Search Results (465)

This study examined the leaching behavior of copper and iron from a sphalerite concentrate in sulfuric acid utilizing an ensemble MnO₂–KI oxidizing system. The temperature was shown to significantly influence the leaching kinetics, with the efficiency notably improving between 40 °C and 80 °C. The introduction of KI affected the balance between sulfur passivation and oxidant availability, facilitating increased leaching efficiencies. At 3 wt% KI, maximum recoveries of 82.1% Cu and 85.3% Fe were achieved, which indicates a notable decrease in surface passivation. Kinetic study analysis revealed low activation energies of 28.90 kJ mol⁻¹ for copper and 18.94 kJ mol⁻¹ for iron, indicating that both processes proceed readily at moderate temperature regimes. Despite being diffusion-controlled, the mechanisms of dissolution are different: iron leaching is more complicated, involving pyrite oxidation, sulfur layer formation, transformation to marcasite, and ultimately iron (III) release, whereas copper leaching involves direct interaction of chalcopyrite with the oxidants, similar to the behavior of sphalerite. Full article

The pathogenesis of Friedreich’s ataxia (FRDA) remains poorly understood. The most important event is the deficiency of frataxin, a protein related to iron metabolism and, therefore, involved in oxidative stress. Studies on oxidative stress markers and gene expression in FRDA patients have yielded inconclusive results. This is largely due to the limited number of studies, small sample sizes, and methodological differences. A notable finding is the decreased activity of mitochondrial respiratory chain complexes I, II, and III, as well as aconitase, in endomyocardial tissue. In contrast, numerous studies in experimental models of FRDA (characterized by frataxin deficiency) have shown evidence of the involvement of oxidative stress in cellular degeneration. These findings include increased iron concentration, mitochondrial dysfunction (with reduced respiratory chain complex activity and membrane potential), and decreased aconitase activity. Additionally, there is the induction of antioxidant enzymes, reduced glutathione levels, elevated markers of lipoperoxidation, and DNA and carbonyl protein oxidation. The expression of NRF2 is decreased, along with the downregulation of PGC-1α. Therefore, it is plausible that antioxidant treatment may help improve symptoms and slow the progression of FRDA. Among the antioxidant treatments tested in FRDA patients, only omaveloxolone and, to a lesser extent, idebenone (particularly for cardiac hypertrophy) have shown some efficacy. However, many antioxidant drugs have shown the ability to reduce oxidative stress in experimental models of FRDA. Therefore, these drugs may be useful in treating FRDA and are likely candidates for future clinical trials. Future studies investigating oxidative stress and antioxidant therapies in FRDA should adopt a prospective, multicenter, long-term, double-blind design. Full article

Fiber-based black-and-white developing-out papers (DOPs) were among the most widely used photographic supports of the 20th century. Their broad use, structural complexity, and range of surface finishes, alongside evolving manufacturing practices, underscore the importance of understanding their material composition for authentication, dating, and conservation purposes. This study presents a multi-analytical characterization of three DOP sample sets: two from Ilford (ca. 1950) and one from Kodak (1972), complementing previous research with a deeper insight into general features, stratigraphy, and composition. Initial non-sampling techniques, including thickness measurements, colorimetry, optical microscopy, and UV–visible induced fluorescence, were used to classify papers into visually and physically distinct groups. This informed a targeted sampling strategy for further stratigraphic and compositional analysis using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray fluorescence (XRF), Raman spectroscopy, and fiber/pulp identification tests. Significant differences were observed in base tint, surface gloss, optical brightening agents, fillers, and fiber content. Notable findings include the presence of iron (III) oxide–hydroxide pigment in Ilford cream papers, anatase titanium dioxide (TiO₂) in a baryta-less Ilford sample, and the shift to more uniform tones and mixed pulps in Kodak papers by the 1970s. These results offer valuable insights into historical manufacturing and support improved dating and characterization of photographic papers. Full article

Blast furnace (BF) ironmaking remains one of the most efficient countercurrent processes; however, achieving further CO₂ emission reductions through conventional methods is increasingly challenging. Currently, BF ironmaking emits approximately 2.33 tonnes of fossil-derived CO₂ per tonne of crude steel cast. Integrating briquettes composed of biochar and in-plant fines into the BF process offers a promising short- to medium-term strategy for lowering emissions. This approach enables efficient recycling of fine residues and the substitution of fossil reductants with bio-based alternatives, thereby improving productivity while reducing energy and carbon intensity. This study investigates the reduction behavior of (i) biochar mixed with pellet fines, (ii) various in-plant residues individually, and (iii) briquettes composed of biochar and in-plant fines. The reduction rate of biochar–pellet fine mixtures was found to depend on biochar type, with pyrolyzed pine sawdust exhibiting the highest reactivity, and pyrolyzed contorta wood chips the lowest. A correlation between reduction rate and the alkali index of each char was established, although other factors such as char origin and physical properties also influenced reactivity. The effect of biochar addition (0, 5, and 10 wt.%) on the reduction of steelmaking residues was also studied. In general, biochar enhanced the reduction degree and shifted the reaction onset to lower temperatures. The produced briquettes maintained high mechanical integrity during and after reduction, regardless of biochar origin. Thermogravimetric and XRD analyses revealed that mass loss initiates with the dehydroxylation of cement phases and release of volatiles, followed by carbonate decomposition and reduction of higher oxides above 500 °C. At temperatures ≥ 850 °C, the remaining iron oxides were further reduced to metallic iron. Full article

As an important agricultural ecosystem, greenhouse gas (GHG) emissions and arsenic (As) mobilization in rice paddy fields have gained significant attention on climate change and food safety. There is a certain correlation between the GHG and As migration in rice paddy fields. The oxidation of methane in paddy fields can provide electrons for the reduction and release of arsenate. Nitrate in rice paddy soil can promote the fixation of As by oxidizing Fe (II) to form iron oxide–As complexes or directly oxidize As (III) to As (V) to reduce the toxicity of As. However, incomplete denitrification of nitrate can lead to the emission of N₂O. This review systematically expounds the research advances, influencing factors and simultaneous mitigation measures of GHG emissions and As mobilization in rice paddy fields. It focuses on discussing the influence mechanisms of soil physical and chemical properties, water management measures, fertilization methods, and the addition of soil conditioner on As migration and GHG emission, and it looks forward to future research directions. It aims to provide a theoretical basis and practical guidance for reducing the risk of As contamination in rice fields, reducing GHG emission, and achieving sustainable development of rice production. Full article

The development of stable and efficient heterogeneous Fenton oxidation for organic pollutant degradation is crucial to avoid iron sludge formation and cumbersome filtration processes. In this study, iron oxide/carbon aerogel was prepared via the sol–gel method, freeze-drying, and high-temperature carbonization using iron nitrate heptahydrate, ammonium hydroxide, and cellulose as raw materials, with polyvinylimine serving as the crosslinking agent. To enhance the pH adaptability of the catalyst, copper and cerium elements were introduced. The characterization results demonstrate the iron (III) oxide within the carbon aerogel, achieving phenol degradation efficiency exceeding 95% within 120 min. Meanwhile, the introduction of copper and cerium accelerated the degradation of phenol while maintaining a certain catalytic degradation effect at pH 5-7. In addition, the catalyst exhibited excellent recyclability, retaining 85% of its initial degradation efficiency after five reaction cycles. This work offers a new method for the development of heterogeneous Fenton catalysts. Full article

This study investigates the phenolic composition and antioxidant potential of root extracts from three Opuntia ficus-indica varieties (green, red, and orange) using ultra-high-performance liquid chromatography coupled with diode array detection and electrospray ionization–tandem mass spectrometry (UHPLC-DAD-ESI-MS/MS). Phenolic compounds were extracted with a hydromethanolic solvent and quantified by spectrophotometric assays, while antioxidant activity was assessed through DPPH, ABTS, iron III reduction, hydroxyl radical, and nitric oxide scavenging methods. A total of 26 compounds were identified, including piscidic acid, epicatechin-3-O-gallate, and isovitexin, with several phenolics newly reported for O. ficus-indica roots. The green and red varieties showed the highest phenolic contents (up to 147.82 mg/g extract) and strong antioxidant capacity, particularly in ABTS (IC₅₀ = 29.38 μg/mL) and hydroxyl radical inhibition (>90%). Relative Antioxidant Capacity Index (RACI) analysis confirmed a consistent correlation between phenolic/flavonoid content and antioxidant efficacy. These findings highlight the analytical relevance of UHPLC-DAD-ESI-MS/MS for profiling underutilized plant matrices and support the potential use of O. ficus-indica root extracts as natural sources of bioactive compounds for pharmaceutical and biomedical applications. Full article

This paper presents the results of a study on the development of a processing technology for pyrite–cobalt concentrates to obtain iron oxide pigments (Fe₂O₃ and Fe₃O₄) via high-temperature hydrolysis. It was found that, in a single operation, the concentrate can be effectively purified from lead, zinc, and copper, yielding an iron–nickel–cobalt product suitable for further processing by standard technologies, such as smelting into ferronickel. The scientific originality of research concludes in a mechanism of stepwise selective chloride volatilization, which was established as follows: stage I (500–650 °C)—removal of lead; stage II (700–750 °C)—chlorination of copper and iron; stage III (850–900 °C)—volatilization of nickel and cobalt. Microprobe analysis of the powders obtained from high-temperature hydrolysis of FeCl₂·4H₂O and FeCl₃·6H₂O revealed the resulting Fe₃O₄ and Fe₂O₃ powders with particle sizes 50 μm and 100 μm. A visual color palette was created, corresponding to different Fe₃O₄/Fe₂O₃ ratios in the pigment composition—ranging from black (magnetite) to red (hematite)—and potential application areas. For the first time, the new technological scheme was proposed of pigments Fe₂O₃ and Fe₃O₄ production from pyrite–cobalt concentrates via combination of oxidized roasting with subsequent chlorination and high-temperature hydrolysis of the products. Full article

Abiotic processes have ramifications in wastewater treatment, in situ degradation of organic matter, and cycling of nutrients in wetland ecosystems. Experiments were conducted to investigate abiotic oxidation of organic compounds (lactate) as a function of electron acceptors (ferric citrate and hydrous ferric oxide (HFO), media composition, and pH under anaerobic conditions, using sodium bicarbonate as the buffering agent. Dissolved inorganic carbon (DIC) was used as a proxy for the oxidation of substrates. HFO media generated more DIC compared to ferric citrate containing media. Light and pH had major roles in the oxidation of lactate in the presence of ferric iron. Under dark conditions in the presence or absence of Fe(III), the DIC produced was low in all pH conditions. Inhibition of DIC production was also observed upon photo exposure when Fe (III) was absent. Isotopically, the system showed initial mixing between the bicarbonate and the carbon dioxide produced from oxidation later being dominated by carbon isotope value of lactate used. These redox conditions align with previous studies suggesting cleavage of organic compounds by hydroxyl radicals. The slower redox processes observed here, compared to previous studies, could be due to the scavenging effect of chloride ion on the hydroxyl radical. Full article

Molasses, a by-product of raw sugar production, is widely used as a cost-effective carbon and nutrient source for industrial fermentations, including the production of baker’s yeast (Saccharomyces cerevisiae). Due to the cost and limited availability of molasses, efforts have been made to replace molasses with cheaper and more readily available substrates such as corn syrup. However, the quality of dry yeast drops following the replacement of molasses with corn syrup, despite the same amount of total sugar being provided. Our understanding of how molasses replacement affects yeast physiology, especially during the dehydration step, is limited. Here, we examined changes in gene expression of a strain of baker’s yeast during fermentation with increasing corn syrup to molasses ratios at the transcriptomic level. Our findings revealed that the limited availability of the key metal ions copper, iron, and zinc, as well as sulfur from corn syrup (i) reduced their intracellular storage, (ii) impaired the synthesis of unsaturated fatty acids and ergosterol, as evidenced by the decreasing proportions of these important membrane components with higher proportions of corn syrup, and (iii) inactivated oxidative stress response enzymes. Taken together, the molecular and metabolic changes observed suggest a potential reduction in nutrient reserves for fermentation and a possible compromise in cell viability during the drying process, which may ultimately impact the quality of the final dry yeast product. These findings emphasize the importance of precise nutrient supplementation when substituting molasses with cheaper substrates. Full article

Natural polymers, polysaccharides, demonstrate piezoelectric behavior suitable for force sensor manufacturing. Carrageenan hydrogel film with α-iron oxide particles can act as a piezoelectric polysaccharide-based force sensor. The mechanical impact on the hydrogel caused by a falling ball shows the impact response time, which is measured in milliseconds. Repeating several experiments in a row shows the dynamics of fatigue, which does not reduce the speed of response to impact. Through the practical experiments, we sought to demonstrate how theoretical knowledge describes the hydrogel we elaborated, which works as a piezoelectric material. In addition to the theoretical basis, which includes the operation of the metal and metal oxide contact junction, the interaction between the metal oxide and the hydrogel surfaces, the paper presents the practical application of this knowledge to the complex hydrogel film. The simple calculations presented in this paper are intended to predict the hydrogel film’s characteristics and explain the results obtained during practical experiments. Carrageenan, as a low-cost and already widely used polysaccharide in various industries, is suitable for the production of low-cost force sensors in combination with iron oxide. Full article

Background/Objectives: In the context of preclinical studies, we have hitherto showcased that a low-molecular-weight ruthenium(III) complex we named AziRu holds significant potential for further developments as an anticancer candidate drug. When appropriately converted into stable nanomaterials and delivered into tumor cells, AziRu exhibits superior antiproliferative activity, benefiting from a multimodal mechanism of action. The activation of regulated cell death (RCD) pathways (i.e., apoptosis and autophagy) has been proved in metastatic phenotypes, including triple-negative breast cancer (TNBC) cells. This study focuses on a bioengineered lipophilic derivative of AziRu, named PalmiPyRu, that we are currently developing as a potential anticancer drug in preclinical studies. When delivered in this way, AziRu confirms a multimodal mechanism of action in effectively blocking the growth and proliferation of TNBC phenotypes. Special focus is reserved for the activation of the ferroptotic pathway as a consequence of redox imbalance and interference with iron homeostasis, as well as the glutathione biosynthetic pathway. Methods: Human preclinical models of specific TNBC phenotypes and healthy cell cultures of different histological origin were selected. After in vitro treatments, cellular responses were carefully analyzed, and targeted biochemical and molecular biology experiments coupled to confocal microscopy allowed us to explore the antiproliferative effects of PalmiPyRu. Results: In this study, we unveil that PalmiPyRu can enter TNBC cells and interfere with both the iron homeostasis and the cystine-glutamate antiporter system Xc-, causing significant oxidative stress and the accumulation of lipid oxidation products. The increase in intracellular reactive free iron and depletion of glutathione engender a lethal condition, driving cancer cells toward the activation of ferroptosis. Conclusions: Overall, these outcomes allow us, for the first time, to couple the antiproliferative effect of a ruthenium-based candidate drug with the inhibition of the Xc- antiporter system and Fenton chemistry, thereby branding PalmiPyRu as an effective multimodal inducer of ferroptosis. Molecular mechanisms of action deserve further investigations, and new studies are underway to uncover how interference with Xc- controls cell fate, allowing us to explore the connection between iron metabolism regulation, oxidative stress and RCD pathways activation. Full article

The modern world has brought extensive socioeconomic and ecological changes. Urbanization in developing nations has significantly increased municipal solid waste, necessitating in-depth understanding of waste composition particularly in developing nations for sustainable management practices. This study aimed to classify and characterize waste while evaluating potential waste management methods. Mixed methods were used to examine landfilled waste from Soshanguve and Hatherley sites in Tshwane Metropolitan, South Africa, using techniques such as Fourier transform infrared spectroscopy, X-ray fluorescence, proximate, and ultimate analysis. Seasonal variations in waste components were analysed over two seasons. The study identified that both sites are predominantly composed of organic waste, accounting for over 42 wt.%, with moisture content of ~50 wt.%, and minimal recyclables (<5 wt.%). Seasonal variations in MSW were significant for glass (<4% increase), organic waste (<5% increase), while plastic decreased by ~7% during spring. The biodegradable waste showed high carbon (>50%) and oxygen (>40%) levels, low ash content (<18%), and calorific values of 15–19 MJ/kg. Biodegradables mainly contained oxides of calcium, silicon, iron (III), and potassium with chemical composition indicating functional groups that emphasize composting and energy recovery benefits. The research provides insights into sustainable waste management, revealing waste composition at Tshwane landfills, aiding informed decision-making for resource usage and environmental conservation. Full article

Nanotechnology plays an increasingly important role in the economy and human life, which means that more and more amounts of nanosubstances, including nanoparticles of metal oxides, together with wastewater, end up in the environment. This study aimed to study the impact of iron(III) oxide nanoparticles (n-Fe₂O₃), which have magnetic properties, on the efficiency of the Anammox wastewater treatment process. The results indicate that n-Fe₂O₃ in the range of low concentrations may have a positive effect on nitrogen metabolism, increasing the efficiency of NH₄-N removal to 98% in 120 min and at 30 °C. During the first 30 min of the process, when almost anaerobic conditions arose, nanoparticles of Fe₂O₃, stabilized the system by producing ROS. However, a constant control of TOC and pH is necessary because of the constant increase in the amount of organic compounds and H⁺ ions during the reaction. However, a longer contact of n-Fe₂O₃ with biomass causes the efficiency to decrease, and, as a result, the efficiency is lower compared to the system containing only Anammox. Full article

This paper aimed to evaluate the effect of cross-linking temperature on the rheological, mechanical, and thermal properties of CR/BR compositions cross-linked with zinc oxide, iron(III) oxide, or copper(II) oxide. Properties of CR/BR compounds were studied at four temperatures: 140, 160, 180, and 200 °C. The lowest activation energy of vulcanization was shown by blends cross-linked with ZnO, and the highest activation energy of vulcanization was shown by samples with Fe₂O₃. Blends cured with ZnO or Fe₂O₃ showed higher cross-linking activity than CuO. Higher temperatures enhanced the degree of cross-linking in the CR/BR composite cured with ZnO or CuO but slightly reduced it for the CR/BR/Fe₂O₃ vulcanizates. The highest tensile strength was observed for the CR/BR/Fe₂O₃ product. However, compositions cured with ZnO exhibited the best aging resistance. The CR/BR compounds cured with ZnO at high temperatures had the highest tear strength (16.8 N/mm), while samples containing CuO as a curing agent showed declining tear strength with temperature. DSC confirmed a single glass transition (~36 °C), indicating good elastomers dispersion. Infrared and SEM analyses confirmed effective cross-linking and blend compatibility. Full article