Ni-Al layered double hydroxides electrodeposition from a chloride solution

Ni-Al LDHs was electrodeposited from a NiCl₂-AlCl₃ solution. In order to analyze the electrodeposition process, electrolytes with initial Al content range of 0–20% were used. With increasing Al content in the sample, the preferred orientations of (0 0 3) and (0 0 6), increased crystallinity, and decreased interlayer spacing were observed from the XRD results. A dissolution–recrystallization of (0 0 3) plane was detected among the Ni-Al LDHs from the strongly alkaline solution soaking results, which was found to be conducted easily in high Al-containing samples. The pH of the Al-containing electrolyte was much lower than that of pure NiCl₂ solution because lower pH was needed to start a precipitation reaction in the AlCl₃-NiCl₂ solution. The electrodeposition yield and current efficiency were found to decrease obviously in the electrolytes with initial Al content higher than 10%, which was attributed to the increasing Al content in the sample and diffusion of the complex ions. The electrodeposition pattern was in-situ in the electrolyte initially containing 10% Al, then, it developed toward and off in-situ in electrolytes initially containing 0–10% and 10–20% Al.     

类水滑石材料在核废水处理领域的应用

核能已成为我国能源结构的重要组成部分, 但含放射性物质的废水所带来的危害不容忽视. 如何高效解决核废水污染问题迫在眉睫. 类水滑石材料是一类阴离子型粘土化合物, 因其层板组成及层间阴离子种类的可调控性、 较大的比表面积及粒径和形貌的可调控性等特点已在含放射性核素废水的处理中崭露头角. 本文主要阐述了类水滑石材料对废水中放射性核素的吸附行为及其作用机制, 探讨了存在的问题及可能的解决方法, 并对其发展前景进行了展望.     

Electrochemical Approach for the Production of Layered Double Hydroxides with a Well-Defined Co/MeIII Ratio

Layered double hydroxides (LDHs) have been widely studied for their plethora of fascinating features and applications. The potentiostatic electrodeposition of LDHs has been extensively applied in the literature as a fast and direct method to substitute classical chemical routes. However, the electrochemical approach does not usually allow for a fine control of the M^II/M^III ratio in the synthesized material. By employing a recently proposed potentiodynamic method, LDH films of controlled composition are herein prepared with good reproducibility, using different ratios of the trivalent (Fe or Al) to bivalent (Co) cations in the electrolytic solution. All the obtained materials are shown to be effective oxygen evolution reaction (OER) catalysts, and are thoroughly characterized by a multi-technique approach, including FE-SEM, XRD, Raman, AES and a wide range of electrochemical procedures.     

LDHs薄膜基纳米荧光传感器的制备及其研究进展

层状复合氢氧化物(LDHs)是一种层板金属元素和层间离子可调的无机层状材料,利用其独特的插层组装特性,基于静电、氢键、范德华力等相互作用力,功能性荧光客体分子可与LDHs纳米片复合构筑多功能荧光薄膜材料.LDHs薄膜基荧光材料用于荧光传感器,在有机挥发性气体(VOCs)、温度、压力、重要生物分子等的检测中显示了良好性能.本文总结了LDHs复合薄膜的制备方法以及近年来其在纳米荧光传感领域的进展,并对其未来发展做出了展望.     

A Prospect for Environmental Remediation of Perchlorate via Cost-Effective Pinus Leaves and Dandelion Flower Powder-based Layer Double Hydride (LDH) Sorbents

In this study, pine leaves powder (PiP) and dandelion flower powder (DFP) were repurposed to synthesize layered double hydroxides (LDHs) to form a base for sorbents used in perchlorate remediation from wastewater. The effects of the adsorbent dose, pH, thermodynamics, and coexisting ions were evaluated in batch experiments. The results revealed that 0.1 g adsorbent (PiP-LDH and DFP-LDH) removed 97% and 93% of perchlorate contaminants, respectively. In this study, the correlation coefficient of pseudo-second-order was higher than pseudo-first-order for all the LDHs. The kinetic and isotherm studies showed the best uptake of perchlorate in the short time was by PiP-LDH, followed by DFP-LDH (20 min and 40 min, respectively). The calculated and experimental values of adsorption at the equilibrium state also concurred with the pseudo-second-order model. The prepared LDHs were mesoporous. The surface area of PiP-LDH provided more adsorption sites, rendering it more suitable for perchlorate adsorption compared with the other two LDHs. The model suggests Physico-chemical interactions behind the sorption of perchlorate by LDHs. The adsorption was more influenced by anions i.e, PO₄³⁻ > SO₄²⁻ > NO₃ than monovalent anions due to the increase in the charge radius values. The prepared LDHs could be of great benefit to the environmental remediation of wastewater bodies.     

Two Coordination Polymers Constructed from Pillared M–O (M = Na+ or Ba2+) Subunits with 3‐Formyl‐4‐hydroxybenzenesulfonic Acid as Ligand

Two new coordination polymers, [Na(H₂L)(H₂O)₂]_n ( 1 ) and [Ba(H₂L)₂(H₂O)]_n ( 2 ) (H₃L = 3‐formyl‐4‐hydroxybenzenesulfonic acid) were synthesized and structurally characterized. The H₂L^– ligand shows three different bridging modes, μ₃ in 1 , μ₃ and μ₄ in 2 . Compound 1 presents a 2D pillared structure, whereas 2 forms a 3D framework. Both 1 and 2 show blue luminescence at 380 nm in aqueous solution, however, their solid state emissions are at 406 and 446 nm, respectively.     

Facile Synthesis of Al-pillared Mesoporous Montmorillonite Assisted with Concentrated Al13 Solution

Al-pillared mesoporous montmorillonite was facilely synthesized from concentrated Al13 solution obtained by vacuum concentrating-ultrasonic pillaring strategy.Concentrated Al13 solution could reduce the process of pillare and increase pillaring efficiency.The absolute value of layer distance could be increased by 0.96 nm via concentrated Al13 solution pillare.27Al NMR indicates that Al Keggin ions of concentrated Al13 are arranged in a more regular way by vacuum concentrating method.The Al-pillared mesoporous montmorillonite from concentrated Al13 solution has bigger specific surface area and even pore size distribution which were characterized by X-ray diffraction（XRD） and nitrogen adsorption measurement.Furthermore the catalytic activity of Ai-pillared montmorillonite loaded Ni and Mo catalysts was tested by the hydrodesulfurization of thiophene.The thiophene conversion reached 77.5％,which was higher than the corresponding value reported in the literature.     

Unique coordination of pyrazine in T[Ni(CN)4]·2pyz with T=Mn, Zn, Cd

The materials under study, T[Ni(CN)₄]·2pyz with T=Mn, Zn, Cd, were prepared by separation of T[Ni(CN)₄] layers in citrate aqueous solution to allow the intercalation of the pyrazine molecules. The obtained solids were characterized from chemical analyses, X-ray diffraction, infrared, Raman, thermogravimetry, UV-Vis, magnetic and adsorption data. Their crystal structure was solved from ab initio using direct methods and then refined by the Rietveld method. A unique coordination for pyrazine to metal centers at neighboring layers was observed. The pyrazine molecule is found forming a bridge between Ni and T atoms, quite different from the proposed structures for T=Fe, Ni where it remains coordinated to two T atoms to form a vertical pillar between neighboring layers. The coordination of pyrazine to both Ni and T atoms minimizes the material free volume and leads to form a hydrophobic framework. On heating the solids remain stable up to 140 °C. No CO₂ and H₂ adsorption was observed in the small free spaces of their frameworks.     

Synthesis, Characterization and Catalysis of New Pillared Anionic Clays by [GaW_(11)O_(39)M(H_2O)]~(7-)(M=Mn~(2 ),Co~(2 ) or Ni~(2 ))

ＩｎｔｒｏｄｕｃｔｉｏｎＡｎｉｏｎｉｃｃｌａｙｓ（ｌａｙｅｒｅｄｄｏｕｂｌｅｈｙｄｒｏｘｉｄｅｓ）ａｒｅｉｍｐｏｒｔａｎｔｌａｙｅｒｅｄｍａｔｅｒｉａｌｓ．Ｔｈｅｇｅｎｅｒａｌｆｏｒｍｕｌａｉｓ［Ｍ２＋（１－ｘ）Ｍｘ３＋（ＯＨ）２］ｘ＋Ａｎ－ｘ／ｎｍ...     

Synthesis and properties of pyrazine-pillared Ag3Mo2O4F7 and AgReO4 layered phases

The new pyrazine-pillared solids, AgReO₄(C₄H₄N₂) (I) and Ag₃Mo₂O₄F₇(C₄H₄N₂)₃ (C₄H₄N₂=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150 °C and characterized using single crystal X-ray diffraction (I—P2₁/c, No. 14, Z=4, a=7.2238(6) Å, b=7.4940(7) Å, c=15.451(1) Å, β=92.296(4)°; II—P2/n, No. 13, Z=2, a=7.6465(9) Å, b=7.1888(5) Å, c=19.142(2) Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains in I are bonded to three perrhenate ReO₄^- tetrahedra per layer, while each layer in II contains sets of three edge-shared Ag(pyz) chains (π-π stacked) that are edge-shared to four Mo₂O₄F₇^3- dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150-175 °C, to produce crystalline AgReO₄ for I, and Ag₂MoO₄ and an unidentified product for II. Both pillared solids exhibit strong orange-yellow photoemission, at 575 nm for I and 560 nm for II, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76 eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.