Method for electrolytic production of lead

FIELD: metallurgy.

SUBSTANCE: method includes electrolytic refining of lead in the melt of salt halogenides with use of liquid metal cathode and anode. At the same time the process of electrolysis is carried out with application of one and more bipolar electrode, such as liquid lead, at cathode density of current from 0.5 to 2.0 A/cm2, anode - from 0.3 to 1.5 A/cm2 and temperature of 450-600C.

EFFECT: higher extent of raw lead treatment from admixtures.

1 tbl

 

The invention relates to ferrous metallurgy, in particular the production of lead electrolytic method.

There is a method of refining bismuthide lead (Delimarsky J.K., Zarubitsky OG and other non-ferrous metals, 1974, No. 15, p.23-25) [1]. The essence of this method is to clean up lead by anodic polarization in the molten eutectic mixture PbCHl2(18 mol.%) - ZnCl2(30 mol.%) - KCl (52 mol.%) at the current density of 0.38-0.40 to A/cm2in the temperature range of 440-470C. This method is characterized by insufficient depth cleaning of lead, low efficiency of the process due to the low current density, and also requires the use of an expensive reagent ZnCl2and additional power consumption due to the need for preliminary preparation of the electrolyte.

There is a method of refining of lead from impurities (EN 2291213, publ. 2006) [2]. The method includes anodic polarization of the melt containing the chlorides of potassium and lead, while anodic polarization black lead is carried out at a current density of 0.41-1.2 a/cm2in the temperature range of 480-700C at a concentration of KCl 30-50 mol. %. The molten lead is placed in an electrolytic cell separated from each other cathode and anode spaces, while the anode is a rough lead, and the cathode is a graphite electrode located above the cathode prostranstva system the melt of potassium chloride and lead and when applying direct current to produce electrolysis. Obtained on the cathode lead contains, wt%: 0,0001 Ag; 0,0005 Bi; 0,0005 As; 0,0007 Sn; 0,015 Sb. The use of the known method is a direct one-step anodic-cathodic refining limits the possibility of increasing the purity of the cathode metal: received cathode metal to antimony content does not meet the requirements of the current standard. In addition, the process in the temperature range from 600 to 700C causes an intensive evaporation of components of the melt, which leads to changes in the composition and melting point of the electrolyte.

The task of the invention consists in the electrolytic production of metallic lead with a high degree of purity without the use of expensive reagents and the reliability of the cell.

To achieve these objectives carry out electrolytic refining of metallic lead in the molten halide salts using a liquid metal cathode and the anode. The process of electrolysis is carried out with application of one or more bipolar electrode, which is liquid lead, at a cathode current density of from 0.5 to 2.0 A/cm2, anode from 0.3 to 1.5 a/cm2the temperature of 450-600C.

The method consists in the following. The molten crude lead is placed in the anode part of the cell, the lead brand C1 - bipolar the left and the cathode part. When enabled, a constant electric current of the rough surface of the lead acquires a positive charge, the surface of the liquid metal bipolar electrode in contact with the anode electrolyte - negative charge, and the surface in contact with a cathode electrolyte, a positive charge. Under the influence of electric current occurs at the anode dissolution lead to cations Pb2+moving in molten salt, and deposited on the negatively charged surface of the bipolar electrode. The process is repeated, and is deposited on the cathode lead, the last double electrolytic cleaning. Thus, unlike [2], high degree of purification black lead from impurities is achieved by dual electrolytic cleaning, achieved by the use of liquid metal bipolar electrodes, the number of which can be changed depending on the required purity of the cathode lead. The bipolar electrode provides a consistent decrease in the concentration of electrophoretically impurities from the anode to the bipolar and bipolar to a liquid metal cathode electrode. This allows you to apply a greater range of current density. Accordingly, the claimed interval of values of anodic and cathodic current density is selected in C the dependence on the concentration electropolishing component of the alloy. The smaller concentration of impurities, the higher will be the value of the current density. Accordingly, by increasing the concentration of impurities it is necessary to reduce the current density. The recommended interval current density is due on the one hand the speed of the process and the purity of the cathode metal. Below iaof 0.3 A/cm2and ito0.5 a/cm2low productivity of the process above ia1.5 a/cm2and ito2.0 a/cm2- concentration electropolishing component exceeds the allowable level in the cathode metal. The temperature interval from 450 to 600C. greater than the melting temperature of not more than 50C, allows to minimize the evaporation of the melt.

A new technical result achieved the stated solution is to increase the level of cleaning black lead from impurities.

The method was tested in pilot scale and illustrates an example of a practical application. Electrolytic receipt of lead was carried out in the electrolytic cell, having made integral body made of heat-resistant concrete. The interior of the body divided by a partition into two parts: the anode and cathode. The lower part of the cell divided by concrete walls on metal in three parts: the anode, and cathode bipolar - so the m way the bipolar metal in contact with an anode electrolyte and the cathode. Current supply to the electrodes are graphite rods. Loading, unloading metal and sampling for chemical analysis through lundbye pipe. Implementation of the proposed method in the electrolyzer requires consistent with the following steps:

- the initial loading of metal;

- the supply current to the electrodes;

- fusion of the electrolyte;

- set levels anode and cathode electrolytes;

download black lead;

- discharge cathode metal;

- sampling.

Experimental testing of the method was performed with a current load of up to 1 kA for 15 days in a melt of potassium chloride and lead continuous control modes of the refining process.

Technological parameters of the method:

anodic current densityfrom 0.3 to 1.5 a/cm2
cathodic current density : from 0.5 to 2.0 A/cm2
current loadfrom 200 to 1000 And
- process temperaturefrom 450 to 600C

The composition of chernovagalina, wt.%: antimony from 1.0 to 1.5; bismuth from 0.01 to 0.02; arsenic from 0.05 to 0.07. The results of the electrorefining process, including the chemical composition of raw materials and products of electrorefining shown in the table.

As can be seen from table data obtained on the cathode lead contained in wt.%: <0,0003 Ag; <0,003 Bi; <0,0005 As; 0,0006 Sn; 0,0004 Sb that meets the requirements of GOST 3778-98.

Table
MetalContent, wt.%
SbSnCuBiZnFeAsAgPb
Source1,390,0006<0,001to 0.032<0,0003<0,00030,020,003The OST.
Cathode0,00040,00060,001 <0,003<0,0003<0,0003<0,0005<0,0003The OST.
Anodic33,100,00200,0010,430<0,00030,00250,310,040The OST.

The way the electrolytic production of lead refining the molten halide salts using a liquid metal cathode and the anode, characterized in that the electrolysis process is carried out with application of one or more bipolar electrode, which is liquid lead, at a cathode current density of from 0.5 to 2.0 A/cm2, anode from 0.3 to 1.5 a/cm2and a temperature of 450-600C.



 

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