Iron Ions In Solution Research Articles

Carbon quantum dots of ginsenoside Rb1 for application in a mouse model of intracerebral Hemorrhage

After intracerebral hemorrhage (ICH) occurs, the overproduction of reactive oxygen species (ROS) and iron ion overload are the leading causes of secondary damage. Removing excess iron ions and ROS in the meningeal system can effectively alleviate the secondary damage after ICH. This study synthesized ginsenoside Rb1 carbon quantum dots (RBCQDs) using ginsenoside Rb1 and ethylenediamine via a hydrothermal method. RBCQDs exhibit potent capabilities in scavenging ABTS + free radicals and iron ions in solution. After intrathecal injection, the distribution of RBCQDs is predominantly localized in the subarachnoid space. RBCQDs can eliminate ROS and chelate iron ions within the meningeal system. Treatment with RBCQDs significantly improves blood flow in the meningeal system, effectively protecting dying neurons, improving neurological function, and providing a new therapeutic approach for the clinical treatment of ICH.

Investigation of the solid oxidizer effect on the metal geotechnology efficiency

Purpose. The research is aimed at increasing the useful component content in a pregnant solution during in-situ leaching (ISL) using a solid oxidizer and increasing the ferric iron concentration in the leaching solution based on laboratory research. Methods. Laboratory research is performed on a specially developed model electrolyzer for obtaining comparative data on divalent iron oxidation to trivalent iron and the change in the useful component content in a pregnant solution. Firstly, tests are conducted with a basic leaching solution, then on the oxidation of the leaching solution with a solid oxidizer in the form of a lead dioxide plate. Tests are conducted by changing sulphuric acid concentration within 5-50 g/l, amount of divalent iron ions in the solution from 0.5 up to 4.0 g, lead dioxide plate surface area from 19 to 76 cm2. The leaching time is up to 10 hours. Findings. The results of laboratory research on determining the oxidation degree of divalent iron ions and change in the oxidation-reduction potential (ORP) depending on the sulphuric acid concentration and on the initial concentration of divalent iron ions in the initial solution are presented. With a change in the sulphuric acid concentration from 5 to 50 g/l, the oxidation value of divalent iron ions increases from 26.5 to 96.5%, and with an increase in the initial solution concentration of divalent iron, the oxidation degree of divalent iron naturally decreases from 95.2 to 58.8%. In the initial leaching solution, the divalent solution concentration is 312 mg/l, and that of the trivalent solution is 288 mg/l. After oxidation with a solid oxidizer, the divalent and trivalent iron concentrations are 56 and 392 mg/l, respectively. In the course of further laboratory research using core materials from a uranium deposit, it has been revealed that when leaching with a basic solution, the uranium content in the pregnant solution is 19.36 mg/l, and when leaching with a solution after oxidation with a solid oxidizer, it is 27.9 mg/l, which is by 8.54 mg/l more. Originality. New dependences have been determined of the oxidation degree of divalent iron ions to trivalent one on the sulphuric acid concentration and on the initial concentration of divalent iron ions, as well as the useful component content in the pregnant solution on the leaching time when using a solid oxidizer. Practical implications. Using of a solid oxidizer, it is possible to increase the trivalent iron concentration in the leaching solution and the useful component content in the pregnant solution compared with the basic technology, thereby reducing the time of mining uranium reserves. Proposed technology is environmentally friendly, with low capital costs.

Purification, Characterization, and Ferrous Oxidation Kinetics of Iron Oxidase from Acidithiobacillus ferridurans

Iron oxidase was proposed to be the initial electron acceptor from the ferrous ion in the iron oxidation of the Acidithiobacillus genus for metal bioextraction; however, its most fundamental property of direct ferrous oxidation kinetics remains undetermined due to the confusion of reaction monitor method. Here, a recombinant iron oxidase from Acidithiobacillus ferridurans Riv11 was constructed, expressed, purified, characterized, and further used to investigate the kinetics and mechanism of ferrous oxidation. This protein is more stable in an acid solution than in a neutral solution. An infrared characteristic peak around 1050 cm−1 of the [Fe4S4] cluster was identified. The [Fe4S4] cluster does not affect the secondary structure of protein, but plays an important role in the stability of protein and strongly absorbs the intrinsic fluorescence of protein, resulting in a great loss of the fluorescence emission. The protein has far more absorbance than those of the iron ions in solution in the visible region; therefore, the maximum difference absorbance around 500 nm between the oxidized and reduced states of protein can be used to monitor the reaction of ferrous oxidation. Accordingly, the kinetic rate constant of the reaction was determined. Bioinformatics analysis and molecular simulation further revealed the underlying molecular mechanism that ferrous ions approach the protein at the edge of a large hydrophobic surface patch nearest to the [Fe4S4] cluster from a direction far from all positively charged residues, which enough enables an efficient electron transfer.

Selective leaching of base/precious metals from E-waste of cellphone printed circuit boards (EWPCB): Advantages and challenges in a case study

Complex materials, such as those contained in e-waste, offer new challenges for recovering metals of interest. This investigation exemplifies the difficulties encountered when treating multimetallic or refractory materials, from which specific values are to be separated and recovered. The case study involves the selective leaching of gold from e-waste printed circuit boards (EWPCB), containing ≈200 g Au per ton. To achieve a selective process, chemical inhibitors were employed; their function is to avoid the co-dissolution of base- metal impurities, which could accumulate in the leaching solutions and contribute to leaching agents' degradation, impeding gold extraction.Solutions of thiourea (CS(NH2)2) and hydrogen peroxide (H2O2) were proposed to leach the gold; however, strong competition for these reagents, especially by copper and iron contained in the EWPCB, completely blocked gold dissolution. After a pretreatment that removed the bulk of selected base metals (elimination of 98% of Cu and > 80% of Fe, Zn and Ni), the presence of these and other metals still obstructed gold extraction. The incorporation of chemical inhibitors was analyzed.Unfortunately, although oxalic acid did diminish the presence of both copper and iron ions in solution, it fomented the competitive leaching of aluminum and tin. The CS(NH2)2-H2O2-C2H2O4 system at ambient temperature (25 °C) allowed a gold recovery of ≈87% by suppressing most of the base metal interference. Not only the dissolution of the metal of interest is important, but also the fate of the accompanying metals and constituents.

PH Dependance of Scorodite Formation in As(V) Solution Using Magnetite as the Solid Iron Source

Arsenic-containing wastewater, which is mainly generated in nonferrous metal-smelting plants, threatens the natural environment and human health owing to its high toxicity and mobility. A promising arsenic immobilization method to solve this problem is to immobilize arsenic as scorodite. In this study, the method of scorodite synthesis using magnetite as the iron source was investigated, which can be performed using low-cost materials under atmospheric pressure without using an autoclave. The generation and crystallization behaviors of the intermediate of the gel-like precursor of scorodite were investigated by monitoring the concentration of each iron ion in solution and characterizing the precipitate. By clarifying the effect of the solution pH for each reaction step, the mechanism and suitable conditions of this process are discussed.

Resource-recycling and energy-saving innovation for iron removal in hydrometallurgy: Crystal transformation of ferric hydroxide precipitates by hydrothermal treatment

In hydrometallurgy industry, the accumulation of iron removal residues containing heavy metal elements and toxic elements poses great threats to ecological systems. We propose a novel method to prevent the production of hazardous iron removal residues: firstly, neutralization precipitation is used to purify iron ions in solution; after sedimentation of the obtained suspension, only dense underflow is subjected to hydrothermal reaction, in which ferric hydroxide transforms into hematite crystal. Results showed that ferric hydroxide precipitated into a thin sedimentation layer at temperature greater than 60 °C. For hydrothermal treatment of the sedimentation layer, a high hydrothermal reaction temperature was conducive to complete transformation of ferric hydroxide into hematite. The precipitated ferric hydroxide firstly changed from the crystallite of goethite or lepidocrocite to amorphous particles, and then gradually formed spherical α-Fe2O3 monocrystalline with diameter of around 50 nm, as indicated by TEM and XRD results. At 200 °C, hematite precipitates with iron content of about 65% can be obtained. For iron-containing zinc/nickel/cobalt sulfate solution, controlling hydrothermal reaction temperature and acidity of the underflow solution can effectively avoid the generation of zinc/nickel/cobalt hydroxides or subsulfates in the hematite precipitates, thereby significantly reducing the loss of those valuable metals.

Comparison of the behavior of ZVI/carbon composites from both commercial origin and from spent Li-ion batteries and mill scale for the removal of ibuprofen in water

Zero valent iron/carbon composites were successfully synthesized from commercial iron oxide and graphite (ZVI/C) and also by using graphite obtained from spent Li-ion batteries and iron oxide from mill scale (ZVI/C-X) as a new approach for the valorization of these waste. The composites were synthesized through carbothermic reactions and tested as catalysts for the degradation of ibuprofen from water by Fenton reaction. The optimal conditions for synthesizing ZVI/C composites were a temperature of 1000 °C maintained for 2 h. The structural, and textural features of ZVI/C with different ZVI mass ratios were characterized by different techniques. ZVI/C composites with higher ZVI mass ratios showed higher degradation rates for the removal of ibuprofen both in presence and absence of H2O2. Moreover, ZVI/C-X composite, obtained from industrial waste, showed activity even after four consecutive cycles of use with very low concentration of iron ions in solution after reaction (4.8 mg L−1 after 4 h), which supports the high stability and low Fe-lixiviation of ZVI/C-X composite. The results of this study prove the possibility of synthesizing composites using graphite from spent Li-ion batteries and iron oxide from mill scale, and their potential for the degradation of ibuprofen in water, with comparable activities to those obtained from commercial feedstocks.

Simply synthesized N-doped carbon supporting Fe3O4 nanocomposite for high performance supercapacitor

Metal oxides have attracted a lot of attention in energy conversion and storage due to their high capacitance. In this work, the polydopamine nanospheres (PDA) was used to adsorb iron ions in solution, and then the mixture was calcined at high temperature to form nitrogen doped (N-doped) carbon (NCSs) supporting Fe3O4 (NCSs@Fe3O4). The as-prepared nanocomposite carbonized at 750 °C with large specific surface area of 349.5 m2 g−1 and large number of pores distributed at 2–10 nm, exhibiting excellent electrochemical performance. Its specific capacitance can reach 206 F g−1 at the current density of 1 A g−1, and still keep 95% of the initial capacity after 5000 cycles. The NCSs@Fe3O4//NCSs asymmetric supercapacitor was constructed using NCSs@Fe3O4 as cathode electrode material and NCSs as anode electrode material. The results of a series of tests indicated that the asymmetric supercapacitor has excellent capacitive performance, suggesting that NCSs@Fe3O4 composite is a favorable candidate for supercapacitor.

Sulfur content reduction of iron concentrate by reverse flotation

ABSTRACT In this study, the desulphurization of iron ore concentrate using reverse flotation was investigated. In this paper first, behavior of the flotation of both pure – pyrite and iron oxides-pyrite with xanthate has been examined based on micro-flotation results and zeta-potential measurements. Then, an effort has been made to investigate the effect of pH, chemical reagent dosages, impeller speed, pulp density, flotation time and conditioning time parameters on desulphurization of actual iron ore concentrate using lab-scale mechanical flotation cell. Results of zeta-potential measurements displayed that iso-electric points (IEP) for pure and iron oxides-pyrite were around pH 7 and 8, respectively. Based on the micro-flotation results, the recoveries were highly dependent on pH. Both pyrite types showed high recoveries at pH 4.75 to 8, but in the flotation of iron oxides-pyrite, partial depression was found in the pH range of 6–7. The presence of iron ions in solution considerably depressed iron oxide-pyrite flotation in the pH range of 2.5–3. Recovery of both pyrites decreased dramatically when going from pH 10, due to the formation of iron hydroxides and the instability of dixanthogen. According to the data obtained from batch flotation tests, the maximum recovery of total sulfur was achieved when the operational parameters were set to the PAX dosage 200 gr/t, MIBC dosage 150 gr/t, CuSo4 75 gr/t, impeller speed 1500 rpm, pH 7.5, flotation time 7 min and pulp density 30%. With these optimum parameters, final concentrate with the grade of 69.48% Fe and 0.1% S was obtained.

Semiholoenzyme optimizes activity and stability of a hyperthermostable iron-superoxide dismutase

Metal ion coordination is an essential step for the maturation of metalloenzymes. Generally, the metal coordination sites are thought to be fully occupied to achieve the maximum activity and stability. In this research, we compared the structural features, activity and stability of the apo-, semiholo- and holo-forms of a hyperthermostable tetrameric Fe-superoxide dismutase (SOD). Strikingly, the three forms of enzymes had similar compact tetrameric structures. Removal of iron ions destabilized subunit-subunit interactions during guanidine hydrochloride-induced unfolding. The partially metalized semiholoenzyme possessed most of the activity and identical hyperthermostability of the holoenzyme, but weaker propensity to aggregate. Furthermore, both of the iron content and activity of the semiholoenzyme were unaffected by a 200-fold excess iron ions in solutions, suggesting that conformation of the apo-subunits were forced to the close state by the iron-containing subunits. These observations suggest that fully metalized enzyme is probably nonessential for multimeric metalloenzymes and the semiholoenzyme may be a better choice. The unique properties of semiholoenzyme also provide the organisms a compromised solution to survival under metal deficiency conditions.

Oxalate enhanced degradation of Orange II in heterogeneous UV-Fenton system catalyzed by Fe3O4@γ-Fe2O3 composite

Oxalate enhanced mechanism of Fe3O4@γ-Fe2O3 was developed to provide novel insight into catalytic process regulation of iron oxide catalysts in heterogeneous UV-Fenton system. And the iron oxide composite of Fe3O4@γ-Fe2O3 was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fourier transform infrared (FTIR) spectroscopy and nitrogen adsorption-desorption isotherms. The results showed that large amount of iron could be leached from catalyst in the presence of oxalate, which promoted the homogeneous UV-Fenton reactions in solution. Orange II degradation could be significantly enhanced with the increase of the ratio of homogeneous UV-Fenton process to heterogeneous UV-Fenton process. The optimum concentration of oxalate determined by experiment was 0.5 mM in oxalate enhanced heterogeneous UV-Fenton system. On this condition, the pseudo-first-order rate constant value of Orange II degradation was 0.314 min−1, which was 2.3 times as high as that in heterogeneous UV-Fenton system. The removal rates of color and TOC were 100% and 86.6% after 20 min and 120 min treatment, respectively. In addition, the iron ions in solution could be almost completely adsorbed back to the catalyst surface in later degradation stages of Orange II. During the recycle experiments, the results showed that the increase of pH in solution and the sorption of intermediates on the catalyst surface would hinder oxalate enhanced process and lead to a decrease of degradation rate of Orange II in oxalate enhanced heterogeneous UV-Fenton system.

Efficient reuse of anode scrap from lithium-ion batteries as cathode for pollutant degradation in electro-Fenton process: Role of different recovery processes

Effective recycling of spent graphite from lithium-ion batteries (LIBs) has a strong application potential. In this research, anode scrap of spent LIBs is efficiently recovered and reused as high-performance cathode in electro-Fenton system. Role of different recovery processes in the reuse of anode scrap powder in electro-Fenton system is focused, including Anode raw powder (RP), acid leaching (AL), acid and alkali leaching (AAL) residual powder. The results indicate functional groups of anode powder are changed by different leaching processes, which can significantly affect the subsequent reuse in electro-Fenton system. According to evaluation by electrochemical characterization, the AAL has a higher hydrogen peroxide (H2O2) selectivity and yield than RP and AL due to highly active two-electron reduction of oxygen (O2). Interestingly, when anode powder is reused in electro-Fenton system, the AL electrode achieves 100% bisphenol A (BPA) removal in 70 min and 87.4% COD removal in 240 min, showing the best degradation efficiency. The reason can be attributed to higher carboxylic group content (35.83%) of AL powder than that of AAL (7%). Thus, part of iron ion in solution can be adsorbed on the surface of AL cathode, forming a partial heterogeneous iron oxidation-reduction. Furthermore, the reusability of AL electrode is evaluated. Compared with other carbon cathode, the AL cathode with a low current density still maintains 100% BPA removal after 10 reuse cycles. Since it is inherent with high reusability and environmental friendliness comparing with traditional cathode materials, this research demonstrates a potentially new approach to cooperatively treat pollutants from solid waste and waste water.

Toward the Digital Electrochemical Recognition of Cobalt, Iridium, Nickel, and Iron Ion Collisions by Catalytic Amplification.

We report the electrochemical detection of femtomolar amounts of cobalt, iridium, nickel, and iron ions in solution by electrocatalyst formation and amplification. The metal oxides of these ions can be formed electrochemically and can catalyze the oxidation of water. Alternatively, the reduction of metal ions to metals, such as the reduction of IrCl6(3-) to iridium, is capable of electrocatalytically reducing protons to molecular hydrogen, as shown previously with Pt. These events, which manifest themselves in amperometry, correspond to the formation of electrocatalytic nuclei on the electrode surface, capable of electrocatalytically oxidizing water or reducing protons. An analysis of the frequency of anodic blips compared to theory implies that the requirement for water oxidation is 10 ± 1 ions of cobalt, 13 ± 4 ions of iridium, and 11 ± 3 ions of nickel. A similar analysis for iridium reduction and the corresponding catalytic reduction of protons implies that 6 ± 2 ions of iridium are required for proton reduction. These numbers are confirmed in an analysis of the time of first nucleation event, i.e. the time at which the first blip on the amperometric i-t experiment occurs. We further show that the anodic blips in detecting nickel increase in intensity upon increasing amounts of iron ions in solution to a ratio of Ni/Fe of ∼5, surprisingly close to that for bulk electrocatalysts of Ni-Fe.

Mesoporous silica based catalysts for the oxidation of azodyes in waste water

Iron-containing catalysts supported on mesoporous silica samples that differ in the methods of their preparation (commercial KSS silica gel, MSM-41 mesoporous silicalite, and silica gels obtained under laboratory conditions by means of spray drying and drying in supercritical СО2) are synthesized. Their porous structure is studied via low-temperature nitrogen adsorption. Their catalytic activity and stability in the oxidation of carmoisine (an anionic dye) with a 3% hydrogen peroxide solution in water at 60°C and рН 3 are compared. The initial carmoisine and catalyst concentrations in solution are 20 mg/L and 3 g/L, respectively, and the molar Н2О2/carmoisine ratio is 459/1. The KSS-based catalyst demonstrates the highest activity and stability with respect to the outwashing of an active component into a solution: the conversion of carmoisine on this catalyst is as high as 99% for 30 min, while the concentration of iron ions in solution (0.27 mg/L) does not exceed the maximum allowable concentration. After the support is preimpregnated with aluminum, the degree of iron outwashing into a solution is more than halved. The synthesized catalysts are of interest with regard to the purification of waste water containing organic admixtures.

Morphological transformations in the magnetite biomineralizing protein Mms6 in iron solutions: a small-angle X-ray scattering study.

Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core-corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.

Bioregeneration of the pregnant leach solutions obtained during the leaching of nonferrous metals from slag waste by acidophilic microorganisms

The bioregeneration of the solutions obtained after the leaching of copper and zinc from slag waste by sulfuric acid solutions containing ferric iron was examined. For bioregeneration, associations of mesophilic and moderately thermqophilic acidophilic chemolithotrophic microorganisms were made. It has been shown that the complete oxidation of iron ions in solutions is possible at a dilution of the pregnant leach solution with a nutrient medium. It has been found that the maximal rate of oxidation of iron ions is observed at the use of a mesophilic association of microorganisms at a threefold dilution of the pregnant leach solution with a nutrient medium. The application of bioregeneration during the production of nonferrous metals from both copper converter slag and its waste would make it possible to approach the technology of their processing using the closed cycle of workflows.

Bioregeneration of the Solutions Obtained during the Leaching of Nonferrous Metals from Waste Slag by Acidophilic Microorganisms

The bioregeneration of the solutions obtained after the leaching of copper and zinc from waste slag by sulfuric solutions of ferric sulfate is examined. For bioregeneration, associations of mesophilic and moderately thermqophilic acidophilic chemolithotrophic microorganisms were made. It has been shown that the complete oxidation of iron ions in solutions obtained after the leaching of nonferrous metals from waste slag is possible at a dilution of the pregnant solution with a nutrient medium. It has been found that the maximal rate of oxidation of iron ions is observed at the use of a mesophilic association of microorganisms at a threefold dilution of the pregnant solution with a nutrient medium. The application ofbioregeneration during the production of nonferrous metals from both waste and converter slags would make it possible to approach the technology of their processing using the closed cycle of workflows.

Release of Iron Ions From the Stainless Steel Anode Occurring During High-Voltage Pulses and Its Consequences for Cell Electroporation Technology

One of the plausible reactions occurring during high-voltage pulses, which are used to electroporate the cells, is the oxidation of the metal ions of the anode resulting in the dissolution of the anode. In the case of the anode made from stainless steel, which is one of the most popular electrode materials, iron ions ( Fe2+ and Fe3+) are released from the anode. Here, this process and its consequences have been studied. A single square-wave electric pulse with the duration of 2 ms and the amplitude of 1.2 kV/cm increased the concentration of iron ions in solution by over 0.5 mM. Iron ions released from the anode behave as a Lewis acid and hydrolyze the water molecules in the solution, reducing the pH of a solution and might play a role in the changes of the medium conductivity. In addition, the roughness of the stainless steel anode increased progressively, in proportion with the total amount of the electric charge that had passed through the unit area of the electrode. The reduction of the viability of cells by iron ions has been demonstrated. The iron ions quench the fluorescence of anticancer drugs, which are used when photodynamic tumor therapy is combined with electroporation, such as porphyrin sulfonate and Adriamycin.

Fabricating Carbon Nanotube Network with Different Growth Density on Distinctive Fissure Structure Formed by Dried Ferroin Solution

Simple methods of fabricating distinctive carbon nanotube networks with different growth density on the same substrate have been investigated. Special substrates fabricated by drying a tris-1,10-phenanthroline iron complex (ferroin) solution on a silicon substrate were used. The ferroin consisted of 1,10-phenanthroline and iron ions in solution. The dried ferroin solution formed fissure structures with unique shapes and iron particles that acted as catalysts for carbon nanotube growth on the substrates. Thermal chemical vapor deposition in a hydrogen-methane gas system was used to grow the carbon nanotubes. The density of the carbon nanotube networks was low in fissure areas and high in block areas. The results indicate that the dried ferroin solution not only produces distinctive carbon nanotube structures, but also changes the growth density on the same substrate. [DOI: 10.1380/ejssnt.2009.586]

Solvent Effect of Alcohols at the L-Edge of Iron in Solution: X-ray Absorption and Multiplet Calculations

The local electronic structure of Fe(III) and Fe(II) ions in different alcohol solutions (methanol, ethanol, propan-1-ol) is investigated by means of soft X-ray absorption spectroscopy at the iron L 2,3-edge. The experimental spectra are compared with ligand field multiplet simulations. The solvated Fe(III) complex is found to exhibit octahedral symmetry, while a tetragonal symmetry is observed for Fe(II). A decrease in the solvent polarity increases the charge transfer from the oxygen of the alcohol to the iron ions. This conclusion is supported by Hartree-Fock calculations of the Mulliken charge distribution on the alcohols. A larger charge transfer is further observed from the solvent to Fe(III) compared to Fe(II), which is connected to the higher positive charge state of the former. Finally, iron ions in solution are found to prefer the high-spin configuration irrespective of their oxidation state.