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Showing records 1 to 25 of 230. [First] Page: 1 2 3 4 5 Last
Effect of Physical and Mechanical Activation on the Physicochemical Structure of Coal-Based Activated Carbons for SO2 Adsorption
Dongdong Liu, Zhengkai Hao, Xiaoman Zhao, Rui Su, Weizhi Feng, Song Li, Boyin Jia
December 9, 2019 (v1)
Subject: Materials
Keywords: activated carbons, mechanical activation, physical activation, physicochemical structure, SO2 adsorption
The SO2 adsorption efficiency of activated carbons (ACs) is clearly dependent on its physicochemical structure. Related to this, the effect of physical and mechanical activation on the physicochemical structure of coal-based ACs has been investigated in this work. In the stage of CO2 activation, the rapid decrease of the defective structure and the growth of aromatic layers accompanied by the dehydrogenation of aromatic rings result in the ordered conversion of the microstructure and severe carbon losses on the surfaces of Char-PA, while the oxygen content of Char-PA, including C=O (39.6%), C−O (27.3%), O−C=O (18.4%) and chemisorbed O (or H2O) (14.7%), is increased to 4.03%. Char-PA presents a relatively low SBET value (414.78 m2/g) owing to the high value of Non-Vmic (58.33%). In the subsequent mechanical activation from 12 to 48 h under N2 and dry ice, the strong mechanical collision caused by ball-milling can destroy the closely arranged crystalline layers and the collapse of mesopo... [more]
Molecular Insights into Cage Occupancy of Hydrogen Hydrate: A Computational Study
Rui Ma, Hong Zhong, Jinxiang Liu, Jie Zhong, Youguo Yan, Jun Zhang, Jiafang Xu
December 9, 2019 (v1)
Subject: Materials
Keywords: density functional theory, hydrogen hydrate, molecular dynamics simulation, stability
Density functional theory calculations and molecular dynamics simulations were performed to investigate the hydrogen storage capacity in the sII hydrate. Calculation results show that the optimum hydrogen storage capacity is ~5.6 wt%, with the double occupancy in the small cage and quintuple occupancy in the large cage. Molecular dynamics simulations indicate that these multiple occupied hydrogen hydrates can occur at mild conditions, and their stability will be further enhanced by increasing the pressure or decreasing the temperature. Our work highlights that the hydrate is a promising material for storing hydrogen.
Study on the Compatibility of Gas Adsorbents Used in a New Insulating Gas Mixture C4F7N/CO2
Qingdan Huang, Yong Wang, Jing Liu, Yaru Zhang, Lian Zeng
December 9, 2019 (v1)
Subject: Materials
Keywords: adsorbents, desiccants, HF removal, insulating gas, perfluoroisobutyronitrile
An environment-friendly insulating gas, perfluoroisobutyronitrile (C4F7N), has been developed recent years. Due to its relatively high liquefaction temperature (around −4.7 °C), buffer gases, such as CO2 and N2, are usually mixed with C4F7N to increase the pressure of the filled insulating medium. During these processes, the insulating gases may be contaminated with micro-water, and the mixture of H2O with C4F7N could produce HF under breakdown voltage condition, which is harmful to the gas insulated electricity transfer equipment. Therefore, removal of H2O and HF in situ from the gas insulated electricity transfer equipment is significant to its operation security. The adsorbents with the ability to remove H2O but without obvious C4F7N/CO2 adsorption capacity are essential to be used in this system. In this work, a series of industrial adsorbents and desiccants were tested for their compatibility with C4F7N/CO2. Pulse adsorption tests were conducted to evaluate the adsorption performa... [more]
Preparation and Molecular Dynamics Simulation of RDX/MUF Nanocomposite Energetic Microspheres with Reduced Sensitivity
Xinlei Jia, Yingying Hu, Lanjuan Xu, Xuewen Liu, Youying Ma, Mingming Fu, Jingyu Wang, Jing Xu
December 9, 2019 (v1)
Subject: Materials
Keywords: improved emulsion polymerization, MD simulation, nanocomposite energetic microspheres, RDX/MUF
In order to improve the general problem of irregular coating morphology and low mechanical strength of the coating layer in existing coating desensitization technology, nano-cyclotrimethylene trinitramine/melamine-urea-formaldehyde (RDX/MUF) composite energetic microspheres were prepared by an improved emulsion polymerization, taking the MUF as the binder and RDX as the main explosive. In order to judge whether RDX/MUF possessed good stability, the combination of differential scanning calorimetry (DSC) and molecular dynamics (MD) simulation was used to determine the level of binding binding energy between urea-formaldehyde resin binder (UF) and RDX. In addition, to investigate the optimal reaction temperature for the preparation of MUF/RDX, the binding energy between UF and RDX at different temperatures was simulated. And then the morphology and thermal properties of the as-prepared composite energetic microspheres were analyzed by scanning electron microscopy (SEM) and DSC, the impact... [more]
Computational Analysis of Imbalance-Based Irregularity Indices of Boron Nanotubes
Bin Yang, Mobeen Munir, Shazia Rafique, Haseeb Ahmad, Jia-Bao Liu
December 9, 2019 (v1)
Subject: Materials
Keywords: alpha boron tube, boron nanotube, complexity of structure, irregularity measure, tri-hexagonal boron nanotube, triangular boron tube
Molecular topology provides a basis for the correlation of physical as well as chemical properties of a certain molecule. Irregularity indices are used as functions in the statistical analysis of the topological properties of certain molecular graphs and complex networks, and hence help us to correlate properties like enthalpy, heats of vaporization, and boiling points etc. with the molecular structure. In this article we are interested in formulating closed forms of imbalance-based irregularity measures of boron nanotubes. These tubes are known as α-boron nanotube, triangular boron nanotubes, and tri-hexagonal boron nanotubes. We also compare our results graphically and come up with the conclusion that alpha boron tubes are the most irregular with respect to most of the irregularity indices.
Comparison of Irregularity Indices of Several Dendrimers Structures
Dongming Zhao, Zahid Iqbal, Rida Irfan, Muhammad Anwar Chaudhry, Muhammad Ishaq, Muhammad Kamran Jamil, Asfand Fahad
December 3, 2019 (v1)
Subject: Materials
Keywords: dendrimers, irregularity indices, molecular graph
Irregularity indices are usually used for quantitative characterization of the topological structures of non-regular graphs. In numerous problems and applications, especially in the fields of chemistry and material engineering, it is useful to be aware of the irregularity of a molecular structure. Furthermore, the evaluation of the irregularity of graphs is valuable not only for quantitative structure-property relationship (QSPR) and quantitative structure-activity relationship (QSAR) studies but also for various physical and chemical properties, including entropy, enthalpy of vaporization, melting and boiling points, resistance, and toxicity. In this paper, we will restrict our attention to the computation and comparison of the irregularity measures of different classes of dendrimers. The four irregularity indices which we are going to investigate are σ irregularity index, the irregularity index by Albertson, the variance of vertex degrees, and the total irregularity index.
Rice Husk Biochars Modified with Magnetized Iron Oxides and Nano Zero Valent Iron for Decolorization of Dyeing Wastewater
Bao-Son Trinh, Phung T. K. Le, David Werner, Nguyen H. Phuong, Tran Le Luu
December 3, 2019 (v1)
Subject: Materials
Keywords: biochar, full-scale gasification, nano zero-valent iron, pyrolysis, rice husk
This study investigated if biochar, a low-cost carbon-rich material, can be modified with reactive materials for decolorization of dyeing wastewater. Two types of rice husk biochars were produced by using different processes of gasification and pyrolysis in limited air condition. The biochars were first magnetized and then modified with nano-scale zero-valent iron (nZVI) to achieve the final products of magnetic-nZVI biochars. Batch experiments were conducted to investigate the efficiency of the modified biochars for reducing color of the reactive dyes yellow (RY145), red (RR195), and blue (RB19) from dyeing solutions. Results showed that color removal efficiency of the modified biochars was significantly enhanced, achieving the values of 100% for RY145 and RR195 and ≥65% for RB19, while the effectiveness of the original biochar was significantly lower. In addition, with increasing dose of the modified biochars, the color removal efficiency increased accordingly. In contrast, when the... [more]
Characterizing the Suitability of Granular Fe0 for the Water Treatment Industry
Rui Hu, Xuesong Cui, Minhui Xiao, Pengxiang Qiu, Mesia Lufingo, Willis Gwenzi, Chicgoua Noubactep
December 3, 2019 (v1)
Subject: Materials
Keywords: 1,10-phenanthroline, ethylenediaminetetraacetic acid, intrinsic reactivity, material selection, quality control, zero-valent iron
There is a burgeoning interest in reliably characterizing the intrinsic reactivity of metallic iron materials (Fe0) or zero-valent iron materials (ZVI) used in the water treatment industry. The present work is a contribution to a science-based selection of Fe0 for water treatment. A total of eight (8) granular ZVI materials (ZVI1 to ZVI8) were tested. Fe0 dissolution in ethylenediaminetetraacetic acid (EDTA test) and 1,10-Phenanthroline (Phen test) is characterized in parallel experiments for up to 250 h (10 days). 50 mL of each solution and 0.1 g of each Fe0 material are equilibrated in quiescent batch experiments using 2 mM EDTA or Phen. Results indicated a far higher extent of iron dissolution in EDTA than in Phen under the experimental conditions. The tested materials could be grouped into three reactivity classes: (i) low (ZVI4, ZVI6, ZVI7, and ZVI8), (ii) moderate (ZVI1 and ZVI5) and (iii) high (ZVI2 and ZVI3). The order of reactivity was the same for both tests: ZVI2 ≅ ZVI3 > ZV... [more]
Effect of Cellulosic Waste Derived Filler on the Biodegradation and Thermal Properties of HDPE and PLA Composites
Alessia Quitadamo, Valerie Massardier, Valeria Iovine, Ahmed Belhadj, Rémy Bayard, Marco Valente
December 3, 2019 (v1)
Subject: Materials
Keywords: bio-derived polymer, biodegradation, composites
Composites with high density polyethylene (HDPE) and poly(lactic) acid (PLA) matrix have been tested to analyze the effect of natural fillers (wood flour, recycled wastepaper and a mix of both fillers) and temperature on polymer degradation. Composting tests have been performed in both mesophilic (35 °C) and thermophilic (58 °C) conditions. Degradation development has been evaluated through mass variation, thermogravimetric analysis and differential scanning calorimetry. HDPE, as expected, did not display any relevant variation, confirming its stability under our composting conditions. PLA is sensibly influenced by temperature and humidity, with higher reduction of Mw when composting is performed at 58 °C. Natural fillers seem to influence degradation process of composites, already at 35 °C. In fact, degradation of fillers at 35 °C allows a mass reduction during composting of composites, while neat PLA do not display any variation.
Leaching of Organic Toxic Compounds from PVC Water Pipes in Medina Al-Munawarah, Kingdom of Saudi Arabia
Muhammad Mansoor Shaikh, Marlia Mohd Hanafiah, Alfarooq O. Basheer
December 3, 2019 (v1)
Subject: Materials
Keywords: drinking water, polyvinylchloride (PVC), solid phase extraction (SPE), volatile compounds
It is well established that the use of synthetic material in water pipes significantly affects the quality of domestic water, especially trace organics that are leached through with the flow of water. In the present study, the migration of volatile organic compounds (VOCs) from water pipes manufactured of polyvinyl chloride (PVC) has been investigated using static laboratory conditions and in residential areas. The contact of deionized water with various PVC pipes for three successive test periods of 24, 48, and 72 h duration has been made. Twenty water samples were collected from houses within Medina Al-Munawarah residential area and were analyzed by using solid phase extraction, followed by high resolution gas chromatography with flame ionized detector (GC-FID). The presence of carbon tetrachloride (CTC), toluene, chloroform, styrene, o-xylene, bromoform (BF), dibromomethane (DBM), cis-1,3-dichloropropane (Cis-1,3-DCP), and trans-1,3-dichloropropane (Trans-1,3-DCP) was initially conf... [more]
Lattice Strain Analysis of a Mn-Doped CdSe QD System Using Crystallography Techniques
Nor Aliya Hamizi, Mohd Rafie Johan, Nadiah Ghazali, Yasmin Abdul Wahab, Zaira Zaman Chowdhury, Omid Akbarzadeh, Suresh Sagadevan, Irfan Anjum Badruddin, T. M. Yunus Khan, Sarfaraz Kamangar
December 3, 2019 (v1)
Subject: Materials
Keywords: cadmium selenide, chemical synthesis, lattice strain, quantum dots
In this work, we report on the different sizes of manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs) synthesized for 0 to 90 min using a reverse micelle organic solvent method and surfactant having a zinc blende structure, with physical size varying from 3 to 14 nm and crystallite size from 2.46 to 5.46 nm and with a narrow size distribution. At similar reaction times, Mn-doped CdSe QDs displayed the growth of larger QDs compared with the pure CdSe QDs. Due to the implementation of lattice strain owing to the inclusion of Mn atoms in the CdSe QD lattice, the lattice parameter was compressed as the QD size increased. Strain was induced by the particle size reduction, as observed from X-ray diffractometer (XRD) analysis. The analyses of the strain effect on the QD reduction are discussed relative to each of the XRD characteristics.
CVD Synthesis, Functionalization and CO2 Adsorption Attributes of Multiwalled Carbon Nanotubes
Shazia Shukrullah, Muhammad Yasin Naz, Norani M. Mohamed, Khalid A. Ibrahim, Nasser M. AbdEl-Salam, Abdul Ghaffar
November 24, 2019 (v1)
Subject: Materials
Keywords: CO2 adsorption capacity, fluidized bed CVD, functionalized CNTs, MWCNTs
Carbon dioxide is one of the major greenhouse gases and a leading source of global warming. Several adsorbent materials are being tested for removal of carbon dioxide (CO2) from the atmosphere. The use of multiwalled carbon nanotubes (MWCNTs) as a CO2 adsorbent material is a relatively new research avenue. In this study, Fe2O3/Al2O3 composite catalyst was used to synthesize MWCNTs by cracking ethylene gas molecules in a fluidized bed chemical vapor deposition (CVD) chamber. These nanotubes were treated with H2SO4/HNO3 solution and functionalized with 3-aminopropyl-triethoxysilane (APTS). Chemical modification of nanotubes removed the endcaps and introduced some functional groups along the sidewalls at defected sites. The functionalization of nanotubes with amine introduced carboxylic groups on the tube surface. These functional groups significantly enhance the surface wettability, hydrophilicity and CO2 adsorption capacity of MWCNTs. The CO2 adsorption capacity of as-grown and amine-fu... [more]
Water Treatment Using Metallic Iron: A Tutorial Review
Rui Hu, Willis Gwenzi, Viviane Raïssa Sipowo-Tala, Chicgoua Noubactep
November 24, 2019 (v1)
Subject: Materials
Keywords: iron corrosion products, laboratory experiments, pilot tests, removal mechanisms, water treatment, zero-valent iron
Researchers and engineers using metallic iron (Fe0) for water treatment need a tutorial review on the operating mode of the Fe0/H2O system. There are few review articles attempting to present systematic information to guide proper material selection and application conditions. However, they are full of conflicting reports. This review seeks to: (i) Summarize the state-of-the-art knowledge on the remediation Fe0/H2O system, (ii) discuss relevant contaminant removal mechanisms, and (iii) provide solutions for practical engineering application of Fe0-based systems for water treatment. Specifically, the following aspects are summarized and discussed in detail: (i) Fe0 intrinsic reactivity and material selection, (ii) main abiotic contaminant removal mechanisms, and (iii) relevance of biological and bio-chemical processes in the Fe0/H2O system. In addition, challenges for the design of the next generation Fe0/H2O systems are discussed. This paper serves as a handout to enable better practic... [more]
The Removal of Silicate(IV) by Adsorption onto Hydrocalumite from the Sodium Hydroxide Leaching Solution of Black Dross
Thi Thuy Nhi Nguyen, Man Seung Lee
November 24, 2019 (v1)
Subject: Materials
Keywords: Adsorption, alumina, black dross, hydrocalumite, silicate
Alkaline leaching of mechanically activated black dross resulted in an aluminate(III) solution with a small amount of silicate(IV). To obtain pure aluminate(III) solution, the removal of silicate(IV) from the alkaline leaching solution was investigated by adsorption with hydrocalumite (Ca2Al(OH)6Cl·2H2O). The hydrocalumite was synthesized by the coprecipitation method. The characterization of the synthesized hydrocalumite was analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM) images and Fourier-transform infrared spectroscopy (FTIR). In our experimental conditions, silicate(IV) was selectively adsorbed onto hydrocalumite over aluminate(III). The reaction time greatly affected the removal percentage of aluminate(III) owing to mass action effect. When the reaction time was longer than 2 h, no aluminate(III) was adsorbed onto hydrocalumite and thus it was possible to selectively remove silicate(IV). When the dosage of hydrocalumite was in excess, the removal percenta... [more]
Study of the Lamellar and Micellar Phases of Pluronic F127: A Molecular Dynamics Approach
Juan M. R. Albano, Damian Grillo, Julio C. Facelli, Marta B. Ferraro, Mónica Pickholz
November 24, 2019 (v1)
Subject: Materials
Keywords: lamellar, micellar, molecular dynamics, Pluronic F127, poloxamer
In this work, we analyzed the behavior of Pluronic F127 through molecular dynamics simulations at the coarse-grain level, focusing on the micellar and lamellar phases. To this aim, two initial polymer conformations were considered, S-shape and U-shape, for both simulated phases. Through the simulations, we were able to examine the structural and mechanical properties that are difficult to access through experiments. Since no transition between S and U shapes was observed in our simulations, we inferred that all single co-polymers had memory of their initial configuration. Nevertheless, most copolymers had a more complex amorphous structure, where hydrophilic beads were part of the lamellar-like core. Finally, an overall comparison of the micellar a lamellar phases showed that the lamellar thickness was in the same order of magnitude as the micelle diameter (approx. 30 nm). Therefore, high micelle concentration could lead to lamellar formation. With this new information, we could unders... [more]
Adsorption of Arsenic and Lead onto Stone Powder and Chitosan-Coated Stone Powder
Kyungho Jung, Sanghwa Oh, Hun Bak, Gun-Ho Song, Hong-Tae Kim
November 24, 2019 (v1)
Subject: Materials
Keywords: Adsorption, arsenic, chitosan-coated stone powder, lead, stone powder
Stone powder (SP) produced from masonry mills has been treated as a specific waste and rarely used for environmental purposes. In this study, we tested its potential as an adsorbent to remove arsenic (As) and lead (Pb) from water. The single-solute sorption isotherms for As(V) and Pb(II) onto SP and chitosan-coated SP (CSP) were investigated. Several sorption models, such as the Langmuir, Freundlich, and Dubinin−Radushkevich (DR) models, were used to analyze the adsorption features. The results demonstrated that As and Pb were successfully adsorbed onto SP and CSP, indicating that SP and CSP had potential as adsorbents of As and Pb. The maximum adsorption capacities of SP and CSP for Pb were 22.8 and 54.5 times higher than those for As, respectively. Chitosan coating increased the adsorption potential in Pb adsorption by 5% but decreased it in As adsorption. The adsorption potential also depended on the pH and temperature. The adsorption amount of As increased with pH but that of Pb de... [more]
Highly Selective CO2 Capture on Waste Polyurethane Foam-Based Activated Carbon
Chao Ge, Dandan Lian, Shaopeng Cui, Jie Gao, Jianjun Lu
November 24, 2019 (v1)
Subject: Materials
Keywords: Carbon Dioxide Capture, high selectivity, physical activation, ultra-micropore, waste polyurethane foam
Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO2 for the first time and chemical activation with Ca(OH)2, NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO2 adsorption capacity and CO2/N2 selectivity. The sample prepared by physical activation showed CO2/N2 selectivity of up to 24, much higher than that of chemical activation. This is mainly due to the narrower microporosity and the rich N content produced during the physical activation process. However, physical activation samples showed inferior textural properties compared to chemical activation samples and led to a lower CO2 uptake of 3.37 mmol·g−1 at 273 K. Porous carbons obtained by chemical activation showed a high CO2 uptake of 5.85 mmol·g−1 at 273 K, comparable to the optimum activated carbon materials prepared from other wastes. This is mainly attributed to large volumes of ultra-micropores (<1 nm) up to 0.212 cm3·g−1 and... [more]
Characterization of Natural Composites Fabricated from Abutilon-Fiber-Reinforced Poly (Lactic Acid)
Hua Wang, Elwathig. A. M. Hassan, Hafeezullah Memon, Tienah. H. H. Elagib, Fadlelmoula Abad AllaIdris
November 24, 2019 (v1)
Subject: Materials
Keywords: abutilon, characterization, green composite, poly (lactic acid) and reinforcement
In recent decades, natural-fiber-reinforced poly (lactic acid) (PLA) composites have received a great deal of attention. In this study, biocomposites of poly (lactic acid) and abutilon fibers are prepared by using melt blending and an extruder. The effects of fiber additions on rheological, thermomechanical, thermal, and morphological properties are investigated using a rheometer, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC), TGA, and SEM, respectively. The DSC results indicate that the fibers acted as a nucleating agent, which led to enhancing the crystallization of PLA. The results also reveal that the thermal stability of PLA was improved by abutilon fibers. Moreover, higher values of storage modulus are observed, which are attributed to strong interfacial adhesion. In addition, thetan delta isreduced upon the addition of fiber content into the PLA matrix, which restricts the mobility of PLA polymer molecules in the presence of the fibers. The improveme... [more]
Impact Analysis of Water Quality on the Development of Construction Materials
Hamad Farid, Muhammad Shoaib Mansoor, Syyed Adnan Raheel Shah, Nasir Mahmood Khan, Rana Muhammad Farooq Shabbir, Muhammad Adnan, Hunain Arshad, Inzmam-Ul Haq, Muhammad Waseem
November 24, 2019 (v1)
Subject: Materials
Keywords: materials, strength, Wastewater, water management, water quality
This research dealt with the impact of the quality of the water source on the mechanical properties of construction materials. The mechanical properties of construction materials include compressive, tensile, and flexural strength. Water samples were collected from different resources, these samples were then synthetically investigated to identify and compare their quality parameters. After a detailed chemical analysis of water samples from three sources—wastewater, surface or canal water, and ground water—construction concrete material samples were prepared. The construction materials were developed with the same water−cement ratio, i.e., 0.60 for each concrete mix sample at two mix ratios—M1 (1:2:4) and M2 (1:1.5:3). Slump cone and compacting factor tests were conducted on the fresh concrete to determine its workability prior to its hardening. Then, at 7, 14, 21, and 28 days for each mix, tests for mechanical properties were carried out to determine the compressive, tensile, and flex... [more]
Comparison of Growth Characteristics and Properties of CVD TiN and TiO2 Anti-Coking Coatings
Shiyun Tang, Tao Liu, Shuiping Duan, Junjiang Guo, Anjiang Tang
November 24, 2019 (v1)
Subject: Materials
Keywords: anti-coking coating, coke, growth characteristics, hydrocarbon fuel
Coating metals with anti-coking materials inhibit their catalytic coking and are especially beneficial in the pyrolysis of hydrocarbon fuels. It is believed that growth characteristics and properties may play a pivotal role in the anti-coking performance of chemical vapor deposition (CVD) coatings. In this study, TiN and TiO2 coatings were obtained by CVD using TiCl4−N2−H2 and TiCl4−H2−CO2 systems, respectively. The effects of deposition time, residence time, and partial pressure were examined, and the coating microstructure was characterized by scanning electron microscopy (SEM). The results reveal that the effect of deposition parameters on the growth characteristics of TiN and TiO2 coatings is very different. The growth of the TiN coating shows characteristics of the island growth model, while the TiO2 coating follows the layer model. In general, the growth rate of the star-shaped TiN crystals is higher than that of crystals of other shapes. For the TiO2 coating, the layer mode grow... [more]
Adsorption Process and Properties Analyses of a Pure Magadiite and a Modified Magadiite on Rhodamine-B from an Aqueous Solution
Mingliang Ge, Zhuangzhuang Xi, Caiping Zhu, Guodong Liang, Yinye Yang, Guoqing Hu, Lafifa Jamal, Jahangir Alam S.M.
November 24, 2019 (v1)
Subject: Materials
Keywords: adsorption process, CTAB-Magadiite, magadiite, rhodamine-B
The result of an adsorption experiment indicated that the pure magadiite (MAG) and the modified MAG via cetyltrimethylammonium-bromide (CTAB-MAG) possessed pronounced affinity to the Rhodamine-B (Rh-B) dye molecules. CTAB-MAG was synthesized with an ion-exchange method between MAG and cetyltrimethylammonium-bromide (CTAB) in an aqueous solution. The adsorption capacities of CTAB-MAG and MAG on Rh-B were 67.19 mg/g and 48.13 mg/g, respectively; while the pH and the time were 7 and 60 min, respectively; however, the initial concentration of Rh-B was 100 mg/L, and adsorbent dosage was 1 g/L. Whereas, the adsorption capacity of CTAB-MAG was increased by 40% over MAG which indicated that CTAB-MAG can be used as an efficient low-cost adsorbent. Adsorption kinetics were consistent with the pseudo-second-order kinetic equation; the adsorption processes were dominated by film diffusion process which belonged to monomolecular layer adsorption.
On the Selective Transport of Nutrients through Polymer Inclusion Membranes Based on Ionic Liquids
Z. Baicha, M.J. Salar-García, V.M. Ortiz-Martínez, F.J. Hernández-Fernández, A.P. de los Ríos, D.P. Maqueda Marín, J.A. Collado, F. Tomás-Alonso, M. El Mahi
November 5, 2019 (v1)
Subject: Materials
Keywords: ionic liquids, liquid membrane stability, nutrients, permeation, polymer inclusion membranes
In the last few years, the use of ionic liquid-based membranes has gained importance in a wide variety of separation processes due to the unique properties of ionic liquids. The aim of this work is to analyze the transport of nutrients through polymer inclusion membranes based on different concentrations of methyltrioctylammonium chloride, in order to broaden the application range of these kinds of membranes. Calcium chloride (CaCl2) and sodium hydrogen phosphate (Na2HPO4) nutrients were used at the concentration of 1 g·L−1 in the feeding phase. The evolution of the concentration in the receiving phase over time (168 h) was monitored and the experimental data fitted to a diffusion-solution transport model. The results show very low permeation values for CaCl2. By contrast, in the case of Na2HPO4 the permeation values were higher and increase as the amount of ionic liquid in the membrane also increases. The surface of the membranes was characterized before and after being used in the se... [more]
Adsorption of NO Gas Molecules on Monolayer Arsenene Doped with Al, B, S and Si: A First-Principles Study
Keliang Wang, Jing Li, Yu Huang, Minglei Lian, Dingmei Chen
November 5, 2019 (v1)
Subject: Materials
Keywords: arsenene, doping, first principles study, gas adsorption, two-dimensional
The structures and electronic properties of monolayer arsenene doped with Al, B, S and Si have been investigated based on first-principles calculation. The dopants have great influences on the properties of the monolayer arsenene. The electronic properties of the substrate are effectively tuned by substitutional doping. After doping, NO adsorbed on four kinds of substrates were investigated. The results demonstrate that NO exhibits a chemisorption character on Al-, B- and Si-doped arsenene while a physisorption character on S-doped arsenene with moderate adsorption energy. Due to the adsorption of NO, the band structures of the four systems have great changes. It reduces the energy gap of Al- and B-doped arsenene and opens the energy gap of S- and Si-doped arsenene. The large charge depletion between the NO molecule and the dopant demonstrates that there is a strong hybridization of orbitals at the surface of the doped substrate because of the formation of a covalent bond, except for S... [more]
Recovering Cobalt and Sulfur in Low Grade Cobalt-Bearing V−Ti Magnetite Tailings Using Flotation Process
Junhui Xiao, Yushu Zhang
November 5, 2019 (v1)
Subject: Materials
Keywords: cobalt, cobalt pyrite, flotation, linneite, pyrite, V–Ti magnetite tailings
There is 0.032% cobalt and 0.56% sulfur in the cobalt-bearing V−Ti tailings in the Panxi Region, with the metal sulfide minerals mainly including FeS2, Fe1−xS, Co3S4, and (Fe,Co)S2, and the gangue minerals mainly including aluminosilicate minerals. The flotation process was used to recover cobalt and sulfur in the cobalt-bearing V−Ti tailings. The results showed that an optimized cobalt−sulfur concentrate with a cobalt grade of 2.08%, sulfur content of 36.12%, sulfur recovery of 85.79%, and cobalt recovery and 84.77% were obtained by flotation process of one roughing, three sweeping, and three cleaning under roughing conditions, which employed pulp pH of 8, grinding fineness of <0.074 mm occupying 80%, flotation concentration of 30%, and dosages of butyl xanthate, copper sulfate, and pine oil of 100 g/t, 30 g/t, and 20 g/t, respectively. Optimized one sweeping, two sweeping, and three sweeping conditions used a pulp pH of 9, and dosages of butyl xanthate, copper sulfate, and pine oi... [more]
Imbalance-Based Irregularity Molecular Descriptors of Nanostar Dendrimers
Zafar Hussain, Mobeen Munir, Shazia Rafique, Tayyab Hussnain, Haseeb Ahmad, Young Chel Kwun, Shin Min Kang
October 26, 2019 (v1)
Subject: Materials
Keywords: complexity of structure, irregularity measure, nanostar dendrimer, NS1[p], NS2[p], NS3[p]
Dendrimers are branched organic macromolecules with successive layers of branch units surrounding a central core. The molecular topology and the irregularity of their structure plays a central role in determining structural properties like enthalpy and entropy. Irregularity indices which are based on the imbalance of edges are determined for the molecular graphs associated with some general classes of dendrimers. We also provide graphical analysis of these indices for the above said classes of dendrimers.
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