Showing papers on "Ferric published in 2019"

Ferrous-cysteine–phosphotungstate nanoagent with neutral pH fenton reaction activity for enhanced cancer chemodynamic therapy

Abstract: The key bottleneck problem of chemodynamic therapy (CDT) is that the efficiency depends heavily on an acidic chemical environment. However, there is a sufficient blood supply on the surface of solid tumours, resulting in neutral-pH surface regions, strongly reducing the effectiveness of CDT. In this study, chelating complex ferrous-cysteine–phosphotungstate nanoparticles (FcPWNPs) are synthesized to serve as new CDT nanoagents that break through the limitation of a neutral pH, ensuring CDT efficiencies at both an acidic and neutral pH. The CDT efficiency is increased by introducing cysteine and phosphotungstate, which form an Fe chelating complex to inhibit the formation of inert Fe(OH)x, and accelerate electron transfer between ferric and ferrous ions, respectively. Due to this ferrous chelating strategy and associated electron transfer property, the FcPWNPs can destroy cancer cells from the neutral-pH tumour surface to the acidic interior, thus realizing a complete CDT cancer therapy.

A review on nanotechnological application of magnetic iron oxides for heavy metal removal

Abstract: With increasing trend in industrialization, heavy metals possess a great threat to the environment due to their discharge in water and wastewater above permissible limits. Heavy metals have toxic effects on human and environment. However, advancement in newly budding and fangled nanotechnology offers better treatment techniques. Development of novel and cost-effective 0D, 1D, 2D and 3D nanomaterials for environmental remediation, pollution detection and other applications has attracted considerable attention. Zero valent iron and iron oxide nanoparticles are found to be the best candidates for heavy metal adsorption and removal. Various mechanical, optical and electrical properties of nanoparticles play important role in nanoparticle formation and interaction. Forms of iron oxide such as hematite (α Fe2O3) and magnetite (Fe3O4) nanoparticles of varied morphology and size (10 nm, 20 nm, 50 nm etc.) were synthesized by various methods like sol-gel, precipitation, hydrothermal processes and magnetic nano-composites with different iron precursors (iron acetate, iron nitrate, ferric chloride, ferrous sulphate etc.). Iron oxide nanoparticles (in a variety of chemical and structural forms) have already exhibited its diversity and potential in many frontiers of environmental area. Present review is focused on the application of iron and iron oxide nanoparticles towards heavy metal removal.

Redox and pH gradients drive amino acid synthesis in iron oxyhydroxide mineral systems.

Abstract: Iron oxyhydroxide minerals, known to be chemically reactive and significant for elemental cycling, are thought to have been abundant in early-Earth seawater, sediments, and hydrothermal systems. In the anoxic Fe2+-rich early oceans, these minerals would have been only partially oxidized and thus redox-active, perhaps able to promote prebiotic chemical reactions. We show that pyruvate, a simple organic molecule that can form in hydrothermal systems, can undergo reductive amination in the presence of mixed-valence iron oxyhydroxides to form the amino acid alanine, as well as the reduced product lactate. Furthermore, geochemical gradients of pH, redox, and temperature in iron oxyhydroxide systems affect product selectivity. The maximum yield of alanine was observed when the iron oxyhydroxide mineral contained 1:1 Fe(II):Fe(III), under alkaline conditions, and at moderately warm temperatures. These represent conditions that may be found, for example, in iron-containing sediments near an alkaline hydrothermal vent system. The partially oxidized state of the precipitate was significant in promoting amino acid formation: Purely ferrous hydroxides did not drive reductive amination but instead promoted pyruvate reduction to lactate, and ferric hydroxides did not result in any reaction. Prebiotic chemistry driven by redox-active iron hydroxide minerals on the early Earth would therefore be strongly affected by geochemical gradients of Eh, pH, and temperature, and liquid-phase products would be able to diffuse to other conditions within the sediment column to participate in further reactions.

Unexpected Favorable Role of Ca2+ in Phosphate Removal by Using Nanosized Ferric Oxides Confined in Porous Polystyrene Beads

Abstract: Polystyrene-based nanoferric oxide composite is a representative nanomaterial successfully applied in scale-up water decontamination for arsenic and phosphorus. However, little is available on the effect of solution chemistry (for instance, the coexisting Ca2+) on the long-term performance of the nanocomposite. In this study, we carried out 20 cyclic runs of phosphate adsorption-desorption on a polymer-supported ferric nanocomposite HFO@201. Unexpectedly, an enhanced phosphate removal was observed in the presence of Ca2+, which is quite different from its adverse effect on phosphate capture by granular ferric oxide. Further mechanistic studies revealed that enhanced phosphate removal was mainly realized via the Ca-P coprecipitation inside the networking pores of HFO@201 as well as the possible formation of the multiple Fe-P-Ca-P complex. The complex formation led to a distinct increase in P adsorption, and the coprecipitation, driven by the accumulated OH- in confined pores during phosphate adsorption and alkaline regeneration, favored P removal via the formation of amorphous calcium phosphate (ACP) and hydroxyapatite inside. TEM-EDS spectra indicated that coprecipitation did not occur on the surface of loaded nano-HFO, greatly mitigating its adverse effect on P adsorption on the surface of nano-HFO. Fixed-bed column study showed that the presence of Ca2+ increased the effective treatable volume of HFO@201 toward P-containing influents by ∼70%. This study is believed to shed new insights into the effect of solution chemistry on similar nanocomposites for advanced water treatment.

Mechanism of Catalytic O2 Reduction by Iron Tetraphenylporphyrin.

Abstract: The catalytic reduction of O2 to H2O is important for energy transduction in both synthetic and natural systems. Herein, we report a kinetic and thermochemical study of the oxygen reduction reaction (ORR) catalyzed by iron tetraphenylporphyrin (Fe(TPP)) in N, N'-dimethylformamide using decamethylferrocene as a soluble reductant and para-toluenesulfonic acid ( pTsOH) as the proton source. This work identifies and characterizes catalytic intermediates and their thermochemistry, providing a detailed mechanistic understanding of the system. Specifically, reduction of the ferric porphyrin, [FeIII(TPP)]+, forms the ferrous porphyrin, FeII(TPP), which binds O2 reversibly to form the ferric-superoxide porphyrin complex, FeIII(TPP)(O2•-). The temperature dependence of both the electron transfer and O2 binding equilibrium constants has been determined. Kinetic studies over a range of concentrations and temperatures show that the catalyst resting state changes during the course of each catalytic run, necessitating the use of global kinetic modeling to extract rate constants and kinetic barriers. The rate-determining step in oxygen reduction is the protonation of FeIII(TPP)(O2•-) by pTsOH, which proceeds with a substantial kinetic barrier. Computational studies indicate that this barrier for proton transfer arises from an unfavorable preassociation of the proton donor with the superoxide adduct and a transition state that requires significant desolvation of the proton donor. Together, these results are the first example of oxygen reduction by iron tetraphenylporphyrin where the pre-equilibria among ferric, ferrous, and ferric-superoxide intermediates have been quantified under catalytic conditions. This work gives a generalizable model for the mechanism of iron porphyrin-catalyzed ORR and provides an unusually complete mechanistic study of an ORR reaction. More broadly, this study also highlights the kinetic challenges for proton transfer to catalytic intermediates in organic media.

Biogenic synthesis of ferric oxide nanoparticles using the leaf extract of Peltophorum pterocarpum and their catalytic dye degradation potential

Abstract: Plant-mediated green synthesis of nanoparticles is an eco-friendly and cheap method since it makes use of phyto-compounds present in various plant parts as reducing and stabilizing agents. Herein, magnetic, ferric oxide nanoparticles (FONPs) were prepared by utilizing the leaf extract of Peltophorum pterocarpum for the first time. Rod-like FONPs with agglomerations were witnessed in FE-SEM images. Sharp peaks for elemental oxygen and iron were witnessed in EDS spectrum. XRD spectrum ascertained the crystallinity of the FONPs and showed both γ and α–Fe 2 O 3 phases. The average crystallite size was 16.99 nm. A large specific surface area (66.44 m 2 /g) was found in BET analysis and the FONPs were mesoporous (pore diameter = 7.92 nm). TGA results showed a 20% weight loss during heating up to 800 °C. FTIR spectrum showed significant bands for various phyto-compounds and Fe–O. The Fenton-like catalytic efficiency of FONPs was studied for the methylene blue dye degradation during which 90% removal was noticed within 220min. The experimental results were satisfactorily fitted into a second-order model with a degradation constant of 0.0987 L/mg min. Also, the catalytic activity of the FONPs was assessed for the removal of MB dye with the reducing agent NaBH 4 . A remarkable dye degradation (92%) was attained within 27min, and the results were best suited for a first-order model with a kinetic degradation constant of 0.0856min −1 . Therefore, the green-synthesized FONPs obtained here could be used in the degradation of dyes as nanocatalysts for the remediation of wastewater.

Nitrogen-doped carbon dots with high quantum yield for colorimetric and fluorometric detection of ferric ions and in a fluorescent ink

Abstract: Nitrogen-doped carbon dots (N-CDs) with a quantum yield of 41 ± 3% and excellent stability were prepared and are shown to be viable probes for the determination of ferric ions, which is a strong quencher of fluorescence. The absorption peak of the N-CDs is located at 325 nm. The optimal excitation and emission wavelengths of the N-CDs are 340 nm and 430 nm, respectively. The fluorometric response to Fe(III) is linear in the ranges between 1.0 and 21.0 μM and between 0.05 and 30.0 μM, and the limits of detection are 0.28 μM in case of colorimetry and 13.5 nM in case of fluorometry. Quenching by Fe(III) is mainly attributed to a combination of chelation (static quenching) and inner filter effect. The N-CDs also can be used as a new sort of fluorescent ink owing to the strong luminous performance and chemical inertness.

Fe2+/Fe3+ Ions Chelated with Ultrasmall Polydopamine Nanoparticles Induce Ferroptosis for Cancer Therapy

Abstract: Ferroptosis, a promising mechanism of killing cancer cells, has become a research hotspot in cancer therapy. Besides, advantages of polymeric nanomaterials in improving anticancer efficacy and reducing side effect are widely accepted. In this work, based on the property of polypodamine to chelate metal ions, ultrasmall poly(ethylene glycol)-modified polydopamine nanoparticles, (UPDA-PEG)@Fe2+/3+ nanoparticles, a novel ferroptosis agent, was rationally designed by chelating iron ions on ultrasmall polydopamine nanoparticles modified by PEG. This treatment led to a bigger specific surface area, which could support more reactive sites to chelate large number of iron ions, which is beneficial for exploring the detailed mechanism of ferroptosis-induced tumor cell death by iron ions. Also, the pH-dependent release of iron ions can reach approximately 70% at pH 5.0, providing the advantage of application in tumor microenvironment. The in vitro tests showed that the as-prepared NPs exhibit an effective anticancer effect on tumor cells including 4T1 and U87MG cells, yet ferric ions show a stronger ability of killing cancer cells than ferrous ions. Differences between ferrous ions and ferric ions in the ferroptosis pathway were monitored by the change of marker, including reactive oxygen species (ROS), glutathione peroxidase 4, and lipid peroxide (LPO), as well as the promoter and inhibitor of ferroptosis pathway. UPDA-PEG@Fe2+ nanoparticles induce ferroptosis that depends more on ROS; however, a more LPO-dependent ferroptosis is induced by UPDA-PEG@Fe3+ nanoparticles. Additionally, the in vivo studies using tumor-bearing Balb/c mice demonstrated that the as-prepared NPs could significantly inhibit tumor progression. UPDA-PEG@Fe2+/3+ nanoparticles reported herein represent the nanoparticles related to iron ions for chemotherapy against cancer through the ferroptosis pathway.

Potential of Crystalline and Amorphous Ferric Oxides for Biostimulation of Anaerobic Digestion

Abstract: Iron oxides have been widely investigated to accelerate the conversion of organic wastes to methane. However, the potential mechanism involved with different types of iron oxides is a controversial topic. In this study, crystalline Fe2O3 and amorphous Fe (OH)3 were respectively supplemented to explore the effects of the crystal form of Fe(III) on anaerobic digestion. The results showed that the addition of Fe2O3 and Fe(OH)3 both significantly enhanced COD removal and biomethanation compared with the control. The reason was related to that the supplement of Fe(OH)3 induced an efficient microbial dissimilatory iron reduction to enhance the decomposition of complex organics into simples. Consistently, 28.3% of Fe(OH)3 dosed at the initial stage were reduced into Fe(II), while no obvious iron reduction was observed with the Fe2O3 supplement. Interestingly, Fe2O3 significantly stimulated the secretion of protein and humic acid-like substances in EPS, leading to an electron-transfer capacity higher than that fo...

Treatment of a Mature Landfill Leachate: Comparison between Homogeneous and Heterogeneous Photo-Fenton with Different Pretreatments

Abstract: This study focuses on the treatment of a mature landfill leachate by coagulation and photo-Fenton at different conditions. Optimal coagulation is carried out with ferric chloride in acid conditions; and with alum in near-neutral conditions, to minimize the use of sulphuric acid for pH adjustment (1 g/L vs. 7.2 g/L), the generation of sludge and the increase of conductivity in the final effluent. In both cases, a similar chemical oxygen demand (COD) removal is obtained, higher than 65%, which is high enough for a subsequent photo-Fenton treatment. However, the removal of absorbance at 254 nm (UV-254) was significantly higher with ferric chloride (83% vs. 55%), due to the important removal of humic acids at acid pH. The best results for coagulation are 2 g/L ferric chloride at initial pH = 5 and 5 g/L alum at initial pH = 7. After coagulation with ferric chloride, the final pH (2.8) is adequate for a homogeneous photo-Fenton using the remaining dissolved iron (250 mg/L). At these conditions, using a ratio H2O2/COD = 2.125 and 30 min contact time, the biodegradability increased from 0.03 to 0.51. On the other hand, the neutral pH after alum coagulation (6.7) allows the use of zero valent iron (ZVI) heterogeneous photo-Fenton. In this case, a final biodegradability of 0.32 was obtained, after 150 min, using the same H2O2/COD ratio. Both treatments achieved similar results, with a final COD, UV-254 and color removal greater than 90%. However, the economic assessment shows that the approach of ferric chloride + homogeneous photo-Fenton is much cheaper (6.4 €/m3 vs. 28.4 €/m3). Although the discharge limits are not achieved with the proposed combination of treatments, the significant increase of the pre-treated leachate biodegradability allows achieving the discharge limits after a conventional biological treatment such as sequencing batch reactor, which would slightly increase the total treatment cost.