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排序方式: 共有64条查询结果,搜索用时 15 毫秒
21.
AbstractTwo biomaterials based on the abundant Bulgarian medicinal plants Mentha spicata L. (denoted as MS) and Ruta graveolens L. (denoted as RG) were investigated as environmentally friendly biosorbents for Cu(II) removal from aqueous solutions. Grain size distribution, slurry pH, texture parameters, thermal behavior and mineralogical composition of MS and RG were determined. Instrumental methods such as scanning electron microscopy (SEM), X-ray-diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, differential thermal analysis (DTA), and thermogravimetric analysis (TGA) were used for their characterization. It was demonstrated that the surface morphology of both materials is rough and contains pores that could entrap different pollutants, as well as functional groups that can attach metal ions. In order to examine the feasibility of these materials for use as biosorbents for heavy metals, adsorption experiments were performed. The results for the removal of Cu(II) ions from aqueous solution reveal capabilities suggesting that both materials have potential to be used as promising, efficient and low-cost biosorbents. 相似文献
22.
The initial stage of electrodeposition of silver on a glassy carbon electrode is investigated using a double-pulse potentiostatic method. Data are obtained for the concentration dependence of the steady-state nucleation rate I and conclusions are drawn for the probable mechanism of critical nucleus formation. 相似文献
23.
Vassileva ND van den Ende D Mugele F Mellema J 《Langmuir : the ACS journal of surfaces and colloids》2005,21(24):11190-11200
We study the capillary forces acting on sub-millimeter particles (0.02-0.6 mm) trapped at a liquid-liquid interface due to gravity-induced interface deformations. An analytical procedure is developed to solve the linearized capillary (Young-Laplace) equation and calculate the forces for an arbitrary number of particles, allowing also for a background curvature of the interface. The full solution is expressed in a series of Bessel functions with coefficients determined by the contact angle at the particle surface. For sub-millimeter spherical particles, it is shown that the forces calculated using the lowest order term of the full solution (linear superposition approximation; LSA) are accurate to within a few percents. Consequently the many particle capillary force is simply the sum of the isolated pair interactions. To test these theoretical results, we use video microscopy to follow the motion of individual particles and pairs of interacting particles at a liquid-liquid interface with a slight macroscopic background curvature. Particle velocities are determined by the balance of capillary forces and viscous drag. The measured velocities (and thus the capillary forces) are well described by the LSA solution with a single fitting parameter. 相似文献
24.
Elka Vassileva Janos Sapi Jean-Yves Laronze Catherine Mirand Jean Lévy 《Monatshefte für Chemie / Chemical Monthly》2002,133(2):151-156
Summary. 2′-Dimethylamino-1′-trifluoroacetyl-2-vinylindole derivatives were prepared by trifluoroacetic anhydride assisted oxidation.
Received July 20, 2001. Accepted (revised) September 24, 2001 相似文献
25.
The complex formation of Co2+ and Ni2+ with m-methyl benzamide oxime was studied spectrophotometrically in 60% methanol. The complexes [Co(mMB)2] and [Ni(mMB)2] appear in alkaline solution. The formation constants are lgK=4.15±±0.04 for [Co(mMB)2] and lgK=4.08±0.04 for [Ni(mMB)2] at 25°. The decadic molar extinction coefficients are ε=5000 for [Co(mMB)2] and ε=560 for [Ni(mMB)2], resp. 相似文献
26.
Isolation of Novel Alkaliphilic <Emphasis Type="Italic">Bacillus</Emphasis> Strains for Cyclodextrin Glucanotransferase Production 总被引:1,自引:0,他引:1
Atanasova N Petrova P Ivanova V Yankov D Vassileva A Tonkova A 《Applied biochemistry and biotechnology》2008,149(2):155-167
New alkaliphilic Bacillus producers of cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) were isolated from 17 Bulgarian alkaline and normal habitats
(springs and soils) by three steps of a selection. None of the isolates obtained, producing CGTase, appeared to be thermophilic
in character. One hundred and thirty-seven strains were estimated for CGTase activity by batch cultivation in a liquid alkaline
medium. Twenty-seven of them had a detectable CGTase activity in their culture supernatants under the enzyme assay conditions,
despite of the significant growth of all isolates. The phenotypic properties of three selected strains (20RF, 8SB and 24WE)
were determined. They were aerobic endospore-forming Bacillus strains: two of them were obligated alkaliphiles (20RF and 8SB) and one, alkalitolerant (24WE). Both obligated alkaliphiles
were further characterised by 16S rRNA analysis. According to the full 16S rRNA gene sequences obtained and deposited to the
NCBI GenBank database, both isolated obligated alkaliphiles 20RF and 8SB were clustered into the group of alkaliphilic Bacillus species. The exhibited CGTase production by them (230–250 U ml−1 for 20RF and 130–160 U ml−1 for 8SB) defined these new isolates as promising producers of the enzyme, especially Bacillus sp. 8SB synthesising thermostable alkaline β-CGTase. Both new enzymes from 20RF and 8SB Bacillus strains formed only two types of cyclodextrins, beta and gamma, which could be of interest for their easy separation and
industrial production. 相似文献
27.
This communication presents the synthesis of N-phenylpiperazines (4), using the organobismuth compound (3) as arylating agent. Triarylbismuthine (3) was obtained by condensation of dry BiCl3 with the organolithium intermediate (2). 相似文献
28.
Alicia Cordero Javier García-Maimó Juan R. Torregrosa Maria P. Vassileva Pura Vindel 《Applied Mathematics Letters》2013,26(8):842-848
In this paper, the dynamics of King’s family of iterative schemes for solving nonlinear equations is studied. The parameter spaces are presented, showing the complexity of the family. The analysis of the parameter space allows us to find elements of the family that have bad convergence properties, and also other ones with stable behavior. 相似文献
29.
Nikolay Vassilev Almudena Medina Bettina Eichler-Löbermann Elena Flor-Peregrín Maria Vassileva 《Applied biochemistry and biotechnology》2012,168(5):1311-1318
Cells of Aspergillus terreus, free and immobilized in polyurethane foam, were employed in itaconic acid fermentation processes on glycerol-based media. The purpose was to assess their suitability for animal bone char solubilization and the development of a biotechnological alternative to P fertilizers chemically produced from rock phosphate. Animal bones constitute a renewable source of P that can replace the traditionally used finite, nonrenewable rock phosphate as a P source. Glycerol was an excellent substrate for growth (10.2 g biomass L?1) and itaconic acid production (26.9 g?L?1) by free fungal cells after 120-h fermentation. Simultaneously, A. terreus solubilized the insoluble phosphate to a yield of 23 to 50 %, depending on the particle size and concentration. Polyurethane foam cut into cubes of 0.5–0.6 cm per side, with 0.3 mm pore size and applied at 2.0 g?L?1 proved to be an excellent cell carrier. In repeated batch fermentation, the immobilized mycelium showed a high capacity to solubilize animal bone char, which resulted on average in 168.8 mg?L–1 soluble phosphate per 48-h cycle and 59.4 % yield (percent of total phosphate) registered in the fourth batch. 相似文献
30.
Paunka S. Vassileva Madlena S. Apostolova Albena K. Detcheva Elisaveta H. Ivanova 《Chemical Papers》2013,67(3):342-349
Natural Bulgarian diatomite modified by oxidation with sulfuric acid and H2O2 or by coating with manganese oxide was characterized considering its chemical composition, surface area, pore volume, and structure. Modified diatomites displayed larger surface area and pore volumes in comparison with untreated natural diatomite, which favored their sorption behavior. Sorption properties of diatomites towards Fe3+, Pb2+, Cu2+, Cd2+, Mn2+, Ni2+, Co2+, Cr3+, Pd2+, Ca2+, and Mg2+ were investigated and their sorption capacities were determined. Sorption properties of manganese oxide-modified diatomite were superior to those of diatomite modified by oxidation. Owing to its high sorption capacity towards Co2+, Ni2+, Pb2+, Cr3+, Fe2+, Cu2+, and Cd2+, the manganese oxide-modified diatomite is a promising low-cost sorbent for selective removal of milligram amounts of these toxic metal ions from contaminated water. 相似文献