Electrolysis of Zinc Chloride

Two Cl ions give up one electron each and become a Cl2 molecule Figure 6.16 Electrolysis of zinc chloride solution using platinum electrodes. 

Ah an example we quote the electrolysis of zinc chloride solution with molal concentration m = 0.5, at a pressure of 1 atm. and temperature 25 °C. The mean activity coefficient of zinc chloride at this concentration y-, =0.51. 

In order to outline broadly the mechanism of electrolysis, the behavior of ions of a dissolved salt during electrolysis may be illustrated by the account of the electrolysis of a solution of zinc chloride (Figure 6.16). When zinc chloride is dissolved in water, one zinc ion and two chloride ions are produced from one molecule of salt. The zinc ion will carry two... 

During the electrolysis of a solution of zinc chloride, both of the ions of the solute (i.e., Zn2+ and Cl ) have their ionic charges neutralized at the cathode and anode, respectively. These ions may therefore be said to have been discharged and liberated in the form of elemental zinc and chlorine. To determine whether the ions corresponding to the solute are always discharged at the electrodes during electrolysis, it is necessary to inquire into the behavior of other electrolytes. 

Perhaps the best approach to understanding the operation of battery cells may be had by reconsidering a simple case of electrolysis. The non-spontaneous changes that occur during the electrolysis of an aqueous solution of zinc chloride may be represented by the following equations ... 

In our next experiment we will produce more metallic zinc by a process of electrolysis. The apparatus used is shown in Fig 7. It consists merely of a U-tube with two electrodes and a solution of zinc chloride. If the current is permitted to pass through this solution for a short time, we notice a beautiful formation of metallic zinc at the negative electrode, while the anode product will be the gas chlorine. 

A second example is provided by ammonium compounds, e.g. ammonimn chloride, NH4CI. These are very similar to alkali metal compounds. Indeed, ammonium compounds and potassium compounds often form mixed crystals with each other. Furthermore, electrolysis of ammonimn chloride solution with a mercury cathode at 0 °C gives a grey mass that is similar in character to sodimn or potassimn amalgam. Thus, it reduces copper dichloride solution to copper, zinc chloride to zinc, etc. On warming, it decomposes into ammonia and hydrogen in the proportions required by the equation... 

In cases of forced overdischarge or accidental charging, both of these abuse conditions can lead to electrolysis of water within the cell to create a hydrogen/oxygen gas mixture. Proper venting of the cell can relieve internal pressure, but the explosive gas mixture can pose a risk to the immediate area until the gas dissipates. Accidental charging can also lead to evolution of highly toxic chlorine gas (in the case of zinc-chloride types). 

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. 

F. P. Haver, D. E. Shanks, D. L. Bixby and M. M. Wong, Recovery of Zinc from Zinc Chloride by Fused Salt Electrolysis, U. S. Bureau of Mines, Rept. Invst. No. 8133,1976. 

Several methods are available for producing thorium metal it can be obtained by reducing thorium oxide with calcium, by electrolysis of anhydrous thorium chloride in a fused mixture of sodium and potassium chlorides, by calcium reduction of thorium tetrachloride mixed with anhydrous zinc chloride, and by reduction of thorium tetrachloride with an alkali metal. 

The electrolysis of a mixture of ZnCl2 with alkaline chlorides and the effect of different elements were investigated as a method to extract zinc from ores and industrial wastes. The studies on electrolysis of ZnCl2 in molten ZnCl2-KCl-NaCl... 

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