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  • 1
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    Seasonal characteristics of phosphorus sorption by sediments from plain lakes with different trophic statuses (2018)
    Royal Society
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    Publication Date: 2018-08-16
    Description: Phosphorus (P) sorption in sediments plays a significant role in trophic status of a lake. This study investigated the characteristics of P sorption in sediments from three lakes with different trophic statuses (moderately eutrophic, lightly eutrophic and moderately trophic) through kinetic, batch equilibrium and thermodynamic experiments. Results show that pseudo-second-order kinetics best describe P sorption in sediments from the three lakes. Fitting by modified Langmuir and Freundlich isotherms indicates that the moderately trophic lake sediment has higher sorption capacity (maximum of 0.848 mg g –1 at 35°C) than the sediments of the other two lakes at different temperatures (5, 15, 25 and 35°C). Thermodynamic results indicate that the processes of P sorption of the three sediments are spontaneous, entropy-driven and endothermic reactions. The risk of P release in sediments was analysed according to the calculated results of isotherms combined with the change in P fraction. Sediments from the moderately eutrophic lake act as a source in summer. The lightly eutrophic and moderately trophic lakes act as sources in spring and winter, and a pool in summer and autumn, respectively. Furthermore, the amounts of reductant-soluble P, calcium-bound P and iron-bound P are significantly related to the sorption capacity of sediments from the three lakes ( p 〈 0.05). The different sediments have different P release risk, and P fraction in sediment is one of the significant factors of P sorption.
    Keywords: environmental science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 2
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    Improving the signal subtle feature extraction performance based on dual improved fractal box dimension eigenvectors (2018)
    Royal Society
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    Publication Date: 2018-05-03
    Description: Because of the limitations of the traditional fractal box-counting dimension algorithm in subtle feature extraction of radiation source signals, a dual improved generalized fractal box-counting dimension eigenvector algorithm is proposed. First, the radiation source signal was preprocessed, and a Hilbert transform was performed to obtain the instantaneous amplitude of the signal. Then, the improved fractal box-counting dimension of the signal instantaneous amplitude was extracted as the first eigenvector. At the same time, the improved fractal box-counting dimension of the signal without the Hilbert transform was extracted as the second eigenvector. Finally, the dual improved fractal box-counting dimension eigenvectors formed the multi-dimensional eigenvectors as signal subtle features, which were used for radiation source signal recognition by the grey relation algorithm. The experimental results show that, compared with the traditional fractal box-counting dimension algorithm and the single improved fractal box-counting dimension algorithm, the proposed dual improved fractal box-counting dimension algorithm can better extract the signal subtle distribution characteristics under different reconstruction phase space, and has a better recognition effect with good real-time performance.
    Keywords: mathematical physics, pattern recognition
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 3
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    Doping induced dielectric anomaly below the Curie temperature in molecular ferroelectric diisopropylammonium bromide (2018)
    Royal Society
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    Publication Date: 2018-11-29
    Description: A dielectric anomaly induced by doping has been observed at about 340 K in chlorine-doped diisopropylammonium bromide. The dielectric anomaly has a switchable behaviour, which indicates potential applications on switches and sensors. Temperature-dependent Raman spectrum, X-ray diffraction and differential scanning calorimetry do not show any anomaly around the dielectric anomaly temperature, which prove that the dielectric anomaly does not come from structure phase transition and has no specific heat variety. It is assumed that this dielectric anomaly can be attributed to the freezing of ferroelectric domain walls induced by the pinning of point defects.
    Keywords: physical chemistry, chemical physics
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 4
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    Environment-friendly wood fibre composite with high bonding strength and water resistance (2018)
    Royal Society
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    Publication Date: 2018-04-05
    Description: With the growing depletion of wood-based materials and concerns over emissions of formaldehyde from traditional wood fibre composites, there is a desire for environment-friendly binders. Herein, we report a green wood fibre composite with specific bonding strength and water resistance that is superior to a commercial system by using wood fibres and chitosan-based adhesives. When the mass ratio of solid content in the adhesive and absolute dry wood fibres was 3%, the bonding strength and water resistance of the wood fibre composite reached the optimal level, which was significantly improved over that of wood fibre composites without adhesive and completely met the requirements of the Chinese national standard GB/T 11718-2009. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations revealed that the excellent performance of the binder might partly be due to the amide linkages and hydrogen bonding between wood fibres and the chitosan-based adhesive. We believe that this strategy could open new insights into the design of environment-friendly wood fibre composites with high bonding strength and water resistance for multifunctional applications.
    Keywords: materials science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
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  • 5
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    Catalytic methyl esterification of colophony over ZnO/SFCCR with subcritical CO2: catalytic performance, reaction pathway and kinetics (2018)
    Royal Society
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    Publication Date: 2018-05-03
    Description: A heterogeneous catalyst (ZnO/SFCCR) composed of ZnO supported on spent fluid cracking catalyst by wet impregnation was synthesized and applied to the esterification of colophony acids with methanol under subcritical CO 2 conditions. The catalyst was characterized by SEM-EDS, BET, ICP, FTIR, XRD and Py-IR. An experimental set-up involving a new injection technique was designed to promote the heterogeneous methyl esterification, and the subcritical CO 2 played a role in auxiliary acid catalysis (a pH range of 3.54–3.91), increasing the lifespan of ZnO/SFCCR, reducing the viscosity of the system to promote gas–liquid mass transfer. A maximum conversion rate of 97.01% was obtained in a relatively short time of 5 h. Kinetic experiments were performed from 190 to 220°C using a special high-temperature sampling device and analysing aliquots with high-performance liquid chromatography. A new reaction pathway, involving methyl abietate, methyl dehydroabietate, methyl neoabietate and methyl palustrate along with other kinds of colophony acids, was developed. The kinetic parameters were obtained using the Levenberg–Marquardt nonlinear least-squares method, and the activation energies for the isomerizations of neoabietic and palustric acids and for the methyl esterification of neoabietic, abietic, palustric and dehydroabietic acids were found to be 107.09, 113.95, 68.99, 49.85, 75.43 and 59.20 kJ mol –1 , respectively. The results from the kinetic model were in good agreement with experimental values.
    Keywords: synthetic chemistry, chemical engineering
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 6
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    A Ni-based catalyst with polyvinyl pyrrolidone as a dispersant supported in a pretreated fluid catalytic cracking catalyst residue for C9 petroleum resin (C9 PR) hydrogenation (2018)
    Royal Society
    Details
    Publication Date: 2018-05-24
    Description: A Ni-based catalyst (Ni-PVP/PFC3R) with polyvinyl pyrrolidone (PVP) as a dispersant supported in a pretreated fluid catalytic cracking catalyst residue (PFC3R) was synthesized and applied to C9 petroleum resin (C9 PR) hydrogenation. For comparison, a Ni catalyst without PVP (Ni/PFC3R) was prepared in the same way. Ni-PVP/PFC3R exhibited higher activity and better stability. The catalysts were characterized by X-ray diffraction, scanning electron microscope, H 2 -temperature programmed reduction/temperature programmed desorption, Fourier transform infrared spectroscopy and the Brunauer–Emmett–Teller method. The catalysts had a smaller crystallite size and stronger interactions between the Ni species and the PFC3R support in the presence of PVP. The effects of nickel loading, H 2 pressure, temperature and reaction time for C9 PR hydrogenation over Ni-PVP/PFC3R were investigated. The bromine number was reduced to 1.25 under the following conditions: nickel content of 12 wt%, PVP amount of 1.5 wt%, temperature of 270°C, H 2 pressure of 8 MPa and reaction time of 240 min.
    Keywords: chemical engineering
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
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  • 7
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    The effect of thermo-oxidative ageing on crystallization, dynamic and static mechanical properties of long glass fibre-reinforced polyamide 10T composites (2018)
    Royal Society
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    Publication Date: 2018-06-21
    Description: The performances and microstructure of long glass fibre-reinforced polyamide 10T (PA10T/LGF) composites that experienced different ageing temperatures (160 and 200°C) with increasing ageing time are characterized by differential scanning calorimetry (DSC), mechanical analysis, thermogravimetric analysis (TGA) and scanning electron microscopy to probe the correlation between properties of the composites and thermo-oxidative ageing. The DSC results show that PA10T/LGF composites occur on degradation, the fracture of molecular chains and the destruction of crystallization structure, which leads to the crystallization and melting peaks of PA10T/LGF composites to shift to high temperature. On the basis of dynamic mechanical analysis data, the reduction of the interfacial bonding between the glass fibre and PA10T matrix and the motion of molecular chain segments result in the thermo-oxidative ageing of composites. According to the calculation of activation energy ( E ), thermo-oxidative temperature and ageing time can bring about the decline of the E value, proving the deterioration in performance of PA10T/LGF composites. In view of TGA, the increase in the thermo-oxidative temperature and ageing time promotes the degradation of PA10T/LGF composites. The tensile, flexural and notched impact strengths of PA10T/LGF composites decline with prolonging the ageing temperature and time. The surface of materials produces some microcracks and the cross-section surface of PA10T/LGF composites becomes rougher.
    Keywords: materials science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
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  • 8
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    A novel acid catalyst based on super/subcritical CO2-enriched water for the efficient esterification of rosin (2018)
    Royal Society
    Details
    Publication Date: 2018-07-05
    Description: Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO 2 –enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO 2 –H 2 O binary system, as calculated based on gas–liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO 2 pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius–Polanyi equation. The presence of super/subcritical CO 2 -enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.
    Keywords: chemical engineering, green chemistry
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
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  • 9
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    Preparation of hollow iron/halloysite nanocomposites with enhanced electromagnetic performances (2018)
    Royal Society
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    Publication Date: 2018-01-25
    Description: Nanostructures loaded on halloysite nanotubes (HNTs) have attracted global interest, because the nanotubular HNTs could extend the range of their potential applications. In this study, we fabricated a novel nanocomposite with hollow iron nanoparticles loaded on the surface of HNTs. The structure of the iron nanoparticles can be adjusted by ageing time. Owing to the increased remnant magnetization and coercivity values, the nanocomposites loaded with hollow iron nanoparticles showed better electromagnetic performance than that with solid iron nanoparticles. This study opens a new pathway to fabricate halloysite nanotubular nanocomposites that may gain applications in the catalytic degradation of organic pollutants and electromagnetic wave absorption.
    Keywords: materials science, nanotechnology
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
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  • 10
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    Evaluation and mechanism of ammonia nitrogen removal using sediments from a malodorous river (2018)
    Royal Society
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    Publication Date: 2018-03-22
    Description: Malodorous rivers are among the major environmental problems of cities in developing countries. In addition to the unpleasant smell, the sediments of such rivers can act as a sink for pollutants. The excessive amount of ammonia nitrogen (NH 3 –N) in rivers is the main factor that causes the malodour. Therefore, a suitable method is necessary for sediment disposition and NH 3 –N removal in malodorous rivers. The sediment in a malodorous river (PS) in Beijing, China was selected and modified via calcination (PS-D), Na + doping (PS-Na) and calcination–Na + doping (PS-DNa). The NH 3 –N removal efficiency using the four sediment materials was evaluated, and results indicated that the NH 3 –N removal efficiency using the modified sediment materials could reach over 60%. PS-DNa achieved the highest NH 3 –N removal efficiency (90.04%). The kinetics study showed that the pseudo-second-order model could effectively describe the sorption kinetics and that the exterior activated site had the main function of P sorption. The results of the sorption isotherms indicated that the maximum sorption capacities of PS-Na, PS-D and PS-DNa were 0.343, 0.831 and 1.113 mg g –1 , respectively, and a high temperature was favourable to sorption. The calculated thermodynamic parameters suggested that sorption was a feasible or spontaneous ( G 〈 0), entropy-driven ( S 〉 0), and endothermic ( H 〉 0) reaction.
    Keywords: materials science, environmental science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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