Search Results (9)

Fenton oxidation is effective for degrading refractory organic contaminants, but slow Fe³⁺-to-Fe²⁺ regeneration under acidic conditions limits continuous H₂O₂ activation. Here, Acid Orange 7 (AO7) was used as a model pollutant to evaluate a coupled Mn⁰/Fe/H₂O₂ system designed to promote iron redox cycling and enhance H₂O₂ activation. AO7 degradation was examined under different operating conditions, and reactive species and mechanisms were identified using electron spin resonance spectroscopy, chemical probes, and quenching experiments. Under optimized conditions (pH 3.0, 10 μM AO7, 2 mM H₂O₂, 9 μM Fe²⁺, and 0.05 g/L Mn⁰), 88% of AO7 was degraded within 30 min. Hydroxyl radicals (•OH) and FeO²⁺ were identified as the main reactive species, accounting for 88.6% and 11.4% of AO7 degradation, respectively. Mn⁰ promoted AO7 degradation by directly activating H₂O₂ to form •OH and by reducing Fe³⁺ to Fe²⁺, thereby sustaining Fe²⁺/Fe³⁺ cycling and facilitating •OH and FeO²⁺ generation. Sulfate and carbonate had negligible effects, whereas fulvic acid, nitrate, and chloride inhibited degradation. AO7 degradation decreased to 40% in lake water and 60% in river water. These results demonstrate that Mn⁰ addition can enhance Fenton-like oxidation by accelerating iron redox cycling, suggesting its potential in treating dye-contaminated wastewater under controlled operational conditions. Full article

High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. This study highlights their dual functionality, not only as conventional oxidants but also as mechanistic mediators within redox cycles that underpin next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal-based AOPs into photocatalysis, sonocatalysis, and electrochemical regeneration is explored through a newly proposed classification framework, highlighting their potential in the development of energy efficient hybrid systems. In addition, this work addresses the critical yet underexplored area of environmental fate, elucidating the post-oxidation transformation pathways of high-valent species, with particular attention to their implications for metal recovery and nutrient valorization. This review highlights the potential of high-valent metal-based AOPs as a promising approach for zero wastewater treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed loop reactor engineering, will bridge the gap between laboratory research and real-world applications. 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

This study investigated the impact of soil colloidal characteristics on the transfer patterns of different Cu and Cd speciation in contaminated soil treated with three different amendments: lime (L), zero-valent iron (ZVI), and attapulgite (ATP). It seeks to clarify the activation hazards and aging processes of these modifications on Cu and Cd. Compared with the control (CK), the available Cu concentrations treated with amendments reduced in the short term (6 months) by 96.49%, 5.54%, and 89.78%, respectively, and Cd declined by 55.43%, 32.31%, and 93.80%, respectively. Over a 12-year period, there was no significant change in the immobile effect with L, while Cu and Cd fell by 19.06% and 40.65% with ZVI and by 7.63% and 40.78% with ATP. Short- and long-term increases in the readily reducible iron and manganese oxide fraction of Cu and Cd were accompanied by a considerable rise in the concentrations of amorphous iron oxide in the soil and colloid after amendment treatment. This suggested that Cu and Cd were immobilized and stabilized in part by amorphous iron oxide. Full article

Type 1 diabetes is caused by the inability of the pancreatic beta cells to produce sufficient amounts of insulin, an anabolic hormone promoting the absorption of the blood glucose by various cells in the body, primarily hepatocytes and skeletal muscle cells. This form of impaired metabolism has been traditionally treated with subcutaneous insulin injections. However, because one such method of administration does not directly correspond to the glucose concentrations in the blood and may fail to reduce hyperglycemia or cause hypoglycemia, the delivery of insulin in a glucose-dependent manner has been researched intensely in the present and past. This study tested the novel idea that the supplementation of polymeric reservoirs containing insulin with metallic nanoparticle precursors responsive to the redox effect of glucose could be used to create triggers for the release of insulin in direct response to the concentration of glucose in the tissue. For that purpose, manganese oxide nanoparticles were dispersed inside a poly(ε-caprolactone) matrix loaded with an insulin proxy and the resulting composite was exposed to different concentrations of glucose. The release of the insulin proxy occurred in direct proportion to the concentration of glucose in the medium. Mechanistically, as per the central hypothesis of the study, glucose reduced the manganese cations contained within the metal oxide phase, forming finer and more dissipative zero-valent metallic nanoparticles, thus disrupting the polymeric network, opening up pores in the matrix and facilitating the release of the captured drug. The choice of manganese for this study over other metals was justified by its use as a supplement for protection against diabetes. Numerical analysis of the release mechanism revealed an increasingly nonlinear and anomalous release accompanied by a higher diffusion rate at the expense of chain rigidity as the glucose concentration increased. Future studies should focus on rendering the glucose-controlled release (i) feasible within the physiological pH range and (ii) sensitive to physiologically relevant glucose concentrations. These technical improvements of the fundamental new concept proven here may bring it closer to a real-life application for the mitigation of symptoms of hyperglycemia in patients with diabetes. Full article

This study aimed to investigate the effects of zerovalent iron (ZVI/Fe₀) on growth, yield and grain quality of rice (Oryza sativa L.) cv. BRRI dhan49 in arsenic (As)-contaminated soils. The pot experiment was arranged in a complete randomized design (CRD). The treatments on rice applied were As in soils at As₀ (0 mg kg⁻¹), As₂₀ (20 mg kg⁻¹), and As₄₀ (40 mg kg⁻¹) with a combination of ZVI at ZVI₀ (0%), ZVI_0.5 (0.5%), ZVI_1.0 (1.0%), and ZVI_1.5 (1.5%) with three replications. Contents of phosphorus (P), potassium (K), manganese (Mn), zinc (Zn), iron (Fe), and As in grains of rice; and Fe and As content in cultivated soils were determined. The application of ZVI had negative or no effect on shoot weight, tiller number, and grain yield. Although application of ZVI had little or no effect on thousand grain weight, P, K, Zn, and Mn of rice grains, Fe content in rice grains was increased by ZVI treatments in a dose-dependent manner. The grain As content was non-significantly reduced by the ZVI application. Soil bacterial population was negatively influenced by the ZVI in a dose-dependent manner which might be linked with As content in the soils. Therefore, a further elaborative study is needed to elucidate the mechanisms of the effects of ZVI and soil As on rice and rhizosphere soil microorganisms. Full article

The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe⁰-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe⁰/MnO₂ system). The resulting system is a very complex one where characterization is challenging. The present communication uses methylene blue discoloration (MB method) to characterize the Fe⁰/MnO₂ system. Shaken batch experiments (75 rpm) for 7 days were used. The initial MB concentration was 10 mg L⁻¹ with the following mass loading: [MnO₂] = 2.3 g L⁻¹, [sand] = 45 g L⁻¹, and 0 < [Fe⁰] (g L⁻¹) ≤ 45. The following systems where investigated: Fe⁰, MnO₂, sand, Fe⁰/MnO₂, Fe⁰/sand, and Fe⁰/MnO₂/sand. Results demonstrated that MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the test-tubes. Results confirm the complexity of the Fe⁰/MnO₂/sand system, while establishing that both MnO₂ and sand improve the efficiency of Fe⁰/H₂O systems in the long-term. The mechanisms of water decontamination by amending Fe⁰-based systems with MnO₂ is demonstrated by the MB method. Full article

Nanoscale zerovalent iron (nZVI) is the most widely used nanomaterial for environmental remediation. The impacts of nZVI on terrestrial organisms have been recently reported, and in particular, plant growth was promoted by nZVI treatment in various concentrations. Therefore, it is necessary to investigate the detailed physiological and biochemical responses of plants toward nZVI treatment for agricultural application. Here, the effects of nZVI on photosynthesis and related biochemical adaptation of soil-grown Arabidopsis thaliana were examined. After treatment with 500 mg nZVI/kg soil, the plant biomass increased by 38% through enhanced photosynthesis, which was confirmed by the gas-exchange system, carbon isotope ratio and chlorophyll content analysis. Besides, the iron uptake of the plant increased in roots and leaves. The magnetic property measurements and transmission electron microscopy showed that the transformed particles were accumulated in parts of the plant tissues. The accumulation of carbohydrates such as glucose, sucrose and starch increased by the enhanced photosynthesis, and photosynthetic-related inorganic nutrients such as phosphorus, manganese and zinc maintained homeostasis, according to the increased iron uptake. These findings suggest that nZVI has additional or alternative benefits as a nano-fertilizer and a promoter of CO₂ uptake in plants. Full article

In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites. Full article