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1.
E. Chmielewská-Horváthová J. Lesný 《Journal of Radioanalytical and Nuclear Chemistry》1995,200(4):351-363
The possibility to use the monoionic Ag+-form (eventually Hg+- and Hg2+- forms) of clinoptilolite of domestic origin for radioactive iodide elimination from waters has been studied. The capacity of the monoforms of clinoptilolite towards iodide exceeds many times that of the capacity of clinoptilolite in natural form. Due to the low solubility product of AgI, Hg2I2 and HgI2 iodides generate precipitates on the zeolite surface. Rtg analyses of the silver form of clinoptilolite after sorption of iodide demonstrate the formation of new crystals on the zeolite surface. The influence of interfering anions on the adsorption capacity of silver clinoptilolite towards iodide was investigated, too. Kinetic curves of iodide desorption from the surface of silver and mercury clinoptilolite were compared. Simultaneously, adsorption isotherms for the systems aqueous iodide solution/Ag–, Hg-clinoptilolite were determined. 相似文献
2.
Sorption of51Cr(VI) by MnO2 has been studied as a function of pH and ionic concentration in the presence of certain added cations and anions. The findings are explained in the light of deprotonation/hydroxyl ion association reaction on oxide surface and its subsequent interaction with the tracer. Infrared spectroscopy has shown the chemical interaction of Cr(VI) on the surface of MnO2. The influence of certain interfering ions has been shown on the sorption of51Cr(VI) on MnO2 surface. An attempt has been made to concentrate traces of51Cr under optimum experimental conditions. The experimental observation shows that the activity sorbed under specified conditions can be recovered appreciably by leaching the pre-adsorbed carrier. 相似文献
3.
Dorota Jermakowicz-BartkowiakBo?ena N. Kolarz 《European Polymer Journal》2002,38(11):2239-2246
Two resins with different matrices, both bearing aminoguanidyl ligands, were obtained and used for gold sorption from hydrochloric acidic and from alkali solutions. Resin 1 was a aminoguanidine derivative of poly(acrylonitril-co-vinyl acetat-co-divinyl benzene) terpolymer (AN/VA/DVB), (67:27:10 wt.%), and Resin 2 the same derivative of gel expanded poly(vinylbenzyl chloride-co-divinylbenzene) copolymer (VBC/DVB). The resins sorption capacity and sorption isotherms of both resins were determined for AuCl4− and Au(CN)2− anions. Resin 2 revealed the best sorption of gold from acidic and alkali solutions: 68 and 23 mg/g, respectively. The effect of the HCl concentration on AuCl4− removal from solution was investigated. Gold was recovered quantitatively from both resins using a 5% thiourea solution in 0.1 HCl. Both resins remained ability of multiple gold sorption and desorption under acidic conditions. 相似文献
4.
K. Bhagyashree R. K. Mishra R. Shukla Sharayu Kasar Aishwarya Kar Sumit Kumar Sanjay Kumar C. P. Kaushik A. K. Tyagi B. S. Tomar 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1561-1566
Nano-crystalline MnO2 has been synthesized by the method of alcoholic hydrolysis of KMnO4 and its potential as a sorbent for plutonium present in the low level liquid waste (LLW) solutions was investigated. The kinetic studies on the sorption of Pu by MnO2 reveal the attainment of equilibrium sorption in 15 h, however 90 % of sorption could be achieved within an hour. In the studies on optimization of the solution conditions for sorption, it was observed that the sorption increases with the pH of the aqueous solution, attains the maximum value of 100 % at pH = 3 and remains constant thereafter. The sorption was found to be nearly independent of the ionic strength (0.01–1.0 M) of the aqueous solutions maintained using NaClO4, indicating the inner sphere complexation between the Pu4+ ions and the surface sites on MnO2. Interference studies with different fission products, viz., Cs+, Sr2+ and Nd3+, revealed decrease in the percentage sorption with increasing pH of the suspension indicating the competition between the metal ions. However, at the metal ion concentrations prevalent in the low level liquid waste solutions, the decrease in the Pu sorption was only marginally decreased to 90 % at pH = 3, the decrease being more in the case of Nd3+ than that in the case of Cs+. This study, therefore, shows nano-crystalline MnO2 can be used as a sorbent for separation of Pu from LLW solutions. 相似文献
5.
Carbazole solid crystals have been mechanically attached to platinum or gold electrodes by two different methods and investigated
by cyclic electrochemical quartz crystal microbalance measurements in the presence of aqueous acidic media. It was demonstrated
that oxidative dimerization and polymerization can also be accomplished under such conditions. During electropolymerization,
anions and water molecules enter the surface layer; however, these species leave the film after the reduction of the polymer
formed. The mass changes observed in the course of the redox transformations of polycarbazole film can be explained by potential-
and time-dependent sorption/desorption of H+ and ClO4
− ions. The electroactivity of the polymer diminishes in more dilute acid media; however, it is recovered again in concentrated
HClO4 solutions. In more dilute acid solution the extent of the water sorption (film swelling) increases. 相似文献
6.
A. O. Nizhegorodova S. N. Eliseeva E. G. Tolstopjatova G. G. Láng D. Zalka M. Ujvári V. V. Kondratiev 《Journal of Solid State Electrochemistry》2018,22(8):2357-2366
Electrochemical behavior of poly-3,4-ethylenedioxythiophene composites with manganese dioxide (PEDOT/MnO2) has been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance at various component ratios and in different electrolyte solutions. The electrochemical formation of PEDOT film on the electrode surface and PEDOT/MnO2 composite film during the electrochemical deposition of manganese dioxide into the polymer matrix was gravimetrically monitored. The mass of manganese dioxide deposited into PEDOT at different time of electrodeposition and apparent molar mass values of species involved into mass transfer during redox cycling of PEDOT/MnO2 composites were evaluated. It was found that during the redox cycling of PEDOT/MnO2 composite films with various MnO2 content, the oppositely directed fluxes of counterions (anions and cations) occur, resulting in a change of the slope of linear parts of the Δf–E plots with changing the mass fraction of MnO2 in the composite film.Rectangular shape of cyclic voltammograms of PEDOT/MnO2 composites with different loadings of manganese dioxide was observed, which is characteristic of the pseudocapacitive behavior of the composite material. Specific capacity values of PEDOT/MnO2 composites obtained from cyclic voltammograms were about 169 F g?1. The specific capacity, related to the contribution of manganese dioxide component, was about 240 F g?1. 相似文献
7.
The sorption of Cd(II) from aqueous solution on MnO2 was investigated under ambient conditions. Experiments were carried out as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid and temperature. The results indicated that the sorption of Cd(II) was strongly dependent on pH and ionic strength. At low pH, the sorption of Cd(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on MnO2 surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (ΔG 0, ΔS 0, ΔH 0) calculated from the temperature dependent sorption isotherms suggested that the sorption of Cd(II) on MnO2 was an spontaneous and endothermic process. 相似文献
8.
A thin film of δ‐type MnO2 grown cathodically has been investigated with respect to the ability toward anodic decomposition of H2O2 and durability. With polarization at less positive potentials than +0.4 V vs. Ag/AgCl, the film was dissolved exclusively as a result of reduction of Mn4+ sites in the oxide by H2O2 to soluble Mn2+. At +0.9 V, MnO2 remained unchanged and decomposed H2O2 in solution. At +0.8 V, the film was once dissolved in the initial stage; however, it was self‐healed via reoxidation of the liberated Mn2+ ions. Amperometric flow‐injection analysis of H2O2 was carried out with the δ‐MnO2 film. 相似文献
9.
Lipeng Zhang Hui Zhang Zhiwei Ge Xianjin Yu 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):537-546
The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions.
The removal of 60Co(II) from wastewaters by MnO2 was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and
humic substances under ambient conditions. The results indicated that the sorption of 60Co(II) on MnO2 was strongly dependent on pH and ionic strength. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on MnO2 surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA/FA enhances
60Co(II) sorption at low pH values, whereas reduces 60Co(II) sorption at high pH values. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 60Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters (ΔH
0, ΔS
0 and ΔG
0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on MnO2 was endothermic and spontaneous. 相似文献
10.
The inhibition mechanism of pitting corrosion of natural oxide film-covered pure aluminum by NO−
3 and SO2−
4 ions has been examined in 0.1 M NaCl solution using potentiodynamic polarization experiments, a.c. impedance spectroscopy,
Auger electron spectroscopy and a combination of the potentiostatic current transient method and optical microscopy. It was
found that NO−
3 ions can be incorporated into the natural oxide film on pure aluminum at open-circuit potential, but the incorporation of
SO2−
4 ions into the film hardly occurs. The incorporation of NO−
3 ions lowered the pitting susceptibility of pure aluminum in 0.1 M NaCl solution. Based upon the experimental results, it
is suggested that the pitting corrosion inhibition mechanism by anions can be classified into two different groups: inhibition
by competitive adsorption of anions (SO2−
4) with Cl− ions and inhibition by the incorporation of anions (NO−
3) into the film rather than competitive adsorption. Both cases may impede the incorporation of Cl− ions into the film, thus inhibiting pitting corrosion of natural oxide film-covered pure aluminum in chloride solutions.
Received: 16 October 1998 / Accepted: 6 January 1999 相似文献
11.
Sorption properties of oxides IX: Effect of anions on the sorption of uranium (VI) on hydrous oxides
Effect of anions such as nitrate, chloride, sulphate and carbonate on the sorption of U(VI), from aqueous solutions on hydrous
oxides of Ti(IV), Ce(IV) Zr(IV) and Th(IV) has been studied. The sorption of U(VI) is markedly reduced in the presence of
anions, like carbonate, whichform strong complexes with UO
2
2
+ in solution. The results are explained in terms of a competition for free UO
2
2
+ between surface hydroxyl groups and ligands (anions) present in solution. The sorption of U(VI) on these hydrous oxides was
also studied from a bicarbonatecarbonate mixture. Sorption was less under conditions when tricarbonate complex of U(VI) was
formed, but increased at higher pH values (>9), presumably due to the formation and sorption of hydroxo complexes of U(VI). 相似文献
12.
Kuppukkannu Ramalingam Thiyagarajan Kamatchi Pullarkat A. Sumod 《Transition Metal Chemistry》2006,31(4):429-433
Birnessite type layered MnO6 oxides with increased crystallinity were synthesized from six carbohydrates and three dihydric phenols viz., dextrose, starch, fructose, galactose, maltose, lactose, catechol, resorcinol, quinol and KMnO4 through the formation of a sol–gel. All of the MnO6 oxides were characterized by powder XRD. The strong signal at 2θ ~ 12° corresponding to 7.4 Å refers to the Mn–Mn distance between the adjacent layers. The interlayer volume is dispersed with K+ ions and H2O molecules. The presence of interlayer K+ ions is indicated by a signal at 25°, corresponding to a distance of 3.5 Å. IR spectra of the oxides show signature bands at ca. 500 cm?1 due to the stretching modes occurring for MnO6 entity. A broad band observed at ca. 3300 cm?1 is due to interlayer water molecules. Thermal analysis indicated three stage decomposition with the formation of MnO2 at ca. 600 °C through the intermediate formation of Mn(OH) n . The MnO6 exhibited a remarkable CO2 scrubbing ability, which has also been investigated. 相似文献
13.
Nathalie A. Wall Yoshitaka Minai 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):221-225
The remediation of technetium-99 (99Tc) at contaminated sites remains a major challenge, as Tc high solubility and anionic nature under oxic conditions lead to high contaminant mobility. Hydrotalcite, a form of anionic clay, can strongly retain anions, especially upon mineral calcination. However, naturally occurring humic acids can also sorb onto hydrotalcite, therefore competing with TcO4 ? for sorption sites. This work explores the ability of hydrotalcite to retain TcO4 ? in presence of humic substances to evaluate the efficacy of hydrotalcite for Tc remediation in natural environment. Results show that calcined hydrotalcite can immobilize TcO4 ?, while the presence of 23 ppm humic acids has little influence on TcO4 ? uptake. However, additional monatomic and polyatomic anions in solution can compete with TcO4 ? for sorption sites on hydrotalcite. 相似文献
14.
《Electroanalysis》2005,17(19):1746-1754
Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb)2 and Hg(Npdntb)2 as new carriers for iodide‐selective electrodes by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7×10?7 to 0.1 M and 1×10?6 to 0.1 M, with slopes of 59.6±0.8 and 58.9±0.9 mV per decade of iodide concentration and detection limit of 3×10?7 M and 7×10?7 for Hg(Npdntb)2 and Hg(Nmpntb)2, respectively, over a wide pH range of 3–11. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations. 相似文献
15.
Montree Sawangphruk Supree Pinitsoontorn Jumras Limtrakul 《Journal of Solid State Electrochemistry》2012,16(8):2623-2629
Ag-doped MnO2 pseudocapacitor electrodes with dendrite and foam-like structures were successfully produced for the first time using an electrodeposition method employing structure-directing agents, i.e., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) acting through micelle formation at solid–liquid interfaces. Doping silver with MnO2 enhanced their electronic conductance. Controlling pseudocapacitor electrode morphologies with surfactants accelerated ion transport. The specific capacitance values of the Ag-doped MnO2 films produced with SDS and CTAB, measured in 0.5?M Na2SO4 at a scan rate of 5?mV?s?1 were 551 and 557?F?g?1, respectively. These values are about 2.7-fold higher than that of the pure MnO2 film and about 1.4-fold higher than that of the Ag-doped MnO2 film made without using surfactants. 相似文献
16.
Shoji Yamanaka Koichi Yamasaka Makoto Hattori 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(1-2):297-304
New kinds of organic derivatives of layer structured -zirconium phosphate Zr(HPO4)2·2H2O are prepared by the exchange of the interlayer phosphate groups with phosphoric ester groups having oxyethylene chains, CH3–(OCH2CH2)n–OPO3
2– (n=1–3). Half of the interlayer phosphate groups are exchanged topochemically, the oxyethylene chains being grafted onto the phosphate layers through the ester bonds in the resulting derivatives. The derivatives behave like crown ethers, and form complexes with alkali salts of soft base anions such as SCN– and I–. Alkali salts of hard base anions such as Br– and NO3
– do not form complexes with the derivatives. The alkali iodide complexes of the organic derivatives can be used for the halogen exchange reaction. n-Butyl bromide is converted into n-butyl iodide in the presence of the alkali iodide complexes. The reactivities for the halogen exchange reaction increase with the number of the oxyethylene units. 相似文献
17.
An electrochemical quartz crystal microbalance was employed to monitor directly the growth of vanadium hexacyanoferrate (VHF) films on platinum substrates during electrodeposition and interfacial coagulation in the solution containing sulfuric acid electrolyte, vanadium(IV) and hexacyanoferrate(III). Mass changes of the gold/crystal working electrode were correlated with cyclic voltammetry data. Effects of cations (NH4+, Li+, Na+ and K+), anions (SO42− and NO3−) and solvent during redox reactions of the films were studied. The results show that cations were incorporated into the film during reduction and expelled from the film during oxidation. Solvent also participates in VHF electrochemistry, and its role cannot be neglected. Anions play no role in VHF electrochemistry. 相似文献
18.
Preparation and characterization of polyaniline/manganese dioxide composites via oxidative polymerization: Effect of acids 总被引:1,自引:0,他引:1
Ali H. Gemeay Ikhlas A. Mansour Rehab G. El-Sharkawy Ahmed B. Zaki 《European Polymer Journal》2005,41(11):2575-2583
Polyaniline/manganese dioxide (PANI/MnO2) composites have been chemically prepared by oxidative polymerization of aniline in acidic medium containing MnO2 as an oxidant. The acids used were; H2SO4, HNO3, HCl, and H3PO4 The prepared composites were characterized by SEM, elemental analysis, FT-IR, XRD, TGA, and magnetic susceptibility. XRD measurements of the composites revealed that the crystal structure of incorporated MnO2 undergone a distortion and converted into amorphous. Thus, the XRD pattern of PANI was predominate. The degree of crystallinity of the prepared composites is depended on the type of compensated acid anions and has the order; . This order is agrees with the order of crystallographic radii and the shape of the corresponding acid anions. From the value of point zero charge of MnO2 (pzc at pH ≈7.5) and FT-IR spectra, it was concluded that adsorbed acids anions on the oxide surface works as the charge compensator for positively charge PANI in the formation of PANI/MnO2. The content of PANI in the composite was depended on the type of acid used. Thermogravimetric study exhibited that the composite with low content of PANI has a higher thermal stability. Magnetic susceptibility measurements revealed that the composites has a diamagnetic properties. A schematic composition of the composites has been suggested. 相似文献
19.
O. B. Belskaya T. I. Gulyaeva N. N. Leont’eva V. I. Zaikovskii T. V. Larina T. V. Kireeva V. P. Doronin V. A. Likholobov 《Kinetics and Catalysis》2011,52(6):876-885
The interaction of aqueous H2PtCl6 solutions with hydrotalcite-type aluminum-magnesium hydroxides differing in the nature of their interlayer anion is reported.
In the case of CO32− as the interlayer anion, the introduction of the platinum(IV) chloro complex does exerts no significant effect on the structural
properties of the support, on its thermal decomposition dynamics, and on the textural characteristics of the resulting oxide
phase. The binding of the platinum complexes to “activated hydrotalcite” with interlayer OH− anions increases the interplanar spacing and enhances the thermal stability of the layered structure. This is accompanied
by marked changes in textural characteristics of the material, leading to the formation of a nearly monodisperse mixed oxide
phase. In the Pt/MgAlO
x
samples obtained by reductive treatment, a considerable proportion of platinum is in the form of planar particles, and this
corroborates the hypothesis that the metal complex at the sorption stage is mainly localized in the interlayer space of this
support. Platinum binds to the support as chloro complexes via rapid anion exchange, and these bound platinum species are
characterized by a higher reduction temperature. 相似文献
20.
S. J. Ahmadi N. Akbari Z. Shiri-Yekta M. H. Mashhadizadeh A. Pourmatin 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1701-1707
Hydrous, amorphous MnO2–ZrO2 composite was prepared as a new inorganic composite material under various conditions for removal of Sr2+ ion from aqueous solutions. The physico-chemical characterization was carried out by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy and thermogravimetry. The maximum sorption capacity for synthesized composite was evaluated as 1.5 meq/g sorbent and batch experiments were carried out as a function of contact time, aqueous phase pH, temperature and initial metal ions concentration of adsorptive solution. The results indicated that under optimal conditions, Sr2+ ions could be efficiently removed using MnO2–ZrO2 composite from aqueous solutions when pH > 5. The equilibrium isotherms were determined and the sorption data were successfully modeled using Langmuir model. Kinetics of the process was studied by considering a pseudo second-order model. This model predicted chemisorption as the adsorption mechanism. The results of thermodynamic investigation reveal that the adsorption process of the studied ion is entropy driven. 相似文献