Nanoscale Zero-valent Iron Research Articles

Efficient removal of Cr(VI) by sulfide nanoscale zero-valent iron: Characterization, aging and mechanism

In the research, sulfide nanoscale zero-valent iron (S-nZVI) was synthesized, characterized and further applied to remove hexavalent chromium Cr(VI) from water. The results showed that a maximum adsorption (81 mg/g) and repeatability was reached at a sulfur/iron molar ratio of 0.1. Sulfide modification could form amorphous FeS on the surface of nZVI, which enhanced the antioxidant activity and hydrophobicity of S-nZVI0.1. The removal of Cr(VI) by S-nZVI0.1 was in accordance with the pseudo-second-order and Langmuir model with the theoretical removal capacity of 83.51 mg/g. After aging 45 d, 60 mg/g of Cr(VI) still was adsorbed by S-nZVI0.1, suggesting that S-nZVI0.1 exhibited a better stability. 84.1 % of Cr(VI) was reduced to Cr(III) on the surface of S-nZVI0.1, Fe0, FeS, Fe2+ and S2− were involved in the reduction reaction. This study provided guidance for synthesizing well stability and high reaction of S-nZVI to remove Cr(VI).

Enhanced hydrodechlorination of 4-chlorophenol through carboxymethylcellulose-modified Pd/Fe nanosuspension synthesized by one-step methods

Palladized iron (Pd/Fe) represents one of the most common modification strategies for nanoscale zero-valent iron (nZVI). Most studies prepared Pd/Fe by reducing iron salts and depositing Pd species on the surface of pre-synthesized nZVI, which can be called the two-step method. In this study, we proposed a one-step method to obtain Pd/Fe by the concurrent formation of Fe0 and Pd0 and investigated the effects of these two methods on 4-chlorophenol (4-CP) removal, with carboxymethylcellulose (CMC) coated as a surface modifier. Results indicated that the one-step method, not only streamlined the synthesis process, but also Pd/Fe-CMCone-step, synthesized by it, exhibited a higher 4-CP removal rate (97.9%) compared to the two-step method material Pd/Fe-CMCtwo-step (82.4%). Electrochemical analyses revealed that the enhanced activity of Pd/Fe-CMCone-step was attributed to its higher electron transfer efficiency and more available reactive species, active adsorbed hydrogen species (Hads*). Detection of intermediate products demonstrated that, under the influence of Pd/Fe-CMCone-step, the main route of 4-CP was through hydrodechlorination (HDC) to form phenol and H* was the main active specie, supported by EPR tests, quenching experiments and product analysis. Additionally, the effects of initial 4-CP concentration, initial pH, O2 concentration, anions such as Cl−, SO42−, HCO3−, and humic acid (HA) were also investigated. In conclusion, the results of this study suggest that Pd/Fe-CMCone-step, synthesized through the one-step method, is a convenient and efficient nZVI-modifying material suitable for the HDC of chlorinated organic compounds.

Catalytic activation of persulfate by nanoscale zero-valent iron-derived supported boron-doped porous carbon for bisphenol A degradation.

In this study, boron-doped porous carbon materials (BCs) with high surface areas were synthesized employing coffee grounds as carbon source and sodium bicarbonate and boric acid as precursors; afterward, nanoscale zero-valent iron (nZVI) and BCs composites (denoted as nZVI@BCs) were further prepared through reduction of FeSO4 by NaBH4 along with stirring. The performance of the nZVI@BCs for activating persulfate (PS) was evaluated for the degradation of bisphenol A (BPA). In comparison with nZVI@Cs/PS, nZVI@BCs/PS could greatly promote the degradation and mineralization of BPA via both radical and non-radical pathways. On the one hand, electron spin resonance and radical quenching studies represented that •OH, SO4•-, and O2•- were mainly produced in the nZVI@BCs/PS system for BPA degradation. On the other hand, the open circuit voltages of nZVI@BCs and nZVI@Cs in different systems indicated that non-radical pathway still existed in our system. PS could grab the unstable unpaired electron on nZVI@BCs to form a carbon material surface-confined complex ([nZVI@BCs]*) with a high redox potential, then accelerate BPA removal efficiency via direct electron transfer. Furthermore, the performances and mechanisms for BPA degradation were examined by PS activation with nZVI@BC composites at various conditions including dosages of nZVI@BCs, BPA and PS, initially pH value, temperature, common anions, and humid acid. Therefore, this study provides a novel insight for development of high-performance carbon catalysts toward environmental remediation.

Ecological effects of biochar-supported nanoscale zero-valent iron on Eisenia foetida in cadmium-contaminated soil: Oxidative stress, DNA damage, gene expression and transcriptomics analysis

Biochar-supported nanoscale zero-valent iron (nZVI@BC) has been widely used in heavy metal contaminated soil for remediation. However, studies on the soil ecological effects of nZVI@BC were rare. In this study, nZVI@BC was synthesized by the liquid phase reduction and GnZVI@BC was prepared by a green synthesis method which was reduced by green tea extract instead of NaBH4. Earthworms (Eisenia foetida) as indicator organisms were exposed to Cd-contaminated soil. The immobilization effects and enrichment in earthworms of Cd were measured. Besides, oxidative stress, DNA damage, gene expression and transcriptomics of earthworms were deeply explored. The results indicated that the immobilization efficiency of BC, nZVI@BC and GnZVI@BC for Cd was 76.01%, 85.49%, and 80.76%, respectively. The effects of Cd on superoxide dismutase, glutathione S-transferase, peroxidase, and catalase in earthworms reduced, reactive oxygen species and malondialdehyde contents decreased, and DNA damage was relieved. In addition, the gene toxicity of Cd to earthworms was restrained, and the genes expression of sod, cat and gst tended to be stable. With nZVI@BC, the main pathways affected by the differential genes were cellular oxidative phosphorylation and transforming growth factor-β signaling pathways. With GnZVI@BC, there were mainly structure of the cell phagosome, metabolism of taurine, hypotaurine, and alanine processes. This study will provide references for ecological risk assessment of nZVI@BC in practical applications.

Nano zero-valent iron/montmorillonite composite for the removal of Cr(VI) from aqueous solutions: Characterization, performance, and mechanistic insights

Infiltration of hexavalent chromium (Cr(VI)) into the human body poses significant health risks, including the risk of developing cancer and increased mortality rates. The discharge of chromium-contaminated wastewater from industrial processes exacerbates environmental pollution, highlighting the necessity for efficient, cost-effective, and environmentally friendly treatment methods. In recent years, there has been a growing emphasis on the application of nanoscale zero-valent iron particles (NZVI) for mitigating Cr(VI) water pollution. In the present study, NZVI was synthesized using a liquid-phase reduction method employing sodium borohydride (NaBH4), and natural montmorillonite (Mt) was incorporated as a carrier, resulting in the creation of NZVI/Mt., a composite material. Characterization of this composite was performed using scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), Specific surface area and pore size (BET), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) techniques. The investigation encompassed an exploration of the influence of initial pollutant pH levels, adsorbent dosages, and initial pollutant concentrations on the adsorption process. The research findings indicate that, at an initial pH of 4.0, NZVI/Mt. achieves a removal efficiency of 92.41% for a Cr(VI) solution with an initial concentration of 40 mg/L. The NZVI/Mt. composite adheres to both a pseudo-second-order kinetic model and the Langmuir isotherm model, showcasing a significant maximum adsorption capacity of 67.75 mg/g for Cr(VI). Furthermore, thermodynamic analysis revealed an exothermic nature of the adsorption process. This experimental approach effectively resolved issues related to NZVI particle agglomeration, offering a simplified, cost-effective, and environmentally friendly preparation method. Consequently, the NZVI/Mt. composite material demonstrates effective treatment of Cr(VI) mildly contaminated wastewater.

Core Soil Microorganisms and Abiotic Properties as Key Mechanisms of Complementary Nanoscale Zerovalent Iron and Nitrification Inhibitors in Decreasing Paclobutrazol Residues and Nitrous Oxide Emissions.

Agrochemical residues and nitrous oxide (N2O) emissions have caused considerable threats to agricultural soil ecology. Nanoscale zerovalent iron (nZVI) and nitrification inhibitors might be complementary to each other to diminish soil agrochemical residues and N2O emissions and enhance soil bacterial community diversities. Compared to the control, the nZVI application declined soil paclobutrazol residues by 5.9% but also decreased the bacterial community co-occurrence network node. Combined nZVI and Dicyandiamide applications significantly decreased soil N2O emission rates and paclobutrazol residues but promoted Shannon diversity of the bacterial community. The increased soil pH, ammonium nitrogen, and Actinobacteriota could promote soil paclobutrazol dissipation. The nZVI generated double-edged sword effects of positively decreasing paclobutrazol residues and N2O emissions but negatively influencing soil multifunctionalities. The nZVI and Dicyandiamide could be complementary to each other in diminishing soil agrochemical residues and N2O emission rates but promoting soil bacterial community diversities simultaneously.

Nano zerovalent Fe did not reduce metal(loid) leaching and ecotoxicity further than conventional Fe grit in contrasting smelter impacted soils: A 1-year field study

The majority of the studies on nanoscale zero-valent iron (nZVI) are conducted at a laboratory-scale, while field-scale evidence is scarce. The objective of this study was to compare the metal(loid) immobilization efficiency of selected Fe-based materials under field conditions for a period of one year. Two contrasting metal(loid) (As, Cd, Pb, Zn) enriched soils from a smelter-contaminated area were amended with sulfidized nZVI (S-nZVI) solely or combined with thermally stabilized sewage sludge and compared to amendment with microscale iron grit. In the soil with higher pH (7.5) and organic matter content (TOC = 12.7 %), the application of amendments resulted in a moderate increase in pH and reduced As, Cd, Pb, and Zn leaching after 1-year, with S-nZVI and sludge combined being the most efficient, followed by iron grit and S-nZVI alone. However, the amendments had adverse impacts on microbial biomass quantity, S-nZVI being the least damaging. In the soil with a lower pH (6.0) and organic matter content (TOC = 2.3 %), the results were mixed; 0.01 M CaCl2 extraction data showed only S-nZVI with sludge as remaining effective in reducing extractable concentrations of metals; on the other hand, Cd and Zn concentrations were increased in the extracted soil pore water solutions, in contrast to the two conventional amendments. Despite that, S-nZVI with sludge enhanced the quantity of microbial biomass in this soil. Additional earthworm avoidance data indicated that they generally avoided soil treated with all Fe-based materials, but the presence of sludge impacted their preferences somewhat. In summary, no significant differences between S-nZVI and iron grit were observed for metal(loid) immobilization, though sludge significantly improved the performance of S-nZVI in terms of soil health indicators. Therefore, this study indicates that S-nZVI amendment of soils alone should be avoided, though further field evidence from a broader range of soils is now required.

Activation of persulfate by g-C3N4/nZVI@SBC for degradation of total petroleum hydrocarbon in groundwater

In this study, we synthesized a high removal efficiency catalyst using biochar-supported nanoscale zero-valent iron and g-C3N4, denoted as g-C3N4/nZVI@SBC, to activate persulfate (PS) for the degradation of total petroleum hydrocarbon (TPH) in groundwater. We characterized the morphology and physiochemical properties of g-C3N4/nZVI@SBC with scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), BET surface area analysis, and X-ray photoelectron spectroscopy (XPS). To assess the performance of the g-C3N4/nZVI@SBC catalyst, we investigated various reaction parameters, such as the mass ratio of g-C3N4 to nZVI@SBC, PS concentration, initial pH, initial TPH concentration, and the presence of coexisting ions in the system. The results from batch experiments and repeated use trials indicate that g-C3N4/nZVI@SBC exhibited both excellent catalytic activation capability and impressive durability, making it a promising choice for TPH degradation. Specifically, when the PS concentration reached 1 mM, the catalyst dosage was 0.3 g/L, and the g-C3N4 to nZVI@SBC mass ratio was 2, we achieved a remarkable TPH removal efficiency of 93.8%. Through electron paramagnetic resonance (EPR) testing and quenching experiments, we identified sulfate radicals, hydroxyl radicals, and superoxide radicals as the primary active substance involved in the TPH degradation process. Moreover, the g-C3N4/nZVI@SBC composite proved highly effective for in-situ TPH removal from groundwater and displayed an 86% removal rate, making it a valuable candidate for applications in permeable reactive barriers (PRB) aimed at enhancing environmental remediation. In summary, by skillfully utilizing g-C3N4/nZVI@SBC, this study has made notable advancements in synthesis and characterization, presenting a feasible and innovative approach to addressing TPH pollution in groundwater.

Removal of dyes from wastewater using Eucalyptus wood fiber loaded nanoscale zero-valent iron: Characterization and removal mechanism

Wood fiber as a natural and renewable material has low cost and plenty of functional groups, which owns the ability to adsorb dyes. In order to improve the application performance of wood fiber in dye-pollution wastewater, Eucalyptus wood fiber loaded nanoscale zero-valent iron (EWF-nZVI) was developed to give EWF magnetism and the ability to degrade dyes. EWF-nZVI was characterized via FTIR, XRD, zeta potential, VSM, SEM-EDS and XPS. Results showed that EWF-nZVI owned a strong magnetism of 96.51 emu/g. The dye removal process of EWF-nZVI was more in line with the pseudo-second-order kinetics model. In addition, the Langmuir isotherm model fitting results showed that the maximum removal capacities of Congo red and Rhodamine B by EWF-nZVI were 714.29 mg/g and 68.49 mg/g at 328 K, respectively. After five adsorption-desorption cycles, the regeneration efficiencies of Congo red and Rhodamine B were 74 % and 42 % in turn. The dye removal mechanisms of EWF-nZVI included redox degradation (Congo red and Rhodamine B) and electrostatic adsorption (Congo red). In summary, EWF-nZVI is a promising biomass-based material with high dye removal capacities. This work is beneficial to promote the large-scale application of wood fiber in water treatment.

Carboxymethyl cellulose stabilization induced changes in particle characteristics and dechlorination efficiency of sulfidated nanoscale zero-valent iron

Polymer stabilization, exemplified by carboxymethyl cellulose (CMC), has demonstrated effectiveness in enhancing the transport of nanoscale zero-valent iron (nZVI). And, sulfidation is recognized for enhancing the reactivity and selectivity of nZVI in dechlorination processes. The influence of polymer stabilization on sulfidated nZVI (S-nZVI) with various sulfur precursors remains unclear. In this study, CMC-stabilized S-nZVI (CMC-S-nZVI) was synthesized using three distinct sulfur precursors (S2−, S2O42−, and S2O32−) through one-step approach. The antioxidant properties of CMC significantly elevated the concentration of reduced sulfur species (S2−) on CMC-S-nZVIs, marking a 3.1–7.0-fold increase compared to S-nZVIs. The rate of trichloroethylene degradation (km) by CMC-S-nZVIs was observed to be 2.2–9.0 times higher than that achieved by their non-stabilized counterparts. Among the three CMC-S-nZVIs, CMC-S-nZVINa2S exhibited the highest km. Interesting, while the electron efficiency of CMC-S-nZVIs surged by 7.9–12 times relative to nZVI, it experienced a reduction of 7.0–34% when compared with S-nZVIs. This phenomenon is attributed to the increased hydrophilicity of S-nZVI particles due to CMC stabilization, which inadvertently promotes the hydrogen evolution reaction (HER). In conclusion, the findings of this study underscores the impact of CMC stabilization on the properties and dechlorination performance of S-nZVI sulfidated using different sulfur precursors, offering guidance for engineering CMC-S-nZVIs with desirable properties for contaminated groundwater remediation.

Magnetic triiron tetraoxide/biochar–loaded nanoscale zero-valent iron for chromium(VI) removal from aqueous solution

BackgroundTo inhibit the agglomeration of nanoscale zero-valent iron (nZVI or Fe0), increase its stability and facilitate electron transfer, magnetic triiron tetraoxide/biochar (MBC) was used as the carrier to load nZVI. Consequently, a new pathway was created for electron transfer from nZVI to triiron tetraoxide (Fe3O4) and then to contaminants, thereby improving the chemical reactivity of nZVI. MethodsMagnetic triiron tetraoxide/biochar–loaded nanoscale zero-valent iron (nZVI@MBC) composites were prepared for chromium(VI) adsorption. Different influencing aspects were studied, including the loading percentage of nZVI, solution pH, co-existing anions(PO43−, SO42−, Cl−, NO3−), temperature and reusability. Furthermore, the adsorption isotherms, kinetics and thermodynamics for Cr(VI) removal were performed. Significant findingsnZVI@MBC exhibited an adsorption amount of 117.25 mg g−1 at the optimal conditions (dosage 0.4 g L−1, initial concentration 50 mg L−1, temperature 30 °C, nZVI loading percentage onto MBC 5.0 wt% and pH 2). The adsorption data obeyed the pseudo-second-order kinetics model and followed the Langmuir isotherm, thermodynamic characteristics revealed that Cr(VI) adsorption onto nZVI@MBC was a spontaneous endothermic process. After four recycles, the Cr(VI) removal efficiency remained higher than 70 %, exhibiting a good reusable ability. The mechanisms were confirmed to be physical adsorption, chemical reduction and co-precipitation processes.

Method validation of an inductive measurement system (IMS) for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns

The purpose of this work was to develop and validate a rapid, non-destructive, real-time measurement system for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns. This aims to provide an approach to analyse for nZVI particle transport and nZVI induced contaminant degradation reactions in 1-dimensional aquifer experiments. The inductive measurement system (IMS) was developed and tested by measuring columns filled with varying portions of nZVI and sandy aquifer material. Method validation was conducted for this innovative approach in accordance with several guidelines in disciplinary areas. The linearity of ZVI concentration and measurement signal was confirmed. Calibration curves were determined to be linear over the range of 0.11–53.50 g/L for nZVI NANOFER STAR, 0.10–81.67 g/L for nZVI BASF 1, 0.12–58.26 g/L for nZVI Carbo-Iron, 0.12–69.70 g/L for nZVI NANOFER 25DS ORM, 0.12–50.69 g/L for nZVI NANOFER 25DS, and 0.21–1613.39 g/L for nZVI Höganäs 1* (dry). This method was determined to be sensitive in nZVI, accurate (101.63 % within-run recovery, 101.85 % between-run recovery covering 76 days), and precise (0.46 % repeatability RSD, 0.85 % intermediate precision RSD covering 76 days). LOQ was determined ranging from 0.10 to 0.21 g/L for nZVI used in experiments and regression through origins was selected as the calibration model. Quality control processes were performed to assure the reliability of the results and the long-term stability. Additional data processing steps allowed to compensate for measurement deviations resulting from different liquid phase compositions, e.g. dispersants used for nZVI suspensions. This method is now successfully validated in single-laboratory conditions.

Penicillium oxalicum SL2-enhanced nanoscale zero-valent iron effectively reduces Cr(VI) and shifts soil microbiota

Most current researches focus solely on reducing soil chromium availability. It is difficult to reduce soil Cr(VI) concentration below 5.0 mg kg-1 using single remediation technology. This study introduced a sustainable soil Cr(VI) reduction and stabilization system, Penicillium oxalicum SL2–nanoscale zero-valent iron (nZVI), and investigated its effect on Cr(VI) reduction efficiency and microbial ecology. Results showed that P. oxalicum SL2–nZVI effectively reduced soil total Cr(VI) concentration from 187.1 to 3.4 mg kg–1 within 180 d, and remained relatively stable at 360 d. The growth curve of P. oxalicum SL2 and microbial community results indicated that γ-ray irradiation shortened the adaptation time of P. oxalicum SL2 and facilitated its colonization in soil. P. oxalicum SL2 colonization activated nZVI and its derivatives, and increased soil iron bioavailability. After restoration, the negative effect of Cr(VI) on soil microorganisms was markedly alleviated. Cr(VI), Fe(II), bioavailable Cr/Fe, Eh, EC and urease (SUE) were the key environmental factors of soil microbiota. Notably, Penicillium significantly stimulated the growth of urease-positive bacteria, Arthrobacter, Pseudarthrobacter, and Microvirga, synergistically reducing soil chromium availability. The combination of P. oxalicum SL2 and nZVI is expected to form a green, economical and long-lasting Cr(VI) reduction stabilization strategy.

Processes and mechanisms in remediation of aqueous chromium contamination by sulfidated nano-scale zerovalent iron (S-nZVI): Experimental and computational investigations

Sulfidated nano-scale zerovalent iron (S-nZVI) has emerged as an advanced functional nanomaterial for efficiently remediating Cr(VI) contamination in aqueous environments. However, there is an insufficient understanding of its coherent process, removal pathway, and hydrochemical reactive mechanisms, presenting potential challenges for its future environmental applications. To address this gap, this study successfully synthesized S-nZVI through a chemical precipitation method and effectively applied it for the removal of Cr(VI). Additional characterization revealed that the removal of Cr(VI) followed a sequence of rapid chemisorption and intraparticle diffusion processes, concomitant with an increase in pH and a decrease in oxidation-reduction potential. The remediation mechanism encompassed a synergistic reduction of Cr(VI) to Cr(III) and simultaneous immobilization via Cr2FeO4 coprecipitation. The highest Cr(VI) removal capacity of 75 mg/g was attained during dynamic removal experiments in the sand column packed with S-nZVI. Further computational analysis, employing density functional theory calculations based on the experimental data, revealed the involvement of multiple molecular orbitals of Cr(VI) in the removal process. It also elucidated a step-by-step reduction pathway for Cr(VI) characterized by decreasing free energy. These findings provide evidence-based insights into Cr(VI) remediation using S-nZVI and can serve as valuable technical support for future environmental management of heavy metals.

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.

Study on the kinetics and mechanisms of Cr(VI) removal by nZVI modified with four modifiers

To improve the nanoscale zero-valent iron (nZVI) utilization efficiency in environmental remediation and explore the performance enhancement mechanisms, the treatment of chromium pollution by pyrogallic acid modified nZVI (pyGA-nZVI), sodium dihydrogen phosphate modified nZVI (MSP-nZVI), ethylenediamine modified nZVI (EDA-nZVI) and sodium persulfate modified nZVI (PS-nZVI) were investigated in this study. The characterization of modified nZVIs demonstrated the successful bonding of modifiers onto nZVIs. Among the four modified materials, pyGA-nZVI exhibited the highest Cr(VI) removal performance (complete removal within 4 min), followed by MSP-nZVI (81.7 % within 30 min), EDA-nZVI (77.1 % within 30 min) and PS-nZVI (55.1 % within 30 min). The H2 production was all suppressed due to the presence of modifiers, boosting the electronic selectivity in the reaction with Cr(VI). Fe0 was the main contributor to the reduction of Cr(VI) by nZVI, EDA-nZVI and PS-nZVI, whereas Fe(II) played a major role in Cr(VI) reduction by pyGA-nZVI and MSP-nZVI. The decrease of element P and S contents indicated the direct involvement of MSP and PS in Cr(VI) removal, while the same content of N on nZVI before and after reaction implied an indirect participation of EDA in Cr(VI) removal.

Targeted degradation of Bisphenol A with peroxymonosulfate activated by nanoscale zero-valent iron supported on molecularly imprinted polymers

In order to address the limitation of active species being influenced by the complex water environment during the degradation of target pollutants, a catalyst called MIP-nFe0 was prepared. This catalyst consists of nanoscale zero-valent iron (nFe0) supported on molecularly imprinted polymers (MIPs) with specific recognition. It was designed for the targeted degradation of Bisphenol A (BPA) by activating peroxymonosulfate (PMS). Material characterization confirmed that nFe0 was successfully loaded onto MIPs without agglomeration and did not cause significant damage to the MIPs structure. Under specific conditions (50 mg/L BPA and 100 mg/L catalyst), PMS activation with MIP-nFe0 rapidly degraded most BPA in just 0.5 min. Competitive adsorption and degradation experiments revealed that MIP-nFe0 displayed the best adsorption (21.02 mg/g) and degradation (28.89 mg/g) efficiency for BPA compared with the control materials nFe0 and nFe0 supported on non-imprinted polymer (NIP-nFe0). MIP-nFe0 was further applied in the actual water background for BPA removal, MIP-nFe0 maintained efficient BPA removal in both river water as well as sewage plant tail water, which was significantly higher than NIP-nFe0 and nFe0. Free radical capture and quenching experiments demonstrated that active species of SO4−·, ·OH, ·O2−, and 1O2 existed in the system, with SO4−· played a major role.

Remediation of Cr(VI)-contaminated soil by double-modified nanoscale zero-valent iron: performance and mechanism

Remediation of Cr(VI)-contaminated soil by double-modified nanoscale zero-valent iron: performance and mechanism

Nano zero-valent iron and melatonin synergistically alters uptake and translocation of Cd and As in soil-rice system and mechanism in soil chemistry and microbiology

Nanoscale zero-valent iron (Fe) is a promising nanomaterial for remediating heavy metal-contaminated soils. Melatonin (MT) is essential to alleviate environmental stress in plants. However, the conjunction effects of Fe and MT (FeMT) on rice Cd, As accumulation and the mechanism of soil chemical and microbial factors interaction are unclear. Here, a pot experiment was conducted to evaluated the effects of the FeMT for rice Cd, As accumulation and underlying mechanisms. The findings showed that FeMT significantly reduced grains Cd by 92%–87% and As by over 90%, whereas improving grains Fe by over 213%. Soil available-Cd and iron plaques-Cd (extracted by dithionite-citrate-bicarbonate solution, DCB-Cd) significantly regulated roots Cd, thus affected Cd transport to grains. Soil pH significantly affected soil As and DCB-As, which further influenced roots As uptake and the transport to shoots and grains. The interactions between the soil bacterial community and soil Fe, available Fe, and DCB-Fe together affected root Fe absorption and transportation in rice. FeMT significantly influenced rhizosphere soil bacterial α- and β-diversity. Firmicutes as the dominant phylum exhibited a significant positive response to FeMT measure, and acted a key role in reducing soil Cd and As availability mainly by improving iron-manganese plaques. The increase of soil pH caused by FeMT was beneficial only for Actinobacteriota growth, which reduced Cd, As availability probably through complexation and adsorption. FeMT also showed greater potential in reducing human health and ecological risks by rice consumption and straw returning. These results showed the important role of both soil chemical and microbial factors in FeMT-mediated rice Cd, As reduction efficiency. This study opens a novel strategy for safe rice production and improvement of rice iron nutrition level in heavy-metals polluted soil, but also provides new insights into the intricate regulatory relationships among soil biochemistry, toxic elements, microorganism, and plants.

Green cleanup of styrene-contaminated soil by carbon-based nanoscale zero-valent iron and phytoremediation: Sunn hemp (Crotalaria juncea), zinnia (Zinnia violacea Cav.), and marigold (Tagetes erecta L.)

Accidental chemical spills can result in styrene-contaminated soil. Styrene negatively affects human health and the environment. The objective of this study was to remediate styrene-contaminated soil using a combination of activated carbon-based nanoscale zero-valent iron (nZVI-AC) and phytoremediation by sunn hemp (Crotalaria juncea), zinnia (Zinnia violacea Cav.) and marigolds (Tagetes erecta L.). The results showed that all three plant types could potentially increase the removal efficiency of styrene-contaminated soil. At 28 days, all three plants showed complete removal of styrene from the soil with 1 g/kg of nZVI-AC, activated carbon-based nZVI synthesized by tea leaves (Camellia sinensis) (T-nZVI-AC), or activated carbon-based nZVI synthesized by red Thai holy basil (Ocimum tenuiflorum L.) (B-nZVI-AC). However, styrene removal efficiencies of sunn hemp, zinnia, and marigold without carbon-based nZVI were 30%, 67%, and 56%, respectively. Statistical analysis (ANOVA) revealed that the removal efficiencies differed significantly from those of phytoremediation alone. With the same removal efficiency (100%), the biomass of sunn hemp in nano-phytoremediation treatments differed by approximately 55%, whereas the biomass of zinnia differed by >67%, compared with that of the control experiment. For marigold, the difference in biomass was only 30%. Styrene was adsorbed on surface of soil and AC and then further oxidized under air-water-nZVI environment, while phytovolatilization played an important role in transporting the remaining styrene from the contaminated soil to the air. Marigold was used as an alternative plant for the nano-phytoremediation of styrene-contaminated soil because of its sturdy nature, high biomass, tolerance to toxic effects, and ease of cultivation. Remediation of one cubic meter of styrene-contaminated soil by a combination of carbon-based nanoscale zero-valent iron and phytoremediation by marigolds emitted 0.0027 kgCO2/m3.