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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbon nanotubes are novel materials that have been investigated for diverse applications, but only a few studies have been focused on environmental issues. In this work, we report on the efficient adsorption of phenol and cadmium ions on N-doped carbon nanotubes (CNx), which have been modified in air at different temperatures. The pristine and modified CNx nanotubes were characterized by SEM, TGA, elemental analysis and their surface areas were also determined. The adsorption experiments of toxic pollutants were carried out in batch reactors at 25 degrees C. The characterization of modified CNx by these techniques showed an increase in oxygen content and surface area in comparison with the pristine CNx tubes. The individual adsorption capacity was 0.10 and 0.07 mmol/g for phenol and Cd(2+), respectively. The experimental data of the competitive adsorption of phenol and Cd(2+) revealed that the cadmium removal was favored as the phenol concentration increased, whereas the phenol adsorption capacity was slightly affected at any cadmium concentration. These results suggest that modified CNx tubes have a great potential in environmental applications as adsorbents of organic and inorganic compounds in aqueous phases. In addition, first-principles calculations were carried out in order to elucidate the mechanism of Cd(2+) adsorption on CNx.
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PMID:Simultaneous adsorption of Cd2+ and phenol on modified N-doped carbon nanotubes: experimental and DFT studies. 1940 43

Verticillium longisporum is a vascular fungal pathogen presently threatening oilseed rape production in Europe. Systemic spread and vascular responses were studied in a susceptible ('Falcon') and a resistant genotype (SEM 05-500256) of Brassica napus. Colonization of both genotypes after dip-inoculation of the roots followed by quantitative polymerase chain reaction revealed similarities only in the initial stages of root penetration and colonization of the hypocotyl, while a substantial invasion of the shoot was only recorded in 'Falcon'. It is concluded that the type of resistance represented in SEM 05-500256 does not prevent the plant base from being invaded as it is internally expressed well after root penetration and colonization of the plant base. The morphological and biochemical nature of barriers induced in the hypocotyl tissue upon infection was studied with histochemical methods accompanied by biochemical analyses. Histochemical studies revealed the build-up of vascular occlusions and the reinforcement of tracheary elements through the deposition of cell wall-bound phenolics and lignin. Furthermore, the accumulation of soluble phenolics was observed. Although these responses were found in vascular tissues of both genotypes, they occurred with a significantly higher intensity in the resistant genotype and corresponded with the disease phenotype. In the resistant genotype phenols were differentially expressed in a time-dependent manner with preformed soluble and cell wall-bound phenolics at earlier time points and de novo formation of lignin and lignin-like polymers at later stages of infection. This is the first study identifying a crucial role of phenol metabolism in internal defense of B. napus against V. longisporum and locating the crucial defense responses in the plant hypocotyl.
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PMID:Internal resistance in winter oilseed rape inhibits systemic spread of the vascular pathogen Verticillium longisporum. 1952 78

A new chitosan derivative has been synthesized by crosslinking a metal complexing agent, [6,6'-piperazine-1,4-diyldimethylenebis (4-methyl-2-formyl) phenol] (L), with chitosan (CTS). The resulting material (CCTSL) was characterized by elemental (CHN), spectral (FTIR and solid-state NMR), thermal (TGA and DTA), and structural (powder XRD and SEM) analyses. Adsorption experiments (pH dependency, kinetics, and equilibrium) of CCTSL toward various metal ions such as Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II) were carried out at 25 degrees C. The results showed that the adsorption was dependent on the pH of the solution, with a maximum capacity between pHs 6.5 and 8.5. The kinetics was evaluated by applying the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The maximum adsorption capacity was 1.21 mmol g(-1) for Cu(II) and the order of adsorption capacities for the metal(II) ions studied was found to be Cu(II)>Ni(II)>Cd(II)> or =Co(II)> or =Mn(II)> or =Fe(II)> or =Pb(II).
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PMID:Synthesis and characterization of a crosslinked chitosan derivative with a complexing agent and its adsorption studies toward metal(II) ions. 1954 61

In order to find an effective, stable, environmentally compatible electrode for the elimination of organic pollutants, preparation of a novel graphite electrode (NGE) was explored using graphite, epoxy resin, curing agent and acetone as materials. Water, ethanol aqueous solution, acetone, ultrasound-acetone and electrochemical method were used to pretreat the electrode. The first three methods obtained poor effect. Ultrasound-acetone could improve the pretreatment, but satisfied results were difficult to achieve. Electrochemical method could work effectively. Electrochemical oxidation of phenol was carried out on NGE and commercial graphite electrode (CGE), respectively. UV spectroscopy was used to study evolution of phenol oxidation. The results showed that CGE resulted in accumulation of bensoquine in the electrolyte, though it was more effective than NGE on phenol oxidation. While much less benzoquinone was found in the electrolyte for NGE. TOC removal rate were 40% and 31% for NGE and CGE, respectively. SEM study showed that CGE was severely corroded after phenol degradation, while NGE was undamaged, showing good stability.
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PMID:[Preparation of a novel graphite electrode and its effect on phenol degradation]. 1955 10

Carbonaceous adsorbents prepared from olive stones biomass and novolac resin, as well as a commercial activated carbon for comparison reasons, have been examined for the removal of phenol and 3-nitrophenol from aqueous solutions. All carbonaceous adsorbents have been characterized by SEM-EDAX analysis and mercury porosimetry. The experimental data were examined according to the following kinetic models: pseudo first order, pseudo second order, Natarajan and Khalaf, Elovich, power function equations and intraparticle diffusion. By plotting the amount of adsorbate (phenol or 3-nitrophenol) adsorbed per unit mass of adsorbent b(t), versus the square root of time, four regions can be distinguished (A, B, C and D). By applying all the previously described models it is concluded that: (a) the intraparticle diffusion model is valid for the B and C region, whereas macropore diffusion and mesopore diffusion, respectively, take place. The pore diffusion coefficient, D for each carbonaceous material was calculated and indicated that the adsorption is controlled by diffusion, (b) the power model for the adsorption of phenol on each of the three carbonaceous materials is acceptable only for the C region and (c) the pseudo second order for the adsorption of 3-nitrophenol on each of the three carbonaceous materials is acceptable for the C region.
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PMID:Adsorption kinetics of phenol and 3-nitrophenol from aqueous solutions on conventional and novel carbons. 1962 23

A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g(-1). Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R(2) > 0.99). Thermodynamic parameters including the Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees), and entropy (DeltaS degrees) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 degrees C.
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PMID:Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: equilibrium, kinetic and thermodynamic study. 1965 23

In the present paper a novel mechanochemical process for the elimination of organic pollutants dissolved in water is proposed. In this regard, phenol aqueous solutions (100mgL(-1)) were ball-milled for 0, 12, 18, 24, 36, 48, and 72h with and without a well-characterized (XRD, SEM, and N(2) Adsorption), rutile powder catalyst and the reaction products analyzed with UV and GC/MS. It was found that when the catalyst was not included in the process, phenol was not affected, but when it was included, phenol was decomposed. The catalyst itself did not change and the reaction follows a pseudo-first-order kinetics. Besides, intermediates which are characteristic of the ()OH radical mechanism were found in the reaction products. Then, a mechanism similar to those accepted for other advanced oxidation processes was proposed. The value measured for the pseudo-first-order reaction constant was very low, indicating that the reported process is inefficient. Nevertheless, this problem could be solved by applying catalysts consisting of particles with smaller diameters.
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PMID:Degradation of phenol by mechanical activation of a rutile catalyst. 1968 5

Manganese nodule leached residue is a good adsorbent. Adsorption of phenol (PhOH) on water washed manganese nodule leached residue (WMNLR), waste materials from manganese nodules processing plant, has been investigated. The adsorbent (WMNLR) used for the removal of phenolic compounds were characterized by EDX, FTIR, SEM and BET surface area measurement before and after the adsorption process. Adsorption experiments were carried out to study the effect of various parameters like adsorbent dose, pH, adsorbate concentration, reaction time, temperature and calcination temperature. WMNLR calcined at 400 degrees C showed highest adsorption capacity. The equilibrium adsorption data for phenol was analyzed by using Langmuir isotherm model. The maximum adsorption of phenol was obtained at pH 3 (about 95% for adsorbent dose 1g/L and 30 mg/L adsorbate concentration). The increase in percentage of adsorption with increase in temperature indicates that adsorption is endothermic in nature. The pseudo-second-order kinetics was followed in the adsorption process.
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PMID:Removal of phenolic compounds from aqueous solutions by adsorption onto manganese nodule leached residue. 1983 80

Dipyrone (Dp), 4-aminoantipyrine (AA) and antipyrine (At) administered iv and Dp administered icv delay gastric emptying (GE) in rats. The participation of capsaicin (Cps)-sensitive afferent fibers in this phenomenon was evaluated. Male Wistar rats were pretreated sc with Cps (50 mg/kg) or vehicle between the first and second day of life and both groups were submitted to the eye-wiping test. GE was determined in these animals at the age of 8/9 weeks (weight: 200-300 g). Ten minutes before the study, the animals of both groups were treated iv with Dp, AA or At (240 micromol/kg), or saline; or treated icv with Dp (4 micromol/animal) or saline. GE was determined 10 min after treatment by measuring % gastric retention (GR) of saline labeled with phenol red 10 min after orogastric administration. Percent GR (mean +/- SEM, N = 8) in animals pretreated with Cps and treated with Dp, AA or At (35.8 +/- 3.2, 35.4 +/- 2.2, and 35.6 +/- 2%, respectively) did not differ from the GR of saline-treated animals pretreated with vehicle (36.8 +/- 2.8%) and was significantly lower than in animals pretreated with vehicle and treated with the drugs (52.1 +/- 2.8, 66.2 +/- 4, and 55.8 +/- 3%, respectively). The effect of icv administration of Dp (N = 6) was not modified by pretreatment with Cps (63.3 +/- 5.7%) compared to Dp-treated animals pretreated with vehicle (62.3 +/- 2.4%). The results suggest the participation of capsaicin-sensitive afferent fibers in the delayed GE induced by iv administration of Dp, AA and At, but not of icv Dp.
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PMID:Phenylpyrazolone derivatives inhibit gastric emptying in rats by a capsaicin-sensitive afferent pathway. 1985 4

Lignocellulosic materials can significantly contribute to the development of biobased composites. In this work, glyoxal-phenolic resins for composites were prepared using glyoxal, which is a dialdehyde obtained from several natural resources. The resins were characterized by (1)H, (13)C, 2D, and (31)P NMR spectroscopies. Resorcinol (10%) was used as an accelerator for curing the glyoxal-phenol resins in order to obtain the thermosets. The impact-strength measurement showed that regardless of the cure cycle used, the reinforcement of thermosets by 30% (w/w) sisal fibers improved the impact strength by one order of magnitude. Curing with cycle 1 (150 degrees C) induced a high diffusion coefficient for water absorption in composites, due to less interaction between the sisal fibers and water. The composites cured with cycle 2 (180 degrees C) had less glyoxal resin coverage of the cellulosic fibers, as observed by images of the fractured interface observed by SEM. This study shows that biobased composites with good properties can be prepared using a high proportion of materials obtained from natural resources.
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PMID:Biobased composites from glyoxal-phenolic resins and sisal fibers. 1988 Mar 15


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