Sulfidized Nanoscale Zerovalent Iron Research Articles

Iron Nanoparticle-Incorporated Laser-Induced Graphene Filters for Environmental Remediation via an In Situ Electro-Fenton Process.

Laser-induced graphene (LIG) has garnered much attention due to its facile and chemically free fabrication technique. Metal nanoparticle incorporation into the LIG matrix can improve its electrical and catalytical properties for environmental application. Here, we demonstrate the fabrication of nanoscale zerovalent iron (nZVI) nanoparticle-incorporated LIG (Fe-LIG) and sulfidized-nanoscale zerovalent iron (S-nZVI) nanoparticle-incorporated LIG (SFe-LIG) surfaces. The sheets were first fabricated to investigate nanoparticle loading, successful incorporation in the LIG matrix, and electrochemical performance as electrodes. Fe-LIG and SFe-LIG sheets showed ∼3-3.5 times more charge density as compared with the control LIG sheet. The XPS and its deconvolution confirmed the presence of nZVI and S-nZVI in the Fe-LIG and SFe-LIG surfaces, which can generate in situ hydroxyl radical (•OH) via iron activation of electrogenerated hydrogen peroxide (H2O2) in short in situ electro-Fenton process. After confirmation of the successful incorporation of iron-based nanoparticles in the LIG matrix, filters were fabricated to demonstrate the application in the flow-through filtration. The Fe-LIG and SFe-LIG filters showed ∼10-30% enhanced methylene blue removal under the application of 2.5 V at ∼1000 LMH flux. The Fe-LIG and SFe-LIG filters also showed complete 6-log bacteria and virus removal at 2.5 and 5 V, respectively, while the LIG filters showed only ∼4-log removal. Such enhanced removal by the Fe-LIG and SFe-LIG filters as compared to LIG filters is attributed to the improved charge density, electrochemical activity, and in situ electro-Fenton process. The study shows the potential to develop catalytic LIG-based surfaces for various applications, including contaminant removal and microbial inactivation.

High performance self-assembled sulfidized nanoscale zero-valent iron for the immobilization of cadmium in contaminated sediments: Optimization, microbial response, and mechanisms

Sulfidized nanoscale zero-valent iron (S-nZVI) showed excellent removal capacity for cadmium (Cd) in aqueous phase. However, the remediation effects of S-nZVI on Cd-contaminated sediment and its interactions with microorganisms in relation to Cd fate remain unclear. The complexity of the external environment posed a challenge for Cd remediation. This study synthesized S-nZVI with different S and Fe precursors to investigate the effect of precursors and applied the optimal material to immobilize Cd in sediments. Characterization analysis revealed that the precursor affected the morphology, Fe0 crystallinity, and the degree of oxidation of the material. Incubation experiments demonstrated that the immobilization efficiency of Cd using S-nZVIFe3++S2- (S/Fe = 0.14) reached the peak value of 99.54%. 1% and 5% dosages of S-nZVI significantly reduced Cd concentration in the overlying water, DTPA-extractable Cd content, and exchangeable (EX) Cd speciation (P < 0.05). Cd leaching in sediment and total iron in the overlying water remained at low levels during 90 d of incubation. Notably, each treatment maintained a high Cd immobilization efficiency under different pH, water/sediment ratio, organic acid, and coexisting ion conditions. Sediment physicochemical properties, functional bacteria, and a range of adsorption, complexation and precipitation of CdS effects dominated Cd immobilization.

Attapulgite-supported sulfidated nano Zero-Valent Iron activated persulfate advanced oxidation technology for degradation of polyethylene microplastics: Optimal design, change of particle size and degradation mechanisms

Microplastics (MPs), as a novel pollutant, have raised concerns about their potentialtoxicity and the wide-ranging ecological risks they may pose. In this study, a novel attapulgate-supported sulfidized nanoscale zero-valent iron (S-nZVI@ATP) catalyst was prepared for the activation of persulfate. We investigated the degradation efficiency and mechanism of polyethylene microplastics (PE) using the S-nZVI@ATP activated persulfate advanced oxidation process. Various factors, such as temperature,pH, catalyst dosage, and persulfate concentration, were evaluated for their influence on the oxidative reaction in the system to determine the optimal degradation conditions. The average particle size of PE decreased from 64.2±0.86μm to 28.1±0.91μm after 24 hours of oxidative degradation. The reaction progressed, TOC in the solution showed an initial increase, followed by a decrease. Some PE was oxidized into small molecules substances such as alkanes, alkenes, ketones, alcohols, and carboxylic acids. S-nZVI@ATP continuously supplied Fe2+ for persulfate activation, generating strong oxidants SO4•-, •OH, and 1O2, among which SO4•- played a dominant role in oxidation system. The heterogeneous advanced oxidation system provided in this study offers an effective reference for PE degradation and holds great promise as a method for degrading MPs in water.

Activation of persulfate by biochar-supported sulfidized nanoscale zero-valent iron for degradation of ciprofloxacin in aqueous solution: process optimization and degradation pathway.

The pollution of antibiotics, specifically ciprofloxacin (CIP), has emerged as a significant issue in the aquatic environment. Advanced oxidation processes (AOPs) are capable of achieving stable and efficient removal of antibiotics from wastewater. In this work, biochar-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC) was adopted to activate persulfate (PS) for the degradation of CIP. The impacts of different influencing factors such as S/Fe molar ratios, BC/S-nZVI mass ratios, PS concentration, S-nZVI/BC dosage, CIP concentration, initial pH, coexisting anions, and humic acid on CIP degradation efficiency were explored by batch experiments. The results demonstrated that the highest degradation ability of S-nZVI/BC was achieved when the S/Fe molar ratio was 0.07 and the BC/S-nZVI mass ratio was 1:1. Under the experimental conditions with 0.6 g/L S-nZVI/BC, 2 mmol/L PS, and 10 mg/L CIP, the degradation rate reached 97.45% after 90 min. The S-nZVI/BC + PS system showed significant degradation in the pH range from 3 to 9. The coexisting anions affected the CIP degradation efficiency in the following order: CO32- > NO3- > SO42- > Cl-. The radical quenching experiments and electron paramagnetic resonance (EPR) revealed that oxidative species, including SO4•-, HO•, •O2-, and 1O2, all contribute to the degradation of CIP, in which •O2- plays a particularly prominent role. Furthermore, the probable degradation pathway of CIP was explored according to the 12 degradation intermediates identified by LC-MS. This study provides a new idea for the activation method of PS and presents a new approach for the treatment of aqueous antibiotics with highly catalytic active nanomaterials.

Different sulfidized procedures and sulfur precursors alter the bacterial toxicity of sulfidized nanoscale zero-valent iron by affecting the physicochemical properties

Different sulfidized procedures and sulfur precursors influenced the bacterial toxicity of S-NZVI and the mechanisms.

Particle-Scale Understanding of Arsenic Interactions with Sulfidized Nanoscale Zerovalent Iron and Their Impacts on Dehalogenation Reactivity.

Co-occurrence of organic contaminants and arsenic oxoanions occurs often at polluted groundwater sites, but the effect of arsenite on the reactivity of sulfidized nanoscale zerovalent iron (SNZVI) used to remediate groundwater has not been evaluated. Here, we study the interaction of arsenite [As(III)] with SNZVI at the individual-particle scale to better understand the impacts on the SNZVI properties and reactivity. Surface and intraparticle accumulation of As was observed on hydrophilic FeS-Fe0 and hydrophobic FeS2-Fe0 particles, respectively. X-ray absorption spectroscopy indicated the presence of realgar-like As-S and elemental As0 species at low and high As/Fe concentration ratios, respectively. Single-particle inductively coupled plasma time-of-flight mass spectrometry analysis identified As-containing particles both with and without Fe. The probability of finding As-containing particles without Fe increased with the S-induced hydrophobicity of SNZVI. The interactions of SNZVI materials with coexisting arsenite inhibited their reactivity with water (∼5.8-230.7-fold), trichloroethylene (∼3.6-67.5-fold), and florfenicol (∼1.1-5.9-fold). However, the overall selectivity toward trichloroethylene and florfenicol relative to water was improved (up to 9.0-fold) because the surface-associated As increased the SNZVI hydrophobicity. These results indicate that reactions of SNZVI with arsenite can remove As from groundwater and improve the properties of SNZVI for dehalogenation selectivity.

Recent advances in sulfidized nanoscale zero-valent iron materials for environmental remediation and challenges.

Over the past decade, sulfidized nanoscale zero-valent iron (S-nZVI) has been developed as a promising tool for the remediation of contaminated soil, sediment, and water. Although most studies have focused on applying S-nZVI for clean-up purposes, there is still a lack of systematic summary and discussion from its synthesis, application, to toxicity assessment. This review firstly summarized and compared the properties of S-nZVI synthesized from one-step and two-step synthesis methods, and the modification protocols for obtaining better stability and reactivity. In the context of environmental remediation, this review outlined an update on the latest development of S-nZVI for removal of heavy metals, organic pollutants, antibiotic resistance genes (ARGs), and antibiotic resistant bacteria (ARB) and also discussed the underlying removal mechanisms. Environmental factors affecting the remediation performance of S-nZVI (e.g., humic acid, coexisting ions, S/Fe molar ratio, pH, and oxygen condition) were highlighted. Besides, the application potential of S-nZVI in advanced oxidation processes (AOP), especially in activating persulfate, was also evaluated. The toxicity impacts of S-nZVI on the environmental microorganism were described. Finally, the future challenges and remaining restrains to be resolved for better applicability of S-nZVI are also proposed. This review could provide guidance for the environmental remediation with S-nZVI-based technology from theoretical basis and practical perspectives.

Enhanced immobilization of cadmium in contaminated paddy soil by biochar-supported sulfidized nanoscale zero-valent iron

Enhanced immobilization of cadmium in contaminated paddy soil by biochar-supported sulfidized nanoscale zero-valent iron

Immobilization of cadmium in river sediments using sulfidized nanoscale zero-valent iron synthesized with different iron precursors: performance and mechanism

Immobilization of cadmium in river sediments using sulfidized nanoscale zero-valent iron synthesized with different iron precursors: performance and mechanism

Enhanced tetracycline abatement by peracetic acid activation with sulfidation of nanoscale zerovalent iron.

Iron-based heterogeneous catalysts due to the environmental friendliness have been widely studied for activation of peracetic acid (PAA) for abatement of organic contaminants in the water and wastewater treatment. However, the slow reduction from Fe(III) to Fe(II) of the iron-based catalysts as the rate-limiting step results in the low PAA activation efficiency. With regard to the excellent electron-donating capability of the reductive sulfur species, sulfidized nanoscale zerovalent iron is proposed for PAA activation (simplified as the S-nZVI/PAA process) and the tetracycline (TC) abatement efficacy and mechanism of this process are elucidated. The optimal sulfidation ratio (S/Fe) of S-nZVI is 0.07, which exhibits superior performance in PAA activation for TC abatement with the efficiency of 80-100% in the pH range of 4.0-10.0. The radical quenching experiments and oxygen release measurements confirm that acetyl(per)oxygen radicals (CH3C(O)OO•) are the main radical contributing to TC abatement. The influence of sulfidation on the crystalline structure, hydrophobicity, corrosion potential, and electron transfer resistance of S-nZVI is evaluated. The main sulfur species on the S-nZVI surface are identified as ferrous sulfide (FeS) and ferrous disulfide (FeS2). The analysis by X-ray photoelectron spectroscopy (XPS) and Fe(II) dissolution suggest that the reductive sulfur species can accelerate the conversion from Fe(III) to Fe(II). In summary, the S-nZVI/PAA process exhibits application prospects for the abatement of antibiotics in the aquatic environments.

Sulfidized state and formation: Enhancement of nanoscale zero-valent iron on biochar（S-nZVI/BC） in activating peroxymonosulfate for Acid Red 73 degradation

To improve the performance of the nanoscale zero-valent iron (nZVI)-based advanced oxidation process (AOPs), a sulfidation pre-modification endowed nZVI with stable reduction nature mechanism was proposed, and a coupled system of activating PMS with sulfidized nanoscale zero-valent iron supported by biochar(S-nZVI/BC@PMS) was constructed in this study. It could be found that sulfidation state and formation, largely dependent on the sulfidized modification method, had a great impact on the enhancement for nZVI/BC in activating PMS for Acid Red 73 degradation. Compared with original nZVI/BC, the formed FeS shell blocked the external air to protect the internal Fe0, and S-nZVI/BC became relatively hydrophobic, which could slow down the material corrosion by water and dissolved oxygen to enhance the reaction durability. Appropriate sulfidation reduced the electrochemical impedance and enhanced the electrical conductivity of the catalyst, which facilitated the electron transfer in the system, and the participation of reducing sulfur species enabled the reaction to form a positive cycle and ensure a prolonged duration. Excessive sulfidation caused the material to become unstable and thus susceptible to air erosion, reducing the efficiency of contaminant removal. Due to the FeS protective shell, hydrophobicity of S-nZVI/BC and the promoted electron transfer in the system, S-nZVI/BC@PMS system secured more free radicals and had longer reaction time under the same conditions. In addition, S-nZVI/BC had good antioxidant properties, universality, and reusability for practical applications. These findings not only elucidated the superiority of S-nZVI/BC@PMS system but also provided new insights into cost-saving and efficient advanced oxidation processes.

Efficient removal of Cd(II), Cu(II), and Pb(II) in aqueous solutions by exhausted copper slag supported sulfidized nanoscale zerovalent iron

Exhausted copper slag (ECS) is an industrially utilized secondary waste, and due to its large volume and potential environmental risks, the utilization of ECS in a safe manner is required. In this study, a novel synthetic composite (S-nZVI@ECS) was prepared by loading sulfidized nanoscale zerovalent iron (S-nZVI) onto ECS for the removal of Cd(II), Cu(II), and Pb(II) from aqueous solutions. The composite not only provides a new idea for utilizing ECS but also prevents S-nZVI particles from agglomerating. The optimized S-nZVI@ECS can achieve efficient removal of the three heavy metals over a wide pH range without being affected by coexisting ions (Na+, K+, Mg2+, Ca2+). With the respective maximum adsorption capacities of these three cationic heavy metals being as high as 173.01, 93.81, and 338.98 mg/g (based on the Langmuir model), the elimination of S-nZVI@ECS for these three cationic heavy metals could be fitted with the Langmuir and Freundlich models well, and the associated mechanisms (including redox reactions, complexation, and precipitation) were elucidated. The novel S-nZVI@ECS composites prepared in this study using secondary waste as a substrate have good potential for removing cationic heavy metals from aqueous solutions.

Adsorption-reduction coupling mechanism and reductive species during efficient florfenicol removal by modified biochar supported sulfidized nanoscale zerovalent iron

Sulfidized nanoscale zerovalent iron (S-nZVI) was a promising material for degrading halogenated contaminants, but the easy aggregation limits its application for in-situ groundwater remediation. Hence, S-nZVI was decorated onto modified biochar (mBC) to obtain better dispersity and reactivity with florfenicol (FF), a widely used antibiotic. Uniform dispersion of S-nZVI particles were achieved on the mBC with plentiful oxygen-containing functional groups and negative surface charge. Thus, the removal rate of FF by S-nZVI@mBC was 2.5 and 3.1 times higher than that by S-nZVI and S-nZVI@BC, respectively. Adsorption and dechlorination of FF showed synergistic effect under appropriate mBC addition (e.g., C/Fe mass ratio = 1:3, 1:1), probably due to the enrichment of FF facilitates its reduction. In contrast, the contact between FF and S-nZVI could be hindered under more mBC addition, significantly decrease the reduction rate of FF and the reduction capacity of per unit Fe0. In addition, sulfur dose altered the surface species of surface Fe and S, and removal rates of FF correlated well with surface reductive species, i.e., FeS (r = 0.90, p < 0.05) and Fe0 (r = 0.98, p < 0.01). These mechanistic insights indicate the importance of rational design for biochar supported S-nZVI, which can lead to more efficient FF degradation.

Sulfidized Nanoscale Zerovalent Iron Supported by Oyster Powder for Efficient Removal of Cr (VI): Characterization, Performance, and Mechanisms

In this study, sulfidized nanoscale zerovalent iron (S-nZVI) supported by oyster shell (OS) powder (S-nZVI@OS) was synthesized by controlling the initial S/Fe ratios (0.1–0.5) to explore the potential synergistic effects during the adsorption and reduction of Cr (VI). X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses showed that Fe (0) and FeS were well dispersed on the OS surface. Furthermore, the stability of S-nZVI@OS composite was higher than that of nZVI, which was proved by the material ageing experiment. The effects of different S/Fe molar ratios, time, temperature, the initial concentration of Cr (VI), and initial pH on the removal efficiency were also studied. The results indicated that with the increase of the S/Fe molar ratio, the removal capacity of Cr (VI) first increased rapidly and then decreased slowly. Batch experiments showed that an optimal S/Fe molar ratio of 0.2 offered a Cr (VI) removal capacity of about 164.7 mg/g at pH 3.5. The introduction of S can not only promote Cr (VI) reduction but also combine with Cr (III) by forming precipitate on S-nZVI@OS mainly as CrxFe(1−x) OOH and Cr2S3. The adsorption thermodynamics and kinetics demonstrated that the Langmuir model and pseudo-second-order kinetics model can describe the adsorption isotherms and kinetics. These results suggest that S-nZVI@OS is an effective and safe material for removing Cr (VI) from aqueous solutions.

Transformation of sulfidized nanoscale zero-valent iron particles and its effects on microbial communities in soil ecosystems

Sulfidized nanoscale zero-valent iron (S-nZVI) is a promising material for in situ soil remediation. However, its transformation (i.e., aging) and effects on the microbial community in soil ecosystems are largely unknown. In this study, S-nZVI having low (S-nZVI (L)) and high sulfur-doping (S-nZVI (H)) were incubated in soil microcosms and bare nZVI was used as a control. Their aged products were characterized using microspectroscopic analyses and the changes in the corresponding soil microbial community were determined using high-throughput sequencing analyses. The results indicate that severe corrosion of both bare and S-nZVI occurred over 56 days of aging with significant morphological and mineral changes. Magnetite, lepidocrocite, and goethite were detected as the main aged products. In addition, sulfate ions, pyrite, and iron polysulfide were formed in the aged products of S-nZVI. Cr(VI) removal test results indicated that S-nZVI(L) achieved the best results after aging, likely because of the optimal FeS arrangement on its nanoparticle surfaces. The presence of nZVI and S-nZVI increased the abundance of some magnetotactic microorganisms and altered bacterial and fungal community structures and compositions. Moreover, the addition of S-nZVI enriched some bacterial and fungal genera related to sulfur cycling because of the presence of sulfide-bearing material. The findings reveal the transformation of S-nZVI during aging and its effects on microbial communities in soil ecosystems, thereby helping to the evaluation of S-nZVI application in soil remediation.

Molecular Structure and Sulfur Content Affect Reductive Dechlorination of Chlorinated Ethenes by Sulfidized Nanoscale Zerovalent Iron.

Sulfidized nanoscale zerovalent iron (SNZVI) with desirable properties and reactivity has recently emerged as a promising groundwater remediation agent. However, little information is available on how the molecular structure of chlorinated ethenes (CEs) affects their dechlorination by SNZVI or whether the sulfur content of SNZVI can alter their dechlorination pathway and reactivity. Here, we show that the reactivity (up to 30-fold) and selectivity (up to 70-fold) improvements of SNZVI (compared to NZVI) toward CEs depended on the chlorine number, chlorine position, and sulfur content. Low CEs (i.e., vinyl chloride and cis-1,2-dichloroethene) and high CEs (perchloroethene) tended to be dechlorinated by SNZVI primarily via atomic H and direct electron transfer, respectively, while SNZVI could efficiently and selectively dechlorinate trichloroethene and trans-1,2-dichloroethene via both pathways. Increasing the sulfidation degree of SNZVI suppressed its ability to produce atomic H but promoted electron transfer and thus altered the relative contributions of atomic H and electron transfer to the CE dechlorination, resulting in different reactivities and selectivities. These were indicated by the correlations of CE dechlorination rates and improvements with CE molecular descriptors, H2 evolution rates, and electron transfer indicators of SNZVI. These mechanistic insights indicate the importance of determining the structure-specific properties and reactivity of both SNZVI materials and their target contaminants and can lead to a more rational design of SNZVI for in situ groundwater remediation of various CEs.

A comparative study on the physicochemical properties, reactivity and long-term performance of sulfidized nanoscale zerovalent iron synthesized with different kinds of sulfur precursors and procedures in simulated groundwater

There are plentiful ways to synthesize sulfidized nanoscale zerovalent iron (S-nZVI), and this study investigated the influence of sulfur reagents (Na2S, Na2S2O3, Na2S2O4) and sulfidation sequence (co-sulfidation and post-sulfidation method) on the physicochemical properties, reactivity, and long-term performance of S-nZVI in simulated groundwater. The results suggested that the co-sulfidized nZVI (S-nZVIco) has higher reactivity (∼2-fold) than S-nZVIpost due to the stronger electron transfer capacity, deriving from the higher content of Fe0 and reductive sulfur species. However, during aging, the reactivity of S-nZVIco would be lost more rapidly than S-nZVIpost, due to the faster corrosion of Fe0 and more oxidation of reductive sulfur species. S-nZVIpost has the superior long-term performance with the degradation rate of trichloroethylene (TCE) remained at 30%∼60% even after 90 d of aging. Sulfur precursors can control the selectivity of S-nZVI by affecting the sulfur speciation on the particle surface. The proportion of reductive sulfur species on S-nZVIpost synthesized by Na2S was higher than S-nZVIpost synthesized by Na2S2O3 or Na2S2O4, resulting in a higher selectivity of the former S-nZVIpost than the latter S-nZVIpost. In addition, sulfidation procedures and sulfur precursors did not affect the degradation pathway of TCE. Nevertheless, the degradation product distribution can be affected by the different physicochemical transformation of various types of S-nZVI with the aging time. These results indicated that sulfur reagents and sulfidation procedures have crucial effects on the reactivity and long-term performance of S-nZVI, which can be designed for the specific application scenarios.

Effective removal of heavy metal ions by attapulgite supported sulfidized nanoscale zerovalent iron from aqueous solution

Sulfidation of nanoscale zero valent iron (nZVI) has attracted increasing interest for improving the reactivity and selectivity of nZVI towards heavy metal ions. In this study, attapulgite-loaded sulfide modified nZVI (APT/S-nZVI) was synthesized, and used for removal Cr(Ⅵ), Cu(Ⅱ) and Zn(Ⅱ) alone or coexisting. The morphology and structure characterizations indicated that sulfide-modified nZVI particles were well distributed and immobilized on the attapulgite surface. Batch experiments of Cr(Ⅵ), Cu(Ⅱ) and Zn(Ⅱ) removal were conducted at varying mass ratios, S/Fe ratios, pH and initial concentrations. Moreover, kinetic and thermodynamic analyses were used to study the removal process, and possible mechanisms of removal for Cr(Ⅵ), Cu(Ⅱ) and Zn(Ⅱ) were discussed. The results of removal performance tests demonstrated that APT/S-nZVI displayed high removal capacity and fast removal rate for three heavy metal ions compared to the nZVI, which derived from the synergistic effects of the strongly reducing characteristics of nZVI combined with high electronic conductivity of FeS and high surface area of APT. Dynamic studies revealed that the removal process was highly consistent with the pseudo-second-order model for three metal ions adsorption and reaction process. Additionally, combined the value of activation energy, it has been proved that the removal Cr(VI) and Cu(Ⅱ) were controlled by chemical surface-limiting step, and removal Zn(Ⅱ) was controlled by chemically diffusion step. The modification of S changes the removal mechanism between APT/S-nZVI and metal ions, which is closely related to the redox potential of metal ion and the solubility product constant (Ksp) of metal sulfides. Overall, the work suggests that APT/S-nZVI has a good potential for the elimination of micropollutants in the aquatic environment.

Adsorption-Reduction Coupling Mechanism and Reductive Species During Efficient Florfenicol Removal by Modified Biochar Supported Sulfidized Nanoscale Zerovalent Iron

Adsorption-Reduction Coupling Mechanism and Reductive Species During Efficient Florfenicol Removal by Modified Biochar Supported Sulfidized Nanoscale Zerovalent Iron

Adsorption-Reduction Coupling Mechanism and Reductive Species During Efficient Florfenicol Removal by Modified Biochar Supported Sulfidized Nanoscale Zerovalent Iron

Adsorption-Reduction Coupling Mechanism and Reductive Species During Efficient Florfenicol Removal by Modified Biochar Supported Sulfidized Nanoscale Zerovalent Iron