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1.
Polarization studies have been carried out to determine the influence of diisobutyldithiophosphinate (DIBDTPI) on the dissolution of silver in cyanide solutions at pH 11. DIBDTPI was found to inhibit dissolution at concentrations similar to those used when this compound is applied as a flotation collector. The inhibition efficiency in 10–2 mol dm–3 CN– was found to increase with increase in DIBDTPI concentration in the range 10–6–10–4 mol dm–3, and with increase in time of exposure of the silver to the DIBDTPI solution. The inhibition efficiency found for 10–4 mol dm–3 DIBDTPI in quiescent 10–2 mol dm–3 CN– solution at 23 °C was 64.6% and 95.0% for exposure times of 10 min and 2 h, respectively. These values are significantly less than those found previously for 2-mercaptobenzothiazole under the same conditions. Surface enhanced Raman spectroscopy showed that inhibition was associated with adsorption of DIBDTPI displacing cyanide from the silver surface. Voltammetry at 0.5 mV s–1 indicated that adsorption of DIBDTPI involves charge transfer. 相似文献
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The interaction of the sulfide mineral flotation collector, 2-mercaptobenzothiazole, with silver, copper and gold surfaces has been investigated by surface enhanced Raman scattering (SERS) spectroscopy. 2-mercaptobenzothiazole, the copper, silver and gold compounds of this species, and the dithiolate, 2,2-dithiobis(benzothiazole) were characterised by 13C NMR and Raman spectroscopy to provide a basis for identifying surface species. SERS investigations showed that, at pH 4.6 where the solution species is in the protonated form, and at 9.2, where it is present as the ion, adsorption on each metal occurs over a wide potential range. Attachment of the organic compound occurs through bonding between the exocyclic sulfur atom and metal atoms in the surface. X-ray photoelectron spectroscopy confirmed that the adsorbed layer was of monolayer thickness. Adsorption of the protonated 2-mercaptobenzothiazole occurs on copper at pH 4.6 at potentials below that at which charge transfer adsorption commences. 相似文献
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D. Kaušpėdienė A. Gefenienė R. Ragauskas V. Pakštas 《Chemical Engineering Communications》2017,204(11):1258-1269
Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO3 were used for the removal of CN– and Ag–CN complex from model wastewater. The formed Ag0 centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag0 participating in CN– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The KF values for the CN– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN–, and plain, removing the rest of Ag–CN. 相似文献
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The efficiency of benzotriazole as inhibiting agent for the corrosion of cobalt was probed at pH ranging from 8.3 to 10.2 in a sodium bicarbonate solution, chosen to simulate mild natural environments. From electrochemical, Raman spectroscopy, atomic force microscopy and ellipsometry experiments, we have demonstrated that benzotriazole markedly affects the electrodissolution reactions, which become modeled by the formation of a [Co(II)(BTA)2·H2O]n film according to two different mechanisms. Surface-enhanced Raman spectroscopy has shown that the polarization of a cobalt electrode at cathodic potentials with respect to its potential of zero charge allows a mechanism of specific adsorption of the neutral form of benzotriazole to take place through a suspected metal-to-molecule electron transfer and which follows Frumkin's adsorption isotherms. At the onset of the anodic dissolution, some experimental evidence suggests that these adsorbed neutral benzotriazole molecules deprotonate to yield a very thin [Co(II)(BTA)2·H2O]n polymer-like and water-insoluble protective film, responsible for the inhibition of active dissolution processes occurring at slightly more anodic potentials. In the anodic dissolution region, deprotonated benzotriazole species present in the bulk solution favors the formation of a multilayered [Co(II)(BTA)2·H2O]n film, which also contributes to the inhibition of any further cobalt dissolution usually observed at higher electrode potentials. 相似文献
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Sarla Malhotra M Pandit JC Kapoor DK Tyagi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):13-19
Photo‐oxidation of cyanide was studied in aqueous solution using a low‐pressure ultra‐violet (UV) lamp along with H2O2 as an oxidant. It was observed that by UV alone, cyanide degradation was slow but when H2O2 was used with UV, the degradation rate became faster and complete degradation occurred in 40 min. The rate of degradation increased as the lamp wattage was increased. It was also observed that cyanide oxidation is dependent on initial H2O2 concentration and the optimum dose of H2O2 was found to be 35.3 mmol dm?3. Photo‐oxidation reactions were carried out at alkaline pH values (10–11) as at acidic pH values, cyanide ions form highly toxic HCN gas which is volatile and difficult to oxidise. By the UV/H2O2 process, using a 25 W low‐pressure UV lamp and at alkaline pH of 10.5 with an H2O2 dose of 35.3 mmol dm?3, cyanide (100 mg dm?3) was completely degraded in 40 min when air was bubbled through the reactor, but when pure oxygen was bubbled the time reduced to 25 min. The cyanide degradation reaction pathway has been established. It was found that cyanide was first oxidised to cyanate and later the cyanate was oxidised to carbon dioxide and nitrogen. The kinetics of cyanide oxidation were found to be pseudo‐first order and the rate constant estimated to be 9.9 × 10?2min?1 at 40 °C. The power required for complete degradation of 1 kg of cyanide was found to be 167 kWh (kilowatt hour). Copyright © 2004 Society of Chemical Industry 相似文献
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M. Prabakaran P. Durainatarajan V. Periasamy 《Journal of Adhesion Science and Technology》2016,30(14):1487-1509
The corrosion inhibition effect of carbon steel in aqueous solution was using a synergistic mixture of an environmentally friendly inhibitor system phosphoserine (PS) and Zn2+ using gravimetric studies, potentiodynamic polarization, and electrochemical impedance studies. Potentiodynamic polarization studies showed that the inhibitor system is a mixed type inhibitor. Electrochemical impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the aqueous solution. X-ray photoelectron spectroscopic analysis of the protective film exhibited the presence of the elements viz., iron, phosphorus, nitrogen, oxygen, carbon, and zinc. The chemical shifts in the binding energies of these elements inferred that the surface film is composed of oxides/hydroxides of iron, Zn(OH)2, and [Fe(II)/(III)-Zn(II)-PS] complex. Further, the surface examination techniques viz., FTIR, SEM, and AFM studies confirm the formation of an adsorbed protective film on the carbon steel surface. Based on the results obtained, a suitable mechanism of corrosion inhibition is presented. 相似文献
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M.A. Pasquale S.L. Marchiano A.E. Bolzán A.J. Arvia 《Journal of Applied Electrochemistry》2003,33(5):431-441
The influence of agarose on the electrochemical behaviour of the interfaces silver/aqueous agarose + 0.014 M silver sulfate + 0.5 M sodium sulfate + 0.01 M sulfuric acid and platinum/aqueous agarose + 0.5 M sulfuric acid, at 298 K, was studied. Freshly prepared and aged agarose-containing solutions in the range of agarose concentration 0.01 c
aga 0.5% w/v were used. Viscosity, open circuit potential, solid sample infrared spectra and conventional voltammetric measurements were performed. The electrooxidation of adsorbates produced from both the homogeneous and heterogeneous decomposition of agarose-containing solutions on platinum was investigated. Results are discussed in terms of the structure and interactions of agarose molecules in sols and gels. The electrooxidation of adsorbed residues can be explained within the complex reaction pathway for the electrooxidation of saccharides previously discussed in the literature. 相似文献
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S. Vilchis-Carbajal I. González G.T. Lapidus 《Journal of Applied Electrochemistry》2000,30(2):217-229
The half-reactions involved in gold cementation on zinc powder from low concentration alkaline cyanide solutions were studied in a steady state regime, employing electrodes of glassy carbon and graphite paste with zinc powder. The effects of pH, cyanide and initial gold concentrations were investigated using various electrochemical techniques. The results were used to determine the controlling step of the cementation at low cyanide concentration and to interpret the influence of the variables on this process. Mixed potentials and associated currents were determined from the Evans' diagrams constructed using sampled current–potentials curves from chronoamperometric results for half redox reactions. These values do not adequately describe the global cementation reaction because gold reduction in low cyanide concentration solutions is greatly influenced by a strong contribution from adsorptive processes. This behaviour is different from that found by other authors for concentrated gold and cyanide solutions, where the process is controlled by the complex ion diffusion (Au(CN)2
–). The strong component of adsorption found in the present work does not permit the determination, using the Evans' diagrams, of the cementation velocity. Direct monitoring of the mixed potential was proposed, employing an electrode made of zinc powder in carbon paste submerged in a gold cyanide solution. The results of these experiments at low cyanide concentrations show that zinc oxidation is controlled by the formation of different passivating layers, the nature of which depended on the pH of the solution, and that the gold reduction reaction is strongly influenced by adsorption phenomena. 相似文献
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Gintaras Baltrūnas 《Electrochimica acta》2003,48(24):3659-3664
The electrode's surface inhomogeneity was taken into account studying the mechanism of process. The effect of CN− adsorption and partial surface coverage was investigated by electrochemical fast Fourier transform (FFT) impedance spectroscopy (0.03-3900 Hz). The isopotential solutions (E0=−0.350 V) as well as solutions containing constant silver cyanide complex concentration (0.05 M) and different free cyanide ion concentrations (from 0.01 to 1.0 M) were studied. The exchange current density, re-calculated for only active area, gives electrochemical reaction order (RCN=1.8 for α=0.5, and RCN=2 for α=0.6) which is independent from CN− concentration and from the composition of complexes prevailing in the bulk of electrolyte. The value of RCN close to 2, obtained in a series of isopotential solutions confirms that in all cases the complex ions Ag(CN)2− take direct part in the charge transfer step. 相似文献
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The corrosion of single crystal pure iron in 3.5% NaCl solutions and its inhibition by 3-amino-5-mercapto-1,2,4-triazole (AMTA) have been studied using in situ and ex situ Raman spectroscopy, cyclic voltammetry (CV), open-circuit potential (OCP), potentiodynamic polarization (PDP), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. CV experiments indicated that the iron electrode in the chloride solution alone showed an anodic peak at ∼−650 mV after the 5th cycle shifted to ∼−610 mV after the 20th cycle; another cathodic peak appeared at ∼−990 mV. In the presence of 1.0 mM AMTA, these two peaks shifted to ∼550 and −1050 mV, respectively. OCP, PDP, CA and EIS revealed that the presence of AMTA and the increase of its concentration move the corrosion potential to more positive values and decrease both the corrosion current and corrosion rate. This effect also increases with increasing the immersion time of iron electrode to 24 h in the test electrolyte. In situ and ex situ Raman investigations confirmed that the addition of AMTA molecules to the chloride solution strongly inhibits the iron corrosion through their adsorption onto the surface blocking its active sites and preventing its corrosion. 相似文献
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The adsorption and corrosion inhibition behaviour of four selected piperidine derivatives, namely piperidine (pip), 2-methylpiperidine
(2mp), 3-methylpiperidine (3mp), and 4-methylpiperidine (4mp) at nickel in 1.0 M HNO3 solution were studied computationally by the molecular dynamics simulation and quantum chemical calculations and electrochemically
by Tafel and impedance methods. The results indicate a strong dependence of the inhibition performance on the nature of the
metal surface, in addition to the structural effects of piperidines. Inhibition is accomplished by adsorption of piperidines
on the metal surface without detectable changes in the chemistry of corrosion. Adsorption is predominantly chemisorptive in
the active region and by hydrogen bond formation in the passive region. The potential of zero charge (PZC) of the nickel electrode
was determined in 1.0 M HNO3 solutions in the absence and presence of 10−2 M 2mp, and the electrostatic (physical) adsorption was discussed. The inhibition efficiency of these compounds increases
in the order: 4mp > 3mp > 2mp > pip. Molecular simulation studies were applied to optimize the adsorption structures of piperidine
derivatives. The nickel/inhibitor/solvent interfaces were simulated and the charges on the inhibitor molecules as well as
their structural parameters were calculated in the presence of solvent effects. Quantum chemical calculations based on the
ab initio method were performed to determine the relationship between the molecular structure of piperidines and their inhibition
efficiency. Results obtained from Tafel and impedance methods are in good agreement and confirm theoretical studies. 相似文献
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利用衰减全反射红外光谱(ATR-IR)和二维相关红外技术研究2, 6-二甲氧基苯酚(2, 6-DMP)在1-丁基-3-甲基咪唑四氟硼酸盐([C4mim]BF4)水溶液(离子液体摩尔分数xIL=1.0~0.02)中的溶解行为。随着水量增大, 2, 6-DMP溶解度先增大而后急剧减小, 对应的xIL阈值为0.1。2, 6-DMP与[C4mim]BF4之间存在强相互作用, 2, 6-DMP上的甲氧基是重要作用位点之一;当少量的水加入[C4mim]BF4(xIL=0.1~1.0), 致密的离子簇结构被解离, 2, 6-DMP容易与[C4mim]BF4作用, 溶解度增大;随着大量水加入(0.02IL<0.1), 离子簇完全解离为大分子水簇包围的离子对, 憎水的2, 6-DMP与[C4mim]BF4作用困难, 溶解度减小。这种由于水量改变引起的[C4mim]BF4水溶液微观结构变化影响2, 6-DMP溶解行为。 相似文献
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Poly vinyl alcohol (PVA) incorporated with different weight percent of Silver nanoparticles (Ag NPs) were prepared. The enhancement factors for each band in the Raman spectra were calculated and the degree of enhancement were found to be increased as the percent of Ag NPs increases up to 0.3%, and thereafter it decreases. Some bands were red shifted while others were blue shifted. The overtones FTIR bands and photoacoustic spectra were recorded and show the same behavior as those bands. The X‐ray diffraction pattern and Raman and photoacoustic spectra showed that PVA has a high degree of crystallinity. The UV–vis spectra of the same samples were red shifted and increase in their intensities up to 0.3% Ag NPs, thereafter the band intensities of the peak corresponding to Ag NPs were diminished. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3608–3614, 2006 相似文献
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G. Petkova E. Sokolova S. Raicheva P. Ivanov 《Journal of Applied Electrochemistry》1998,28(10):1067-1071
The inhibition effect of gamma-pyrodiphenone (PD) on copper corrosion in near neutral sulphate solutions was investigated. Weight loss and polarization measurements show a high inhibition efficiency (>96%) of PD on copper corrosion at extremely low concentrations. PD suppresses active copper dissolution and oxygen reduction. The potentiodynamic cathodic reduction measurements showed an inhibition of oxide formation and stabilization of the Cu2O oxide in the presence of PD. XPS measurements suggested that the high inhibition effect of PD on copper corrosion is due to the adsorption of PD molecules, as a first stage, and the formation of a film with a polymer-like structure by coordination of PD with Cu2O on prolonged exposure. 相似文献
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Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques. 相似文献