共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Yu. Bek 《Russian Journal of Electrochemistry》2001,37(4):387-393
Effective order of the gold dissolution reaction by cyanide ions, p, transfer coefficient , and exchange current i
0are measured at constant coverages of the gold surface by lead adatoms, . Constancy of is ensured by maintaining the time period t, during which the electrode is in contact with solution after the renewal of its surface and before taking measurements, constant. Solutions under study contain (0.5–2) × 10–5M lead acetate, 0.05–0.2 M KCN, 0.1 M KOH, and 0.01 M KAu(CN)2. With increasing t, quantities p, , and i
0increase from, respectively, 0.17, 0.1, and 10–5A dm–2(in 0.05 M KCN) to p 1.2, 0.45, and i
0 10–4A dm–2. The increase in psuggests that the limiting stage alters in the presence of lead adatoms: in addition to adsorbed cyanide ions, as is the case with pure alkali–cyanide solutions, it involves cyanide ions located outside the adsorption layer. A feasible mechanism for the acceleration of gold dissolution by lead adatoms is offered. 相似文献
2.
R. Yu. Bek 《Russian Journal of Electrochemistry》2003,39(10):1036-1041
An admixture of mercury ions accelerates dissolution of gold at negative (in the hydrogen scale) potentials and hinders it at positive potentials. In contradistinction to a similar effect exerted by admixtures of thallium, bismuth, and lead ions, the influence of mercury ions, all other conditions being equal, manifests itself at much longer times of contact between gold and solution. This difference is due to a low rate of the act of adsorption (discharge) of mercury ions. The rate increases at more negative potentials, and at E –1.2 V (NHE) the act accelerates to such an extent that looses the limiting role, which passes to the stage of supply of mercury ions to the electrode, as with solutions containing thallium, bismuth, and lead. Comparing these results with earlier data on the adsorption of cyanide ions on gold shows that the discharge of the Hg(CN)2-
4 anions stops limiting the formation of a layer of mercury atoms when the adsorption of cyanide ions turns insignificant. 相似文献
3.
The gold dissolution rate iin solutions containing 0.1 M KOH, 0.1 M KCN, and 2.5 × 10–7to 1.5 × 10–5M TlNO3is studied as a function of potential Eof the electrode whose surface is renewed prior to each experiment, the TlNO3concentration c, and the time tof the electrode contact with solution. At cexceeding 0.5 × 10–5M and t 0, the rate is 1.5–2 times that at c= 0. Initial portions of ivs. tcurves in the absence and presence of TlNO3coincide only at cbelow 10–6M. Potentiostatic and potentiodynamic measurements show that, at positive E, only small coverages of the electrode surface with thallium are obtained, which make no impact on iat E< 0 and heavily increase it at 0 < E< 0.3 V. The discovered effects are attributed to the formation, during the adsorption of oxidized thallium forms, of dipoles comprising thallium adions and gold atoms. Presumably, the dipoles face the gold with their negative ends and make the potential of zero free charge more negative. 相似文献
4.
Igor V. Mironov Danila B. Kal’nyi Vasiliy V. Kokovkin 《Journal of solution chemistry》2017,46(4):989-1003
Processes involving gold(I) complexes were studied in sulfite–thiourea (TU) solutions. It is shown that at pH >5 the complex [\( {\text{AuTU}}_{2}^{ + } \)] undergoes irreversible decomposition followed by deprotonation and formation of a solid phase. From the data of pH in mixed solutions, the equilibrium constants were evaluated: \( {\text{Au}}({\text{SO}}_{3} )_{2}^{3 - } + i{\text{TU}} \rightleftharpoons {\text{Au}}({\text{SO}}_{3} )_{2 - i} {\text{TU}}_{i}^{2i - 3} + i{\text{SO}}_{3}^{2 - } \), log10 β 1 = ?1.2, log10 β 2 = ?3.6. Some aspects of the anodic dissolution of gold in mixed sulfite–thiourea solutions are considered. With the help of the carbonate buffer system the change of the anodic current density j a was studied at high pH; j a (pH) has a maximum at pH 11.6–11.9 for E a = 0.3–0.6 V (vs. NHE). At pH > 12.0, the j a values decrease sharply. Possible mechanisms of anodic gold dissolution, as well as the role of sulfite, are discussed. 相似文献
5.
The possibility of determining kinetic parameters of the gold electrodeposition in the presence of thallium adatoms is considered. The coverage of the electrode surface by thallium adatoms is monitored. The steady-state values of potential used correspond to current densities i that are directly proportional to the concentration of thallium ions in solution. The procedure is based on the assumption that the rate of incorporation of adatoms is proportional to the product i. With increasing to 0.25, the exchange current and transfer coefficient increase from 5 × 10–5 A cm–2 and 0.23 in pure solutions to1.5 × 10–4 A cm2 and 0.6 at = 0.25–0.3, whereas the reaction order by cyanide ions remains practically invariant with increasing . Variations in the kinetic parameters with are compared to similar measurements obtained earlier for the anodic process. These may be made consistent by assuming that mechanisms of cathodic and anodic reactions differ in pure solutions and are identical in the presence of catalytically active adatoms. An explanation to the above regularities is given. 相似文献
6.
ResearchershavestudiedtheeffectofCI-onthestructureandpropertiesofthecorrosionproductsinchloridesolutionscontainingH,S"'.IthasbeenfoundthattherearenocorrosioneffectsonironsurfaceswhicharesubmergedinconcentratedacidicchloridesolutionswithlowHZSlevel.Inthepast,theinteractionbetweentheCI-ionandFehasnotbeenstudiedcompletelyandintensively.TheanodicreactionofironinacidicsolutionscontainingHZSwastheironoxidationcatalyzedbyHS-3.WhenCI-ispresentinHZS-containingacidicsolutions,theeffectofCI-onir… 相似文献
7.
Selective Anodic Dissolution of Ag–Zn Alloys in the Eutectic Melt of Alkali Metal Chlorides at 300°С
Russian Journal of Electrochemistry - The peculiarities of electrochemical dealloying of two homogeneous Ag–Zn alloys in the (LiCl)0.57(CsCl)0.26(KCl)0.17 melt are studied. The zinc content... 相似文献
8.
Semencha A. V. Strekalovskaya D. A. Baturova L. P. 《Russian Journal of Applied Chemistry》2021,94(11):1483-1488
Russian Journal of Applied Chemistry - The anodic behavior of Ti–Nb alloys in a deaerated 1 М H2SO4 solution was studied, and the effect of cathodic pretreatment of the alloys on the... 相似文献
9.
G. N. Pirogova I. M. Kosareva N. N. Popova I. I. Byvsheva A. K. Pikaev 《High Energy Chemistry》2002,36(4):209-212
Radiolytic gas formation was measured in aqueous alkali–nitrate and alkali–nitrate–aluminate solutions simulating liquid intermediate-level wastes. The radiation-chemical yields of the gas mixture and its individual components depending on solution composition and irradiation temperature (up to 60°C) were determined. It was noted that oxygen was formed in comparatively high yields (up to 0.4 and 0.6 molecule/100 eV in alkali–nitrate–aluminate solutions at 30 and 60°C, respectively). This fact was explained by the decomposition of hydrogen peroxide, which is formed as a primary product of water radiolysis and in the combination of O– radical ions, and by the catalytic effect of aluminate ions. 相似文献
10.
Yurkinskii V. P. Sokolova N. V. Popov V. A. 《Russian Journal of Applied Chemistry》2001,74(3):427-429
Complex formation of lead(II) was studied, and the solubility of -PbO was determined by potentiometric titration in solutions containing sodium hydroxide (0.3-4 M) and a series of mono- and polyhydric alcohols. A correlation between the lead monoxide solubility and Pb(II) complex formation function was considered. 相似文献
11.
Wenjing Wang Nitya Sai Reddy Satyavolu Zhenkun Wu Prof. Dr. Jian-Rong Zhang Prof. Dr. Jun-Jie Zhu Prof. Dr. Yi Lu 《Angewandte Chemie (International ed. in English)》2017,56(24):6798-6802
DNAzymes have enjoyed success as metal ion sensors outside cells. Their susceptibility to metal-dependent cleavage during delivery into cells has limited their intracellular applications. To overcome this limitation, a near-infrared (NIR) photothermal activation method is presented for controlling DNAzyme activity in living cells. The system consists of a three-stranded DNAzyme precursor (TSDP), the hybridization of which prevents the DNAzyme from being active. After conjugating the TSDP onto gold nanoshells and upon NIR illumination, the increased temperature dehybridizes the TSDP to release the active DNAzyme, which then carries out metal-ion-dependent cleavage, resulting in releasing the cleaved product containing a fluorophore. Using this construct, detecting Zn2+ in living HeLa cells is demonstrated. This method has expanded the DNAzyme versatility for detecting metal ions in biological systems under NIR light that exhibits lower phototoxicity and higher tissue penetration ability. 相似文献
12.
Four wood pulps and a microcrystalline cellulose were dissolved in a NaOH 8%–water solution. Insoluble fractions and clear
solution fractions were isolated by centrifugation and were observed by optical microscopy and transmission electron microscopy.
Molecular weight distribution, carbohydrate composition and cellulose II content were measured. The dissolution of wood cellulose
fibres in NaOH 8%–water solutions occurs by successive dismantlement and fragmentation steps governed by the swelling and
the shearing of the original structure. The cellulose from insoluble and clear solution fractions is in both case converted
in cellulose II and the insoluble fractions contain embedded mannans. Besides, the molecular weight distributions of cellulose
from insoluble and clear solution fractions reveal the existence of heterogeneities in dissolution capacity of the cellulose
chains, independent to the degree of polymerization, which are related to the chemical environment of the chains in the fibre
structure. 相似文献
13.
Pei Zhu Zhi-cheng Xu Lei Zhang Sui Zhao 《Journal of Dispersion Science and Technology》2016,37(6):820-829
The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C8PO6EO3S (6-3) and C8PO6EO6S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface. 相似文献
14.
Ekilik V. V. Svyataya M. N. Berezhnaya A. G. 《Russian Journal of Electrochemistry》2003,39(8):857-862
Acridine derivatives as inhibitors of diffusion- and diffusion–kinetic-controlled dissolution of -brass are studied. Inhibition coefficients of the dissolution and its steps correlate with parameters of a standard reaction series and wavelengths of the longest-wave absorption band of the electronic spectrum. 相似文献
15.
LI Xiao-kun WANG Zhen-xin 《高等学校化学研究》2010,26(2):194-197
The authors presented a simple colorimetric assay for the detection of toxic heavy metal lead(Ⅱ) ion(Pb2+).Pentapeptide,cysteine-alanine-leacine-asparagine-asparagine(CALNN),functionalized gold nanoparticles(GNPs) were aggregated in the presence of the divalent metal ion in solution by an ion-templated chelation process,which caused an easily measurable change in the absorption spectrum of the particles.Typically,mono-dispersing GNPs exhibit an absorption band at 522 nm,corresponding to a red color solution,while aggregated GNPs have it at longer wavelengths,corresponding to a purple or blue color solution.The chelation/aggregation process is reversible via the addition of a strong metal ion chelator such as EDTA.Highly selective and sensitive detection of Pb2+ in aqueous solution is thus provided.A detection limit of 0.1 μmol/L of Pb2+ was demonstrated. 相似文献
16.
V. P. Gordeeva G. A. Kochelaeva G. I. Tsizin V. M. Ivanov Ya. A. Zolotov 《Journal of Analytical Chemistry》2002,57(8):688-693
A sorption–spectrometric method was developed for the determination of palladium in solutions of complex composition using cellulose filters impregnated with trioctylamine with the subsequent formation of the colored compound of palladium with 4-(2-pyridylazo)resorcinol on the filter. It was demonstrated that conditions for the preconcentration of palladium coincide with conditions for the formation of colored compounds (green and red forms of palladium complexes) in the sorbent phase. The highest selectivity is observed for the formation of the green form; in this case, the determination of palladium is not affected by the interference from large amounts of concomitant elements (macrocomponents of ores). Palladium was determined on filters by diffuse reflectance spectrometry with the calculation of chromaticity characteristics and by a test scale. The detection limits were 0.5 (green form) and 0.3 (red form) g of palladium on the filter. High precision of results of the determination of palladium (RSD < 5%) is attained in a wide range of its concentrations. 相似文献
17.
Introduction Overall exposure to lead is of public health concern because of several hazardous effects that may occur to human beings. Lead poisoning may provoke irritability, anorexia, malaise and headache. Intoxication progress may lead to attacks of abdominal pain until coma and death.1 The determination of trace lead in variety of en-vironmental samples is of great importance since lead is recognized as a cumulative poison to animals and hu-mans. There is a constant demand for improved an… 相似文献
18.
Xiaohui Xu Fu Yang Nan Wang Minghuan Shen Tingting Zhou Xiangying Wang 《Journal of Dispersion Science and Technology》2013,34(1):101-105
With the vacuum sublimation freezing‐drying and rheological techniques, the salt/alkali/surfactant effects on the solution properties and the aggregate conformations of the polymers, synthesized hydrophobically modified poly (acrylamide) (HMPAM), were investigated. The experimental methods included viscosity measurements, the photomicroscopy, scan electron microscopy, and the freeze fracture transmission electron microscopy. The variety of conformations of the ultramolecular aggregates, the hydrophobical region, and the spatial network structures resulted from the hydrophobical interaction were studied. Combined results confirmed that HMPAM could form several of interesting three‐dimensional network structures either in distilled water or NaCl solution. The results have revealed the mechanism of the salt/alkali/surfactant effects on the peculiar rheological properties of the solution. 相似文献
19.
V. I. Parfenyuk 《Journal of Structural Chemistry》2001,42(6):951-955
The ionic coefficients of the pair interionic interaction in aqueous solutions of 1–1 electrolytes at 298 K were determined from the real activity coefficients of single-charged single ions using the McMillan–Mayer formalism. Analysis of the results of calculations revealed that salt effects are stronger in the case of cations. The weakening of cation hydration (increased negative hydration) and the strengthening of anion hydration (increased positive hydration) enhance the mutual salting of cations and anions. It is shown that the structural effects of hydration produce a strong effect on the interionic interaction in solutions. 相似文献
20.
The effect of temperature on the yields of 1,2-alkanediols in the -radiolysis of the methanol(or ethanol)–formaldehyde (0.9 M) systems and on the yields of 1,2-alkanediols, carbonyl compounds, methanol, and ethanol in the -radiolysis of the 1-propanol(or 2-propanol)–formaldehyde (1 M) systems was studied over the range 373–473 K. It was found that the temperature dependence of the yields of 1,2-butanediol and 2-methyl-1,2-propanediol exhibited maximums at 423 and 373 K, respectively. 相似文献