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排序方式: 共有668条查询结果,搜索用时 15 毫秒
91.
Activation of Candida antarctica lipase B in pressurized fluids for the synthesis of esters
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92.
Luciana Sciascia Selene Casella Giuseppe Cavallaro Giuseppe Lazzara Stefana Milioto Francesco Princivalle Filippo Parisi 《Ceramics International》2019,45(2):2751-2759
Green composites for environmental applications were successfully prepared by intercalation of the biosurfactant Quillaja saponin onto montmorillonite mineral clay on varying pH and surfactant/clay ratio. Equilibrium adsorption isotherms were constructed and the system was characterized by performing TGA and XRD analyses.The efficiency of the surfactant-modified clay in the removal of the organic content present in olive mill wastewaters (OMW) was evaluated by means of spectrophotometric measurements. The interest for this cogent issue comes from the consideration that, despite their high pollutant content, OMW can be considered as a potential resource of several organic compounds which can be recovered for a wide array of pharmaceutical and industrial applications. Two different strategies were proposed. In the first one, dried surfactant/clay hybrids were added to the batch samples under continuous stirring, while in the second alternative approach the organoclays were packed in chromatography column filled with multiple alternate layers of sand and organoclay.These studies revealed the efficacy of the methods used and suggested that the modification of the montmorillonite clay substrate significantly improves the performance of the clay. 相似文献
93.
Torres R García JV Arnau A Perrot H Kim LT Gabrielli C 《The Review of scientific instruments》2008,79(4):045113
The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mVHz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications. 相似文献
94.
The behaviour of copper in oxalic acid solutions was studied both by cyclic voltammetry and electrochemical impedance technique. It was shown that, due to the easy complexation of copper with oxalate ions, the species present in the solution depend on the pH. During the dissolution, it was shown that the electrode was blocked by the precipitation of copper oxalate. On the other hand, a model was proposed to explain the copper deposition in concentrated oxalic acid solution. We found a rather good agreement between the experimental and calculated impedances. 相似文献
95.
Impedance techniques are used to investigate the average dynamic behaviour of a fluidized bed of gold-coated beads in potassium
ferri-ferrocyanide/NaOH solution. A transmission line is used as a model. The main features of the fluidized bed are correctly
interpreted, especially the capacitive high frequency impedance related to the intermittent contacts between the particles.
The use of a nonuniform transmission line is attempted in order to study the influence of a distance dependent charge transfer
mechanism in the bulk of the fluidized bed. 相似文献
96.
Magnetic polystyrene–palygorskite nanocomposite obtained by heterogeneous phase polymerization to apply in the treatment of oily waters
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Antonieta Middea Luciana Spinelli Fernando Gomes de Souza Junior Reiner Neumann Thais Fernandes Fabiano Richard Leite Faulstich Otavio Gomes 《应用聚合物科学杂志》2018,135(15)
Water contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe3O4‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46162. 相似文献
97.
Valeria Di Sarli Gianluca Landi Luciana Lisi Almerinda Di Benedetto 《American Institute of Chemical Engineers》2017,63(8):3442-3449
The potential of diesel particulate filters wash‐coated with highly dispersed nano‐metric ceria particles for continuous regeneration has been investigated. To this end, catalytic filters were prepared, soot‐loaded (avoiding the formation of the cake layer), and regenerated—under isothermal conditions—at temperature ranging from 200–600°C. Results have shown that catalytic oxidation of soot starts from 300°C and, at all temperatures, the selectivity to CO2 is higher than 99%. 475°C is the minimum temperature at which the filter is regenerated via catalytic path. At this temperature, the catalytic filter maintains substantially the same performance over repeated cycles of soot loading and regeneration, indicating that the thermal stability of ceria is preserved. This has been further confirmed by comparison between the outcomes obtained from characterization (X‐ray powder diffraction, N2 adsorption at 77 K, Hg intrusion porosimetry, and scanning electron microscope/energy dispersive X‐ray analysis) of fresh filter and filter subjected to repeated regeneration tests. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3442–3449, 2017 相似文献
98.
Magnetic water treatment for scale prevention 总被引:15,自引:0,他引:15
A home-made magnetic device was built with permanent magnets for treating scaling waters. Its efficiency was evaluated by measuring the remaining ionic calcium at the output of the device by means of an ion selective electrode. The scaling power of the treated water was estimated through an electrochemical scaling test. Chroamperometric curves and chronoelectrogravimetric curves were plotted to obtain the scaling time and the nucleation time of the scale deposition. The variation of the efficiency of the magnetic treatment was studied when the length of treatment, the flow velocity of the scaling water in the device, the material of the pipe where the scaling water flowed were changed. An empirical relationship, which gives the value of the efficiency in function of the length of treatment and the flow velocity, was proposed. Possible mechanisms of action of the magnetic treatment were discussed. 相似文献
99.
Coelho GL Dornelas CB Soares KC dos Santos EP Vergnanini AL dos Santos TC Rodrigues CR Castro HC Dias LR Cabral LM 《Drug development and industrial pharmacy》2008,34(5):536-546
Herein we describe inclusion complexes of commercial sunscreens in cyclodextrins and montmorillonites to generate new sunscreen derivatives with optimized functional properties such as water resistance and skin adherence. Four cyclodextrins (alpha-, beta-, and gamma-cyclodextrin, and beta-dimethyl cyclodextrin) and two montmorillonites (sodium and alkylammonium) were investigated for encapsulating some commercial sunscreens. Our results reveal a good yield and inclusion products with functional properties obtained by using kneading technique on Eusolex 2292 and Eusolex 6007 in beta-cyclodextrin and solubilization method on Eusolex 6007 and NeoHeliopan MA in montmorillonite. In addition, molecular modeling studies indicated flexibility as important for the intercalation of the host molecule. 相似文献
100.
Pietro L Silva DR do Carmo Alberto-Rincon M Duek EA 《Journal of materials science. Materials in medicine》2008,19(3):1069-1074
The development of biodegradable materials has lead to renewed interest in the study of their interactions with the host organism
in order to make the resulting products appropriate for use as temporary materials in clinical research, as well as important
therapeutic applications. The copolymer poly (l-lactic-co-glycolic acid) or PLGA membranes have been used for several purposes. The physical properties of these materials
can be modified by the addition of a plasticizer, such as the triethylcitrate, to provide flexibility and porosity to the
implants, and enhance control of the polymer degradation time. Membranes with 7% plasticizer and without plasticizer (triethylcitrate)
were compared. Membranes without plasticizer were denser and more compact than those with plasticizer. Two days and 30 days
after implantation, the membranes with and without plasticizer showed little degradation. Sixty days and 120 days after implantation,
the membranes with 7% plasticizer showed more cell invasion, and tissue adherence, as well as rapid degradation when compared
to membranes without plasticizer. 相似文献