Rapid Aerobic Inactivation and Facile Removal of Escherichia coli with Amorphous Zero-Valent Iron Microspheres: Indispensable Roles of Reactive Oxygen Species and Iron Corrosion Products

Synergistic effects of a sequential recirculation electrochemical system combined with low-cost UV-LEDs on the gram-negative bacteria inactivation

In this work, an electrochemical system combined with low-cost UV-LEDs was implemented for the inactivation of Escherichia coli and Pseudomonas aeruginosa. The individual elimination of these bacteria was followed by plate counting and flow cytometry, as complementary techniques to establish the cell inactivation and non-viability, respectively. The contribution of the different parts of the disinfection system (anode, cathode, and light) was determined. In addition, the efficiency of the UV-LEDs/GDE/DSA system in the disinfection of an irrigation water sample was studied. It was found that the combination of the electrochemical system with UV-LEDs was highly synergistic (φ > 7), having low electric energy consumptions per order of magnitude (EEO: 1.13 × 10-2 and 1.55 × 10-2 kWh/m3 order). Moreover, some differences in the inactivation kinetics and synergy between E. coli and P. aeruginosa were observed and linked to the structural/morphological characteristics of the two bacteria. Remarkably, the electrochemical system combined with low-cost UV-LEDs inactivated both target microorganisms after only 2 min of treatment. The flow cytometry analyses evidenced the damage to the cell membrane of the bacteria by the simultaneous and synergistic action of the electrogenerated H2O2 and active chlorine species (ACS), plus the attacks of photo-generated reactive oxygen species. This synergistic combination in the UV-LEDs/GDE/DSA system demonstrated remarkable efficiency in the disinfection of an irrigation water sample, achieving the elimination of culturable bacteria in 45 min of treatment. The results of this research demonstrated the capacity and great potential of an easy combination of electrochemistry with UV-LEDs as an alternative system for the elimination of gram-negative bacteria in water.

Highly efficient FeS/Fe3O4 @ biomass carbon bifunctional catalyst with enriched oxygen vacancies for heterogeneous electro-Fenton catalysis

Low H2O2 production, narrow adaptive pH range and slow Fe(II) regeneration on the cathode still limit efficiency of electro-Fenton (EF) and its application. Herein, we designed a bifunctional catalyst with FeS and Fe3O4 nanoparticles dispersed on porous carbon (CFeS@C) using template of sodium alginate (SA)/FeSO4 hydrogel mixed with carbon black (CB), which presented high H2O2 generation efficiency and outstanding tetracycline degradation efficiency under wide pH ranges (3-8) with a low energy consumption of 19.6 kWh/kg total organic carbon (TOC). The introduction of CB created abundant oxygen vacancies in CFeS@C, promoting the oxygen adsorption and the electrochemical generation of H2O2, which further boosted the formation of •OH due to the interaction with Fe2+ on the cathode surface. Simultaneously, the reaction between the outer layer of FeS and Fe3+ not only accelerated iron cycling but also reduced the solution pH. It was verified that •OH and 1O2 played a dominant role in organics degradation. The system maintained stability after 10 cycles and effectiveness in the treatment of pharmaceutical wastewater. This study would offer a new strategy to develop an efficient and durable bifunctional catalyst for heterogeneous EF system working in wide pH conditions for wastewater treatment.

Biological self-protection inspired engineering of nanomaterials to construct a robust bio-nano system for environmental applications

Nanomaterials can empower microbial-based chemical production or pollutant removal, e.g., nano zero-valent iron (nZVI) as an electron source to enhance microbial reducing pollutants. Constructing bio-nano interfaces is critical for bio-nano system operation, but low interfacial compatibility due to nanotoxicity challenges the system performance. Inspired by microorganisms' resistance to nanotoxicity by secreting extracellular polymeric substances (EPS), which can act as electron shuttling media, we design a highly compatible bio-nano interface by modifying nZVI with EPS, markedly improving the performance of a bio-nano system consisting of nZVI and bacteria. EPS modification reduced membrane damage and oxidative stress induced by nZVI. Moreover, EPS alleviated nZVI agglomeration and probably reduced bacterial rejection of nZVI by wrapping camouflage, contributing to the bio-nano interface formation, thereby facilitating nZVI to provide electrons for bacterial reducing pollutant via membrane-anchoring cytochrome c. This work provides a strategy for designing a highly biocompatible interface to construct robust and efficient bio-nano systems for environmental implication.

The mechanism differences between sulfadiazine degradation and antibiotic resistant bacteria inactivation by iron-based graphitic biochar and peroxydisulfate system

In this study, the activation of peroxydisulfate (PS) by K2FeO4-activation biochar (KFeB) and acid-picking K2FeO4-activation biochar (AKFeB) was investigated to reveal the mechanism differences between iron site and graphitic structure in sulfadiazine (SDZ) degradation and ARB inactivation, respectively. KFeB/PS and AKFeB/PS systems had similar degradation property towards SDZ, but only KFeB/PS system showed excellent bactericidal property. The mechanism study demonstrated that dissolved SDZ was degraded through electron transfer pathway mediated by graphitic structure, while suspended ARB was inactivated through free radicals generated by iron-activated PS, accompanied by excellent removal on antibiotic resistance genes (ARGs). The significant decrease in conjugative transfer frequency indicated the reduced horizontal gene transfer risk of ARGs after treatment with KFeB/PS system. Transcriptome data suggested that membrane protein channel disruption and adenosine triphosphate synthesis inhibition were key reasons for conjugative transfer frequency reduction. Continuous flow reactor of KFeB/PS system can efficiently remove antibiotics and ARB, implying the potential application in practical wastewater purification. In conclusion, this study provides novel insights for classified and collaborative control of antibiotics and ARB by carbon-based catalysts driven persulfate advanced oxidation technology.

Promotive Effects of Chloride and Sulfate on the Near-Complete Destruction of Perfluorocarboxylates (PFCAs) in Brine via Hydrogen-tuned 185-nm UV Photolysis: Mechanisms and Kinetics

Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H2) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study discovered the promotive effects of two major brine anions, i.e., chloride and sulfate in VUV/H2 photolysis on the hydrated electron (eaq-) generation and perfluorocarboxylates (PFCAs) destruction and established a kinetics model to elucidate the promotive effects on the steady-state concentration of eaq- ([eaq-]ss). Results showed that VUV/H2 achieved near-complete defluorination of perfluorooctanoic acid (PFOA) in the presence of up to 1000 mM chloride or sulfate at pH 12. The defluorination rate constant (kdeF) of PFOA peaked with a chloride concentration at 100 mM and with a sulfate concentration at 500 mM. The promotive effects of chloride and sulfate were attributed to an enhanced generation of eaq- via their direct VUV photolysis and conversion of additionally generated hydroxyl radical to eaq- by H2, which was supported by a linear correlation between the predicted [eaq-]ss and experimentally observed kdeF. The kdeF value increased from pH 9 to 12, which was attributed to the speciation of the H·/eaq- pair. Furthermore, the VUV system achieved >95% defluorination and ≥99% parent compound degradation of a concentrated PFCAs mixture in a synthetic brine, without generating any toxic perchlorate or chlorate.

Synthesis of stabilized zero-valent iron particles and role investigation of humic acid-Fex+ shell in Fenton-like reactions and surface stability control

Herein, a novel humic acid-Fex+ complex-coated ZVI (HA-Fex+@ZVI) was synthesized and used to activate peroxydisulfate (PDS) for phenol degradation. The HA-Fex+ shell selectively reacted with PDS rather than O2, leading to the formation of modified ZVI with excellent surface stability in storage and ultraefficient PDS activation in advanced oxidation processes (AOPs). As a result, the phenol degradation and PDS activation efficiencies of HA-Fex+@ZVI/PDS were ∼14.4 and ∼1.8 times higher than those of ZVI/PDS, respectively. Mechanistic explorations revealed that the replacement of the HA-Fex+ shell relative to the original passivation layer of ZVI greatly changed the SO4•- generation pathway from a heterogeneous process to a homogeneous process, resulting from the slow exposure of Fe0 (generating dissolved Fe2+) and the depolymerized HA (enhancing the Fe3+/Fe2+ cycle). Based on experimental analysis and density functional theory (DFT) calculations, the Fe3+ in HA-Fex+ could be reduced to Fe2+ by PDS, resulting in the disintegration of the HA-Fex+ shell and exposure of Fe0 core active sites. Furthermore, compared to similar catalysts synthesized with commercial HA and traditional chemicals, HA-Fex+@ZVI synthesized with multiple waste biomasses exhibited better performance. This research provides valuable insights for designing ZVI-based catalysts with excellent storage stability and ultraefficient PDS catalytic activity for AOPs.

Progress of disinfection catalysts in advanced oxidation processes, mechanisms and synergistic antibiotic degradation

Human diseases caused by pathogenic microorganisms make people pay more attention to disinfection. Meanwhile, antibiotics can cause microbial resistance and increase the difficulty of disease treatment, resulting in risk of triggering a vicious circle. Advanced oxidation process (AOPs) has been widely studied in the field of synergistic treatment of the two contaminates. This paper reviews the application of catalytic materials and their modification strategies in the context of AOPs for disinfection and antibiotic degradation. It also delves into the mechanisms of disinfection such as the pathways for microbial inactivation and the related influencing factors, which are essential for understanding the pivotal role of catalytic materials in disinfection principles by AOPs. More importantly, the exploratory research on the combined use of AOPs for disinfection and antibiotic degradation is discussed, and the potential and prospects in this field is highlighted. Finally, the limitations and challenges associated with the application of AOPs in disinfection and antibiotic degradation are summarized. It aims to provide a starting point for future research efforts to facilitate the widespread use of advanced oxidation processes in the field of public health.

Toxicological effects and underlying mechanisms of chlorination-derived metformin byproducts in Escherichia coli

Chlorination-derived byproducts of the emerging contaminant metformin, such as (3E)-3-(chloroimino)-N,N-dimethyl-3H-1,2,4-triazol-5-amine (3,3-CDTA) and N-cyano-N,N-dimethylcarbaminmidic chloride (NCDC), occur in global waters and are toxic to organisms, from bacteria to mice. However, the mechanisms underlying their toxicity remain unknown. Here, we explored the toxicological effects and potential molecular mechanisms of 3,3-CDTA and NCDC at milligram concentrations, using Escherichia coli as a model organism. Compared with metformin (>300 mg/L), 3,3-CDTA and NCDC exerted stronger toxicity to E. coli, with a 4-h half maximal inhibitory concentration of 2.97 mg/L and 75.7 mg/L, respectively. Both byproducts disrupted E. coli cellular structures and components, decreased membrane potential and adenosine triphosphate (ATP) biosynthesis, and led to excessive reactive oxidative species (ROS), as well as the ROS-scavenging enzymes superoxide dismutase and catalase. Proteomic analysis and molecular docking supported these biomarker responses in the byproduct-treated E. coli, and indicated potential damage to DNA/RNA processes, while also provided novel insights into the toxicological and detoxified-byproduct effects at the proteome level. The toxicity-related events of NCDC and 3,3-CDTA included membrane disruption, oxidative stress, and abnormal protein expression. This study is the first to examine the toxicological effects of chlorination-derived metformin byproducts in E. coli and the associated pathways involved; thereby broadening our understanding regarding the toxicity and transformation risks of metformin throughout its entire life process.

Inactivation of Escherichia Coli by mixed-valent nanoparticles in-situ generated during Fe electrocoagulation

Electrocoagulation (EC) is promising for the removal of chemical and microbial contaminants. Although the removal of pathogens from wastewater is efficient by conventional Fe-EC in the presence of dissolved oxygen (DO), the non-inactivated pathogens in the sediment still have a risk. Herein, the inactivation of Escherichia coli (E. coli) with the mixed-valent iron nanoparticles, magnetite and green rust (GR), in-situ generated from Fe-EC process in the absence of DO was investigated. The inactivation efficiency was significantly higher with magnetite (4.7 log cells) and GR (3.2 log cells) compared with FeOOH (0.7-1.7 log cells) generated at 50 mA in 10 min. The unstable in-situ generated magnetite with positive charges was prone to adsorb onto E. coli, damaging the cell membrane, inactivating the bacteria. The unstable in-situ generated GR was prone to coagulate with E. coli, delivering Fe2+ into the cell and inducing the generation of endogenous ROS, inactivating the bacteria. Fe-EC in the absence of DO was proved to be efficient for the inactivation of E. coli (4.2-4.3 log cells) in real wastewater. These findings identified the ignored inactivation effect and mechanism of E. coli with magnetite and GR generated in situ from Fe-EC process, which will provide theoretical support for real applications.

Modulation of ultrathin nanosheet structure and nitrogen defects in graphitic carbon nitride for efficient photocatalytic bacterial inactivation

The efficient generation and utilization of ROSs is a key step in determining the achievement of safe drinking water by photocatalytic bacterial inactivation technology. Although graphitic carbon nitride (g-C3N4) serves as a green and promising photocatalyst for water disinfection, insufficient bacterial capturing capacity and serious charge recombination of pristine g-C3N4 extremely restrict its bactericidal activity. Herein, we develop a facile thermal exfoliation and thermal polymerization method to prepare the nitrogen-defective ultrathin g-C3N4 nanosheets (DUCN-500). Our results showed that ultrathin nanosheet structure greatly enhanced bacterial capturing capacity of g-C3N4 to increase the utilization efficiency of ROS, which contributed to the performance of DUCN-500 greatly outperforming bulk g-C3N4. The nitrogen defects increased ROS generation (·O2- and H2O2) by approximately 4.6 times, which was attributed to negative shift of the conduction band potential and rapid separation of charge carriers. The DUCN-500 could rapidly and completely inactivate Escherichia coli and Bacillus subtilis in real sewage under simulated solar irradiation, accompanied by good anti-interference capability and stability. Additionally, bacterial morphology destruction, the loss of antioxidant enzyme activity and the leakage of protein were proven to be the main mechanisms of photocatalytic sterilization. This study offers new insight into the rational design of efficient g-C3N4-based photocatalysts for water disinfection.

Physicochemical Effects of Sulfur Precursors on Sulfidated Amorphous Zero-Valent Iron and Its Enhanced Mechanisms for Cr(VI) Removal

Amorphous zerovalent iron (AZVI) has gained considerable attention due to its remarkable reactivity, but there is limited research on sulfidated amorphous zerovalent iron (SAZVI) and the influence of different sulfur precursors on its reactivity remains unclear. In this study, SAZVI materials with an amorphous structure were synthesized using various sulfur precursors, resulting in significantly increased specific surface area and hydrophobicity compared to AZVI. The Cr(VI) removal efficiency of SAZVI-Na₂S, which exhibited the most negative free corrosion potential (-0.82 V) and strongest electron transfer ability, was up to 8.5 times higher than that of AZVI. Correlation analysis revealed that the water contact angle (r = 0.87), free corrosion potential (r = -0.92), and surface Fe(II) proportion (r = 0.98) of the SAZVI samples played crucial roles in Cr(VI) removal. Furthermore, the enhanced elimination ability of SAZVI-Na₂S was analyzed, primarily attributed to the adsorption of Cr(VI) by the FeS_x shell, followed by the rapid release of internal electrons to reduce Cr(VI) to Cr(III). This process ultimately led to the precipitation of FeCr₂O₄ and Cr₂S₃ on the surface of SAZVI-Na₂S, resulting in their removal from the water. This study provides insights into the influence of sulfur precursors on the reactivity of SAZVI and offers a new strategy for designing highly active AZVI for efficient Cr(VI) removal.

Fabricating Amorphous Zero-Valent Iron for Cr(VI) Efficient Reduction: Unveiling the Effect of Ethylenediamine on Physicochemical Properties

Amorphous zero-valent iron (AZVI) has attracted wide attention due to its high-efficiency reduction ability. However, the effect of different EDA/Fe(II) molar ratios on the physicochemical properties of the synthesized AZVI requires further investigation. Herein, series of AZVI samples were prepared by changing the molar ratio of EDA/Fe(II) to 1/1 (AZVI@1), 2/1 (AZVI@2), 3/1 (AZVI@3), and 4/1 (AZVI@4). When the EDA/Fe(II) ratio increased from 0/1 to 3/1, the Fe⁰ proportion on the AZVI surface increased from 26.0 to 35.2% and the reducing ability was enhanced. As for AZVI@4, the surface was severely oxidized to form a large amount of Fe₃O₄, and the Fe⁰ content was only 74.0%. Moreover, the removal ability of Cr(VI) was in the order AZVI@3 > AZVI@2 > AZVI@1 > AZVI@4. The isothermal titration calorimetry results revealed that the increase of the molar ratio of EDA/Fe(II) would lead to the stronger complexation of EDA with Fe(II), which resulted in the gradual decrease of the yield of AZVI@1 to AZVI@4 and the gradual deterioration of water pollution after the synthesis. Therefore, based on the evaluation of all indicators, AZVI@2 was the optimal material, not only because its yield was as high as 88.7% and the secondary water pollution level was low, but most importantly, the removal efficiency of Cr(VI) by AZVI@2 was excellent. Furthermore, the actual Cr(VI) wastewater with the concentration of 14.80 mg/L was treated with AZVI@2, and the removal rate of 97.0% was achieved after only a 30 min reaction. This work clarified the effect of different ratios of EDA/Fe(II) on the physicochemical properties of AZVI, which provided insights for guiding the reasonable synthesis of AZVI and is also conducive to investigating the reaction mechanism of AZVI in Cr(VI) remediation.

Lightning-Rod Effect on Nanowire Tips Reinforces Electroporation and Electrochemical Oxidation: An Efficient Strategy for Eliminating Intracellular Antibiotic Resistance Genes

Conventional oxidative disinfection methods are usually inefficient to eliminate intracellular antibiotic resistance genes (i-ARGs) due to competitive oxidation of cellular components of antibiotic-resistant bacteria (ARB), resulting in the ubiquitous occurrence of ARGs in drinking water systems. Herein, we developed the strategy of coupling electroporation and electrochemical oxidation on a Co₃O₄-nanowires-modified electrode to destroy the multiresistant Escherichia coli cells and promote subsequent i-ARG (bla_TEM-1 and aac(3)-II) degradation. The lightning-rod effect over nanowire tips can form finite regions with a locally enhanced electric field and highly concentrated charge density, in turn facilitating the electroporation for ARB cell damage and electrochemical reactivity for reactive chlorine/oxygen species generation. Characterization of the ARB membrane integrity and morphology revealed that electroporation-induced cell pores were further enlarged by the oxidation of reactive species, resulting in i-ARG removal at lower applied voltages and with 6-9 times lower energy consumption than the conventional electrochemical oxidation approach with a Co₃O₄-film-modified electrode. The satisfactory application and effective inhibition of horizontal gene transfer in tap water further demonstrated the great potential of our strategy in the control of the ARG dissemination risk in drinking water systems.

Synergistic nanowire-assisted electroporation and chlorination for inactivation of chlorine-resistant bacteria in drinking water systems via inducing cell pores for chlorine permeation

The widespread use of chlorination (Cl₂) in drinking water systems causes the selection of chlorine-resistant bacteria commonly with dense extracellular polymeric substance (EPS) against chlorine permeation, posing significant threat to public health. Herein, a nanowire-assisted electroporation (EP) via locally enhanced electric field was combined with Cl₂ to construct the synergistic EP/Cl₂ disinfection, with the purposes of inducing cell pores for chlorine permeation and bacterial inactivation. The synergistic effects of EP/Cl₂ were observed for inactivation of chlorine-resistant Bacillus cereus (G+, 304 μg DOC-EPS/10⁹ CFU) and Aeromonas media (G-, 35.8 μg), and chlorine-sensitive Escherichia coli (G-, 5.1 μg) that were frequent occurrence in drinking water systems. The EP/Cl₂ enabled above 6 log B. cereus inactivation (undetectable live bacteria) at 1.5 V-EP and 0.9 mg/L-Cl₂, which was much higher than the individual EP (1.11 log) and Cl₂ (1.13 log) disinfection. The cell membrane integrity, intracellular free chlorine levels, and morphology analyses revealed that the electroporation-induced pores on cell wall/membrane destructed the bound EPS barrier for chlorine permeation, and the pore sizes were further enlarged by chlorine oxidation, hence facilitating bacterial inactivation via destroying the cell structures. The excellent disinfection performance for tap water and lake water also suggested its sound application potentials.

In-depth exploration of toxicity mechanism of nanoscale zero-valent iron and its aging products toward Escherichia coli under aerobic and anaerobic conditions

The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F^- which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., Fe₃O₄, γ-Fe₂O₃, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.

Boosting the oxidative capacity of the Fe(0)/O2 system via an air-breathing cathode

The corrosion of Fe(0) in the presence of O₂ in nature can lead to the oxidation of organic compounds, but the efficiency is very limited. Herein, attempts were made to establish a galvanic system that separates the anodic Fe(0) oxidation reaction and the cathodic O₂ reduction reaction using an air-breathing cathode. Compared with the chemical Fe(0)/O₂ system, it exhibited a substantially higher capability of destroying a variety of pollutants, such as organic dyes (12 types), phenol, nitrobenzene, acetaminophen, phenol, and ethylenediaminetetraacetic acid. The degradation rate constant of a model dye (i.e., Rhodamine B) increased from 0.047 min^-1 (chemical) to 1.412 min^-1 (galvanic) under the passive air-breathing condition. The electric circuit design promoted Fe(0) dissolution to Fe(II) and triggered electron transfer that drives O₂ reduction to H₂O₂, two important species responsible for the generation of HO^• at high abundance. In addition, the galvanic Fe(0)/O₂ system produces electricity while destroying pollutants. Tests with real Ni plating wastewater further demonstrated the capability of the system to oxidize complexed organics and phosphite. This study provides a new strategy for boosting the oxidative capacity of the Fe(0)/O₂ system, which shows promise for acid wastewater treatment.

Rust triggers rapid reduction of Cr6+ by red phosphorus: The importance of electronic transfer medium of Fe3

Red phosphorus (P) is one of the metalloid materials, with five external electrons, it should be an excellent electron donor. However, the activity of red P to reduce Cr⁶⁺ is limited. Due to electrostatic repulsion, it is difficult for the electrons on the red P to transfer to the chromate anion (Cr⁶⁺). Interestingly, we found that Fe³⁺ derived from rust, waste iron or Fe³⁺ reagents can be used as the electron transport medium to solve the electron transport obstacles between red P and Cr⁶⁺. As a result, the reduction of Cr⁶⁺ by red P/rust system takes only 20 min, which is far lower than the 140 min of red P. The reduction rate of Cr⁶⁺ in the red P/rust system is about 12.3 times that of red P. The reaction mechanism is that red P is not easy to access chromate anions but can easily adsorb Fe³⁺. The adsorbed Fe³⁺ will be reduced to Fe²⁺ by red P, and the regenerated Fe²⁺ will diffuse into the solution to rapidly reduce Cr⁶⁺. Therefore, this work provides an alternative waste iron reuse pathway and also sheds light on the important role of electron medium in reduction reaction.

The high efficient Sb(III) removal by cauliflower like amorphous nanoscale zero-valent iron (A-nZVI)

In this study, cauliflower like amorphous nanoscale zero-valent iron (A-nZVI) was prepared and its performance on the removal of Sb(III) was investigated and compared with that of nZVI. The results indicated that the removal of Sb(III) by nZVI and A-nZVI followed the pseudo-second-order kinetic model and Langmuir isotherm model, but the removal of Sb(III) by A-nZVI was more stable and its removal capacity (558.2 mg/g) is much higher than that of nZVI (91.3 mg/g). Moreover, the effects of initial Sb(III) concentration, initial pH and anions such as Cl^-, NO₃^-, SO₄^2-, PO₄^3-, and AsO₄^3- were also investigated. A-nZVI showed extremely high selectivity towards Sb(III) in that 500 mg/L of AsO₄^3- and PO₄^3- shows little impact on its removal, while the removal of Sb(III) by nZVI was almost inhibited under the same condition. The combination of SEM-EDS, XPS, XRD and FTIR revealed the removal of Sb(III) by nZVI and A-nZVI were synergistic effects of oxidation and adsorption, but less Sb(III) (39.5%) was oxidized by A-nZVI. More γ-FeOOH and γ-Fe₂O₃ were formed at the surface of A-nZVI during the reaction. Both oxides have high affinity toward Sb(III), which might cause the higher removal capacity and selectivity for the removal of Sb(III) by A-nZVI. In conclusion, A-nZVI showed great potential for the remediation of Sb(III) in groundwater.

Membrane disruption boosts iron overload and endogenous oxidative stress to inactivate Escherichia coli by nanoscale zero-valent iron

The inactivation of microorganisms by nanoscale zero-valent iron (nZVI) was extensively reported, but what happens inside the cells is rarely explored. Herein, we revealed that nZVI caused the drastic increase of intracellular iron concentrations, which subsequently catalyzed the Haber-Weiss reaction to produce high levels of endogenous reactive oxygen species (ROSs) and inactivated E. coli cells by oxidative damage of DNA, evidenced by the significantly higher inactivation efficiencies of E. coli mutant strains deficient in iron uptake regulation and DNA repair than the parental strain. The intracellular iron levels, endogenous ROSs levels and the inactivation efficiencies of E. coli were positively correlated. The permeabilized cytomembrane due to the close contact between nZVI and E. coli was responsible for the iron overload. This work demonstrates experimentally for the first time that nZVI causes iron overload and endogenous oxidative stress to inactivate E. coli, thus deepening our knowledge of the nZVI antimicrobial mechanism.

Synergistic effect of sulfidated nanoscale zerovalent iron in donor and recipient bacterial inactivation and gene conjugative transfer inhibition

Antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) are widespread in urban wastewater treatment plants (UWTPs). In this research, a horizontal transfer model of recipient (Pseudomonas. HLS-6) and donor (Escherichia coli DH5α carries RP4 plasmid) was constructed to explore the effect of sulfidated nanoscale zerovalent iron (S-nZVI) on the efficiency of plasmid-mediated horizontal transfer. When the S/Fe was 0.1, the inactivation efficiency of 1120 mg/L S-nZVI on the donor and recipient bacteria were 2.36 ± 0.03 log and 3.50 ± 0.17 log after 30 min, respectively (initial ARB concentration ≈ 5 ×10⁷ CFU/mL). Effects of treatment time, S/Fe molar ratio, S-nZVI dosage and initial bacterial concentration were systemically studied. S-nZVI treatment could increase the extracellular alkaline phosphatase and malondialdehyde content of the ARB, cause oxidative stress in the bacteria, destroy the cell structure and damage the intracellular DNA. This study provided evidence and insights into possible underlying mechanisms for reducing conjugative transfer, such as hindering cell membrane repair, inducing the overproduction of reactive oxygen species, inhibiting the SOS response, reducing the expression of ARGs and related transfer genes. S-nZVI could inhibit the gene conjugative transfer while inactivating the ARB. The findings provided an alternative method for controlling antibiotic resistance.

Transcriptome profiles of genes related to growth and virulence potential in Vibrio alginolyticus treated with modified clay

Vibrio alginolyticus is a globally distributed opportunistic pathogen that causes different degrees of disease in various marine organisms, such as fish, shrimp and shellfish. At present, vibriosis caused by V. alginolyticus has a wide epidemic range and causes frequent outbreaks, resulting in substantial losses in aquaculture. According to previous studies, modified clay (MC) could effectively flocculate and reduce the density of Vibrio in water, but it is still unknown whether MC inhibits growth and how it affects virulence in bottom flocs. Here, we studied the response mechanism of V. alginolyticus in flocs treated with MC at the transcriptome level and verified the transcriptomic data combined with relevant physiological experiments and reverse transcription quantitative real-time PCR (RT-qPCR) for the first time. It was found that the morphology of Vibrio in the MC flocs changed, the membrane function was damaged, the antioxidant system was activated, and the material and energy metabolism also changed. In addition, MC could inhibit the expression of virulence factors of V. alginolyticus; for example, flagella, pilus, siderophores, quorum sensing, and other related genes were significantly downregulated. In general, MC effectively inhibited the growth of Vibrio and reduced its virulence potential in flocs, which could provide theoretical support for a new model of healthy aquaculture.

Synthesis, Characterization, and Photocatalytic Investigation of CuFe2O4 for the Degradation of Dyes under Visible Light

The CuFe2O4 photocatalysts were synthesized by the solution combustion synthesis method, followed by heat treatment at a temperature range of 400 to 1100 °C. Later, they were characterized for application in the photodegradation of synthetic dyes under visible radiation. The X-ray diffraction results showed the presence of cubic and tetragonal phases of CuFe2O4 and secondary phases of Fe2O3 and CuO, at low temperatures. The infrared spectrum profile confirms the formation of the phases pointed out in the XRD. For most specimens, the scanning electron microscopy examination revealed a morphology similar to porous flakes and a quasi-spherical shape. On the other hand, samples heat-treated at 1100 °C displayed a plate-like morphology. The specimens’ band gap ranged from 1.49 to 1.58 eV, indicating that the material is a semiconductor. Regarding the photocatalytic efficiency, the 400 °C heat-treated samples showed better activity when the visible irradiation was used over the green malachite and rhodamine B dyes. The solution degradation rates on the first and former dyes were 56.60% and 84.30%, respectively.

Vacancy-rich BiO2-x as a highly-efficient persulfate activator under near infrared irradiation for bacterial inactivation and mechanism study

This study, for the first time, developed a novel defective BiO_2-x based collaborating system, where the near-infrared light (NIR) irradiation (λ > 700 nm) initiated persulfate activation and photocatalytic bacterial inactivation simultaneously. Vacancy-rich BiO_2-x nanoplates possessed impressive NIR absorption and firstly realized persulfate activation under NIR irradiation. In this collaborating system, on one hand, the persulfate can be transformed into sulfate radicals through light/heat activation mode directly, which would be enhanced by the presence of vacancy-rich BiO_2-x owing to its outstanding light and heat absorption ability. On the other hand, the photogenerated electrons can further efficiently react with persulfate and form sufficient reactive sulfate radicals. The sulfate radicals, synergizing with other reactive species (O₂^-, h⁺, etc.), achieved a 7-log Escherichia coli inactivation within 40 min. The systematic investigation of inactivation mechanism revealed that the reactive species caused the dysfunction of cellular respiration, ATP synthesis and bacterial membrane, followed by the severely oxidative damage to the antioxidative SOD and CAT enzymes and the generation of carbonylated protein. The final leakage of DNA and RNA implied the lethal damage to the bacteria cells. This work provided a new insight into the persulfate associated NIR driven remediation technology of controlling microbial contaminants.

Performances and mechanisms of microbial nitrate removal coupling sediment-based biochar and nanoscale zero-valent iron

Immobilized microorganism technology has attracted increasing attention for high concentration of microbes, low cell loss and high resistance to impact of environment. The microbial reduction of nitrate in the presence of sediment-based biochar (SBC) and nanoscale zero-valent iron (nZVI) was investigated in four different free systems. NZVI-SBC/bacteria system realized the best nitrate removal of 97.61% within 3 days through the synergistic effect of SBC and nZVI on denitrifying bacteria. Accumulation of nitrite and ammonium in nZVI-SBC/bacteria system also decreased. High-throughput sequencing results showed that the proportion of denitrifying bacteria in microbial community structure increased after adding nZVI-SBC. The performance of nitrate removal was then studied through PVA/SA-immobilization. Immobilized active pellets performed better nitrate removal (98.89%) and stronger tolerance under different conditions than the free bacterial cells. Overall, this study provided a promising approach by utilizing SBC and nZVI for the bio-remediation of nitrate-contaminated water in practical application.

Influence of several crucial groundwater components on the toxicity of nanoscale zero-valent iron towards Escherichia coli under aerobic and anaerobic conditions

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.

Iron amendments minimize the first-flush release of pathogens from stormwater biofilters

First flush or the first pore volume of effluent eluted from biofilters at the start of rainfall contributes to most pollution downstream because it typically contains a high concentration of bacterial pathogens. Thus, it is critical to evaluate designs that could minimize the release of bacteria during a period of high risk. In this study, we test the hypothesis of whether an addition of iron-based media to biofilter could limit the leaching of Escherichia coli (E. coli), a pathogen indicator, during the first flush. We applied E. coli-contaminated stormwater intermittently in columns packed with a mixture of sand and compost (70:30 by volume, respectively) and iron filings at three concentrations: 0% (control), 3%, and 10% by weight. Columns packed with a mixture of sand and iron (3% or 10%) without compost were used to examine the maximum capacity of iron to remove E. coli. In columns with iron, particularly 10% by weight, the leaching of E. coli during the first flush was 32% lower than the leaching from compost columns, indicating that the addition of iron amendments could decrease first-flush leaching of E. coli. We attribute this result to the ability of iron to increase adsorption and decrease growth during antecedent drying periods. Although the addition of iron filings increased E. coli removal, the presence of compost decreased the adsorption capacity: exposure of 1 g of iron filings to 1 mg of DOC reduces E. coli removal by 8%. The result was attributed to the alteration of the surface charge of iron and blocking of adsorption sites shared by E. coli and DOC. Collectively, these results indicate that the addition of sufficient amounts of iron media could decrease pathogen leaching in the first flush effluent and increase the overall biofilter performance and protect downstream water quality.

Bacteriostatic impact of nanoscale zero-valent iron against pathogenic bacteria in the municipal wastewater

Nanoscale zero-valent iron particles were investigated as an antibacterial agent against two Gram-positive bacteria; Staphylococcus aureus NRRL B-313 (S. aureus), Bacillus subtilus NRC (B. subtilus), and two Gram-negative bacteria; Escherichia coli NRC B-3703 (E. coli), Pseudomonas aeruginosa NRC B-32 (Ps. aeruginosa). The characterization of synthesized nZVI particles was obtained by XRD, SEM, EDX, and TG analyses. The results demonstrated that the nZVI particles have a spherical shape, mean crystalline size of 44.43 nm, and exhibited a good chemical and thermal stability performance under different physical conditions. The bacterial suspensions were subjected to the treatment using nZVI particle suspensions with a concentration of 10 mg/mL. The minimum inhibitory concentration of nZVI particles was determined using the well diffusion assay method and found to be 15, 10, 10, and 5 mg for the following four strains; S. aureus, B. subtilus, E. coli, and Ps. aeruginosa, respectively. The biological treatment results of municipal wastewater using nZVI particles revealed that the counts of total bacteria, total coliform, fecal coliform, S. aureus, fecal Streptococcus, and E. coli were decreased to 44.29%, 51.76%, 90.95%, 46.67%, 33.33%, and 93.89%, respectively, while the Ps. aeruginosa not detected in the wastewater sample. The enhanced inactivation performance of nZVI nanoparticles was mainly attributed to the reactive oxygen species (ROS) production, releasing of iron corrosion products like Fe²⁺/Fe³⁺ ions, and direct friction of nZVI particles with bacterial cells membranes. In addition, the nZVI particles presented a striking disinfection behavior in comparison with other widespread disinfection technologies such as chlorination. Accordingly, the obtained results introduce the nZVI particles as a promising disinfection technology.

Heterogeneous Fenton catalysts: A review of recent advances

Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.

Hydroxylamine driven advanced oxidation processes for water treatment: A review

Hydroxylamine (HA) driven advanced oxidation processes (HAOPs) for water treatment have attracted extensive attention due to the acceleration of reactive intermediates generation and the improvement on the elimination effectiveness of target contaminants. In this review, HAOPs were categorized into three parts: (1) direct reaction of HA with oxidants (e.g., hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), ozone (O₃), ferrate (Fe(VI)), periodate (IO₄^-)); (2) HA driven homogeneous Fenton/Fenton-like system (Fe(II)/peroxide/HA system, Cu(II)/O₂/HA system, Cu(II)/peroxide/HA system, Ce(IV)/H₂O₂/HA system); (3) HA driven heterogeneous Fe/Cu-Fenton/Fenton-like system (iron-bearing material/peroxide/HA system, copper-bearing material/peroxide/HA system, bimetallic composite/peroxide/HA system). Degradation efficiency of the target pollutant, reactive intermediates, and effective pH range of various HAOPs were summarized. Further, corresponding reaction mechanism was elaborated. For the direct reaction of HA with oxidants, improvement of pollutants degradation was achieved through the generation of secondary reactive intermediates which had higher reactivity compared with the parent oxidant. For HA driven homogeneous and heterogeneous Fe/Cu-Fenton/Fenton-like system, improvement of pollutants degradation was achieved mainly via the acceleration of redox cycle of Fe(III)/Fe(II) or Cu(II)/Cu(I) and subsequent generation of reactive intermediates, which avoided the drawbacks of classical Fenton/Fenton-like system. In addition, HA driven homogeneous Fe/Cu-Fenton/Fenton-like system with heterogeneous counterpart were compared. Further, formation of oxidation products from HA in various HAOPs was summarized. Finally, the challenges and prospects in this field were discussed.

Inactivation of sulfonamide antibiotic resistant bacteria and control of intracellular antibiotic resistance transmission risk by sulfide-modified nanoscale zero-valent iron

The inactivation of a gram-negative sulfonamide antibiotic resistant bacteria (ARB) HLS.6 and removal of intracellular antibiotic resistance gene (ARG, sul1) and class I integrase gene (intI1) by nanoscale zero-valent iron (nZVI) and sulfide-modified nZVI (S-nZVI) with different S/Fe molar ratios were investigated in this study. The S-nZVI with high sulfur content (S/Fe = 0.05, 0.1, 0.2) was superior to nZVI and the treatment effect was best when S/Fe was 0.1. The ARB (2 × 10⁷ CFU/mL) could be completely inactivated by 1.12 g/L of S-nZVI (S/Fe = 0.1) within 15 min, and the removal rates of intracellular sul1 and intI1 reached up to 4.39 log and 4.67 log at 60 min, respectively. Quenching experiments and flow cytometry proved that reactive oxygen species and adsorption were involved in the ARB inactivation and target genes removal. Bacterial death and live staining experiments and transmission electron microscopy showed that the ARB cell structure and intracellular DNA were severely damaged after S-nZVI treatment. This study provided a potential alternative method for controlling the antibiotic resistance in aquatic environment.

Production of Reactive Oxygen Species by the Reaction of Periodate and Hydroxylamine for Rapid Removal of Organic Pollutants and Waterborne Bacteria

Periodate (PI, IO₄^-) can be activated by hydroxylamine (HA), resulting in the rapid removal of organic pollutants within seconds. While the previous studies on PI-based advanced oxidation processes (AOPs) have proposed iodate radical (^•IO₃) as the major reactive species, no evidence of ^•IO₃ production was found in the present PI/HA system. Reactive oxygen species (ROS) including ^•OH, HO₂^•, and ¹O₂ are proposed to be the main oxidants of the PI/HA system, which is supported by various tests employing the scavengers, chemical probes, and spin-trapping electron paramagnetic resonance (EPR) technique. To minimize the risk of toxic iodinated byproduct formation caused by reactive iodine species such as HOI and I₂, the molar ratio of HA/PI was optimized at 0.6 to achieve the stoichiometric conversion of IO₄^- to iodate (IO₃^-), a preferred nontoxic sink of iodine species. The PI/HA system also efficiently inactivated both Gram-positive and -negative bacteria with producing ¹O₂ as the dominant disinfectant. The mechanism of ROS production was also investigated and is discussed in detail. This work offers a simple and highly efficient option for PI activation and ROS production which might find useful applications where urgent and rapid removal of toxic pollutants is needed.

Mechanisms of Enhanced Antibacterial Activity by Reduced Chitosan-Intercalated Nontronite

Previous studies have documented the antibacterial activity of certain iron-containing clays. However, the repulsion between negatively charged bacteria and the clay surface makes this process inefficient. The objective of this study is to improve the bactericidal efficiency of clays by reversing their surface charge from negative to positive. To achieve this objective, positively charged chitosan, a nontoxic and biodegradable polymer, was intercalated into nontronite NAu-2. Chitosan-intercalated NAu-2 (C-NAu-2) was chemically reduced to obtain reduced C-NAu-2 (rC-NAu-2). Relative to reduced nontronite (rNAu-2), the antibacterial activity of rC-NAu-2 is higher and more persistent over a pH range of 6-8. The close spatial association between positively charged rC-NAu-2 and negatively charged bacteria increases the chances of cell membrane attack by extracellular ROS, the influx of soluble Fe²⁺ into the bacterial cell, and the yield of intracellular ROS. All these factors contribute to the enhanced antibacterial activity of rC-NAu-2. In contrast to rNAu-2 treated E. coli cells, where membrane damage and intracellular ROS/Fe accumulation are restricted to the polar regions, the close bacteria-clay association in rC-NAu-2 results in nonselective membrane damage and more uniform intracellular ROS/Fe distribution across whole bacterial cells. These results advance the antibacterial model by highlighting the importance of bacteria-clay interactions to the antibacterial activity of Fe-bearing clays.

Photocatalytic Bacterial Inactivation by a Rape Pollen-MoS2 Biohybrid Catalyst: Synergetic Effects and Inactivation Mechanisms

A novel and efficient 3D biohybrid photocatalyst, defective MoS₂ nanosheets encapsulated carbonized rape pollen, was fabricated and applied to water disinfection. The rape pollen-MoS₂ (PM) biohybrid showed excellent dispersibility, high stability, and efficient charge-carrier separation and migration ability, resulting in the highly enhanced photocatalytic inactivation performance toward various waterborne bacteria under different light sources. The inactivation mechanisms were systematically investigated. Reactive species (RSs), including electrons, holes, and reactive oxygen species (•O₂^- and •OH), played major roles in inactivating bacteria. The antioxidant system of bacteria exhibited a self-protection capacity by eliminating the photogenerated RSs from PM biohybrid at the early stage of inactivation. With the accumulation of RSs, the cell membrane and membrane-associated functions were destroyed, as suggested by the collapse of cell envelope and subsequent loss of cell respiration and ATP synthesis capacity. The microscopic images further confirmed the destruction of the bacterial membrane. After losing the membrane barrier, the oxidation of cytoplasmic proteins and lipids caused by invaded RSs occurred readily. Finally, the leakage of DNA and RNA announced the irreversible death of bacteria. These results indicated that the bacterial inactivation began with the membrane rupture, followed by the oxidation and leakage of intracellular substances. This work not only provided a new insight into the combination of semiconductors with earth-abundant biomaterials for fabricating high-performance photocatalysts, but also revealed the underlying mechanisms of photocatalytic bacterial inactivation in depth.

Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal

This study characterizes the decrease of the hydraulic conductivity (permeability loss) of a metallic iron-based household water filter (Fe0 filter) for a duration of 12 months. A commercial steel wool (SW) is used as Fe0 source. The Fe0 unit containing 300 g of SW was sandwiched between two conventional biological sand filters (BSFs). The working solution was slightly turbid natural well water polluted with pathogens (total coliform = 1950 UFC mL−1) and contaminated with nitrate ([NO3−] = 24.0 mg L−1). The system was monitored twice per month for pH value, removal of nitrate, coliforms, and turbidity, the iron concentration, as well as the permeability loss. Results revealed a quantitative removal of coliform (>99%), nitrate (>99%) and turbidity (>96%). The whole column effluent depicted drinking water quality. The permeability loss after one year of operation was about 40%, and the filter was still producing 200 L of drinking water per day at a flow velocity of 12.5 L h−1. A progressive increase of the effluent pH value was also recorded from about 5.0 (influent) to 8.4 at the end of the experiment. The effluent iron concentration was constantly lower than 0.2 mg L−1, which is within the drinking-water quality standards. This study presents an affordable design that can be one-to-one translated into the real world to accelerate the achievement of the UN Sustainable Development Goals for safe drinking water.

Highly Efficient Utilization of Nano-Fe(0) Embedded in Mesoporous Carbon for Activation of Peroxydisulfate

Nanoscale zerovalent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. However, the aggregation and oxidation of nZVI brings much difficulty in practical application of environmental remediation. In this study, we reported a composite nano-Fe(0)/mesoporous carbon by a chelation-assisted coassembly and carbothermal reduction strategy. Nano-Fe(0) particles with surface iron oxide (Fe₂O₃·FeO) were wrapped with graphitic layers which were uniformly dispersed in mesoporous carbon frameworks. The unique structure made the nano-Fe(0) particles stable in air for more than 20 days. It was used as a peroxydisulfate (PDS) activator for the oxidation treatment of 2,4,6-trichlorophenol (TCP). The TOF value of MCFe for TCP degradation is nearly 3 times higher than those of FeSO₄ and Fe₂O₃·FeO and nearly 2 times than that of commercial nZVI. The reactive oxygen species (ROS) including •SO₄^-, HO•, and •O₂^-, ¹O₂ are efficiently generated by PDS activation with MCFe. The PDS activation process by nano-Fe(0) particles was intrinsically induced by the ferrous ions (Fe(II)) continuously generated at the solid/aqueous interface. Namely, the nano-Fe(0) particles were highly efficiently utilized in sulfate radical-based advanced oxidation processes (SR-AOP). The porous structure also assists the absorption and transfer of TCP during the degradation process.