydroxyls produced by ZVI oxidation, maintaining an acidic environment conducive to the generation of scorodite rather than iron (hydr)oxides. Characterizations of X-ray diffraction (XRD), Raman, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) confirmed that scorodite was formed in situ and then exfoliated from the surface of ZVI, and approximately 75% of ZVI could still be recovered, which contributed to efficient As removal in successive runs and real As-polluted wastewater. The application of S(IV) achieved a balance among ZVI reactivity improvement, As(V)/As(III) removal, and raw material consumption, making it a promising approach for addressing arsenic contamination in wastewater treatment.

Understanding the transitional phase of nitrate removal in three different specialty adsorbents for stormwater treatment

Excess nitrogen input from nonpoint sources driven by hydrologic and anthropogenic disturbances has become a significant ecological challenge in receiving water bodies. Moreover, nitrate removal by cost-effective filtration media has still not performed up to expectation because of the knowledge gap in the transitional phase from physicochemical to microbiological processes. This study developed three cost-effective, sustainable, and adaptable green sorption media (GSM), namely CPS (clay–perlite with sand sorption media), ZIPGEM (zero-valent iron and perlite green environmental media), and BIPGEM (biochar, zero-valent iron, and perlite-based green environmental media), made of readily available and recyclable materials, to compare nitrate removal methods for stormwater treatment and elucidate the transitional phase. The primary adsorption mechanism was chemisorption, and subsequent biofilm growth sustained removal efficiency for a long-lasting period. Adsorption kinetics, adsorption equilibrium, material characterization, and fixed-bed column experiments with a 2-stage cultivation approach were undertaken to characterize the transitional phase in these GSM, based on breakthrough curves, maximum adsorption capacity, and microbial population dynamics for nitrification and denitrification. As shown in the column study, BIPGEM had the highest adsorption capacity (7.637 mg∙g−1), followed by ZIPGEM (2.16 mg∙g−1), and CPS (0.1798mg∙g−1). The biochar in BIPGEM provides a better cultivation environment for nitrifying and denitrifying bacteria, contributing sufficient electron donors. Biofilm production and maturation enabled the BIPGEM to maintain 30 % nitrate removal in a steady state even after 2000 h of operation in the first stage. When the biofilm reached maturation, BIPGEM’s nitrate removal percentage was up to 70 % via denitrification in the second stage.

Application of central composite design for the simultaneous removal of tetracycline and cefixime using nanoscale zero-valent iron modified by montmorillonite and graphene oxide

Application of central composite design for the simultaneous removal of tetracycline and cefixime using nanoscale zero-valent iron modified by montmorillonite and graphene oxide

The beginning of iron corrosion - high-resolution visualization with 3D electron tomography

Understanding the genesis and early-phase reactions of iron corrosion is essential for the early detection, mitigation and prevention of metal degradation. In this work, high-resolution 3D tomography of metallic iron oxidation was acquired using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In particular, dendritic capillaries (<0.5 nm) were observed during the initial oxidation of fresh nanoscale zero-valent iron due to the differential oxygen diffusion and iron atoms migration. This observation led to the proposal of a nanoscale “pothole” model for early-phase corrosion, wherein hollowing out of the metal nanoparticle and formation of nanovoids beneath the iron/oxide interface through Kirkendall effect. Coalescence of the nanocapillaries results in the ultimate collapse of metal structure and/or functional failure. Using nanoscale zero-valent iron as a research model, this work provides unprecedented insights into the nano- and atomic-scale mechanisms of iron oxidation, paving the way for advanced detection and prevention strategies for iron corrosion.

Solidification of concentrated zero-valent iron slurry: A microrheology study using diffusing wave spectroscopy

Concentrated zero-valent iron (ZVI) slurries (CIS) are commonly encountered during the water treatment using ZVI, in the processes such as delivery, settling, and pumping of the ZVI slurry; about the CIS, knowledge about their rheology is critical to the operation of these processes, but little is known about this aspect so far. Herein, microrheology of the CIS of four different ZVI is studied using diffuse wave spectroscopy (DWS). Results show that the CIS of two iron nanoparticles solidify immediately after their separation from water (<3 h), with a fast growth of macroscopic viscosity and a rapid weakening of the fluidity; the CIS of the microscale ZVI (mZVI) is nearly pure viscous or liquid-like and solidifies slower than the nanoparticle CIS; CIS of the floc modified ZVI (mZVI(floc)) is viscoelastic and remains stable in rheology over an extended period up to four days. Such differences in CIS rheology are explained by the coarse surface of the nanoparticle aggregates, the smooth surface of mZVI particles, the intertwined floc coating of mZVI(floc) particles, and the corresponding disparity in surface friction between the particles or aggregates. The solidification of CIS is explained by the binding effect of the oxidation products of the ZVI-water reaction. This study provides information about CIS rheology and offers guidance for process operations in the water treatment using ZVI. This study also shows that the DWS technique is informative in characterizing CIS and the method may be equally applicable for studying other concentrated particle slurries in water treatment.

Mechanism of dual reduction centers containing nano zero-valent iron and single-atom iron carbon spheres for removing hexavalent chromium from water

The passivation and agglomeration issues of ZVI were effectively addressed through the preparation of a carbon-coated material (ZVI/BC-0.8–800) containing embedded iron atoms and nZVI，which exhibits excellent reducing properties towards Cr(Ⅵ). Our results demonstrate that ZVI/BC-0.8–800 possesses iron atoms and nZVI, achieving a remarkable removal rate of 99.8 % for Cr(Ⅵ) within 20 minutes, surpassing that achieved by commercial nZVI. Moreover, nearly all Cr(Ⅵ) is reduced to Cr(III). After ageing different water bodies or in the air for 15 days, the removal rate of ZVI/BC-0.8–800 remains at approximately 70 % when placed in water reaches up to 95 % in air. This efficient and stable removal is due to the protective effect of carbon materials, and the presence of iron atoms and nZVI as the double reduction center in the Cr(Ⅵ) removal process, which enhances the reduction effect. The respective contribution rates from iron atoms and nZVI are 29.13 % and 50.32 % respectively. Overall, this multi-form composite with double reduction centers consisting primarily of nZVI embedded within a carbon material holds great promise for in-situ groundwater remediation applications.

Simultaneous removal of Cd(II) and phosphate by nanoscale zero-valent iron from solution: Co-sorption and implication of corrosion

Nanoscale zero-valent iron (nZVI) has been extensively utilized in environmental remediation, but its reactivity in the presence of co-contaminants requires further investigation for effective application in complex environments. Here, we conducted batch removal experiments to systematically investigate the co-removal behaviors of Cd(II) and phosphate by nZVI. Results showed that nZVI can synergistically remove Cd(II) and phosphate in solution, with the removal efficiency of Cd(II) and phosphate in the binary system being approximately 2 and 5 times higher than those in the single system, respectively. Sequential removal experiments combined with characterization analysis revealed the co-sorption of Cd(II) and phosphate onto the corrosion product of nZVI mainly by forming the ternary complexes (≡Fe–P–Cd). The Fe(OH)2 formed as the initial nZVI corrosion product provides numerous active sites for immobilization of Cd(II) and phosphate. Such effective co-sorption of Fe(OH)2 inhibits its subsequent phase transformation to Fe3O4. Overall, our work sheds light on how nZVI, Cd(II), and phosphate interact in solution as well as highlights the influence of phase transformation on co-removal, which can broaden the potential applications of nZVI in the practical environment.

Highly efficient removal of 1,1,1-trichloroethane from simulated groundwater by polydopamine-modified iron/polylactic acid/biochar composite coupling with Shewanella oneidensis MR-1

Biochar (BC) loaded with nanoscale zero-valent iron (nZVI) has been extensively used to remove chlorinated hydrocarbons from groundwater through biotic/abiotic reductive dechlorination. However, the rapid deactivation due to surface passivation, hydrophobicity, and inadequacy of carbon sources severely limits its practical application. Herein, a novel polydopamine (PDA)-modified iron/polylactic acid (PLA)/biochar composite (PDA@OBC-nZVI) was successfully synthesized to address this issue. Its effect and mechanism for 1,1,1-trichloroethane (1,1,1-TCA) removal from simulated groundwater coupling with Shewanella oneidensis MR-1 (MR-1) were investigated. Results showed that nZVI and PLA particles were uniformly dispersed on the BC surface, being smoother after PDA coating. The composite coupling with MR-1 exhibited efficient and long-term performances for 1,1,1-TCA removal. Under the experimental conditions comprising 10 % PLA mass fraction in the composite, 10 g·L−1 composite dosage and 20 mL·L−1 MR-1 inoculum volume, 83.14 % of 100 mg·L−1 1,1,1-TCA was removed by PDA@OBC-nZVI + MR-1 within 360 h, compared to only 48.12 % by PDA@OBC-nZVI alone. The primary removal pathways included the rapid chemical reductive dechlorination and the long-term microbial dissimilatory iron reduction. The synergistic dechlorination mechanism was manifested in the composite providing sustained carbon sources, accelerating electron transfer, raising sorbed Fe(II) level, and promoting cytochrome c secretion by MR-1. The novelty of this study is enhancing the hydrophilicity and redox activity of carbon-iron composites by PDA modification for the first time in 1,1,1-TCA removal. Overall, the results suggest that PDA@OBC-nZVI + MR-1 can effectively promote the reductive dechlorination process, being great potential for the remediation of chlorinated hydrocarbon-contaminated groundwater.

Efficient reduction of antibiotic resistance genes and mobile genetic elements in organic waste composting via fenton-like treatment

Livestock manure harbors antibiotic resistance genes (ARGs), and aerobic composting (AC) is widely adopted for waste management. However, mitigating ARG resurgence in later stages remains challenging. This work aims to curb ARGs rebounding through a Fenton-like reaction during food waste and swine manure co-composting. Results revealed that 0.025 % zerovalent iron (ZVI) + 0.5 % hydrogen peroxide (H2O2) facilitated maximum ARG, mobile genetic elements (MGEs), and 16 s rRNA removal with reductions of 2.68, 2.69, and 1.4 logs. Spectroscopic analysis confirmed Fenton-like reaction and cell apoptosis analysis indicated that 0.025 % ZVI and 0.5 % H2O2 treatment had the maximum early apoptosis, least observed, and normal cells on day 30. Redundancy analysis highlighted the influence of bacterial communities and physicochemical properties on ARGs, with MGEs playing a crucial role in Fenton treatments. Our findings suggest incorporating ZVI and H2O2 in composting can significantly reduce ARGs and enhance waste management practices.

Synergistic scavenging of sulfamethoxazole and hexavalent chromium in groundwater sample induced by iron-char composites activated persulfate triggering dominant electron transfer process

Effectively scavenging combined pollutants in complex water matrix via dominant electron transfer pathway using modified zero-valent iron (ZVI) remains challenging. Herein, novel iron-based catalysts were synthesized using ball milling and pre-oxidation modified biochar (MOBC), which featured abundant pore structure and oxygen-rich functional moieties to support nZVI in activating persulfate (PS). The most suitable catalytic system achieved ultrafast simultaneous removal of 89.0 % of sulfamethoxazole (SMX) and nearly 100 % of hexavalent chromium (Cr(VI)) within 5 min (with nearly complete removal of SMZ and Cr(VI) in 60 min). By serving as an electron shuttle, MOBC700 could accelerate electron transfer from SMX to PS adsorbed on the nZVI1.0@MOBC700 for SMX decomposition, with reactive oxygen species (ROSs) also contributing. Moreover, nZVI facilitated the reduction of Cr(VI) adsorbed on nZVI1.0@MOBC700 through electron transfer. The dissolved Fe(II) generated via PS activation and Cr(VI) reduction further facilitated Cr(VI) removal from the solution, while the gradual consumption of excess Fe(II) ensured continued ROSs-mediated degradation of SMX. Additionally, the system also demonstrated resistance to interference from NO3-, CO32-, and humic acid, and was effective in remediating four different water samples. Overall, this study presents a promising method for designing iron-char composites to address combined antibiotic and heavy metal contamination in groundwater samples via dominant electron transfer process.

Discarded substrates from soilless hydroponic horticulture as potential amendments for metal-contaminated soils

Soil contamination with metals is a major threat for the environment and public health since most metals are toxic to humans and to non-human biota, even at low concentrations. Thus, new sustainable remediation approaches are currently needed to immobilize metals in soils to decrease their mobility and bioavailability. In this work, we explore the application of discarded substrates from hydroponic cultivation, namely coconut shell and a mixture of coconut shell and pine bark, for immobilization of metals (Cd, Cr, Ni, Cu, Pb, Hg, Sb and As) in a naturally contaminated soil from a mining region in Portugal. The immobilization capacity of substrates (added to the soil at 5% mass ratio) was assessed both individually and also combined with other traditional agriculture soil additives (limestone and gypsum, at 2% mass ratio) and nanoparticles of zero-valent iron (nZVI) at 1–3% mass ratio. The overall results obtained after a 30-d incubation showed that the discarded substrates are a viable, economic, and environmental-friendly solution for metal remediation in soils, with the capacity of immobilization ranging from 20 to 91% for the metals and metalloids studied. Furthermore, they showed the capacity to reduce the soil toxicity (EC50 ∼ 6000 mg/L) to non-toxic levels (EC50 > 10000 mg/L) to the bacteria Aliivrio fischeri.

Degradation Efficiency and Mechanism of Tetracycline in Water by Activated Persulfate Using Biochar-Loaded Nano Zero-Valent Iron.

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.

Effect of the Fe0/PMS advanced oxidation system on the removal of aromatic organic compounds

The aromatic organic compounds present in groundwater environments have low contents, high toxicity, long half-lives and stable chemical properties, which increase the difficulty of degradation under natural conditions. In this study, an zero-valent iron activated peroxymonosulfate system (Fe0/PMS) was constructed to remove common aromatic organic compounds in groundwater. The results showed that at an initial pH of 7.0, Fe0=0.3 g/L, PMS= 0.5 mM, and initial concentration of organic matter (C0) =0.1 mM, the removal efficiency of the seven aromatic organic compounds by the Fe0/PMS system reached more than 70 %, which shows good removal ability. Alcohol quenching tests and liquid chromatography time-of-flight mass spectrometry tests showed that the main active oxygen species in the system were SO4•─ and OH•, which could efficiently degrade aromatic organic compounds through electrophilic substitution, hydroxylation, carbonylation and decarboxylation reactions and reduce the biological toxicity of organic compounds in wastewater to a certain extent. In the long-term dynamic reaction process, the removal rate of aromatic organic compounds in actual groundwater by the Fe0/PMS system can be maintained above 75 %, and the complex structure can be effectively destroyed. This research can provide a theoretical basis for the efficient treatment of aromatic organic compounds in groundwater.

Unveiling the kinetics and mechanism of sulfide-modified zero-valent iron activated hydrogen peroxide for phenol degradation

In this study, sulfide-modified zero-valent iron (S-ZVI) synthesized by a two-step process with optimal S/Fe ratio of 0.056 was used to activate hydrogen peroxide (H2O2) to degrade phenol, and the kinetics and reaction mechanism of phenol degradation were investigated under different conditions. Phenol degradation kinetics in S-ZVI/H2O2 system was characterized by an initial lag phase followed by a rapid reaction period, which was accurately described by Logistic regression model, deviating from conventional pseudo-first-order and pseudo-second-order models. Over 80 % of phenol degradation occurred via liquid-phase reactions, predominantly driven by hydroxyl radicals (•OH). The consumption of H2O2 and the removal of total organic carbon (TOC) were both significantly correlated with the total dissolved iron content, underscoring the importance of iron dissolution. The S-ZVI/H2O2 system outperformed other activated H2O2 systems, with a 41.71 %, 35.89 %, and 44.02 % increase in H2O2 utilization efficiency for TOC removal compared to FeSO4, ZVI, and ZVI(H+), respectively. Sulfide-modification of ZVI significantly promoted the sustained release of dissolved iron with a higher proportion of Fe2+, which was identified as a key factor in enhancing H2O2 utilization efficiency. Our findings provide new insight into a better description of the pollutant removal kinetics process in the S-ZVI/H2O2 system and the synergistic effects between S-ZVI and H2O2 for organic pollutant degradation.

Regulating the surface area increase of zero-valent iron (ZVI) during ball milling: A study of the mechanical mechanism and low-carbon milling

This study investigates the effect of milling parameters on the specific surface area (SSA) increase of zero-valent iron (ZVI) powder, which is crucial for its environmental applications. Combining experimental and orthogonal design methodologies, the research explores how the parameters modulate the SSA. The operational factors are analyzed from the perspectives of bead momentum, kinetic energy, and energy efficiency. A regression model is proposed for the precise fabrication of ZVI with predetermined SSA. Furthermore, the study identifies optimized parameters that minimize energy consumption and carbon emissions. The results suggest that the optimal milling time is 10 min, with larger beads (2.0 mm), higher quality beads (0.75 kg), and higher shaft rotational speed (2000 rpm) significantly enhancing SSA. Discrete Element Method (DEM) simulations reveal micro-mechanical interactions, supporting the parameter selection scheme for maximizing SSA. The findings contribute to optimizing the milling process of the ductile ZVI powder for environmental clean-up.

Exploring zero-valent iron nanoparticles (nZVI) for Bisphenol A removal: Experimental investigations and Monte-Carlo simulation insights

ABSTRACT Numerous personal care products contain Bisphenol-A (BPA), a hormone disruptor that ultimately finds its way into waterways. A combination of experimental investigations and Monte-Carlo simulations (MCS) were used to explore zerovalent iron nanoparticles (nZVI) for their removal. The nZVI exhibited an absorption peak (λmax) at 373 nm with a mesoporous structure (pore size 2.138 nm), 159.419 m2 g−1 surface area, and crystalline peaks. The adsorption processes were positively influenced by batch parameters. BPA adsorption on nZVI varied with temperature as predicted by Freundlich and Langmuir isotherms, achieving a maximum adsorption capacity (qmax) of 982.13 mgg−1 at 308 K and pH 2. The adsorption process at 303 and 308 K was physisorption, whereas, at 313 K, it was chemisorption suitably described by pseudo-second-order kinetics. The exothermic and spontaneous nature of the adsorption processes were demonstrated by the negative values of enthalpy (−ΔH°) and free energy (−ΔG°) that decreased with increasing temperatures (308–328 K). The density function theory and MCS studies showed that BPA's phenyl ring, isopropyl, and hydroxyl groups interacted electrostatically with nZVI, specifically crystal plane 121 with the most negative adsorption energy (ΔEads), enhancing BPA removal. Through optimized adsorption mechanisms, nZVI can effectively remove BPA from wastewater.

New insights and enhancement mechanisms of activated carbon in autotrophic denitrification system utilizing zero-valent iron as indirect electron donors

Zero-valent iron acts as an indirect electron donor, supplying ferrous iron for the nitrate-dependent ferrous oxidation (NDFO) process. The addition of activated carbon (AC) increased the specific NDFO activity in situ and ex situ by 0.4 mg-N/(d·g VSS) and 2.2 mg-N/(d·g VSS), respectively, due to the enrichment of NDFO bacteria. Furthermore, AC reduced the nitrous oxide emission potential of the sludge, a mechanism that metagenomic analysis suggests may act as a cellular energy storage strategy. During a 196-day experiment, a total nitrogen removal efficiency of 53.7 % was achieved, which may be attributed to the upregulation of key genes involved in iron oxidation and denitrification. Based on these findings, a model involving pilin, ’nanowires,’ and a cyc2/?→/(FoxE→FoxY)/?→cymA/Complex III/?-mediated pathway for extracellular electron uptake was proposed. Overall, this work provides a feasible strategy for enhancing the nitrogen removal performance of the ZVI-NDFO process.

Lattice-sulfur-impregnated zero-valent iron crystals for long-term metal encapsulation

Lattice-sulfur-impregnated zero-valent iron crystals for long-term metal encapsulation