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Lin Ye, Ivo Teixeira, Benedict T W Lo, Pu Zhao, S C Edman Tsang
By combining synchrotron X-ray powder diffraction, Rietveld refinement and the use of a probe molecule, Brønsted Acid Sites (BAS) of different strengths in steam-treated USY zeolite can be for the first time spatially differentiated: this enables the analysis of different acid-catalysed reactions of dimethylfuran (biomass) by the zeolite using a definitive site blockage strategy.
August 16, 2017: Chemical Communications: Chem Comm
Michael Fischer
Zeolites and structurally related materials (zeotypes) have received considerable attention as potential adsorbents for selective carbon dioxide adsorption. Within this group, zeotypes with aluminophosphate composition (AlPOs) could be an interesting alternative to the more frequently studied aluminosilicate zeolites. So far, however, only a few AlPOs have been characterised experimentally in terms of their CO2 adsorption properties. In this study, force-field based grand-canonical Monte Carlo (GCMC) simulations were used to evaluate the potential of AlPOs for CO2/N2 separation, a binary mixture that constitutes a suitable model system for the removal of carbon dioxide from flue gases...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
M Haris Mahyuddin, Yoshihito Shiota, Aleksandar Staykov, Kazunari Yoshizawa
While the most likely structure of the active site in iron-containing zeolites has been recently identified as [FeO](2+) (Snyder et al. Nature 2016, 536, 317-321), the mechanism for the direct conversion of methane to methanol over this active species is still debatable between the direct-radical-rebound or nonradical (concerted) mechanism. Using density functional theory on periodic systems, we calculated the two reaction mechanisms over two d(4) isoelectronic systems, [FeO](2+) and [MnO](+) zeolites. We found that [FeO](2+) zeolites favor the direct-radical-rebound mechanism with low CH4 activation energies, while [MnO](+) zeolites prefer the nonradical mechanism with higher CH4 activation energies...
August 15, 2017: Inorganic Chemistry
Joel E Schmidt, Frank C Hendriks, Martin Lutz, L Christiaan Post, Donglong Fu, Dr Bert M Weckhuysen
Large crystals of zeolite ferrierite (FER) are important model systems for spatially resolved catalysis and diffusion studies, though there is considerable variation in crystal habit depending on the chemical composition and employed synthesis conditions. A synergistic combination of techniques has been applied, including single crystal X-ray diffraction, high-temperature in situ confocal fluorescence microscopy, fluorescent probe molecules, wide-field microscopy and atomic force microscopy to unravel the internal architecture of three distinct FER zeolites...
August 15, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Hongmei Li, Xing Qian, Chong Xu, Shaowei Huang, Changli Zhu, Xiancai Jiang, Li Shao, Linxi Hou
The development of highly active and stable earth-abundant electrocatalysts to reduce or eliminate the reliance on noble-metal based ones for hydrogen evolution reaction (HER) over a broad pH range remains a great challenge. Herein, hierarchical porous Co9S8/N-doped carbon@MoS2 (Co9S8/NC@MoS2) polyhedrons have been synthesized by a facile hydrothermal approach using highly conductive Co/NC polyhedrons composed of cobalt nanoparticles embedded in N-doped carbon matrices as both the structural support and cobalt source...
August 14, 2017: ACS Applied Materials & Interfaces
Takumi Horiike, Yuma Dotsuta, Yuriko Nakano, Asumi Ochiai, Satoshi Utsunomiya, Toshihiko Ohnuki, Mitsuo Yamashita
Radioactive strontium ((90)Sr) leaked into saline environments, including the ocean, from the Fukushima Daiichi Nuclear Power Plant after a nuclear accident. Since the removal of (90)Sr using general adsorbents (e.g., zeolite) is not efficient at high salinity, a suitable alternative immobilization method is necessary. Therefore, we incorporated soluble Sr into biogenic carbonate minerals generated by urease-producing microorganisms from a saline solution. An isolate, Bacillus sp. strain TK2d, from marine sediment removed > 99% Sr after contact for four days in a saline solution (1...
August 11, 2017: Applied and Environmental Microbiology
Yaser Rasouli, Mohsen Abbasi, Seyed Abdollatif Hashemifard
In this research, four types of low cost and high performance ceramic microfiltration (MF) membranes have been employed in an in-line adsorption-MF process for oily wastewater treatment. Mullite, mullite-alumina, mullite-alumina-zeolite and mullite-zeolite membranes were fabricated as ceramic MF membranes by low cost kaolin clay, natural zeolite and α-alumina powder. Powdered activated carbon (PAC) and natural zeolite powder in concentrations of 100-800 mg L(-1) were used as adsorbent agent in the in-line adsorption-MF process...
August 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Shitu Yang, Chenxi Yu, Lili Yu, Shu Miao, Mingming Zou, Changzi Jin, Dazhi Zhang, Longya Xu, Shengjun Huang
Rational design of zeolite-based catalysts calls for flexible tailoring of porosity and acidity beyond micropore dimension. To date, dealumination has been applied extensively as an industrial technology for the tailoring of zeolite in micropore dimension, whereas desilication has separately shown its potentials in the creation of mesoporosities. The free coupling of dealumination with desilication will bridge the tailoring at micro/mesopore dimensions; however, such coupling has been prevailingly confirmed as an impossible mission...
August 11, 2017: Angewandte Chemie
Xitong Chen, Xianhui Bu, Qipu Lin, Chengyu Mao, Quan-Guo Zhai, Yuan Wang, Pingyun Feng
The development of novel photocatalysts usually centers on features such as band structures, various nano-, micro-, or macro-forms, and composites in efforts to tune their light absorption and charge separation efficiency. In comparison, the selectivity of photocatalysts with respect to features of reactants such as size and charge has received much less attention, in part due to the difficulty in designing semiconducting photocatalysts with uniform pore size. Here, we use crystalline porous chalcogenides as a platform to probe reactant selectivity in photocatalytic processes...
August 11, 2017: Chemistry: a European Journal
Christine Young, Rahul R Salunkhe, Jing Tang, Chi-Chang Hu, Mohammed Shahabuddin, Ekrem Yanmaz, Md Shahriar A Hossain, Jung Ho Kim, Yusuke Yamauchi
Correction for 'Zeolitic imidazolate framework (ZIF-8) derived nanoporous carbon: the effect of carbonization temperature on the supercapacitor performance in an aqueous electrolyte' by Christine Young et al., Phys. Chem. Chem. Phys., 2016, 18, 29308-29315.
August 10, 2017: Physical Chemistry Chemical Physics: PCCP
Anindita Chakraborty, Subhajit Laha, Kesavan Kamali, Chandrabhas Narayana, Muthusamy Eswaramoorthy, Tapas Kumar Maji
Self-assembly of metal-organic framework (MOF) nanoparticles (NPs) with a functional material can result in MOF nanocomposites having new and advanced properties along with the fabrication of new nanoscopic structures. However, such assembly of MOFs has not been realized to date. Here we report self-assembled nanocomposites of the zeolitic imidazolate framework (ZIF-8) and layered aminoclay (AC) for the first time, and the ZIF-8@AC composites exhibit significantly enhanced adsorption properties in comparison to those of pristine ZIF-8 nanoparticles...
August 9, 2017: Inorganic Chemistry
Boya Cui, Cornelius O Audu, Yijun Liao, SonBinh T Nguyen, Omar K Farha, Joseph T Hupp, Matthew Grayson
Thermal conductivity is a crucial parameter for managing exothermal gas adsorption in metal organic frameworks (MOFs), but experimental studies have been limited. In this work the thermal conductivity of a zeolitic imidazolate framework ZIF-8 was experimentally determined on thin films using the 3ω technique at different partial pressures in perfluorohexane, nitrogen, air, and vacuum ambients at 300 K. In contrast to theoretical prediction, the thermal conductivity κ = 0.326 ± 0.002 W/m·K was approximately independent of ambient gas species and pressure from atmospheric pressure to vacuum...
August 9, 2017: ACS Applied Materials & Interfaces
Paloma Vinaches, Katia Bernardo-Gusmão, Sibele B C Pergher
Zeolite synthesis is a wide area of study with increasing popularity. Several general reviews have already been published, but they did not summarize the study of imidazolium species in zeolite synthesis. Imidazolium derivatives are promising compounds in the search for new zeolites and can be used to help understand the structure-directing role. Nearly 50 different imidazolium cations have already been used, resulting in a variety of zeolitic types, but there are still many derivatives to be studied. In this context, the purpose of this short review is to help researchers starting in this area by summarizing the most important concepts related to imidazolium-based zeolite studies and by presenting a table of recent imidazolium derivatives that have been recently studied to facilitate filling in the knowledge gaps...
August 6, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Helen Paola Toledo-Jaldin, Alien Blanco-Flores, Víctor Sánchez-Mendieta, Osnieski Martín-Hernández
Removal potentials of a surfactant modified zeolite (SMZ) and clay (SMC) for atrazine adsorption were evaluated. Materials were modified with hexadecyl trimethyl ammonium bromide (HDTMA) and benzyl octadecyl dimethyl ammonium chloride (BODA) considering the critical miscelar concentration (CMC) of each one (0.94 and 0.041 meq/L, respectively). The influence of the surfactant was analyzed in detail, particularly the formation of surfactant layers (complete or partial) connected with the length of the surfactant tail (16 and 18 methyl groups or number of carbons in the chain)...
August 7, 2017: Environmental Technology
Dries Jonckheere, Julian A Steele, Birgit Claes, Bart Bueken, Laurens Claes, Bert Lagrain, Maarten B J Roeffaers, Dirk E De Vos
Metal-organic frameworks (MOFs) are investigated for the adsorption of aromatic amino acids L-phenylalanine (L-Phe), L-tryptophan (L-Trp) and L-tyrosine (L-Tyr) from aqueous solutions. After screening a range of water-stable MOFs, the hydrophobic Zr-MOF MIL-140C emerged as the most performant material, exhibiting uptakes of 15 wt% for L-Trp and 20 wt% for L-Phe. These uptakes are 5 to 10 wt% higher than those of large-pore zeolites Beta and Y. Both single-compound and competitive adsorption isotherms for L-Phe and L-Trp were experimentally obtained at the natural pH of these amino acid mixtures without additional pH-modification (pH 6...
August 7, 2017: ACS Applied Materials & Interfaces
Triantafyllos Tatoulis, Christos S Akratos, Athanasia G Tekerlekopoulou, Dimitrios V Vayenas, Alexandros I Stefanakis
The use of Constructed Wetlands (CWs) has been nowadays expanded from municipal to industrial and agro-industrial wastewaters. The main limitations of CWs remain the relatively high area requirements compared to mechanical treatment technologies and the potential occurrence of the clogging phenomenon. This study presents the findings of an innovative CW design where novel materials were used. Four pilot-scale CW units were designed, built and operated for two years. Each unit consisted of two compartments, the first of which (two thirds of the total unit length) contained either fine gravel (in two units) or random type high density polyethylene (HDPE) (in the other two units)...
August 1, 2017: Chemosphere
Nadali Alavi, Monavvar Daneshpajou, Mohammad Shirmardi, Gholamreza Goudarzi, Abdolkazem Neisi, Ali Akbar Babaei
Fermentation of ethanol as a product of sugarcane agro-industry causes the discharge of large amounts of a liquid waste called vinasse into the environment. In this study, co-composting followed by vermicomposting process of the mixtures of vinasse, cow manure, and chopped bagasse was performed for 60days using earthworms of Eisenia fetida species. The results showed that the trend of changes in C/N was decreasing. The pH of the final fertilizer was in alkaline range (8.1-8.4). The total potassium decreased during the process, ranging from 0...
August 2, 2017: Waste Management
Xianjiang Shen, Guibo Qiu, Changsheng Yue, Min Guo, Mei Zhang
Copper ions were first adsorbed by zeolite 4A synthesized from bauxite tailings, the desorption of Cu(II) using Na2EDTA solutions was performed, and the recycling of zeolite 4A in adsorption and desorption was systematically investigated. It was observed that the Cu(II) removal efficiency was directly dependent on the initial pH value. The maximum removal efficiency of Cu(II) was 96.2% with zeolite 4A when the initial pH value was 5.0. Cu(II) was completely absorbed in the first 30 min. It was also observed that the desorption efficiency and zeolite recovery were highly dependent on the initial pH and concentration of Na2EDTA in the solution...
August 3, 2017: Environmental Science and Pollution Research International
Małgorzata Franus, Grzegorz Jozefaciuk, Lidia Bandura, Krzysztof Lamorski, Mieczysław Hajnos, Wojciech Franus
An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %-8 wt %) caused marked changes in the aggregates' microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%-2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates' bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase...
October 18, 2016: Materials
Jingbin Yang, Dongxu Li, Yuan Fang
C-A-S-H (CaO-Al₂O₃-SiO₂-H₂O) and N-A-S-H (Na₂O-Al₂O₃-SiO₂-H₂O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na₂O)/SiO₂ ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis...
June 26, 2017: Materials
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