Zero-valent Iron Research Articles

Synergetic effect of green synthesized NZVI@Chitin-modified ZSM-5 for efficient oxidative degradation of tetracycline

The aggregation and limited activity of nanoscale zero-valent iron (NZVI) in aqueous media hinder its practical application. In this study, a cost-effective, environmentally friendly, robust, and efficient synthesis method for NZVI-based composite was developed. NZVI@Chitin-modified ZSM-5 (NZVI@C-ZSM) composite was facilely and greenly synthesized by loading NZVI into alkali-modified ZSM-5 molecular sieves after modifying with chitin as a surfactant and binder. NZVI@C-ZSM exhibited remarkable efficacy in TC removal, achieving a removal efficiency of 97.72% within 60 min. Compared with pristine NZVI, NZVI@C-ZSM demonstrated twice the removal efficiency, indicating that NZVI@C-ZSM effectively improved the dispersion and stability of NZVI. This enhancement provided more reactive sites for generating reactive oxygen species (ROS), significantly boosting catalytic activity and durability while reducing the potential risk of secondary pollution. An improved two-parameter pseudo-first-order kinetic model was used to effectively characterize the reaction kinetics. The mechanism for TC removal primarily involved an adsorption process and chemical oxidation-reduction reactions induced by hydroxyl radicals (•OH) and superoxide radicals (•O2−). Three potential degradation pathways for TC were suggested. Furthermore, NZVI@C-ZSM exhibited good resistance to interference, suggesting its broad potential for practical applications in complex environmental conditions. This study offers a viable material and method for addressing the issue of antibiotic-contaminated water, with potential applications in water resource management.

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

Mechanism of nano-scale zero-valent iron modified biochar for enhancing low-nitrogen anammox process resistance to low temperatures

Two anaerobic ammonia oxidation (anammox) systems, one with adding nano-scale zero-valent iron modified biochar (nZVI@BC) and the other with adding biochar, were constructed to explore the feasibility of nZVI@BC for enhancing the resistance of low-nitrogen anammox processes to low temperatures. The results showed that the average nitrogen removal efficiency with nZVI@BC addition at low temperatures was maintained at about 80%, while that with biochar addition gradually decreased to 69.49%. The heme-c content of biomass with nZVI@BC was significantly higher by 36.60%-91.45%. Additional, nZVI@BC addition resulted in more extracellular polymeric substances, better biomass granulation, and a higher abundance of anammox bacteria. In particularly, anammox genes hzsA/B/C, hzo and hdh played a pivotal role in maintaining nitrogen removal performance at 15°C. These findings suggest that nZVI@BC has the potential to enhance the resistance of low-nitrogen anammox processes to low temperatures, making it a valuable approach for practical applications in low-nitrogen and low-temperature wastewater treatment.

Facilely tuning the coating layers of Fe nanoparticles from iron carbide to iron nitride for different performance in Fenton-like reactions

In this study, a series of Fe-based materials are facilely synthesized using MIL-88A and melamine as precursors. Changing the mass ratio of melamine and MIL-88A could tune the coating layers of generated zero-valent iron (Fe0) particles from Fe3C to Fe3N facilely. Compared to Fe/Fe3N@NC sample, Fe/Fe3C@NC exhibits better catalytic activity and stability to degrade carbamazepine (CBZ) with peroxymonosulfate (PMS) as oxidant. Free radical quenching tests, open-circuit potential (OCP) test and electron paramagnetic resonance spectra (EPR) prove that hydroxyl radicals (OH) and superoxide radical (O2−) are dominant reactive oxygen species (ROSs) with Fe/Fe3C@NC sample. For Fe/Fe3N@NC sample, the main ROSs are changed into sulfate radicals (SO4−) and high valent iron-oxo (Fe (IV)=O) species. In addition, the better conductivity of Fe3C is beneficial for the electron transfer from Fe0 to the Fe3C, thus could keep the activity of the surface sites and obtain better stability. DFT calculation reveals the better adsorption and activation ability of Fe3C than Fe3N. Moreover, PMS can also be adsorbed on the Fe sites of Fe3N with shorter FeO bonds and longer SO bonds than on Fe3C, the Fe (IV)=O is thus present in the Fe/Fe3N@NC/PMS system. This study provides a novel strategy for the development of highly active Fe-based materials for Fenton-like reactions and thus could promote their real application.

Zero-valent iron-loaded Ti3C2-MXene activated by persulfate for the degradation of tetracycline hydrochloride: Efficiency and mechanism

The unique two-dimensional "sandwich" structure and excellent surface chemistry of Ti3C2-MXene show great potential for environmental treatment. In this paper, a novel degradant, Ti3C2-MXene was modified by zero-valent iron (Fe0) composites (Fe0/Ti3C2-MXene) were prepared, which could successfully degrade tetracycline hydrochloride (TC) under sodium persulfate (PDS) conditions. Characterization methods such as SEM, XRD, and XPS demonstrated that Fe0/Ti3C2-MXene still retained the two-dimensional layered structure of Ti3C2-MXene, and the Fe0 nanoparticles were successfully attached to the surface and interlayers of Ti3C2-MXene. Meanwhile, the effects of catalyst dosage, PDS dosage, initial concentration, pH, and coexisting anions and cations on the degradation were investigated. The results indicated that the degradation of TC (80 mL, 20 mg/L) by 2 mg of Fe0/Ti3C2-MXene and 10 mg of PDS under 25 °C and pH=4 could reach 80 % within 2 min. There is a synergistic effect of adsorption and oxidative degradation in the degradation of TC by Fe0/Ti3C2-MXene. SO4-• and 1O2 play a major role during TC degradation by the radical quenching experiments, XPS and LC-MS. This work not only provides a new strategy for the modification of Ti3C2-MXene with Fe0, but also offers new insights into the efficient degradation of antibiotics in water by Ti3C2-MXene.

Characteristic study of biological CaCO3-supported nanoscale zero-valent iron: stability and migration performance

ABSTRACT nZVI has attracted much attention in the remediation of contaminated soil and groundwater, but the application is limited due to its aggregation, poor stability, and weak migration performance. The biological CaCO3 was used as the carrier material to support nZVI and solved the nZVI agglomeration, which had the advantages of biological carbon fixation and green environmental protection. Meanwhile, the distribution of nZVI was characterised by SEM-EDS and TEM carefully. Subsequently, the dispersion stability of bare nZVI and CaCO3@nZVI composite was studied by the settlement experiment and Zeta potential. Sand column and elution experiments were conducted to study the migration performance of different materials in porous media, and the adhesion coefficient and maximum migration distances of different materials in sand columns were explored. SEM-EDS and TEM results showed that nZVI could be uniformly distributed on the surface of biological CaCO3. Compared with bare nZVI, CaCO3@nZVI composite suspension had better stability and higher absolute value of Zeta potential. The migration performance of nZVI was poor, while CaCO3@nZVI composite could penetrate the sand column and have good migration performance. What’s more, the elution rates of bare nZVI and CaCO3@nZVI composite in quartz sand columns were 5.8% and 51.6%, and the maximum migration distances were 0.193 and 0.885 m, respectively. In summary, this paper studies the stability and migration performance of bare nZVI and CaCO3@nZVI composite, providing the experimental and theoretical support for the application of CaCO3@nZVI composite, which is conducive to promoting the development of green remediation functional materials.

Use of Zero-Valent Iron Nanoparticles (nZVIs) from Environmentally Friendly Synthesis for the Removal of Dyes from Water—A Review

This review article addresses the increasing environmental concerns posed by synthetic dyes in water, exploring innovative approaches for their removal with a focus on zero-valent iron nanoparticles (nZVIs) synthesized through environmentally friendly methods. The article begins by highlighting the persistent nature of synthetic dyes and the limitations of conventional degradation processes. The role of nanoparticles in environmental applications is then discussed, covering diverse methods for metallic nanoparticle production aligned with green chemistry principles. Various methods, including the incorporation of secondary metals, surface coating, emulsification, fixed support, encapsulation, and electrostatic stabilization, are detailed in relation to the stabilization of nZVIs. A novel aspect is introduced in the use of plant extract or biomimetic approaches for chemical reduction during nZVI synthesis. The review investigates the specific challenges posed by dye pollution in wastewater from industrial sources, particularly in the context of garment coloring. Current approaches for dye removal in aqueous environments are discussed, with an emphasis on the effectiveness of green-synthesized nZVIs. The article concludes by offering insights into future perspectives and challenges in the field. The intricate landscape of environmentally friendly nZVI synthesis has been presented, showcasing its potential as a sustainable solution for addressing dye pollution in water.

Activation of peroxydisulfate by zero valent iron-carbon composites prepared by carbothermal reduction: Enhanced non-radical and radical synergies

Since its application in environmental remediation, nano zero-valent iron (nZVI) has gained wide attention for its environmental friendliness, strong reducing ability, and wide range of raw materials. However, its high preparation cost and difficulty in preservation remain the bottlenecks for their application. Carbothermal reduction is a promising method for the industrial preparation of nZVI. Micronized zero-valent iron/carbon materials (Fe0/CB) were produced in one step by co-pyrolysis of carbon and iron. The performance of the Fe0/CB is comparable to that of nZVI. In addition, Fe0/CB overcomed the disadvantages of agglomeration and oxidative deactivation of nZVI. Experiments on the Fenton-like reaction of its activated PDS showed that metronidazole (MNZ) was efficiently removed through the synergistic action of radicals and non-radicals, which were mainly superoxide radicals (·O2−), monoclinic oxygen (1O2), and high-valent iron (FeIVO). Moreover, the degradation process showed better generalization, making it suitable for a wide range of applications in the degradation of antibiotics.

Enhancing Biohydrogen Production: The Role of Iron-Based Nanoparticles in Continuous Lactate-Driven Dark Fermentation of Powdered Cheese Whey

Here, a comprehensive investigation was conducted under various operational strategies aimed at enhancing biohydrogen production via dark fermentation, with a specific focus on the lactate metabolic pathway, using powdered cheese whey as a substrate. Initially, a batch configuration was tested to determine both the maximum hydrogen yield (100.2 ± 4.2 NmL H2/g CODfed) and the substrate (total carbohydrates) consumption efficiency (94.4 ± 0.8%). Subsequently, a transition to continuous operation was made by testing five different operational phases: control (I), incorporation of an inert support medium for biomass fixation (II), addition of carbon-coated, zero-valent iron nanoparticles (CC-nZVI NPs) at 100 mg/L (III), and supplementation of Fe2O3 nanoparticles at concentrations of 100 mg/L (IV) and 300 mg/L (V). The results emphasized the critical role of the support medium in stabilizing the continuous system. On the other hand, a remarkable increase of 10% in hydrogen productivity was observed with the addition of Fe2O3 NPs (300 mg/L). The analysis of the organic acids’ composition unveiled a positive correlation between high butyrate concentrations and improved volumetric hydrogen production rates (25 L H2/L-d). Moreover, the presence of iron-based NPs effectively regulated the lactate concentration, maintaining it at low levels. Further exploration of the bacterial community dynamics revealed a mutually beneficial interaction between lactic acid bacteria (LAB) and hydrogen-producing bacteria (HPB) throughout the experimental process, with Prevotella, Clostridium, and Lactobacillus emerging as the predominant genera. In conclusion, this study highlighted the promising potential of nanoparticle addition as a tool for boosting biohydrogen productivity via lactate-driven dark fermentation.

Synergistic effect between biochar and sulfidized nano-sized zero-valent iron enhanced cadmium immobilization in a contaminated paddy soil

Biochar-based sulfidized nano-sized zero-valent iron (SNZVI/BC) can effectively immobilize cadmium (Cd) in contaminated paddy soils. However, the synergistic effects between biochar and SNZVI on Cd immobilization, as well as the underlying mechanisms remain unclear. Herein, a soil microcosm incubation experiment was performed to investigate the immobilization performance of SNZVI/BC towards Cd in the contaminated paddy soil. Results indicated that the addition of SNZVI/BC at a dosage of 3% significantly lessened the concentration of available Cd in the contaminated soil from 14.9 (without addition) to 9.9 mg kg−1 with an immobilization efficiency of 33.3%, indicating a synergistic effect. The sequential extraction results indicated that the proportion of the residual Cd in the contaminated soil increased from 8.1 to 10.3%, manifesting the transformation of the unstable Cd fractions to the steadier specie after application of SNZVI/BC. Also, the addition of SNZVI/BC increased soil pH, organic matter, and dissolved organic carbon, which significantly altered the bacterial community in the soil, enriching the relative abundances of functional microbes (e.g., Bacillus, Clostridium, and Desulfosporosinus). These functional microorganisms further facilitated the generation of ammonium, nitrate, and ferrous iron in the contaminated paddy soil, enhancing nutrients’ availability. The direct interaction between SNZVI/BC and Cd2+, the altered soil physicochemical properties, and the responded bacterial community played important roles in Cd immobilization in the contaminated soil. Overall, the biochar-based SNZVI is a promising candidate for the effective immobilization of Cd and the improvement of nutrients’ availability in the contaminated paddy soil.Graphical

Granular activated carbon supported polyethylene glycol modified nano-zero-valent iron immobilized microbial removal of 2,4-dichlorophenol in water

In recent years, the remediation of 2,4-DCP pollution using immobilized microbial technology has attracted increasing attention. Using granular activated carbon (GAC), polyethylene glycol 4000 (PEG-4000), ferrous sulfate, and sodium borohydride as raw materials, granular activated carbon loaded polyethylene glycol modified nano zero-valent iron composite material (PEG-nZVI/GAC) was prepared via a liquid-phase reduction method. Bacillus marisflavi, capable of degrading phenolic compounds, was immobilized on PEG-nZVI/GAC using an adsorption method to prepare immobilization of microorganisms by granular activated carbon loaded polyethylene glycol modified nano zero-valent iron (PEG-nZVI/GAC@B) for 2,4-DCP removal. Characterization analysis of immobilized microbes was conducted using transmission electron microscopy (TEM) and other methods to determine their physicochemical properties. Response surface methodology (RSM) was employed to optimize the conditions for 2,4-DCP removal, and the performance and mechanism of 2,4-DCP removal by PEG-nZVI/GAC@B were studied. The results indicate that nanoscale zero-valent iron (nZVI) was uniformly distributed in granular activated carbon, Bacillus marisflavi was successfully loaded onto PEG-nZVI/GAC, PEG-nZVI/GAC@B had a higher content of oxygen-containing groups on its surface, and exhibits good dispersibility, stability, and reusability. When the immobilized microbial dosage was 270.32 mg/L, the initial concentration of 2,4-DCP was 50.51 mg/L, and pH was 6.58, the predicted removal rate of 2,4-DCP was 96.53 %. Under these conditions, the actual removal rate of 2,4-DCP was 94.68 %. The removal of 2,4-DCP by PEG-nZVI/GAC@B involved adsorption by granular activated carbon, reductive dechlorination by nanoscale zero-valent iron, and degradation by Bacillus marisflavi. In conclusion, PEG-nZVI/GAC@B is an excellent immobilized microorganism for the removal of 2,4-DCP.

Continuous-flow columns packed with zero-valent iron and iron sulfide as a feasible strategy to remediate the persistent contaminant nitroguanidine

The insensitive munitions compound nitroguanidine (NQ) is used by the U.S. Army to avoid unintended explosions. However, NQ also represents an emerging contaminant whose environmental emissions can cause toxicity toward aquatic organisms, indicating the need for effective remediation strategies. Thus, we investigated the feasibility of treating water contaminated with NQ in continuous-flow columns packed with zero-valent iron (ZVI) or iron sulfide (FeS). Initially, the impact of pH on NQ transformation by ZVI or FeS was evaluated in batch experiments. The pseudo first-order rate constant for NQ transformation (k1, NQ) by ZVI was 8–10 times higher at pH 3.0 compared to pH 5.5 and 7.0, whereas similar k1, NQ values were obtained for FeS at pH 5.5–10.0. Based on these findings, the influent pH fed to the ZVI- and FeS-packed columns was adjusted to 3.0 and 5.5, respectively. Both reactors transformed NQ into nitrosoguanidine (NsoQ). Further transformation of NsoQ by ZVI produced aminoguanidine, guanidine, and cyanamide, whereas NsoQ transformation by FeS produced guanidine, ammonium, and traces of urea. ZVI outperformed FeS as a reactive material to remove NQ. The ZVI-packed column effectively removed NQ below detection even after 45 d of operation (490 pore volumes, PV). In contrast, NQ breakthrough (removal efficiency <85%) was observed after 18 d (180 PV) in the FeS-packed column. The high NQ removal efficiency and long service life of the ZVI-packed column (>490 PV) suggest that the technology is a promising approach for NQ treatment in packed-bed reactors and in situ remediation.

Application of greenly synthesised zero-valent iron nanoparticles for iron removal from aqueous system

Application of greenly synthesised zero-valent iron nanoparticles for iron removal from aqueous system

Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the PAC in-situ regeneration

Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the PAC in-situ regeneration

Occurrence and ecotoxicological impacts of polybrominated diphenyl ethers (PBDEs) in electronic waste (e-waste) in Africa: Options for sustainable and eco-friendly management strategies

Polybrominated diphenyl ethers (PBDEs) are persistent contaminants used as flame retardants in electronic products. PBDEs are contaminants of concern due to leaching and recalcitrance conferred by the stable and hydrophobic bromide residues. The near absence of legislatures and conscious initiatives to tackle the challenges of PBDEs in Africa has allowed for the indiscriminate use and consequent environmental degradation. Presently, the incidence, ecotoxicity, and remediation of PBDEs in Africa are poorly elucidated. Here, we present a position on the level of contamination, ecotoxicity, and management strategies for PBDEs with regard to Africa. Our review shows that Africa is inundated with PBDEs from the proliferation of e-waste due to factors like the increasing growth in the IT sector worsened by the procurement of second-hand gadgets. An evaluation of the fate of PBDEs in the African environment reveals that the environment is adequately contaminated, although reported in only a few countries like Nigeria and Ghana. Ultrasound-assisted extraction, microwave-assisted extraction, and Soxhlet extraction coupled with specific chromatographic techniques are used in the detection and quantification of PBDEs. Enormous exposure pathways in humans were highlighted with health implications. In terms of the removal of PBDEs, we found a gap in efforts in this direction, as not much success has been reported in Africa. However, we outline eco-friendly methods used elsewhere, including microbial degradation, zerovalent iron, supercritical fluid, and reduce, reuse, recycle, and recovery methods. The need for Africa to make and implement legislatures against PBDEs holds the key to reduced effect on the continent.

Improving antibiotic resistance removal from piggery wastewater by involving zero-valent iron within an integrated anoxic-aerobic biofilm reactor

This study introduces zero-valent iron (ZVI) to enhance the removal of antibiotic resistance in piggery wastewater. Two integrated anoxic-aerobic biofilm reactors (IAOBRs) were operated simultaneously for 120 days, with one serving as a control reactor and the other as experimental reactor supplemented with ZVI. The experimental reactor demonstrated superior antibiotic removal efficiencies (89.8 ± 4.5 %), eliminating 99.7 ± 0.7 % of sulfonamides, 91.6 ± 4.5 % of tetracyclines and 81.1 ± 8.4 % of quinolones. The antibiotic resistance bacteria, antibiotic resistance genes (ARGs) and mobile genetic elements removal efficiency reached 0.69–1.74, 2.06 and 2.15 logs, respectively. In comparison to the control reactor, the activated sludge in the experimental reactor also experienced a reduction in total antibiotic concentrations by 57.58 ± 19.99 %. The enhanced performance of the iron-mediated process in antibiotic resistance removal is attributed to the augmentation of enzymatic activity, biodegradation ability, and enrichment of specific microorganisms. The introduction of ZVI also modified the microbial community composition and decreased the potential hosts of ARGs. The proposed iron-mediated process greatly enhances antibiotic resistance removal from wastewater and mitigates antibiotic accumulation in activated sludge, offering new insights into wastewater biological treatment for eliminating antibiotic resistance.

Chemical and biological effects of zero-valent iron (ZVI) concentration on in-situ production of H2 from ZVI and bioconversion of CO2 into CH4 under anaerobic conditions

The conversion of carbon dioxide (CO2) to methane (CH4) is a strategy for sequestering CO2. Zero-valent iron (ZVI) has been proposed as an alternative electron donor for the CO2 reduction to CH4. In this study, the effects of ZVI concentrations on the abiotic production of H2 (without the action of microorganisms) in the first part and on the biological conversion of CO2 to CH4 using ZVI as a direct electron donor in the second part were examined. In the abiotic H2 production, the increase in the ZVI concentration from 16 to 32, 64, and 96 g/L was found to have positive effects on both the amounts of H2 generated and the rates of H2 production because the extent of ZVI oxidation positively correlates with increasing surface area. Nevertheless, the increase in ZVI concentration from 96 to 224 g/L did not benefit the H2 production because the ZVI dissolution was suppressed by the increasing aqueous pH above 10. In the bioconversion of CO2 to CH4 using ZVI as an electron donor, the main methanogenesis pathway occurred via hydrogenotrophic methanogenesis at pH 8.7–9.5 driven by the genus Methanobacterium of the class Methanobacteria. At ZVI concentrations of 64 g/L and above, the production of volatile fatty acid (VFA) became clear. Acetate was the main VFA, indicating the induction of homoacetogenesis at ZVI concentrations of 64 g/L and above. In addition, the presence of propionate as the second major VFA suggests the production of propionate from CO2 and acetate under conditions with high H2 partial pressure. The results indicated that the pathway for ZVI/CO2 conversion to CH4 was competitive between hydrogenotrophic methanogenesis and homoacetogenesis.

Surface Modification of Polyurethane Sponge with Zeolite and Zero-Valent Iron Promotes Short-Cut Nitrification.

Partial nitrification-Anammox (PN-A) is a cost-effective, environmentally friendly, and efficient method for removing ammonia (NH4+-N) pollutants from water. However, the limited accumulation of nitrite (NO2--N) represents a bottleneck in the development of PN-A processes. To address this issue, this study developed a composite carrier loaded with nano zero-valent iron (nZVI) and zeolite to enhance NO2--N accumulation during short-cut nitrification. The modified composite carrier revealed electropositive, hydrophilicity, and surface roughness. These surface characteristics correlate positively with the carrier's total biomass adsorption capacity; the initial adsorption of microorganisms by the composite carrier was increased by 8.7 times. Zeolite endows the carrier with an NH4+-N adsorption capacity of 4.50 mg/g carrier. The entropy-driven ammonia adsorption process creates an ammonia-rich microenvironment on the surface of the carrier, providing effective inhibition of nitrite-oxidizing bacteria (NOB). In tests conducted with a moving bed biofilm reactor and a sequencing batch reactor, the composite carrier achieved a 95% NH4+-N removal efficiency, a NO2--N accumulation efficiency of 78%, and a doubling in total nitrogen removal efficiency. This composite carrier enhances NO2--N accumulation by preventing biomass washout, inhibiting NOB, and enriching PN-A functional bacteria, suggesting its potential for large-scale, stable PN-A applications.

Controllable integration of nano zero-valent iron into MOFs with different structures for the purification of hexavalent chromium-contaminated water: Combined insights of scavenging performance and potential mechanism investigations

This work combined the stability of the porous structure of metal-organic frameworks with the strong reducibility of nano zero-valent iron, for the controllable integration of NZVI into MOFs to utilize the advantages of each component with enhancing the rapid decontamination and scavenging of Cr(VI) from wastewater. Hence, four kinds of MOFs/NZVI composites namely ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, were prepared for Cr(VI) capture. The results indicated that the stable structure of ZIF67, MOF74, MIL101(Fe), CuBTC, was beneficial for the dispersion of NZVI that could help more close contact between MOFs/NZVI reactive sites and Cr(VI), subsequently, MOFs/NZVI was proved to be better scavengers for Cr(VI) scavenging than NZVI alone. The Cr(VI) capture achieved the maximum adsorption capacity at pH ~ 4.0, which might be due to the participation of more H+ in the reaction and better corrosion of NZVI at lower pH. Mechanism investigation demonstrated synergy of adsorption, reduction and surface precipitation resulted in enhanced Cr(VI) scavenging, and Fe(0), dissolved and surface-bound Fe(II) were the primary reducing species. The findings of this investigation indicated that the as-prepared composites of ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, with high oxidation resistance and excellent reactivity, could provide reference for the decontamination and purification of actual Cr(VI)-containing wastewater.

Retraction: Combination effect of cold atmospheric plasma with green synthesized zero-valent iron nanoparticles in the treatment of melanoma cancer model.

Retraction: Combination effect of cold atmospheric plasma with green synthesized zero-valent iron nanoparticles in the treatment of melanoma cancer model.