Zero-valent Iron Nanoparticles Research Articles

Zero-Valent Iron Nanoparticles: Biogenic Synthesis and their Medical Applications; Existing Challenges and Future Prospects.

In the last decade, nanobiotechnology is emerging as a keen prudence area owing to its widespread applications in the medical field. In this context, zero-valent iron nanoparticles (nZVI) have garnered tremendous attention attributed to their cheap, non-toxic, excellent paramagnetic nature, extremely reactive surface, and dual oxidation state that makes them excellent antioxidants and free-radical scavengers. Facile biogenic synthesis, in which a biological source is used as a template for the synthesis of NPs, is presumably dominant among other physical and chemical synthetic procedures. The purpose of this review is to elucidate plant-mediated synthesis of nZVI, although they have been successfully fabricated by microbes and other biological entities (such as starch, chitosan, alginate, cashew nut shell, etc.) as well. The methodology of the study involved keyword searches of electronic databases, including ScienceDirect, NCBI, and Google Scholar (2008-2023). Search terms of the review included 'biogenic synthesis of nZVI', 'plant-mediated synthesis of nZVI', 'medical applications of nZVI', and 'Recent advancements and future prospects of nZVI'. Various articles were identified and reviewed for biogenic fabrication of stable nZVI with the vast majority of studies reporting positive findings. The resultant nanomaterial found great interest for biomedical purposes such as their use as biocompatible anticancer, antimicrobial, antioxidant, and albumin binding agents that have not been adequately accessed in previous studies. This review shows that there are potential cost savings applications to be made when using biogenic nZVI for medical purposes. However, the encountering challenges concluded later, along with the prospects for sustainable future development.

Removal of Cu(II) by sodium hexametaphosphate and nano zero-valent iron modified calcium bentonite: characteristic, adsorption performance and mechanism

Cu (II) is a toxic heavy metal commonly identified in groundwater contaminants. Bentonite-based cutoff wall is the most used method in isolating and adsorbing contaminants, while the bentonite in it easily to fail due to Cu(II) exchange. This study synthesized a novel material through the modification of calcium bentonite (CaB) utilizing sodium hexametaphosphate (SHMP) and nano zero-valent iron (NZVI). The characteristics, adsorption performance, and mechanism of the NZVI/SHMP-CaB were investigated comprehensively. The results showed that SHMP can disperse CaB and reduce flocculation, while NZVI can be further stabilized without agglomeration. The best adsorption performance of NZVI/SHMP-CaB could be obtained at the dosage of 2% SHMP and 4% NZVI. The NZVI/SHMP-CaB exhibited an outstanding removal efficiency of over 60% and 90% at a high Cu(II) concentration (pH = 6, Cu(II) = 300 mg/L) and acidic conditions (pH = 3–6, Cu(II) = 50 mg/L), respectively. The adsorption of Cu(II) by NZVI/SHMP-CaB followed a pseudo-second-order kinetic model, and fitting results from the Freundlich isothermal model suggested that the adsorption process occurred spontaneously. Besides the rapid surface adsorption on the NZVI/SHMP-CaB and ion exchange with interlayer ions in bentonite, the removal mechanism of Cu(II) also involved the chemical reduction to insoluble forms such as Cu0 and Cu2O. The generated FePO4 covered the surface of the homogenized NZVI particles, enhancing the resistance of NZVI/SHMP-CaB to acidic and oxidative environments. This study indicates that NZVI/SHMP-CaB is a promising alternative material which can be used for heavy metal removal from contaminated soil and water.

Efficient and low-cost mesoporous magnetic carbon composites derived from date palm stones for environmental remediation of hexavalent chromium

AbstractThis study was performed to achieve two important scientifically challenging goals, environmental remediation of toxic heavy metals and utilization of agricultural lignocellulosic wastes. In this work, a series of mesoporous magnetic carbon (MMC) adsorbents were synthesized by carbothermic reduction at different temperatures employing date palm (Phoenix dactylifera L.) stones as the carbon source. The synthesized adsorbents were characterized by different technquies and the results confirmed the presence of zero-valent iron (ZVI) nanoparticles and other iron oxides as products of the carbothermal reduction. The nature of phases present, crystallite size and the surface properties were found to be dependent on the calcination temperature. The adsorbent MMC700 exhibited the smallest (ZVI) crystallite size 36 nm and the largest SBET 341 m2/g. All adsorbents showed mesoporous structure with mesopore average diameter lower than 6 nm. The performance was evaluated in the removal process of toxic Cr(VI) in an aqueous medium, and the optimum conditions of the process were reported. The removal process was dependant of solution pH where best results was achieved at pH = 2. Complete removal of chromium was achieved in less than 5 min by MMC700. The results were better fitted with pseudo-second-order kinetics and followed the Freundlich model isotherm. The maximum adsorption capacity was found to be 265.25 mg/g for MMC700, suggesting its application as an efficient, low-cost, and easily separable adsorbent for the toxic Cr(VI) removal process. The prepared adsorbents exhibited superior performance in the removal process compared to other agricultural wastes or biomass - derived adsorbents reported in literature.

Equilibrium and kinetic modeling of Cr(VI) removal by novel tolerant bacteria species along with zero-valent iron nanoparticles

This work describes the study of the removal of a refractory contaminant, i.e., Hexavalent chromium (Cr(VI)) from aqueous systems by a novel adsorbent comprising Cr(VI) tolerant bacteria and zero valent iron nanoparticle (nZVI). A gram-positive, rod-shaped bacteria used in the study were isolated from wastewater (WW) received from the effluent of leather industries. The adsorbents were prepared with bacteria, nZVI alone, and a combination of both. The adsorbent comprising both elements was found to remove Cr(VI) with a higher percentage (93%) and higher capacities (0.58 mg/g) as compared to adsorbent with bacteria (Cr(VI) removal = 63%, qe = 0.163 mg/g) or nanoparticles (Cr(VI) removal = 80%, qe = 0.45 mg/g) alone. The adsorbent worked best at neutral pH, and the removal became saturated after 90 min of incubation. Equilibrium studies with isotherm modeling suggested that the adsorption process follows sips isotherm (R2 = 0.9955), which is expected to bean intra-particle diffusion process before the actual adsorption. Process kinetics was modeled with pseudo-first order, pseudo-second order, and Vermeulen model. The diffusion coefficient determined by fitting the kinetic data to Vermeulen model was found to be 0.0000314 cm2/s. The adsorbent can be tested further for continuous flow processes to find more insights about the usage on a large scale.

Architecture dependent transport behavior of iron (0) entrapped biodegradable polymeric particles for groundwater remediation

Polylactic acid based spherical particles with three architectural variations (Isotropic (P1), Semi porous (P2), and Janus (P3)) were employed to encapsulate zero valent iron nanoparticles (ZVINPs), and their performance was extensively evaluated in our previous studies. However, little was known about their transportability through saturated porous media of varying grain size kept under varying ionic strength. In this particular study, we aimed to investigate the architectural effect of polymeric particles (P1–P3) on their mobility through the sand column of varying grain size in presence of mono, di, and tri-valent ions of varying concentrations (25–200 mM (millimoles)). As per column breakthrough experiments (BTCs) using various types of sands, amphiphilic Janus type (P3) particles exhibited the maximum transportability among all the tested particles, irrespective of the nature of the sand. Owing to the narrower travel path, sands with lower porosity (31%) delayed the plateau by shifting it to a higher pore volume with a minimum retention of iron (C/Co: 0.94 for P3) in the column. The impact of mono (Na+, K+), di (Ca2+, Mg2+), and trivalent (Al3+) ions on their transportability was progressively increased from P3 to P1, especially at higher ionic concentrations (200 mM), with P3 being the most mobile particles (C/Co:0.54 for Al3+). Among all the ions, Al3+ exhibited maximum hindrance to their mobility through the sand column. This could be due to their strong charge screening effect coupled with cation bridging complex formation with moving particles. Experimental results obtained from BTCs were found to be well-fitted with a theoretical model based on advection-dispersion equation, showing minimum retention for P3 particles. Overall, it can be inferred that encapsulation of ZVINPs inside Janus particles (P3) with a right balance of amphiphilicity and highly negative surface charge would be required to achieve considerable transportability through sand aquifers to target contaminants in polluted groundwater existing under harsh conditions (high ionic concentrations).

Iron scrap derived nano zero-valent iron/biochar activated persulfate for p-arsanilic acid decontamination with coexisting microplastics

P-arsanilic acid (AA) has received widespread attention because of its conversion to more toxic inorganic arsenic compounds (arsenate and arsenite) in the natural ecosystems. Its removal process and mechanisms with co-existence of microplastics remain unkown. In this study, biochar loaded with nano zero-valent iron (nZVI) particles (ISBC) was prepared by using iron scrap obtained from a steel works and wood chips collected from a wood processing plant. The advanced oxidation system of sodium persulfate (PDS) activated by ISBC was applied for AA degradation and inorganic arsenic control in aqueous media. More than 99% of the AA was completely degraded by the ISBC/PDS system, and the As(III) on AA was almost completely oxidized to As(V) and finally removed by ISBC. HCO3− inhibited the removal of AA by the ISBC/PDS system, while Cl− had a dual effect that showing inhibition at low concentrations yet promotion at high concentrations. The effect of microplastics on the degradation of AA by the ISBC/PDS system was further investigated due to the potential for combined microplastic and organic arsenic contamination in rural/remote areas. Microplastics were found to have little effect on AA degradation in the ISBC/PDS system, while affect the transport of inorganic arsenic generated from AA degradation. Overall, this study provides new insights and methods for efficient removal of p-arsanilic acid from water with coexisting microplastics.

Deciphering the corrosion puzzle: Nano-iron-biochar composite – Not a quick fix for metal immobilization in peat soils

The use of zero-valent iron nanoparticles in the remediation of metal-contaminated soils has received considerable attention. Upon introduction into the soil, zero-valent iron particles corrode into iron oxides, known for their high adsorption capacity for potentially toxic metals. While limited research has directly compared zero-valent iron micro- and nanoparticles, it is important to investigate whether particle size contributes to effective soil remediation. This study focuses on elucidating the comparative kinetics of iron corrosion using iron powder and a nano-iron-biochar composite. In a model experiment, these materials were exposed to a cellulose/biochar mixture and peat for five months. Mössbauer spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy with electron diffraction were used to analyze the corrosion products. The results show a slow corrosion rate in the nano-iron-biochar composite in cellulose due to the protective effect of biochar on the embedded iron nanoparticles. In addition, iron corrosion in peat was inhibited, likely due to the presence of humic substances. Transmission electron microscopy after five months of corrosion revealed round metal particles encased in a graphite capsule with visible channels. Large dissolved organic matter molecules in the peat likely block these channels, inhibiting metallic iron corrosion. Consequently, the nano-iron-biochar composite emerges as a slow-reacting option for immobilizing soil metals in peat. This study highlights the need for further research involving long-term field experiments.

Facilitating effects of the synergy with zero-valent iron and peroxysulfate on the sludge anaerobic fermentation system: Combined biological enzyme, microbial community and fermentation mechanism assessment

This study evaluated a synergetic waste activated sludge treatment strategy with environmentally friendly zero-valent iron nanoparticles (Fe0) and peroxysulfate. To verify the feasibility of the synergistic treatment, Fe0, peroxysulfate, and the mixture of peroxysulfate and Fe0 (synergy treatment) were added to different sludge fermentation systems. The study demonstrated that the synergy treatment fermentation system displayed remarkable hydrolysis performance with 435.50 mg COD/L of protein and 197.67 mg COD/L of polysaccharide, which increased 1.13–2.85 times (protein) and 1.12–1.49 times (polysaccharide) for other three fermentation system. Additionally, the synergy treatment fermentation system (754.52 mg COD/L) exhibited a well acidification performance which was 1.35–41.73 times for other systems (18.08–557.27 mg COD/L). The synergy treatment fermentation system had a facilitating effect on the activity of protease, dehydrogenase, and alkaline phosphatase, which guaranteed the transformation of organic matter. Results also indicated that Comamonas, Soehngenia, Pseudomonas, and Fusibacter were enriched in synergy treatment, which was beneficial to produce SCFAs. The activation of Fe0 on peroxysulfate promoting electron transfer, improving the active groups, and increasing the enrichment of functional microorganisms showed the advanced nature of synergy treatment. These results proved the feasibility of synergy treatment with Fe0 and peroxysulfate to enhance waste activated sludge anaerobic fermentation.

Impact of Zero-Valent Iron Nanoparticles and Ampicillin on Adenosine Triphosphate and Lactate Metabolism in the Cyanobacterium Fremyella diplosiphon.

In cyanobacteria, the interplay of ATP and lactate dynamics underpins cellular energetics; their pronounced shifts in response to zero-valent iron (nZVI) nanoparticles and ampicillin highlight the nuanced metabolic adaptations to environmental challenges. In this study, we investigated the impact of nZVIs and ampicillin on Fremyella diplosiphon cellular energetics as determined by adenosine triphosphate (ATP) content, intracellular and extracellular lactate levels, and their impact on cell morphology as visualized by transmission electron microscopy. While a significant increase in ATP concentration was observed in 0.8 mg/L ampicillin-treated cells compared to the untreated control, a significant decline was noted in cells treated with 3.2 mg/L nZVIs. ATP levels in the combination regimen of 0.8 mg/L ampicillin and 3.2 mg/L nZVIs were significantly elevated (p < 0.05) compared to the 3.2 mg/L nZVI treatment. Intracellular and extracellular lactate levels were significantly higher in 0.8 mg/L ampicillin, 3.2 mg/L nZVIs, and the combination regimen compared to the untreated control; however, extracellular lactate levels were the highest in cells treated with 3.2 mg/L nZVIs. Visualization of morphological changes indicated increased thylakoid membrane stacks and inter-thylakoidal distances in 3.2 mg/L nZVI-treated cells. Our findings demonstrate a complex interplay of nanoparticle and antibiotic-induced responses, highlighting the differential impact of these stressors on F. diplosiphon metabolism and cellular integrity.

Biogenic preparation of zero-valent iron nanoparticles and evaluation of anti-cancer effect and heavy metal removal

In this research, a new environmentally friendly protocol for manufacturing of zero iron nanoparticles (Fe(0) NPs) using herbal tea flowers was proposed. The transmission electron microscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analyses were used to characterize the crystal structure and morphology of the fabricated Fe(0) NPs. The prepared Fe(0) NPs were exerted for adsorptive uptake of Pb(II) from aqueous medium. The investigation of equilibrium data involved the examination of Langmuir and Freundlich isotherms. The Pb(II) adsorption closely aligned with the Langmuir adsorption isotherm. The estimated maximum adsorption capacity for Pb(II) was 46.5 mg/g. To assess the removal process kinetics, pseudo-first-order and pseudo-second-order equations were utilized. Among these, the pseudo-second-order equation demonstrated the optimal fit, indicating that the removing of heavy metal associated with by chemisorption. The study also investigated the cytotoxic effect of the as-prepared Fe(0) NPs on the common fibroblast cancer cell line (HSkMC). The MTT assay investigations on cell viability demonstrated that the bio-synthesized Fe(0) NPs exhibited notable cytotoxicity versus fibroblast cancer in humans. The Fe(0) NPs prepared in this work have proven to be effective in the fields of heavy metal removal and cancer treatment.

Sulfidation of nano-Fe/Pd bimetal for highly efficient remediation of Cr (VI) from water: Enhanced reactivity and applicability

Sulfidation of zero-valent iron nanoparticles (S-nZVI) has been considered as a common means to improve its reactivity. In this paper, Pd and Na2S were chosen as the catalyst and sulfidation regent via a modified post sulfidation approach to fabricate a kind of sulfidated bimetallic Fe/Pd nanoparticles (S-nZVIPd). The structure and composition have been clearly confirmed by a combination of various techniques. Morphology analysis showed that S-nZVIPd had a core–shell framework and hierarchical structure. The reactivity performance of S-nZVIPd, nZVIPd and S-nZVI toward Cr (VI) remediation from aqueous solution was compared, and the underlying mechanisms for the improvement effect of Cr (VI) removal were also investigated. S-nZVIPd exhibited a superior remediation reaction to remove Cr (VI) with higher removal capacity of 234.9 mg/g, with the comparison of nZVIPd (192.3 mg/g) and S-nZVI (137.5 mg/g). Additionally, the effects of common anions and cations, pH, and temperature on Cr (VI) removal were also investigated in batch experiments. Also, kinetic fitting of results revealed that remediation obeyed a pseudo-second-order model, where the apparent activation energy was 37.7 KJ/mol, illustrating that the removal of Cr (VI) was mainly dominated by chemical reduction. The enhanced removal rate of Cr (VI) by S-nZVIPd suggested that Pd and FeSx played a dual role in accelerating the corrosion of nZVI, and were facilitated to electron transfer between nZVI and Cr (VI). The results indicated that the research of the novel S-nZVIPd composite delivered new ideas theoretically for specific inquiries in the future.

Hexavalent chromium ion removal from wastewater using novel nanocomposite based on the impregnation of zero-valent iron nanoparticles into polyurethane foam

In this study, we developed a novel nanocomposite, polyurethane foam impregnated with zero-valent iron nanoparticles (PU@nZVI), for the effective removal of chromium(VI) from various water sources. The characterization of nanocomposite (PU@nZVI) was performed by XRD, SEM–EDS, TEM and FT-IR techniques. Using the response surface methodology, we optimized the removal conditions, achieving an optimal pH of 2 and a dose of 0.5 g/L. The PU@nZVI demonstrated an excellent maximum adsorption capacity of 600.0 mg/g for Cr6+. The adsorption kinetics and isotherms were best described by the pseudo-second-order model and the Freundlich isotherm, respectively. Significantly, the nanocomposite removed 99.98% of Cr6+ from tap water, 96.81% from industrial effluent, and 94.57% from treated sewage wastewater. Furthermore, the PU@nZVI maintained its efficiency over five adsorption–desorption cycles, highlighting its reusability. These results suggest that the PU@nZVI nanocomposite is a highly efficient and sustainable option for chromium(VI) removal in water treatment applications.

Comparative Environmental and Economic Analysis of Biomethane Production from Co-Digestion of Rice Straw and Spent Mushroom Compost: Application of Zero-Valent Iron Nanoparticles

Abstract Spent mushroom compost is one of the main potentials for biogas production. In recent years, several studies employed adding nanoparticles and alkaline pretreatment for improving biogas production. The present study is one of the pioneer studies that employ hybrid alkaline pretreatment (0, 5, and 15 mg of NaOH) and zero-valent iron nanoparticles (0, 10, 20, 30, and 40 mg) for improving the co-digestion of spent mushroom compost and rice straw. According to the results, retention time (RT) and nanoparticle (NP) concentrations have the most significant impact on biomethane production (significant at 1% probability level), while the NaOH concentration has the lowest impact on biomethane production (significant at 5% probability level) in comparison with RT and NP concentration. Also, the maximum biomethane production is related to NP40Na15 (about 200% higher than the control). The minimum cumulative biomethane production is related to NP0Na15 (about 30% lower than the control). The lowest relative environmental midpoint impact is related to NP40Na15, which was on average about 60% lower than the control. Adding NPs at high concentrations of NaOH reduces the midpoint impacts. The results of the study could lead to new, ecologically friendly biomethane production methods that make better use of agricultural and organic wastes.

Integrated approaches for heavy metal-contaminated soil remediation: harnessing the potential of Paulownia elongata S. Y. Hu, Oscillatoria sp., arbuscular mycorrhizal fungi (Glomus mosseae and Glomus intraradices), and iron nanoparticles.

In recent years, researchers have extensively investigated the remediation of heavy metal-contaminated soil using plants, microorganisms, and iron nanoparticles. The objective of this study was to investigate and compare the individual and simultaneous effects of Paulownia elongata S. Y. Hu, cyanobacteria (Oscillatoria sp.), arbuscular mycorrhizal fungi (AMF) including Glomus mosseae and Glomus intraradices, and zero-valent iron nanoparticles (nZVI) on the remediation of heavy metal-contaminated soil containing chromium (Cr VI and Cr III) and nickel (Ni). The study found significant variations in parameters such as pH (acidity), electrical conductivity (EC), nitrogen (N), phosphorus (P), potassium (K), and organic carbon (OC) among different treatments. The addition of cyanobacteria, AMF, and nZVI influenced these properties, resulting in both increases and decreases compared to the control treatment. The treatment involving a combination of cyanobacteria, AMF, and nZVI (CCAN25) exhibited the highest increase in growth parameters, such as total dry mass, root length, stem diameter, and leaf area, while other treatments showed varied effects on plant growth. Moreover, the CCAN25 treatment demonstrated the highest increase in chlorophyll a, chlorophyll b, and carotenoid levels, whereas other treatments displayed reductions in these pigments compared to the control. Moderate phytoaccumulation of Cr and Ni in P. elongata samples across all treatments was observed, as indicated by the bioconcentration factor and bioaccumulation coefficient values being less than 1.0 for both metals. The findings provide insights into the potential application of these treatments for soil remediation and plant growth enhancement in contaminated environments.

Removal of pollutants from landfill leachate by adsorption with nano zero-valent iron particles: adsorption isotherms and kinetic studies

Abstract Nano zero-valent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles, synthesized in our previous work, were used for landfill leachate pretreatment. The adsorption performance was tested at various adsorbent concentrations (50–500 mg Fe0/L), pH (3–8), and contact times (15–330 min). Chemical oxygen demand, dissolved organic carbon (DOC), nitrate (NO3-), and ammonium (NH4+) removal efficiency were approximately 75%, 60, 57, and 33%, respectively. The obtained data were fitted well by the Langmuir isotherm and adsorption kinetics of pseudo-second-order equations (R2 &amp;gt; 0.9). The adsorption capacities were found to be 29.62, 21.01, and 3.12 mg/g for DOC, NH4+, and NO3−, respectively, at Fe0 concentration of 50 mg Fe0/L, pH of 8, and contact time of 120 min, which was determined as the effective operational conditions in this work. The obtained removal levels were higher compared to the conventional activated carbon adsorption (72.3%). Results suggest that nZVI has the potential to create effective adsorption relevant to landfill leachate pretreatment, thereby providing more efficient biological treatment by decreasing important pollutants before biological treatment.

Development of an adsorption-enhanced heterogeneous Fenton process for abatement of natural organic matter by kaolin-supported phytogenic nanoscale zero-valent iron

Abstract Natural organic matter (NOM) serves as a precursor for the formation of carcinogenic disinfection by-products when not adequately removed by conventional water treatment processes. The degradation of NOM by heterogeneous Fenton processes is particularly attractive because it results in prospects of zero sludge discharge. This work reports on NOM degradation and adsorption via the heterogeneous Fenton process using phytogenic zero-valent iron nanoparticles (nZVI) synthesised from green tea extract (Camellia sinensis) and supported on kaolin (fK-nZVI). The synthesised material was characterised using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) analysis. Morphological analysis of SEM images and BET values revealed an increase in the surface area from 11.64 m2 · g−1 for kaolin to 27.07 m2 · g−1 for the kaolin-supported nZVI (K-nZVI), thus presenting an ideal modification for effective adsorption. Fenton process parameters were optimised, that is, H2O2 concentration (5 mM) and pH (4.5). At equilibrium, the adsorption by the fK-nZVI system was 0.127 mg · g−1, a value higher than reported in other adsorption systems at equivalent adsorbent dosage and NOM concentration. The promising results obtained in this study indicate heterogeneous Fenton degradation and adsorption can be a viable and effective method for NOM removal from aqueous media.

Influence of zero-valent iron nanoparticles on anaerobic digestion of swine manure: effects on methane yield

ABSTRACT This study evaluated the effect of zero-valent iron nanoparticles (NZVI) on the anaerobic digestion of swine manure. A wide range of doses of NZVI was evaluated (5, 10, 15, 20, 25, 50, and 100 mgFe°/gVS). The maximum methane yield of 0.4506 L/gVSremoved was obtained with the concentration of 10 mgFe°/gVS representing an increase of 58.99% than the control system with 0.2834 L/gVSremoved, indicating that Fe° improves the methanogenic activity. However, when using doses greater than 20 mgFe°/gVS, there were decreases in the methane yield of 34.4–47.98%. Also, to observe the effect of NZVI in anaerobes was evaluated the activity in the electron transport system (ETS), where the control reactor showed an activity of 31.91 μg INTred/gVS•h, while in reactors with NZVI showed values of 39.48 μg INTred/gVS•h (10 Fe°mg/gVS), observing a stimulation of Fe° in microbial activity. However, the dose of 100 mgFe°/gVS showed the greatest decrease in methane yield (0.1474 L/gVSremoved) and a reduction in ETS was observed by 8.5% compared to the control. The effect on the composition of the volatile fatty acids was observed, where the control system obtained a maximum production of acetic acid of 639 mg/L, which was exceeded with the dose of 10 mg Fe°/gVS by 215% and a decrease of 41.15% with the inhibitory concentration of 100 mg Fe°/gVS. As a result, higher doses of NZVI affect the metabolic activity of anaerobes as well as the acetoclastic pathway causing a decrease in the methane production.

Pesticide abatement using environmentally friendly nano zero valent particles as photo-Fenton catalyst

Nano-zero valent iron particles (NZVI) have been used for the pesticide pirimicarb degradation under simulated solar radiation. These particles have been synthesized by extracts from agro-industrial residues, namely vineyard and blueberry pruning, black tea and algae, so they can be labelled as “green-NZVI”. The physico-chemical properties of these green-NZVI were compared to those of NZVI synthesized with NaBH4. The usage of agro-industrial residues as reducing agent not only provided better performant NZVI but also evade the usage of harmful reagents. Indeed, this process is not only within circular economy, and environmentally friendly, but also defeats the degradation performance of the widely reported photo-Fenton process with Fe2+ catalyst. 96.5 % pirimicarb degradation was achieved under simulated solar radiation within 15 min with 0.08 mM H2O2 and 0.16 mM NZVI synthesized with black tea extract. Further, the developed process was optimized in terms of reagents concentration and natural antioxidant extract used for NZVI synthesis, which demonstrated a strong effect on pirimicarb degradation due to the differences on natural phenolic compounds present on them. The pirimicarb degradation pathway was analysed, confirming the successful pesticide degradation. In terms of H2O2 concentration, it can be reduced by its sequential addition in time. Under optimal conditions, even real effluents can be successfully degraded.

A combined experimental and DFT study on the zero valent iron/reduced graphene oxide doped QCM sensor for determination of trace concentrations of As using a Flow-batch system

A sensor based on a gold Quartz Crystal Microbalance (QCM) modified with nanoscale zero-valent iron nanoparticles (nZVI) anchored to reduced graphene oxide (rGO) was developed. An automated measurement microsystem was employed using QCM (modified and unmodified) as an arsine detector device. The QCM measurements of frequency changes are associated with total As concentration (III/V) in the samples. The gold surface QCM modification with nZVI/rGO improved the sensitivity in total As determination. The limit of detection (LOD) was 0.0062 ng mL−1 for QCM-Au/nZVI/rGO, 100 times higher than the unmodified QCM-Au sensor. Moreover, studies of adsorption energy and electron density of As with QCM-Au/nZVI/rGO and QCM-Au systems were performed. For this purpose, Density Functional Theory (DFT) methodology was used employing arsine adsorption on magnetite nanoparticles supported on graphene, and also on Au as models. This theoretical-experimental research allows us to acquire knowledge of the interaction of Au/nZVI/rGO with As and confirms the experimental results.

Biosynthesis of Iron Nanoparticles from Spinacia Oleracea and its Application in Wastewater Treatment

Water quality and purification issues may be resolved with the aid of "nanotechnology." Due to their prompt responsiveness and effectiveness in eradicating contaminants, along with their capacity to tackle groundwater issues by implementing a permeable reactive barrier utilizing zero-valent iron, zero-valent iron nanoparticles find extensive application in environmental remediation. These nanoparticles, containing zero-valent iron, were produced by synthesizing a metal salt solution with an extract obtained from Spinacia oleracea leaves. In this current study, the plant extract was mixed with a metal salt solution at a predetermined ratio to generate zero-valent iron nanoparticles (FeNP) either at room temperature or via the hydrothermal method. Phase-contrast microscopy and UV-visible spectroscopy were employed to scrutinize the nanoparticles generated. To our knowledge, this study represents the initial exploration of the efficacy of zero-valent iron nanoparticles derived from Spinacia oleracea leaf extract for treating municipal wastewater. The focus is particularly on assessing their impact on BOD and COD parameters.