Metal Ions Fe3 Research Articles

Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi

To reveal the species of gem-grade red garnets with similar colors, especially the mechanisms underlying their subtle color differences, a series of tests, including conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy, were performed on gem-grade red garnets mined from Malawi. The results demonstrated that the color difference is not caused by the difference in species, and both the purplish-red and maroon-red garnets were magnesium-aluminum garnets (pyrope). They both contained the transition metal ions Fe2+, Mn2+, Fe3+, and Cr3+, with Fe2+ and Mn2+ occupying crystal site A and Fe3+ and Cr3+ occupying crystal site B. Cr3+ absorption peaks were observed at 367 and 690 nm; Fe3+ absorption peaks were observed at 502, 528, and 570 nm; and Mn2+ absorption peaks were observed at 400, 423, and 460 nm, which contributed to their respective colors. However, while the maroon-red pyrope had a larger Fe2+/Fe3+ ratio than the purplish-red pyrope, it lacked Mn2+ ions, which is the cause of the color difference between the two pyrope garnets. To date, the study of color differences in red garnets remains a major controversial topic. This study proposed an innovative spectroscopic approach, particularly the combination of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy, thus providing a novel methodology for investigating color differences in red garnets.

Use of Monocalcium Phosphate Monohydrate for Chemical Immobilization of Heavy Metals Ions in Copper Smelting Slags

Monocalcium phosphate monohydrate (MCPM) with chemical formula of Ca(H2PO4)2.H2O is a water-soluble and powerful agent for metal ion immobilization (removal) in soil and water. The use of MCPM can, therefore, be considered as an innovative and effective way to remove the leachable heavy metals from copper smelting slag. This study aims to (1) characterize copper smelting slag and perform the batch precipitation tests using MCPM, (2) analyze the treated copper smelting slag (residue) by x-ray diffraction (XRD) and (3) elucidate the mechanism of MCPM on leachable heavy metal removal from slag.The experimental results demonstrated that MCPM effectively removes Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr and Zn metal ions from copper smelting slag under different MCPM concentrations and reaction times. In addition, the XRD analysis reveals the formation of insoluble metal phosphates such as Cd3(PO4)2, Cu2(PO4)2OH, Fe3(PO4)2, Mn3(PO4)2, Pb3(PO4)2 and Zn3(PO4)2 in the residue of copper smelting slag.

DNA Stability in Biodosimetry, Pharmacy and DNA Based Data-Storage: Optimal Storage and Handling Conditions.

DNA long-term stability and integrity is of importance for applications in DNA based bio-dosimetry, data-storage, pharmaceutical quality-control, donor insemination and DNA based functional nanomaterials. Standard protocols for these applications involve repeated freeze-thaw cycles of the DNA, which can cause detrimental damage to the nucleobases, as well as the sugar-phosphate backbone and therefore the whole molecule. Throughout the literature three hypotheses can be found about the underlying mechanisms occurring during freeze-thaw cycles. It is hypothesized that DNA single-strand breaks during freezing can be induced by mechanical stress leading to shearing of the DNA molecule, by acidic pH causing damage through depurination and beta elimination or by the presence of metal ions catalyzing oxidative damage via reactive oxygen species (ROS). Here we test these hypotheses under well defined conditions with plasmid DNA pUC19 in high-purity buffer (1xPBS) at physiological salt and pH 7.4 conditions, under pH 6 and in the presence of metal ions in combination with the radical scavengers DMSO and Ectoine. The results show for the 2686 bp long plasmid DNA, that neither mechanical stress, nor pH 6 lead to degradation during repeated freeze-thaw cycles. In contrast, the presence of metal ions (Fe2+ ) leads to degradation of DNA via the production of radical species.

Fabrication of the polyethersulfone/functionalized mesoporous carbon nanocomposite nanofiltration membrane for dyes and heavy metal ions removal: Experimental and quantum mechanical simulation method

AbstractThe presence of industrial pollutants, especially salts, heavy metals ions, and dyes in water and wastewater is considered a serious environmental issue. To eliminate these pollutants, a high‐performing nanofiltration (NF) membrane was prepared by blending the functionalized mesoporous carbon CMK‐5 (F‐CMK‐5) nanofiller. This membrane was synthesized by introducing the active groups of sulfonyl and amide to the surface of mesoporous carbon CMK‐5 through covalent functionalization. Characterizations were conducted to study the membranes' physical properties and separation performance in terms of antifouling properties and rejection of salts, heavy metal ions, and dyes. The interactions between the active sites of the nanocomposite membrane and the studied solutes, including dyes and heavy metal ions in aqueous solutions, were studied by the density functional based tight binding method and structural optimization was carried out. Insertion of the F‐CMK‐5 nanofiller was eventuated in a remarkable increase in surface hydrophilicity, pure water flux, and antifouling properties. For all membranes, the lowest and the highest salt rejection was obtained for NaCl and Na2SO4, respectively, exhibiting the characteristics of NF membranes. Moreover, M0.3 with 0.3 wt% nanofiller showed the highest rejection for heavy metal ions (Fe2+ = 99.9%, Zn2+ = 99.9%, Cu2+ = 99.7%, and Pb2+ = 99.2%) and dyes (RB5 = 99.21, DR16 = 98.87, and MB = 98.12%), as well as high separation performance for filtration of multipollutant solutions. The reusability and 144 h uninterrupted filtration experiments for M0.3 confirmed the stability of the membrane. The findings suggest that the PES/F‐CMK‐5 nanocomposite NF membrane is a promising candidate for water and wastewater treatment.

Study on Surface Properties of Unalloyed Copper Implanted with Different Transition Metal ions

Copper is widely used in Integrated Circuits and electronic components. Its corrosion performance and service performance have been paid much attention. We implanted Ti, Cr, Fe, Ni, Zn and other fourth period transition metal ions into unalloyed copper. After that, zeta potential test, electrochemical test and density functional theory calculation were used to study the surface properties of the implanted samples. We found that for copper samples, the zeta potential of implanted samples is related to the type of implanted transition metal ions, that is, the charge state at the solid-liquid interface is related to the type of implanted ions. We use density functional theory calculations to explain this change in surface properties of metal samples before and after ion implantation. We find that the d-band center of the transition metal has a similar trend to zeta potential.

Cost-Effective and High Purity Valuable Metals Extraction from Water Leaching Solid Residues Obtained as a By-Product from Processing the Egyptian Boiler Ash

The water leaching solid residues (WLSR) obtained from salt-roasting Egyptian boiler ash are considered an essential secondary resource for (13%) nickel and (5.6%) zinc extraction. Hence, the current study aims for the cost-effective and high purity Ni, Zn, Fe and Mg metal ion extraction from (WLSR) using a sulfuric acid leaching process. The factors affecting the percentage recovery of Ni, Zn, Fe and Mg from WLSR, including leaching temperature, time, acid concentration and solid/liquid ratio, have been investigated. The obtained leaching solutions were analyzed chemically using ICP, and the different precipitates were analyzed mineralogically using XRD and EDX analysis and chemically using XRF. The maximum percentage recovery of Ni, Zn, Fe and Mg was 95.02%, 90.13%, 66.29% and 75.73%, which was obtained under the optimum leaching conditions of 8% H2SO4 concentration and 1/15 solid/liquid ratio at 85 °C for 240 min. The effect of pH, Fe2O3 dosage as nucleating agent and the precipitation duration on iron removal and Ni and Zn loss have been thoroughly studied. It has been found that >95% of the contained iron impurity can be removed, while nickel and zinc losses are around 4.2% and 3.8%, respectively. Additionally, a pH of 6 and 0.45 mol/L concentration of H2C2O4 was utilized to precipitate Mg as MgC2O4.2H2O, demonstrating that the precipitation efficiency of Mg reaches 96.9%. Nickel and zinc precipitation efficiency was 92.25% and 85.51%, respectively, by raising the solution pH to approximately 9. The kinetic of Ni and Zn dissolution has been investigated to explain the mechanism prevalent and the factors influencing the leaching process. It has been found that the nickel leaching kinetic is controlled by both diffusion through an inert porous layer and by chemical reaction with an activation energy of 20.25 kJ.mol−1. Meanwhile, the kinetic of zinc leaching is controlled by solid product layer diffusion with an activation energy of 11.67 kJ mol−1.

Enhanced solar inactivation of fungal spores by addition of low-dose chlorine: Efficiency and mechanism

This work demonstrated that the solar inactivation of fungal spores was enhanced by addition of low-dose chlorine. Although the effect of low-dose chlorine alone (2.0 mg/L) on culturability of fungal spores was negligible, the solar/chlorine inactivation on fungal spores performed better than solar alone inactivation, with a lower shoulder length and a higher maximum inactivation rate constant. The enhanced inactivation of Aspergillus niger can be ascribed to the membrane oxidation by chlorine, and the enhanced inactivation of Penicillium polonicum can be ascribed to the membrane oxidation by chlorine and ·OH (·OH plays a major role). The oxidization by chlorine and ·OH led to an increase in membrane permeability of fungal spores, which enhanced the solar inactivation, resulting in an increase in intracellular ROS and more serious morphological damage. Due to the presence of background substances such as dissolved organic matter and metal ions (Fe2+, Mn2+, etc.), the inactivation efficiency in real water matrices was decreased. The main disinfection by-products (DBPs) produced in the inactivation of fungal spores in chlorine alone and solar/chlorine treatments were dichloroacetic acid, trichloroacetic acid, trichloroacetone and trichloromethane. Generally, DBPs formation in solar/chlorine treatment was lower than those in chlorine alone treatment. Moreover, the regrowth potential of the two genera of fungal spores in R2A medium could be inhibited by adding low-dose chlorine.

Isophthaloylbis (Azanediyl) Dipeptide Ligand and Its Complexes: Structural Study, Spectroscopic, Molecular Orbital, Molecular Docking, and Biological Activity Properties

The ligand 2,2′-(isophthaloylbis(azanediyl))bis(3-phenylpropanoic acid; H2L) was used to build novel metal complexes of Co(II), Ni(II), Fe(III), and Zn(II) metal ions. Elemental analyses, thermal, infrared, mass, electronic spectra, magnetic moments, X-ray diffraction analysis, and conductivity measurements were used to predict the nature of bonding and the stereochemistry of the complexes. The complexes were proposed to have the general formula [M(H2L)(H2O)2]Cl n , where M = Co(II), Ni(II), and Zn(II) (n = 2) and Fe(III) (n = 3), based on the elemental analyses data. All of the complexes were electrolytes, according to the molar conductivity measurements. The FT-IR spectra revealed that the dipeptide ligand is tetradentately coordinated to metal ions, with NNOO donor atoms participating in coordination with metal (II)/(III) ions, resulting in octahedral complexes. Using the recommended programme, the structural formula for the investigated ligand was optimized. Using the density-functional theory (DFT) approach, the energy gaps and other essential theoretical parameters were calculated. The agar diffusion method was used to test the in vitro biological characteristics of the ligand (H2L) and its transition metal complexes against Gram(+) bacteria (Bacillis subtilis and Staphylococcus aureus) and Gram(−) bacteria (Escherichia coli and Pseudomonas aeruginosa). The title compounds were found to be more biologically active than the parent dipeptide ligand. The title compounds have a good interaction with the crystal structures of 3t88-Escherichia coli, 3ty7-S. aureus, 5h67-Bacillus subtilis, and 5i39-Pseudomonasaeruginosa, according to molecular docking study.

Metal tri-phosphonates containing aliphatic tertiary amines for medium-temperature proton conduction

New medium-temperature proton conductors (MATMP) were synthesized from amino trimethylene phosphonic acid (ATMP) and metal ions (Fe2+, Ce4+ and Zr4+) with varying molar ratios. The high content of phosphonic acid groups of ATMP endowed MATMP with good ion exchange capacity (IEC, 0.58∼3.45 meq·g−1) and proton conductivity. The aliphatic tertiary amine in ATMP improved proton conduction via ionic and hydrogen bonds. The proton conductivity of FeATMP(1:2) reached 0.124, 0.079 and 0.038 S cm−1 at 100%, 50% and 0 RH at 180 °C, respectively. MATMP exhibited good thermal and oxidative stability, demonstrating promising applications in fuel cell technology.

Coordination-Driven Metal-Polyphenolic Nanoparticles toward Effective Anticancer Therapy.

Stabilization of bioactive components, especially for hydrophobic functional factors, is a promising approach for improving their biological activity. Here, a metal-phenolic coordination chemistry that synthesizes biocompatible and biodegradable thin film based on tannic acid and trivalent metal ion (Fe3+ or Al3+ ) is addressed, and the results also demonstrate its use for encapsulating a hydrophobic drug (nobiletin) and triggering drug release for cancer treatment both in vitro and in vivo. This assembled system provides drug-loaded nanoparticles (NPs) with small, but uniform, size (≈200nm). It displays beneficial potential in enhancing colloidal stability and preventing premature drug leakage. Moreover, the metal-phenolic coating is found to possess high cell biocompatibility as a delivery vector for controlled drug delivery, while the final fabricated drug NPs have effective anti-tumor activity by both inducing higher tumor apoptosis and inhibiting tumor metastasis, which is superior to naked drug formulations. Overall, these findings propose an effective and straightforward way for coating hydrophobic drugs employing interfacial adhesion and assembly, which can be a highly promising vehicle for controlled-release biomedical applications for cancer therapy.

Quadruple analyte responsive platform: Point-of-care testing and multi-coding logic computation based on metal ions recognition and selective response

While it is recognized that instrumentation techniques can provide precise and sensitive solutions to heavy metal ion monitoring, it remains challenging to transform laboratory testing into a convenient, on-site, and quantitative sensing platform for point-of-care testing (POCT) in a resource-constrained setting. To address these limitations, an affordable and user-friendly colorimetric POCT sensing system is proposed here for selectively monitoring four metal ions (Fe3+, Co2+, Pb2+, and Cd2+) based on the sulfur quantum dots (S dots). Quadruple distinct visual signals (green, brown, precipitation, and bright yellow) are presented on the fabricated paper-based analytical devices (PADs) when mixing S dots and metal ions. The high-quality photographs of the PADs are captured by a scanner, while a smartphone App converts visual signals to HSV values. The quantitative analysis relies on the digital colorimetric reading, and the limits of detection are 0.59, 0.47, 0.82, and 0.53 μM for Fe3+, Co2+, Cd2+, and Pb2+, respectively. This metal ions-responsive platform is engineered as a smart strategy for multiple logic operations (YES, NOT, AND, INHIBIT, and NOR) by integrating multi-responsive blocks into the S dots with encoded patterns, which improves the computing capability. Accordingly, this strategy demonstrates its potential for on-site environmental testing and sophisticated molecular computation.

Mechanism and process for the extraction of lithium from the high magnesium brine with N,N-bis(2-ethylhexyl)-2-methoxyacetamide in kerosene and FeCl3

The degradation of TBP has become a stumbling block to the industrial continuous production of lithium chloride extraction from brines with high Mg/Li ratio by solvent extraction. To develop a more stable and more efficient extraction system, a novel amide system, containing newly synthesized extractant N,N-bis(2-ethylhexyl)-2-methoxyacetamide (NBEHMOA), FeCl3 6H2O and sulfonated kerosene, was proposed in this work. Compared with TBP and N523, NBEHMOA extracted Li+ and H+ in the sequence of TBP ˃ NBEHMOA ˃ N523 and N523 ˃ TBP ˃ NBEHMOA respectively. The solution containing 5.5 mol/L LiCl and 0.5 mol/L HCl was used as the eluent in the scrubbing process. A Li+ extraction efficiency of 96.7% and 22.31 g/L Li+ in the stripping solution were achieved by the whole process with counter-current twelve stages. The extraction mechanism investigated via FT-IR spectroscopy illustrated that the metal ions Fe3+ and Li+ were mainly coordinated by the carbonyl C = O in NBEHMOA. This novel amide system can successfully achieve the cascade extraction effect for lithium, Li/Mg separation and avoid the generation of phase interface objects through counter-current extraction of lithium from brine at a lower acidity. This work provided a novel extraction system to recover lithium from the higher magnesium/lithium ratio brines.

Efficiently selective extraction of iron (III) in an aluminum‐based metal–organic framework with native N adsorption sites

AbstractSeparation and recovery of metal ions from wastewater is greatly significant because of the non‐negligible harm of heavy metal ions in water to human health and environment. A water‐stable aluminum‐based metal–organic framework material (MOF‐303) with native N adsorption sites is proposed for the selective adsorption and separation of the mixture with heavy metal ions (Fe3+ and Cr3+). This type of material comprises the native N adsorption sites, evenly distributing on the organic linking group. It means that the adsorbent has a smoother transport channel for metal ion, resulting in high adsorption capacity and selectivity. The single‐component adsorption results show that MOF‐303 has excellent adsorption capacity for Fe3+, up to a maximum adsorption capacity of 104 mg·g−1, which is about 5 times more than the counterpart capacity of Cr3+. Comprehensive separation studies show that the separation of the mixture with these ions can be achieved in the pH range of 1–3, and the selective adsorption is the most efficient. During 30 min of adsorption process, the removal rate of Fe3+ can be attained by 90%. And the adsorption property of this material can be recovered effectively through pickling process. In addition, the adsorption mechanism of MOF‐303 is characterized by zeta potential analysis, X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT‐IR). Our work shows that MOF‐303 is not only a promising material for effective separation of Fe3+ from industrial wastewater but also providing a new perspective the specific adsorption capacity of MOF materials.

A nanozyme-based colorimetric sensor array as electronic tongue for thiols discrimination and disease identification

Thiol analysis is of vital significance due to the essential roles in disease diagnosis, while the highly similar structures of thiols are a major challenge in practical determination. Herein, a nanozyme-based colorimetric sensor array has been proposed as electronic tongue for excellent discrimination and sensitive quantitation of thiols. The sensing units are fabricated by integrating the terephthalic acid modified graphene quantum dots (TPA@GQDs) with three transition metal ions (Fe2+, Cu2+ and Zn2+) via coordination, respectively, which not only provide sufficient substrate binding sites but also form the metal ion-regulated catalytic active centers. In this way, disparate promotion degrees on the peroxidase-like catalytic activity have been achieved in different metal ion-TPA@GQD ensembles. Based on the strong binding affinity between metal ions and thiols, the catalytic active centers are removed from TPA@GQDs, which inhibits the catalytic activity of sensing unit to diverse degrees. Accordingly, using 3, 3′, 5, 5′-tetramethylbenzidine (TMB) as chromogenic substrate in the presence of hydrogen peroxide (H2O2), each sensing unit can generate differential colorimetric signals (fingerprints) for six thiol analytes, which can be accurately discriminated through linear discriminant analysis (LDA) with a detection limit of 50 nM. In addition, the discrimination of the same thiol with different concentrations and thiol mixtures have also been achieved. Furthermore, inspired by the distinct levels of thiols in practical samples, the proposed sensor array enables the identification of thiol-associated diseases by means of machine learning algorithm, which makes a positive contribution to medical diagnosis.

Degradation of Benzotriazole UV Stabilizers in PAA/d-Electron Metal Ions Systems—Removal Kinetics, Products and Mechanism Evaluation

Benzotriazole UV stabilizers (BUVs) have gained popularity, due to their absorption properties in the near UV range (200–400 nm). They are used in the technology for manufacturing plastics, protective coatings, and cosmetics, to protect against the destructive influence of UV radiation. These compounds are highly resistant to biological and chemical degradation. As a result of insufficient treatment by sewage treatment plants, they accumulate in the environment and in the tissues of living organisms. BUVs have adverse effects on living organisms. This work presents the use of peracetic acid in combination with d-electron metal ions (Fe2+, Co2+), for the chemical oxidation of five UV filters from the benzotriazole group: 2-(2-hydroxy-5-methylphenyl)benzotriazole (UV-P), 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol (UV-326), 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol (UV-327), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV-328), and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (UV-329). The oxidation procedure has been optimized based on the design of experiments (DoE) methodology. The oxidation of benzotriazoles follows first order kinetics. The oxidation products of each benzotriazole were investigated, and the oxidation mechanisms of the tested compounds were proposed.

Sulfur or nitrogen-doped rGO supported Fe-Mn bimetal – organic frameworks composite as an efficient heterogeneous catalyst for degradation of sulfamethazine via peroxydisulfate activation

In this work, sulfur/nitrogen modified reduced graphene oxide (S/N-rGO) was employed as both electron shuttle and support to fabricate Fe-Mn bimetallic organic framework@S/N-rGO hybrids (BOF@S/N-rGO) via a facile two-step solvothermal route. Compared with the transition metal ions (Fe2+/Mn2+), the classical metal oxide catalyst (Fe2O3 and Fe3O4) and nano zero-valent iron (nZVI), BOF@S/N-rGO catalyst can more effectively activate peroxydisulfate (PDS) with ultra-low concentration (0.05 mM) to degrade sulfamethazine (SMT). Quenching experiments, electron paramagnetic resonance (EPR) measurement and linear sweep voltammetry (LSV) showed that the activation pathways of PDS between the two catalysts were different. In BOF@N-rGO+PDS system, the degradation of SMT was mainly attributed to the oxidation of radicals including SO4•− and •OH, especially SO4•− . However, in BOF@S-rGO+PDS system, in addition to the radical pathway, there are also non-radical pathways, namely 1O2 and direct electron transfer. Furthermore, the applicability of BOF@S/N-rGO used in the PDS-mediated advanced oxidation processes (AOPs) was systematically investigated in terms of the effects of operating parameters and coexisting substance (anions and humic acid (HA)), the degradation of other pollutants, as well as the stability and reusability of the catalyst. This study proved that BOF@S/N-rGO was a promising activator of PDS with ultra-low concentration for the degradation of SMT.

Production Optimization and Biochemical Characterization of Cellulase from Geobacillus sp. KP43 Isolated from Hot Spring Water of Nepal.

This study is aimed at isolating and identifying a thermophilic cellulolytic bacterium from hot spring water and characterizing thermostable cellulase produced by the isolate. Enrichment and culture of water sample was used for isolation of bacterial strains and an isolate with highest cellulase activity was chosen for the production, partial purification, and biochemical characterization of the enzyme. Different staining techniques, enzymatic tests, and 16s ribosomal DNA (16s rDNA) gene sequencing were used for the identification of the isolate. The cellulase producing isolate was Gram positive, motile, and sporulated rod-shaped bacterium growing optimally between 55°C and 65°C. Based on partial 16s rDNA sequence analysis, the isolate was identified as Geobacillus sp. and was designated as Geobacillus sp. KP43. The cellulase enzyme production condition was optimized, and the product was partially purified and biochemically characterized. Optimum cellulase production was observed in 1% carboxymethyl cellulose (CMC) at 55°C. The molecular weight of the enzyme was found to be approximately 66 kDa on 12% SDS-PAGE analysis. Biochemical characterization of partially purified enzyme revealed the temperature optimum of 70°C and activity over a wide pH range. Further, cellulase activity was markedly stimulated by metal ion Fe2+. Apart from cellulases, the isolate also depicted good xylanase, cellobiase, and amylase activities. Thermophilic growth with a variety of extracellular enzyme activities at elevated temperature as well as in a wide pH range showed that the isolated bacteria, Geobacillus sp. KP43, can withstand the harsh environmental condition, which makes this organism suitable for enzyme production for various biotechnological and industrial applications.

Recent Progress in Fluorescent Probes For Metal Ion Detection.

All forms of life have absolute request for metal elements, because metal elements are instrumental in various fundamental processes. Fluorescent probes have been widely used due to their ease of operation, good selectivity, high spatial and temporal resolution, and high sensitivity. In this paper, the research progress of various metal ion (Fe3+,Fe2+,Cu2+,Zn2+,Hg2+,Pb2+,Cd2+) fluorescent probes in recent years has been reviewed, and the fluorescence probes prepared with different structures and materials in different environments are introduced. It is of great significance to improve the sensing performance on metal ions. This research has a wide prospect in the application fields of fluorescence sensing, quantitative analysis, biomedicine and so on. This paper discusses about the development and applications of metal fluorescent probes in future.

Double-exchange-induced effective increased CO2 capture of CaO by doping bimetallic oxides with variable valence state

• Double-exchange-induced effective increased CO 2 capture of CaO was investigated. • Novel (Fe-Mn)-doped calcium-based sorbent exhibited excellent performance. • Electron transfer can occur by intermediate oxygen p orbits between Fe and Mn ions. • Synergistic interaction of Fe and Mn can significantly reduce the activation energy. Motivated by the double exchange interaction between the adjacent magnetic ions in the magnetic oxides would lead to the generation of more oxygen vacancy to improve the CO 2 capture of CaO, here we report a double-exchange-induced effective increase of CO 2 performance of calcium-based adsorbent by incorporating bimetallic oxides with variable valence state (i.e. Fe, Mn, Ce, Cu) into CaO. The (Fe-Mn)-doped CaO sample exhibits excellent CO 2 adsorption capacity and carbonation conversion, remaining stable at 0.61 g CO 2 /g adsorbent and 95% after 20 cycles, respectively. The enhanced performance are attributed to uniform distribution of Fe 2 O 3 and Ca 2 MnO 4 particles preventing CaO crystallite growth and agglomeration. The (Fe-Mn)-doped sample with much thinner flake structure and the largest pore diameter is loose and porous, thus favoring CO 2 diffusion inside the particles and preventing sintering during carbonation period. The electron transfer between Fe and Mn carried out by the famous double exchange may boost the generation of oxygen vacancy and the effective improvement of the CO 2 affinity for the calcium-based adsorbent, which are significant to the diffusion of CO 3 2– and mobility of O 2– according to the mechanism of CO 2 adsorption. In addition, the (Fe-Mn)-doped adsorbent exhibits the fastest adsorption kinetics, and the synergistic interaction of Fe and Mn can significantly reduce the activation energy of carbonation reaction. The famous double-exchange interaction of magnetic metal oxide can occur by intermediate oxygen p orbits between adjacent Fe and Mn metal ions with different d orbital occupancies in the (Fe-Mn)-modified calcium-based adsorbent, which provides a unique way to design CO 2 adsorbent.

Interface Modulation of FePc/Porous Ti(HPO4)2 Z‐Scheme Heterojunctions with Ultrafine Ag for Efficiently Photocatalytic CO Oxidation

Herein, an integrative Z‐scheme heterojunction of ultrafine Ag‐ (≈ 4 nm) modulated FePc/porous Ti(HPO4)2 nanosheet (FePc/Ag/TiP NS) with extended spectrum response is designed and fabricated for efficient CO oxidation. The optimal one exhibits approximately tenfold enhancement in photocatalytic activity compared with the bulky TiP counterpart, even outperforming commercial TiO2 (P25). The greatly improved photoactivity is mainly ascribed to the accelerated Z‐scheme charge transfer, and well‐defined isolated central metal ion (Fe2+) in FePc with excellent oxygen activation capacity, along with the extended visible light response. The strengthened charge transfer depends on the interfacial modulation of the ultrafine Ag intentionally embedded in the pores of TiP NS, which enables the electrons of TiP NS migration directionally and induces high‐dispersion FePc controllable assembly on TiP NS with the increased loading amount. Moreover, it is revealed that CO is previously adsorbed on TiP NS via forming –OH–OC intermediate with the surface hydroxyl and subsequently react with the activated O2 by the Fe–N4 sites in FePc to produce CO2 mainly based on in situ diffuse reflectance infrared spectra and near ambient pressure XPS spectra. A new design concept for constructing Ti(HPO4)2‐based Z‐scheme heterojunctions is provided, and the avenues for efficient CO oxidation are paved.