Search Results (234)

In order to develop an efficient, environmentally friendly heavy metal ions adsorbent, the amino-modified expanded vermiculite-supported nano zero-valent iron (nZVI@PEI/EVMT) was prepared by using polyethyleneimine (PEI) as the functional reagent and expanded vermiculite (EVMT) as the carrier. The characterization results of nZVI@PEI/EVMT confirm that the PEI modification did not destroy the crystal configuration of EVMT, and when nano zero-valent iron (nZVI) was successfully loaded onto the PEI/EVMT surface, the value of saturation magnetic field was 41.5 emu/g, which could be separated from solution with magnet. The performance of Cr(VI) adsorption onto nZVI@PEI/EVMT was studied, showing that the ideal mass ratio for nZVI@PEI/EVMT was 1:1, and the removal capacity was largest when solution pH was 2. After four adsorption–desorption cycles, the adsorption amounts remained 40.1 mg/g. The Cr(VI) adsorption onto nZVI@PEI/EVMT was more consistent with a pseudo-second-order kinetics equation. Isotherm adsorption data accord with the Langmuir model, which suggests that the adsorption was the monolayer, the maximum adsorption amount was 116.2 mg/g at 30 °C and pH 2, and the adsorption was spontaneous and endothermic. It was inferred that the adsorption mechanisms included electrostatic attraction, reduction, chemical complexation, and co-precipitation. Full article

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

The widespread industrial use of chromium has exacerbated water contamination issues globally. In this study, a nitrogen-doped wheat straw biochar loaded with nanoscale zero-valent iron composite (nZVI/N-KBC) was synthesized via a liquid-phase reduction method, and its adsorption properties for hexavalent chromium (Cr(VI)) in aqueous solutions were systematically investigated. The material was characterized using SEM, XRD, Raman spectroscopy, FTIR, and XPS. Experimental results demonstrated that under optimal conditions (pH 2, 0.05 g adsorbent dosage, and 50 mg/L initial Cr(VI) concentration), the adsorption capacity reached 41.29 mg/g. Isothermal adsorption analysis revealed that the process followed the Langmuir model, indicating monolayer adsorption with a maximum capacity of 100.9 mg/g. Kinetic studies show that the adsorption conforms to the pseudo-second-order kinetic model, and thermodynamic and XPS analyses jointly prove that chemical adsorption is dominant. Thermodynamic analyses confirmed the endothermic and entropy-driven nature of adsorption. Mechanistic studies via XPS and FTIR revealed a dual mechanism: (1) partial adsorption of Cr(VI) onto the nZVI/N-KBC surface, and (2) predominant reduction in Cr(VI) to Cr(III) mediated by Fe⁰ and Fe²⁺. This study highlights the synergistic role of nitrogen doping and nZVI loading in enhancing Cr(VI) removal, offering a promising approach for remediating chromium-contaminated water. 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 accumulation of heavy metal cadmium (Cd) in farmland soil in edible parts of crops seriously threatens plant growth, human health, and even the global ecological environment. Finding stabilization remediation technology is an important means to treat Cd-contaminated soil. This study comprehensively evaluated the synergistic effects of independent or combined application of biochar (BC) (10, 30 g kg⁻¹) and nano zero-valent iron (nZVI) (0.1% w/w) on soil properties and morphological and physiological traits of pakchoi (Brassica rapa L. subsp. chinensis) under Cd (1, 3 mg kg⁻¹) stress by pot experiments. It was shown that Cd toxicity negatively affected soil properties, reduced pakchoi biomass and total chlorophyll content, and increased oxidative stress levels. On the contrary, the combined application of BC (30 g kg⁻¹) and nZVI (0.1%, w/w) reduced the Cd accumulation in the shoot parts of pakchoi from 0.78 mg·kg⁻¹ to 0.11 mg·kg⁻¹, which was lower than the Cd limit standard of leafy vegetables (0.20 mg kg⁻¹) in GB 2762-2017 “National Food Safety Standard”. Compared with the control, the treatment group achieved a 61.66% increase in biomass and a 105.56% increase in total chlorophyll content. At the same time, the activities of catalase (CAT) and superoxide dismutase (SOD) increased by 34.86% and 44.57%, respectively, and the content of malondialdehyde (MDA) decreased by 71.27%. In addition, the application of BC alone (30 g·kg⁻¹) increased the soil pH value by 0.43 units and the organic carbon (SOC) content by 37.82%. Overall, the synergistic effect of BC (30 g kg⁻¹) and nZVI (0.1% w/w) helped to restore soil homeostasis and inhibit the biotoxicity of Cd, which provided a new option for soil heavy metal remediation and crop toxicity mitigation. Full article

Ensuring access to clean water for drinking, agriculture, and recreational activities remains a global challenge. Groundwater, supplying approximately 50% of domestic water and 40% of agricultural irrigation, faces increasing threats from climate change, population growth, and unsustainable agricultural practices. These factors contribute to groundwater contamination, notably nitrate pollution resulting from excessive fertilizer use, which poses risks to water quality and public health. Addressing this issue demands innovative, efficient, and sustainable remediation technologies. Permeable reactive barriers (PRBs) have emerged as promising solutions for in situ groundwater treatment, using reactive media to transform contaminants into less toxic forms. PRBs offer advantages like low energy consumption and minimal maintenance. This study uses bibliometric analysis to explore the scientific production of PRBs for nitrate remediation, revealing research trends, key focus areas, and significant contributions. It included 141 articles published from 1975 to 2023. Early research focused on basic mechanisms and materials like zero-valent iron (ZVI), while recent studies emphasize sustainability and cost-effectiveness using low-cost materials such as agricultural byproducts. The findings highlight a growing focus on the circular economy and the need for more in situ studies to assess PRB performance under varying conditions. PRBs show significant potential for enhancing groundwater management and long-term water quality in agricultural contexts. Full article

In this study, inexpensive, environmentally friendly, and biodegradable cellulose filter paper was used to load nano zero-valent iron (nZVI), effectively improving the dispersibility of nZVI and successfully preparing the supported modified cellulose filter paper (FP-nZVI). Subsequently, the capacity of FP-nZVI to remove Cr(VI) in a flow system was explored. FP-nZVI was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Traditional single-factor experiments often require a large number of repeated experiments when analyzing the interactions among multiple variables, resulting in a long experimental cycle and high consumption of experimental materials. This research used the Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD) and the Artificial Neural Network (ANN) to optimize and predict the removal process of Cr(VI). This RSM investigated the interactions between the response variable (Cr(VI) removal rate) and the independent variables (Cr(VI) concentration, pH value, and flow rate). A highly significant quadratic regression model was constructed, which was proven by a high F value (93.92), an extremely low p-value (<0.0001), and a high determination coefficient (R² = 0.9918). An ANN model was established to forecast the correlation between independent variables and the removal rate of Cr(VI). Both models demonstrate remarkable consistency with the experimental data; however, from the perspective of statistical parameters, the ANN model has more significant advantages; the coefficient of determination R² reaches 0.9937, which is higher than that of RSM (0.9918); the values of indicators such as MSE, RMSE, MAE, MAPE, AAD, and SEP are all smaller than those of RSM. The ANN exhibits greater excellence in prediction error, value fluctuation, and closeness to the actual value and has a more excellent prediction ability. The experiment for treating Cr(VI) with FP-nZVI was optimized, achieving good results. Meanwhile, it also provides a valuable reference for similar experimental studies. Full article

The excessive levels of neonicotinoid insecticides, particularly thiacloprid (THI), in the environment have become a significant threat to ecosystems. This study investigates the catalytic degradation of THI using pinewood biochar (PBC), zero-valent iron (ZVI), and ZVI/PBC composite, with a particular focus on the reaction activity modulation mediated by organic acids (humic acid: HA and oxalic acid: OA). Reductive dechlorination dominated THI degradation as observed by Cl⁻ release kinetics. Compared to HA (39.73%), the OA (73.44%) addition markedly increased the THI removal efficiency by ZVI/PBC, which alone has a lower removal efficacy, i.e., 37.29%. The increase in the THI removal rate was attributed to its enhanced electron transfer capacity. As confirmed by electrochemical characterization, the addition of organic acids promotes electron transfer between THI and catalysts (ZVI, PBC, or ZVI/PBC), thereby improving the removal efficiency of THI. XRD/XPS analyses elucidated that OA preferentially converted passivating Fe₂O₃/Fe₃O₄ on ZVI/PBC to reactive FeOOH and formed electron-conductive Fe–COO bonds, thereby suppressing oxide layer formation. PBC amplified these effects through ZVI dispersion and electron shuttling, reducing aggregation-induced activity loss. These findings provide a mechanistic framework for optimizing ligand-engineered iron composites, offering practical strategies to enhance pesticide remediation efficiency in organic acid-rich environmental systems. Full article

Trichloroethylene (TCE), a volatile organic compound commonly used as a solvent, is frequently detected in contaminated groundwater. In the zero-valent iron (ZVI) Fenton process, TCE can be eventually dechlorinated into non-toxic products, which is mainly caused by hydroxyl radicals derived from H₂O₂. However, some key factors in the dechlorination of TCE in the zero-valent iron Fenton process have not been studied clearly. In the present study, the effects of the initial TCE concentration, initial H₂O₂ concentration, dosage of ZVI, initial pH, and temperature on TCE degradation in the ZVI Fenton process were studied. In addition, the structure and surface morphology of the ZVI used in this study were analyzed through scanning electron microscopy (SEM), N₂ adsorption–desorption, and X-ray diffractometry (XRD). The experimental results demonstrated that the dosage of ZVI and initial H₂O₂ concentration had obvious impacts on TCE degradation. At a ZVI dosage of 2 g/L and an initial H₂O₂ concentration of 0.53 mol/L, more than 97% of TCE could be degraded within 24 h at 25 °C. We found that the ZVI Fenton process could efficiently degrade TCE at a broad pH range and room temperature, making it applicable to groundwater remediation. TCE degradation was associated with Fe²⁺ concentration. Spectroscopic analyses indicated that the oxide film formed on the ZVI surface was associated with Fe²⁺ concentration in enhanced TCE dechlorination. The ZVI Fenton process could work at a wide range of TCE concentrations (0–200 mg/L). Full article

Tannic acid (TA), a prevalent polyphenolic contaminant in industrial effluents, significantly inhibits microbial activity in anaerobic digestion, thereby diminishing wastewater treatment efficiency. In this study, a sulfidized nano zero-valent iron (S-nZVI) composite incorporated into sludge biochar (SB), abbreviated as SB-S-nZVI, was synthesized via a one-step hydrothermal method. The composite’s adsorption capacity for TA and its impact on anaerobic digestion were systematically evaluated. Experimental results showed that SB-S-nZVI achieved a TA removal efficiency of 99.31% under optimal conditions (S/Fe = 0.05, dosage = 0.3 g·L⁻¹), with a maximum adsorption capacity of 337.08 mg·g⁻¹. In anaerobic digestion, the addition of 0.03 g·L⁻¹ SB-S-nZVI enhanced chemical oxygen demand (COD) removal by 3.32%, increased specific methanogenic activity by 62.66%, and improved the microbial community composition, particularly enriching hydrolytic bacteria (Georgenia) and methanogenic archaea (Methanosaeta). The mechanistic analysis revealed that the FeS protective layer of SB-S-nZVI inhibited nano zero-valent iron oxidation and facilitated chemisorption-driven TA removal. This study presents an innovative approach for the integrated treatment of TA-contaminated wastewater by combining adsorption, degradation, and energy recovery. 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

The extensive utilization of nano-zero-valent iron (nZVI) and its engineered derivatives has prompted significant environmental concerns, particularly regarding their phytotoxicological impacts, which remain inadequately characterized. This investigation systematically evaluated the phytotoxicological responses induced by nZVI, Chlorella vulgaris biochar (BC), and Chlorella vulgaris biochar loaded with nano-zero-valent iron (BC/nZVI) on mung bean seed germination and subsequent seedling development. The experimental data revealed that both the nZVI and BC/nZVI treatments significantly suppressed the germination indices, including germination rate, radicle and plumule elongation, and biomass accumulation, with nZVI demonstrating the most pronounced inhibitory effects. During the vegetative growth phases, nZVI exposure substantially impaired plant morphogenesis, manifested through reduced vertical growth, diminished fresh and dry biomass production, and the onset of premature foliar chlorosis, necrosis, desiccation, and, ultimately, plant mortality. A comparative analysis indicated that the BC/nZVI composites exhibited less severe photosynthetic inhibition relative to pristine nZVI. Biochemical assays demonstrated that nZVI exposure elicited the substantial upregulation in antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), concomitant with abnormal ferric ion accumulation in root tissues. Notably, BC/nZVI composites demonstrated the partial mitigation of these physiological disturbances. These empirical findings underscore that excessive iron bioavailability from nZVI induces substantial phytotoxicological stress, while BC matrix incorporation provides the partial amelioration of these adverse effects on seedling ontogeny. Full article

The objective of this study was to examine the impact of various foliar fertilization treatments on the growth of new shoots, photosynthetic characteristics of leaves, and mineral nutrient content in the leaves of ‘Marselan’ grapevines. Five distinct combinations of nano zero-valent iron (n ZVI), compound sodium nitrophenolate (CSN), and potassium dihydrogen phosphate (KH₂PO₄) were administered through foliar application to ‘Marselan’ grapevines cultivated in the Wuwei region of the Hexi Corridor, with water spray serving as the control treatment. The results showed that T5 treatment (15 mg·L⁻¹ n ZVI + 0.4 g·L⁻¹ CSN + 2.5 g·L⁻¹ KH₂PO₄) significantly increased the leaf area and SPAD value of ‘Marselan’ grapes; T4 treatment (15 mg·L⁻¹ n ZVI + 0.4 g·L⁻¹ CSN + 1.67 g·L⁻¹ KH₂PO₄) significantly increased the internode length of new grape shoots. T5 treatment was favorable to increase the basic coarseness of new grape shoots, the net photosynthetic rate of the leaves, and stomatal conductance; leaf transpiration rate was the highest under the T4 and T5 treatments; T3 (15 mg·L⁻¹ n ZVI + 0.4 g·L⁻¹ CSN + 1.25 g·L⁻¹ KH₂PO₄), T4, and T5 treatments could improve leaf initial fluorescence at different periods. At 45 days after flowering, the maximum photochemical efficiency under the T3 and T4 treatments reached the highest value throughout the period, and the T3 treatment improved leaf potential maximum quantum yield. Meanwhile, the leaf nitrogen and phosphorus content under the T5 treatment were the highest in the five periods. Additionally, the contents of potassium (K), manganese (Mn), copper (Cu), and zinc (Zn) in the leaves increased significantly under the T4 and T5 treatments. The following conclusions emerged from a comprehensive analysis: the T4 treatment was the best, and the T5 treatment was the second most effective. Full article

A stabilized biochar (BC)–nano-scale zero-valent iron (nZVI) composite (BC-nZVI@Cell-g-PAA) was prepared using cellulose-grafted polyacrylic acid (Cell-g-PAA) as the raw material through in situ polymerization and liquid-phase reduction methods for the remediation of hexavalent chromium (Cr(VI))-contaminated water. BC-nZVI@Cell-g-PAA was characterized by XRD, FT-IR, SEM, BET, TEM, and XPS. According to the batch experiments, under optimized conditions (Cr(VI) concentration of 50 mg/L, pH = 3, and dosage of 2 g/L), the BC-nZVI@Cell-g-PAA composite achieved maximum Cr(VI) removal efficiency (99.69%) within 120 min. Notably, BC, as a carrier, achieved a high dispersion of nZVI through its porous structure, effectively preventing particle agglomeration and improving reaction activity. Simultaneously, the functional groups on the surface of Cell-g-PAA provided excellent protection for nZVI, significantly suppressing its oxidative deactivation. Furthermore, the composite effectively reduced Cr(VI) to insoluble trivalent chromium(Cr(III)) species and stabilized them on its surface through immobilization. The synergistic effects of physical adsorption and chemical reduction greatly contributed to the removal efficiency of Cr(VI). Remarkably, the composite exhibited excellent reusability with a removal efficiency of 62.4% after five cycles, demonstrating its potential as a promising material for remediating Cr(VI)-contaminated water. In conclusion, the BC-nZVI@Cell-g-PAA composite not only demonstrated remarkable efficiency in Cr(VI) removal but also showcased its potential for practical applications in environmental remediation, as evidenced by its sustained performance over multiple reuse cycles. Moreover, Cr(VI), a toxic and carcinogenic substance, poses significant risks to aquatic ecosystems and human health, underscoring the importance of developing effective methods for its removal from contaminated water. Full article

Sewage sludge was treated with nanoscale zero-valent iron (nZVI) to enhance biogas and methane (CH₄) production, and the influence of key parameters on the material’s anaerobic digestion (AD) efficiency was analyzed using sigmoidal mathematical models. In this study, three dosages of nZVI (0.5%, 1.5% and 3%) were added to the anaerobic sludge digestion system to enhance and accelerate the sludge decomposition process. The results showed that cumulative biogas yield after 41 days of digestion increased by 23.9% in the reactor with a nZVI dosage of 1.5%. Correspondingly, the highest CH₄ production enhancement by 21.5% was achieved with a nZVI dosage of 1.5% compared to the control. The results indicated that this nZVI dosage was optimal for the AD system, as it governed the highest biogas and CH₄ yields and maximum removal of total and volatile solids. Additionally, to predict biogas and CH₄ yields and evaluate kinetic parameters, eight kinetic models were applied. According to the results of the modified Gompertz, Richards and logistic models, the nZVI dosage of 1.5% shortened the biogas lag phase from 11 to 5 days compared to the control. The Schnute model provided the best fit to the experimental biogas and CH₄ data due to highest coefficients of determination (R²: 0.9997–0.9999 at 1.5% and 3% nZVI dosages), as well as the lowest Akaike’s Information Criterion values and errors. This demonstrated its superior performance compared to other models. Full article