FR2463189A1 - Sepn. of non:ferrous metals from zinc ore tailings - by selective sulphation and leaching, leaving an iron rich material used as pigment or for iron prodn. - Google Patents

Abstract

Recovery of nonferrous metals from goethite-rich residues derived from wet processing of Zn ores is carried out by (a) treating the residue with a sulphating agent at 500-750 (pref.550-650) deg.C and (b) leaching the resulting sulphates from the residue. The sulphatinq agent can be H2SO4 or a SO3-contg. gas, e.g. produced by decompsn. of H2SO4 or a sulphate or derived from a contact process plant. The SO3-contg. gas can be enriched by injecting H2SO4. The treatment selectively removes Zn, Cu, In and Cd, leaving a Fe-rich material suitable for use as a pigment or an iron ore (FL).

Description

 The present invention relates to a process for recovering non-ferrous metals contained in a residue rich in goethite (FeOOH), obtained during the hydrometallurgical treatment of zinc ores.

In the production of zinc by hydrometallurgical process, the leaching of ores goes hand in hand, depending on their composition, with the dissolution of more or less significant quantities of iron. One method for separating this iron from the leach liquor is to precipitate it by hydrolysis in the form of goethite which is a well filterable compound. This hydrolysis releases H2SO4 which must be neutralized since it must be carried out at a well-determined pH. Most often, as a neutralizing agent, toasted blende is used and the residue of this neutralizing blende is then found in the iron precipitate. This blende residue is partially made of zinc ferrites, there are also other non-ferrous metals such as Cu, In, Ge, and Cd. After filtration, we then obtain on the one hand a leached liquor with iron and on the other hand the residue rich in goethite containing non-ferrous metals, targeted by the present invention
The aim of the present invention is to provide a process making it possible to economically recover the non-ferrous metals contained in this residue and to obtain both a residue rich in iron which can be recovered, for example as a pigment or iron ore.

To this end, the residue is treated according to the invention with a sulfating agent between about 500 and about 7500C, thereby selectively sulfating the non-ferrous metals, and the sulfated metals are separated from the residue by leaching.

It is essential to carry out the sulfation between about 500 and around 7500 C, because, if one operates below about 5000 C, one produces significant quantities of iron sulphate, and, if one operates above about 7500 C, the zinc sulfation rate is too low. It is advantageous to operate between approximately 550 and approximately 6500 ° C., because in this range the most selective sulfation of the non-ferrous metals is obtained.

The reaction time required to obtain the desired result depends to a large extent on the possibilities of contact between the residue and the sulfating agent and, consequently, on the apparatus used to carry out the sulfation. It goes without saying that this duration can be easily determined, for each particular case, experimentally.

As sulfating agent, advantageously used
H2SO4 and Zou of S03. It is in this way that sulfation can be carried out with H2SO4 or with a gas containing SO3, this gas being obtained either by the decomposition of H2SO4 or of a sulfate, or an installation for manufacturing H2SO4 by the process from @@@ @@@. We can further enrich this sulfating gas and injecting il2SC3.

 When dealing with a wet residue and using a gas containing 803 as the sulfating agent, it is advantageous to dry the residue between about 100 and about 2000 C before bringing it into contact with the sulfating agent .

 The selectively sulfated residue is advantageously leached with acidulated water at a p11 ranging from 1 to 5, preferably from 1 to 2, to avoid hydrolysis of the sulfates, and at a temperature between room temperature and around 900 ° C. , preferably at a temperature ranging from about 20 to about 600 C.

It is particularly useful to carry out leaching against the current, this method making it possible to obtain concentrated solutions of non-ferrous metals.

 The following examples will better understand the process of the invention and its advantages.

 These examples relate to the treatment of a wet residue rich in goethite taken directly from the filter used to separate it from the bare leach liquor.

This wet residue (42% by weight of water) contains in the dry state, in% by weight: 7.15 Zn; 41.2 Fe; 0.06 In; 0.82 Cu.

Example 1
1 kg of residue is mixed with 10% by weight of 36N H 2 SO 4 and the mixture is calcined at 6000 ° C. for 2 hours.

The calcination residue is leached for 2 hours at 600 ° C. in 5 liters of water acidified with H2SO4 until a pH between 1 and 2.

Composition of the leaching residue, in% by weight: 1 Zn; 60.5 Fe, 0.011 In; 0.09 Cu.

Yields in solution (or extraction), in 90 Zn; 6 Fe; 87.5 In; 93 Cu.

Example 2
0.5 kg of residue is dried at 1200 ° C. and the dried residue is ground.

 A basket containing 0.1 kg of this dry residue is placed in a tubular oven, which is heated to 6300 ° C. and through which a gas is passed for 1 hour and at a flow rate of 0.2 Nm 3 / hour. containing 7% by volume of SO3 and coming from an installation for the production of H2SO4 by the contact process.

 The residue thus sulphated is leached for 2 hours at 600 (in 1 liter of water carried by H2SO4 at m pH between 1 and 2.

 Composition of the leaching residue, in% by weight 1.05 Zn; 58.5 Fe; 0.014 In; 0.1 Cu.

 Yields in solution, in%: 92 Zn; 1.8 Fe; 94 Cu; 86 In.

Example 3
1 kg of residue is mixed with 5% by weight of 36N H 2 SO 4 and the mixture is calcined at 6000 ° C. for 2 hours.

 The residue thus sulphated is leached at 200 ° C. in countercurrent with 1 liter of water brought to pH 1 with H 2 SO 4, using 3 steps each having a duration of 1 hour.

 Composition of the leach residue, in% by weight: 1.5 Zn; 62 Fe; 0.1 Cu; 0.02 In.

 Composition of the solution, in g / l: 95 Zn; 20 Fe; 9 Cu; 0.5 In; 0.25 Cd.

 Such a solution can be treated by known techniques for the recovery of Zn, Cu, In, Cd.

Claims (12)

 1. Process for recovering non-ferrous metals contained in a residue rich in goethite (FeOOH), obtained during the hydrometallurgical treatment of zinc ores, characterized in that the residue is treated with a sulfating agent between approximately 500 and approximately 750 C by thus selectively sulfating the non-ferrous metals, and the sulfated metals are separated from the residue by leaching.  2. Method according to claim 1, characterized in that the sulfation is carried out between "about 550 and about 6500 C. 3. Method according to claim 1 or 2, characterized in that as sulfating agent is used H2SO4 and / or SO3. 4. Method according to claim 3, characterized in that the sulfation is carried out with 112ide of a gas containing SO 3 and obtained by decomposition of 112804 or of a sulfate 5. Method according to claim 3, characterized in that the sulfation is carried out using a gas containing SO 3 and obtained in an installation for manufacturing H 2 O 4 by the contact process.  6. Method according to claim 5, characterized in that the gas is enriched by injecting H2SO4 therein. 7. Method according to any one of the preceding claims, characterized in that a wet residue is treated. 8. Method according to any ur of the claims: ions 1 to 3 and according to claim 7, characterized in that the residue is mixed with H2SO4 and the mixture thus obtained is heated to a temperature within the above-mentioned temperature range .  9. Method according to 1 any one of claims 1 to 6 and according to revendîcatj0ri7, characterized in that the residue is dried at a temperature between about 100 and about 2000 C and the residue thus dried is treated with a gas containing SO3 to a temperature within the aforementioned temperature range.  10. Method according to any one of the preceding claims, characterized in that the leaching is carried out with acidulated water at a pH ranging from 1 to 5 and at a temperature between room temperature and about 900 C.  11. Method according to claim 10, characterized in that the p11 is maintained at a fixed value by addition of H2SO4. 12. Method according to any one of the preceding claims  @@@@@@ characterized in that one carries out the leaching by countercurrent.