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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Preparation and characterization of CNT-CeO{sub 2} nanocomposite

This paper reports decoration of CeO{sub 2} nanoparticles on multi-walled carbon nanotubes through a reflux process in which Ce (NO{sub 3}) {sub 3}·6H{sub 2}O serves as precursor and hydrazine hydrate (N{sub 2}H{sub 4}.H{sub 2}O) as reducing agent. Successful deposition of cubic fluorite CeO{sub 2} nanoparticles onto multi-walled carbon nanotubes has been confirmed by x-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). It was found that CeO{sub 2} nanoparticles formed in the presence of CNTs were larger as compared to pure CeO{sub 2} nanoparticles. Raman analysis showed that CeO{sub 2} induced a decrease in the size of the carbon grain in the CNTs. A red shift from 460 cm{sup −1} to 463 cm{sup −1} for F{sub 2g} mode of CeO{sub 2} has also been observed in Raman spectra of CNT- CeO{sub 2} nanocomposite as compared to pure CeO{sub 2}. The CeO{sub 2} coated multi-wall carbon nanotubes (CNT-CeO{sub 2}) nanocomposite would be a promising candidate for practical applications such as catalysis, sensing and power source applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

In-situ transmission electron microscopy study of oxygen vacancy ordering and dislocation annihilation in undoped and Sm-doped CeO 2 ceramics during redox processes

Ceria (CeO 2 ) based ceramics have been widely used for many applications due to their unique ionic, electronic, and catalytic properties. We report our findings in investigating into the redox processes of undoped and Sm-doped CeO 2 ceramics stimulated by high-energy electron beam irradiation within a transmission electron microscope (TEM). The reduced structure with oxygen vacancy ordering has been identified as the CeO 1.68 (C-Ce 2 O 3+δ ) phase via high-resolution TEM. The reduction of Ce 4+ to Ce 3+ has been monitored by electron energy-loss spectroscopy. The decreased electronic conductivity of the Sm-doped CeO 2 (Sm 0.2 Ce 0.8 O 1.9 , SDC) is revealed by electron holography, as positive electrostatic charges accumulated at the surfaces of SDC grains under electron beam irradiation, but not at CeO 2 grains. The formation of the reduced CeO 1.68 domains corresponds to lattice expansion compared to the CeO 2 matrix. Therefore, the growth of CeO 1.68 nuclei builds up strain inside the matrix, causing annihilation of dislocations inside the grains. By using in-situ high-resolution TEM and a fast OneView camera recording system, we investigated dislocation motion inside both CeO 2 and SDC grains under electron beam irradiation. The dislocations prefer to dissociate into Shockley partials bounded by stacking faults. Then, the partials can easily glide in the {111} planes to reach the grain surfaces. Even the Lomer-Cottrell lock can be swept away by the phase change induced strain field. Our results revealed the high mobility of dislocations inside CeO 2 and SDC grains during their respective redox processes

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effect of pretreatment conditions on acidity and dehydration activity of CeO 2 -MeO x catalysts

A series of MeOx-modified CeO 2 (CeO 2 -MnO x , CeO 2 -ZnO, CeO 2 -MgO, CeO 2 -CaO, and CeO 2 -Na 2 O) catalysts were prepared by the impregnation of CeO 2 with corresponding metal nitrates. Acidity and oxidation state of cerium were investigated on both oxidized and reduced catalysts by employing Fourier Transform Infrared spectroscopy (FTIR) on adsorbed pyridine and in situ H 2 -Temperature Programmed Reduction/X-ray Absorption Spectroscopy (H 2 -TPR/XAS) techniques, respectively. Metal oxide addition tended to alter both type and number of acid sites on ceria. EXAFS data showed a significant difference in N Ce-O between unmodified and CeO 2 -MeO x , suggesting that added MeO x interferes with vacancy formation on ceria during reduction. Here, in comparison with air-pretreated samples, H 2 -pretreated ones under similar conversion of 1,5 pentanediol exhibited a higher selectivity towards linear alcohols. Alcohol conversion found to correlate with total acidity (i.e., Brønsted and Lewis). CeO 2 benefited from the addition of alkali (Na) or alkaline earth metals (Mg, Ca) by producing unsaturated alcohols.

1,5-Pentanediol↗
DOE OSTI2015

Photoelectron spectra of CeO{sup −} and Ce(OH){sub 2}{sup −}

The photoelectron spectrum of CeO{sup −} exhibits what appears to be a single predominant electronic transition over an energy range in which numerous close-lying electronic states of CeO neutral are well known. The photoelectron spectrum of Ce(OH){sub 2}{sup −}, a molecule in which the Ce atom shares the same formal oxidation state as the Ce atom in CeO{sup −}, also exhibits what appears to be a single transition. From the spectra, the adiabatic electron affinities of CeO and Ce(OH){sub 2} are determined to be 0.936 ± 0.007 eV and 0.69 ± 0.03 eV, respectively. From the electron affinity of CeO, the CeO{sup −} bond dissociation energy was determined to be 7.7 eV, 0.5 eV lower than the neutral bond dissociation energy. The ground state orbital occupancies of both CeO{sup −} and Ce(OH){sub 2}{sup −} are calculated to have 4f 6s{sup 2} Ce{sup +} superconfigurations, with open-shell states having 4f5d6s superconfiguration predicted to be over 1 eV higher in energy. Low-intensity transitions observed at higher electron binding energies in the spectrum of CeO{sup −} are tentatively assigned to the {sup 1}Σ{sup +} (Ω = 0) state of CeO with the Ce{sup +2}⍰6s{sup 2} superconfiguration.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2014

STK Integrated Message Production List Editor (SIMPLE) for CEO Operations

Late in fiscal year 2011, the Crew Earth Observations (CEO) team was tasked to upgrade and replace its mission planning and mission operations software systems, which were developed in the Space Shuttle era of the 1980s and 1990s. The impetuses for this change were the planned transition of all workstations to the Windows 7 64-bit operating system and the desire for more efficient and effective use of Satellite Tool Kit (STK) software required for reliable International Space Station (ISS) Earth location tracking. An additional requirement of this new system was the use of the same SQL database of CEO science sites from the SMMS, which was also being developed. STK Integrated Message Production List Editor (SIMPLE) is the essential, all-in-one tool now used by CEO staff to perform daily ISS mission planning to meet its requirement to acquire astronaut photography of specific sites on Earth. The sites are part of a managed, long-term database that has been defined and developed for scientific, educational, and public interest. SIMPLE's end product is a set of basic time and location data computed for an operator-selected set of targets that the ISS crew will be asked to photograph (photography is typically planned 12 to 36 hours out). The CEO operator uses SIMPLE to (a) specify a payload operations planning period; (b) acquire and validate the best available ephemeris data (vectors) for the ISS during the planning period; (c) ingest and display mission-specific site information from the CEO database; (d) identify and display potential current dynamic event targets as map features; (e) compute and display time and location information for each target; (f) screen and select targets based on known crew availability constraints, obliquity constraints, and real-time evaluated constraints to target visibility due to illumination (sun elevation) and atmospheric conditions (weather); and finally (g) incorporate basic, computed time and location information for each selected target into the daily CEO Target List product (message) for submission to ISS payload planning and integration teams for their review and approval prior to uplink. SIMPLE requires and uses the following resources: an ISS mission planning period Greenwich Mean Time start date/time and end date/time), the best available ISS mission ephemeris data (vectors) for that planning period, the STK software package configured for the ISS, and an ISS mission-specific subset of the CEO sites database. The primary advantages realized by the development and implementation of SIMPLE into the CEO payload operations support activity are a smooth transition to the Windows 7 operating system upon scheduled workstation refresh; streamlining of the input and verification of the current ISS ephemeris (vector data); seamless incorporation of selected contents of the SQL database of science sites; the ability to tag and display potential dynamic event opportunities on orbit track maps; simplification of the display and selection of encountered sites based on crew availability, illumination, obliquity, and weather constraints; the incorporation of high-quality mapping of the Earth with various satellite-based datasets for use in describing targets; and the ability to encapsulate and export the essential selected target elements in XML format for use by onboard Earth-location systems, such as Worldmap. SIMPLE is a carefully designed and crafted in-house software package that includes detailed help files for the user and meticulous internal documentation for future modifications. It was delivered in February 2012 for test and evaluation. Following acceptance, it was implemented for CEO mission operations support in May 2012.

Trenchard, Mike↗
DOE OSTI2013

Graphite oxide-mediated synthesis of porous CeO{sub 2} quadrangular prisms and their high-efficiency adsorptive performance

Graphical abstract: - Highlights: • Porous CeO{sub 2} quadrangular prisms have been prepared via graphite oxide-mediated synthesis. • Dual-pore hierarchical systems are formed with the pore distributions around 4 nm and 30 nm. • Porous CeO{sub 2} exhibits a rapid adsorption to Rhodamine B with a removal efficiency of ∼99%. • Porous CeO{sub 2} retains the same performances in different pH solutions. - Abstract: We report a graphite oxide-mediated approach for synthesizing porous CeO{sub 2} through a facile hydrothermal process followed by thermal annealing in air. The phase structure, morphology, microstructure and porosity of the products have been revealed by a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N{sub 2} adsorption. The as-prepared CeO{sub 2} products show well-defined quadrangular prism morphology, and they are composed of interconnected nanoparticles with diameters around 30–100 nm. In particular, the dual-pore hierarchical systems are created in the CeO{sub 2} quadrangular prisms with the pore distributions around 4 nm and 30 nm. The dye sorption capacity of the porous CeO{sub 2} is investigated, which exhibits a rapid adsorption to rhodamine B with a high removal efficiency of ∼99%. Moreover, the CeO{sub 2} absorbent retains the same performances in different pH solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Mechanism of Methane Chemical Looping Combustion with Hematite Promoted with CeO 2

Chemical looping combustion (CLC) is a promising technology for fossil fuel combustion that produces sequestration-ready CO{sub 2} stream, reducing the energy penalty of CO{sub 2} separation from flue gases. An effective oxygen carrier for CLC will readily react with the fuel gas and will be reoxidized upon contact with oxygen. This study investigated the development of a CeO{sub 2}-promoted Fe{sub 2}O{sub 3}-hematite oxygen carrier suitable for the methane CLC process. Composition of CeO{sub 2} is between 5 and 25 wt % and is lower than what is generally used for supports in Fe{sub 2}O{sub 3} carrier preparations. The incorporation of CeO{sub 2} to the natural ore hematite strongly modifies the reduction behavior in comparison to that of CeO{sub 2} and hematite alone. Temperature-programmed reaction studies revealed that the addition of even 5 wt % CeO{sub 2} enhances the reaction capacity of the Fe{sub 2}O{sub 3} oxygen carrier by promoting the decomposition and partial oxidation of methane. Fixed-bed reactor data showed that the 5 wt % cerium oxides with 95 wt % iron oxide produce 2 times as much carbon dioxide in comparison to the sum of carbon dioxide produced when the oxides were tested separately. This effect is likely due to the reaction of CeO{sub 2} with methane forming intermediates, which are reactive for extracting oxygen from Fe{sub 2}O{sub 3} at a considerably faster rate than the rate of the direct reaction of Fe{sub 2}O{sub 3} with methane. These studies reveal that 5 wt % CeO{sub 2}/Fe{sub 2}O{sub 3} gives stable conversions over 15 reduction/oxidation cycles. Lab-scale reactor studies (pulsed mode) suggest the methane reacts initially with CeO{sub 2} lattice oxygen to form partial oxidation products (CO + H{sub 2}), which continue to react with oxygen from neighboring Fe{sub 2}O{sub 3}, leading to its complete oxidation to form CO{sub 2}. The reduced cerium oxide promotes the methane decomposition reaction to form C + H{sub 2}, which continue to react with Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4} to form CO/CO{sub 2} and H{sub 2}O. This mechanism is supported by the characterization studies, which also suggest that the formation of carbonaceous intermediates may affect the reaction rate and selectivity of the oxygen carrier.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

CEOS Committee on Earth Observations Satellites Consolidated Report, 1992

A concise overview of the committee on Earth Observations Satellites (CEOS) and its Working Groups, covering the history and purpose of the Committee and its accomplishments to date are provided. The report will be updated annually before each Plenary meeting, and as developments in the Working Groups warrant. The committee on Earth Observations Satellites (originally named the International Earth Observations Satellite committee, IEOS) was treated in 1984, in response to a recommendation from the Economic Summit of Industrialized Nations Working Group on Growth, Technology, and Employment's Panel of Experts on Satellite Remote Sensing. This group recognized the multidisciplinary nature of satellite Earth observations, and the value of coordinating across all proposed missions. Thus, CEOS combined the previously existing groups for coordination on Ocean Remote-Sensing Satellites (CORSS) and coordination on Land Remote-Sensing Satellites (CLRSS), and established a broad framework for coordination across all spaceborne Earth observations missions. The first three LEOS Plenary meetings focused on treating and guiding the Working Groups deemed necessary to carry out the objectives of the CEOS members. After the third meeting, it was agreed that a more active orientation was required by the Plenary, and additional issues were brought before the group at the fourth meeting. At the fifth Plenary, international scientific programs and relevant intergovernmental organizations accepted invitations and participated as affiliate members of CEOS. This enabled progress toward integrating satellite data users' requirements into the CEOS process. Data exchange principles for global change research were also adopted. An interim CEOS Plenary meeting was held in April 1992, in preparation for the United Nations Conference on Environment and Development (UNCED). Brief encapsulations of the Plenary sessions immediately follow the Terms of Reference that govern the activities of CEOS as a whole; Terms of Reference for the individual Working Groups are included as Appendix A. A complete listing of CEOS members is offered as Appendix B.

Source record↗
DOE OSTI2018

Structural, Optical, and Magnetic Properties of Nd-Doped CeO{sub 2} Nanoparticles Codoped with Transition Metal Elements (Cu, Zn, Cr)

In the present work, pure CeO{sub 2}, neodymium-doped CeO{sub 2}, and neodymium and transition metal element (Cu, Zn, Cr)-codoped CeO{sub 2} nanoparticles were synthesized by an auto-combustion method and annealed at 700 {sup ∘}C. The X-ray diffraction (XRD) studies revealed that all the samples exhibited a single-phase cubic fluorite structure with the incorporation of respective dopant ions into the CeO{sub 2} lattice. The scanning electron microscopy (SEM) images displayed the prepared nanoparticles which had an irregular flaky structure with large agglomerations. The Fourier transform Raman (FT-Raman) spectroscopy analysis revealed the increased oxygen vacancy defects in CeO{sub 2} host after doping and codoping with neodymium and transition metal elements. Ultraviolet-diffuse reflectance spectroscopy (UV-DRS) studies revealed the decrease in bandgap values in doped and codoped samples compared to pure CeO{sub 2} sample. The Fourier transform infrared spectroscopy (FTIR) studies revealed the presence of functional groups in the prepared samples. Photoluminescence (PL) spectroscopy analysis reported the decreased luminescence intensities of Nd-doped and neodymium and transition metal-codoped CeO{sub 2} nanoparticles. The vibrating sample magnetometer (VSM) results depicted that all the samples exhibited room-temperature ferromagnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

The Triple Component Interface of Ni–Co–Ce: Growth, Chemical State, and Stability of NiCo Bimetallic Particles on Reducible CeO 2 (111) Thin Films

The growth of NiCo particles at low coverages over reducible CeO 2 (111) thin films producing a triple interface between Ni-Co-Ce was investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), which was compared to that of monometallic Ni and Co particles. XPS data show that deposition of either Ni or Co on CeO 2 at 300 K causes a partial reduction of Ce 4+ cations to Ce 3+ ions. At 0.3 monolayer (ML), XPS detects Co 2+ on CeO 2 . However, both Ni 0 and Ni 2+ are present as major species at 300 K and annealing causes a significant increase of Ni 2+ in Ni particles. Deposition of 0.3 ML Co over 0.3 ML Ni on CeO 2 at 300 K induces reduction of Ni 2+ to metallic Ni and Ni 0 was found as predominant species. Unlike for Co/CeO 2 , metallic Co was also present over the Co-Ni/CeO 2 surface in addition to Co 2+ . Further, this behavior indicates the formation of NiCo bimetallic particles with the possibility of Co diffusion to the interface of Ni/ceria. With heating, the intermixing of Ni and Co atoms in bimetallic particles on CeO 2 was facilitated. Furthermore, oxidation of both metals and ceria occurred as a result of the diffusion of lattice oxygen from the bulk of ceria to the surface. A slight increase in Ni 2+ was observed after heating Co-Ni/CeO 2 to 500 K or higher. Co became Co 2+ with heating to 800 K. Our STM results confirm the formation of NiCo bimetallic particles on CeO 2 at 300 K and further suggest that the addition of Co can help inhibit the sintering of Ni particles at higher temperatures. Bimetallic particles were also obtained by depositing Ni over existing Co particles on CeO 2 . However, our XPS data demonstrate that the deposition order of Co and Ni plays a role in the chemical state of these two metals in bimetallic particles, likely attributed to the difference in their compositions at the bimetallic particle surface as well as the metal-support interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

CeO 2 Promoted CuO/MgO-Al 2 O 3 Catalyst with Enhanced Activity and Water-Resistance for CO Oxidation

Copper (Cu)-based catalysts have emerged as cost-effective and sustainable alternatives to noble metal systems (e.g., Pt, Pd) for catalytic CO oxidation. However, their practical application is hindered by insufficient low-temperature activity and rapid deactivation under wet conditions containing moisture. To address these challenges, this work introduces CeO 2 -modified CuO/MgO-Al 2 O 3 (Cu-Ce/MA) catalysts, strategically designed to enhance the catalytic performance and water resistance simultaneously. These catalytic materials were evaluated for CO oxidation under both dry and humid conditions, revealing that CeO 2 modification significantly improves the low-temperature activity. Specifically, the optimal catalyst, Cu-30Ce/MA, achieved a 50% CO conversion temperature (T 50 ) of 151 °C, a marked reduction from 218 °C on Cu/MA reference catalyst. Furthermore, the water resistance improves in a CeO 2 content-dependent manner, with higher CeO 2 loadings imparting greater stability in humid environments. Detailed characterizations demonstrate that CeO 2 promotes the dispersion of CuO and stabilizes Cu sites, while also enhancing the low-temperature reducibility and CO adsorption capacity. Crucially, CeO 2 modification suppresses the competitive H 2 O adsorption, mitigating water-induced deactivation. These synergistic effects collectively rationalize the superior activity and durability of Cu-Ce/MA catalysts. By elucidating the dual role of CeO 2 in optimizing Cu-based systems, this study advances the rational design of cost-effective catalysts for real-world CO emission control, particularly under water-rich industrial conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Enhanced Colloidal Stability of CeO 2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation

Due to the toxicity of cerium oxide (CeO 2 ) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO 2 NPs and their transport in natural and engineered aqueous systems is needed. As such, this study investigates the impact of redox reactions with ferrous ions (Fe 2+ ) on the colloidal stability of CeO 2 NPs. We demonstrated that under anaerobic conditions, suspended CeO 2 NPs in a 3 mM FeCl 2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe 2+ . Redox reactions between CeO 2 NPs and Fe 2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO 2 NPs. These redox reactions can affect the toxicity of CeO 2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

(U) PRAD0697 & PRAD0698: Complex Loading of CeO₂ Powder

Cerium(IV) oxide (CeO₂) powder is shock compressed using the Precision High Energy-density Liner Implosion eXperiment (PHELIX) platform. Experimental results are compared against several modeling approaches. Compaction behavior is best captured with a P-∝ model, which calculates CeO₂ powder bulk densities within 80-99% of experimental values but overpredicts densi cation at the cylindrical target's outer radius and center by up to 20%. Preliminary calculations suggest that accuracy could be increased with the inclusion of a coupled strength model. Several common computational modeling approaches for the shock compression response of granular materials and the magnetohydrodynamic (MHD) force upon the impactor/liner in pulsed power compression experiments are investigated and analyzed for their validity. The Bi-linear Ramp, P-∝ PACXP, and P-∝ Menikoff-Kober continuum compaction models are calibrated to planar impact Hugoniot data for CeO₂ powder and used to predict the powder's shock compaction response under non-planar shock wave compression. MHD calculations of the PHELIX pulsed power driver are performed using an idealized resistor-inductor-capacitor (RLC) circuit calibrated to previous experiments. All simulations are performed using the LANL code FLAG. Two validation experiments are computationally designed using the calibrated compaction and circuit models, executed using the PHELIX platform on CeO₂ targets with initial porous densities of 3.95 and 4.03 g/cm³, measured with proton radiography, and analyzed against the model predictions. The two P-∝ models more accurately describe CeO₂ powder densi cation than the Bi-linear Ramp model. However, the two P-∝ models overpredict bulk density of the shock compressed CeO₂ powder by up to 20% when the appropriate impact velocities are applied. MHD calculations for both validation experiments underpredict liner impact velocities by 4-11% when using the idealized RLC circuit model calibrated to previous experiments. Compensating underpredictions of impact velocity and overpredictions of powder densication lead to a false accuracy in pre-shot calculations compared to experimental data. To improve correlation between simulations and experiments, the following improvements are suggested: 1. A coupled strength model for CeO₂ powder that updates strength as a function of porosity and applied stress. 2. An improved MHD circuit model that more accurately captures the PHELIX machine.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Influence of CeO{sub 2} NPs on biological phosphorus removal and bacterial community shifts in a sequencing batch biofilm reactor with the differential effects of molecular oxygen

The effects of CeO{sub 2} nanoparticles (CeO{sub 2} NPs) on a sequencing batch biofilm reactor (SBBR) with established biological phosphorus (P) removal were investigated from the processes of anaerobic P release and aerobic P uptake. At low concentration (0.1 mg/L), no significant impact was observed on total phosphorus (TP) removal after operating for 8 h. However, at a concentration of 20 mg/L, TP removal efficiency decreased from 83.68% to 55.88% and 16.76% when the CeO{sub 2} NPs were added at the beginning of the anaerobic and aerobic periods, respectively. Further studies illustrated that the inhibition of the specific P release rate was caused by the reversible states of Ce{sup 3+} and Ce{sup 4+}, which inhibited the activity of exopolyphosphatase (PPX) and transformation of poly-β-hydoxyalkanoates (PHA) and glycogen, as well as the uptake of volatile fatty acids (VFAs). The decrease in the specific P uptake rate was mainly attributed to the significantly suppressed energy generation and decreased abundance of Burkholderia caused by excess reactive oxygen species. The removal of chemical oxygen demand (COD) was not influenced by CeO{sub 2} NPs under aerobic conditions, due to the increased abundance of Acetobacter and Acidocella after exposure. The inhibitory effects of CeO{sub 2} NPs with molecular oxygen were reduced after anaerobic exposure due to the enhanced particle size and the presence of Ce{sup 3+}. - Highlights: • CeO{sub 2} NPs (20 mg/L) had a notable toxicity effect on P removal in SBBR system. • The deteriorated SPRR was caused by the inhibited key enzyme activity (PPX). • The decreased SPUR was caused by the bacterial community shifts. • Ce ions converting and excess ROS generation are related toxicity mechanisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Degradation of Congo Red dye by a Fe 2 O 3 @CeO 2 -ZrO 2 /Palygorskite composite catalyst: Synergetic effects of Fe 2 O 3

A newly designed Fe 2 O 3 @CeO 2 -ZrO 2 /Palygorskite heterogeneous Fenton catalyst with high degradation efficiency toward Congo Red (CR) is reported in this paper. The iron oxide (Fe 2 O 3 ) was used as the originator of hydroxyl radicals ( OH), CeO 2 -ZrO 2 was used as an efficient matrix of Fe 2 O 3 to enhance the oxidation performance, and the Palygorskite (Pal) played the role of substrate and adsorbent. A synergetic effect of the catalyst was realized by enhancing the adsorption capacity and dispersibility of CeO 2 -ZrO 2 and Fe 2 O 3 nanoparticles, and also due to charge transfer between these two species. The products were characterized by XRD, FTIR, SEM, TEM, XPS, VSM and nitrogen adsorption-desorption isotherms. The catalytic activities were evaluated in terms of many reaction parameters. The removal efficiency of CR was up to 95% on Fe 2 O 3 @CeO 2 -ZrO 2 /Pal under optimized conditions (Pal accounted for 30% of the catalyst mass fraction and Ce/Zr atoms molar ratio = 8:2, T = 30 °C, pH = 3.4, 4 g L -1 catalyst, 40 mM H 2 O 2 and 500 mg/L CR), the product also has shown good reusability. Both α-Fe 2 O 3 and CeO 2 -ZrO 2 played important roles in the generation of hydroxyl radicals, which determined the catalytic efficiency of the composite catalyst. Fe 2 O 3 @CeO 2 -ZrO 2 /Pal was proven to be a promising candidate in the field of heterogeneous Fenton catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗