Sulfuric acid electrolyte

Specifications for sulfuric acid vary rather widely. Exceptions include the federal specifications for "Sulfuric Acid, Technical" and "Sulfuric Acid, Electrolyte (for storage batteries)" and the Food Chemicals Codex specification for sulfuric acid, frequentiy called food-grade acid (although industrywide, "food-grade" is nonspecific). Very Httie has been done to estabUsh industry-wide analytical standards in the United States, except for development of the ASTM analytical methods, designated as E223-88 and summarized in Table 12. 

Aluminum has a low density it is a strong metal and an excellent electrical conductor. Although it is strongly reducing and therefore easily oxidized, aluminum is resistant to corrosion because its surface is passivated in air by a stable oxide film. The thickness of the oxide layer can be increased by making aluminum the anode of an electrolytic cell the result is called anodized aluminum. Dyes may be added to the dilute sulfuric acid electrolyte used in the anodizing process to produce surface layers with different colors. 

Shukla AK, Ravikumar MK, Roy A, Barman SR, Sarma DD, Arico AS, Antonucci V, Pino L, Giordano N. 1994. Electrooxidation of methanol in sulfuric-acid electrolyte on platinized-carbon electrodes with several functional-group characteristics. J Electrochem Soc 141 1517-1522. 

In comparison to electrorefining, the electrowinning process of copper, when using a copper sulfate-sulfuric acid electrolyte, presents an interesting situation. In the electro-... 

Dilute sulfuric acid Electrolytic cell slimes/sludges... 

Various plutonium materials are dissolved in acidic media and then fumed with sulfuric acid. In a 0.5 M sulfuric acid electrolyte, plutonium is reduced to Pu(III) at a platinum working electrode maintained at 0.310 V relative to a saturated calomel electrode. Plutonium (III) is oxidized to Pu(IV) at 0.670 V for the coulometric measurement. This work supports manufacturing, stock pile reduction, and pilot programs for making nuclear fuels from the stockpile. 

The use of low-grade ores with large amounts of harmful impurities results in increased accumulation of these impurities in the electrolyte. One of the most harmful is arsenic, which seriously affects the quality of the copper cathodes. Arsenic occurs in the sulfuric acid electrolyte as arsenic acid, and as such can be extracted as an adduct complex with TBP. The extraction is favored by increasing acidity and low temperature. 

Almost fifty years ago, Baranowsld et al. [70] and Baranowski and Smi-alowski [71] reported that, using sulfuric acid electrolyte and current densities <20 mA cm , Ni cathodes could be converted into nonstoichiometric NiH c(x < 1) hydride. A few years later, the nature of NiH c was established by identifying two separate phases, p and a, as for the PdH analog [69, 72]. Both p- and a-hydrides formed by electrolysis of aqueous H2SO4 at Ni the former, much more hydrogen-rich than the latter (H/Ni atom ratios of 0.8 for p and 0.03 for a), decomposes quickly with H2 evolution [73, 74]. 

The effect of antimony, germanium, and nickel ions, and the organic additives on the zinc electrowinning from sulfuric acid electrolytes was also studied by Ivanov [400]. 

In the gelled electrolyte battery, die sulfuric acid electrolyte has been immobilized by a diixolropic gel. This is made by mixing an inorganic powder such as silicon dioxide, SiCL, with the acid. Other cells use a highly absorbent separator to immobilize the electrolyte. 

The hydrogenation of heteroaromatic compounds can easily be performed at lead cathodes in sulfuric acid electrolytes. Examples are the formation of piperidine or hexahydrocarbazole [17] ... 

Reduction of pyridine by electrolytic methods is the oldest reported industrial process involving pyridine compounds. Merck patented this process in 1896 however, catalytic hydrogenation has supplanted this process for virtually every piperidine manufacturer.8,14,13 The earliest report was by Ahrens, who described a process that others could not repeat.16 Up to 1934 the technology was to use an aqueous sulfuric acid electrolyte and a lead cathode. Many of these reports are conflicting.17-19 The interacting nature of electrochemical variables may be responsible in part for these discrepancies. Thus experimentation by an approach that attempts to hold all but one variable constant is bound to lead to different results depending on where the starting point was chosen or whether an important variable was, or was not,... 

Each electrochemical cell has a porous lead anode and a compressed insoluble lead (IV) cathode. The anode and cathode are submersed in a sulfuric acid electrolyte. 

As already mentioned, oscillations are also observed if a small amount of CO (typically less than 1%) is contained in the H2 fuel gas [107, 108], The oscillations were studied in concentrated sulfuric acid electrolytes (0.5 or 2 M) under galvanostatic conditions. Yamazaki and Kodera [108] propose a model to describe the galvanostatic oscillations that assumes strong attractive interactions between the CO... 

Mahmood et al. [117] studied the electrochemical reduction of carbon dioxide using gas diffusion electrodes. The reduction was performed on metal (lead, indium, and tin)-impregnated Teflon -bonded carbon gas diffusion electrodes in a sulfuric acid electrolyte over a 1 - 5 pH range. A schematic of the cell is shown in Fig. 24. The following reactions occurred ... 

Habashi and Torres-Acuna (H6) described a process that involved th direct recovery of copper and elemental sulfur by anodic dissolution o copper (I) sulfide (white metal). The white metal produced from th (jopper matte analyzed 77.85% Cu and 19.20% S. A closed vessel wa used to prevent the evaporation of the copper (II) sulfate acidified wit sulfuric acid electrolyte. The electrolysis was carried out at room tempera ture. The sulfur originally present in the white metal went into the slim as pure elemental sulfur. The elimination of the converting and polin, steps in the conventional copper smelting and refining process can b realized by use of this technique. 

Figure 6.7 Influence of pulse parameters on deposit morphology for copper deposition from a copper sulfete/sulfuric acid electrolyte [6.102]. p pulse current density ipj limiting pulse current density i average current density jj limiting current density under dc conditions.

The controlled grain structure allows forming an adherent protective oxide coating within days when placed in an electrowinning cell without the necessity of being preconditioned [13]. In sulfuric acid electrolytes, the introduction of cobalt ions into the solution reduces the anode overvoltage and the corrosion rate of lead. 

A uniform distribution of sulfuric acid electrolyte between the plates of the battery is essential if the battery is to provide an optimum service. Two types of departure from this ideal are encountered in practice (i) a heterogeneous distribution of the liquid phase when saturation is incomplete (ii) and the development of concentration gradients within the liquid phase. 

Rapid screening of the electrochemical performance. DuPont has developed rapid half-cell screening techniques to evaluate catalyst activity for methanol oxidation, CO tolerance and oxygen reduction. These measurements are performed in liquid sulfuric acid electrolytes, and up to 32 electrodes can be screened in parallel using a variety of electrochemical techniques in a 3-electrode... 

Major characteristics of the process of microarc oxidation coating of aluminum placed as an anode in a concentrated sulfuric acid electrolytic system (Kharitonov et al., 1987, 1988) can be summarized in the following ten statements ... 

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