US1101620A - Extraction of a metal by electrolytic exhaustion of a solution of a salt of this metal. - Google Patents

Description

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entrain stratus grjaja (13mm? aromas HENRI MARIE DEKKER, or rAia'i's, FRANCE' nxraacrron or a METAL BY ELECTROLYTIC nxnausrron or A soitu'rron or A sat-tr or arms METAL. p x

No Drawing.

T 0 all whom it may concern:

Be it known that I, NICOLAS HENRI MARIE DEKKER, subject of the Queen of the Netherlands, residing at 29 Rue de la Sourdiere, Paris, France, have'invented new and useful Improvements in the Extraction of a Metal by Electrolytic Exhaustion of a Solution of a Salt of This Metal, of which the following is a specification.

In electrolytic operations secondary reactions are always found due to the decomposition of the water which in its turn is due to the presence of free acid in the bath,

which acid favors the formation of hydro gen and oxygen which produce basic salts, oxids, etc., which unfavorably atl'ect the operation.

Of all the usual metals, only one can be treated in a practical manner at the present time, namely copper which is generally produced in that way, but that production relates only to the refining of the mattes, for it has not hitherto been possible to obtain copper by exhausting a complex electrolyte. The greatest difl'ic'ulty at present met within obtaining good electrolytic deposits, is therefore due to water dilutions without which no electrolysis has hitherto been undertaken and when it is desired to obtain by electrolysis a metal, either by refining, or by exhausting a solution of one of its salts, the operation is always carried out with baths obtained by dissolving in water a salt of the metal to be obtained, to which are added one or more other salts of different metals generally of alkaline metals. In order to avoid that disadvantage, it has been suggested to use hygroscopic salts, but without success, because that method always leads to secondary reactions due to the use of these salts or to hydrogen or oxygen or to both these gases produced by: the decomposition of the water by the free acid. lit. has thus been found that hydride, oxids or basic salts of zinc are formed during electr'oly'sis of salts of zinc. In the same way, it has been found that basic salts or oxid of iron are formed in the electrolysis of an iron salt.

In order to avoid the disadvantages due to the decomposition of water, that is to say, to the presence in the baths, of oxygen and hydrogen due to the presence of free Specification of Letters Patent. Application filed Ma 1t, 1913. Serial at. 767,569.

Patented June 3(1), 1914.

acid, it has been suggested to use sulfurous gas, chlorin, air deprived of its oxygen, etc.

It has been even suggested to add to the baths oxidizing or reducing substances, according to the result to be obtained, but always without appreciable success, all these attempts having failedowing to the forma' tion of hydrogen or oxygenor both gases,

according to individual cases.

The present invention cohcerns an electrolytic process for producing a metal by exhausting a solution of a salt of the metal. This process avoids the drawbacks cited hereinbefore and is suitable for the usual metals such as iron, copper, zinc, lead, silver, nickel, cobalt, and the like.

In a crystallizable salt such as zinc sulfate (soanmu o the water, 7H O contained in the crystal is a part of the molecule SOZnJZHgO'.

It is the water of crystallization. This water is not free and its action is quite different from that of water of dissolution. If a bath containing no water but water of crystallization of the salts is electr'olyzed, there is no production of hydrogen or oxygen. This water seems not to be subjected to any decomposition from the current and it appears to act onl for maintaining the constitution of the mo ecule of salt.

According to the present invention, the anode is placed in a compartment containing water separated by a porous wall from gust 17, 1912, filed an application, Serial No. 715,598, relating to a process for tr'eating or'es, in which he uses a reagent of a particular character, such reagent or electrolyte being substantially the same as used in the present process.

According to thepresent invention the mass is crystallized and melted in its water of crystallization in order to form the electrolytic bath. In a porous pot containing water, an insoluble anode will be placed and this pot will be introduced in a bath of metallic .salts prepared, as specified before, without water of dissolution, and in which the cathode dips. The metal will depose itself during electrolysis and the acid will pass through the porous wall and mix itself with the water of the anodic pot without any diffusion of the cathodic liquid through the wall of that anodic chamber. Two cases could then be met with according to metals to be exhausted: 1. It will be necessary to heat the bath in order that the deposit should be compact; 2. The heating will not be necessary.

First case.In order to constitute the bath when the heating is necessary, the proceeding is based on the fact that a salt crystallizing with water, can always be melted in its water of crystallization, if care is taken to compensate for the loss of water due to evaporation by a suitable and limited addition of new water, as already explained. By proceeding in that manner, it

is possible to produce, without the addition of free acid, a very good bath for refining metals, as already stated, and also another bath intended for exhausting various metals which it is desired to deposit. But in the latter operation, the constitution of the bath comprises the addition to the salt of the metal to be deposited on the cathode, of other salts that can be electrolyzed in the presence of water, but which do not give a metallic deposit. If by way of example, it

is desired to Jdepose iron, iron pyrite will be treated by means of area ent formed with sulfuric acid, sodium sul ate, and magnesium sulfate, a solution will be obtained,

' comprising for each three molecules of iron sulfate, one molecule of sulfate of sodium and one molecule of sulfate of magnesium. By concentrating this solution until it is crystallized by cooling, we will obtain at that 'moment no longer a mixture of three molecules of iron sulfate plus a molecule of sulfate of sodium plus a molecule of sulfate of magnesium, but :a combination represented by the formula 3(FeSO 7H O.l |;l Ta,SO,MgSO,6H O in which there are 27 molecules of water representing in weight 27 l8' l4=86 gr. of-

water.

- When the whole iron is deposited, the bath will contain in proportions: 1 mole'culeof sulfate of sodium- Na SO,=142 gr., 1 molecule of sulfate of magnesium MgSO,=124E gr., that is to say 266 gr. of sulfates, and 27 molecules of water-486 gr. It is necessary to see here what is represented by the 486 gr. of water.

1. 180 gr. that is to say, 101 1 0 which are necessaryto the molecule 'of sulfate of sodium Na SO 1OH O.

MgSOJH O.

Out of the 486 gr. of water there are therefore 180+126=306 gr. which have been used for the crystallization of the sulfates of sodium and of magnesium. There is left therefore 486306:180 gr. which are free and do not constitute a diluted solution. In fact, the two sulfates of sodium and of magnesium which are in solution in their water of crystallization, receive only a small addition of 'water owing to the presence of the said-180 gr. of free water, a portion m of which is moreover evaporated not only owing to the temperature at which the heated bath is operated, but also by natural evaporation; the total quantity of water evaporated in the two cases cannot however be equal to 180 gr. This quantity of water (1 80w) is insufficient for dissolving the molecule of sulfate of sodium which requires 10H O and that of sulfate of magnesium, which requires 7 H O: The free acid which it is true could here exercise its action has however passed into the anodic electrolyte at the anode. At the end of the operation, there is therefore left one molecule of sulfate of sodium (Na SOJOILO), one molecule of sulfate of magnesium (MgSO 7H O) desired temperature. FThi's solution can be obtained hot, so that by cooling to .the ordinary temperature, the solution has the tendency to crystallize. The quantity of water contained in the said solution, represents: the quantity of water required by each of the salts dissolved for crystallizing, plus the small quantity of water which prevents the solution from becoming crystallized. If the operation is carried out with the same salts as before, there will be found, at the end of the operation, sulfate of sodium and sulfate of magnesium plus the water which was saturated with the three salts; sodium, magnesium and decomposed sulfate. Crystals'in a deliquescent state are therefore present here. If calamin (oxid' of zinc) has been attacked by the reagent above referred to,

there will be obtained, by concentrating the solution until it has the tendency to crystallize cold a combination of:

1 molecule of double sulfate of zinc and sodium Na SO ZnSO 6H O.

1 molecule of double sulfate of zinc and magnesium MgSO ZnSOJSH O. 1 molecule of sulfate of zinc ZnSOJH O,

that is to say, for water 19H O or Na SO 10H O, and 7H O or 126 gr.- are used for forming the crystal MgSOJI-I O.

Consequently 180+126:306 gr. are used for forming crystals of sulfate of sodium and sulfate of magnesium. There are left therefore 342306:36 gr. of free water, without free acid, which, being added to the water of crystallization of the bath, do

not constitute a diluted solution. Therefore there will always be a solution sufficiently concentrated to prevent decomposition of water from taking place. It must be further pointed out that in the case of the exhaustion of the bath, the whole metal to be deposited will have gone to the cathode, and there .will be left in the cathode bath only the molecules MgSOJI-I O Na SOJOH O and 36 gr. of free water, while the acid which formed with the metal deposited on the cathodes, the molecules of the salt of the said metal, will be concentrated in the anode bath. The latter is then emptied into What remains of the cathode bath, then the water which in the anode bath gave rise to the acid liberated by the deposition of the metal, as well as the 36 gr. of free water, are evaporated, and in that way the reagent which was used for the treatment of the ore, is recovered, which in the present case can be represented by the formula Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is A process for preparing a metal by exhaustinga solution, consisting in forming a cathodic bath containing a salt of this metal and no water, excepting the water of crystallization of the salts forming the bath; the anode dipping in water separated from the cathodic bath by a porous wall; passing a current through said bath, the acid liberated in the cathodic bath by electrolysis passing through the porous wall into the anodic bath while the metal deposes itself on the cathode.

In testimony whereof I aflix my signature in presence of two witnesses.

NICOLAS HEN-RI MARIE DEKKER.

Witnesses:

J ULES BEL, LUoIEN MEMMINGER.

and