Higher Ce Content Research Articles

Fortification of yogurt with cloves extract

The purpose of the current study was to evaluate the impact of different concentrations of clove extract (CE: 0%, 0.5%, 1.0%, and 2.0%) on the viscoelasticity, viscosity, syneresis, texture, sensory quality, and antioxidant properties of set yogurt up to 21 days in cold storage. The addition of CE enlarged the total suspended solids (TSS) and mineral contents while reducing whey separation. On the other hand, CE existence dropped the consistency index (k) and elastic modulus (G’) of yogurt gels and further lessening was observed with prolonged storage period. Moreover, the textural firmness remained unaffected whereas gels that are more cohesive were attained with integration of CE. Similarly, total phenolics and free radical scavenging activity increased significantly (p < 0.05) by CE supplementation, and amplified lipid oxidation was observed with increased storage time. Addition of CE lowered the lightness (L*) index and manipulated the organoleptic properties whereas the sample with 1% CE showed improvement in texture and flavor; however, the overall acceptability reduced for samples with higher concentration of CE.

Efficient recovery of rare earth elements from ion-adsorption rare earth tailings: Based on the addition of pyrite calcination modification

Rare earth tailings constitute a significant amount of solid waste that remains after industrial (NH4)2SO4 leaching and typically contain rare earth elements (REEs), primarily Ce. This study aimed to fully recover REEs from rare earth tailings by calcination with pyrite under both air and N2 atmospheres, followed by dilute H2SO4 leaching or bioleaching. The results of XRD, SEM-EDS, TIMA, SEM-BSE, XPS, and ICP-MS analyses indicated that Ce and Mn were mainly present in the form of CeO2 and MnO2, respectively, whereas Fe existed in both Fe2O3 and Fe2(SO4)3 forms. Leaching experiments with dilute H2SO4 demonstrated that the co-calcination of rare earth tailings with pyrite significantly enhanced the recovery of REEs. Notably, calcination in air resulted in a significantly higher extraction rate of Ce (95.55 %) than that in N2 (83.82 %). This difference was attributed to the presence of O2, which promoted the oxidation of pyrite and facilitated the reduction of Ce(IV) to Ce(III). In contrast, incomplete oxidation of pyrite occurred in the N2 atmosphere, leading to a high residual Ce(IV) content in the tailings that could not be leached by the dilute acid. Subsequently, sufficient recovery of Ce (97.52 %) from the tailings calcined in the N2 atmosphere was achieved by bioleaching using Acidithiobacillus ferrooxidans and pyrite. Thus, this study provides theoretical support for the efficient recovery of REEs from mining tailings or secondary sources containing CeO2.

Effect of Pressure on Ce-Substituted Nd-Fe-B Hot-Deformed Magnets in the Hot-Pressing Process.

With the increasing demand for Nd-Fe-B magnets across various applications, the cost-effective substitution of Ce has garnered significant interest. Many studies have been conducted to achieve the high magnetic properties of Nd-Ce-Fe-B hot deformation magnets in which Nd is replaced with Ce. We propose a method to improve magnetic properties of the Ce-substituted Nd-Ce-Fe-B hot-deformed magnets by optimizing the hot-pressing process. This study investigates the microstructure and properties following hot deformation of Ce-substituted Nd-Ce-Fe-B magnets fabricated at a constant temperature and different pressures (100-300 MPa) during the hot-pressing process. The results highlight the influence of pressure from previous hot-pressing processes on grain alignment and microstructure during hot deformation. Magnets subjected to hot pressing at 200 MPa followed by hot deformation achieved superior magnetic properties, with Hci = 8.9 kOe, Br = 12.2 kG, and (BH)max = 31 MGOe with 40% of Nd replaced with Ce. Conversely, precursors prepared at 100 MPa exhibited low density due to high porosity, resulting in poor microstructure and magnetic properties after hot deformation. In magnets using precursors prepared at 300 MPa, coarsened grains and a condensed h-RE2O3 phase were observed. Incorporating Ce into the magnets led to insufficient formation of RE-rich phases due to the emergence of REFe2 secondary phases, disrupting grain alignment and hindering the homogeneous distribution of the RE-rich phase essential for texture formation. Precursors prepared under suitable pressure exhibited uniform distribution of the RE-rich phase, enhancing grain alignment along the c-axis and improving magnetic properties, particularly remanence. In conclusion, our findings present a strategy for achieving the ideal microstructure and magnetic properties of hot-deformed magnets with high Ce contents.

Insight into the effect of Ce content on the magnetic properties of Ce-magnets with grain boundary diffusion Pr-Al alloys

The development of cost-effective Ce-magnets with high Ce content is urgent to realize the vision of cost reduction and performance enhancement. Dual-main-phase Ce-magnets with different Ce content (Ce accounted for the total amount of rare earths is 40%, 50% and 60%) are prepared. The Pr80Al20 (at%) alloy is selected as diffusion source for the three magnets using the grain boundary diffusion technique under the same conditions. The correlation of magnetic properties and microstructures before and after diffusion with different Ce contents are systematically analyzed. According to the EPMA results, the presence of Ce in the magnets facilitates the diffusion of Pr elements along the grain boundaries, which significantly increases the diffusion depth of Pr inside the magnets. As a consequence, the percentage increment of coercivity increase with the Ce content due to the increased diffusion depth. This study provides new insight into the preparation of dual-main-phase Ce-magnets with high Ce content of 40–60%.

The Geometric and Electronic Effects of Ceria on Promoting PdZn catalyst for Enhanced Acetylene Semi‐Hydrogenation

AbstractPdZn intermetallic compounds (IMCs) have been extensively reported for acetylene semi‐hydrogenation due to unique geometric and electronic structure of isolated Pd sites. However, to achieve high ethylene selectivity at high conversion remains challenging. Here we show the promotional role of ceria in modifying the geometric and electronic structure of PdZn IMCs towards enhanced catalytic performance for acetylene semi‐hydrogenation. The Ce (0.1 wt%) promoted Pd−Zn‐Al catalyst shows by far the best catalytic performance among other Pd based catalysts in literature, maintaining high selectivity (>95 %) and excellent stability (~130 h) at high acetylene conversion (~90 %). Using in situ spectroscopic techniques, the geometric and electronic effects of CeOx promotor were clearly elucidated. At low Ce content, the presence of highly dispersed Ce3+ species in the periphery of PdZn alloys enhanced electronic metal‐oxide interaction, resulting in electron‐rich Pd sites that promote hydrogen dissociation and ethylene desorption, and account for the outstanding catalytic performance. At high Ce content, the formation of bulk‐phase CeO2 suppressed the PdHx formation during PdZn alloying and led to phase separation yielding highly dispersed Pd ensembles, consequently lowering ethylene selectivity. Our results provide a new route for the design of PdZn catalyst by applying rare earth promoters towards high‐performance acetylene semi‐hydrogenation.

Grain boundary reconstruction for high-performance regeneration of Ce-abundance sintered Nd-Ce-Fe-B magnet scraps

In this study, we focus on the short-process regeneration of high-Ce content sintered Nd-Ce-Fe-B magnet scraps, aiming to enhance the coercivity and overall magnetic properties through the reconstruction of grain boundaries (GBs) based on the analysis of rare earth (RE) loss and proportions at each stage of the regeneration process. CeHx, (Nd0.75Pr0.25)Hx, and their mixtures were added as intergranular additives to produce sintered magnets. When 2.31 wt% of (Nd0.75Pr0.25)Hx is added, a high-performance magnet is obtained with the remanence of 11.72 kG, coercivity of 11.56 kOe, and maximum energy product of 32.23 MGOe, reaching performance recovery rates of 98.8%, 103.5%, and 98%, respectively, of the original magnets. It is indicated that the intergranular additives were beneficial to the formation of continuous smooth RE-rich GBs. In addition, a portion of Nd/Pr diffused into the 2:14:1 phase as a partial replacement for Ce, resulting in the migration of Ce from the interior of the grains to the outer region. This led to the formation of new RE-rich triple junction phases on the exterior, thereby reducing the magnetic dilution effect of Ce in the primary phase and enhancing the magnetic crystal anisotropy. These findings offer new insights into the regeneration of high-Ce sintered Nd-Ce-Fe-B scraps.

Abundance of Low-Energy Oxygen Vacancy Pairs Dictates the Catalytic Performance of Cerium-Stabilized Zirconia.

Cerium-stabilized zirconia (Ce1-xZrxOy, CZO) is renowned for its superior oxygen storage capacity (OSC), a key property long believed to be beneficial to catalytic oxidation reactions. However, 50% Ce-containing CZO recorded with the highest OSC has disappointingly poor performance in catalytic oxidation reactions compared to those with higher Ce contents but lower OSC ability. Here, we employ global neural network (G-NN)-based potential energy surface exploration methods to establish the first ternary phase diagram for bulk structures of CZO, which identifies three critical compositions of CZO, namely, 50, 60, and 80% Ce-containing CZO that are thermodynamically stable under typical synthetic conditions. 50% Ce-containing CZO, although having the highest OSC, exhibits the lowest O vacancy (Ov) diffusion rate. By contrast, 60% Ce-containing CZO, despite lower OSC (33.3% OSC compared to that of 50% Ce-containing CZO), reaches the highest Ov diffusion ability and thus offers the highest CO oxidation catalytic performance. The physical origin of the high performance of 60% Ce-containing CZO is the abundance of energetically favorable Ov pairs along the ⟨110⟩ direction, which reduces the energy barrier of Ov diffusion in the bulk and promotes O2 activation on the surface. Our results clarify the long-standing puzzles on CZO and point out that 60% Ce-containing CZO is the most desirable composition for typical CZO applications.

Synthesis and characterization of luminescent cerium-doped hydroxyapatite

Hydroxyapatite (HAp) biomaterials are intended for use as bone substitutes, target functional agents in theranostics or bioimaging due to affinity for hard tissues, biocompatibility, and bioactivity. This study is devoted to HAp doped with cerium, having distinctive feature to change the oxidation state (3+/4+), which affects the physico-chemical and optical properties of the obtained powders. Cerium-doped HAp nanopowders with Ce content up to 0.5 wt% were obtained through precipitation technique and then were heat treated. The following conditions for heat treating were used: (i) heating in air atmosphere, (ii) hot pressing, (iii) heating in a carbon filling. For characterization, the complex methodology was implemented, including X-ray diffraction (XRD) analysis and high temperature XRD, X-ray absorption near edge structure (XANES) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma atomic emission spectrometry (ICP-AES), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy, and, finally, photoluminescence (PL) spectroscopy. It was shown that the monophase cerium-HAp is stable up to a temperature of 1000 °C in the oxidizing atmosphere, above 1000 °C cerium(4+) oxide forms. Using reducing atmosphere during heating prevents the transition of Ce3+ to Ce4+. PL, EPR and XANES studding clarified obviously the Ce3+ content in the materials obtained under different processing conditions. It was shown, that Ce-HAp powders produced by precipitation and hot pressing contain Ce3+ and exhibit luminescence. The significant luminescence of hot pressed Ce-HAps was caused by a higher concentration of Ce3+ ions and incorporation of carbonate ions as a result of the processing.

Development of Molybdenum oxide Promoted CeO2−SiO2 Mixed‐oxide Catalyst for Efficient Catalytic Oxidation of Benzylamine to N‐Benzylidenebenzylamine

AbstractThis study explores a rational synthesis of a molybdenum‐promoted Ce−Si mixed oxide catalyst (MoO3/CeO2−SiO2) to regulate synergies between MoO3 and SiO2 dopant on CeO2, achieving high selectivity in solvent‐free catalytic oxidative coupling of amines to imines using molecular O2 as the oxidant. Comparative efficiency tests were conducted with bare CeO2, CeO2−SiO2, and MoO3/CeO2 catalysts. Characterization techniques, including XRD, Raman spectroscopy, N2‐adsorption‐desorption analysis, FTIR, NH3−TPD, TEM, and XPS, were employed to assess textural properties, acidic features, promoter and dopant dispersion in CeO2 lattice, and oxygen defects. Mo/Ce−Si catalyst exhibited superior acidic sites and a higher concentration of Ce3+ ions (Iu/ITotal), indicating increased oxygen vacancies. This catalyst demonstrated exceptional performance in the oxidative coupling of benzylamine, providing higher conversion and selectivity to the corresponding imine. Remarkably, the Mo/Ce−Si catalyst maintained consistent performance over five recycling runs. The catalyst also proved effective for the selective oxidative coupling of various amine substrates with diverse steric and electronic properties. Experimental results confirmed a plausible reaction mechanism within the concise catalyst design.

Early Jurassic and Late Cretaceous plagiogranites in Nain–Baft ophiolitic mélange zone in Iran: remnants of rift–drift and SSZ evolution of a Neotethyan seaway

We have investigated the geology, geochemistry and geochronology of various plagiogranite intrusions that are spatially associated with ophiolitic subunits in a mélange terrain exposed within the Nain–Baft fault zone along the western boundary of the Central–East Iranian Microcontinent (CEIM). One group of plagiogranites is intrusive into foliated amphibolites, whereas the plagiogranites of the other group are intrusive into gabbros, dyke swarms and pillow lavas that are tectonically juxtaposed. U–Pb zircon dating of the first group of plagiogranites has revealed near-concordant crystallization ages of 176.94 ± 0.71, 179.84 ± 0.92 and 190.40 ± 2.1 Ma, indicating the early Jurassic timing of their emplacement. U–Pb zircon dating of the second group of plagiogranites has revealed a weighted average age of 92.34 ± 0.38 Ma, indicating that they were emplaced in the early Late Cretaceous. The Early Jurassic plagiogranites are low-K, sub-alkaline rocks with negative Eu anomalies, low Ti and high La and Ce contents. They display elevated ratios of large ion lithophile elements to high field strength elements. They were part of a magmatic system that facilitated the earliest rift–drift stages of a Neotethyan seaway development, and their magmas were produced by fractional crystallization of a mafic melt associated with asthenospheric upwelling beneath a rift system. The Late Cretaceous plagiogranites are low-K, sub-alkaline rocks with negative Eu anomalies, high Y and low Ta contents. They show light REE depletion relative to flat heavy REE patterns, and high Ba/Th ratios. Magmas of these plagiogranites were the products of partial melting of amphibolites in the subducting oceanic lithosphere in the same Neotethyan seaway. Thus, we posit that plagiogranite rocks in suture zones can be excellent trackers of geochemical, geochronological and magmatic evolution of various types of oceanic crust through rift–drift, seafloor spreading and subduction initiation stages within the same ocean basins in the past. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Controlling grain growth to achieve improved magnetic properties of NdCeFeB magnets via grain boundary diffusion

The abnormal growth of grains near the surface of NdCeFeB magnets reduces the number of grain boundaries, and meanwhile, the formation of REFe2 phase also hinders the diffusion of rare earth elements, both of which limit the enhancement of magnetic properties. This poses a certain challenge for the preparation of high Ce content NdCeFeB magnets. In this work, it is found that the TbPrNdAl diffusion source can suppress the mutual diffusion between Ce in the main phase and rare earth elements in the diffusion source, thereby restraining the abnormal growth of grains and inhibiting the formation of REFe2 phase. Eventually, a more uniform core-shell structure and thin and continuous RE-rich phase are formed. The coercivity of 1389 kA/m and magnetic energy product of 289 kJ/m3 can be obtained without reducing the remanence, which are 612 kA/m and 30 kJ/m3 higher than those of the initial magnet, respectively. This diffusion source can greatly promote the development of NdCeFeB magnets with high Ce content.

Structural and dielectric properties of Cerium doped Magnesium-Zinc Aluminate spinel nano-crystallites for high frequency applications

The Ce3+ doped Mg–Zn Aluminate spinel nano size crystals with compositional formula of Mg0.5Zn0.5CexAl2-xO4 (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized by sol gel auto-combustion method followed by annealing at 800 °C for 3 h. The X-ray diffractometric (XRD) analysis confirmed space group FD3m and spinel structure of Ce3+ doped Mg–Zn Aluminates with crystallite size between 10 and 28 nm. Generally, an increasing trend in particles size and other structural parameters were observed at higher concentration of Ce3+ content. Transmission Electron Microscopy (TEM) was utilized to study the morphology and size of the Ce doped MG-Zn Aluminates that were consistent with XRD results. Furrier transforms infrared spectroscopy (FTIR) has been employed to reveal the absorption bands for the octahedral and tetrahedral sides observed in between 400 and 1000 cm−1. All samples were pelletized to study the dielectric properties like dielectric constant, impedance, electric modulus and tangent loss. Impedance spectroscopy was employed at room temperature in the applied frequency ranging from 1 MHz to 3 GHz. A consistent behavior in dielectric constant and dielectric loss was observed for the intermediate range of applied frequencies. The concentration at x = 0.10 was found to exhibit the most stable dielectric constant and dielectric loss behavior at high frequencies. The effect of doping concentration on grain and grain boundaries, the polarization phenomena and conductivity mechanism has been discussed. It is found that AC conductivity for all doping concentration is low at lower frequencies range from 1 MHz to 300 MHz while a peak is observed at higher frequency around 2.5 GHz. The valuable responses of dielectric constant and dielectric lost at higher frequency range show that Mg0.5Zn0.5CexAl2-xO4 can be used in high frequency devices.

Coercivity enhancement of NdCeFeB magnet by two-step grain boundary diffusion with Pr70Cu10Al15Ga5 and DyHx

Nd-Ce-Fe-B sintered magnets with Ce-substitution amounts of 30 wt% were treated by one- and two-step grain boundary diffusion processes, in which DyHx and low-melting-point Pr70Cu10Al15Ga5 (at%) alloys were designed as the diffusion sources and diffused into the magnets according to the different steps and orders. Results showed that the increase of coercivity was only 2.7 kOe when introducing heavy rare-earth Dy by the one-step diffusion of DyHx, reflecting the difficulty of conventional diffusion modification on high Ce content magnets. Note that by the two-step grain boundary diffusion (no matter which diffusion source was diffused preferentially in the first step), the coercivities were significantly enhanced over 18.5 kOe from the original 13.64 kOe, with the obvious improvements of thermal stability. Microstructures and compositions analyses revealed that the grain boundaries were greatly optimized after the diffusion of Pr70Cu10Al15Ga5, supporting favorable diffusion channels for the introduction of Dy in the subsequent second step. By contrast when introducing Dy first and then diffusing the Pr70Cu10Al15Ga5 second, the elements in the low-melting-point alloys could drive the superficial Dy to migrate into the deep interior of the magnets. Thus, both the two types of two-step grain boundary diffusions were conductive to improving the utilization of heavy rare-earth Dy in high Ce content magnets. Besides, dynamic domain evolution analyses demonstrated the positive effect of diffusion on anti-demagnetization. This work provided a foundation for the development of high Ce content magnets with high performances.

Green, Safe, and Reliable Synthesis of Bimetallic MOF-808 Nanozymes With Enhanced Aqueous Stability and Reactivity for Biological Applications.

Bimetallic metal-organic frameworks (MOFs) are promising nanomaterials whose reactivity towards biomolecules remains challenging due to issues related to synthesis, stability, control over metal oxidation state, phase purity, and atomic level characterization.Here, these shortcomings are rationally addressed through development of a synthesis of mixed metal Zr/Ce-MOFs in aqueous environment, overcoming significant hurdles in the development of MOF nanozymes, sufficiently stable on biologically relevant conditions. Specifically, a green and safe synthesis of Zr/Ce-MOF-808 is reported in water/acetic acid mixture which affords remarkably water-stable materials with reliable nanozymatic reactivity, including MOFs with a high Ce content previously reported to be unstable in water. The new materials outperform analogous bimetallic MOF nanozymes, showcasing that rational synthesis modifications could impart outstanding improvements. Further, atomic-level characterization by X-ray Absorption Fine Structure (XAFS) and X-ray Diffraction (XRD) confirmed superior nanozymes arise from differences in the synthetic method, which results in aqueous stable materials, and Ce incorporation, which perturbs the ligand exchange dynamics of the material, and could ultimately be used to fine tune the intrinsic MOF reactivity. Similar rational strategies which leverage metals in a synergistic manner should enable other water-stable bimetallic MOF nanozymes able to surpass existing ones, laying the path for varied biotechnological applications.

Electrochemical behavior and passive film properties of Ce-added AlCoCrFeNi2.1 eutectic high-entropy alloys in sulfuric acid solution

Eutectic high-entropy alloys (EHEAs), represented by AlCoCrFeNi2.1, are considered to be promising materials. However, the study of the corrosion behavior of EHEAs remains limited, which hinders further development. This study investigated the effect of Ce addition on the electrochemical behavior and passive film properties of AlCoCrFeNi2.1 EHEAs in H2SO4 solutions. The results show that the addition of Ce changed the properties of the passive film formed on the alloys, resulting in reduction in the proportion of Cr2O3, and thereby reduced the corrosion resistance. Moreover, a higher Ce content in the EHEAs was found to correspond to a more pronounced deterioration in corrosion resistance. Compared with the film formed at 0.2 Vvs SCE, the film formed at 0.5 Vvs SCE exhibited more optimal physicochemical properties, leading to a decrease in the passive current density. Notably, Ce was absent in the film formed at 0.2 Vvs SCE, but present at 0.5 Vvs SCE.

Multiferroic properties of BiFeO3 thin films with Ce substitution

In this study, we investigated the crystalline structure, ferroelectricity, leakage current density, magnetic, and nanomechanical properties of BiFeO3 (BFO) films with Ce substitution. Bi1-xCexFeO3 (BCFO) films with x = 0.00, 0.03, 0.06, 0.09, and 0.15 were deposited on glass substrates by using pulsed laser deposition. The experimental results showed that the BCFO films mainly composed the perovskite phase. The structure changed from rhombohedral when x = 0.00 to pseudo-cubic when x = 0.03, and pseudo-cubic phase coexisted with an additional Bi2Fe4O9 phase when x = 0.06–0.09. The BCFO films exhibited improved ferroelectricity and desirable magnetic characteristics. The remanent polarization (2Pr) increased significantly with the Ce concentration, reaching 189.3 μC/cm2 and 100.0 μC/cm2 when x = 0.03 and x = 0.06, respectively, but decreasing at higher Ce contents. The BCFO film with x = 0.03 had a remarkable 2Pr value of 189 μC/cm2 after 108 cycles due to the high (110) texture, fine microstructure, and flat interface resulting in strong anti-fatigue properties. The leakage mechanisms in the BCFO films were also examined. The films exhibited enhanced saturation magnetization (Ms) values ranging from 3.8 to 10.0 emu/cm3, which were attributed to suppression of the spiral spin configuration and the larger magnetic moment associated with the Ce3+ ion. The nanomechanical characteristics of the BCFO films, such as hardness, were significantly influenced by the grain size and phase composition. These findings provide valuable insights into enhancement of the multiferroic properties of BFO polycrystalline films through Ce substitution for use in various applications.

Enhanced radical scavenging performance of Pt@CeO2 via strong metal-support interaction effect for improving durability of proton exchange membrane fuel cell

Since scavenging free radical is regarded as an efficient strategy to enhance the durability of proton exchange membrane fuel cells (PEMFCs), strong metal-support interaction (SMSI) effect between metal and reducible oxide supports is employed as a strategy to moderate the number of accessible active sites for reduction-oxidation reaction. Enriched Pt–CeO2 interface to enhance SMSI effect is achieved as well via constructing multicore-shell structure Pt@CeO2. Theoretical calculation confirms that SMSI effect at Pt–CeO2 interface endows electrons flowing from Pt to CeO2 to reduce the formation energy of oxygen vacancies, while Pt@CeO2 with higher magnitude of lattice distortion plan provides enriched Pt–CeO2 interface that made more concentration of Ce3+ ions feasible. Results show that better free radical scavenging performance is achieved with higher concentration of Ce3+ ions in Pt@CeO2. Based on the open circuit voltage (OCV) test, the Pt@CeO2-modified membrane in this work decays at only 70% of the commercial membrane, while 65% of the maximum power is still maintained after the test. This superior performance to the commercial membrane indicates this designed structure with SMSI effect could be considered as a potential route to solve the free radical problem in PEM for enhanced durability of PEMFCs.

Performance changes in the anammox process under the stress of rare-earth element Ce(III) and the evolution of microbial community and functional genes

The high Ce(III) content in ionic rare-earth tailings wastewater has hindered the application of anammox process in this field. Here, the effect of Ce(III) on the performance of anammox processes was investigated, and the evolution of microbial communities and functional genes was explored using metagenomic sequencing. The results showed that the reactor nitrogen removal rate decreased when the Ce(III) concentration reached 25 mg/L, although ammonia nitrogen removal (92.31%) and nitrogen removal efficiency (81.33%) remained at a high level; however, both showed a significant decreasing trend. The relative abundance of anammox bacteria increased continuously from P1–P5, reaching 48.81%, whereas the relative abundance of Candidatus jettenia reached 33.71% at P5, which surpassed that of Candidatus brocadia as the most abundant anammox bacteria, and further analysis of functional genes and metabolic pathways revealed that Candidatus brocadia was richer in biochemical metabolic genes, whereas Candidatus jettenia had richer efflux genes.

Synthesis of Stable Cerium Oxide Nanoparticles Coated with Phosphonic Acid-Based Functional Polymers.

Functional polymers, such as poly(ethylene glycol) (PEG), terminated with a single phosphonic acid, hereafter PEGik-Ph are often applied to coat metal oxide surfaces during post-synthesis steps but are not sufficient to stabilize sub-10 nm particles in protein-rich biofluids. The instability is attributed to the weak binding affinity of post-grafted phosphonic acid groups, resulting in a gradual detachment of the polymers from the surface. Here, we assess these polymers as coating agents using an alternative route, namely, the one-step wet-chemical synthesis, where PEGik-Ph is introduced with cerium precursors during the synthesis. Characterization of the coated cerium oxide nanoparticles (CNPs) indicates a core-shell structure, where the cores are 3 nm cerium oxide and the shell consists of functionalized PEG polymers in a brush configuration. Results show that CNPs coated with PEG1k-Ph and PEG2k-Ph are of potential interest for applications as nanomedicines due to their high Ce(III) content and increased colloidal stability in cell culture media. We further demonstrate that the CNPs in the presence of hydrogen peroxide show an additional absorbance band in the UV-vis spectrum, which is attributed to Ce-O22- peroxo-complexes and could be used in the evaluation of their catalytic activity for scavenging reactive oxygen species.

Boosting the Rhodamine B adsorption of bimetallic Ce/Zr UiO-66: Effect of valence states of cerium precursor

Two kinds of Ce-doped UiO-66 were synthesized by using CeCl3·7H2O and (NH4)2Ce(NO3)6 as cerium precursors, namely Ce(III)- and Ce(IV)-UiO-66. The effect of valence states of cerium precursors on adsorption performance towards Rhodamine B (RhB) was investigated for the first time. Ce atoms are in two valence states of +3 and + 4, where Ce3+ ions turn their surfaces negatively charged. The higher cerium content (24.8%) and ratio of Ce3+/Ce4+ ions (1.4:1) of Ce(IV)-UiO-66 made its surface more negatively charged, which is contributed to form stronger electrostatic interaction with cationic dyes. The adsorption amounts of RhB were 239.5 mg/g and 431.7 mg/g for Ce(III)- and Ce(IV)-UiO-66, which are 2.38 and 5.11 times higher than pristine UiO-66, respectively. The well-fit Langmuir model and pseudo-second-order model suggest a monolayer chemisorption process. The adsorption mechanism suggests that the electrostatic interaction and the complexation interaction between Ce3+ and RhB are dominant factors affecting RhB adsorption. Since Ce3+ severed as adsorption sites, the higher Ce content and stronger electrostatic interaction of Ce(IV)-UiO-66 together promoted its RhB adsorption than Ce(III)-UiO-66. The obtained results help to understand how the mixed-valences of incorporated metals affect the adsorption behaviors of bimetallic MOFs deeply.