Select
Where physics meets chemistry: Thin film deposition from reactive plasmas
Andrew Michelmore, Jason D. Whittle, James W. Bradley, Robert D. Short
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 441-458.
https://doi.org/10.1007/s11705-016-1598-7
Functionalising surfaces using polymeric thin films is an industrially important field. One technique for achieving nanoscale, controlled surface functionalization is plasma deposition. Plasma deposition has advantages over other surface engineering processes, including that it is solvent free, substrate and geometry independent, and the surface properties of the film can be designed by judicious choice of precursor and plasma conditions. Despite the utility of this method, the mechanisms of plasma polymer growth are generally unknown, and are usually described by chemical (i.e., radical) pathways. In this review, we aim to show that plasma physics drives the chemistry of the plasma phase, and surface-plasma interactions. For example, we show that ionic species can react in the plasma to form larger ions, and also arrive at surfaces with energies greater than 1000 kJ?mol– 1 (>10 eV) and thus facilitate surface reactions that have not been taken into account previously. Thus, improving thin film deposition processes requires an understanding of both physical and chemical processes in plasma.
Figures and Tables |
References |
Related Articles |
Metrics
Select
Combustion mechanism development and CFD simulation for the prediction of soot emission during flaring
Anan Wang,Helen H. Lou,Daniel Chen,Anfeng Yu,Wenyi Dang,Xianchang Li,Christopher Martin,Vijaya Damodara,Ajit Patki
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 459-471.
https://doi.org/10.1007/s11705-016-1594-y
Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data.
Figures and Tables |
References |
Related Articles |
Metrics
Select
On the fouling mechanism of polysulfone ultrafiltration membrane in the treatment of coal gasification wastewater
Xue Zou,Jin Li
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 490-498.
https://doi.org/10.1007/s11705-016-1600-4
Membrane fouling has been investigated by using a polysulfone ultrafiltration membrane with the molecular weight cutoff of 20 kDa to treat crushed coal pressurized gasification wastewater. Under the conditions of different feed pressures, the permeate flux declines and rejection coefficients of pollutants referring to three parameters (total organic carbon (TOC), chroma and turbidity) were studied. The membrane fouling mechanism was simulated with three classical membrane fouling models. The membrane image and pollutants were analyzed by scanning electron microscopy and gas chromatography-mass spectrography (GC-MS). The results indicate that the permeate flux decreases with volume reduction factor before reaching a constant value. The rejection coefficients were also measured: f TOC = 70.5%, f C = 84.9% and f T = 91%. Further analysis shows that the higher the feed pressure is, the sooner the permeate flux reaches constant value and the more sharply the permeate flux declines. Constant flux indicates a nonlinear growth with feed pressure (P F ): when P F equals 1.2 bar, the mark for the critical flux, slight membrane fouling occurs; when P F exceeds 1.2 bar, cake layer pollution aggravates. Also the rejection coefficients of global pollutant increases slightly with P F , suggesting the possibility of cake compression when P F exceeds 1.2 bar. Through regression analysis, the fouling of polysulfone ultrafiltration membrane could be fitted very well by cake filtration model. The membrane pollutants were identified as phthalate esters and long-chain alkenes by GC-MS, and a certain amount of inorganic pollutants by X-ray photoelectron spectroscopy.
Figures and Tables |
References |
Related Articles |
Metrics
Select
Reaction kinetics of CaC2 formation from powder and compressed feeds
Renxing Wang,Zhenyu Liu,Leiming Ji,Xiaojin Guo,Xi Lin,Junfei Wu,Qingya Liu
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 517-525.
https://doi.org/10.1007/s11705-016-1585-z
The production of CaC2 from coke/lime powders and compressed powder pellets are low cost and fast processes. A number of studies have reported the reaction kinetics of these reactions but they are still not well understood and the proposed kinetic models are not comparable due to differences in the reaction conditions. Therefore the reaction behavior of CaO/C powders (0.074 mm) and cubes (5 mm × 5 mm × (4.6–5.1) mm) compressed from a mixture of powders have been studied using thermal gravimetric analysis (TGA) at 1700– 1850 °C. Kinetic models were obtained from the TGA data using isoconversional and model-fitting methods. The reaction rates for the compressed feeds were lower than those for the powder feeds. This is due to the reduced surface area of the compressed samples which inhibits heat transfer from the surrounding environment (or the heating source) to the sample. The compression pressure had little influence on the reaction rate. The reaction kinetics of both the powder and the compressed feeds can be described by the contracting volume model f (α ) = 3(1−α )2/3 , where α is the conversion rate of reactant. The apparent activation energy and pre-exponential factor of the powder feed were estimated to 346–354 kJ?mol− 1 and 5.9 × 107 min− 1 , respectively, whereas those of the compressed feed were 305–327 kJ?mol− 1 and 3.6 × 106 min− 1 , respectively.
Figures and Tables |
References |
Supplementary Material |
Related Articles |
Metrics
Select
Process simulation and economic analysis of reactor systems for perfluorinated compounds abatement without HF effluent
Boreum Lee,Sunggeun Lee,Ho Young Jung,Shin-Kun Ryi,Hankwon Lim
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 526-533.
https://doi.org/10.1007/s11705-016-1590-2
New and efficient reactor systems were proposed to treat perfluorinated compounds via catalytic decomposition. One system has a single reactor (S-1), and another has a series of reactors (S-2). Both systems are capable of producing a valuable CaF2 and eliminating toxic HF effluent and their feasibility was studied at various temperatures with a commercial process simulator, Aspen HYSYS® . They are better than the conventional system, and S-2 is better than S-1 in terms of CaF2 production, a required heat for the system, natural gas usage and CO2 emissions in a boiler, and energy consumption. Based on process simulation results, preliminary economic analysis shows that cost savings of 12.37% and 13.55% were obtained in S-2 at 589.6 and 621.4 °C compared to S-1 at 700 and 750 °C, respectively, for the same amount of CaF2 production.
Figures and Tables |
References |
Related Articles |
Metrics
Select
Streptomyces ghanaensis VITHM1 mediated green synthesis of silver nanoparticles: Mechanism and biological applications
Mani Abirami, Krishnan Kannabiran
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 542-551.
https://doi.org/10.1007/s11705-016-1599-6
We present the microbial green synthesis of silver nanoparticles (NPs) by Streptomyces ghanaensis VITHM1 strain (MTCC No. 12465). The secondary metabolites in the cell free supernatant of this bacterium when incubated with 1 mmol/L AgNO3 , mediated the biological synthesis of AgNPs. The synthesized AgNPs were characterized by UV-visible spectrum, X-ray diffraction (XRD), atomic force microscope, scanning electron microscopy equipped with energy dispersive spectroscopy, transmission electron microscopy, FT-IR spectroscopy, dynamic light scattering and zeta potential. They were highly stable and, spherical in shape with the average size of 30?50 nm. The secondary metabolites involved in the formation of AgNPs were identified gas chromatography-mass spectrography. The 3D structure of the unit cell of the synthesized AgNPs was determined using XRD data base. The synthesized AgNPs exhibited significant antibacterial activity against tested bacterial pathogens, and did not show haemolysis on human red blood cells. This green synthesis could provide a new platform to explore and use AgNPs as antibacterial therapeutic agents.
Figures and Tables |
References |
Related Articles |
Metrics
Select
Synthesis and properties of novel organogelators functionalized with 5-iodo-1,2,3-triazole and azobenzene groups
Ziyan Li,Yaodong Huang,Dongli Fan,Huimin Li,Shuxue Liu,Luyuan Wang
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 552-561.
https://doi.org/10.1007/s11705-016-1589-8
Two series of 5-iodo-1,2,3-triazole derivatives containing azobenzene group(s) were synthesized and their gelling properties were tested. Those containing two azobenzene groups (B series) have better gelation performance than those containing one azobenzene group (A series). The microstructure of organogels and the driving force of gelation were investigated by scanning electron microscopy and 1 H NMR, respectively. It was found that π-π stacking, van der Waals interaction, and dipole-dipole interaction were the main forces of gelation. All the tested organogels are photoresponsive and those from B series are smarter than that from A series. Henry δ p -δ h diagrams of compounds A1 , A2 , and B2 were constructed on the basis of their gelation performance and the Hansen solubility parameters of related solvents. The constructed Henry δ p -δ h diagrams can be used to estimate the behavior of three compounds in any untested solvent.
Figures and Tables |
References |
Related Articles |
Metrics
Select
Thin-film composite forward osmosis membranes with substrate layer composed of polysulfone blended with PEG or polysulfone grafted PEG methyl ether methacrylate
Baicang Liu,Chen Chen,Pingju Zhao,Tong Li,Caihong Liu,Qingyuan Wang,Yongsheng Chen,John Crittenden
Front. Chem. Sci. Eng.. 2016, 10 (4 ): 562-574.
https://doi.org/10.1007/s11705-016-1588-9
To advance commercial application of forward osmosis (FO), we investigated the effects of two additives on the performance of polysulfone (PSf) based FO membranes: one is poly(ethylene glycol) (PEG), and another is PSf grafted with PEG methyl ether methacrylate (PSf-g-PEGMA). PSf blended with PEG or PSf-g-PEGMA was used to form a substrate layer, and then polyamide was formed on a support layer by interfacial polymerization. In this study, NaCl (1 mol?L−1 ) and deionized water were used as the draw solution and the feed solution, respectively. With the increase of PEG content from 0 to 15 wt-%, FO water flux declined by 23.4% to 59.3% compared to a PSf TFC FO membrane. With the increase of PSf-g-PEGMA from 0 to 15 wt-%, the membrane flux showed almost no change at first and then declined by about 52.0% and 50.4%. The PSf with 5 wt-% PSf-g-PEGMA FO membrane showed a higher pure water flux of 8.74 L?m−2 ?h−1 than the commercial HTI membranes (6–8 L?m−2 ?h−1 ) under the FO mode. Our study suggests that hydrophobic interface is very important for the formation of polyamide, and a small amount of PSf-g-PEGMA can maintain a good condition for the formation of polyamide and reduce internal concentration polarization.
Figures and Tables |
References |
Related Articles |
Metrics
13 articles