DE2607956C2 - Process for the extraction of high-purity zinc compounds from technical, in particular As-containing, materials by ammoniacal solvent extraction - Google Patents

Description

The present invention describes a method for obtaining high-purity zinc solutions from impure, in particular As-containing materials by ammoniacal solvent extraction with subsequent recovery high purity zinc compounds.

Ks has long been known that metals which form cationic amine complexes are very easily converted into Solutions containing ammonia / ammonium salts can be dissolved, provided they are in oxidic or carbonate form shear form. Aniinkoinplex-forming metals are z. B. zinc, copper, cadmium, silver and others. In the event of

z. B. of zinc oxide dissolves according to the formula

ZnO Hh-2) NH ₍ + 2NH; = [Zn (NH _J ) J ^il + H ₁ O

( _n = 2-4). The number of ammonia ligands depends on the concentration of the ammonia, the temperature and the type of anion.

The metals mentioned dissolve very quickly and with a very good yield. In this way For example, the zinc content of contaminated, oxidic zinc ores, roasted zinc sulfide ores, but also of substances that are used as intermediate products in a wide variety of metallurgical processes or waste materials are produced, brought into solution. Parts of metallic zinc provide the dissolving process no difficulties, since in ammoniacal solution oxygen eagerly absorbed and thus metallic Zinc is converted into ionogenic form. The dissolution chemistry listed for zinc applies equally This also applies to other amine-forming accompanying metals.

The filtration of the ammoniacal solutions obtained in this way is technologically very convenient because it is filtration-inhibiting In contrast to acidic dissolution, silica is not in colloidal, gel-like form, but in macromolecular polymers is transferred. The ammoniacal, metallamine-containing solution can so from insoluble gangue (silica, aluminosilicates) and all non-amine-forming cations (e.g. iron, lead, Manganese) are completely freed.

The anions contained in the precursors to be dissolved normally pass into the ammoniacal solution as long as they are not bound to insoluble cations (e.g. in the form of lead sulfate). The ammoniacal solution is therefore normally in addition to the anion present in accordance with equation (1), ζ. B. carbonate, still contain varying amounts of sulfate, chloride, phosphate and other anions. Likewise, the arsenic, which almost always accompanies zinc, is transferred quantitatively into the ammoniacal solution _{as arsenate ion (AsO 4} ^{3 -).} Its removal presents the main problem in the ammoniacal preparation of pure zinc compounds from contaminated materials.

It has also long been known that the zinc amine complexes formed according to equation (1) are not very are solid, but are subject to quite extensive secondary dissociation, which z. B. in the case of Zinc tetramine complex (/ 7 = 4) according to the formula

[Zn (NHO ₄ P '.- [Zn (NHj) ₂ ] ^{2 f} I- 2NH ₃ (2)

runs. This makes it possible, by reducing the ammonia concentration, e.g. B. by overcooking the

_S5 complex to completely destroy and the zinc as Hydroxide or, in the presence of COj, precipitate as carbonate. This zinc compound is precipitating according to the above from Gangart and all non-amine-forming cations practically completely free.

do Of this, e.g. in US Pat. No. 16 08 844 Made use of. A separation of the zinc from other amine-forming cations as well as from soluble ones Anions is neither intended nor possible.

in BF 7 46 633 ^; n further execution of this

(, 5 Working method describes a method in which under slightly increased pressures and temperatures with the addition of oxygen also the leaching of sulphidic seeds / substances is possible. Also is in the same

ntschrift stated that when adding CO ₂

Lye solution the precipitating zinc in zinc carbonate

^2Ü u will lead. The latter is separated into zinc oxide

? i, infcrt and the CO ₂ fed back into the process.

I this method offers no possibility of s iSerming interfering cations (e.g. nod!) Or

^Lösrich _d ^e g _n ^A US ⁿ p "tentschriften 26 95 843 and 28 05 918 proposed the method in which from

lexen ie both zinc and copper containing, κ ammoniacally leached ores a largely Γ'fer-free zj _n knee precipitate or a largely k-free copper amine solution can be obtained. In doing so, use is made of the different bond strength Her be ^: the amine complexes, but not on the role of other cations or anions

There are obvious variations of the processes already described. For example, US _{Pat. No. 2,305} describes a process for dissolving copper scrap under oxidizing conditions in ammoniacal solutions. The solution is boiled after the impurities have been separated off and the deposited precipitate is treated with sodium hydroxide solution to separate the two metals.

The so-called ARBITER process (see M. C. K u h η, N. A r b i t e r and H. Kling Comparative Chemistry and Process Development in Copper Hydrometallurgy, 2nd ann. Meeting, ^ "Metallurgy Group of ClM, Oct. 1972) treated essentially the mechanism and completeness of the dissolution of sulphidic ore cones with regard to Le different components, but goes on that Separation of the cationic and anionic components does not occur.

In OS 25 15 601 a process is described in which preferably polyvalent non-ferrous metals are extracted from an aqueous ammonium salt-containing solution, which contains the metals as dissolved metal amines, with the help of a canonical ion exchange resin and then contact with a ΝΗ, / NrM salt solution. be ated. Their concentration is chosen so that the volume of the eluting solution essentially completely removes the free ammonia and, as a result of the extraction ^agents mentioned, the functional group of which is the oxime group, is essentially based on the metals copper and nickel In summary, the state of the art is that to date no possibility has been shown of converting any contaminated zinc precursors into a highly pure end product in a single operation, e.g. by solvent extraction simultaneous presence of amine-forming (copper, nickel, etc.) and non-amine-forming (iron, manganese, cations, soluble anions (Cl, SO ₄ ² "). In particular arsenal and insoluble gangue and intermediates from which pure zinc compounds can be obtained in a short, cost-effective manner n way is desired.

The inventive method described below for obtaining highly pure zinc salt solutions from impure, in particular As-containing solutions shows such a way (see also attached process diagram) and at the same time avoids the limitations or disadvantages contained in the processes discussed in the prior art. ^{Hie: at s, ^ 1} Jg starting materials 1, eg fly ash, zinc scraping, are initially used in a known manner. Ball mill dust, oxidic or rusted sulphonic zinc ores, e.g. B. Galmei, a solution 2 in an ammoniacal, ammonium salt-containing, aqueous Loü solution, optionally subjected to blowing oxygen and separated after complete dissolution of the amine-forming metals from the insoluble gangar and the non-amine-forming metals. Since, process of the invention is now characterized, gekennis characterized that the hen in the impure, ammoniakali ⁵ "zinc-containing solution, if any of the zinc compared to electropositive metals, such as copper CadmSni silver, nickel, etc., by cementation 3 with zinc dust as Metallzementat mederschJag and removed by filtration, the ammoniacal, ammonium carbonate-containing solution () thus obtained, for the purpose of zinc extraction, is brought into contact with a liquid organic cation exchanger which has a capacity of zinc which differs significantly from zero

as well as inuii wociuhu. .. ■

of the metals fixed to the resin. This 45, however, no capacity for any type of anions process has the basic disadvantage of all those who are separated in suitable aggregates, the exchange processes on resins, namely that the high zinc-laden organic phase, possibly after 1 ci,., I ,; " _ri " , _nn , | Flning going through a washing stage, with a second,

Low-zinc or zinc-free, ammoniacal / ammonium carbonate-containing Bringing solution (II) into contact for the elution 5 of the zinc, which separates the phases of the zinc Lean organic phase for renewed contact with fresh solution (1) returns and the high-purity, ammoniacal, aqueous zinc solution (II) in known way worked up.

According to the method according to the invention, it is useful, but not absolutely necessary, to use the solution (II) used for the oath in its ammonia or. Ammonia / ammonium carbonate - set the concentration higher than the solution used for dissolving (I). As a result, higher zinc concentrations are achieved in the solution (II), and the subsequent zinc extraction stage 6 can be dimensioned correspondingly smaller. If you win;. H. the pure

AUSiaU5UH_-i piuti-o ^ _u ... ,

Ion concentrations during extraction and elution cause a so-called »ion shock« of the resin, which results in alternating swelling and contraction phenomena of the resin, d. H. ultimately in a disintegration of the resin particles and an associated reduced service life. aside from that This process does not guarantee a good separation due to the high residual volumes in the intermediate bed Cations / anions, if you do not want to accept high volumes of wash water, these again, as is well known pose serious sewage problems.

Finally, there is a method in DT-OS 24 34 949 for the extraction of metals from an ammoniacal, aqueous, impure Alisgangphase and their Conversion into a liquid organic phase with subsequent extraction described. The re-extraction takes place with a likewise ammoniacal aqueous solution of higher ammonia concentration. Apart from this limiting condition, the higher ammonia concentration has in this one ΠΤ-OS described method has the disadvantage that there is zinc compound by working in a known manner Ammonia and carbon dioxide boiled away, so energy is saved correspondingly with a higher zinc concentration. Even with the alternative ancestor of the

tion of pure zinc carbonate by injecting carbon dioxide into the ammoniacal solution (II) the highest possible zinc concentration advantages. Both processes naturally produce ammonia or - when calcining the carbonate - carbon dioxide recovered by condensation 7 and used as Solution of suitable and adjustable concentration fed back into the process.

It is also useful to accelerate the dissolution process and the kinetics of the phase transitions carry out the entire process at elevated temperature when extracting and eluting. One The upper limit is given by the flash point of the organic phase, which is normally through that is used to dilute or dissolve the actual is Active ingredient used organic solvents is determined.

The anions present in the input materials accumulate in the circulating solution (I) gradually on. Their removal 8 can be done in campaigns in such a way that from time to time the Solution (I) is mixed with an excess of lime and the ammonia and carbon dioxide boil off heated. Insoluble calcium salts, e.g. B. sulfate, arsenate, phosphate, fall out here. The one left behind If chloride ions are present, the solution only contains calcium chloride, which can be safely discarded can be. If not only insignificant amounts of arsenic are present, it is advisable to add the lime residue Add ferric salt to convert arsenic into the most insoluble of its compounds, ferric arsenate transfer, which means that there are no longer any concerns about the landfill of the residue. More expedient leads one the regeneration of the solution (I) continuously in such a way that one part of the solution in Bypass with the addition of lime removes the disruptive anions continuously from the process removed. The volume of the bypass flow to be regenerated depends on the concentration of the Anions in the feed material, the selectivity of cations / anions of the available exchanger as well as the quality of the organic / aqueous phase separation. The less aqueous phase is mechanically carried over into the organic phase (so-called entrainment), the cleaner the reaction product becomes or the smaller the bypass flow can be kept.

In conclusion, it must be emphasized once again that the method according to the invention depends on the availability a cation exchanger is bound, which has the following special properties:

a) Strict selectivity between accepted cations and rejected anions. One of those strict selectivity is generally only achieved by chelating exchangers.

b) One which is predetermined by the molecular structure or the type of bond and is essentially different from zero Charge capacity, but weak bond strength for zinc.

c) No significant loading capacity for cations whose normal potential is less noble than that of Zinc is.

A chelating agent with all three properties listed above is not yet commercially available. Although z. For example, the exchanger LlX 64® (or 64 N, 70, etc.), which is already used on a large scale, has excellent selectivity for Cu ²⁴ ions, but only a minimal zinc loading capacity. Exchangers of the specification required for the method according to the invention are currently being developed at several research centers and will shortly also be available in large-scale technical quantities.

The method described offers convincing advantages over those mentioned in the prior art. It Firstly, it becomes a very pure product from any contaminated ores or intermediate products in a very short space of time of analytical quality (see the detailed example). Second, the procedure does not require any stoichiometrically proportional auxiliary or operating materials, since all chemicals (organic phase, ammonia, Carbon dioxide) are conducted in closed circuits and thus only possible losses are complementary. Thirdly, thanks to the closed-loop system, the process is environmentally friendly, as neither Washing water nor exhaust gases occur. Rather, end products are only the purest ZnO in addition to that of the Dissolution of remaining inert material of the starting materials and optionally the residues of the Anion stripping. Finally, the method can be largely automated or process computer-controlled because all stages are inevitably connected in series and all in the liquid phase get lost. This allows the personnel expenditure to be limited to monitoring the system.

The following detailed example, taken from a pilot plant, illustrates the c according to the invention Procedure, without being limited to this.

example

The raw material used was a mixture of calcined zinc ore (calamine), ball mill dust and shaft furnace oxides to disposal. The initial analysis was as follows:

Zn Cu Cn Cd CD Pb Vc Fe Mn As Mn As SiO; the Al luge ha 53.74
(Anioner 4.10
ι nb) 2.88 0.15 0.19 6.61 0.26 0.010 0.001 0.52 0.11 0.88 0.10 Cl 1.68 NHi In a two-stage
Material with a release
CO; extracted at 50 ° C That became the counter current system
eye of 68 g / l NH, and 20 g / l
and after 2 Ii from the depleted Filtered off residue.
Composition: 1.45 Delete 71 Zn Pb Al SOa ! 4.74 0.015 0.001 1.11

S1O2

8.53%

20.2 u / l

The solution was emeritus with 5 g / l zinc dust and then had the following composition:

Cu
0.009

CD
0.008

Pb

0.010 g / l

The other values remained practically unchanged [= solvent solution (I)]. The solution became a small one Pilot system, consisting of a total of 10 mixer-settler units, supplied, four of which are used to extract the solvent solution (1), two to wash the organic Phase and four were switched to EJuieren. The flow rate was approx. 40 l / h, the organic phase contained a 15% concentration of the actual

Active ingredient, dissolved in an aromatic mixture, and took up approx. 10.5 g / l Zn. It was eluted with a solution (U) with 136 g / l NH ₃ and 88 g / l CO ₂ , which after the 4-stage elution had taken up 113.2 g / l zinc. The solution was boiled, NH3 + CO2 was driven off, condensed and returned to the elution circuit for reuse. The precipitated basic zinc carbonate of the approximate formula

2Zn (OH) ₂ • ZnCO ₅

was filtered off, dried and calcined. There; obtained high-purity zinc oxide contained the following " Impurities (in ppm):

CD
0.03

Pb

1.7

Fe
0.7

Mn 0.17

Al
1.2

S1O2
32

Cl

In addition 1 mall drawings

Claims (4)

Patent claims: 1. Process for obtaining high-purity ic salt solutions from impure, especially Ai-halide solutions, which are produced by ammoniacal leaching zinc-containing materials, e.g. B. fly ash, scraping, ball mill dust, etc., were obtained by means of Solvent extraction in closed circuits, with subsequent extraction of a high-purity zinc compound, z. B. zinc oxide or carbonate, d a characterized in that the in the impure ammoniacal, Zn-containing solution (1) possibly present opposite the zinc electropositive metals, e.g. B. copper, cemented in a known manner with zinc dust and separates the ammoniacal solution (1) with a liquid organic cation exchanger with a capacity for zinc of at least 1 g / l in suitable aggregates, e.g. B. Mixer-Settler Units, extracted, the separated Zn-laden organic phase, optionally after passing through a Washing stage, with another ammonia-ammonium carbonate solution (H) to elute the zinc in Bringing contact, separating the phases, the zinc-lean organic phase for renewed contact with fresh solution (I) and the highly pure, ammoniacal, aqueous zinc solution (11) worked up in a known manner. 2. The method according to claim I ₁ characterized marked- } o that the ammonia-ammonium carbonate solution (11) used for bluing expediently has a higher ammonia or ammonia-ammonia carbonate concentration than the impure ammoniacal starting solution (1). 3. Process according to Claims 1 and 2, characterized in that the extraction and the elution process above room temperature, but below the flash point of the dilution of the extractant used organic solvent carries out. 4. The method according to claims 1-3, characterized in that one after the extraction Part of the aminonia-ammonium carbonate solution (1) branches off and one in a bypass process Subjecting treatment with steam and quick lime, using all anions, e.g. B. Arsenate, Sulphate, chloride, converted into calcium salts and removed from the process. 50