查找使用阿拉丁产品的科研文献

Separation of La/Ce in rare earth polishing powder waste via Two-Stage hydrochloric acid leaching and corresponding leaching mechanism

Yang Li,Feifei Yang,Jing Xiong,Kejia Liu,Wanhai Xiao,Tao Qi,Zhipeng Dong,Yong Wang

Rare earth polishing powder waste (REPPW) usually contains lanthanum (La) and cerium (Ce) with content over 50 %, thus its recovery is important for the cyclic utilization of rare earth. In the traditional acid leaching process, La and Ce are simultaneously leached and required further separation. Based on their leaching behavior difference, a two-stage hydrochloric acid leaching process was proposed in this study to recover and primarily separate La and Ce in REPPW. With the optimal operation conditions, La enriched solution with a relative purity of 91.11 % and Ce enriched solution with a relative purity of 92.85 % were obtained and their recovery ratio were 59.47 and 85.15 %, respectively. After precipitation and calcination, products of La 2 O 3 with purity of 83.67 % and CeO 2 with purity of 93.38 % were obtained. Besides, individual leaching kinetics of La and Ce in low-acid leaching were studied using various shrinking core models. Based on the analysis of phase components and micromorphology evolution of REPPW during the leaching process, the leaching mechanism of REPPW was determined. Combined the leaching regularity with the fitting results, the leaching process of La was controlled by interfacial transfer and product layer diffusion, and the Ce was by product layer diffusion. The apparent activation energies of the LaOF and CeO 2 leaching reactions were 89.97 kJ/mol and 79.03 kJ/mol, respectively.

La-MOFs in situ loaded Al2O3 particles for effective removal of phosphate in water: characterization, application potential analysis, and mechanism

Ai Huiying,Zhang Zhiyong,Ji Yuxi,Xu Lei,Fu Ming-Lai,Yuan Baoling

Excessive phosphorus in water would cause eutrophication and deterioration of the ecological environment. Herein, the La-MOFs/Al 2 O 3 composite was successfully prepared by the in situ hydrothermal synthesis method for granulation, which was conducive to exerting the phosphate adsorption capacity and facilitating practical application. The materials were characterized by SEM, EDX, XRD, BET, FTIR, and Zeta. In addition, the adsorption performance of La-MOFs/Al 2 O 3 was evaluated through adsorption kinetics and isotherms, showing that the Langmuir adsorption capacity was 16.34 mgP·g -1 (25 °C) and increased with the water temperature. Moreover, the batch influence experiments of intimal pH, adsorbent dosage, coexisting ions, and stability tests were performed to analyze the potential for practical applications and verified through the natural micro-polluted water samples from Houxi River and Bailu Lake (China). The results indicated that the La-MOFs/Al 2 O 3 was suited to a wide pH range of 4 to 10 and the phosphate removal efficiency remained above 70% after continuous use for four times, exhibiting excellent stability. It also had excellent selectivity in the presence of SO 4 2- , Cl - , NO 3 - , and HCO 3 - , only decreased to 70.24% at high HCO 3 - ion concentration of 60 mg/L, respectively. And the La-MOFs/Al 2 O 3 had excellent adsorption of total phosphorus, phosphate, and organic phosphorus in the actual river and lake water and completely removed dissolved phosphorus. Finally, a phosphate adsorption mechanism model involved in electrostatic interaction and ligand exchange was proposed. Therefore, La-MOFs/Al 2 O 3 could be considered to be an excellent phosphorus adsorbent for application in the actual water environmental remediation. Graphical abstract

Microstructure and mechanical properties of highly dense Si3N4 ceramics with ZrN–AlN–Re2O3 (Re=Yb, Y, Nd, Ce, La) additives

Jun-Wei Huang,Xiao-Feng Dong,Xiao-An Lv,Xiao-Na Ren,Chang-Chun Ge

The Si 3 N 4 ceramics with ternary ZrN–AlN–Re 2 O 3 (Re=Yb, Y, Nd, Ce, La) and ZrN–AlN system as sintering additives were prepared by hot-pressed sintering with vacuum environment at 1750°C-30min–30MPa. Subsequently, the effect of the ternary additives system with 2 wt% Re 2 O 3 on phase transformation, grain boundary phases, microstructure, and mechanical properties of the Si 3 N 4 ceramics were investigated firstly. All samples achieved the high β-Si 3 N 4 phases transformation (≥98.86%), while the grain boundary phases Re x Zr 1-x O (4-x)/2 and Yb 2 Si 2 O 7 were detected in the sintered Si 3 N 4 ceramics with Re 2 O 3 additives. Additionally, compared with Si 3 N 4 ceramic not contain Re 2 O 3 additives, the Si 3 N 4 ceramics added Re 2 O 3 additives presented the textured microstructure with more elongated rodlike β-Si 3 N 4 grains based on the XRD and SEM results. Consequently, the sample S-Ce with added CeO 2 additive shows the highest relative density of 99.85% and optimal fracture toughness of 8.75 ± 0.36 MPa m 1/2 . The sample S–Nd with added Nd 2 O 3 additive presented a highest bending strength of 1061.78 ± 41.76 MPa. Sample S–Yb with added Yb 2 O 3 additive presented the maximum Vickers hardness of 16.35 ± 0.07 GPa. The results of this study can provide a helpful reference for the preparation of high-performance Si 3 N 4 ceramics.

Lightweight and Flexible Bi@Bi-La Natural Leather Composites with Superb X-ray Radiation Shielding Performance and Low Secondary Radiation

Qian Li,Rui Zhong,Xiao Xiao,Jiali Liao,Xuepin Liao,Bi Shi

A high-shielding, low secondary radiation, lightweight, flexible, and wearable X-ray protection material was prepared by coimpregnating La2O3 and Bi2O3 nanoparticles in natural leather (NL) with an additional Bi2O3 coating at the bottom surface of the leather. The prepared Bi28.2@Bi3.48La3.48–NL (28.2 and 3.48 mmol·cm–3 are the loading contents of elements) showed excellent X-ray shielding ability (65–100%) in a wide energy range of 20–120 keV with reduced scattered secondary radiation (30%). The bottom surface coating played a critical role in enhancing the X-ray attenuation and reducing the scattered secondary radiation by reflecting and deflecting incident X-ray photons. Excellent mechanical property with superb bending resistance of the NL matrix was properly maintained, and its tensile strength and tearing load were 15.39 MPa and 25.81 N·mm–1, respectively. This lightweight and wearable high-performance protection material can facilitate safety and comfortability during intensive activities of practitioners in the health care industry.

High performance and colossal permittivity of (Nb+La) co-doped rutile TiO2 ceramics induced by composition regulation

Yang Yu,Wei-Li Li,Wei-Dong Fei

Application of a novel endocrine disruptor bisphenol A electrochemical sensor based on analogous heterostructure characteristics of La-doped Yb2O3 nanomaterials

Xiaojiao Wang,Yang Li,Yuanzhen Zhou,Yijia He

Bisphenol A (BPA) is one of the most prevalent environmental endocrine disrupting chemicals. In this present paper, a facile BPA sensor was successfully fabricated based on a La-doped Yb2O3 nanorod modified carbon paste electrode (La–Yb2O3/CPE). La-doped Yb2O3 nanorods were synthesized using a one step hydrothermal synthesis method and further investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometric response analysis were applied to characterize the electrochemical properties of the sensor. Under the optimal conditions, the oxidation current increased linearly with increasing the concentration of BPA in the range of 0.04 to 15 μM with a detection limit of 0.013 μM. The prepared La-doped Yb2O3 nanomaterial modified electrode showed good reproducibility, stability and anti-interference ability. Furthermore, this newly developed sensor was further adopted to measure BPA in tap water and milk samples. The possible electrocatalytic sensing mechanism is discussed.

Microwave-assisted synthesis of La(OH)3/BiOCl n-n heterojunctions with high oxygen vacancies and its enhanced photocatalytic properties

Zhuo Zhou,Haiming Xu,Dongya Li,Zhongwei Zou,Dongsheng Xia

La(OH) 3 /BiOCl n-n heterojunction (BCL) was successfully fabricated by facile microwave technique. Photocatalytic performance experiments confirmed that BCL-20 can degrade 20 mg/L tetracycline hydrochloride (TC-HCl) about 85% in 60 min, which is 2 and 0.5 times higher than that of BiOCl and La(OH) 3 , respectively. The photocatalytic mechanism reveals that the co-effect of oxygen vacancies (OVs) and rebuilt internal electric field induced by heterostructure not only broaden the light-responsive range but also augment the separation efficiency of photogenerated carriers, thus improving the photocatalytic properties of BCL. This work provides a new avenue for improving the photocatalytic performance of Bi-based photocatalysts by heterojunction and OVs.

CO2 hydrogenation to methanol over Cu catalysts supported on La-modified SBA-15: The crucial role of Cu–LaOx interfaces

Kun Chen,Huihuang Fang,Simson Wu,Xi Liu,Jianwei Zheng,Song Zhou,Xinping Duan,Yichao Zhuang,Shik Chi Edman Tsang,Youzhu Yuan

The direct hydrogenation of CO 2 to methanol has become a very active research field because CO 2 can be prospectively recycled to mitigate greenhouse effect and store clean synthetic fuels. This reaction can be catalyzed by supported Cu catalysts and the catalysts display strong support or promoter effects. Sintering of Cu species accelerates the separation of Cu–oxide interfaces, reduces the active component, and diminishes the methanol selectivity. In this work, we report a Cu catalyst supported on La-modified SBA-15, where the Cu–LaO x interface is generated through the interaction of highly dispersed Cu nanoparticles with LaO x species bedded into the SBA-15 pore wall. The optimized Cu 1 La 0.2 /SBA-15 catalyst can achieve methanol selectivity up to 81.2% with no deterioration in activity over 100 h on stream compared with the La-free catalyst. A thorough study reveals that La species not only significantly improve the CO 2 adsorption but also enhance Cu dispersion to produce well-dispersed active sites. The H/D exchange experiments show that the methanol synthesis displays a strong thermodynamic isotope effect and the Cu–LaO x interface plays a crucial role for the methanol synthesis rate in CO 2 /D 2 feed. In situ DRIFTS studies reveal that *HCOO and *OCH 3 species are the key intermediates formed during the activation of CO 2 and methanol synthesis over the Cu 1 La 0.2 /SBA-15 catalyst.

Thermal Emittance of $$\hbox {La}_{0.7}\hbox {Ca}_{0.3-x}\hbox {K}_x\hbox {MnO}_3$$ Coatings on Aluminum Substrate

Fan Desong,Sun Si,Guo Li

A novel thermal control coating was presented based on the thermochromism of manganite. The pigment of K-doped manganite nanoparticles was dispersed into polymer matrix to prepare the coating with curing below 200  \(^{\circ }\) C. The nanoparticles size mainly distributes around 100–200 nm, and it shows a comparable stoichiometric ratio. The phase transition of the nanoparticles was observed from ferromagnetic metallic to paramagnetic insulator state. With increasing K doping level, the phase transition temperature increases, achieving controllable adjustment. Coating surface with and without pore defect was obtained by different polymer matrix. A sharp emittance variation was observed with increasing temperature in K-doped coating. The variation magnitude of emittance is up to 0.46, which is attractive to space thermal control. It is suggested that the pigment content of 50 wt% is sufficient to realize a large emittance variation.

A novel strategy for constructing mesoporous solid superbase catalysts: bimetallic Al–La oxides supported on SBA-15 modified with KF

Ning Liu,Zhimin Wu,Meng Li,Shanshan Li,Yongfei Li,Rongdong Yu,Langsheng Pan,Yuejin Liu

Bimetallic Al–La oxides were conjointly precoated on SBA-15 prior to the introduction of potassium fluoride to achieve solid superbases at low temperature by a modified wetness impregnation method. This breaks the tradition of decomposition of KNO3 at high temperature and gives rise to a new approach to generating superbasic sites on SBA-15. The physico-chemical characteristics of the prepared KF/Al–La@SBA-15 materials were investigated using FT-IR, XRD, TG-DTG, N2 adsorption–desorption, TEM, SEM-EDS, acid–base titration, Hammett indicators and CO2-TPD measurements. The results demonstrated that the addition of Al species promoted the dispersion behavior of La species inside the channels, and the bimetallic species could synergistically protect the mesoporous structures of SBA-15 against KF corrosion. With increasing Al content, KF/Al–La@SBA-15 exhibited a long-range ordering of the pores with relatively narrow pore size distribution as well as high specific surface area. The research results showed that the KF/Al–La@SBA-15 (0.4) catalyst possessed a total basicity up to 0.79 mmol g−1 and superbasicity with a strength of 26.5. The catalytic activity of the prepared materials was evaluated in the ring-opening reaction of propylene oxide with methanol. Compared with the SBA-15 supported monometallic oxide (Al or La) catalysts, KF/Al–La@SBA-15 (0.4) exhibited the highest catalytic activity for the ring-opening reaction of propylene oxide with methanol. This is associated with the synergistic effects between Al and La species and the high dispersion of active components on the SBA-15 support.

Effect of limited current on ultrarapid densification and giant dielectric properties of flash sintering (La, Ta) co-doped TiO2 ceramics

Yang Zaizhi,Wang Xi,Zhang Liang,Li Hailing,Zhang Hui,Xu Dong

Flash sintering is considered a promising energy-saving and efficient technology for preparing high-temperature ceramics. The effects of limited current on flash sintering parameters, microstructure, and electrical properties of (La 1/2 , Ta 1/2 ) 0.02 Ti 0.98 O 2 ceramic were investigated by the XRD, SEM, XPS, and precision impedance analyzer. With limiting current increase, the grain size of flash sintering sample increases gradually, and the relative density increases first and then decreases. The average grain size is about 1 μm, and the highest relative density is 96.9%. Joule heating runaway and oxygen vacancy defect lead to rapid densification of flash sintering La and Ta co-doped TiO 2 ceramics. According to the EPDD model, doped La 3+ and Ta 5+ ions increase the concentration of oxygen vacancies and free electrons, lead to local polarization of carriers, and obtain a giant dielectric constant of ε ’  = 7.6 × 10 4 and low dielectric loss of tanδ = 0.11. At high temperature, electrons break free from the constraints of defect clusters and accumulate at the interface, leading to interface polarization due to the IBLC model. The giant dielectric properties originate from the combined effect of EPDD and IBLC model.

Chemiresistive detection of H2 at near room temperature by porous In2O3 nanotubes co-sensitized with La-dopant and Pd-modifier

Xuping Li,Yanwei Li,Xingtang Xu,Xiaohua Wang,Guang Sun,Bo Zhang,Yan Wang,Jianliang Cao

Metal oxide semiconductor (MOS)-based hydrogen (H 2 ) sensor that can work at room or near room temperature has attracted an increasing concern owing to its potential application in hydrogen storage and utilization. Herein, a co-sensitization strategy by La doping and Pd decoration is proposed to realize the detection of H 2 at near room temperature (50 °C) on In 2 O 3 porous nanotubes (PNTs). The In 2 O 3 PNTs were prepared via a solvothermal method and then sequentially doped with La 3+ and decorated with Pd nanoparticles via an immersion, freeze-drying and calcination route and a chemical reduction method, respectively. The results of gas-sensing measurements indicated that after a compositional evolution from In 2 O 3 to La-doped In 2 O 3 (La-In 2 O 3 ) and Pd-decorated La-In 2 O 3 (Pd/La-In 2 O 3 ), the fabricated H 2 sensor showed a higher sensitivity at lower operating temperature. At a near room temperature of 50 °C, the response of the best Pd/La-In 2 O 3 sensor to 50 ppm H 2 was as high as 8.34, increasing about 4.85, 1.20 and 1.15 folds compared to the In 2 O 3 (1.72 at 160 °C), La-In 2 O 3 (6.97 at 150 °C) and Pd/In 2 O 3 (7.24 at 80 °C) sensors, respectively. The sensitization effects and mechanism of La dopant and Pd modifier as well as their synergistic effects were discussed in detail.