Sulphate electrolytes

Figure 2.14 Electrocapillary curve of a gold electrode in pH 3.0 sulphate electrolyte. From...

Acid Vanadous Sulphates and double vanadous sulphates.—Electrolytic reduction of solutions of vanadyl sulphate, V0S04, has given two green, crystalline, acid vanadous sulphates, according to the amount of sulphuric acid also added ... 

The oxidation of pyrogallol in a sodium sulphate electrolyte yields purpurogallin.8... 

The principle behind all galvanic cells can be explained with reference to one of the simplest, the Daniell cell, which was invented in 1836. It consists of a zinc rod in a solution of zinc sulphate, and a copper rod in a solution of copper sulphate. To complete the circuit, a porous solid layer, which allows ions to pass between the sulphate electrolytes, and an external metallic conductor between the zinc and copper, are needed. In this case, electrons then pass around the external circuit and ions travel through the electrolyte solutions (Figure 9.2). 

The galvanic stripping reactions involved in separating iron from a zinc sulphate electrolyte using solvent extraction can be assumed to comprise the following half cell reactions. The major anodic and cathodic steps are ... 

SEPARATION OF IRON FROM A ZINC SULPHATE ELECTROLYTE BY COMBINED LIQUID-LIQUID EXTRACTION AND ELECTRO-REDUCTIVE... 

Iron is an important impurity in many process solutions. The environmentally friendly removal of iron and its downstream valorisation has attracted the attention of many researchers in industry and universities. In the last decade, much effort has been dedicated to the removal of iron from zinc sulphate electrolytes in the hydrometallurgical processing of zinc feeds (1-7). Similar problems of iron control, however, occur in other acidic sulphate-based process solutions in hydrometallurgy, in electroplating [conditioning and control of iron (III) in iron-zinc co-deposition baths (8)] or in the treatment of spent zinc galvanizing pickle liquors (9). Numerous extractants or extractant mixtures for the selective removal of iron from acidic sulphate solutions have been proposed. 

X. Tang, Pu Yu, T. J. O Keefe and G. Houlachi, Characterization of Antimony-Gelatin Additives in Zinc Sulphate Electrolytes Using Impedance Analysis, Aqueous Electrotechnologies Progress in Theory and Practice. D. B. Dreisinger, Ed., The Minerals, Metals and Materials Society, Warrendale, PA, U.S.A., 1997, 115-125. 

The mediation behavior of this redox polymer for the reduction of nitrite is quite different. This mediation process was studied in acidic sulphate electrolytes, and it most likely occurs through reduction of the intermediate by Os(II)... 

In chloride electrolyte systems, titanium anodes with iridium or ruthenium compound catalytic coatings are used to allow evolution of chlorine at the anodes. For these anodes, each short circuit from nodules and dendrites not only destroys the local active coating and its catalytic effect but also completely destroys any ability for that area to oxidize chloride to chlorine. Shorts thereby reduce the life of these anodes which is important since these anodes are relatively expensive compared to lead alloy anodes normally utilized in sulphate based systems. The use of such catalytic anodes is expanding with some sulphate electrolyte copper electrowinning plants now moving to a form of these titanium catalytic anodes a nickel plant has these anodes for mixed chloride/sulphate duty and there appears scope for further expansion into nickel sulphate electrowinning. 

Worrell WL, Liu QG (1984) A new sulphur dioxide sensor using a novel two-phase solid-sulphate electrolyte. J Electroanal Chem 168 355-362... 

Medvedev, G.I. and Makrushin, N.A. (2002) The study of the kinetics of electrodeposition of tin fiom sulphate electrolyte with organic additives. Zh. Prikl. Khim., 75 (8), 1260-1262. 

Reduced anode overpoleiifial via the addition of for example, Co(ii) ions to an acid copper sulphate electrolyte (> Omgdm" ) involves the following... 

To eliminate the tedious operations involved in the preparation of electrodes for weighing to determine the amount of metal deposited or removed, Ehlers and Sease (19) proposed a coulometric coulometer which employs constant current stripping of the metal deposited during the primary electrolysis. The current to be measured is used to deposit copper metal from a copper sulphate electrolyte on a platinum cathode the copper-plated platinum electrode is then reconnected as the anode and the deposited copper stripped off at constant current. The current-time products obtained were suited for the determination of quantities of electricity in the 0.015-75 coulomb range with a standard deviation of0.096 per cent. Castro (20)... 

Thallium can be quantitatively separated by deposition as thallium oxide on a platinum anode at 0.70 V vs. normal hydrogen electrode from an ammoniacal sulphate electrolyte (224). The direct oxidation of thallium (I) to thallium (III) on a platinum anode at 1.34 V vs. SCE does not proceed with 100 per cent current efficiency in 1 M sulphuric acid. Ck)riou, Hure, and Meunier (225) showed that traces of thalUum deposited into a mercury cathode could be redissolved without oxidizing noticeable quantities of mercury. 

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