Iron Species Research Articles

Effect of Calcination Temperature in Large-Aperture Medium-Entropy Oxide (FeCoCuZnNa)O on CO2 Hydrogenation for Light Olefins

The catalytic hydrogenation of carbon dioxide is not only a way to mitigate the greenhouse effect but also provides high-value chemicals. In this work, a medium-entropy oxide catalyst (FeCoCuZnNa)O was prepared by the sol–gel method for highly active and selective hydrogenation of CO2 to value-added hydrocarbons. When reacted at 290 °C, 2.5 MPa, and 2500 mL·gcat−1·h−1, the CO2 conversion and selectivity of olefin were affected by the calcination temperature of the catalyst, and the best performances were 39% and 41.3%. The large pore size and oxygen vacancies (Ov) formed by (FeCoCuZnNa)O promote the activation of CO2 and promote the C-C coupling reaction of Fe5C2 in a hydrogenation reaction. The promoted C-C coupling reaction was related to the surface enrichment of iron species. The presence of Ov also inhibited the excessive hydrogenation reaction, further improving the selectivity of light olefins. In addition, (FeCoCuZnNa)O did not show significant deactivation within 75 h, indicating that the catalyst has strong industrial potential.

Further Results on the Effects of the Grinding Environment on the Flotation of Copper Sulphides

Grinding conditions affect the flotation of copper sulphide minerals as changes in the properties of the grinding media and their interactions with the sulphide minerals, and between sulphide minerals themselves, affect the chemical environment in the flotation pulp. Galvanic interactions between steel grinding media and sulphide minerals, and between sulphide minerals, can lower the pulp potential, decrease the dissolved oxygen concentration in the mineral slurry, and lead to the dissolution of iron and copper from the media and the minerals. As a result, the formation of hydrophilic iron hydroxides and their adsorption on the copper sulphide minerals can be deleterious to copper flotation while pyrite (when present) can be activated to flotation by dissolved copper lowering the grade of the copper concentrate. Electrochemically less active grinding media (e.g., chrome alloy balls rather than mild steel media) can have beneficial effects on flotation performance due to the lower oxidation of the grinding media and consequently the lower production of oxidised iron species in the pulp. Copper activation of pyrite can be decreased by chemical additions to the pulp. In this paper, relevant experimental data published in the last 15 years are discussed.

An Integrated Approach to Elucidate the Interplay between Iron Uptake Dynamics and Magnetosome Formation at the Single-Cell Level in Magnetospirillum gryphiswaldense.

Iron is a crucial element integral to various fundamental biological molecular mechanisms, including magnetosome biogenesis in magnetotactic bacteria (MTB). Magnetosomes are formed through the internalization and biomineralization of iron into magnetite crystals. However, the interconnected mechanisms by which MTB uptake and regulate intracellular iron for magnetosome biomineralization remain poorly understood, particularly at the single-cell level. To gain insights we employed a holistic multiscale approach, i.e., from elemental iron species to bacterial populations, to elucidate the interplay between iron uptake dynamics and magnetosome formation in Magnetospirillum gryphiswaldense MSR-1 under near-native conditions. We combined a correlative microscopy approach integrating light and X-ray tomography with analytical techniques, such as flow cytometry and inductively coupled plasma spectroscopy, to evaluate the effects of iron and oxygen availability on cellular growth, magnetosome biogenesis, and intracellular iron pool in MSR-1. Our results revealed that increased iron availability under microaerobic conditions significantly promoted the formation of longer magnetosome chains and increased intracellular iron uptake, with a saturation point at 300 μM iron citrate. Beyond this threshold, additional iron did not further extend the magnetosome chain length or increase total intracellular iron levels. Moreover, our work reveals (i) a direct correlation between the labile Fe2+ pool size and magnetosome content, with higher intracellular iron concentrations correlating with increased magnetosome production, and (ii) the existence of an intracellular iron pool, distinct from magnetite, persisting during all stages of biomineralization. This study offers insights into iron dynamics in magnetosome biomineralization at a single-cell level, potentially enhancing the industrial biomanufacturing of magnetosomes.

Ferritinophagy is involved in hexavalent chromium-induced ferroptosis in Sertoli cells

Hexavalent chromium [Cr(VI)] has significant adverse effects on the environment and human health, particularly on the male reproductive system. Previously, we observed ferroptosis and autophagy in rat testicular injury induced by Cr(VI). In the present study, we focused on the association between ferroptosis and autophagy in mouse Sertoli cells (TM4) exposed to concentrations of 2.5 μМ, 5 μМ, and 10 μМ Cr(VI). Cr(VI) exposure altered mitochondrial ultrastructure; increased intracellular iron, malondialdehyde, and reactive oxygen species (ROS) levels; decreased glutathione content; increased TfR1 protein expression; and decreased GPX4, FPN1, and SLC7A11 protein expression, ultimately resulting in ferroptosis. Additionally, we observed ferritinophagy, increased expression of BECLIN1, LC3B, and NCOA4, and decreased expression of FTH1 and P62. Inhibition of autophagy and ferritinophagy via 3-MA and small interfering RNA (siRNA)-mediated silencing of NCOA4 ameliorated changes in ferritinophagy- and ferroptosis-associated protein expression, and reduced ROS levels. Rats exposed to Cr(VI) exhibited atrophy of testicular seminiferous tubules, a reduction in germ and Sertoli cells, and the occurrence of ferritinophagy and ferroptosis in cells of the rat testes. These results indicate that ferroptosis, triggered by NCOA4-mediated ferritinophagy, is one of the mechanisms that contribute to Cr(VI)-induced damage in Sertoli cells.

Upregulation of PRRX2 by silencing Marveld3 as a protective mechanism against radiation-induced ferroptosis in skin cells.

Radiation-induced skin injury (RISI) represents a significant complication in patients receiving radiotherapy and individuals exposed to nuclear accidents, characterized by a protracted wound-healing process relative to injuries from other etiologies. Current preventive and management approaches remain inadequate. Consequently, investigating efficacious intervention strategies that target the disease's progression characteristics holds significant practical importance. Small interfering RNA (siRNA) and overexpression plasmid were used to modulate the expression of Marvel domain containing 3 (Marveld3) and paired related homeobox 2 (PRRX2). Protein and mRNA levels were estimated by Western Blot and real-time PCR, respectively. Intracellular levels of Malondialdehyde (MDA), a terminal product of lipid peroxidation, were measured following the manufacturer's protocol for MDA assay kit. Similarly, intracellular levels of ferrous iron (Fe2+) and reactive oxygen species (ROS) were determined using their respective assay kits. Lipid peroxidation status within the cells was evaluated via BODIPY staining. Immunohistochemistry was conducted to ascertain the expression of PRRX2 in skin tissues collected at various time points following irradiation of rats. The H-score method was used to evaluate the percentage of positively stained cells and staining intensity. RNA sequencing, Gene Ontology (GO) analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were conducted by OE Biotech Company. In this study, our findings indicated that Marveld3 suppression could effectively inhibit lipid peroxidation levels in irradiated skin cells, concomitantly reducing intracellular Fe2+ content. Additionally, the silencing of Marveld3 effectively abrogated the impact of a ferroptosis agonist on cellular viability, resulting in the upregulation of 66 and 178 genes, as well as the downregulation of 188 and 31 genes in irradiated HaCaT and WS1 cells, respectively. Among the differentially expressed genes, the PRRX2 which was found to be involved in the process of ferroptosis, exhibited statistically significant upregulation. And the upregulation of PRRX2 expression may attenuate radiation-induced lipid peroxidation in skin cells, thereby functioning as a potential stress-responsive mechanism to counteract radiation effects. This study elucidates the role of Marveld3 in radiation-induced ferroptosis in skin cells. Inhibition of Marveld3 led to the upregulation of PRRX2, which subsequently resulted in a reduction of Fe2+ and ROS levels, as well as the suppression of lipid peroxidation. These effects collectively mitigated the occurrence of ferroptosis.

Intracellular Magnetic Hyperthermia Sensitizes Sorafenib to Orthotopic Hepatocellular Carcinoma Via Amplified Ferroptosis.

Sorafenib (SRF) is recognized as the primary treatment for hepatocellular carcinoma (HCC), yet the emergence of SRF resistance in many HCC patients results in unfavorable outcomes. Enhancing the efficacy of SRF in HCC remains a significant challenge. SRF works in inducing ferroptosis, a form of cell death, in cancer cells through the inhibition of glutathione peroxidase 4 (GPX4). The effectiveness of this process is limited by the low levels of cellular iron and reactive oxygen species (ROS). A promising approach to circumvent this limitation is the use of intracellular magnetic hyperthermia (MH) mediated by magnetic iron oxide nanomaterials (MIONs). When MIONs are subjected to an alternating magnetic field (AMF), they heat up, enhancing the Fenton reaction, which in turn significantly increases the production of ROS within cells. In this study, we explore the capability of MH facilitated by high-performance ferrimagnetic vortex-domain iron oxide nanoring (FVIO) to enhance the effectiveness of SRF treatment in HCC. The increased iron uptake facilitated by FVIO significantly enhances the sensitivity of HCC cells to SRF-induced ferroptosis. Moreover, the nanoheat generated by FVIO in response to an AMF further elevates ROS levels and stimulates lipid hydroperoxide (LPO) production and GPX4 inactivation, thereby intensifying ferroptosis. Both in vitro and in vivo animal studies demonstrate that combining FVIO-mediated MH with SRF significantly reduces cell viability and inhibits tumor growth, primarily through enhanced ferroptosis, with minimal side effects. The effectiveness of this combination therapy is affected by the ferroptosis inhibitor ferrostatin-1 (Fer-1) and the iron chelator deferoxamine (DFO). The combination treatment of FVIO-mediated MH and SRF offers a strategy for HCC treatment by promoting accelerated ferroptosis, presenting a different perspective for the development of ferroptosis-based anticancer therapies.

RON receptor tyrosine kinase regulates glycolysis through MAPK/CREB signaling to affect ferroptosis and chemotherapy sensitivity of thyroid cancer cells.

Anaplastic thyroid cancer (ATC) is one of the deadliest and most aggressive human malignancies for which there is currently no effective treatment. Tyrosine kinase receptor RON is highly expressed in various cancer types, including colon, pancreatic and thyroid cancer. However, its underlying role in ATC is not fully understood. The present study investigated the therapeutic potential and molecular mechanism of RON in ATC. RON expression in thyroid cancer cells was detected by western blotting. Glycolysis was assessed by measuring the extracellular acidification rate, glucose uptake, lactate concentration, and expression levels of glucose transporter 1, hexokinase 2 and pyruvate kinase M1/2. In addition, ferroptosis was assessed by detecting the levels of total iron, lipid peroxide and reactive oxygen species, and the expression levels of ferroptosis‑related proteins. Furthermore, mitochondrial function were assessed by JC‑1 staining and detection kits, respectively. The results demonstrated that RON was highly expressed in thyroid cancer cell lines. Furthermore, RON interference inhibited glycolysis, promoted ferroptosis, elevated cell sensitivity to chemotherapy and affected mitochondrial function in thyroid cancer cells. Further experiments demonstrated that RON interference affected the ferroptosis levels in thyroid cancer cells by inhibiting the glycolysis process. Mechanistically, the present results indicated that RON may affect ferroptosis, glycolysis and chemotherapy sensitivity by regulating MAPK/cAMP‑response element binding protein (CREB) signaling in thyroid cancer cells. In conclusion, the present study demonstrated that RON affected ferroptosis, glycolysis and chemotherapy sensitivity in thyroid cancer cells by regulating MAPK/CREB signaling, demonstrating its potential as a therapeutic target in thyroid cancer cells.

A Specific Targeted Enhanced Nanotherapy Strategy for Inducing Ferroptosis by Regulating the Iron Pool Levels in Tumor Cells.

Ferroptosis is an iron-dependent cell death pathway triggered by the toxic accumulation of lipid peroxides on cellular membranes. However, an imbalance in iron metabolism in tumor cells leads to the insufficient accumulation of iron ions in the iron pool, which inhibits ferroptosis. Nonspecific delivery of iron species may increase the risk of promoting tumor proliferation as well as trigger undesirable detrimental effects such as anaphylactic reactions in normal tissues. This study found that a constructed self-enhancing targeted nanocarrier can accurately regulate the iron pool levels in tumor cells. We constructed a programmatic targeted enhanced nanotherapy strategy by loading the ferroptosis inducer erastin into a self-enhancing targeted nanocarrier. This nanosystem was more effective at inducing tumor ferroptosis after upregulating the iron pool levels in tumor cells with self-enhancing targeted nanocarriers. Both in vitro and in vivo outcomes demonstrated notable anticancer ferroptosis efficacy, indicating that self-enhancing targeted nanocarriers can effectively regulate the level of the iron pool in tumor cells and promote ferroptosis. The combination of this nanotherapy strategy with self-enhancing targeted chemotherapy nanomedicines can achieve complete tumor clearance. Moreover, this self-enhancing targeted ferroptosis nanotherapy strategy is expected to be beneficial for future progress in the field of cancer self-enhancing targeted therapy.

Unraveling the role of reducing atmospheres on Fe-Zn-Al catalysts for highly selective carbon dioxide hydrogenation to light olefins

This study investigates the carbon dioxide (CO2) hydrogenation performance of Fe-Zn-Al catalysts pretreated under four distinct reducing atmospheres (H2, H2/N2, H2/CO, and CO/N2), elucidating their impact on CO2 conversion, CO selectivity, and light olefins selectivity. Combined with the characterization results, it was found that various catalyst components were obtained after activation in different atmospheres, but Fe5C2 was observed in all the catalysts after the CO2 hydrogenation reaction. The catalytic performance is intricately linked to the type of surface species produced after reduction and the Fe5C2 content. In a comparative perspective, the catalytic activity of the same catalyst in the four atmospheres followed the sequence H2>H2/N2>CO/N2>H2/CO. Notably, catalyst pretreatment with H2 yielded the highest CO2 conversion rate at 31.6 % and light olefins selectivity at 40.2 %. These results can be attributed to the highest electron density detected by XPS for the iron species on the spent catalyst and to the largest concentration of Fe5C2 formed during the reaction in the hydrogen reduced sample.

The Metallothionein System in Tetrahymena thermophila Is Iron-Inducible.

Metallothioneins are multifunctional proteins implicated in various cellular processes. They have been used as biomarkers of heavy metal exposure and contamination due to their intrinsic ability to bind heavy metals and their transcriptional response to both physiological and noxious metal ions such as cadmium (Cd) and mercury (Hg). In this study, we aimed to clarify the role of iron and reactive oxygen species (ROSs) in the induction of the metallothionein system (Mtt) in the ciliate protozoan Tetrahymena thermophila. We investigated the relative mRNA abundances of the metallothionein genes Mtt1, Mtt2/4, and Mtt5, revealing for the first time their responsiveness to iron exposure. Furthermore, by using inhibitors of superoxide dismutase (SOD) and catalase (CAT), alone or in combination with iron, we highlighted the roles of superoxide ion and endogenous hydrogen peroxide, as well as the complex interplay between the metal and ROSs. These results enhance our understanding of the metallothionein system in ciliates and suggest that ROSs may be a primary evolutionary driver for the selection of these proteins in nature.

Improved Photocatalytic Activity of Dion-Jacobson-Type Tantalate Perovskites Modified with FeCl2.

A rapid and feasible approach was used to develop visible-light-driven-type Dion-Jacobson perovskites by the modification of the RbLaTa2O7 host (RbLTO) with FeCl2 through the molten salt route. X-ray diffraction (XRD) characterization showed that FeCl2-modified layered perovskite (e.g., Fe@RbLTO) preserved its lamellar structure. SEM micrographs confirmed the layered morphology of both RbLTO and Fe@RbLTO perovskite materials. The UV-Vis spectra illustrated a significant red shift of the absorption edge after Fe2+ modification, with the band gap energy reducing from 3.88 to 1.82 eV. H2-TPR measurements emphasized the anchorage of Fe2+ species located on the surface of the layered perovskite as well as in the interlayer space. The synthesized materials were valorized as photocatalysts for the degradation of phenol under both Xe lamp and simulated solar irradiation (SSL) conditions. The photocatalytic reaction follows first-order kinetics. By-product formations during phenol (Ph) degradation were identified and quantified using high-performance liquid chromatography (HPLC). Hydroquinone, 1,2-dihydroxi-benzene, benzoquinone, and pyrogallol were identified as the main Ph degradation intermediates. Pristine RbLaTa2O7 exhibited a phenol conversion value of about 17% using an Xe lamp, while a ≈ 11% conversion was achieved under SSL. A substantial increase in Ph conversion and selectivity was perceived after Fe2+ modification. Fe@RbLTO demonstrated superior photocatalytic performances (43% conversion of phenol under an Xe lamp, and 91% selectivity to aromatic intermediate compounds) at optimized reaction conditions. The stability of the Fe@RbLTO photocatalyst when exposed to an Xe lamp was also assessed. These results suggest that the existence of iron species on the layered perovskite's surface is responsible for the improved redox properties of Fe@RbLTO, resulting in a valuable material for environmental applications.

An ultra-sensitive bimetallic based electrochemical sensor for analysis of total iron, total dissolved iron, and granular iron in coastal water

Different iron species play crucial roles in the biogeochemical cycle, so their determination is important. Electrochemical methods are among the most promising and easiest methods for the rapid on-site determination of different iron species. In this study, a new electrode—Au–Bi/ITO—based on the commercial indium tin oxide (ITO) electrode was etched and functionalized with bismuth nanoparticles (BiNPs) and gold nanoparticles (AuNPs) nanocomposites for voltammetric analysis of iron species in coastal water. After etching, the ITO electrode exhibits a higher number of attachment sites for the nanomaterials, thereby improving the stability of the resulting electrode, and the introduction of the nanomaterials improves the sensitivity of the electrode, making it easier to realize on-site detection. Under the synergistic effect of the two nanomaterials, the Au-Bi/ITO electrode showed excellent performance for the determination of different iron species in coastal water. Under the optimal conditions, the Au-Bi/ITO electrode peak current was linear in the concentration range from 5 nM to 1.5 μM with an ultralow detection limit of 1.4 nM. The results are consistent with certified values when the electrode is used for the determination of Fe(III) in certified reference materials. In summary, the Au-Bi/ITO electrode, with its high stability and sensitivity, has been successfully used for the direct determination of different Fe(III) species in coastal water via cathodic stripping voltammetry. This electrode is simple to prepare, easy to use, economical, and highly promising for future applications involving the rapid on-site detection of different iron species.

Curcumin pretreatment attenuates myocardial ischemia/reperfusion injury by inhibiting ferroptosis, autophagy and apoptosis via HES1.

The early restoration of hemodynamics/reperfusion in acute myocardial infarction (AMI) is an effective therapeutic strategy to reduce sudden death and improve patient prognosis. However, reperfusion induces additional cardiomyocyte damage and cardiac tissue dysfunction. In this context, turmeric‑derived curcumin (Cur) has been shown to exhibit a protective effect against myocardial ischemia/reperfusion injury (I/RI). The molecular mechanism of its activity, however, remains unclear. The current study investigated the protective effect of Cur and its molecular mechanism via in vitro experiments. The Cell Counting Kit‑8 and lactate dehydrogenase (LDH) assay kit were used to assess the cell viability and cytotoxicity. The contents of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase, glutathione (GSH)/glutathione disulfide (GSSG), total iron, ferrous iron, caspase‑3 and reactive oxygen species (ROS) were measured using an appropriate kit. Western blotting was used to detect the expression of relevant proteins. The levels of apoptosis, mitochondrial permeability transition pore (MPTP) opening, and mitochondrial membrane potential (MMP) were detected by flow cytometry. The study findings indicated that anoxia/reoxygenation (A/R) injury significantly decreased cell viability, increased in LDH and caspase‑3 activities, induced ferroptosis, increased apoptosis and overactivated autophagy. However, pretreatment with Cur or ferrostatin‑1 (Fer‑1, a ferroptosis inhibitor) significantly increased A/R‑reduced cell viability, SOD, glutathione peroxidase activity, GSH/GSSH ratio and HES1 and glutathione peroxidase 4 protein expression; attenuated A/R‑induced LDH, MDA, total iron, ferrous iron, prostaglandin‑endoperoxide synthase 2 protein expression and prevented ROS overproduction and MMP loss. In addition, Cur inhibited caspase‑3 activity, upregulated the Bcl‑2/Bax ratio, reduced apoptotic cell number and inhibited MPTP over‑opening. Furthermore, Cur increased P62, LC3II/I, NDUFB8 and UQCRC2 expression and upregulated the p‑AMPK/AMPK ratio. However, erastin (a ferroptosis activator), pAD/HES1‑short hairpin RNA, rapamycin (an autophagy activator) and Compound C (an AMPK inhibitor) blocked the protective effect of Cur. In conclusion, Cur pretreatment inhibited ferroptosis, autophagy overactivation and oxidative stress; improved mitochondrial dysfunction; maintained energy homeostasis; attenuated apoptosis; and ultimately protected the myocardium from A/R injury via increased HES1 expression.

Iron hematite-magnetite composite supported on mesoporous SBA-15 synthesized by using silica from cogon grass as a solid catalyst in phenol hydroxylation

Phenol hydroxylation involves the oxidation of phenol (C6H5OH) using hydrogen peroxide (H2O2) to yield benzenediol (C6H4(OH)2), mainly catechol (CTL) and hydroquinone (HQ). These products are in high demand in the pharmaceuticals industry sector. Thus, it is still worth investigating for further improvement in terms of heterogeneous iron catalysts. Herein, this research focuses on an iron hematite (Fe2O3)-magnetite (Fe3O4) composite catalyst supported on SBA-15 using silica from cogon grass for phenol hydroxylation. The extracted silica exhibited a fine white powder appearance and an amorphous structure, used as a silica source for SBA-15 synthesis. After catalyst preparation, the presence of Fe2O3, Fe3O4, and Fe2O3-Fe3O4 composite on SBA-15 was confirmed by using X-ray absorption near-edge structure (XANES). X-ray photoelectron spectroscopy (XPS) analysis provided insights into the surface of the catalyst, revealing that Fe2O3-Fe3O4/SBA-15 had the highest dispersion of iron species. In terms of catalytic performance, Fe2O3-Fe3O4/SBA-15 displayed the highest conversion of 88 % and HQ selectivity of 46 % compared with lone Fe3O4/SBA-15 or Fe2O3 /SBA-15. The magnetic separation approach demonstrated the easy separation of catalysts containing Fe3O4. Reusability studies showed that Fe2O3-Fe3O4/SBA-15 maintained its activity up to the 4th cycle, suggesting minimized iron leaching compared to Fe3O4/SBA-15. Overall, this study provides insights into the catalytic performance of phenol hydroxylation and iron-based catalysts, emphasizing the potential of Fe2O3-Fe3O4/SBA-15 as an effective and reusable catalyst.

Non-radical oxidation driven by iron-based materials without energy assistance in wastewater treatment.

Chemical oxidation is extensively utilized to mitigate the impact of organic pollutants in wastewater. The non-radical oxidation driven by iron-based materials is noted for its environmental friendliness and resistance to wastewater matrix, and it is a promising approach for practical wastewater treatment. However, the complexity of heterogeneous systems and the diversity of evolutionary pathways make the mechanisms of non-radical oxidation driven by iron-based materials elusive. This work provides a systematic review of various non-radical oxidation systems driven by iron-based materials, including singlet oxygen (1O2), reactive iron species (RFeS), and interfacial electron transfer. The unique mechanisms by which iron-based materials activate different oxidants (ozone, hydrogen peroxide, persulfate, periodate, and peracetic acid) to produce non-radical oxidation are described. The roles of active sites and the unique structures of iron-based materials in facilitating non-radical oxidation are discussed. Commonly employed identification methods in wastewater treatment are compared, such as quenching, chemical probes, spectroscopy, mass spectrometry, and electrochemical testing. According to the process of iron-based materials driving non-radical oxidation to remove organic pollutants, the driving factors at different stages are summarized. Finally, challenges and countermeasures are proposed in terms of mechanism exploration, detection methods and practical applications of non-radical oxidation driven by iron-based materials. This work provides valuable insights for understanding and developing non-radical oxidation systems.

Time-dependent redistribution of soil arsenic induced by transformation of iron species during zero-valent iron biochar composites amendment: Effects on the bioaccessibility of As in soils

Zero-valent iron biochar composites (ZVI/BC) are considered as effective amendments for arsenic (As)-contaminated soils. However, the mechanisms of transformation of various soil As species during ZVI/BC amendments remain unclear. This study investigated As transformation in four soils (namely, GX, ZJ, HB, and HN) treated with ZVI/BC for 65 days under two soil moisture conditions, unsaturated and oversaturated. Results showed that the 65-day treatment was divided into two stages based on the variation of labile As content. Within 2 days (stage 1), ZVI/BC addition quickly reduced labile As content by 5.91–90.3 % in soils under unsaturated conditions. During days 2–65 (stage 2), labile As ultimately decreased by 0.06–0.31 mg/kg in GX, ZJ, and HB while increasing by 22.1 mg/kg in HN soil, due to its lower pH value and Fe content. The variations of labile As were attributed to changes in multiple Fe minerals and associated As species. In stage 1, the corrosion of ZVI/BC generated amorphous Fe oxides to immobilize labile As, resulting in the accumulation of meta-stable As. In stage 2, amorphous Fe oxides were transformed into crystalline Fe oxides, resulting in the release and re-precipitation of As along with transformation, thus redistributing immobilized As into labile and stable As, which was evidenced by multiple methods, including chemical extraction, XRD, and TEM-EDX. The elevated soil moisture condition would enhance the corrosion of ZVI/BC in stage 1, further forming a reductive environment to facilitate the transformation of Fe minerals in stage 2. Besides, As bioaccessibility in soils was reduced by 10.8–38.7 % after ZVI/BC treatment in in-vitro gastrointestinal simulations. Overall, our study revealed the time-dependent transformation mechanism of soil As species and associated Fe minerals under different soil moisture with ZVI/BC treatments, and highlighted the effectiveness of ZVI/BC as a long-term amendment for As-contaminated soils.

Fe-ZSM-5 outperforms Al-ZSM-5 in paraffin cracking by increasing the olefinicity of C3-C4 products

Iron-modified Al-ZSM-5 increases selectivity to propene, a key petrochemical resulting from fluid catalytic cracking (FCC). However, the type and role of active iron species remain unclear, hindering efforts to streamline the design of selective FCC additives. Here, we investigated Al-free Fe-ZSM-5 catalysts containing iron species in the form of framework Fe3+, extra-framework Fe3+, oxidic clusters, and oxide micro aggregates in n-octane cracking (FCC model) to assess their effect on catalytic cracking. DR-UV–Vis spectroscopy, 57Fe Mössbauer Spectroscopy, FTIR studies of pyridine adsorption, and n-octane cracking tests at 500 °C revealed that framework-associated coordinatively unsaturated Fe3+ species, which induce strong Lewis acidity, are responsible for paraffin cracking initiation, whereas bulk iron oxides on the zeolite surface are inactive. In comparison with Al-ZSM-5, Fe-ZSM-5 increases the olefinicity of the valuable C3-C4 fractions (selectivity to propene and butenes) and promotes aromatization reactions due to the lower relative strength of Fe-induced Brønsted acid sites and dehydrogenation properties. As shown by our 57Fe Mössbauer study (performed at −269 °C) of the catalyst in calcined, spent, and regenerated states, Fe-ZSM-5 deactivation is associated with the loss of tetrahedrally coordinated Fe3+ species. Therefore, tuning Fe-ZSM-5 C3-C4 selective FCC additives requires stabilizing framework Brønsted and framework-associated Lewis acid sites while decreasing the concentration of iron oxide species. Ultimately, these findings may enable us to meet the demand for propene derived from FCC cracking, which is expected to grow in the foreseeable future.

Treatment of sludge hydrothermal carbonization wastewater by ferrous/sodium percarbonate system: Effect of wastewater composition and role of coagulation and oxidation

It is crucial to explore the effect of complex wastewater compositions on the ferrous/sodium percarbonate (Fe(Ⅱ)/SPC) system and the role of oxidation-coagulation in designing water treatment processes. This study employed redundancy analysis to investigate the effects of wastewater constituents on oxidation and coagulation. Raman analysis, X-ray Photoelectron Spectroscopy, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry were used to determine the roles of oxidation and coagulation in the system. The results showed that sulfates and phosphates formed amorphous complexes with iron species via coprecipitation, thereby promoting coagulation to remove organics. Some heavy metals can also be removed by coagulation. The co-activation of SPC by pre-existing transition metals and the added Fe(Ⅱ) facilitated the oxidative removal of organics, while chloride and arsenic were the main inhibitory inorganic substances in the system. Aromatic compounds mainly promoted coagulation, polysaccharides promoted oxidation, humic acid promoted oxidation and coagulation, and C=C/C=O inhibited the Fe(Ⅱ)/SPC system. The oxidation process removed graphitic structures and unsaturated organic matter in the region of (O/C, H/C) = (0.2–0.4, 0.9–2.0) through free radicals and generated amorphous carbon structures and saturated organic matter in the region of (O/C, H/C) = (0.3–0.7, 1.2–1.9). The coagulation process removed aromatic organics with 2–5 rings and unsaturated organics in the region of (O/C, H/C) = (0.2–0.6, 0.7–1.6) with oxygen-containing organics. The combined effects of coagulation and oxidation enhanced the removal efficiency of organic carbon by approximately 40%. This study facilitates the optimization of hydrothermal carbonization wastewater treatment and advanced oxidation processes.

Using iron speciation to track hydrocarbon migration in bleached rocks and its implications for reservoir reconstruction

Bleaching of red rock beds by hydrocarbons can provide valuable insights for hydrocarbon migration and reservoir transformation. This study investigated the bleaching effects of hydrocarbons on various rock types in the Dushanzi mud volcanic area. Bedrock and bleached samples of different lithologies, including mudstone, sandy mudstone and sandstone, were systematically collected and analyzed for their iron species, mineralogical and chemical compositions using Mössbauer spectroscopy, X-ray diffraction and X-ray fluorescence, respectively. The results indicate that the iron species of the studied samples were dominated by para-Fe3+ (from 44% to 76%), with variable contents of mag-Fe3+, para-Fe2+ and pyr-Fe2+. When compared to the related unbleached rocks, the bleached rocks exhibited a higher proportion of reduced Fe (para-Fe2+ and pyr-Fe2+). The pyr-Fe2+ in the sandstones and sandy mudstones was significantly higher than that of the mudstone interlayers. The observed variations in iron species were consistent with changes in mineralogical and chemical compositions, which can be correlated with the petrological properties of rocks. The increase of quartz and decrease of feldspar and carbonates in the bleached rocks could be attributed to the dissolution of feldspar and the subsequent secondary enlargement of quartz. Geofluids containing crude oils and natural gases preferentially dissolved K-feldspar over albite. The bleached rocks had a significant decrease in the proportion of kaolinite and a slight decrease in the proportion of chlorite, while the proportions of smectite and illite were increased. The dissolution of K-feldspar could provide sufficient K+ for the formation of illite, and the appearance of smectite in the bleached samples might be related to the dissolution of albite in an alkaline environment. The dissolution of carbonates and feldspar, along with the transformation of clay minerals, had a notable positive effect on the formation of secondary porosity, facilitating hydrocarbon migration. These findings provide valuable insights into the interactions between hydrocarbons and different lithologies, informing the impact of hydrocarbon migration on reservoir reconstruction in similar geological settings.

Mononuclear high-spin iron(III) phthalocyanines

2,9(or 10),16(or 17), 23(or 24)-Tetradecyloxycarbonylphthalocyaninatoiron, FeTDPc, and 2,3,9,10,16,17,23,24-octadecyloxycarbonylphthalocyaninatoiron, FeODPc, were synthesized and characterized. These compounds seem to be in trivalent iron high-spin state in solvents such as chloroform, dichloromethane, benzene, and chlorobenzene, although their counter anion could not be detected by elemental analyses. They react with strong bases such as pyridine and imidazoles to form their mono- and subsequently their di-base complexes with formation constant of >106 and < 200 dm3 mol−1, respectively, in dichloromethane at 20 °C. The resultant mono-adducts appear to be trivalent iron low-spin while the di-base adducts are bivalent iron low-spin state complexes. The addition of ca. 10–30 equivalent of tetrabutylammonium-chloride or -bromide (electrolyte) to the solution containing FeTDPc or FeODPc, causes their spin-state change from iron(III) high to low-spin state. In a solid power state, however, both FeTDPc and FeODPc exist as a mixture of high-spin iron(III)- and intermediate-spin iron(II) species. Strangely, when these compounds are dissolved in polystyrene, i.e. each molecules are isolated from each other, the signals originated from the iron(II) component disappear.