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Yuanjie Yi, Jia Wen, Guangming Zeng, Taotao Zhang, Fenghu Huang, Haiyan Qin, Shiyu Tian
Three amendments including limestone, MnO2 and natural zeolite were assessed for their stabilisation effects on Zn, Cu, Pb and Cd in sediment of east Dongting Lake, mid-south China. The metals were first subject to pollution status and potential ecological risk assessment to identify the current and potential hazards to ecology. Speciation of the metals in the sediment treated with amendments was then carried out by BCR sequential extraction procedure in order to evaluate metal contents and their potential mobility...
October 18, 2016: Environmental Science and Pollution Research International
Katie A Cychosz, Rémy Guillet-Nicolas, Javier García-Martínez, Matthias Thommes
This review focuses on important aspects of applying physisorption for the pore structural characterization of hierarchical materials such as mesoporous zeolites. During the last decades major advances in understanding the adsorption and phase behavior of fluids confined in ordered nanoporous materials have been made, which led to major progress in the physisorption characterization methodology (summarized in the 2015 IUPAC report on physisorption characterization). Here we discuss progress and challenges for the physisorption characterization of nanoporous solids exhibiting various levels of porosity from micro- to macropores...
October 19, 2016: Chemical Society Reviews
Mariya V Shamzhy, Pavla Eliašová, Dana Vitvarová, Maksym V Opanasenko, Daniel S Firth, Russell E Morris
Germanosilicate zeolites often suffer from low hydrothermal stability due to the high content of Ge. Herein, we investigated the post-synthesis introduction of Al accompanied by stabilization of selected germanosilicates by degermanation/alumination treatments. The influence of chemical composition and topology of parent germanosilicate zeolites (ITH, IWW, and UTL) on the post-synthesis incorporation of Al was studied. Alumination of ITH (Si/Ge=2-13) and IWW (Si/Ge=3-7) zeolites resulted in the partial substitution of Ge for Al (up to 80 %), which was enhanced with a decrease of Ge content in the parent zeolite...
October 18, 2016: Chemistry: a European Journal
S Greiser, M Hunger, C Jäger
(29)Si{(27)Al} TRAPDOR MAS NMR was applied to two faujasite-type zeolites with Si/Al ratios of 1.3 (Na-X) and 2.7 (Na-Y). The aim of this test study is to show that different Q(4)(mAl) sites (m =4, 3, 2, 1) can be distinguished by differently strong TRAPDOR effects (ΔS/S0). Indeed, it was found that the TRAPDOR effect depends on the number m of AlO4 units connected to the Q(4) silicon tetrahedrons. For Na-X, the measured ΔS/S0 values are 1 : 0.81 : 0.56 for Q(4)(4Al), Q(4)(3Al) and Q(4)(2Al), respectively (normalized to Q(4)(4Al))...
October 8, 2016: Solid State Nuclear Magnetic Resonance
Alexandra Ioana Lupulescu, Wei Qin, Jeffrey D Rimer
Nonclassical mechanisms of crystal growth often involve the formation of amorphous precursors that play a direct role in what is generally referred to as crystallization by particle attachment (or CPA). One of the most studied CPA systems in literature is zeolite MFI, which is a microporous crystal with siliceous (silicalite-1) and aluminosilicate (ZSM-5) isostructures. The self-assembly, microstructural evolution, and mechanistic role of nanoparticle precursors (1 - 6 nm) during silicalite-1 crystallization have been the subjects of prior investigation by combined experimental and modeling techniques...
October 17, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Jeonghun Kim, Christine Young, Jaewoo Lee, Min-Sik Park, Mohammed Shahabuddin, Yusuke Yamauchi, Jung Ho Kim
Carbon nanotubes (CNT) grown on nanoporous carbon (NPC), which yields coexisting amorphous and graphitic nanoarchitectures, have been prepared on a large scale from zeolitic imidazolate framework (ZIF) by introducing bimetallic ions (Co(2+) and Zn(2+)). Interestingly, the hybrid Co/Zn-ZIF-derived NPC showed rich graphitic CNTs on the surface. This NPC was utilized for a coin-type supercapacitor cell with an aqueous electrolyte, which showed enhanced retention at high current density and good stability over 10 000 cycles...
October 17, 2016: Chemical Communications: Chem Comm
Gunther Brunklaus, Hubert Koller, Stacey I Zones
Internal defect SiOH and SiO(-) groups evolve during the structure formation of high-Si zeolites in the presence of a cationic organic structure-directing agent (SDA). These negatively charged defects do not completely disappear upon calcination. Herein we investigate the clustering of defect groups and their location within the pore walls of four zeolites. ZSM-12, ZSM-5, and SSZ-74 have three clustered SiOH groups which are hydrogen-bonded to SiO(-) , whereas SSZ-24 has only two. These defects interact with the structure-directing quaternary ammonium ions preferably close to the charge center, unless steric shielding is present...
October 14, 2016: Angewandte Chemie
Nataliia Popovych, Pavlo Kyriienko, Sergiy Soloviev, Rafal Baran, Yannick Millot, Stanislaw Dzwigaj
Silver has been identified in the framework of AgxSiBEA zeolites (where x = 3-6 Ag wt%) by the combined use of XRD, (109)Ag MAS NMR, FTIR, diffuse reflectance UV-visible, EPR and XPS spectroscopy. The incorporation of Ag ions into the framework of SiBEA zeolite has been evidenced by XRD. The consumption of OH groups as a result of their reaction with the silver precursor has been monitored by FTIR and photoluminescence spectroscopy. The changes in the silver state as a function of Ag content and thermal and hydrogen treatment at 573 K have been identified by (109)Ag MAS NMR, EPR, DR UV-visible, TEM and XPS investigations...
October 14, 2016: Physical Chemistry Chemical Physics: PCCP
Christine Young, Rahul R Salunkhe, Jing Tang, Chi-Chang Hu, Mohammed Shahabuddin, Ekrem Yanmaz, Md Shahriar A Hossain, Jung Ho Kim, Yusuke Yamauchi
Nanoporous carbon materials are a versatile source of carbons that would be useful in applications ranging from electronics to electrochemical energy storage. Here, we focus on nanoporous carbon materials prepared by direct carbonization of zeolitic imidazolate frameworks (ZIF-8) towards supercapacitor applications. Several types of nanoporous carbons have been prepared by varying the applied carbonization temperature. The symmetric devices assembled using nanoporous carbon electrodes were tested for their optimal performance in the electrolyte of sulfuric acid solution...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Minju Thomas, Rajith Illathvalappil, Sreekumar Kurungot, Balagopal N Nair, Abdul Azeez Peer Mohamed, Gopinathan M Anilkumar, Takeo Yamaguchi, U S Hareesh
Nitrogen containing mesoporous carbon obtained by the pyrolysis of graphene oxide (GO) wrapped ZIF-8 (Zeolitic Imidazolate Frameworks-8) micro crystals is demonstrated to be an efficient catalyst for the oxygen reduction reaction (ORR). ZIF-8 synthesis in the presence of GO sheets helped to realise layers of graphene oxide over ZIF-8 microcrystals and the sphere like structures thus obtained, on heat treatment, transformed to highly porous carbon with a nitrogen content of about 6.12 % and surface area of 502 m2/g...
October 12, 2016: ACS Applied Materials & Interfaces
Shunmugavel Saravanamurugan, Anders Riisager, Esben Taarning, Sebastian Meier
Glucose isomerisation to fructose can occur by different pathways and the mechanism of zeolite-catalysed glucose isomerisation in methanol has remained incompletely understood. Herein, the mechanism is studied using an (1)H-(13)C HSQC NMR assay resolving different fructose isotopomers. We find that zeolite-catalysed glucose isomerisation proceeds predominantly via a hydride shift into the pro-R position of fructose, thus resembling the stereoselectivity of the enzymatic isomerisation process.
October 11, 2016: Chemical Communications: Chem Comm
Dawei He, Danhua Yuan, Zhijia Song, Yansi Tong, Yaqi Wu, Shutao Xu, Yunpeng Xu, Zhongmin Liu
High silica zeolite Y with a SiO2/Al2O3 ratio of 7.76 is successfully synthesized with tetraethylammonium hydroxide (TEAOH) as a structure-directing agent. The high silica zeolite Y shows outstanding high temperature thermal stability and hydrothermal stability.
October 11, 2016: Chemical Communications: Chem Comm
S Takahashi, Y Kurita, T Ikeda, M Miyamoto, S Uemiya, Y Oumi
The synthesis of a novel layered silicate SSA-1 (SSA: silicate synthesized with a quaternary amine) was achieved in the SiO2-H2O-TEAOH (TEAOH: tetraethylammonium hydroxide - as an organic structural directing agent) system. The crystal structure of SSA-1 involved two silicate layers composed of bre [10T]-type CBU (Composite Building Unit) and TEAOH in interlayers. The topotactic transformation of SSA-1 by calcination was examined, resulting in a porous material (PML-1: porous material transformed from a layered silicate) with a 108 m(2) g(-1) BET surface area and 0...
October 18, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Siwar Chibani, Mouheb Chebbi, Sébastien Lebègue, Laurent Cantrel, Michael Badawi
Silver modified zeolites with a mordenite structure can capture volatile iodine compounds (I2 and ICH3) which can be released during a severe nuclear accident. However under these particular conditions, molecules such as CO and H2O present in the containment atmosphere are expected to inhibit the adsorption of iodine compounds. In the present work, periodic density functional theory calculations have been carried out to investigate the interaction of I2, ICH3, H2O and CO molecules in silver-exchanged mordenite with various Si/Al ratios with the aim of finding values that favor a selective adsorption of I2 and ICH3...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Najam U Qadir, Syed A M Said, Rached B Mansour, Khalid Mezghani, Anwar Ul-Hamid
Conventional small-scale adsorption chillers generally employ silica-gel/water or zeolite/water working pairs given the relatively high level of mesoporosity and water affinity in these adsorbent materials. However, the coefficient of performance (COP) and specific cooling power (SCP) evaluated for the adsorption chiller using these adsorbent/adsorbate pairs cannot be still considered practically feasible in the context of a commercial system. Metal organic frameworks (MOFs) are not only characterized by much higher water adsorption capacities than these materials, but also can be mass-produced using much simpler methods than the template-assisted synthesis routes of most zeolites...
October 4, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Zhifei Wang, Xuejiao Tang, Xiaoxiao Wang, Dandan Yang, Chao Yang, Yongbing Lou, Jinxi Chen, Nongyue He
Incorporation of CuS nanoparticles into the framework of ZIF-8 provides a chance to integrate near-infrared (NIR) light/low pH triggered release and chemo-photothermal therapy into one system. For the first time, we observed that the framework of ZIF-8 could be disintegrated at pH 7.4 under NIR laser irradiation.
October 6, 2016: Chemical Communications: Chem Comm
Fengdong Qu, Huifang Jiang, Minghui Yang
The rational design of nanoscale metal oxides with hollow structures and tunable porosity has stimulated tremendous attention due to their vital importance for practical applications. Here, we report the designed synthesis of ZnO/ZnCo2O4 hollow core-shell nanocages (HCSNCs) through a metal-organic framework (MOF) route. The strategy includes the synthesis of a zeolite imidazolate framework-8 (ZIF-8)/Co-Zn hydroxide core-shell nanostructure precursor and subsequent transformation to ZnO/ZnCo2O4 HCSNCs by thermal annealing of the as-prepared precursor in air...
September 15, 2016: Nanoscale
Roberto Conti, Laura Pezzolesi, Rossella Pistocchi, Cristian Torri, Patrizio Massoli, Daniele Fabbri
The study evaluated the growth of Desmodesmus communis on column photobioreactor and its thermochemical treatment by catalytic pyrolysis using HZSM-5 zeolite. D. communis showed good results in terms of growth (0.05gL(-1)d(-1)). Analytical pyrolysis of original algae and derived bio-oil mixed with zeolite was used as a screening method in order to gather information on the cracking process. Preparative pyrolysis on bench scale reactor was performed on algae biomass over a zeolite bed at 1:10 ratio (wt/wt). Py-GC-MS of biomass/catalyst mixture showed that the denitrogenation/deoxygenation increased with increasing zeolite load from 1:5 to 1:20 ratio and became significant at 1:10 ratio...
October 3, 2016: Bioresource Technology
Chengtao Wang, Liang Wang, Jian Zhang, Hong Wang, James P Lewis, Feng-Shou Xiao
No abstract text is available yet for this article.
October 7, 2016: Journal of the American Chemical Society
Alberto Sabbioni, Chiara Ferrario, Christian Milani, Leonardo Mancabelli, Enzo Riccardi, Francesco Di Ianni, Valentino Beretti, Paola Superchi, Maria C Ossiprandi
During last decades canine health and well being is becoming an important issue for human owners. In dogs, several factors including diet, pathogenic bacterial and stress conditions can affect the composition of the gut microbiota. In this study, we evaluated the effect of dietary chabazitic zeolitite (CZ) supplementation on the contribution of bifidobacteria to the fecal microbiota in training hunting dogs. Fecal microbiota cataloging based on 16S rRNA microbial profiling analyses highlighted an increase of Lactobacillus and Bifidobacterium in animals treated with CZ, with a simultaneous decrease of pathogens associated with dog gastrointestinal infections, such as Klebsiella and Enterobacter...
2016: Frontiers in Microbiology
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