Electrolyte sulfate

Ideally a standard cell is constmcted simply and is characterized by a high constancy of emf, a low temperature coefficient of emf, and an emf close to one volt. The Weston cell, which uses a standard cadmium sulfate electrolyte and electrodes of cadmium amalgam and a paste of mercury and mercurous sulfate, essentially meets these conditions. The voltage of the cell is 1.0183 V at 20°C. The a-c Josephson effect, which relates the frequency of a superconducting oscillator to the potential difference between two superconducting components, is used by NIST to maintain the unit of emf. The definition of the volt, however, remains as the Q/A derivation described. 

It represents the case of the reaction at the metal electrode in which ions of the same metal discharge at the electrode from the electrolyte. It can be said that copper ions in the electrolyte (copper sulfate solution) possess a free energy GCu(ej, and those in the copper metal electrode possess a free energy Ci(ll(-ril.. Then, if a copper ion is to leave its place in the copper sulfate electrolyte structure and occupy a position in the structure of the copper electrode, the free energy change accompanying this process will be ... 

Amorphous NiP alloys with > 10% P (generally obtained by deposition from acidic electrolytes) are non-magnetic (see [66] and references therein), as required of the underlayer for thin-film media. Although the structure of these alloys is generally assumed to be a solid solution of P in Ni, a recent report [67] has suggested that NiP with 7.4-10% P deposited from acid sulfate electrolytes is better represented by a microcrystalline structure composed of 4-5 nm fee NiP solid-solution grains. 

Given the efforts in this group and others (Table 1) to form the Cd based II-VI compounds, studies of the formation of Cd atomic layers are of great interest. The most detailed structural studies of Cd UPD have, thus far, been published by Gewirth et al. [270-272]. They have obtained in-situ STM images of uniaxial structures formed during the UPD of Cd on Au(lll), from 0.1 M sulfuric acid solutions. They have also performed extensive chronocoulometric and quartz crystal microbalance (QCM) studies of Cd UPD from sulfate. They have concluded that the structures observed with STM were the result of interactions between deposited Cd and the sulfate electrolyte. However, they do not rule out a contribution from surface reconstructions in accounting for the observed structures. 

The anomalous features are observed on well-ordered (111) surfaces in a variety of electrolytes over a wide range of pH (0-11), but the potentials at which the features appear and the detailed shapes of the I-V curves vary considerably. Specifically, the potential region (versus RHE) in which the features appear changes with anion concentration in sulphate and chloride electrolytes, but not in fluoride, perchlorate, bicarbonate or hydroxide electrolyte. In sulfate electrolyte, at constant anion concentration the region shifts (versus RHE) with varying pH, while in fluoride, perchlorate, bicarbonate and hydroxide electrolyte it does not. The use of UHV surface analytical techniques has established to a reasonable (but not definitive) extent that adventitious impurities are not involved in the anomalous process, i.e., the only species participating in the chemistry are protons/hydroxyIs, water and the anions of the solute. On the basis of the pH and anion concentration dependencies, I agree with the... 

The influence of antimony at a level of 300 ppm in copper electrolysis is also significant. The morphologies of deposits made from a pure acid-copper sulfate electrolyte and from an identical solution to which the antimony was added are shown in Figures 5 and 6. There are many other combinations of impurities and electrolytes which exhibit this changing surface appearance and deposit orientation besides those selected as examples. Anion effects are also not uncommon, with the halogens often causing the more notable changes. 

Figure 4. Scanning electron micrograph for the deposit obtained from acidified zinc sulfate electrolyte (9) (0.77M Zn", 7M H2SOh) containing 40 ppb Sb, X 920...

The influence of Pb + ions on the kinetics of zinc electrodeposition on Zn electrode in acidic sulfate electrolyte was discussed [217] in terms of a reaction model involving hydrogen adsorption and evolution, a multistep mechanism for zinc deposition and the overall reaction for zinc dissolution. The strongly adsorbed Pbads inhibited all the reactions taking place on the zinc electrode. 

Also, the influence of aluminum sulfate, animal glue, and an extract of horse-chestnut nuts on zinc electrowiiming from a weak acidic sulfate electrolyte prepared from an industrial waste product was investigated [401]. The use of additives mixture has a beneficial effect on zinc electrowinning and results in smooth, slightly bright zinc deposits. 

Electrodeposition and stripping of tellurium and CdTe in sulfate electrolyte was studied by voltammetric and electrogravi-metric experiments [206]. 

The filtrate from the jarosite process is now ready for copper electrowinning. In this step, copper is extracted from the sulfate electrolyte down to a concentration of 500 ppm. While leaving the nickel, tin, chrcme, cadmium and zinc in solution. Each batch produces 679 lb6 of cathode copper of 99% purity. 

A new solid state chemical sensor for sulfur dioxide utilizing a sodium sulfate/rare earth sulfates/silicon dioxide electrolyte has been developed. The addition of rare earth sulfates and silicon dioxide to the sodium sulfate electrolyte was found to enhance the durability and electrical conductivity of the electrolyte. The electrolyte exhibits a Nernstian response in the range of SC gas concentrations from 30 ppm to 1 %. 

The sodium sulfate electrolytes mixed with Y SO and Si02 are better solid electrolytes for the SO- gas detector ... 

B. Perform the electrolysis in part A with the copper sulfate electrolyte heated to... 

The mercury-mercurous sulfate electrode. Several commercial suppliers offer the mercury-mercurous sulfate electrode with a saturated potassium sulfate electrolyte. The potential (E° + E ) of this electrode system is 0.658 V on the hydrogen scale at 22°C.34 The electrode constitutes one-half of the Weston standard cell,35 an international secondary voltage standard, and is outstanding in reproducibility,36 in spite of the slight tendency of mercurous sulfate to hydrolyze and its rather high solubility. 

Because special preparative procedures are not necessary (except for the preparation of mercurous sulfate electrolytically), this reference electrode is recommended for use in place of the silver chloride or calomel electrodes when chloride ion must be rigorously excluded. 

Figure 5.21 Cyclic voltammograms for a gold electrode upper curve for successive scans in the presence of chloride ion lower curve for sulfate electrolyte.

Bottcher s accumulator — This was an - accumulator with a lead and a zinc electrode in a zinc sulfate electrolyte. Upon discharge zinc ions are reduced to the metal, and lead is oxidized to lead sulfate. These processes are reversed upon charging. 

Sudoh et al. demonstrated the destruction of phenol via electrolytically generated Fenton s reagent in a ferrous sulfate/sodium sulfate electrolyte. These studies were performed in an H-type electrolyzer (Fig. 12) on a graphite plate cathode [52]. At an operating potential of -0.6 V vs. Ag/AgCl, a solution pH of 3, and a ferrous concentration of 2 mol/m, a phenol degradation current efficiency of 60% was reported for initial phenol values ranging from 260 to 2600 ppm. 

Townley and Winnick [102] studied the removal of SO gases at the cathode from simulated coal-burning power plant stack gases. The cell functioned in two modes, used a molten sulfate electrolyte and 10 cm LiCr02 electrodes, and operated at 512 °C. In the first mode, the electrochemical cell was driven electrolytically by applying 0.7 V across the two electrodes. The following reactions were thought to take place at the cathode (information on the equilibrium potentials for SO2 and SO3 reduction can be obtained from [101] ... 

Permanent anodes are used in the electrowinning of base metals such as copper, nickel, cobalt, and zinc. The only function of the anode is to transfer electrons from the electrolyte to the external circuit. The usual reactions on the anode surface are oxygen evolution in sulfate electrolytes and chlorine evolution in chloride electrolytes. The permanent anodes have the disadvantages of maintenance costs to clean the... 

World nickel metal production in 2002 was 678000 tons [39]. Hydrometallurgy has typically been applied to the treatment of nickel-copper mattes, anode nickel, and reduced laterite ore. The sulfide concentrates are usually oxidized by roasting and then smelted to copper-iron-nickel sulfide matte (75-80% Cu-Ni), which is refined or used directly to make M onel metal. Cathode nickel can be produced from a variety of electrolytes, including chloride, sulfate, or a mixed chloride-sulfate. The former two are acid systems used in leaching and electrowinning. Mixed chloride-sulfate electrolytes are used for electrorefining the nickel sulfide matte from the traditional matte-smelting operations. 

The energy consumption in electrowinning depends on the thermodynamical voltage, electrode polarization, and electrolyte resistivity. The conductivity of nickel electrowinning electrolytes (catholyte) at 60 °C is typically 120mScm 1 and for nickel electrorefining electrolytes at 60 °C it is about 200 mS cm-1 [47]. The sulfate electrolyte conductivity can be estimated using Eq. (26)... 

The advantages of using chloride electrolytes compared with sulfate electrolytes are higher electrical conductivity, lower electrolyte viscosity, lower overpotential for nickel reduction, and higher solubility and activity of nickel. An important factor is the lower anode potential of chlorine evolution compared with oxygen evolution in sulfate electrolytes using the common lead anodes. Chloride electrolytes require insoluble or dimensionally stable anodes, usually titanium coated with an electroactive noble metal or oxide, and a diaphragm system to collect the CI2 gas from the anode. The chlorine liberated at the anode is recycled for use in the leach circuits. In practice, some decomposition of water... 

Chlorine cannot be used in pure sulfate electrolyte nickel(III) hydroxide is normally used (28). Other oxidants that can be used to remove cobalt from the sulfate system include peroxide, persulfate, and ozone [5, p. 803]... 

The pH of the solution is raised by adding, for example, nickel carbonate. Iron hydroxide coprecipitates other impurities from the anolyte, particularly lead and arsenic [43], Oxidation of iron is accomplished by using air in pure sulfate electrolyte systems and by using chlorine in chloride systems. Iron can be removed from pure chloride electrolytes by solvent extraction with tributylphosphate. 

Two representative examples of this behavior are reflected in two distinct different chemical systems, namely (a) copper deposition from an acid sulfate electrolyte containing the co-inhibitors PEG-C1 and a bi-functional catalytic species SPS-C1 [12, 136, 243, 264] and (b) silver deposition from a cyanide electrolyte where inhibition is provided by adsorption of silver cyanide species and catalysis is achieved through adsorption of selenocyanate, SeCN [72-75]. Similar behavior is evident in some electrolytes used for the deposition of bright soft gold films [121, 180, 255-261, 267]. 

Copper sulfate (electrolytical) Determination of the Cl /SO ratio, of metallic impurities such as Ni2+ and Zn2+, organic additives... 

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