Search Results (426)

Toxic elements such as arsenic (As) and antimony (Sb) in the arsenic-alkali residue resulted from the antimony smelting industry posed a threat to the ecosystem and must be properly treated to prevent their release into the environment. The integration of stabilizers into mechano-chemical approaches has emerged as a highly promising strategy for the detoxification of non-ferrous metal smelting slags, drawing increasing research attention in recent years. Meanwhile, zero-valent iron has been widely applied owing to its low cost, ready availability, and high reactivity. In this study, modified zero-valence iron powders (ZVI) were prepared and employed to stabilize As and Sb in the arsenic-alkali residue via a mechanical ball-milling process. After modification using acetic acid, the surface properties of the iron powders were substantially altered, leading to the formation of iron oxides. The optimum operation conditions for the mechanical ball-milling process were determined as follows: a milling time of 1 h, the dosage of the detoxifier (n_As:n_Fe) of 1:1, and a ball-to-material ratio of 6:1. Under these conditions, the leaching toxicity of the As and Sb were 1.483 mg/L and 0.208 mg/L, respectively. The stabilization of As and Sb in the residue was primarily attributed to their adsorption onto the surface iron oxides and the formation of new insoluble phases during the ball-milling process. Full article

Nanoscale zero-valent iron (nZVI) exhibits great potential in the field of organic pollutant remediation due to its strong reducibility, high specific surface area and unique core–shell structure. However, pristine nZVI has inherent drawbacks including severe particle aggregation, surface passivation and poor electron selectivity, which greatly restrict its practical remediation performance. To improve the reactivity of nZVI, researchers have developed multiple modification approaches that significantly improve the dispersibility, stability and reactivity of nZVI. This review summarizes the main nZVI modification strategies, including metal modification, surface coating, carrier loading, sulfidation modification and biological integration. The advantages and limitations of each modification method are compared. Furthermore, the underlying removal mechanisms of modified nZVI toward typical organic pollutants are elaborated, covering direct reduction, advanced oxidation and synergistic degradation pathways. Key factors governing the degradation efficiency of modified nZVI are subsequently analyzed. Finally, existing bottlenecks for practical implementation and future research perspectives are proposed. Full article

Zero-valent iron (ZVI) improves nitrogen and phosphorus removal efficiency in municipal wastewater treatment systems. However, its effects on glycogen-accumulating organisms (GAOs) and the mechanisms of action are still not fully understood. This study investigated the influence of ZVI on GAOs by assessing its effect on the performance of a denitrification reactor dominated by Candidatus Competibacter sp. (with a relative abundance of 46.33%). After ZVI addition, the reactor harbored the iron-autotrophic denitrifying bacterium Ferruginibacter sp. (0.38%), the iron-reducing bacterium Pseudomonas sp. (0.26%), and the iron-oxidizing bacterium Comamonas sp. (0.26%). This effectively integrated ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) with heterotrophic denitrification alongside iron ammonium oxidation and nitrate-dependent ferrous oxidation. The integrated approach decreased aeration duration while improving the removal efficiency of PO₄³-P (98.01 ± 2.54%) and total inorganic nitrogen (TIN) (62.01 ± 1.45%). The combined of ZVI in systems predominantly occupied by GAOs enhanced the carbon storage capacity of the bacteria. Full article

Engineered nanomaterials have been increasingly proposed for the treatment of contaminated soils. Nevertheless, most available evidence has been obtained in water, artificial substrates or short-term laboratory experiments, and performance in real soil is substantially more variable. This review examines nanoscale zero-valent iron, photocatalytic metal oxides, carbon-based nanomaterials, and supported or hybrid formulations, with particular attention to the soil properties and contaminant characteristics that control their mobility, transformation, reactivity, and persistence. Nano-enabled treatments can decrease the mobility of arsenic, chromium, lead, and other potentially toxic elements and can promote the degradation of selected pesticides and hydrocarbons. However, opposite responses have also been reported, including mobilisation of non-target elements, nanoparticle aggregation and passivation, effects on microbial communities and plants, contaminant rebound, and potential transport beyond the treated zone. Environmental assessment should therefore consider both the target contaminant and the applied or transformed nanomaterial, together with ecological and occupational exposure pathways. Current evidence does not support nanoremediation as a general replacement for conventional technologies. Its main value lies in its use as a site-specific component of integrated remediation strategies selected according to soil properties, contaminant behaviour, treatment scale, cost, life-cycle impacts, and future land use. European field experience remains limited, particularly in unsaturated soils, and no harmonised EU-wide authorisation procedure specifically for soil nanoremediation currently exists. Wider implementation will require realistic field trials, long-term monitoring, safer and recoverable formulations, transparent regulatory assessment, and evaluation of soil functions and ecosystem-service recovery. A site-specific decision framework is proposed to support material selection, risk–benefit evaluation, and responsible implementation. Full article

Lead (Pb) accumulation in paddy soils promotes its transfer to rice grains, posing persistent risks to food safety and human health. Here, we developed a GSNO-encapsulated chitosan–biochar-supported sulfidized nanoscale zero-valent iron composite (GSNO-CS@S-nZVI/BC) to integrate sustained nitric oxide (NO) delivery with Pb immobilization in rice–soil systems. The novelty of this strategy lies in coupling a biocompatible NO donor with a Pb-reactive CS@S-nZVI/BC matrix to simultaneously alleviate Pb-induced physiological stress in rice and suppress Pb migration from soil to edible grains. In hydroponic experiments, Pb exposure reduced rice fresh weight, dry weight, and chlorophyll levels by 71.2%, 55.6%, and 75.1%, respectively. Compared with Pb treatment alone, GSNO-CS@S-nZVI/BC increased rice dry weight and chlorophyll levels by 68.5% and 260%, respectively, while decreasing Pb concentrations in roots and shoots by 78.2% and 85.8%. In soil pot experiments, GSNO-CS@S-nZVI/BC reduced Pb concentrations in roots, shoots, panicles, and grains by 57.6%, 57.0%, 40.3%, and 64.3%, respectively. It also decreased the grain Pb bioconcentration factor by 80.7%, reduced the soil-to-root Pb translocation factor by 84.41%, and lowered the grain Pb bioconcentration factor to 0.043 ± 0.007. Mechanistically, GSNO-CS@S-nZVI/BC promoted root iron plaque formation by 176.1% and increased Pb adsorption by root iron plaque by 156.9%, while decreasing the oxidizable Pb fraction in soil by 11% and increasing the reducible Pb fraction by 10%. These results indicate that GSNO-CS@S-nZVI/BC mitigates Pb toxicity through sustained NO release, enhanced root iron plaque-mediated Pb sequestration, and soil Pb stabilization. Overall, this nano-enabled amendment provides a promising strategy for reducing Pb transfer from contaminated paddy soils to rice grains and improving the safe utilization of Pb-contaminated farmland. Full article

4-Chlorophenol (4-CP) is a persistent and highly toxic pollutant commonly found in groundwater. However, its efficient degradation remains challenging due to the rapid agglomeration of conventional zero-valent iron (ZVI) nanoparticles, their narrow pH operating range, and the environmental risks associated with synthetic chelating agents. To address these limitations, this study presents a rationally designed catalytic system integrating cyclodextrin polymer (CDP)-supported bimetallic Cu-Fe nanoparticles (Cu-Fe-CDP) with citric acid (CA) as a green complexing agent. The porous CDP matrix effectively mitigates nanoparticle agglomeration and provides abundant active sites, while the Fe-Cu bimetallic coupling accelerates electron transfer and iron corrosion. Critically, CA acts as a biocompatible ligand that sustains Fe(II)/Fe(III) redox cycling, expands the effective pH range, and enhances hydroxyl radical (·OH) generation. The system achieves 92.13% degradation of 4-CP within 80 min at pH 9.0 and nearly complete removal at pH values between 3.0 and 7.0. Mechanistic studies, including electron paramagnetic resonance (EPR) spectroscopy and radical quenching tests, confirm the dominance of ·OH radicals (82.67% inhibition by TBA) and the essential role of surface Fe(II)/Fe(III) cycling. The catalyst exhibits excellent reusability, broad-spectrum activity toward multiple pollutants, and sustained performance in real water matrices and long-term column tests with minimal metal leaching. This work demonstrates a chemically robust strategy for chlorophenol remediation using green citric acid and biodegradable CDP without exogenous oxidant addition, showing promise for further development toward practical applications. Full article

The increasing accumulation of industrial solid waste and worsening groundwater pollution pose significant environmental challenges. This study introduces a Si-Ca-Fe-based ceramsite from solid wastes with exceptional Cd adsorption capacity. A comprehensive investigation was conducted on the phase evolution, adsorption properties, and underlying mechanisms of the synthesized ceramsite. The findings revealed that the optimum sintering temperature for the ceramsite, characterized by austenite and pyroxene, was 1140 °C, which balanced mechanical strength and Cd adsorption capacity. Remarkably, the ceramsite (6.0 g) was immersed in 5 L of a Cd(NO₃)₂ solution for 21 h under initial conditions (pH = 7 and temperature = 20 °C), and the ceramsite exhibited a notable Cd adsorption capacity of 5.47 mg/g (initial Cd concentration: 53.42 mg/L), with a maximum theoretical capacity of 9.32 mg/g according to the Langmuir isotherm. An in-depth analysis of adsorption kinetics, phase composition, and EDS data indicated that the primary adsorption mechanism was the zero-valent iron (ZVI) corrosion-driven reaction. This ZVI formed in situ under reducing conditions during the ceramsite’s preparation and subsequently aided in the precipitation of Cd(OH)₂. Additionally, the honeycomb structure of the ceramsite, containing fine pores (approximately 2–5 μm), enhanced physical adsorption via capillary action, further improving Cd removal. These insights offer a robust foundation for crafting efficient, solid waste-derived ceramsite tailored for heavy metal extraction from polluted water, presenting a compelling approach to concurrent waste recycling and environmental remediation. Full article

Calcium hypochlorite (CH) is a strong oxidant that can be utilized to enhance sludge hydrolysis and anaerobic digestion (AD) performance; however, its suppressive effect on methanogens restricts the development of CH treatment technologies. This laboratory-scale study introduced zero-valent iron (ZVI) into a CH-treated sludge AD system to alleviate the adverse effect, thereby synergistically enhancing biomethane production, and the correlation between methane yield and the two key treatment parameters (ZVI and CH dosages) was explored. The experimental results revealed that the best conditions for the ZVI + CH method were 5 g/L of ZVI plus 0.12 g/g of volatile suspended solids (VSSs) of CH, under which the maximum biomethane yield of 275.8 mL/g VSS was achieved, representing increases of 81.5%, 43.2%, and 28.2% over the control, solo ZVI, and solo CH conditions, respectively. More organic matter in the sludge was found to be degraded during AD by the ZVI + CH treatment compared with the control, solo ZVI, or solo CH conditions. An enzyme activity analysis illustrated that the ZVI + CH treatment not only enhanced the bioactivity of anaerobes but also eliminated the suppression of methanogens by CH. A microbial analysis demonstrated that all functional microbes responsible for sludge AD were enriched by the ZVI + CH treatment, with total abundances of 8.41% and 20.58% in the control and ZVI + CH-treated reactors, respectively. Full article

Antibiotic contamination has become an emerging challenge in water treatment and environmental protection due to the increasing discharge of antibiotics and their transformation products, which exhibit ecological toxicity and resistance to degradation. Conventional treatment technologies often show limitations in antibiotic removal, including insufficient efficiency, high operational costs, and potential secondary pollution. Nanoscale zero-valent iron (nZVI) has attracted extensive attention as a promising remediation material for antibiotic wastewater treatment owing to its large specific surface area, strong reducing capability, and excellent adsorption properties. However, the practical application of nZVI is still restricted by particle aggregation and surface passivation, which reduce its reactivity, stability, and long-term performance. This review provides a comprehensive overview of recent advances in nZVI-based materials for antibiotic removal, with emphasis on preparation strategies, surface modification approaches, removal mechanisms, and integrated treatment technologies. The performance of pristine nZVI and modified nZVI-based systems in antibiotic degradation and removal is systematically discussed. Furthermore, current challenges, including material deactivation, iron leaching, environmental risks, and scale-up limitations, are critically evaluated, and future perspectives toward efficient, stable, and sustainable antibiotic wastewater treatment are proposed. Full article

Nanoscale zerovalent iron (nZVI) has shown promise for soil remediation. This study examined the impact of this nanomaterial on barley and wheat grown in alkaline soil throughout a complete growth cycle, to assess its potential as a fertilizer and to understand its behavior in an uncontaminated matrix. A greenhouse experiment was conducted in which barley and wheat plants were grown in soil treated with a commercial nZVI slurry at 0 and 5% (equivalent to 0 and 8 g kg⁻¹). Physiological parameters were monitored throughout the growth cycle, and plants were harvested after five months. Biomass production, impact on root and leaf ultrastructure, and the concentrations of Fe and other nutrients were determined in several plant tissues. Soil physicochemical properties were not adversely affected by nZVI application, and an increase in Fe availability was observed regardless of the species, from 1 mg kg⁻¹ to 5.2 and 6.6 mg kg⁻¹ in barley and wheat soils, respectively. However, this increase did not translate into higher Fe accumulation in plant tissues at the end of the growth cycle, nor did it enhance plant growth in either species. Therefore, under the experimental conditions evaluated, the application of nZVI as an iron fertilizer cannot be recommended. Notably, both crops exhibited a greater sensitivity to nZVI during early stages of development, as evidenced by significant reductions in chlorophyll content and increased oxidative stress. These initial adverse effects were progressively alleviated as plant growth advanced, with no detectable alterations in cellular ultrastructure, allowing both species to complete their growth cycle. Full article

In this study, thermally hydrolyzed sludge and nanoscale zero-valent iron (nZVI) nanoparticles are combined to assess their impact on enhancing methane production compared with conventional anaerobic digestion without pre-treated sludge and/or nZVI. To this end, 12 digesters were set up for a period of 27 days and divided into four groups, with or without pre-treated sludge and nZVI. To determine the changes in microbiota diversity and metabolic pathways that occurred, DNA shotgun sequencing was carried out. As a results, in the digester containing thermally hydrolyzed sludge and nZVI, methane production was slower but prolonged than with untreated sludge without added nZVI, where it was significantly higher but of shorter duration. Additionally, nZVI addition shortened the lag phase in both sludge types compared to the control digesters. Regarding microbial adaptation, results showed that it was slower in thermally hydrolyzed sewage sludge than in untreated sludge. In terms of microbial diversity, several methanogenic microorganisms have been identified, alongside roughly 75 metabolic pathways directly or indirectly linked to methane production confirming the results achieved related to methane production. the addition of nZVI to thermally hydrolyzed sludge promoted microbial diversity (such as Methanoculleus, Methanobacterium, Methanospirillum, Methanofastidiosum) along with the methane synthesis pathway; these results have been statistically confirmed. Ultimately, the proposed combination proves effective for methane production by improving the availability of nutrients to microorganisms, thereby stimulating the metabolism involved in methanogenesis. Full article

Cr(VI) has become an urgent environmental concern due to its high toxicity. Adsorption is regarded as an effective technique for Cr(VI) removal, and high-performance adsorbents remain in great demand. In this study, waste-derived magnetic biochar (Fe⁰-Fe₃O₄ MB) was synthesized via synchronous pyrolysis combined with liquid-phase reduction, using Chinese medicinal residue as biomass feedstock and iron-based sludge as the sole iron source instead of traditional chemical agents. Mössbauer spectroscopy (MS) results confirmed the feasibility and high efficiency of synthesizing Fe⁰ using iron sludge as the iron source; meanwhile, in situ generated Fe₃O₄ and biochar effectively restrained particle aggregation and the surface passivation of Fe⁰. Cr(VI) adsorption fitted well with pseudo-second-order kinetics and Langmuir isotherm models, which suggests a predominant monolayer chemisorption process. The Fe⁰-Fe₃O₄ MB possessed excellent superparamagnetism, with a saturation magnetization of 66.74 emu/g. Rapid Cr(VI) adsorption was achieved within 30 min at pH 2 and 35 °C, with a maximum adsorption capacity of 128.36 mg/g. The main adsorption mechanisms may involve multiple pathways, including physical adsorption, electrostatic attraction, chemical reduction, and surface complexation. This study provides a feasible strategy for solid waste resource utilization and the fabrication of stabilized functional zero-valent iron materials, realizing the efficient adsorption treatment of Cr(VI)-containing wastewater. Full article

Rhodamine B (RhB) is a typical xanthene-based cationic dye. Its widespread application has brought serious safety and environmental risks. Heterogeneous Fenton systems based on zero-valent iron (Fe⁰) are promising for RhB degradation. However, bare Fe⁰ suffers from severe agglomeration and surface passivation. In this study, alumina with a large pore volume and high specific surface area was employed as a support to enhance Fe⁰ dispersion and stability. The catalyst was prepared via a glucose-assisted carbothermal reduction method, and the formation of Fe⁰ was confirmed by X-ray diffraction and electron microscopy analyses. Under optimal conditions (pH = 3.58, catalyst dosage = 0.8 g·L⁻¹, H₂O₂ = 10 mM), 10 mg·L⁻¹ RhB was completely degraded within 25 min, with a pseudo-first-order rate constant of 0.432 min⁻¹. This exhibits a faster degradation rate and efficiency advantage. Radical quenching experiments indicated that hydroxyl radicals (•OH) were the dominant reactive species, while singlet oxygen (¹O₂) also contributed to the degradation process. Two primary degradation pathways, including N-deethylation and hydroxylation, were identified. The catalyst showed moderate reusability with slight deactivation after repeated cycles. This study demonstrates that tailoring the pore structure of alumina supports is an effective strategy to enhance Fe⁰ dispersion, mass transfer, and catalytic performance in heterogeneous Fenton systems. Full article

Carbamazepine (CBZ), a poorly biodegradable antibiotic, is widely detected in aquatic environments, posing potential threats to ecosystems and human health. There is an urgent need to develop efficient water treatment technologies. This study successfully prepared nitrogen-doped biochar composite materials loaded with zero-valent iron (Fe⁰@CN) via a one-pot calcination method for activating peroxymonosulfate (PMS) to degrade CBZ. The material was systematically characterized using multiple analytical techniques. Results indicate that Fe⁰@CN-1.5 exhibits a high specific surface area (482.65 m²/g) and an abundant mesoporous structure, with nitrogen doping promoting graphitic structure formation and the uniform dispersion of zero-valent iron. Under conditions of a 0.3 g/L catalyst loading, a 15 mM PMS concentration, and an initial pH of 5.5, 30 mg/L of CBZ achieved 97% degradation within 30 min. Radical quenching experiments and electrochemical analysis indicate that ·SO₄⁻ and ·OH are the primary active species in this system, alongside non-radical electron transfer processes. The material demonstrates excellent degradation performance and cycling stability across various real-world water bodies and pollutant systems. This study provides a carbon-based catalytic material with application potential and a theoretical basis for the efficient treatment of antibiotic wastewater. Full article

Zero-valent iron-supported biochar (Fe⁰@BC) integrates multiple functions, including adsorption, complexation, and reduction, exhibiting promising application prospects for the removal and degradation of organic pollutants. However, it still faces challenges such as complex preparation processes and the irreversible deactivation of iron centers. Herein, a double-layer core–shell iron-based biochar composite (Fe⁰/Fe₃C@BC) featuring a “zero-valent iron (Fe⁰) core–iron carbide (Fe₃C) interlayer–graphitized carbon shell” structure was successfully synthesized via a one-step carbothermal reduction method. Furthermore, its synergistic adsorption and degradation mechanism toward florfenicol (FLO) in the absence of external oxidants was systematically investigated. The 4% FeBC-800 composite (0.5 g·L⁻¹) demonstrated a rapid removal efficiency, eliminating 99.89% of FLO (100 mg·L⁻¹) within 30 min, and exhibited exceptional durability by maintaining approximately 90% of its removal efficiency after four consecutive regeneration cycles. The adsorption behavior of FLO by 4% FeBC-800 fitted well with the pseudo-second-order kinetic model (R² = 0.999) and the Langmuir isotherm model (R² = 0.958). The primary adsorption mechanisms included pore filling, hydrogen bonding, surface complexation, and π-π electron donor–acceptor interactions. Interfacial electron transfer played a dominant role in the FLO degradation process. The degradation mechanism primarily involved reductive dechlorination and oxidative degradation via reactive oxygen species (ROS) generated from the activation of dissolved oxygen. This study provides a novel strategy for the development of advanced iron-based biochar materials for the highly efficient removal of persistent organic pollutants. Full article