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排序方式: 共有676条查询结果,搜索用时 15 毫秒
41.
The present study reports the preparation and application of a novel biopolymer-based composite hydrogel (BCH) for removal of synthetic dye rhodamine 6G (Rh6G). BCH was prepared from biopolymer chitosan and acrylic acid monomer, in the presence of initiator (K2S2O8) and cross-linker thiourea using microwave irradiation. Synthesized chitosan-based composite hydrogel was characterized by using analytical techniques including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTA) and differential thermal analysis (DTG). The stability of the adsorbent was demonstrated from its water uptake capacity. The dynamics of water sorption study showed the Fickian behavior. The investigations were continued to assess the adsorption potential of BCH for removal of Rh6G from aqueous solution. The effect of process parameters affecting the adsorption of rhodamine 6G (Rh6G), such as adsorbent dose, initial concentration of pollutant, contact time and pH of the solution was evaluated. Removal efficiency of chitosan-based composite hydrogel (BCH) was found to be 87.31% at pH 7 for BCH dose of 1 g/L after 8 h. The obtained data were fitted to adsorption isotherms and kinetics models. The adsorption equilibrium isotherm and kinetics studies indicated that the pseudo-second-order model and the Freundlich model well described the adsorption equilibrium of Rh6G on BCH. 相似文献
42.
43.
Genotoxicity of silver nanoparticles in Allium cepa 总被引:1,自引:0,他引:1
Mamta Kumari 《The Science of the total environment》2009,407(19):5243-5246
Potential health and environmental effects of nanoparticles need to be thoroughly assessed before their widespread commercialization. Though there are few studies on cytotoxicity of nanoparticles on mammalian and human cell lines, there are hardly any reports on genotoxic and cytotoxic behavior of nanoparticles in plant cells. This study aims to investigate cytotoxic and genotoxic impacts of silver nanoparticles using root tip cells of Allium cepa as an indicator organism. A.cepa root tip cells were treated with four different concentrations (25, 20, 75, and 100 ppm) of engineered silver nanoparticles (below 100 nm size) dispersion, to study endpoints like mitotic index, distribution of cells in mitotic phases, different types of chromosomal aberrations, disturbed metaphase, sticky chromosome, cell wall disintegration, and breaks. For each concentration five sets of microscopic observations were carried out. No chromosomal aberration was observed in the control (untreated onion root tips) and the mitotic index (MI) value was 60.3%. With increasing concentration of the nanoparticles decrease in the mitotic index was noticed (60.30% to 27.62%). The different cytological effects including the chromosomal aberrations were studied in detail for the treated cells as well as control. We infer from this study that silver nanoparticles could penetrate plant system and may impair stages of cell division causing chromatin bridge, stickiness, disturbed metaphase, multiple chromosomal breaks and cell disintegration. The findings also suggest that plants as an important component of the ecosystems need to be included when evaluating the overall toxicological impact of the nanoparticles in the environment. 相似文献
44.
D.C. Electrical conductivity, Hall mobility and magnetic susceptibility measurements on La1?x Sr x CrO3 (0?x?0.25) perovskite ceramic system, and their temperature dependence, have been carried out to understand the nature of the transport mechanism in them. The electrical conductivity and Hall mobility displayed thermally activated temperature dependence with activation energies that varied from 0.13 to 0.23 ev. The variation of the d.c. conductivity of the polycrystalline La1?x Sr x CrO3 with strontium content (X) has been found to be strongly affected by the changes in microstructure. Magnetic susceptibility data indicate that the electronic transport is due to the presence of Cr4+ ions in the lattice, and that the localized level of hopping is associated with the chromium 3d band. 相似文献
45.
The effect of carbon black fillers viz. semireinforcing furnace (SRF), high abrasion furnace (HAF) and intermediate super abrasion furnace (ISAF) carbon blacks on the cure, swelling and mechanical properties of 70/30 EPDM/NBR blend have been investigated. The maximum torque values have been found to be increased with increase in filler loading. Filledsystems have been found to exhibit a reduced solvent uptake tendency compared to the unfilled sample. Blends loaded with ISAF exhibited the lowest toluene uptake among the carbon black filled systems due to the better filler reinforcement. A more uniform morphology has been observed for ISAF‐filled samples compared to the other filler loaded systems. The improvement in the mechanical properties has been observed to be the highest for ISAF‐filled samples followed by HAF and SRF filled systems. This has been attributed to the smaller particle size of ISAF black. The experimental results of mechanical testing have been compared with various theoretical models. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
46.
Tin oxide nanoplatelets (SnO) and nanoparticles (SnO2) were prepared by microwave assisted technique with an operating frequency of 2.45 GHz. This technique permits to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystalline size was evaluated from XRD and found to range from 26 to 34 nm. SEM and TEM analyses showed that the nanoparticles present a platelet-like shaped particle or, a pseudo spherical morphology, after calcination at moderate temperature during which the phase transformation from SnO to SnO2 takes place. Additional FT-IR, density and resistivity measurements were also presented. 相似文献
47.
Purpurin (1,2,4‐trihydroxyanthraquinone) is the major colorant present in the roots of Indian madder (Rubia cordifolia). Its structure is similar to that of disperse dyes. To gain an understanding of the dyefibre interactions involved, kinetic and thermodynamic studies have been conducted with purpurin on nylon fibre. Dyeing corresponds to the Nernst isotherm as linear isotherms were obtained. The dye is found to be sensitive to pH and high temperature. The rate of dye uptake, diffusion coefficient, standard affinity, heat of dyeing and entropy have been calculated and discussed. 相似文献
48.
Niru Kumari Vaibhav Bahadur Marc Hodes Todd Salamon Paul Kolodner Alan Lyons Suresh V Garimella 《International Journal of Heat and Mass Transfer》2010,53(15-16):3346-3356
Enhancement of forced convective heat transport through the use of evaporating mist flow is investigated analytically and by numerical simulation. A two-phase mist, consisting of finely dispersed water droplets in an airstream, is introduced at the inlet of a longitudinally-finned heat sink. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heating of the air inside the heat sink which translates into higher heat-dissipation capacities. The flow and heat transfer characteristics of mist flows are studied through a detailed numerical analysis of the mass, momentum and energy transport equations for the mist droplets and the airstream, which are treated as two separate phases. The coupling between the two phases is modeled through interaction terms in the transport equations. The effects of inlet mist droplet size and concentration on the thermal performance of the heat sink are analyzed parametrically. The results provide insight into the complex transport processes associated with mist flows. The simulations indicate that significantly higher heat transfer coefficients are obtained with mist flows as compared to air flows, highlighting the potential for the use of mist flows for enhanced thermal management applications. 相似文献
49.
Interpenetrating polymer network (IPN) beads consisting of chitosan-glutamic acid were prepared for in vitro study of controlled release of chlorpheniramine maleate (CPM). A viscous solution of chitosan-glutamic acid was prepared
in 2% acetic acid solution, extruded as droplets through a syringe to alkalimethanol solution and the precipitated beads were
crosslinked using glutaraldehyde solution. Swelling and drug release studies were carried out. Transport of release medium
through the semi-IPN depended upon its pH and extent of crosslinking. The structural and morphological studies of beads were
carried out by using a scanning electron microscope (SEM). The larger surface area of beads as well as their ease of handling
makes them ideal agents of controlled release. 相似文献
50.