Zero-valent iron (Fe0) demonstrates significant potential for Cr(VI) contaminated groundwater remediation; however, its reactivity faces inherent limitations from surface passivation. Lattice engineering of Fe0 is among the most promising approaches, yet the impact of such lattice alterations on oxide phase transitions and associated microelectronic properties remains elusive. This study introduces an innovative mechanochemical activation strategy that synergistically modulates Fe lattice strain and reconstructs oxide shell speciation through controlled wet ball milling. Upon investigating the removal of Cr(VI), we observed an intriguing bimodal trend in removal efficiency, with maximum capacities of 82.38 mg·g-1 (up to 4.6-fold higher than unmodified Fe0) and 53.80 mg·g-1 achieved by two distinct Fe0-BM (Fe0-BM-1 and Fe0-BM-12). Lattice diffraction, Mössbauer spectroscopy, and depth profiling revealed that initial mechanical fracturing generated surface defects and caused partial exfoliation of the Fe0-BM-1 oxide layer. This was followed by a mechanochemical reaction that reconstructed the oxide lattice, forming a Fe3O4-dominated phase in Fe0-BM-12. The fracture of the oxide shell exposed the reactive Fe° core, while the generation of a semiconducting Fe3O4 enhanced conductivity. Density functional theory calculations showed that Fe0-BM exhibited a lower energy barrier and a more stable adsorption configuration, facilitating outward electron transfer from the core to the shell and Cr(VI). This study presents a green approach for designing Fe0-based materials via structure-performance regulation, advancing sustainable Cr(VI)-contaminated groundwater remediation.

This study investigated the removal of organic matter and nitrogen, as well as the emissions of CO2, CH4, and N2O in wastewater subsurface infiltration systems (WSISs) that were amended with or without biochar-biosolids and operated with or without intermittent aeration. Additionally, the bacterial abundance, functional genes, and microbial communities at different depths were analyzed. The results showed the aerobic environment was established above 0.45 m, while the anaerobic environment below 0.85 m remained unaffected by intermittent aeration. Intermittent aeration led to remarkable enhancements in the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N), accompanied by elevated abundances of bacterial 16S rRNA, amoA, and nxrA at a depth of 0.45 m. Conversely, the abundance of mcrA decreased at depths of 0.85 m and 1.25 m. The WSIS, with the addition of biochar-biosolids and intermittent aeration, achieved the highest removal efficiencies for COD (95.9 ± 0.3%), NH4+-N (93.7 ± 0.3%), total nitrogen (TN) (86.3 ± 0.5%), as well as the lowest emission rates for CH4 (2.82 ± 0.53 mg/d) and N2O (0.54 ± 0.08 mg/d). Moreover, it enhanced the microbial Alpha diversity, reshaped the microbial co-occurrence network structure and promoted the relative abundances of microorganisms involved in organic matter and nitrogen removal processes. The combination of biochar-biosolids addition and intermittent aeration is a reliable approach for a WSIS to improve organics removal, nitrogen removal, and reduce CH4 and N2O emissions.

To enhance the electron utilization capability and efficiency of iron-based materials in heterogeneous Fenton reaction of Fe3S4, WS2 was employed in this study to utilize interface electron transfer process to promote the Fenton oxidation for benzene, a typical contaminant in groundwater at industrially contaminated sites. The benzene removal rate in the WS2/Fe3S4/H2O2 system reached 79.79 % after a 120-minute reaction under the following experimental conditions: 0.15 g/L Fe3S4, 0.4 g/L WS2, 2 mmol/L H2O2, 20 mg/L benzene, and an initial pH of 7.0. Based on the systematic investigations using the XRD, SEM, EPR, XPS, electrochemical test and DFT calculation, it was observed that the incorporation of WS2 expedited the reductive regeneration of dissolved Fe2 + from Fe3S4 by donating sufficient electrons, achieving the enhanced generation of free center dot OH. Furthermore, a mechanism involving an electron donor-shuttle was identified, with W and S atoms serving as the electron donor and shuttle, respectively. The presence of S atoms in Fe3S4 significantly accelerated the electron transfer between W and Fe atoms, thereby promoting the regeneration of surface-bounded Fe2+ and the production of abundant surface-bounded center dot OH. The proposed WS2/Fe3S4/H2O2 system provided a feasible strategy for enhancing electron regeneration and utilization during remediation of organic contaminants in groundwater by iron-based Fenton- like systems.

To deeply elucidate the intrinsic nature that impact Fenton activity of iron sulfide-based catalysts, iron sulfides with different electronic configurations and crystal structures (FeS, FeS2, Fe3S4, Fe7S8) were applied to activate H2O2 for degrading benzene. The benzene removal reaction exhibited two-stage pattern, where FeS, FeS2 and Fe3S4 were classified as one type of material with Fe7S8 as another type. In the first stage, the unstable crystal structure of Fe3S4 promoted the enhanced iron dissolution and accelerated redox cycle of dissolved iron, thus achieving the highest benzene removal rate (53%). In the second stage, the higher work function of Fe7S8 strengthened electric field from sufficient Fe3+, which in turn promoted iron cycle on Fe7S8 surface. Additionally, the lower energy difference between S p-band and Fe d-band center facilitated the internal iron cycle on Fe7S8. Thus, Fe7S8/H2O2 system obtained the highest benzene removal rate (86.6 %) in the second stage. This work not only provided the deep understanding into intrinsic causes of iron sulfides catalytic performance, but also offered valuable guidance to develop iron cycle-optimized heterogeneous iron-based materials for remediating organic contaminated groundwater.

Sulfidated zero-valent iron (ZVI) and biochar-supported ZVI have received increasing attention for their potential to dechlorinate trichloroethylene. However, minimal data are available regarding the combined effect of sulfur and biochar ZVI on trichloroethylene byproducts. The primary aim of the current study is to determine whether sulfur- and biochar-modified ZVI (ZVI-BC-S) enhances the removal of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) from groundwater. Results show that biochar and sulfur facilitated the milling of ZVI-BC-S into micro- and nanoscale particles and increased FeS formation. Moreover, the rates of cDCE and VC removal by ZVI-S increased by 30.1% and 30.2%, respectively, compared to those obtained with ZVI, owing to enhanced dechlorination via β-elimination by sulfur. Meanwhile, treatment with ZVI-BC-S harnessed the benefits of biochar and sulfur to enhance the cDCE and VC removal rates by 62.0% and 67.7%, respectively. Mechanistically, biochar enhanced the corrosion of ZVI-S to increase FeS production and enhance the electron transfer, β-elimination, and hydrogenolysis involved in cDCE and VC dechlorination. The effectiveness of ZVI-BC-S was confirmed in a field demonstration, during which cDCE and VC concentrations significantly decreased within 10 days following injection. The findings of this study can help inform the rational design of ZVI for in-situ remediation of chlorinated hydrocarbons in groundwater.

Polycyclic aromatic hydrocarbons are persistent organic pollutants that are ubiquitous in the soil and groundwater.Having the simplest structure, naphthalene is one of polycyclic aromatic hydrocarbon, which is characterized by strong mobility and can accumulate in soil and groundwater through a variety of pathways. It has become the most important contaminant of concern in historically abandoned coking and chemical contaminated sites. As advanced oxidation technologies（AOTs） are efficient, safe and economical, their utilization for the treatment of naphthalene-contaminated soil and groundwater has attracted significant attention. This article reviews the reaction mechanism of AOTs such as Fenton and Fenton-like, ozone and persulfate oxidation, focusing on the progresses obtained on the application of activation technologies by homogeneous and heterogeneous activators such as divalent iron, zero-valent iron, micro-and nano-scale zero-valent iron, iron minerals, iron chelates etc., in the remediation of naphthalene-contaminated soil and groundwater, introduces the research statuses on combined remediation using multiple AOTs and synergistic remediation between AOTs and biodegradation technologies, and the existing problems and future prospects on AOTs are also highlighted.

The simultaneous removal of hexavalent chromium (Cr(VI)) and Trichloroethylene (TCE) is facing great challenges, and the influences of the biochar on their removal by nanoscale zero-valent iron (nZVI) are poorly understood and seldom addressed in the literature. The rice straw pyrolysis at 700 °C (RS700) and their supported nZVI composites were investigated on the removal of Cr(VI) and TCE by batch experiments. The surface area and chromium bonding state of biochar supported nZVI with and without Cr(VI)-TCE loading were analyzed by Brunauer-Emmett-Teller analysis and X-ray photoelectron spectroscopy. In single pollutants system, the highest removal amounts of Cr(VI) and TCE were observed in RS700-HF-nZVI (76.36 mg/g) and RS700-HF (32.32 mg/g), respectively. The Cr(VI) removal was attributed to the reduction by Fe(II) with the adsorption by biochar primarily controlling the TCE removal. The mutual inhibition was revealed in simultaneous removal of Cr(VI) and TCE, in which the reduction of Cr(VI) was decreased due to the adsorption of Fe(II) by biochar, while the TCE adsorption was primarily inhibited owing to the blockage of surface pores of biochar supported nZVI by chromium‑iron oxides. Therefore, biochar supported nZVI could be potentially used for the combined contaminated groundwater remediation, but the mutual inhibition should be evaluated.

Iron sulfides have attracted growing concern in heterogeneous Fenton reaction. However, the structure of iron sulfides is different from that of iron oxides and how the structures affect the activation property of hydrogen peroxide (H2O2) remains unclear. This study investigated benzene removal through the activation of H2O2 by the synthesized magnetite (Fe3O4) and greigite (Fe3S4). The structures of Fe3O4 and Fe3S4 were characterized by XRD and EPR, the electron transfer properties of Fe3O4 and Fe3S4 were analyzed by electrochemical workstation, XPS and DFT. It is revealed that the effective benzene removal rate of 88.86% in the Fe3S4/H2O2 was achieved, which compared to 15.58% obtainable from the Fe3O4/H2O2, with the apparent rate constant in the Fe3S4/H2O2 being approximately 65 times over that in the Fe3O4/H2O2. The better H2O2 activation by Fe3S4 was attributed to the significant roles of S (-II) and S vacancies in regulating the dissolution of ferrous iron ions, thus generating abundant free •OH radical. In addition, surface bounded ferrous iron of Fe3S4 could transfer more electrons to H2O2 and O2 to generate more surface bounded •OH and •O2−. This study revealed the combined action of dissolved and surface bounded ferrous iron of greigite on H2O2 activation, and provides an efficient heterogeneous H2O2 activator for the remediation of organic contaminants in groundwater.

The electron storage quantities and electron transfer rate of the reductants are the most critical factors to determine the contaminants degradation in aqueous solution. Zero-valent iron (Fe0) has been considered as a potential reducing agent due to its considerable amount of electron storage, and a variety of modification methods have been explored to strengthen the low electron transfer rate of the Fe0 in the past 30 years. In this study, Fe0-Fe3O4-BM was prepared by ball milling with ethylene glycol as a liquid grinding aid for the reduction of Cr(VI). In the batch experiment with pH = 3.0, C0= 30 mg L-1 and solid-liquid ratio = 1 g L-1, the Cr(VI) removal rate nearly 100 % for Fe0-Fe3O4-BM was reached, significantly higher than 38.9 % and 5.3 % respectively for Fe0 and Fe3O4, with the Cr(VI) removal capacity exceeding its theoretial sum from individual milled Fe0 or Fe3O4. The removal process conformed with pseudo-second-order kinetic, implying that electron transport was the principle limiting step. Semiconductor properties of Fe3O4 played a decisive role in the iron composites, reflecting the greater electron transfer rate and lower resistance of Fe0-Fe3O4-BM. This study revealed that the synthesised Fe0-Fe3O4-BM composite showed a splendid synergy between the abundant electron storage of Fe0 and the fast electron transfer of Fe3O4, with micro-nano structure prepared by wet ball milling providing a highly effective reagent with a large-scale production potential for in-situ injection based groundwater remediation.

为探讨不同铁源对铁碳复合材料结构及其吸附-氧化萘污染的影响,分别以硫酸亚铁、氯化铁、硝酸铁、纳米零价铁和纳米四氧化三铁为铁源,葡萄糖为碳源,采用水热-碳热法合成了铁碳复合材料.采用比表面积测试、红外光谱仪、X射线衍射仪和电化学工作站分别测定材料的比表面积和孔结构、表面官能团、晶体结构和氧化还原能力,同时通过动力学实验研究不同复合材料吸附和活化过氧化氢氧化萘的效果.结果表明:Fe2SO4@C、FeCl3@C和Fe(NO3)3@C因较小的孔体积或较高的表面含氧官能团含量,而对萘的吸附去除率较低,且无法对萘的氧化起到活化作用.而nFe0@C和nFe3O4@C的孔体积较大,且生成结构态亚铁[Fe(Ⅱ)]和碳化三铁(Fe3C)活性物质,可通过吸附和活化过氧化氢氧化去除萘,其中nFe3O4@C对萘的去除效果最好,去除率达到63.7％.研究表明,使用固态铁源制备的铁碳复合材料,具有较低的极性、较大的孔体积以及结晶较好的铁活性物质,在萘污染水体修复中具有较大应用潜力.

Synthesized attapulgite-supported nanoscale zero-valent iron (AT-nZVI) composite/persulfate (PS) systems were utilized to simultaneously remove hexavalent chromium (Cr(VI)) and trichloroethylene (TCE) from aqueous solutions. The structures of AT-nZVI before and after the reaction with Cr(VI)-TCE were characterized by TEM-EDS-Mapping, HR-TEM and HR-XPS with ion sputtering. The effects of initial Cr(VI), TCE and PS concentrations, and PS addition time intervals on Cr(VI)-TCE removal efficiencies were evaluated. Experimental results revealed that the AT-nZVI composites with 1 mM PS can effectively and simultaneously remove Cr(VI) and TCE with the removal efficiencies of Cr(VI) and TCE reaching 90.02% and 90.40% respectively. It is thought that PS promoted TCE oxidation and the reduction of Cr(VI), which was predominately controlled by Fe(II). TCE was mainly degraded by free radical oxidation resulting from the PS activation of AT-nZVI. The enhanced Cr(VI) removal was attributed to the exposed areas and available active sites of nZVI, and Fe(II) in the solution increased by PS-mediated processes of rapid corrosion and dissolution of nZVI. The dual roles of AT-nZVI as a activator for PS activation and reductant for Cr(VI) reduction in Cr(VI)-TCE removal were identified. This implies that AT-nZVI/PS can be utilized as potential remediation reagents for simultaneous removal of heavy metal and chlorinated solvents in groundwater frequently encountered in contaminated sites.

The attempt to decorate carbon nanotubes with organic molecules to form new functional materials has attracted broad attention in the scientific community. Here, we report the covalent functionalization of multiwalled carbon nanotubes (MWCNTs) with pyrene via Cu(I)-catalysed azide/alkyne click (CuAAC) reactions under mild conditions to afford the nanocomposites of pyrene-MWCNTs. Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectroscopy (UV-Vis), and fluorescence spectroscopy were used to characterize the nanocomposites of pyrene clicked MWCNTs. Experimental results indicate that the CuAAC reaction occurs in an efficient manner and the spacer linking MWCNTs and the photoactive molecule is well defined. In contrast to the noncovalent functionalization of π-π stacking, the nanocomposites of pyrene clicked MWCNTs show relatively strong fluorescence and have potential applicability in photoluminescent devices as a highly sensitive and selective fluorescence "turn-off" sensor for Fe(3+).

A simple and versatile method for the introduction of electrochemical moieties onto the surface of Fe3O4 nanoparticles has been developed based on UV-induced thiol-ene click chemistry. Thiol-terminated Fe3O4 nanoparticles were synthesized and further reacted with vinylferrocence under 365nm UV. The functionalized magnetic nanoparticles were characterized using a powder X-ray diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscope (FTIR), and vibrating sample magnetometer (VSM). The resulting nanocomposites possess of magnetism and electrochemical activity. Based on the superparamagnetism of Fe3O4 nanoparticles and the electrocatalytic activity of ferrocene, a recyclable, magneto-controlled bioelectrocatalytic system for glucose oxidation is developed. The switching of the biocatalytic activity and recyclable usage of the ferrocene functionalized nanoparticles by means of the external magnet could provide a simple, green and convenient strategy for bioelectrosensing.

An electrochemical platform for acetylcholinesterase (AChE) activity assay and its inhibitors screening is developed based on the Michael addition reaction of thiocholine, the hydrolysis product of acetylthiocholine (AsCh) in the presence of AChE, with the electrogenerated o-quinone of catechol-terminated SAMs on a gold electrode. For understanding and confirming the mechanism of the reaction, the electrochemical behaviors of Michael addition reaction of two model compounds, cysteine (CYS) and glutathione (GSH), towards the catechol-terminated SAMs have been studied. The enzyme kinetics and the inhibition effects of three types of AChE inhibitors, which are tacrine, carbofuran and parathion-methyl, have been investigated using an amperometric method. Among these three inhibitors, tacrine exhibits the strongest inhibiting effect, which is reinforced by the resulting data of kinetic studies on each inhibitor's influence upon the enzyme activity.

A simple and versatile approach for covalent immobilization of redox protein on solid surface via self-assembled technique and click chemistry is reported. The alkynyl-terminated monolayers are obtained by self-assembled technique, then, azido-horseradish peroxidase (azido-HRP) was covalent immobilized onto the formed monolayers by click reaction. The modified process is characterized by reflection absorption infrared spectroscopy (RAIR), surface-enhanced Raman scattering spectroscopy (SERS) and electrochemical methods. All the experimental results suggest that HRP is immobilized onto the electrode surface successfully without denaturation. Furthermore, the immobilized HRP shows electrocatalytic reduction for H2O2, and the linear range is from 5.0 to 700 μM. The heterogeneous electron transfer rate constant ks is 1.11 s−1 and the apparent Michaelis–Menten constant is calculated to be 0.196 mM.

In this paper, a simple two-step approach for redox protein immobilization was introduced. Firstly, alkynyl-terminated film was formed on electrode surface by electrochemical reduction of 4-ethylnylphenyl (4-EP) diazonium compound. Then, horseradish peroxidase (HRP) modified with azido group was covalently immobilized onto the electrografted film via click reaction. Reflection absorption infrared (RAIR) spectroscopy and electrochemical methods were used to characterize the modification process. The results indicate that HRP retains its native structure and shows fast direct electron transfer. Moreover, the immobilized HRP shows excellent electrocatalytic reduction activity toward H2O2 with a linear range of 5.0×10−6 to 9.3×10−4molL−1.

The paper reports on covalent clicking of rhodamine-B (RhB) bearing a terminal azide group to alkyne-terminated silica coated superparamagnetic iron oxide nanoparticles via the copper(I)-catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. The course of the reaction was followed the use of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, fluoroscopy, and magnetics. The RhB labelled Fe3O4@SiO2 nanoparticles exhibit stable fluorescence and no detectable leakage of the fluorescent dye because the resulting 1,4-disubstituted 1,2,3-triazole ring formed via click reaction is thermally stable and relatively inert to hydrolysis, oxidation, and reduction. Due to the superparamagnetic property of the Fe3O4 and the RhB molecule covalently decorated in the Fe3O4@SiO2 framework, the nanoparticles are endowed with properties of a contrast agent in magnetic resonance imaging (MRI) and optical imaging modality. The cytotoxicity tests indicate the bifunctional nanoparticles could be applied in biomedical or bioengineering field.

A simple and versatile method for the introduction of redox unites onto the surface of magnetic nanoparticles has been developed based on "click" chemistry. Azide-functionalized Fe2O3 magnetic nanoparticles were synthesized and further reacted with ethynylferrocene via Cu(I)-catalyzed azide alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. The functionalized magnetic nanoparticles were characterized using a powder X-ray diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscope (FTIR), and vibrating sample magnetometer (VSM). The resulting materials have properties of both magnetism and electrochemistry, and the electrochemical properties of the nanoparticles are dependent on the features of ethynylferrocene, while the magnetic properties remain independent of ethynylferrocene. Because of the magnetism of Fe2O3 nanoparticles and the electrocatalytic activity of ferrocene unites, a recyclable, magneto-switchable bioelectrocatalytic system for glucose oxidation in the presence of glucose oxidase is developed by alternate positioning of an external magnet, and the system has a linear response for glucose biosensing over the range of 1.0-10.0 mM.

The effect of different post space irrigants on smear layer removal and dentin bond strength was evaluated. Sixty-six extracted sound maxillary central incisors were endodontically treated. After post space preparation, the teeth were assigned to three groups of 22 teeth each. The teeth of these three groups were irrigated for 1 min with 17% ethylenediaminetetracetic acid (EDTA) (group 1), 5.25% sodium hypochlorite (NaOCl) (group 2), or 0.9% sodium chloride (NaCl) (group 3). In each group, eight specimens were split longitudinally for smear layer evaluation, and the other fourteen specimens were filled with a self-etching adhesive system (Panavia F). Four of 14 specimens of each group were prepared for evaluation of the resin-dentin interdiffusion zone (RDIZ) and resin tags, and the other 10 specimens were serially sectioned for push-out test analysis. Smear layer removal and bond strength were affected by different post space irrigants. EDTA removed the smear layer extremely effectively and, as a result, improved the bond strength at each region (apical, middle, and coronal) of the roots. Resin tag formation and the RDIZ were also affected by different irrigants and in accordance with bond strength. Therefore, removal of the smear layer use a self-etching luting system plays an important role in bonding effectiveness.