FR2653450A1 - - Google Patents

Abstract

Method for the selective recovery of lead, zinc and calcium from materials which contain them in the form of oxides or insoluble salts in water, comprising leaching the above materials with a solution of ammonium chloride maintained at boiling temperature, separation of insoluble solids and treatment of the resulting solution with carbon dioxide and ammonia to separately precipitate carbonates of lead, zinc and calcium from where, by calcination or by leaching in acids, is recovered carbon dioxide.

Description

The present invention relates to the selective recovery of lead, zinc

  and calcium from materials which contain them in the form of oxides or salts insoluble in water such as: Waelz oxides and in general the oxides resulting from thermal treatments for enrichment of materials containing lead and zinc, powders from steelworks, roasting materials from lead and zinc minerals,

and oxidized zinc minerals.

  Said materials have typical average analyzes as described in the table below: Percentage content (%) Material type Zinc Lead Calcium Other Oxides type Waelz 40-65 5-10 1-5 Compl. at 100% Oxides of plasma process Tetronics 40-60 5-12 2-3 Compl. 100% Plasma process oxides Tibur Howden 53 9 1-4 "Flame Reactor process oxides 37-46 5-8 1-4 Steel powder 5-35 1-10 1-20" "Roasted blende 55-65 14 0.5-3 "Oxidized zinc minerals (Calamine) 30-50 0.5-5 0.5-5"

Poor oxidized minerals

see 8-20 1-5 10-30 "

  Among the methods for recovering these metals from

  from the above materials, we can cite: - Leaching with sulfuric acid on oxidized zinc materials (traditional processes for the production of electrolytic zinc), in which lead and calcium remain in the residue as sulfates;

  - Two-stage autoclave leaching on oxy-

  zinc dice (U.S. Patent 4,610,721); - Leaching with chlorine and electrolysis of zinc chloride in molten salts (low temperature process by Thomas and Fray, England); - Leaching in a strong alkaline medium (caustic soda) which provides for the electrolytic extraction of zinc in an alkaline medium

  in powder form (U.S. Patent 3,743,501 and Promo- Process

  zinc, France); in these processes the calcium remains in the residue; Carbo-ammonia leaching in which lead and calcium remain in the residue as carbonates (patent

U.S. 4,071,357);

  - Imperial Smelting process which can process Waelz oxides, calcined and roasted from minerals, on a large scale

  of production (at least 200,000 tonnes per year), producing

  health of metals which require subsequent refining processes; Scan Dust plasma process which produces Prime Western class zinc metal;

  - Waels oven process (HTR process, EUA; Berze process-

  lius, Germany), plasma processes (Tetronics, England; Tibur Howden, Canada) and Flame Reactor process (Horsehead

  Resource Development, EUA) which produce materials

chis.

  Among the methods mentioned above, some

  read only an enrichment of the metals in question,

  others extract metals of inferior quality

  lower than that obtained by the electrolytic route, or in forms which are not very marketable and others finally realize

  only zinc extraction with a consumption of reac-

  lead and calcium that remain in the residue.

  The present invention makes it possible to treat materials containing

  oxides or insoluble salts of lead, zinc and calcium and to obtain these elements separately in the form

of tradable products.

  1) The material is mixed with an ammonium chloride solution, which contains from 5 to 85 g per 100 g of water, and the whole is brought and maintained at the boiling temperature corresponding to a pressure of 70 to 2000 kPa , until no more ammonia comes out of the solution. During this phase, the following reactions take place: MeO + 2NH4C1 = MeC12 + H20 + 2NH3 MeCO3 + 2NH4C1 = MeC12 + H20 + C02 + 2NH3 MeSiO3 + 2NH4C1 = MeC12 + H20 + SiO2 + 2NH3 MeOFe203 + 2NH3 + Fe = Me20 2NH3 o Me represents Ca, Zn, Pb and the other bivalent metals

  possibly present as impurities.

  The ammonia released during this phase is used

  in the following phases 2), 4) and 5).

  At the end of the operation, the chlorides solution is separated from the residue consisting of silica, ferric oxide and material.

unsolved solids.

  2) The solution obtained in 1) is treated with ammonia and carbon dioxide while maintaining a pH of 5.7 to 6.0; lead carbonate is thus precipitated according to the following reactions:

NH3 + C02 + H20 = NH4HCO3

NH4HCO3 + NH3 = (NH4) 2CO3

  PbC12 + (NH4) 2C03 = PbCO3 + 2NH4Cl The lead carbonate thus separated is separated from the solution and washed with an ammonia solution in order to rid it of the zinc carbonate which may be co-precipitated which is thus

  transformed into a soluble zinc-ammonium complex.

  3) The solutions obtained in 2), from which the lead carbonate has been separated, are treated with zinc powder which

  causes the lead to precipitate in the form of "cements"

  duel not precipitated as carbonate and any metals more noble than zinc (Cd, Ni, Cu, etc.). "Cements"

are separated from the solution.

  4) The solution obtained in 3) is treated with ammonia and carbon dioxide while maintaining a pH of 6.0 to 6.5; there is thus precipitation of zinc carbonate according to the following reactions:

NH3 + CO2 + H20 = NH4HCO3

NH4HCO3 + NH3 = (NH4) 2CO3

ZnC12 + (NH4) 2CO3 = ZnCO3 + 2NH4Cl

  The zinc carbonate is separated from the solution.

  ) The solution obtained in 4) is treated with ammonia and carbon dioxide while maintaining a pH greater than 6.5; there is thus the precipitation of calcium carbonate according to the following reactions:

NH3 + CO2 + H20 = NH4HCO3

NH4HCO3 + NH3 = (NH4) 2CO3

  CaC12 + (NH4) 2CO3 = CaCO3 + 2NH4C1 Zinc possibly not precipitated in 4) is at this time

  kept in solution because under the operating conditions

  roofs described, during this phase, we have the formation of

soluble zinc-ammonium complex.

  The calcium carbonate is separated from the solution.

  6) The solution obtained in 5), from where the metals have been specified

  pites and o ammonium chloride was restored according to the reactions described in 2), 4) and 5), can be reused

  in 1) for a new leaching operation.

  7) The lead carbonate obtained in 2) is calcined to obtain

  nir the oxide or leached into mineral acids (eg fluoboric acid) and extracted as electrolytic lead; in both cases carbon dioxide is obtained at

  use in phases 2), 4) and 5).

  8) The zinc carbonate obtained in 4) is calcined in order to obtain

  fining the oxide or leached into mineral acids (for example sulfuric acid) and extracted as electrolytic zinc; in both cases carbon dioxide is obtained at

  use in phases 2), 4) and 5).

  9) The calcium carbonate obtained in 5) is calcined to obtain the oxide; we will have carbon dioxide

  to be used in phases 2), 4) and 5).

  The process according to the invention is described in more detail in the example below, which is given only by way of illustration,

  of some embodiments, on steel powders.

EXAMPLE

  The present invention relates, for example, to recovery

  lead and zinc from steelworks powders. A- powders

  The latter used in the example have the following composition: Zinc 18.6% Lead 4.3% Calcium 2.0% Iron 39.0% Cadmium 0.07%

  To an aqueous solution which contains 400 g per liter of chlorine

  ammonium rure are added 450 g per liter of a-

  cairns; the whole is brought to and maintained at the boiling temperature at a pressure of 100 kPa. When the solution no longer releases ammonia, the solid is separated by hot filtration. The solid obtained, washed with boiling water, has the following composition: Zinc 8.0% Lead 1.1% Calcium 1.3% Iron 50.0% Cadmium 0.006% To the filtered solution are added bicarbonate ammonium and ammonia by maintaining a pH below 6.0; we have the lead carbonate precipitation which is separated

by filtration.

  To the filtered solution, which now contains: Zinc 54 g / l Lead 1.5 g / l Calcium 4.4 g / l is added zinc powder which completely precipitates lead and more noble metals than zinc (Cd , Cu, etc.)

  in the form of "cements" which are separated by filtration.

  To the filtered solution are added ammonium bicarbonate

  and ammonia while maintaining a pH of 6.5; we have the pre-

  precipitation of zinc carbonate which is separated by filtration

  tion. The filtered solution now contains: Zinc 23 g / l Calcium 4.2 g / l This solution is brought to a pH greater than 6.5 with

  Ammonia and ammonium carbonate, and we precipitate

  tation of calcium carbonate which is separated by filtration.

  The resulting solution can be reused for further leaching.

Claims (9)

Claims   1. - Method for the selective recovery of lead, zinc and calcium from materials which contain them in the form of oxides or salts insoluble in water:   Waelz oxides and in general heat treatment oxides   enrichment from materials containing lead and zinc, steelmaking powders, roasting materials of lead and zinc minerals, and minerals   oxidized zinc, this method comprising the following steps   a) the treatment of said materials with an ammonium chloride solution maintained at high temperature in order to dissolve the oxides and salts of lead, zinc and calcium in the form of chloride and in order to drive out the ammonia produced therefrom in reactions; b) separating the ferric oxide, the silica and the insoluble residues from the solution; c) adding ammonia and carbon dioxide to the solution obtained in b) while maintaining a pH of less than 6.0 so as to precipitate lead carbon, d) separating the lead carbonate from the solution; e) washing the lead carbonate separated in d) with an ammonia solution to dissolve any zinc carbonate coprecipitated in c);   f) treatment of the solution obtained in d) with the   dre of zinc to precipitate the residual lead and the   more noble metals of zinc in the form of "cements";   g) The separation of the precipitated "cements" - in f) of the solu- tion;   h) Treatment of the solution obtained in g) with ammonia   niac and carbon dioxide by maintaining a pH of 6.0 to 6.5 so as to precipitate zinc carbonate; i) separation of the zinc carbonate from the solution;   1) Treatment of the solution obtained in i) with ammonia   niac and carbon dioxide while maintaining a higher pH   laughing at 6.5 so as to precipitate calcium carbonate; m) Separation of calcium carbonate from the solution; n) Recovery of carbon dioxide by calcination or leaching in acids of lead carbonate; o) Recovery of carbon dioxide by calcination or leaching in acids of zinc carbonate; p) Recovery of carbon dioxide by calcination of calcium carbonate; q) The recycling of the carbon dioxide recovered in n), o) and p) in the precipitation phases of carbonates c), h) and 1); r) Recovery of the ammonia obtained in a) in the phases   carbonate precipitation c), h) and 1).   2. - Method according to claim 1, characterized in that   a) said ammonium chloride solution is at a concentration 5 to 85 g per 100 g of water.   3. - Method according to one of claims 1 and 2, characterized   in that in a) said elevated temperature is between 80 C and the boiling temperature of the solution. 4. - Method according to claim 3, characterized in that said boiling temperature is that corresponding   at a system pressure of 70 to 2000 kPa.   5. - Method according to one of the preceding claims,   characterized in that said elevated temperature is now   naked for a period of time between 1/2 hour and   the time necessary to completely distill the ammonia niac of the solution.   6. - Method according to one of the preceding claims, ca-   characterized in that it includes:   a) the treatment of the solution obtained in b) of the claim   cation 1 with ammonia and carbon dioxide at a pH below 6.5 so as to simultaneously precipitate the lead and zinc carbonates; b) separation of the solution from lead and zinc carbonates; c) treating the lead and zinc carbonates with an ammonia solution so as to dissolve the zinc carbonate as a zinc-ammonium-carbonate complex;   d) separation of the lead carbonate from the solution   the zinc-ammonium-carbonate complex; e) rectifying the ammonia in the solution containing the zinc-ammonium-carbonate complex so as to precipitate zinc carbonate.   7. Method according to claim 6, characterized in that the ammonia and carbon dioxide may be in the form of ammonium carbonate, or ammonium bicarbonate, or ammonium carbamate, or under   form of mixture of these with ammonia and anhy- carbon dioxide.   8. - Method according to one of the preceding claims,   characterized in that the solution obtained in step is treated   b) of claim 2 with zinc powder of way to precipitate lead.   9. - Method according to one of the preceding claims,   characterized in that said ammonium chloride solution   nium can be replaced by solutions obtained in d),   g), i) and m) of claim 1 and in b) of claim cation 6.