Process for preparing lead by electroreduction with ammonium chloride and ammonia

Abstract

A process for preparing lead by electroreduction with an ammonium chloride and an ammonia is disclosed. In the process, an ammonium chloride aqueous solution is used as an electrolyte, a lead compound is used as a raw material, titanium is used as an anode, stainless steel or lead is used as a cathode, and a direct-current electric field is applied in an electrolytic bath; the lead compound is reduced to metal lead after obtaining electrons at the cathode; and at the anode, ammonia is oxidized to nitrogen for escaping, and H.sup.+ ions are generated simultaneously; sulfate radical ions and chloride ions in the lead compound enter the solution to form ammonium sulfate and ammonium chloride; and the lead monoxide and lead dioxide in the lead compound are reduced to a metal lead and OH.sup. ions are simultaneously released to combine with the H.sup.+ ions to form water.

Claims

1. A process for preparing lead by an electroreduction with an ammonium chlorine and an ammonia, wherein in the process, an ammonium chlorine aqueous solution is used as an electrolyte, a lead compound is used as a raw material, a titanium is used as an anode, a stainless steel or a lead is used as a cathode, and a direct-current electric field is applied in an electrolytic bath; the lead compound is reduced to a metal lead after obtaining electrons at the cathode; at the anode, the ammonia is oxidized to nitrogen for escaping, and H.sup.+ ions are generated simultaneously; sulfate radical ions and chloride ions in the lead compound enter the electrolyte and react with ammonia water to form ammonium sulfate and ammonium chloride; and lead monoxide and lead dioxide in the lead compound are reduced to the metal lead, and OH.sup. ions are simultaneously released to combine with the H.sup.+ ions generated at the anode to form water.

2. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 1, comprising the following steps: (1) loading: loading the lead compound on a cathode frame; (2) preparation of the electrolyte: adjusting a concentration of the electrolyte; (3) reduction: applying the direct-current electric field in the electrolytic bath, resulting in that the lead compound is directly reduced to the metal lead after obtaining electrons at the cathode, and H.sup.+ ions are generated at the anode during the reduction, resulting in that a pH value of the electrolyte is decreased; and then adding the ammonia water to control the pH value of the electrolyte; (4) taking out from the electrolytic bath: after completing the reduction, lifting the cathode and taking out the metal lead, and remaining a waste electrolyte; (5) briquetting: briquetting the metal lead to remove moisture from the metal lead to obtain lead briquettes; (6) smelting, casting, and ingotting: smelting, casting, and ingotting the lead briquettes into lead ingots; and (7) causticization of the waste electrolyte: causticizing the waste electrolyte using lime milk to remove ammonium; returning the obtained ammonia gas to participate in the electrolysis; wherein the sulfate radical ions released from the lead compound at the cathode enter the caustic slag in the form of calcium sulfate to be taken away; and the chloride ions in the lead compound are recovered in a form of calcium chloride.

3. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 2, wherein the lead compound comprises lead chloride, lead sulfate, lead monoxide, lead dioxide and mixtures thereof.

4. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 1, wherein the electrolyte is the ammonium chloride.

5. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 1, wherein an anode plate constituting the anode is a titanium mesh, and a cathode plate constituting the cathode comprises a stainless steel plate or a lead plate.

6. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 5, wherein the titanium mesh is a titanium mesh coated with an iridium-ruthenium coating.

7. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 4, wherein the ammonium chloride has a concentration of 0.5-4 mol/L.

8. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 2, wherein in the step (3), a voltage for the reduction is 2.0-2.7 V, a current density is 100-500 A/m.sup.2, and the pH value is controlled to 6-9 with the ammonia water.

9. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 4, wherein the waste electrolyte in the step (7) comprises an ammonium chloride solution.

10. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 2, wherein the electrolyte is the ammonium chloride.

11. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 2, wherein an anode plate constituting the anode is a titanium mesh, and a cathode plate constituting the cathode comprises a stainless steel plate or a lead plate.

12. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 11, wherein the titanium mesh is a titanium mesh coated with an iridium-ruthenium coating.

13. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 10, wherein the ammonium chloride has a concentration of 0.5-4 mol/L.

14. The process for preparing the lead by the electroreduction with the ammonium chloride and the ammonia according to claim 10, wherein the waste electrolyte in the step (7) comprises an ammonium chloride solution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, a brief introduction to the drawings required in the illustration of the embodiments or the prior art is presented below. Apparently, the drawings described below are merely some of the embodiments of the present invention, for those of ordinary skill in the art, other drawings may be derived according to these drawings without creative efforts.

(2) FIG. 1 is a process flow diagram of an embodiment of a process for preparing lead by electroreduction with ammonium chloride and ammonia in the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) In order to further illustrate the present invention, the following illustration is made with reference to the drawings.

(4) A process for preparing lead by electroreduction with ammonium chloride and ammonia is provided. The process is a method for reducing a lead compound to obtain metal lead, and particularly is a method for directly reducing the lead compound at the cathode of the electrolytic bath to obtain metal lead, using ammonium chloride as electrolyte. Wherein, the lead compound includes lead chloride, lead sulfate, lead oxide, lead dioxide and mixtures thereof such as paste/mud of waste lead battery; and the electrolytic bath includes an anode plate, a cathode plate, and a material layer.

(5) The process includes the following steps:

(6) (1) loading: the lead material is loaded on a cathode frame;

(7) (2) preparation of an electrolyte: a concentration of the electrolyte is adjusted;

(8) (3) reduction: a direct-current electric field is applied in the electrolytic bath; the lead compound is directly reduced to the metal lead after obtaining electrons at the cathode, and H ions are generated at the anode during the reduction process of lead, resulting in that the pH value of the solution is decreased; and then ammonia water is added to control the pH value of the solution;

(9) (4) taking out from the electrolytic bath: when the reduction is completed, the cathode is lifted and the lead obtained after reduction is taken out;

(10) (5) briquetting: the lead obtained after reduction is subjected to a process of briquetting to remove the moisture from the lead;

(11) (6) smelting, casting, and ingotting: the lead briquettes are smelted, casted, and ingoted into products; and

(12) (7) causticization of waste electrolyte: the waste electrolyte is causticized using lime milk to remove ammonium; the obtained ammonia gas is returned to participate in the electrolysis: the sulfate radical ions released from the lead compound at the cathode enter the caustic slag in the form of calcium sulfate to be taken away; and the chlorine in the lead compound is recovered in the form of calcium chloride.

(13) The lead compound includes lead chloride, lead sulfate, lead oxide, lead dioxide and mixtures thereof such as paste/mud of waste lead battery or other materials.

(14) The electrolyte is ammonium chloride.

(15) The anode plate includes a titanium mesh, and the cathode plate includes a stainless steel plate or a lead plate.

(16) The titanium mesh is a titanium mesh coated with an iridium-ruthenium coating.

(17) The ammonium chloride has a concentration of 0.5-4 mol/L.

(18) In the step (3), the voltage for the reduction is 2.0-2.7 V, the current density is 100-500 A/m.sup.2, and the pH is controlled to 6-9 with ammonia water.

(19) The solution after the reduction in the step (7) includes an ammonium chloride solution.

Embodiment 1

(20) Two pieces of titanium mesh coated with iridium-ruthenium coating are taken as an anode, and the anode has a width of 10 cm and a height of 20 cm;

(21) a piece of stainless steel is taken as a cathode, and the cathode has a width of 10 cm and a height of 20 cm;

(22) loading: 1000 g of lead chloride containing 64.3% of Pb and 22.4% of Cl are loaded;

(23) preparation of an electrolyte: 5 L of 2 mol/L ammonium chloride solution is taken, and 200 mL of ammonia water is added;

(24) reduction: the reduction reaction is carried out in a constant pressure mode with a voltage of 2.0 V for 20 hours; the pH is controlled to 8-9 with ammonia water; and when the reduction is completed, the lead obtained after reduction is taken out from the electrolytic bath; and

(25) the lead obtained after reduction d subjected to the process of briquetting has a weight of 656.2 g, and the analysis result of the lead sample shows the content of Pb is 98.3%.

(26) Main technical indicators are as follows: the initial current is 10 A, the peak current is 20.8 A, the electricity consumption of the reduction is 339 Wh, the electricity consumption per ton of lead is 525 kWh, the anode current density is 250-545 A/m.sup.2, the lead recovery rate is 99.8%, and the ammonia water consumption is 890 mL (containing 25%-28% of NH.sub.3).

Embodiment 2

(27) Two pieces of titanium mesh coated with iridium-ruthenium coating are taken as an anode, and the anode has a width of 10 cm and a height of 20 cm;

(28) a piece of stainless steel is taken as a cathode, and the cathode has a width of 10 cm and a height of 20 cm;

(29) loading: 1000 g of lead chloride containing 64.3% of Pb and 22.4% of Cl are loaded; preparation of an electrolyte: 5 L of 2 mol/L ammonium chloride solution is taken, and 200 mL of ammonia water is added;

(30) reduction: the reduction reaction is carried out in a constant pressure mode with a voltage of 2.2 V for 20 hours; the pH is controlled to 8-9 with ammonia water; and when the reduction is completed, the lead obtained after reduction is taken out from the electrolytic bath; and

(31) the lead obtained after reduction subjected to the process of briquetting has a weight of 656.2 g, and the analysis result of the lead sample shows the content of Pb is 98.8%.

(32) Main technical indicators are as follows: the initial current is 12 A, the peak current is 23 A, the electricity consumption of the reduction is 370 Wh, the electricity consumption per ton of lead is 575 kWh, the anode current density is 300-575 A/m.sup.2, the lead recovery rate is 99.8%, and the ammonia water consumption is 850 mL (containing 25%-28% of NH.sub.3).

Embodiment 3

(33) 500 g lead paste of waste lead-acid batteries, containing 75.04% Pb (including 5.2% Pb, 41.06% PbSO.sub.4, 44.32% PbO.sub.2, and 3.65% PbO), is taken;

(34) two pieces of titanium mesh coated with iridium-ruthenium coating are taken as an anode, and the anode has a width of 10 cm and a height of 20 cm;

(35) a piece of stainless steel is taken as a cathode, and the cathode has a width of 10 cm and a height of 20 cm;

(36) preparation of a pre-electrolyte: 5 L of 2 mol/L ammonium chloride solution is prepared, and 200 mL of ammonia water is added;

(37) reduction: the reduction reaction is carried out in a constant pressure mode with a voltage of 2.5 V for 20 hours; the pH is controlled to 8-9 with ammonia water; and when the reduction is completed, the lead obtained after reduction is taken out from the electrolytic bath; and

(38) the lead obtained after reduction subjected to the process of briquetting has a weight of 380.0 g, and the analysis result of the lead sample shows the content of Pb is 98.1%.

(39) Main technical indicators are as follows: the initial current is 12 A, the peak current is 23 A, the electricity consumption of the reduction is 411 Wh, the electricity consumption per ton of lead is 1094 kWh, the lead recovery rate is 99.9%, and the ammonia water consumption is 300 mL (containing 25%-28% of NH.sub.3).

(40) The foregoing descriptions are merely preferred embodiments of the present invention, which are not used to limit the present invention. Any modifications, equivalent substitutions, improvements within the spirit and principle of the present invention should be included in the protective scope of the present invention.