US2805195A - Electrolytic manganese - Google Patents

Description

United States Patent I ELECTROLYTIC MANGANESE James H. Jacobs, Marietta, Ohio, and Michael C. Carosella, Niagara Falls, and James B. Culbertson, Lockport, N. Y., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Application April 2, 1956,

Serial No. 575,313

2 Claims. ((31. 204-105 The present invention relates to an improved electrolytic maganese process and, more particularly, to a process employing electrolyte modifiers that control the formation of the deposited manganese metal.

In the production of metallic electrolytic manganese, the form of the deposited metal is of the greatest importance since it influences the efliciency of the process, the purity of the deposited metal, and the ease with which the deposited metal can be stripped from the cathode.

If the deposited metal is coarsely granular,it may build up on the'cathode in small nodules that grow radially,

forming a cauliflower-like structure from which electrolyte is not easily washed. Also, in this form the metal is not easily stripped from the cathode material (if this is not the same metal as that being deposited), since the metal tends to come off in individual nodules rather than in sheets or plates. In some processes, the deposited metal is removed from the cathodes by flexing or vibrating the latter; if the deposit is nodular, it tends to flex with the cathode and does not break loose. Another difficulty encountered is treeing; that is, some nodules may grow at a much greater rate than the average, thus becoming much extended above the surface of the cathode deposit. In some cells this may make it mechanically diflicult to remove the cathodes, or may upset current distribution (thus aggravating the condition). In addition, the nodules tend to be broken off and lost during handling, decreasing metal recovery.

A further difiiculty encountered is the influence of cathode metal structure on deposition time. Obviously, if cathodes must be changed frequently, the overall process etficiency is greatly reduced. As mentioned above, treeing of the cathode metal, once started, becomes'selflpropagating and the extension or growth of the trees can be 2,805,195 Patented Sept. 3, 1957 'ice M It is an object-of the present invention to extend by reducing the frequency at which cathodes must be removed, stripped, prepared and reinserted in cell.

Another object of .the invention is to produce electrolytic manganese metal of improved purity.

A further object ofthe invention is to produce metallic manganese metal that is sound, dense, less friable and of greater thickness than otherwise obtained, and, therefore, easier to handle and use.

The electrowinning of some metals is much more easily accomplished than others; copper, silver, and nickel may be electrodeposited without particular difliculty. One of the metals which is more difficult to obtain electrolytically is manganese which tends to deposit in irregular fashion and in nodular form, and is very prone to form trees.

Prior practice for electrowinning of manganese was such' that not more than a 25- to 30-hour deposition period could be achieved. If it was attempted to continue deposition beyond this length of time, the quality of the metal degenerated and became unacceptable.

By the process of this invention, high-quality manganese metal can be electrodeposited for periods of two to four times as long as is possible with prior processes.

The present invention comprises a process for electrowinning of manganese from an electrolyte composed sub- I stantially of manganese sulphate, ammonium sulphate, and potassium sulphate which serves as a smoothing agent. The presence of specific quantities of potassium sulphate in the electrolyte has a marked effect upon the character of the manganese metal deposited at the cathode.

By the addition or other provision of potassium sulphate in the electrolyte, the character of deposited metal is altered from soft to dense, hard compact metal. This makes it possible to increase the continuous plating time by a factor of from two to four. Inclusion of potassium sulphate in the electrolyte has'made it possible in some cases to obtain continuous deposition of dense, hard manganese metal for periods up to 72 and 96 hours, a

far longer period than is possible in the absence of this addition agent, and appreciably longer than has been pos-. sible with any additive of the prior art.

As is well known in the art, a small amount of sulphur dioxide is added to the cell feedsolution (in a concentration of about 0.1 to 1.0 gram per liter) to stabilize the solu tion and to increase the current efiiciency. I

More specifically, it has been found that the provision of between 20 and grams per liter of potassium sulphate in the electrolyte will be effective in extending the deposition time without any sacrifice in current efficiency.

The data in the table below show that the progressive I increase from 3.3 to 25 gms. per liter in the concentration of potassium sulphate in the cell feed over a 16-month period enabled the operators to extend the plating time by 50% with no drop in the current efficiency. This means that the plate is 50% thicker and that the appearance was good at the end of 72 hours.

the deposition time, and thus simplify and improve the elficiency of the process for the electrowinning of manganese Table Grams per Liter in Cell Feed Current Plating Run Time, Appearance N0. eieney Hrs.

M11 K K3504 (NHQgSO;

1. 48 3. 3 115 61 48 Generally good but nodular. 1.72 3.8 118 61 48 and. 2. 32 5. 2 114 62 72 Surface not good. 3. 60 8. 120 63 48 Good. 6.20 13.8 132 62 48 Nodular, me-

dium base. 6. 5 14. 6 137 61 48 Generally good.

but nodular. 8.0 17.8 136 62 48 Good. 8.50 19.0 r 133 65 48 Very good. 9.75 21.8 133 62 72 Medlumtothiok I basewith L a F l nodules.

10.7 23.8 128 64 "7'2 Good. 10.8 7 2m ,125 v 63.6 72' Good. ms 25.=--' 123- 63 I 72 Good. 11-.0: 2cc 4 can i '72 Good.

lhiotnieasured.

mammalian tearsaehssiayer 'oiaieaianrancaassaarraum the cathode. The

product had built up on this base in-the form oi' nodules.

The ohjectivei of thei tests which yieldedthe ahoye data was toproduce' thickplate' of dense structure and surface. Fo'r'the s'atuecurrente'fiiciencythe thickn ss-of'rthe" plate is'adirect function of the time;

Therefore; the latingiime was extended asidn as was compatible with the production of'dense' plate having a oftrees or' nodular struct 'ue. 'lhedata show that 48 1mm plate was not uniformly oouf until the 150- tassii'irnsulphate c'oncentration approached 2Q; gms. p'er liter'of cell feed; also'that the attempt town 72 hour'sin run No: 3 was not successful-because the surface appeararice' was not good enough; From run No; 9" on, the-plate was" dense and thick with 72-hour plating time and was esse'n'tially free of trees or nodular structure since the potassium sulphate'concentr'ation was increased -frorn= 2f to about 25' gnfis. per liter.

The upper limit of 70 gms. potassium sulphate per liter was chosen as being the limit of solubility in a synthetic cell feed produced from materials essentially free ofsodium but containing ammonium sulphate and manganese sulphate in normal amounts. This limit is the concentration of potassium sulphate compatible with the other constitutentsof the normal cell feed for the electrowinning of manganese, i. e., manganese and ammonium sulphates with sodium sulphate as an impurityand sulphur dioxide addition as known to the prior art. Experiments on the use of various concentrations of sodium sulphate in the absence of'potassium have shown that salt is neither harmful nor beneficial. Consequently, it is considered as an impurity but it has a marked efi ect on the solubility of potassium sulphate. It has not been determined as to when this concentration of sodium sulphate becomes critical. V 7

However, early experiments showed that sodium sulphate 38 gms. per liter permitted a concentration of 3 0 gms; per liter of potassium sulphate (68 gms./l. total) in the standard cell feed. This was the maximum obtainable with this sodium concentration. Consequently, a figure of 70grr1s. potassium sulphate per liter'was specified as a practical top'liinit. This assumes that the concentration of potassium sulphate could easily reachthis figure in the standard cell feed with a minimum of sodium sulphate present since potassium salts are generally speaking more soluble thanj sodium-salts.

In an exam le ofthe process of the invention, an'elec- V trolyte was continually electrolyzed to produce a catholyte containing. about 11.0 grams per liter manganese, 128.5 grams per liter ammonium sulphate, 0.75 gram per liter sulphur dioxide, and 32 grams per liter potassium sulphate in the cathode compartment of a: diaphragm electrolytic cell employing 99% lead-1% silver alloy anodes and stainless steel cathodes. The cathode current density employed was abgurfl 40' amperes per square foot and a catholytepH of about 815 was maintained; Solid, dense manganese" metal was deposited on the cathode for 48 hours before a'fi'n'e nodular structure began to appear; There was" noevidence of'oe einor loss in current e'fiictencyat any time during the'de'posiiion period;

' This isacontinuatien in part of our depending applica tion- Serial No. 378,403" filed September 3, 1953', now abandoned; v v

Vth'atis claimed is": I a

1. In a process for the electrowinning ofmetallic manganeseemploying a diaphragm compartment. cell and an electrolyte comprising an' aqueous manganese and ammoniufm sulphate solution containing an amount of sulphur'dioxide' efiective to stabilize the solution and increase the current eificie'ucy, the improvement which comprises providing and maintaining in said electrolyte solution during electrolysis b'etween'about 20 and grams per liter of potassium sulphate, whereby a thick, dense metallic manganese deposit substantially free of nodules is produced'.

' 2; A'p'ro'ces's for the electrowinning' of metallic manganese employing a diaphragm compartment cell and an electrolyte comprising an aqueous manganese and ammoniun-i sulphate solution containing an amount of sulphur dioxide effective" tostabilize the solution and increase the current efficiency comprising, providing in said cell an aqueous solution containing manganese sulphate, ammonium sulphate, sulphur dioxide, and between 20 and 70 grams per liter of potassium sulphate, and electrolyzing said solution to-for'm at the cathode of said cell, a thick, dense metallic manganese deposit substantially free of nodules.

7 Ref rences crted in'tue file of thispaterit I V 'UNITEDSTALTES PATENTS '2',4'46 ',3l3" Vedensky L Aug. 3, 1948

Claims (1)

1. IN A PROCESS FOR THE ELECTROWINNING OF METALLIC MANGANESE EMPLOYING A DIAPHRAGM COMPARTMENT CELL AND AN ELECTROLYTE COMPRISING AN AQUEOUS MANGANESE AND AMMONIUM SULPHATE SOLUTION CONTAINING AN AMOUNT OF SULPHUR DIOXIDE EFFECTIVE TO STABILIZE THE SOLUTION AND INCREASE THE CURRENT EFFICIENCY, THE IMPROVEMENT WHICH COMPRISES PROVIDING AND MAINTAINING IN SAID ELECTROLYTE SOLUTION DURING ELECTROLYSIS BETWEEN ABOUT 20 AND 70 GRAMS PER LITER OF POTASSIUM SULPHATE, WHEREBY A THICK, DENSE METALLIC MANGANESE DEPOSIT SUBSTANTIALLY FREE OF NODULES IS PRODUCED.