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1.
Xiaoju Yan Ruiling Bao Shuili Yu Qiongfang Li Qingfeng Jing 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(9):1479-1485
This article is aimed at studying on the roles of the hydroxyl radicals, photo-generated holes, and oxygen in the photocatalytic degradation of humic acid (HA) in acid and alkaline conditions. The results indicate that hydroxyl radicals?? scavenger alone can inhibit the photocatalytic degradation process completely in alkaline condition, which implies that photo-generated holes cannot directly degrade the organic matter in alkaline condition. Moreover, the reaction sites between hydroxyl radicals and HA is on the TiO2 surface in acid condition. But in alkaline condition, hydroxyl radicals diffuse and react with HA in the solution. The generation of hydroxyl radicals almost stops and the photocatalytic degradation is inhibited seriously without oxygen, which illustrates that oxygen plays an important role in the photocatalytic degradation of HA. 相似文献
2.
Summary We present a study of the chromatographic behaviour of sixty ions on thin layers of cellulose, employing as eluents aqueous solutions of tartrate, at various molarities (from 0.1 to 1.0 mol dm–3 and pH values (from 2.0 to 10.0 obtained with aqueous ammonia). The ions migrate, whether they are complexed with the tartrate or not, with high RF values and are not influenced by variation of the tartrate concentration. The pH variations, owing to the formation of partial hydrolysis or precipitation products or possibly ammonia complexes, have a greater effect on the rate of ion migration and cause a decrease in the RF values. We show interesting separations obtained with these eluents.This work has been in part supported by C.N.R. of Italy 相似文献
3.
以亚甲基蓝(MB)为模拟废水污染物,Ag3PO4为光催化剂,固定污染物初始浓度、催化剂用量、光照强度和照射时间等,探讨不同浓度的无机阴、阳离子(NO-3、Cl-、SO2-4、Na+、Ca2+、Mg2+、Al 3+)对Ag3PO4光催化降解偶氮染料MB的影响.结果表明,Na+和NO-3对Ag3PO4光催化降解MB没有明显的影响;Cl-在一定程度上对MB的降解具有促进作用;SO2-4、Ca2+、Mg2+、Al3+在不同程度上抑制了该光催化反应的进行,且抑制顺序为SO2-4Ca2+Mg2+Al 3+. 相似文献
4.
Photocatalytic degradation (PCD) reactions of cationic methylene blue (MB) and anionic humic acid (HA) were studied in naked
TiO2 and fluorinated TiO2 (F-TiO2) suspensions in order to investigate how the modification of the TiO2 surface functional group influenced PCD reactions. Adsorption behaviors of MB and HA in the naked TiO2 followed a typical pH-dependent electrostatic interaction mechanism. On the other hand, those in the F-TiO2 were markedly changed and even showed a reversed dependence in specific pH ranges due to surface fluoride interrupting the
interaction of substrates and surface titanol groups. PCD rates of MB (k
MB) and its N-demethylation (Δλ
max) were significantly increased by surface fluorination below circum-neutral pH range, in particular, by a factor of 12 and
54 at pH 2, respectively. In the case of HA, the fluorination had an insignificant effect on its degradation rate but appeared
to change its degradation behavior. It has been suggested that, although the primary effect of fluorination enhances the photocatalytic
production of hydroxyl radicals, the change in electrostatic interaction with substrates could affect PCD as well. 相似文献
5.
Sundararajan M Rajaraman G Ghosh SK 《Physical chemistry chemical physics : PCCP》2011,13(40):18038-18046
The speciation of uranyl ions in fulvic acid (FA) and humic acid (HA), based on models of larger sizes, is systematically studied using density functional theory (DFT). Four uranyl binding sites are suggested for FA and based on their energetics, the preferential binding sites are proposed. The computed binding sites include two chelating types, one through the carboxylate group and one via the hydroxo group. A systematic way to attain the possible structure for Stevenson's HA model is carried out using a combined molecular dynamics (MD) and quantum chemical approach. Calculated structures and energetics reveal many interesting features such as conformational flexibility of HA and binding of hydrophobic molecules in agreement with the experimental suggestions. Five potential binding sites are proposed for uranyl binding to HA and the calculated geometries correlate nicely with the experimental observations. Our binding energy calculations reveal that apart from uranyl binding at the carboxylate functional group, binding at other functional groups such as those involving quinone and hydroxo sites are also possible. Finally, based on our cluster calculations the strength of uranyl binding to HAs and FAs is largely influenced by neighbouring groups via hydrogen bonding interactions. 相似文献
6.
In this study, simultaneous adsorption of copper ions and humic acid (HA) from Aldrich onto an activated carbon is investigated. It is found that the HA adsorption in the absence of copper decreases as the pH is increased. It leads to a reduction of 34.7% in the specific surface area of carbon. There exists a critical concentration (CC) of HA for copper adsorption. At HA concentrations < CC, a decrease in copper adsorption is observed; however, the HA improves the adsorption at HA concentrations > CC. An increase in ionic strength can enhance the copper uptake; however, zinc and/or cobalt ions have an insignificant influence on copper adsorption. The adsorption is significantly increased by citric acid, whereas addition of EDTA slightly decreases the uptake. An intraparticle diffusion model is successfully used to describe the copper adsorption kinetics. 相似文献
7.
We investigated the effect of humic acid and solution pH on the uptake of the radionuclides, (83)Rb, (137)Cs, (54)Mn, (65)Zn, (88)Y, (102)Rh, and (75)Se in rice plants by the multitracer technique. The addition of humic acid to a culture medium containing SiO(2) increased the uptake of Mn and Zn at pH 4.3, whereas their uptake was decreased at pH 5.3. Humic acid depressed the uptake of Y at both pHs. The uptake of Se, which does not interact with humic acid, was not affected by its presence. These results suggest that uptake of the radionuclides by the rice plant is regulated by the affinity of radioactive nuclides for humic acid, as well as by the soil solution's pH. 相似文献
8.
《Journal of photochemistry and photobiology. A, Chemistry》2007,185(2-3):289-294
In this study, we investigated the effects of four inorganic anions (Cl−, SO42−, H2PO4−/HPO42−, and HCO3−/CO32−) on titanium dioxide (TiO2)-based photocatalytic oxidation of aqueous ammonia (NH4+/NH3) at pH ∼ 9 and ∼10 and nitrite (NO2−) over the pH range of 4–11. The initial rates of NH4+/NH3 and NO2− photocatalytic oxidation are dependent on both the pH and the anion species. Our results indicate that, except for CO32−, which decreased the homogeneous oxidation rate of NH4+/NH3 by UV-illuminated hydrogen peroxide, OH scavenging by anions and/or direct oxidation of NH4+/NH3 and NO2− by anion radicals did not affect rates of TiO2 photocatalytic oxidation. While HPO42− enhanced NH4+/NH3 photocatalytic oxidation at pH ∼ 9 and ∼10, H2PO4−/HPO42− inhibited NO2− oxidation at low to neutral pH values. The presence of Cl−, SO42−, and HCO3− had no effect on NH4+/NH3 and NO2− photocatalytic oxidation at pH ∼ 9 and ∼10, whereas CO32− slowed NH4+/NH3 but not NO2− photocatalytic oxidation at pH ∼ 11. Photocatalytic oxidation of NH4+/NH3 to NO2− is the rate-limiting step in the complete oxidation of NH4+/NH3 to NO3− in the presence of common wastewater anions. Therefore, in photocatalytic oxidation treatment, we should choose conditions such as alkaline pH that will maximize the NH4+/NH3 oxidation rate. 相似文献
9.
The mechanism of formation of apH gradient along a paper strip is discussed, and an equation has been derived making possible the calculation of thepH along the carrier. An equation is given relating thepH and the place of ion focusing to the stability constant. The distances between the focused zones have been estimated for
the system Fe−Sr−Y, and the results are compared with the experimental data. 相似文献
10.
Summary Thin-layers of an intermediately acidic cation exchanger, cellulose phosphate (P-cellulose), have systematically been used
to study the chromatographic behavior of 58 inorganic ions in both hydrochloric acid and acid ammonium thiocyanate media (0.01–2.0
mol dm−3). In both solvent systems, the R
f
values of many bivalent cations increase with increasing concentration of the acid and thiocyanate. Polyvalent metal ions
including beryllium (II) and the others are strongly retained on the P-cellulose in the acid and thiocyanate systems tested.
Palladium(II), mercury(II), ruthenium(III), rhenium(VII), arsenic(III), selenium(IV) and tellurium(IV) are not adsorbed on
P-cellulose to any great extent. For silver(I), indium(III), gold(III), and platinum(IV), there are marked differences in
the chromatographic behavior between hydrochloric acid and acid ammonium thiocyanate systems. Multicomponent separations conducted
on P-cellulose plates with these eluents are presented. 相似文献
11.
A. V. Gorokhovsky E. V. Tret’yachenko M. A. Vikulova D. S. Kovaleva G. Yu. Yurkov 《Russian Journal of Applied Chemistry》2013,86(3):343-350
Results of a synthesis and study of the photocatalytic properties of nanosize powder compounds based on amorphous potassium polytitanate, modified with nickel ions are reported. The effect of protonation is noted, resulting in an increase in the specific surface area and adsorption capacity of the substances obtained. It is shown that the increase in the photoactivity of potassium polytitanates modified in aqueous solutions of nickel salts is due to the formation of multiple potassium polytitanate-NiO x semiconductor heterojunctions on the surface and to the doping of potassium polytitanate with nickel ions. 相似文献
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14.
The extraction of 33 elements by a 0.1M solution of di-n-butyl carbamoylphosphonate in chloroform has been investigated as a function of hydrochloric acid concentration. The results show that this new extradant readily extracts most of the elements in a high oxidation state, including the trivalent rare earths, from hydrochloric acid at concentrations greater than 6 M. 相似文献
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16.
Suzuko Yamazaki Hiroyuki Abe Toshifumi Tanimura Yousuke Yamasaki Kenji Kanaori Kunihiko Tajima 《Research on Chemical Intermediates》2009,35(1):91-101
The thermal treatment of TiO2 pellets prepared by the sol–gel method decreased the photocatalytic activity. The activity divided by the specific surface
area of the pellets for the complete mineralization of ethylene or chloroform was maximized at the firing temperature of 400°C.
For the photocatalytic degradation of trichloroethylene (TCE), most of them were converted to chlorinated by-products, such
as dichloroacetic acid, chloroform, and phosgene, and the stoichiometric ratio of [CO2]formed/[TCE]degraded showed a maximal value at 400°C. The electron spin resonance (ESR) spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)
in the flow injection system indicated that firing at 400°C gave the highest signal intensity of DMPO–OH adducts. These findings
indicated that the OH radical was produced most effectively on the TiO2 fired at 400°C, which would be related to the content of anatase and rutile. Concerning the formation of chlorinated by-products
from TCE, more dichloroacetic acid (DCAA) were detected and less CHCl3 and COCl2 were formed at lower firing temperatures, suggesting that the branching ratio of chloroethoxy radicals to the formation of
DCAA or CHCl3 and COCl2 by C–C bond scission depended on the firing temperature. 相似文献
17.
内蒙胜利褐煤腐殖酸对煤平衡复吸水的影响 《燃料化学学报》2016,44(11):1281-1286
研究了褐煤中重要的成分腐殖酸对褐煤水分的影响。测定了内蒙胜利褐煤中腐殖酸含氧官能团的含量,并分析了褐煤、棕黑腐殖酸和残余煤的等温吸附和脱附曲线。通过Dent吸附等温模型研究了褐煤和棕黑腐殖酸第一层吸附和第二层吸附。结果表明,胜利褐煤2/5羧基和1/5羟基是由腐殖酸提供的。棕黑腐殖酸相对褐煤孔径和孔容较小,不利于水簇的形成。腐殖酸对褐煤的复吸水是不利的 相似文献
18.
Surface-area-exclusion chromatography using Whatman glass microfibre filters modified by adsorption of aluminium ions as
a stationary phase was used to evidence the different interfacial behaviour of aluminium ion complexed (tritium labelled)
humic acids. Histograms with adsorption peaks, plateaux and humps on the stationary phase showed the various adsorption characteristics
of the modified humic acid. The absence of adsorption for those constituents which were recovered in the effluent showed the
very low degrees of complexation by aluminium ions to be responsible for the absence of interaction of the components with
the stationary phase.
Received: 24 July 2000 Accepted: 20 December 2000 相似文献
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20.
Summary Thin-layer chromatography of iron(II) and (III), cobalt(II), copper(II), and nickel(II) 1-nitroso-2-naphtholates has been described. The separation was effected on a silica gel layer by employing two different solvent systems: benzene-amyl ether (50 25v/v) and benzene-dioxane (40 17v/v). The metal complexes were detected by their characteristic colours.
Zusammenfassung Die Dünnschichtchromatographie von Eisen(II) und (III), Kobalt(II), Kupfer(II) und Nickel(II) in Form ihrer 1-Nitroso-2-Naphtholate wurde beschrieben. Die Trennung wurde auf einer Kieselgelschichte unter Verwendung zweier Laufmittelsysteme durchgeführt: Benzol-Amyläther (50 25v/v) und Benzol-Dioxan (40 17v/v). Die Metallkomplexe sind an ihrer charakteristischen Farbe kenntlich.
Résumé On décrit la chromatographie en couche mince des-nitroso-naphtolates de fer-II et -III, cobalt-II, cuivre-Il et nickel-II. On effectue la séparation sur une couche de gel de silice en utilisant deux systèmes différents de solvants: benzène-éther amylique (50 25v/v) et benzène-dioxane (40 17v/v). On décèle les complexes métalliques d'après leurs colorations caractéristiques.相似文献