Anodic deposition

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Anodic deposition is controlled by either fluid shear (cross-flow filtration) (48), similar to gel-polarization control, or by continual anode replacement (electrodeposited paints) (46). High fluid shear rates can cause deviations from theory when E > (49). The EUF efficiency drops rapidly... 

The cathode reaction is the reduction of water to produce hydrogen (eq. 8). The mechanism of the anodic deposition of Mn02 has been investigated (44,47). 

The separations summarised in Table 12.2 can be readily accomplished electrolytically the first is dependent upon a large difference in deposition potentials (Section 12.4), and the second upon the fact that Pb2+ can be anodically deposited as Pb02. 

Cathodic stripping voltammetry (CSV) is the mirror image of ASV It involves anodic deposition of the analyte, followed by stripping in a negative-going potential scan ... 

Two types of reactions producing a new phase can be distinguished (1) those producing a noncrystalline phase (gas bubbles liquid drops as, e.g., in the electrolytic deposition of mercury on substrates not forming amalgams), and (2) those producing a crystalline phase (cathodic metal deposition, anodic deposition of oxides or salts having low solubility). 

Hu CC, Tsou TW. Capacitive and textural characteristics of hydrous manganese oxide prepared by anodic deposition. Electrochim. Acta 2002 47 3523-3532. 

In this paper we describe the preparation of thin polymer films by surface catalysis and anodic deposition. The results indicate that both synthesis routes produce orientationally ordered films that have similar infrared spectra. It is also shown that thin ordered films of poly(thiophene) have different electrochemical behavior than the fibrous films that are electrically conducting. 

Polymer films were produced by anodic deposition by potentiostatic deposition onto a platinum electrode. Deposition was done from 1 M solutions of the monomer in 1M LiC104 in acetonitrile. The films were characterized by cyclic voltammetry and reflection infrared spectroscopy in an apparatus described elsewhere [15]. 

A reflection infrared spectrum of the anodically deposited orange-gold film is shown in Figure 2. The electrochemically deposited... 

Aniline. Aniline black is a well known polymer of aniline formed by electrophilic additionf3.41. Numerous investigators have formed poly(aniline) films by anodic deposition of Pt and other electrode materials. We have examined the interaction of aniline with clean Ni(lll) and Ni(100) surfaces in ultrahigh vacuum and found aniline to form an orientationally ordered, thermally stable polymer film. Electrochemically prepared poly(aniline) films also show the high degree of orientational ordering. 

The results suggest that there is a remarkable similarity in the structure of thin films formed by anodic deposition on a Pt electrode to those formed catalytically on Ni surfaces in ultrahigh vacuum. The... 

Barnes, I.L., Murphy, T.J., Gramlich, J.W. and Shields, W.R. (1973). Lead separation by anodic deposition and isotopic ratio mass spectrometry of microgram and smaller quantities. Analytical Chemistry 45 1881-1884. 

Markov chains theory provides a powerful tool for modeling several important processes in electrochemistry and electrochemical engineering, including electrode kinetics, anodic deposit formation and deposit dissolution processes, electrolyzer and electrochemical reactors performance and even reliability of warning devices and repair of failed cells. The way this can be done using the elegant Markov chains theory is described in lucid manner by Professor Thomas Fahidy in a concise chapter which gives to the reader only the absolutely necessary mathematics and is rich in practical examples. 

Markovian Interpretation of an Anodic Deposit Formation <-> Deposit Dissolution Process... 

Markov Chain Evolution for the Anodic Deposit Formation<->Deposit Dissolution Process. The Initial State is Purely Ionic (/> ° = 1 p2 = 0)... 

An electrochemical cell [93,94] was used to obtain an efficient anodic deposition of no carrier added F-fluoride solubilized in the target water. The radioisotope is electrochemically adsorbed on the anode (glassy carbon electrode) and can be easily dried. An opposite electrical field releases the radionuclide directly into a solution of a phase transfer catalyst in dipolar aprotic solvents. The nucleophilic fluorination can be performed simultaneously if the electrochemically and thermally induced desorption of radioactivity is done in the presence of the precursor. However, the yields remain poor (3 % in the electrochemical n.c.a [ F]fluorination of anisole). 

Only three values of log Kso are available for lepidocrocite and these are not in very good agreement. Hashimoto and Misawa (1973) measured the solubility of lepidocrocite produced by anodic deposition from Fe" solution on a platinum electrode and obtained a value for log Kso of 2.50. This agrees with the value calculated from the free energy of formation (Blesa et al., 1994). Mohr et al. (1972) quote a value of 2.72 and Lindsay (1979) gives 1.59. 

A/cm2, 90°C, 30 wt% KOH) with time during a batch experiment demonstrating in situ activation. Evidently the addition of only 10 mg/cnr of cobalt in the form of cobaltous nitrate, which is decomposed by generating soluble Co(OH)fand Co(OH)4 species, results in reduction of the anodic overpotential (+340 mV) by more than 50 mV. This is due to the anodic deposition of a thin film of electrocatalytically active cobalt spinell, C04O4, according to... 

Silver differs markedly from copper in forming few 0x3 compounds. One of these is silver oxynitratc or silvcrdl, III) nitrate which has the empirical formula AgO 145(1 03)3453, in which the average oxidation number of silver is 2.448, It is prepared by action of fluorine upon aqueous silver nitrate or is obtained as an anodic deposit by electrolysis of silver nitrate in dilute HNO3. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

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