Showing papers on "Lanthanum published in 2012"
TL;DR: In this paper, a novel adsorbent, lanthanum hydroxide-doped activated carbon fiber (ACF-LaOH), has been prepared by the ultrasound-assisted chemical precipitation method for phosphate removal from waste water.
225 citations
TL;DR: In this paper, a La-promoted NiMgAl mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the carbon dioxide reforming of methane.
164 citations
TL;DR: Results showed that the removal efficiency of arsenate increased with the increment of the lanthanum content in Cu/Mg/Fe/La-LDH adsorbents, and the optimized lanthanums content was 20% of the total trivalent metals composition (Fe3+ and La3+).
146 citations
TL;DR: In this article, a hydrometallurgical process to recover rare earth and basemetals from spent NiMH batteries was described, where rare earths were recovered by selective precipitation with sodium hydroxide at pH less than 2 after leaching: in these conditions a precipitate composed of lanthanum and cerium sulphates are produced.
122 citations
TL;DR: In this article, the molybdenum substituted lanthanum tungstate was investigated for an enhancement of the n-type electronic conductivity for its use as a mixed electron-proton conductor in hydrogen gas separation membrane applications.
Abstract: Molybdenum substituted lanthanum tungstate, La28–y(W1–xMox)4+yO54+δ (x = 0–1, y = 0.923), was investigated seeking for an enhancement of the n-type electronic conductivity for its use as a mixed electron–proton conductor in hydrogen gas separation membrane applications. The materials were synthesized by the freeze-drying precursor method, and they were single phase after firing between 1300 and 1500 °C for x ≤ 0.8. The crystal structure changed from cubic (x ≤ 0.4) to rhombohedral (x ≥ 0.6) with increasing the molybdenum content. Transmission electron microscopy (TEM) investigations revealed an ordering of the oxygen vacancies with increasing Mo-content, giving rise to superstructure domains. The dependency of the conductivity with the oxygen and water partial pressure showed that these materials are good mixed electron–proton conductors under wet reducing conditions for x ≤ 0.4. The conductivity of the materials with x ≥ 0.6 was dominated by electrons, and they are expected to be less chemically stable d...
98 citations
TL;DR: In this article, the effect of lanthanum substitution by cerium oxide on the performance of perovskite-type oxide precursor for the oxidative steam reforming of ethanol was investigated.
Abstract: This paper investigates the effect of lanthanum substitution by cerium oxide on the performance of La 1− x Ce x NiO 3 ( x = 0, 0.05, 0.1, 0.4, 0.7 and 1.0) perovskite-type oxide precursor for the oxidative steam reforming of ethanol. All catalysts are active and selective to hydrogen but carbon deposition occurs except for La 0.90 Ce 0.10 NiO 3 . Increasing the Ce content decreases the amount of carbon deposited, which passes through a minimum at around 10 wt% of Ce and then increases. The higher resistance to carbon formation on La 0.90 Ce 0.10 NiO 3 catalyst is due to the smaller Ni crystallite size. Furthermore, the support also plays an important role on catalyst stability during ethanol conversion reaction. The reduced La 0.9 Ce 0.1 NiO 3 sample exhibits the highest amount of oxygen vacancies, which decreases as ceria content increases. This highly mobile oxygen reacts with carbon species as soon as it forms, and thus keeps the metal surface free of carbon, inhibiting deactivation.
97 citations
TL;DR: In this article, the authors reported that lanthanum tungstate, earlier believed to be La6WO12, is in fact La28−xW4+xO54+δ, where tungsten dissolves in lanthanium sites to form a stable solid-state electrolyte, exhibiting proton conduction by hydration at intermediate temperatures.
Abstract: This is the first paper reporting that lanthanum tungstate, earlier believed to be La6WO12, is in fact La28−xW4+xO54+δ , where tungsten dissolves in lanthanum sites to form a stable solid-state electrolyte, exhibiting proton conduction by hydration at intermediate temperatures.
95 citations
TL;DR: In this paper, the physicochemical properties of perovskite nano-particles were characterized by means of X-ray diffraction (XRD), thermogravimetry-differential thermal (TG-DTA) analysis, BET surface area and Xray photoelectron spectroscopy (XPS) analysis.
Abstract: In the present study, La 1– x Sr x CoO 3– δ ( x = 0.2, 0.3, 0.4, 0.5) perovskite nano-particles have been successfully prepared by EDTA–citrate complexing process and the catalytic performance was examined for the soot oxidation activity. The physio-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), thermogravimetry–differential thermal (TG–DTA) analysis, BET surface area and X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. TG–DTA analysis suggested that, in the temperature range of 350–500 °C, the pyrolysis of metal/nitrate/citrate/EDTA complexes takes place and the single phase La 1– x Sr x CoO 3– δ perovskite oxides can be formed at 900 °C and the phase formation has been confirmed by XRD analysis. The surface composition of the samples derived from XPS analysis indicated an impoverishment of lanthanum content at the surface with the increase of strontium content. For La 0.6 Sr 0.4 CoO 3– δ sample, Sr-enriched perovskite surface has been observed along with the more number of surface oxides (M(Sr, La, Co) O) resulting in higher catalytic activity for soot oxidation than the others.
91 citations
TL;DR: In this paper, the adsorbents are prepared using macroporous ordered silica foams (MOSF) as the host and the two sides of the silica layer (∼5 nm in thickness) are coated by two layers of lanthanum oxide each with a thickness of ∼2.3 nm, forming a unique sandwich-like wall structure.
Abstract: Novel phosphorus (P) adsorbents with a high adsorption capacity (up to 2.272 mmol g−1) and excellent adsorption performance in a low P concentration range of 1 mg L−1 have been successfully developed. The material achieves up to 96% P removal within 30 min with an initial concentration of 1 mg L−1. The adsorbents are prepared using macroporous ordered silica foams (MOSF) as the host. After modification by lanthanum species (La–MOSF), the two sides of the silica layer (∼5 nm in thickness) are coated by two layers of lanthanum oxide each with a thickness of ∼2.3 nm, forming a unique sandwich-like wall structure. Due to the very large pore size of La–MOSF (∼100 nm), after P adsorption the formed LaPO4 species are confined inside the pores without causing pore blocking, allowing for a high loading of lanthanum oxide and a high adsorption capacity. Moreover, the thin layer nature of lanthanum oxide facilitates the reaction between lanthanum oxide and phosphate ions, leading to the enhanced performance for the adsorption in low P concentration ranges. These rationally designed macroporous materials with outstanding performance have great potentials in water quality control and protection.
89 citations
TL;DR: Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolyte and is expected to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.
Abstract: Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolyte. Nanocrystalline perovskite of composition La0.6Ca0.4CoO3 with a unique cellular internal structure was prepared at 350 °C and then annealed in air at progressively higher temperatures in the range of 600-750 °C. The samples were characterized by electrochemical techniques and X-ray photoelectron spectroscopy. The area-specific electrocatalytic activity for oxygen evolution/oxygen reduction, the oxidation state of cobalt, and the crystallite size increased with annealing temperature, while the Tafel slope remained constant. These trends provide new insights into the role of the cobalt center in oxygen evolution and oxygen reduction, and how preparation conditions can be altered to tune the activity of the cobalt center for electrocatalysis. We expect these findings to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.
87 citations
TL;DR: In this paper, a series of iron-based La1−xFeO3−δ perovskites (with x ǫ = 0, 0.1, 0., 0.2, 0,0.3 and 0.4) were prepared by the self-combustion method using glycine as an ignition promoter.
Abstract: A series of iron-based La1−xFeO3−δ perovskites (with x = 0, 0.1, 0.2, 0.3 and 0.4) was prepared by the so-called self-combustion method using glycine as an ignition promoter. The chemical, structural and surface properties of these mixed oxides were thoroughly characterized before the determination of their activity in the total oxidation of methane. The catalytic data indicated a strong dependence of the methane conversion towards the catalyst elemental composition. A progressive Fe2O3 enrichment of the perovskite surface was clearly evidenced by XPS characterization when decreasing the lanthanum content of the solid. Such additional undesirable surface iron oxide induced an inhibiting effect on the catalytic activity. As a result, while the La1−xFeO3−δ (x = 0, 0.1, 0.2, 0.3, 0.4) perovskites presented moderated performances in methane total oxidation, the most efficient lanthanum iron-based perovskite is the stoichiometric LaFeO3 mixed-oxide that exhibits the most adapted surface and global composition, resulting in a CH4 conversion of 86% at 873 K.
TL;DR: In this paper, a single phase perovskite-type oxides were obtained as single phase and investigated in the partial oxidation of methane through temperature-programmed surface reactions (TPSR).
Abstract: LaCoO 3 and LaCo 0.8 Cu 0.2 O 3 perovskite-type oxides prepared by the polymerizable complex route were obtained as single phase and investigated in the partial oxidation of methane through temperature-programmed surface reactions (TPSR). Characterizations were carried out before and after the reactions under different feed streams CH 4 /O 2 /He = 2/1/37 and 5/1/64, and revealed a dynamic structural transformation in which the perovskite is collapsed towards lanthanum-based matrix and metal cobalt and copper. The copper-substituted perovskite showed better performance in the partial oxidation of methane leading to higher CH 4 conversion and higher syngas production than LaCoO 3 during the transient reaction. Furthermore, copper had significant effect against carbon deposition on the catalyst and it is suggested to be a very important dopant for perovskites applied in reactions with hydrocarbons.
TL;DR: In this article, a La(III)-loaded granular ceramic adsorbent, consisting mainly of different forms of metal oxide minerals, was developed for phosphorus removal from aqueous solution.
Abstract: A La(III)-loaded granular ceramic adsorbent, consisting mainly of different forms of metal oxide minerals, was developed for phosphorus removal from aqueous solution. Batch experiments were performed to investigate the effects of various experimental parameters, such as contact time (3–48 h), initial phosphorus concentration (5–25 mg/L), pH (2.0–12.0), temperature (20, 30 and 40 °C) and anions on phosphorus adsorption. The adsorption process was well described by a pseudo-second-order kinetic model and equilibrium was achieved at 30 h. The adsorption data closely fitted the Langmuir isotherm model at temperatures ranging from 20 °C to 40 °C. Thermodynamic study indicated a spontaneous, favorable and exothermic adsorption on the La(III)-loaded granular ceramic adsorbent. The optimum pH for phosphorus removal ranged from 7.0 to 9.0. Phosphorus adsorption was impeded by the presence of F − , followed by Cl − , SO 4 2− and NO 3 − and the adsorption process appeared to be controlled by a chemical precipitation process. The mechanism may involve ion complexation during subsequent adsorption of phosphorus on lanthanum hydroxides.
TL;DR: In this article, the authors investigated the optical nonlinearity of lead lanthanum borate glass embedded with gold nanoparticles and found that an absorption peak centered on 563 nm has been observed in heat treated samples.
Abstract: Synthesis, characterization and optical nonlinearity of lead lanthanum borate glass embedded with gold nanoparticles have been investigated. DSC thermogram shows characteristics glass transition temperature at Tg = 775 K. Glasses doped with Au were subjected to heat treatment at 823 K with different annealing time and then, slowly cooled to room temperature show striking ruby color. SAED and TEM analyses have confirmed that f.c.c. Au nanoparticles of ~ 40 nm size are present in these glasses. An absorption peak centered on 563 nm has been observed in heat treated samples, which is attributed to surface plasmon resonance of gold nanoparticles. Nonlinear optical studies with open aperture Z-Scan technique show saturable absorption for heat treated samples at low intensity and reverse saturable absorption in samples without heat treatment at high intensity.
TL;DR: In this paper, a defect model comprising an inherently disordered and partially occupied oxide ion sublattice is presented, which rationalizes hydration and ionic conduction of the materials in the undoped state.
TL;DR: In this paper, the olivine-type lanthanum and magnesium doped Li 0.99 La 0.01 Fe 0.9 Mg 0.1 PO 4 /carbon aerogel composite is synthesized via a simple solution impregnation process using carbon aerogels (CA) as templates, characterized by XRD, SEM, EDS, HR-TEM, galvanostastic charge/discharge test and EIS.
TL;DR: In this paper, a systematic liquid-liquid extraction of lanthanum and neodymium from aqueous nitric acid solutions using a mixture of two neutral extractants in kerosene has been investigated.
TL;DR: In this article, the dry reforming of CH 4 by CO 2 has been studied, between 300 and 900°C, over monometallic platinum and rhodium based catalysts supported on α-Al O 3 doped with La 2 O 3 and BaO.
TL;DR: In this paper, the A-site deficient lanthanum doped strontium titanate (LST) was used as a promising, redox-stable candidate for full ceramic anodes in Solid Oxide Fuel Cells (SOFCs).
TL;DR: In this article, a two-layer Aurivillius oxide with an orthorhombic space group A21am was refined by the Rietveld method with powder X-ray diffraction at room temperature.
Abstract: New Aurivillius ferroelectrics Na0.5La0.5Bi2Nb2−xWxO9 (NLBN-W, x = 0, 0.01, 0.02, 0.03, and 0.05) by lanthanum (La3+) and tungsten (W6+) co-substitution were prepared by using a solid-state reaction process. The crystal structure of Na0.5La0.5Bi2Nb1.98W0.02O9 (NLBN-W-0.02) was refined by the Rietveld method with powder X-ray diffraction at room temperature and it was confirmed to be a two-layer Aurivillius oxide with an orthorhombic space group A21am (a = 5.48754(8) A, b = 5.47967(9) A and c = 24.8523(4) A). The ferroelectric to paraelectric phase transition temperature (Tc) of NLBN-W-0.02 is around 501 °C, with prominent relaxation behavior. The NLBN-W-0.02 ceramics have a high piezoelectric coefficient (d33 = 31 pC N−1) and large remnant polarization (Pr = 15.1 μC cm−2). The decrease in Pr for the NLBN-W-0.02 ceramics after 107 switching cycles at 40 and 120 °C is only 2 and 9%, respectively.
TL;DR: In this paper, carboxylated graphene oxide complexes with lanthanum(III) were characterized by FT-IR, TG, TEM, AFM, and Raman, and the results showed that GeneO-La complexes have a good inhibitory effect under the concentration of 1.0 mg mL−1.
Abstract: The anticoagulation and antibacterial properties of biomaterials are crucial for biomedical applications, especially for blood-contacting materials. Herein, we prepare carboxylated graphene oxide complexes with lanthanum(III). The complexes were characterized by FT-IR, TG, TEM, AFM, and Raman. Results show that the lanthanum(III) has been coordinated on the graphene oxide sheet. The antibacterial property of the complexes is determined by the kinetics of bacterial growth and bacterial inhibition zone. The results show that GeneO–La complexes have a good inhibitory effect under the concentration of 1.0 mg mL−1. The anticoagulation property of complexes is evaluated by a hemolysis test and recalcification time test. The plasma recalcification time gradually decreases with the increasing concentration of complexes. The hemolysis rate is less than 5% at lower concentrations of complexes as consistent the Hormesis effect of rare earth elements. GeneO–La complexes have both antibacterial and anticoagulation properties, which indicates potential as blood-contact materials.
TL;DR: In this article, cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05,0.1 and 0.15) were synthesized successfully by hydrothermal method.
TL;DR: In this paper, solid oxide cells with thin strontium-and magnesium-doped lanthanum gallate electrolytes were used to achieve power densities of 1.06 W cm−2 at 550 °C and 0.81 W cm −2 at 500 °C when operated on humidified hydrogen and ambient air.
Abstract: Here we report solid oxide cells with thin strontium- and magnesium-doped lanthanum gallate electrolytes that yield power densities of 1.06 W cm−2 at 550 °C and 0.81 W cm−2 at 500 °C when operated on humidified hydrogen and ambient air. Cost-effective ceramic processing and chemical solution impregnation methods were utilized, yielding a dual micron- and nano-scale architecture that is essential for achieving good low-temperature performance.
TL;DR: In this article, the authors proposed a method for the extraction of rare earth metals from nitrate media with the binary extractant methyltrioctylammonium di(2,4,4-trimethylpentyl)phosphinate with the formation of extracted species of different composition in the organic phase.
TL;DR: Lanthanum (La( 3+)) substitution for bismuth (Bi(3+)) led to an enhancement in relaxation behavior for the KNBN-La ceramics, with a ferroelectric to paraelectric phase transition temperature (T(c)) of about 360 °C.
Abstract: Aurivillius ferroelectrics K0.25Na0.25La0.5Bi2Nb2O9 (KNBN-La) and K0.25Na0.25Bi2.5Nb2O9 (KNBN-Bi) were prepared by using solid-state reaction process. Rietveld refinements for the KNBN-La and KNBN-Bi were carried out by using powder X-ray diffraction at room temperature and they were confirmed to be two-layer Aurivillius oxides with orthorhombic space group A21am. The lattice parameters are a = 5.50468(10) A, b = 5.49217(10) A, and c = 25.05108(35) A for KNBN-La and a = 5.48867(6) A, b = 5.47895(6) A, and c = 25.10591(25) A for KNBN-Bi. Lanthanum (La3+) substitution for bismuth (Bi3+) led to an enhancement in relaxation behavior for the KNBN-La ceramics, with a ferroelectric to paraelectric phase transition temperature (Tc) of about 360 °C. The KNBN-La ceramics had a high remnant polarization (Pr) of 13.6 μC cm−2 and a field-induced strain of up to 0.031%. Particularly, the decrease in Pr for the KNBN-La ceramics after 108 cumulative switching cycles was only 6%.
TL;DR: In this paper, the electrolyte effects on the oxygen surface exchange coefficients of strontium-doped lanthanum manganates (LSM) were investigated using electrical conductivity relaxation technique.
TL;DR: In this paper, borate and phosphate were incorporated into CaMnO3 and borate into La1−ySryMnNO3−δ to achieve an increase in the electronic conductivity.
Abstract: In this paper we report the successful incorporation of borate and phosphate into CaMnO3 and borate into La1−ySryMnO3−δ. For CaMnO3, an increase in the electronic conductivity was observed, which can be correlated with electron doping due to the oxyanion doping favoring the introduction of oxide ion vacancies (as well as the higher valence of P5+ compared to Mn4+ in the case of phosphate doping). The highest conductivity at 800 °C was observed for CaMn0.95P0.05O3−δ, 43.0 S cm−1, in comparison with 7.6 S cm−1 for undoped CaMnO3 at the same temperature. For La1−ySryMnO3−δ the conductivity suffers a decrease for all compositions on borate doping, attributed to a reduction in the hole (Mn4+) concentration. In order to investigate the potential of these materials as SOFC cathodes, the chemical compatibility with Gd0.1Ce0.9O1.95 (CGO10) has also been investigated. For the calcium manganites, the lowest temperature examined without reaction was 900 °C, with minor amounts of Ca4Mn3O10 observed at 1000 °C. Composites of these cathode materials with 50% CGO10 were examined on dense CGO10 pellets and the area specific resistances (ASR) in symmetrical cells were determined. The ASR values, at 800 °C, were 1.50, 0.37 and 0.30 Ω·cm2 for CaMnO3, CaMn0.95B0.05O3−δ and CaMn0.95P0.05O3−δ, respectively. For the lanthanum strontium manganites, the B-doped compositions showed an improvement in the ASR values with respect to the parent compounds, despite the lower electronic conductivity. This may be due to an increase in ionic conductivity due to borate incorporation leading to the formation of oxide ion vacancies. Thus these preliminary results show that oxyanion doping has a beneficial effect on the performance of perovskite manganite cathode materials, and suggests that this doping strategy warrants further investigation in other perovskite cathode systems.
TL;DR: In this article, the polymerizable complex method was used to synthesize pure and calcium substituted lanthanum ferrite compounds, La1−−xCaxFeO3−−δ (x = 0, 0.05,0.1 and 0.2).
TL;DR: In this paper, the authors compared the flame retardancy of intumescent flame retardant ethylene-vinyl acetate (EVA/IFR) composites containing different metal oxides including lanthanide oxide, iron oxide, the mixture of iron oxide and lanthanides oxide, and Lanthanum ferrite nanocrystalline (LaFeO3).
Abstract: The objective of this work was to compare the flame retardancy of intumescent flame retardant ethylene–vinyl acetate (EVA/IFR) composites containing different metal oxides including lanthanide oxide, iron oxide, the mixture of iron oxide and lanthanide oxide, and lanthanum ferrite nanocrystalline (LaFeO3). A novel compound containing iron and lanthanum, LaFeO3 was successfully prepared. The EVA/IFR composites with these different coadditives were then fabricated through a melt blending process. Thermogravimetric analysis data showed that these different coadditives could increase the char residue formation. Cone calorimeter results revealed that these different coadditives and IFR could clearly change the decomposition behavior of EVA and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate, total heat release, average mass loss rate, average smoke extinction area, and so on. Moreover, significant improv...
TL;DR: In this paper, the highly c-axis-oriented polycrystalline material of apatite-type La9.50Si6O26.25 was prepared by isothermal heating of the sandwich type La2SiO5/La2Si2O7/La 2SiO 5 diffusion couple at 1873 K f.
Abstract: We have prepared the highly c-axis-oriented polycrystalline material of apatite-type La9.50Si6O26.25 by isothermal heating of the sandwich-type La2SiO5/La2Si2O7/La2SiO5 diffusion couple at 1873 K f...