DE71155C - Electrometallurgical extraction of zinc - Google Patents

Description

IMPERIAL

PATENT OFFICE.

CLASS 40: Metallurgy.

The inventor has succeeded in cooling a to make zinc-containing electrolytes unnecessary and by other more advantageous measures to replace. Purposed to cool down by allowing lower current density To save electrical work, this means was certainly the only possible one, if the The conductivity of the electrolyte could not be increased and as long as there were no zinc salts found that, assuming technical usability, a higher temperature limit respectively allowed low current densities.

The zinc alkali sulfate double salts proposed by Herrmann are known to permit lower current densities than the simple zinc salts, which have been given special consideration in Patent No. 56700. However, their conductivity should be lower than that of the simple zinc salts due to insufficient solubility. Apart from this, these double salts have an even worse and more disruptive property from a technical point of view. The zinc is part of the anion in these double salts and migrates as such with 2 SO ⁴ molecules to the anode; the zinc precipitated on the cathode is reduced by secondary processes. This peculiarity of the double salt has practically very unpleasant consequences, which make a smooth course of the electrolysis in the baths almost impossible.

If one works for metal separation or refinement with a soluble anode, one already occurs at very low current densities on the anode solid salt, which ultimately prevents the passage of current completely prevents.

Amp.
500

current density of

sqm

With an anode step with simple

Zinc sulphate liquor of 30 ^° B. does not yet induce crystallization, in the case of a concentrated zinc ammonium sulphate liquor already at 75%

The process is caused by the fact that with the latter salt two equivalences of zinc vitriol appear at the anode. In the case of an insoluble anode, the situation becomes still more complicated. If zinc sulphate is electrolyzed alone, this is split into Zn and SO ⁴ , the latter forming sulfuric acid with the water, releasing oxygen; this, specifically lighter than zinc vitriol, rises in the air. An alkali double salt, e.g. Potassium zinc sulphate, for example, is electrolytically decomposed under normal circumstances into K and Zn SO * SO ⁴ , so that even if the anode is insoluble, an accumulation of zinc vitriol takes place on the anode, which draws the resulting free acid to the ground. The slightest changes in concentration, on which the property of the zinc, sometimes to the anion, sometimes to the cathion, depends to a great extent, influence this process, so that the practical result of the process is that a part of the acid produced goes upwards, the predominantly larger part goes down. In the long run, no circulation, however excellently managed, can help against this. A remedy can be found by dilution, but only too much at the expense of conductivity.

The inventor has established through experiments that in the same measure as the dilution, so also the temperature of the splitting ratio

Claims (6)

of the alkali zinc sulfate double salts. These changes in decomposition can be controlled experimentally, degree by degree. Finally, between about 40 and 50 ^° C., the point is reached where the decomposition of the double salt into the simple salts is complete. A temperature of 50 to 60 ° C is recommended for practice; for with this the cleavage takes place with absolute certainty as with the simple salts, so that all the free sulfuric acid, as with these, rises upwards. The simple proportions which lead to the decomposition of zinc vitriol alone for the circulation, provided both - through at the cathode Zinc precipitated from the solution - like at the anode. - by the free sulfuric acid that is formed without zinc vitriol accumulation - a dilution occurs, are therefore also double salts for the alkali zinc sulfate manufactured; electrochemically, at this high temperature, one can no longer use a double salt at all talk. In spite of the fact that the double salt character has now been completely abolished in the electrochemical relation, the proportions are the Cathode current densities for zinc precipitation remained unchanged, so that is evident The double salt character of the electrolyte is not at all a prerequisite for its use lower current density, but only the partial or complete secondary reduction of the zinc by the primary alkali. In addition, the zinc content of the electrolyte was resp. Zinc sulphate reduced to such an extent that, depending on the required current density, there are 45 to 90 g of zinc sulphate (Zn SO _i -f-jH ₂ O) in the liter. This solution is then so enriched with alkali metal sulfate, as in the BEZW to be used. for practical reasons it dissolves at a temperature approx. 10 ° lower. Depending on the current density, the electrolyte contains 45 to 90 g of zinc sulphate and 300 to 150 g of alkali sulphate and, as stated above, is used at a temperature of about 60 °. From a chemical point of view, too, one can no longer speak of a double salt. The advantages achieved by this electrolyte are these: ι. simple circulation, 2. Great conductivity (300 to 400 pct. Greater than that of simple zinc sulphate, more conductive Concentration), 3. Applicability everyone practically into consideration coming current density of 10 to 1 t; o - » sqm 4. Applicability for soluble anodes, 5. Reduction of polarization due to increased temperature, 6. Lowest effort. Using this electrolyte it is possible to use steam engines Condensation the ton of zinc from the ores with an effort of only 3 to 3.5 tons To make coals good according to their calorific value. How very little the temperature still beeinflufst the zinc precipitation in the electrolyte described here, follows from the fact, that in an attempt which at -j- 92 ⁰ C. and a current density of 100 - sqm the zinc was not spongy, although water vapor bubbles on the cathode formed. Godfather N t-An s ρ ruch: In the electrometallurgical extraction of zinc using zinc and Alkali at the same time containing electrolytes the heating of the electrolytes.