共查询到20条相似文献,搜索用时 31 毫秒
1.
Guozhong Wu Yosuke Katsumura Norihisa Chitose Zhihua Zuo 《Radiation Physics and Chemistry》2001,60(6):1909-650
Absorption spectrum and the yield of eaq− determined in quaternary benzene/water and dodecane/water microemulsions were found to be identical with those in pure water. This indicates that the excess electrons produced in the oil droplets cross the oil/water interface and appear in the aqueous phase as hydrated electrons. On the contrary, it was found that the OH radical yield measured by converting into (SCN)2.− was directly proportional to the water content and there was no contribution from the oil phase. The eaq− decay in aerated microemulsion showed that the [O2] in the aqueous phase was decreasing with continuous pulse irradiation and the estimated G(–O2) in the oil was higher than in water. However, peroxides were predominantly formed in the aqueous phase and almost not in the oil. Rate constants for the addition of eaq− and OH to benzene in the benzene/water microemulsion and the following bimolecular decay of cyclohexadienyl and hydroxycyclohexadienyl radicals agree well with those reported in aqueous solutions. 相似文献
2.
The reaction of baicalin (β-
-glucopyranosiduronic acid, 5,6-dihydroxy-oxo-2-phenyl-4H-1-benzopyran-7-yl) scavenging hydroxyethyl peroxyl radicals (RO2.) was studied with the aid of radiolysis of aerated ethanol. Two main stable products were separated by reverse HPLC and their possible molecular structures were derived from their UV, IR and FAB-MS spectra. The dependence of G(H2O2), G(CH3CHO) and G(-baicalin) on the concentration of baicalin showed that one baicalin molecule could inhibit the formation of one H2O2 molecule and two CH3CHO molecules. A possible reaction mechanism between baicalin and RO2. radical was suggested. 相似文献
3.
Di-cysteine substituted hypocrellin B (DCHB) is a new water-soluble photosensitizer with significantly enhanced red absorption at wavelengths longer than 600 nm over the parent compound hypocrellin B (HB). The photosensitizing properties (Type I and/or Type II mechanisms) of DCHB have been investigated in dimethylsulfoxide (DMSO) and aqueous solution (pH 7.4) using electron paramagnetic resonance (EPR) and spectrophotometric methods. In anaerobic DMSO solution, the semiquinone anion radical of DCHB (DCHB•−) is predominantly photoproduced via self-electron transfer between excited- and ground-state DCHB species. The presence of an electron donor significantly promotes the formation of the reduced form of DCHB. When a deoxygenated aqueous solution of DCHB and an electron donor are irradiated with 532 nm light, the hydroquinone of DCHB (DCHBH2) is formed via the disproportionation of the first-formed DCHB•− and second electron transfer to DCHB•− from the electron donor. When oxygen is present, singlet oxygen (1O2), superoxide anion radical (O2•−) and hydroxyl radical (•OH) are produced. The quantum yield of 1O2 generation by DCHB photosensitization is estimated to be 0.54 using Rose Bengal as a reference, a little lower than that of HB (0.76). The superoxide anion radical is also significantly enhanced by the presence of electron donors. Moreover, (O2•−) upon disproportionation generated H2O2 and ultimately the highly reactive •OH via the Haber-Weiss reaction pathway. The efficiency of (O2•−) generation by DCHB is obviously enhanced over that of HB. These findings suggest that the photodynamic actions of DCHB may proceed via Type I and Type II mechanisms and that this new photosensitizer retains photosensitizing activity after photodynamic therapy-oriented chemical modification. 相似文献
4.
Reactions of OH radicals and some one-electron oxidants with 2-aminopyridine (2-AmPy) and 3-aminopyridine (3-AmPy) were studied in aqueous solutions using pulse radiolysis technique. The OH adduct of 2-AmPy at pH 9 has an absorption maximum at 360 nm along with a weak absorption band in the visible region and was found to be reactive with oxygen. The rate constant for its reaction with O2 was determined to be 1.0×108 dm3 mol−1 s−1. At pH 4 also, the OH adduct of 2-AmPy has an absorption band at 360 nm. However, there are differences in the absorption at other wavelengths. From the plot of ΔOD vs. pH at 340 nm, the pKa of the OH adduct was determined to be 6.5. Among the specific oxidants, only SO4−√ radicals were able to oxidize 2-AmPy. In the case of 3-aminopyridine (3-AmPy), the transient species formed by OH radical reaction at pH 9 has an absorption maximum at 410 nm with shoulder bands on both the sides. Its absorption spectrum at pH 4 was different indicating the existence of a pK value for the OH adduct. pKa of 3-AmPy-OH radical adduct species was evaluated to be 5.7. This adduct species was also found to be reactive with oxygen (k=7.6×106 dm3 mol−1 s−1). Specific one-electron oxidants like N3√, Br2−√ C2−√ and SO4−√ were able to oxidize 3-AmPy indicating that it is easier to oxidize 3-AmPy as compared to 2-AmPy. 相似文献
5.
Kensuke Kuwamura Tohru Ikegami Sadahiro Masuo Shinjiro Machida Nobuo Tanaka Akira Itaya 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):232-238
The direct photolysis of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solution was investigated under monochromatic ultraviolet (UV) irradiation at 254 nm. ABTS was found to be directly photolyzed by UV irradiation to yield the one-electron oxidized radical, ABTS+, which is a blue-green colored persistent radical species that has strong visible absorption bands. The photochemical production of ABTS+ was strongly dependent on the solution pH and the presence of dissolved oxygen. The presence of dissolved oxygen increased the quantum yields at pH 3, whereas it inhibited the production of ABTS+ at pH 6.5. Spectrophotometric and spectrofluorometric data indicated that ABTS photolysis may occur as a result of the transfer of one-electron between the singlet excited state and the ground state of ABTS. Observations made during UV/H2O2 experiments with ABTS suggested that the dependence of the photoloysis of ABTS on the solution pH and the presence of dissolved oxygen is related to the role of the hydroperoxyl/superoxide radical (HO2/O2−), which appears to be formed via a secondary reaction of the reduced intermediate of ABTS with dissolved oxygen. The proposed photolytic reactions were supported by the observed stoichiometry between the amount of ABTS+ radicals produced and the amount of ABTS molecules decomposed. 相似文献
6.
Ganglin Xue Bin Liu Huaiming Hu Jianhui Yang Jiwu Wang Feng Fu 《Journal of Molecular Structure》2004,690(1-3):95-103
A new family of heteropolytungstate complexes (NH4)21[Ln(H2O)5{Ni(H2O)}2As4W40O140]·xH2O(Ln=Y, Ce, Pr, Nd, Sm, Eu, Gd) were prepared by the reaction of Na27[NaAs4W40O140]·60H2O with NiCl2·6H2O and Ln(NO3)3·xH2O at pH≈4.5. The crystal structures of (NH4)21[Gd(H2O)5{Ni(H2O)}2As4W40O140]·51H2O was determined by X-ray diffraction analysis and element analysis. The compound crystallizes in the monoclinic space group P21/n with a=19.754(3), b=24.298(4), c=39.350(6) Å, β=100.612(3)°, V=18564(5) Å3, Z=2, R1(wR2)=0.0544(0.0691). The central site S1 and two opposite sites S2 of the big cyclic ligand [As4W40O140]28− are occupied by one Ln3+and two Ni2+, respectively, each site supply four Od coordinating to metal ion, another one water molecule and other five water molecules coordinate, respectively, to Ni2+and Ln3+. Polyanion [Ln(H2O)5{Ni(H2O)}2As4W40O140]21− has C2v symmetry. IR and UV–vis spectra of [NaAs4W40O140]27− of the title compounds are discussed. 相似文献
7.
Antoine Aboukais Elena A. Zhilinskaya Jean-Franois Lamonier Igor N. Filimonov 《Colloids and surfaces. A, Physicochemical and engineering aspects》2005,260(1-3):199-207
Oxygen adsorption experiments were performed on evacuated and prereduced CeO2/SiO2 and CeO2/Al2O3 catalysts with and without platinum. Considerable amounts of the superoxide radical ions were stabilized on all the samples. Signal parameters suggest Ce4+–O2− positioning for all detectable superoxide species. Physisorbed oxygen broadens O2− signal beyond detection for all the alumina-based samples, while the same procedure for all the silica-based samples did not change signal shape of O2− species. Detectable O2− species are localized in the bulk of ceria and the nature of support (silica or alumina) determines the number of oxygen vacancies and the rate of electron transfer. XRD data suggest that for alumina-based samples small and/or thin islands of ceria dominate, while comparatively large ceria particles are stabilized on the surface of silica-based samples with the same ceria content. Average size of ceria crystallites is still not determining factor and cannot account for the observed differences. Higher concentrations of paramagnetic species may be stabilized on alumina-based samples and thus, sensor-like behavior towards gaseous oxygen at room temperature was detected for them—oxygen admission reversibly changes superoxide lineshape. For silica samples, only minor changes of O2− lineshapes were typical upon the change of the partial pressure of oxygen at ambient and low temperatures. Addition of platinum has little effect on parameters of the O2− signal, except an enhancement of the superoxide decay in the reducing media. Possible site for O2− stabilization inside the lattice of CeO2 was proposed and relevance of the observed effects to the redox catalysis discussed. 相似文献
8.
R.M. Quint H.R. Park P. Krajnik S. Solar N. Getoff K. Sehested 《Radiation Physics and Chemistry》1996,47(6):835-845
Using pulse radiolysis and steady state γ-radiolysis in combination with product analysis by HPLC the radiolytic degradation mechanism of 4-chloroanisole (4-ClAn) has been elucidated. Pulse radiolysis experiments show that OH radicals react in neutral aqueous N2O saturated solutions with 4-ClAn by addition to all aromatic ring positions to yield hydroxycyclohexadienyl radicals (OH-adducts), k(OH + 4-ClAn) = 6.5 × 109dm3mol−1s−1. Those OH-adducts formed on ipso positions of the molecule subsequently undergo HCl or CH3OH elimination forming methoxyphenoxyl- and chlorophenoxyl radicals. Their yield corresponds to 20% of the OH-radicals, whereby the distribution is roughly 3:1 in favor of the methoxyphenoxyl radicals, which reflects the stronger ortho-, para-directing activity of the methoxy group. The OH-adducts decay second order, 2k = 1 × 109dm3mol−1s−1. The presence of oxygen leads to its addition on the hydroxycyclohexadienyl radicals, k(OH-adduct + O2) = 3.2 × 108dm3mol−1s−1. In airfree solution the reaction of H-atom with the substrate, k(H + 4-ClAn) = 1.2 × 109dm3mol−1s−1, results in H-adducts which decay in bimolecular reactions, 2k = 8.2 × 108dm3mol−1s−1. The rate constant for the reaction of the solvated electrons has been determined to k(eaq− + 4-ClAn) = 2 × 109dm3mol−1s−1. The absorption spectra of H- and OH-adducts were measured in the range of 280–450 nm. The products analysed by HPLC after γ-radiolysis in dependence of dose (100–600 Gy) are given for N2O-, air-, oxygen- and argon saturated neutral aqueous solutions. In conditions favoring the OH radical oxidation 4-chlorophenol, 4-methoxyphenol, 5-chloro-2-methoxyphenol and 2-chloro-5-methoxyphenol were determined as final products. In the presence of Ar, where about equal amounts of OH and eaq− are present, additionally anisole could be detected. Under both reaction conditions the amount of identified products is about 20% of decomposed 4-ClAn. The reaction of eaq− leads to reductive dechlorination which corresponds quantitatively to the degradation of the substrate. In the presence of air or solutions saturated with pure oxygen predominantly hydroquinone, 4-chlorophenol and muconic acids are formed and the material balance is 50%. The efficient dechlorination (60% of the decomposed 4-ClAn) as well as ring fragmentation products as intermediates en route to complete mineralization in oxygenated solution indicate that high energy radiation is a promising method for degradation of halogenated aromatic compounds in water. Variation of dose rates from 79 Gy min−1 to 266 Gy min−1 did not show any influence on the product distribution. 相似文献
9.
Thermal decomposition of mixed ligand thymine (2,4-dihydroxy-5-methylpyrimidine) complexes of divalent Ni(II) with aspartate, glutamate and ADA (N-2-acetamido)iminodiacetate dianions was monitored by TG, DTG and DTA analysis in static atmosphere of air. The decomposition course and steps of complexes [Ni(C5H6N2O2)(C4H5NO4)2−(H2O)2]·H2O, [Ni(C5H6N2O2)(C5H7NO4)2−(H2O)2]·H2O and [Ni(C5H6N2O2)(C6H8N2O5)2−(H2O)2]·1.5H2O were analyzed. The final decomposition products are found to be the corresponding metal oxides. The kinetic parameters namely, activation energy (E*), enthalpy (ΔH*), entropy (ΔS*) and free energy change of decomposition (ΔG*) are calculated from the TG curves using Coats–Redfern and Horowitz–Metzger equations. The stability order found for these complexes follows the trend aspartate > ADA > glutamate. 相似文献
10.
In the present work, CdSe/ZnS core-shell quantum dots were synthesized and conjugated with enzymes, glucose oxidase (GOD) and horseradish peroxidase (HRP). The complex of enzyme-conjugated QDs was used as QD-FRET-based probes to sense glucose. The QDs were used as an electron donor, whereas GOD and HRP were used as acceptors for the oxidation/reduction reactions involved in oxidizing glucose to gluconic acid. Electron transfer between the redox enzymes and the electrochemical reduction of H2O2 (or O2) occurred rapidly, resulting in an increase of the turnover rate of the electron exchange between the substrates (e.g. glucose, H2O2 and O2) and the enzymes (GOD, HRP), as well as between the QDs and the enzymes. The transfer of non-radiative energy from the QDs to the enzymes resulted in the fluorescence quenching of the QDs, corresponding to the increase in the concentration of glucose. The linear detection ranges of glucose concentrations were 0–5.0 g/l (R = 0.992) for the volume ratios of 10/5/5, 0.2–5.0 g/l (R = 0.985) for the volume ratios of 10/5/3 and 1.0–5.0 g/l (R = 0.982) for the volume ratios of 10/5/0. Temperature (29–37 °C), pH (6–10) and some ions (NH4+, NO3−, Na+, Cl−) had no interference effect on the glucose measurement. 相似文献
11.
Juan M. Coronado A. Javier Maira Arturo Martínez-Arias Jos Carlos Conesa Javier Soria 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):213-221
EPR measurements reveal remarkable differences on the type of radicals produced after UV illumination of TiO2, CeO2 and 0.8% CeO2/TiO2 photocatalysts. Photoactivation of the TiO2 sample in vacuum results in the formation of Ti4+–O− species and a small amount of Ti3+ centers. In the presence of adsorbed oxygen, irradiation of this material also generates Ti4+–O3− radicals. In the case of the CeO2/TiO2 catalyst, the ceria component is present in a highly dispersed state, as indicated by XRD and UV–Vis diffuse reflectance spectra (DRS) results. Accordingly, the only type of Ce4+–O2− adducts generated on the CeO2/TiO2 sample are indicative of the presence of two-dimensional patches of ceria on the anatase surface. On the other hand, photoactivation of the CeO2/TiO2 sample in the presence of oxygen also leads to the formation of some Ti4+–O− and Ti3+ centers. In the case of the CeO2 sample, superoxide radicals are observed upon irradiation in vacuum and subsequent oxygen adsorption. Further irradiation of this material in the presence of oxygen increases the amount of Ce4+–O2− radicals and simultaneously generates new species, which are tentatively assigned to Ce4+–O2H radicals. Photocatalytic activity was tested for toluene oxidation, and the results obtained show that the photodegradation rate is slightly lower for CeO2/TiO2 than for the TiO2 sample. However, the selectivity towards benzaldehyde (6–13%) is comparable for both materials. In the case of CeO2, the photo-oxidation rate is an order of magnitude lower than for TiO2, although mineralization of toluene is almost complete. Photoactivity results are discussed in connection with the characteristics of the radicals observed. 相似文献
12.
Kevin Henbest Peter Douglas Michael S. Garley Andrew Mills 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):299-305
The rate constant for the reaction between the sulphate radical (SO4√−) and the ruthenium (II) tris-bipyridyl dication (Ru(bipy)32+) is (3.3±0.2)×109 mol−1 dm3 s−1 in 1 mol dm−3 H2SO4 and (4.9±0.5)×109 mol−1 dm3 s−1 in 0.1 mol dm−3, pH 4.7 acetate buffer. The SO4√−radical produced by the electron transfer quenching of Ru(bipy)32+* by S2O82− reacts rapidly with both acetate buffer and chloride ions. These side reactions result in a reduction in the overall quantum yield of Ru(bipy)33+ production and reduced reaction selectivity when Ru(bipy)32+* is quenched by persulphate. 相似文献
13.
The paper reports results of a study on the specific adsorption of F−, Cl−, Br−, I−, ClO3−, BrO3−, IO3− and IO4− on hydrous γ-Al2O3. The isotherms of the anion adsorption and the adsorption dependencies on pH and the ionic strength of the solution have been determined under the equilibrium conditions. According to the degree of affinity to γ-Al2O3, the anions can be ordered as: I−3−
−−3−3−4−−. It has been established that the sorption of IO4− and F− involves the formation of surface complexes in the inner co-ordination sphere, whereas that of Cl−, Br−, I−, ClO3−, BrO3− and IO3− takes place through formation of ion pair complexes in the outer co-ordination sphere. In the dynamic system, the exchange isoplanes and elution curves have been determined for selected anions on columns filled with Al2O3. It has been shown that γ-Al2O3 can be used for isolation and concentration of IO3− from natural waters in order to decrease the limit of the ions determination to 2 μg l−1. Using differential pulse voltammetry (DPV), after isolation and concentration on γ-Al2O3, the content of iodates has been determined in mineral, marine and tap water doped with these ions. 相似文献
−
14.
Xiao-Bing Cui Ji-Qing Xu Lan Ding Hong Ding Ling Ye Guo-Yu Yang 《Journal of Molecular Structure》2003,660(1-3):131-137
The compound [Zn(H2O)4]2[H2As6V15O42(H2O)]·2H2O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å3, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H2As6V15O42(H2O)]4− anions and [Zn(H2O)4]2+ cations linked through hydrogen bonds into a network. The [H2As6V15O42(H2O)]6− cluster consists of 15 VO5 square pyramids linked by three As2O5 handle-like units. 相似文献
15.
Ritu Bala Raj Pal Sharma Paloth Venugopalan William T.A. Harrison 《Journal of Molecular Structure》2007,830(1-3):8-13
In an effort to utilize the [Co(NH3)6]3+ cation as a new anion receptor (binding agent) for dihydroxy dicarboxylate anion i.e., tartrate, orange single crystals of hexaamminecobalt(III) chloride (R,R)-tartrate monohydrate, [Co(NH3)6]Cl(C4H4O6)·H2O, were obtained by reacting hexaamminecobalt(III) chloride with potassium–sodium tartrate tetrahydrate in a 1:1 molar ratio in hot water. The single crystal X-ray structure determination of [Co(NH3)6]Cl(C4H4O6)·H2O revealed that a distinctive network of hydrogen bonding interactions (N–HO, N–HCl−, O–HO) stabilize the crystal lattice. This is the first complex salt of hexaamminecobalt(III) with dihydroxy dicarboxylate anion i.e., tartrate. 相似文献
16.
B. Sieklucka W.
asocha L. M. Proniewicz R. Podgajny H. Schenk 《Journal of Molecular Structure》2000,520(1-3):155-163
The bimetallic [Pt(NH3)4]2[W(CN)8][NO3]·2H2O is characterised by single-crystal X-ray diffraction [S.G.P21/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)* separations of 4.77(2), 4.55(2)* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO3− between parallel [Pt(1)(NH3)4]2+ planes and the second consists of [W(CN)8]3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH3)4]2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH3 ligands, water molecules and oxygen atoms of NO3− counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer. 相似文献
17.
Formation constants for recrystallized thymol blue were determined in water, using the SQUAD and SUPERQUAD programs. The best model correlating spectrophotometric, potentiometric and conductimetric data was fitted with the dissociation of HL−=L2−+H+−log K=8.918±0.070 and H3L2−=2L2−+3H+−log K=29.806±0.133 with the SUPERQUAD program at variable low ionic strength (1.5×10−4–3.0×10−4 M); and HL=L2−+H+−log K=8.9±0.000, H3L2− =2L2−+3H+−log K=30.730±0.032, H4L2=2L2−+4H+−log K=32.106±0.033 with SQUAD at 1.1 M ionic strength. 相似文献
18.
Ott Horvth Kenneth L. Stevenson 《Journal of photochemistry and photobiology. A, Chemistry》1999,120(3):11751-190
Excitation of solutions of Fe(bipy)2(CN)2 by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)2 (CN)2+, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)2(CN)2 to form Fe(bipy)2(CN)2−, and comparison of the decay constants in the three media (H2O: k = 2.8 × 1010 M−1 s−1; CTAB: k = 2.9 × 1010 M−1 s−1; SDS: k = 5.5 × 109 M−1 s−1), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between eaq− and Fe(bpy)2(CN)2+. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV2+) cations and NO3− anions were measured in the three systems, and the results indicate that for scavenging by MV2+ the rate constants are decreased in the micelle systems (k in H2O, 8.4 × 1010; CTAB, 3.5 × 1010 and SDS, 1.58 × 1010 M−1 s−1), whereas for NO3− the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H2O, 8.3 × 109; CTAB, 7 × 108; and SDS, 2.05 × 1010 M−1 s−1). For the comproportionation reaction between Fe(bipy)2(CN)2+ and Fe(bipy)2(CN)2− both micelles reduce the rate (k in H2O, 3.3 × 1010; CTAB, 2.3 × 1010; and SDS, 1.05 × 1010 M−1s−1), but while the reaction of Fe(bipy)2(CN)2+ with MV+ is increased in CTAB compared to water, it is slowed in SDS (k in H2O, 2.4 × 1010; CTAB, 8.9 × 1010; and SDS, 1.8 × 1010 M−1s−1). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles. 相似文献
19.
Influence of operating conditions on the retention of phosphate in water by nanofiltration 总被引:1,自引:0,他引:1
The objective of this study was to investigate the retention of phosphate anions, H2PO4− and HPO42−, by nanofiltration. The first part of this study deals with the characterisation of the NF200 membrane used in permeation experiments with aqueous solutions of neutral organic and charged inorganic solutes. In the second part the effects of feed pressure, ionic strength, concentration and pH on the retention of phosphate anions were investigated. Results show that the membrane is negatively charged, its pore radius is around 0.5 nm and the retention order for the salts tested was R(Na2SO4) > R(NaCl) > R(CaCl2). The retentions of phosphate anions are in the order of 85% for H2PO4− and 96% for HPO42−. They are relatively high when compared to retentions of other anions with the same charge. The retentions of phosphate anions, particularly the monovalent species, depend on the chemical parameters (feed concentration, ionic strength, and pH) and applied pressure. The experimental data were analysed using the Speigler–Kedem model and the transport parameters, i.e., the reflection coefficient (σ) and solute permeability (Ps) have been determined. 相似文献
20.
The title compound (PTCMA) was irradiated in O2-free dioxane solution by 60Co-γ-rays or by 100 nsec-pulses of 16 MeV electrons. At concentrations below ca 0.04 base mol/l, main-chain scission occurred as was concluded from the decrease of the light scattering intensity (LSI). G(S) = 3.7 ± 0.4 was independent of the polymer concentration and equal to G(S) observed with solid PTCMA. This result indicates that in dilute solution main-chain scission is induced by the direct action of radiation on the polymer. The free radical [presumably ---C(CH3)---(CH2)---] giving rise to main-chain scission has a lifetime of 2.6 msec. It reacts with ethane thiol (k = 6.6 × 104M−1sec−1). At concentrations above 0.04 base mol/l, the polymer crosslinked (gel formation, increase of the LSI according to 2nd order kinetics). It is assumed that crosslinking is due to the combination of radicals of the type ---CH2---C(CH3)(COOCH2CCl2)--- formed via dissociative electron capture processes involving mainly electrons in spurs that otherwise recombine with parent ions. This conclusion was inferred from the finding that [(τ1/2)1]−1 ∞ (cpolymer)2[(τ1/2)1): 1st half-life of LSI increase after the pulse, cpolymer: polymer concentration]. 相似文献