FR2590277A1 - PROCESS FOR DESULFURIZING THE PASTE FROM SINKED BATTERIES - Google Patents

Abstract

WET METALLURGY PROCESS FOR RECOVERY BY ELECTROLYSIS EXTRACTION, IN A PURE METAL FORM, OF THE LEAD OF THE ACTIVE MASS OR DESULFUROUS PASTE OF THE DEPLETED ACCUMULATOR BATTERIES, CHARACTERIZED IN THAT IT CONTAINS THE STEPS CONSISTING OF: A. SUBJECT THE ACTIVE MASS TO LEACHING WITH AN AQUEOUS SOLUTION OF AN ACID CHOSEN FROM THOSE SUITABLE FOR ELECTROLYTIC EXTRACTION; B. TREAT THE LIXED MASS WITH OXYGENATED WATER UNDER THE CONDITIONS INDICATED IN A, WITH SIMULTANEOUS UNDERWAY OF THE FOLLOWING REACTIONS: (CF DRAWING IN BOPI) UNTIL A QUANTITATIVE REDUCTION OF ALL THE LEAD BIOXIDE CONTAINED IN THE ACTIVE MASS; C. SEPARATE THE SOLID RESIDUE FROM THE SOLUTION CONTAINING THE DISSOLVED LEAD SO OBTAINED, WHICH CAN BE SENT DIRECTLY TO THE EXTRACTION OF THE LEAD BY ELECTROLYTIC MEANS.

Description

The present invention relates to a desulfurization process

of the

spent batter batter.

  In the various known processes for the desulphurisation of such pastes, by treating the sludge of spent batteries with alkali metal or ammonium carbonate solutions, a solution is obtained in which the sulfur passes almost entirely in the form of soluble sulphate ( alkali metal or ammonium), and a mixture of insoluble lead compounds, which separates from the

  solution and thoroughly washed with water, is virtually free of sulfur.

  This mixture is easy to reduce by carbon at a temperature relative to

  low (800 - 900 C), without significant release of sulfur dioxide

  and without production of mattes containing lead.

  Hot metallurgical reduction of this product is therefore the most widely used means, also because of the advantages it has with regard to production efficiency, the long service life of ovens

  reduction, and high efficiency for lead extraction.

  The hot metallurgy operations carried out on the materials containing

  lead requires special precautions for the transport of

  and furnace loading, and because of the potential for smoke and volatile dust from furnaces; As a result, refining plants need to have large filtering facilities and an extensive control network.

  to prevent lead pollution from work premises and the environment.

  factories. This is what gives great importance to processes that allow

  put the recovery of lead, from the active mass, in a form

  metal, and which can be an interesting solution,

  place especially those who proceed by metallurgy, by completely wet way,

  like electrolytic extraction or "electroplasty".

  The desulphurized pulp has on average the following composition: - lead carbonate (PbC03) ............ 50 to 52% - lead sulphate (PbSO4) ........... .. 2.5 to 4% - lead peroxide (PbO2) ............. 14 to 16% - lead oxide (PbO) ............... ...... 11 to 12% - metallic lead (Pb) ............

  . 5 to -7% As is known, the problem of hydrometallurgical treatment of the active mass of old accumulators is practically to make soluble, in the solution chosen for electrolysis, all the constituents of the mixture, in particular PbO 2, which represents a significant percentage. Indeed, the .DTD: residue of the acid attack of the mixture must not cause an ex-

Lead cessation.

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  On the other hand, because of the known insolubility of PbO 2 in the normal acids used in the electrolytic process, without a prior PbO 2 reduction treatment, the residue of the acid attack of the mixture is very rich in

  lead and must be subjected to hot metallurgical recovery.

  In the known state of the art, the solubilization of all the constituents

  killing of the active mass in different electrolytes is obtained in different ways. In chronological order, the following patents can be cited: - C.E. Tucker, in U.S. Patent 1,148,062, advocates heating accumulator sludge to convert PbO2 to soluble PbO and Pb20; W.C. Smith, in U.S. Patent 1,752,356, for solubilizing PbO 2 to attack it with caustic soda, subjecting the active mass to heating in a reducing atmosphere (PbO formation); J.H. Calbeck, in U.S. Patent No. 1,911,604, leaches the

  active mass of the accumulator by means of a solution of sodium acetate.

  Lead oxide and sulphate go into solution, whereas PbO2 is normally insoluble in the electrolyte. But in the presence of metallic Pb and in the electrolyte in question, a local battery is established, by which PbO2 and an equivalent quantity of metallic lead pass into solution; A.F. Gâumann, in U.S. Patent 4,107,007, performs the leaching of the

  active mass by a concentrated solution of alkali metal hydrate, addi-

  molasses or raw sugar or similar products. In these circumstances

  Pb oxide and sulphate go into solution and go to electrolysis.

  The behavior of PbO2 is not specified;

  Prengaman, in U.S. Patent 4,229,271, proposes two means for eliminating

  to reduce the PbO2 of the active mass and to make it entirely soluble in the usual acids for the electroplating process: a) drying at 100 ° C of the active mass, followed by roasting in a reducing atmosphere at a temperature of between 290 ° C. and 325C; b) a treatment of the aqueous suspension of the active mass with sulfur dioxide, or with sulphite or bisulfite of alkali metal or ammonium. U. Ducati, in US Pat. No. 4,460,442, reacts the active mass of the accumulator in the presence of a strongly alkaline solution at 100 ° C. to 1200 ° C. in order to obtain a precipitate of minium which has the property of dissolving completely in hot concentrated solutions of fluoboric or fluosilicic acid; A.Y. Lee and E.R. Cole of the Bureau of Mines in R.I. 8857 propose two ways to reduce PbO2 from the active mass:

  a) by adding Pb powder during the leaching process using fluorescent acid

  silicic acid of the already desulfurized pulp as a result of a reaction with the ammonium carbonate; b) adding ammonium bisulfite during the desulfurization treatment with the ammonium carbonate. The proposed methods for the thermal reduction of PbO 2 in a reducing atmosphere have the drawback of increasing the treatment cycle of two

  operations, drying and roasting. These courses of treatment require

  strict control of working conditions and, in addition, must be carried out

  by a unit (oven or roasting device) equipped with a

  adequate dusting. Moreover, even if the temperatures are low, mana-

  Dry material is a source of pollution.

  The reduction process, during the acid attack by means of the addition of lead powder, involves the transport of part of the lead to make it

  powder; it is therefore an expensive process.

  The sulfur dioxide, sulphite or bisulphite reduction process, before carbonation, involves some expenditure of reagent, but what

  more importantly, it increases the fuel consumption by around 25%

  bonate for desulfurization; the corresponding expense is not negligible;

  At present, carbonate expenditure is the most important of the whole process.

  The object of the invention is to solve the problems mentioned above, as regards the hydrometallurgical treatments, by electrowinning

  of the active desulphurised mass of exhausted accumulators.

  This object is achieved, according to the invention, by a hydrometallurgical process designed for recovery by extraction, electrolytically, in a form

  pure metal, lead from the active mass or desulphurised

  exhausted, characterized in that it comprises the following operations: a) leaching the active mass with an aqueous solution of an acid selected from those which allow the electrolytic extraction; b) treat with oxygenated water the leached mass according to stage a) with the following reactions: (1) Pb4 + + H202 Pb2 + + 02 + 2H (2) Pb + Pb4 + 2Pb2 + until quantitative reduction of all the lead dioxide contained in this active mass; (c) separate the solid residue from the solution that contains dissolved lead thus obtained and that may be sent directly to the lead

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  The invention is hereinafter described in more detail with reference to

drawing.

  The starting material for the process consists of the active substance (paste) already separated from the other constituents of the exhausted accumulators, and already desulphurized by the known process. This material is leached with the aqueous solution of an acid capable of performing the following electrolytic extraction (preferably, fluoboric acid and fluosilicic acid), to which the amount of

  of oxygenated water necessary to obtain the maximum dissolution of all

  laid with lead, and more especially PbO2 and metallic Pb.

  During the acid etching of the paste, the oxygenated water causes the reaction: Pb4 + + H 202 b2 + + 02 + 2H (1) as a result of which the totality of PbO 2 is reduced to the state of PbO and dissolved

by the acid present.

  The large amount of O 2 released during the reaction (1) physically activates the surface of the metallic Pb particles contained in the pulp, which has the effect of promoting the reaction: PbPb + Pb4 + 2Pb (2) and all the lead metal of suitable particle size dissolves, causing

  also a saving of hydrogen peroxide corresponding to Pb4 + which is reduced.

  After the acid leaching due to the addition of hydrogen peroxide, only organic substances (small debris of separators and ebonite, fibers, etc.) and Pb sulphate are retained as undissolved substances in the desulfurized pulp.

  transformed in the desulfurization operation.

  The liquid / solid mixture of the filtration contains not more than 5% of the Pb contained in the starting material, and after a roasting to destroy the

  organic substances, can be returned to the desulphurization phase.

  The filtered solution contains all the Pb in ionized form and normally does not require purification, since it is the same Pb powder, physically activated by oxygen, which is involved in the reaction (1) which produces the displacement action ( also known as carburizing), with regard to the

  impurities that can be dissolved in low levels during the

acid proof.

  The automatically purified solution can then be sent directly to the lead electrolytic extraction, which takes place in normal cells with insoluble graphite anodes and with cathodes consisting of

thin lead plates.

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  Under suitable conditions, a cathodic deposit can be obtained of excellent quality and high purity while avoiding as much as possible the deposit of

PbO2 at the anode.

  The small amounts of PbO2 that sometimes inevitably form must be returned to the acid leaching stage with hydrogen peroxide. The cathodes are sold in the form of plates as electrolytic Pb. The solution

  from the electrolysis is returned to the acid leaching of the pulp.

  The invention is described below in more detail by means of

  an exemplary embodiment with reference to the drawing, which illustrates the differences

steps of the process.

  980 g of desulfurized pulp, washed well, containing 70.5% Pb dry,

  0.68% of Sb, and 0.18% of S, were leached with 5 1 of elution.

  electrolyte-depleted trolyte containing 49 g / l of Pb ++ and 139 g / l of free HBF4. After 1/2 hour of stirring at 50 ° C., hydrogen peroxide (in

  35% solution), 4.6% treated pulp, and reacted at room temperature.

erased for another 1/2 hour.

  The filtration separates: (Pb 34.2% - 80 g of insoluble residue having as composition: Sb 2.4%

(S 2.2%

  (181.5 g / l of Pb ++ - 5 1 of electrolyte containing lead and comprising: 0.6 g / l of Sb + 1 + ((25.1 g / l of free HBF4) Leaching with fluoboric acid and hydrogen peroxide extracted 96.01% of the total lead contained in the pulp, and all the sulfur remained in the residue by subjecting the electrolyte-containing 5 1 to electroplasty in cell with graphite anodes ( previously coated with PbO2) and electrolytic lead cathodes in thin plate, 630 g of cathodic Pb are obtained and

9 g of PbO2 at the anode.

  The electrolytic cell worked for 24 hours at 7 amps and

2.5 V.

  The cathode current density was 280 A / m2.

  The current efficiency was 97%.

  The cathodic lead had the following composition:

  Sb <0.001 - As 0.001 - Sn c 0.001 - Bi. 0.002 - Cu = 0.0003 - Ag 0.0005.

  The exhausted electrolyte that needs to be sent back to attack the new

  paste contained 53 g / l Pb ++ and 131 g / l free HBF.

  The attached figure represents, by way of example, an application schema

of the process according to the invention.

  In general, it should be noted that, according to the invention, the use of hydrogen peroxide has the following advantages over other reducing agents used in the state of the art known for the reduction of PbO2: - it has no toxicity; - It does not introduce foreign ions to the solution that must be used for electrolysis and be recycled permanently; - it is a reagent easy to find on the market and not very expensive;

  - it can be precisely dosed with no loss, because the end of the

  PbO2 production is indicated by a sharp shift in suspension color from brown red to brown gray. The modification is detectable visibly; - with a consumption of 4 to 5% of H2O2 (in solution at 35%), one obtains a

  Pb extraction yield of not less than 95%.

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Claims (4)

  1 - Wet metallurgical process for the recovery by extraction by electrolysis, in a pure metallic form, of the lead of the active mass or desulfurized pulp of exhausted accumulator batteries, characterized in that it comprises the steps of: a) subjecting the active mass to leaching with an aqueous solution of an acid selected from those suitable for electrolytic extraction; b) treat with hydrogen peroxide the leached mass under the conditions indicated in a), with simultaneous progress of the following reactions: 4+ 2 ++   (1) Pb + H202. Pb + 02 + 2H + (2) Pb + Pb4 + 2Pb2 + up to the quantitative reduction of all the lead dioxide contained in the active mass;   (c) separate the solid residue from the solution containing the dissolved lead thus ob-   held that can be sent directly to the extraction of lead by trolytique.   2 - Process according to claim 1, characterized in that the reaction   (2) according to b) is activated by the oxygen which is released during the reaction (1) se- lon b).   3 - Process according to claim 2, characterized in that the reactions   (1) and (2) are accompanied by a carburizing action, with regard to the   purities present, exerted by the metal Pb activated physically by 02 which is gives off in the reaction (1).   4 - Process according to claim 1, characterized in that it comprises, in addition, the steps of: d) treating the solution which contains dissolved lead according to c), by electrolytic extraction, with formation of lead cathodes metallic;   e) recycling the exhausted electrolyte obtained in step d) to the leaching stage a).   - Process according to claim 1, characterized in that the acid se-   a) is fluoboric or fluosilicic acid.