Search Results (55)

Synthetic dyes are commonly present in industrial wastewater and when discharged in water bodies without receiving a treatment capable of removing or destroying them, they turn into concerning water pollutants. These organic contaminants threaten living beings due to their toxicity, and some of them can even damage DNA. Consequently, in order to achieve sustainable development, it is necessary to develop eco-friendly tools that can efficiently manage this kind of pollution. In the present study the aqueous extract from the leaves of Leucaena leucocephala (an invasive plant species native to Mexico) was used to produce green nano zero-valent iron (nZVI). The nanomaterial was characterized (TEM, UV–vis, FTIR, SEM, EDS, XRD) and assayed regarding its antioxidant potential (DPPH test) and capacity to remediate the pollution caused by two dyes. It proved to be able to adsorb nigrosine (288.30 mg/g of nanomaterial) and tartrazine (342.50 mg/g of nanomaterial), and also displayed antioxidant activity (effective concentration to discolor 50% of the DPPH solution = 286.02 μg/mL). Therefore, the biogenic antioxidant nanoparticle proved also to be a possible nanotool to be applied to remediate water contamination caused by these synthetic dyes. Full article

Zero-valent iron (ZVI), particularly in its nanoscale form (nZVI), is now considered a highly promising material for the remediation of toxic metal ions from polluted groundwater owing to its strong reductive potential, significant surface area, and reactive behavior. This review systematically explores the application of pristine and modified ZVI systems—including doped ZVI, bio-stabilized composites, and ZVI supported on advanced materials like MXene and nanocellulose—for effective treatment of water containing metal species like As(III/V), Hg(II), Cr(VI), and Ni(II). Emphasis is placed on understanding the underlying mechanisms, including redox reactions, surface complexation, and synergistic adsorption–reduction pathways. Key factors affecting adsorption efficiency—such as pH, temperature, ZVI dosage, and competing ions—are thoroughly analyzed, alongside adsorption kinetics and isotherm models. Modified ZVI composites exhibit enhanced stability, selectivity, and reusability, demonstrating promising performance even in complex aqueous environments. Despite significant progress, challenges such as nanoparticle passivation, limited field-scale data, and potential toxicity of byproducts remain. The review concludes by highlighting future research directions focused on improving material longevity, regeneration efficiency, selective adsorption, and integration with other advanced remediation technologies for sustainable and scalable groundwater treatment. Full article

The agrifood industries generate tremendous amounts of waste, with the valorization of these wastes being of the utmost importance. The aim of this work was to synthesize green zero-valent iron nanoparticles (nZVI) using hydromethanolic extracts of spent coffee grounds (SCGs) and post-distillation residues of Cistus ladanifer L. leaves (CLL). The synthesized nZVI were then analyzed by dynamic light scattering (DLS), and their size, polydispersity index (PDI), and zeta potential (ZP) were determined. Different dispersants (water and methanol) and the impact of a surfactant (Tween^® 20) were tested for DLS analysis. nZVI dispersed in water and added with Tween^® 20 displayed lower agglomeration, particle size, and PDI, but higher ZP than nZVI without the addition of surfactant and methanolic suspension. These results provide further insight into the applicability of surfactants in nZVI characterization. Full article

One of the most widely employed methods for adsorption is the utilization of biochar produced during pyrolysis. Biochar has attracted considerable attention due to its oxygen-containing functional groups and relatively high specific surface area. In alignment with the principles of cleaner production, the sludge generated from sewage treatment plants is typically classified as waste. However, it can be effectively repurposed as an adsorbent following pyrolysis and subsequent nanoparticle modification. This environmentally friendly approach presents an ecological alternative to conventional water treatment methods. The objective of this study is to evaluate the efficiency of batch adsorption for the removal of phosphate from wastewater using both unmodified and modified sewage sludge biochars (SSBs) that were produced at various temperatures (300 °C, 400 °C, 500 °C, and 600 °C) and modified with zero-valent iron nanoparticles (nZVI-SSB300, nZVI-SSB400, nZVI-SSB500, and nZVI-SSB600). The findings indicate that biochar modified with functional nanoparticles is a highly effective adsorbent for the removal of phosphate from wastewater. As demonstrated by the research results, the adsorption capacity of modified biochar is approximately 3 to 3.5 times greater than that of the unmodified variants. The phosphate removal efficiency with modified biochars was optimal with nZVI-SSB600. In experiments with a phosphate concentration (25 mg/L), the modified sorbent biochar exhibited an equilibrium adsorption capacity of 23.74 mg/g, translating to a phosphate removal efficiency of 60%. Under similar test conditions, at an initial phosphate concentration of 50 mg/L, the adsorption capacity improved to 25.67 mg/g (75% efficiency); at 75 mg/L, it reached 27.97 mg/g (80%); at 100 mg/L, it was 28.44 mg/g (85%); and at 125 mg/L, it achieved 29.48 mg/g (89%). The models confirmed the observed adsorption behavior, yielding a maximum phosphate adsorption capacity (q_e) of 19.00 mg/g for the 600 °C pyrolysis of modified biochar at the primary phosphate concentration (25 mg/L). Furthermore, this study indicates that the influence of solution pH on phosphate adsorption remains stable and maximal (nZVI-SSB600, ranging from 16.87 to 20.46 mg/g) within the pH range of 3 to 8. On average, the modified biochar (nZVI-SSB) demonstrated 20 to 30% superior adsorption performance compared to the unmodified biochar (SSB). Additionally, significant differences were noted between various ambient temperatures, ranging from 5 °C to 25 °C. As the ambient temperature increased, the sorption capacity of the adsorbent exhibited a considerable improvement. With a primary concentration of phosphate (100 mg/g) at 5 °C, the adsorption capacity of nZVI-SSB600 was measured at 7.99 mg/g; this increased to 14.33 mg/g at 10 °C, 21.79 mg/g at 20 °C, and 28.44 mg/g at 25 °C. This research highlights the potential application of biochar in wastewater treatment for phosphate removal, simultaneously enabling the effective utilization of generated sewage sludge waste through pyrolysis and coating with zero-iron nanoparticles, resulting in a sustainable solution. Full article

Nanocomposites (NCs) consisting of zero-valent iron nanoparticles (nZVI) immobilized in chitosan (CS) were prepared and employed for the removal of hexavalent chromium (Cr(VI)) from both synthetic and real wastewater. Medium (MCS)- and high (HCS)-molecular-weight chitosan and stabilization with carboxymethylcellulose (CMC) and different nZVI loads were explored. Characterization through scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS) and X-ray diffraction (XRD) revealed millimeter-sized spheres with micrometer-sized nZVI clusters randomly distributed. Better nanoparticle dispersion was observed in NCs from the CMC-MCS and HCS combinations. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that CS binds to Fe(II) or Fe(III) on the surface of nZVI through its functional groups -CONH-, -N-H, and -C-OH and through the -${\mathrm{COO}}^{-}$ functional group of CMC, forming a bidentate bridge complex. Through experiments with synthetic waters, it was found that the elimination of Cr(VI) was favored by lowering the pH, obtaining the maximum percentage of Cr(VI) removal at pH 5.5. With real waters, it was shown that increasing the mass of NCs also improved the removal of Cr(VI), following a pseudo-second-order adsorption kinetics. The synthesized materials show great potential for applications in environmental remediation, showing good efficiency in the removal of Cr(VI) in wastewater. Full article

This study explores the valorization of tea leaf waste by extracting polyphenols through reflux extraction, subsequently using them to synthesize zero-valent iron nanoparticles (nZVI). The in situ generated nanoparticles, when combined with fixed amounts of hydrogen peroxide, facilitated the removal of various dyes (methylene blue, methyl orange, and orange G) via a hetero-catalytic Fenton process. The iron nanoparticles were thoroughly characterized by gas adsorption of N₂ at 77 K, scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), FT-IR spectroscopy, X-ray diffraction (XRD), and thermal analysis, including thermogravimetric analysis (TG) and temperature-programmed reduction (TPR). A statistical design of experiments and response surface methodology were employed to analyze the influence of polyphenol, Fe(III), and H₂O₂ concentrations on dye removal efficiency. The results demonstrated that optimizing the operational conditions could achieve 100% dye removal efficiency. This study highlights the potential of nZVI synthesized through eco-friendly methods as a promising solution for water decontamination involving diverse model dyes, thus contributing to sustainable waste management and environmental protection. Full article

Nanotechnology, a rapidly growing field, holds tremendous promise as it harnesses the unique properties and applications of nanoparticulate materials on a nanoscale. In parallel, the pressing global environmental concerns call for the development of sustainable chemical processes and the creation of new materials through eco-friendly synthesis methods. In this work, zero-valent iron nanoparticles (nZVI) were synthesized using an innovative and environmentally friendly approach as an alternative to conventional methods. This method leverages the antioxidant capacity of natural plant extracts to effectively reduce dissolved metals and produce nZVI. The chosen extract of green tea plays a pivotal role in this process. With the extract in focus, this study delves into the remarkable capability of nZVI in degrading two dyes commonly used in medicine, chrysoidine G and methylene blue, in aqueous solutions. Additionally, Fenton-type oxidation processes are explored by incorporating hydrogen peroxide into the nanoparticle mixture. By applying the statistical design of experiments and Response Surface Methodology, the influence of four key parameters—initial concentrations of Fe²⁺, Fe³⁺, H₂O₂, and polyphenols—on dye elimination efficiency in aqueous solutions is thoroughly analyzed. The obtained results demonstrate that advanced oxidation technologies, such as Fenton-type reactions in conjunction with nanoparticles, achieve an excellent efficiency of nearly 100% in eliminating the dyes. Moreover, this study reveals the synergistic effect achieved by simultaneously employing nZVI and the Fenton process, showcasing the potential for further advancements in the field. Full article

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. Full article

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 COD_fed) 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. Full article

Batch and transport experiments were used to investigate the remediation of loamy sand soil contaminated with Cr(VI) using zero-valent iron nanoparticles (nZVI) stabilized by carboxymethylcellulose (CMC-nZVI). The effect of pH, ionic strength (IS), and flow rate on the removal efficiency of Cr(VI) were investigated under equilibrium (uniform transport) and non-equilibrium (two-site sorption) transport using the Hydrus-1D model. The overall removal efficiency ranged from 70 to over 90% based on the chemical characteristics of the CMC-nZVI suspension and the transport conditions. The concentration and pH of the CMC-nZVI suspension had the most significant effect on the removal efficiency and transport of Cr(VI) in the soil. The average removal efficiency of Cr(VI) was increased from 24.1 to 75.5% when the concentration of CMC-nZVI nanoparticles was increased from 10 to 250 mg L⁻¹, mainly because of the increased total surface area at a larger particle concentration. Batch experiments showed that the removal efficiency of Cr(VI) was much larger under acidic conditions. The average removal efficiency of Cr(VI) reached 90.1 and 60.5% at pH 5 and 7, respectively. The two-site sorption model described (r² = 0.96–0.98) the transport of Cr(VI) in soil quite well as compared to the uniform transport model (r² = 0.81–0.98). The average retardation of Cr(VI) was 3.51 and 1.61 at pH 5 and 7, respectively, indicating earlier arrival for the breakthrough curves and a shorter time to reach maximum relative concentration at lower pH. The methodology presented in this study, combining column experiment and modeling transport using the Hydrus-1D model, successfully assessed the removal of Cr(VI) from polluted soils, offering innovative, cost-effective, and environmentally friendly remediation methodologies. Full article

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. Full article

The objective of this study was to explore the removal of nitrate ions from groundwater by employing dynamic permeable reactive barriers (PRBs) with A400-nZVI. This research aimed to determine the parameters of the barrier and evaluate its overall capacity to retain nitrate ions during percolation with a potassium nitrate solution. The process involves obtaining zerovalent iron (nZVI) nanoparticles, which were synthesized and incorporated onto an anionic resin support material (A400) through the reduction reaction of ferrous ions with sodium borohydride (NaBH₄). This is achieved by preparing a ferrous sulfate solution, contacting it with the ion exchange resin at various solid–liquid mass ratios and gradually adding sodium borohydride under continuous stirring in an oxygen-free environment to create the A400-nZVI barrier. The results of the study, focusing on the development of permeable reactive barriers composed of nano zero-valent iron and ion exchangers, highlight the significant potential of water treatment processes when appropriately sized. The research specifically assesses the effectiveness of NO₃⁻ removal by using the A400-nZVI permeable reactive barrier, conducting laboratory tests that simulate a naturally stratified aquifer with high nitrate contamination. Full article

Nano zero-valent iron (nZVI) technologies have gained recognition for the remediation of heavily contaminated sites and reused as backfilling soil. The moisture environment at these sites not only impacts the reactions and reactivity of nZVI but also the dynamic responses of compacted backfilled soils. The research explored the effects of different nZVI dosages (0.2%, 0.5%, 1%, 2%, and 5%) on Lead-Zinc-Nickel ions contaminated soil under a controlled-moisture condition. Cyclic triaxial tests were performed to evaluate the dynamic responses of treated soil samples prepared using a consistent moisture compaction method. Particle size distribution and Atterberg limits tests assessed changes in particle size and plasticity. The study revealed a minor reduction in the particle size, liquid limit, plastic limit, and plasticity index of the contaminated soil. Notably, increasing nZVI dosages in treated soils led to growing Atterberg limits. An increase in the specific sand fraction of treated soils was observed with nZVI, suggesting nanoparticles–soil aggregations favoring existing larger particles. Stepwise loading cyclic triaxial tests indicated an optimal dynamic response of soil treated with 1% nZVI under the controlled-moisture condition, proven by notable enhancements in the maximum shear modulus, maximum shear stress, less shear strain, and higher damping ratio within the small strain range. It should be noted that moisture content in treated soils declined significantly with higher nZVI dosages during preparation, potentially impeding effective aggregation and the formation of a solid soil skeleton. These findings advance the importance of considering the balanced nZVI dosage and moisture content when employing the safety assessment of practical applications in both nano-remediation techniques and soil mechanics. Full article

Soil heavy metal pollution has become an important environmental problem in the world. Therefore, it is particularly important to find effective remediation methods for heavy metal contaminated soil. Biochar (BC) is a kind of soil heavy metal passivator with a wide range of applications. It also has a good effect on the control of soil heavy metal pollution. However, BC does not have sufficient fixation capacity for para-anionic contaminants. Nano-zero-valent iron (nZVI) has a strong reducing ability, which can make up for this defect of BC. Therefore, to improve the passivation effect of heavy metals, nanomaterial modification is proposed to optimize biochar performance. Nanoparticles are used as carriers to impregnate biochar (BC). Biochar-supported nano-ferric zero-valent materials are prepared to repair soil contaminated by heavy metals. Results show that the physicochemical properties of modified biochar are significantly optimized. At 5%, the modified biochar (1:3) treatment group had the best remediation effect on Cd-contaminated soil, which significantly promoted soil catalase activity. The modified biochar (3:1) treatment group had the best remediation effect on As-contaminated soil, and significantly increased soil pH, Cation Exchange Capacity (CEC), and available Fe content. Modified biochar (1:3) with 3% added content was used to repair actual composite heavy metal contaminated soil, and the relative percentage content of Cu, Zn, As, Cd, and Pb residue state increased by 10.28%, 7.81%, 7.44%, 9.26%, and 12.75%, respectively. The effects of nZVI@BC on the remediation effect and soil enzymes of Cd- and As-contaminated soil under different factors such as mass ratio of carbon and iron and dosage were studied. The remediation mechanism of Cd- and As-contaminated soil was clarified, and a good solidification and stabilization effect was obtained. This provides a theoretical basis for nZVI@BC remediation of soil contaminated by Cd and As. It has good application value in the treatment and remediation of complex heavy metal contaminated soil. Full article

The subsurface injection of nanoscale zero-valent iron particles (nZVI) for the in situ reductive remediation of contaminated aquifers has grown over the last 25 years. However, several efforts are still being made to improve the stability and delivery of nZVI and to simplify the procedure for site-specific injection design. In this study, the injectability and mobility of a commercial nZVI-based reactive gel was tested in a radial geometry laboratory setup. The gel proved to be highly mobile in sandy porous media, allowing for the achievement of a radius of influence (ROI) of 0.7 m with a homogeneous nZVI distribution within the domain. The experimental results therefore confirmed that nZVI permeation injection with a good radius of influence is possible in conductive formations. The software MNMs 2023 (Micro- and Nanoparticle transport, filtration, and clogging Model-Suite) was then applied to model the radial transport experiment and extrapolate results with the aim of developing a new graphical tool for simple and effective nZVI permeation injection design. For this purpose, 1800 numerical simulations were performed to build two multiparametric maps to predict the expected ROI in two typical aquifer lithologies and over a wide range of operating conditions. Full article