DE2621144B2 - Process for processing non-ferrous metal hydroxide sludge waste - Google Patents

Description

The invention relates to a method for processing non-ferrous metal hydroxide sludge waste, which is used as non-ferrous metals essentially contain chromium, copper, zinc and nickel, with recovery of the non-ferrous metals by separating the individual non-ferrous metals from one another.

The hydroxide sludge waste, as it is in galvanic processes and in non-ferrous metal processing

water 40 to 90, in the Middle: 70 5 irons 0 to 10, in the Middle: 2 aluminum 0 to 2, in the Middle: 0.5 Chrome (III) 0 to 10, in the Middle: 2 zinc 0 to 10, in the Middle: 2 copper 0 to 5, in the Middle: 1 ίο nickel 0 to 5, in the Middle: 1 Calcium 0 to 20, in the Middle: 4th sodium 0 to 2, in the Middle: 0.5 Silica 0 to 5, in the Middle: 1 Cyanide (complex) 0 to 0.1, - - 15 sulfite + _ - Carbonate 0 to 5, - - chloride + sulfate +

This hydroxide sludge waste contains a lot of water and insufficient amounts of valuable metals to to be able to smelt this waste economically. However, they would pollute the waste as waste Environment; it can only be deposited in hazardous waste landfills and is very costly from an economic point of view.

Therefore, at least a clean elimination or Destruction necessary, but processing with recovery of the ingredients is desirable.

It has already been proposed to destroy such waste by adding it to the brick-making process. Process methods from hydrometallurgy and waste water treatment are also known which however, the recovery of one or two is unsatisfactory, but hardly more than one Allow ingredients.

There are also numerous processes for separating metals in fixed-bed ion exchangers or for removal from wastewater solutions. However, there are no selective separations of the valuable ones Achieved non-ferrous metals. Usually mixed solutions are obtained which are precipitated together, the Any residue that arises must be disposed of as waste sludge.

DT-OS 23 40 399 describes a process for the extraction of copper and zinc from non-ferrous scrap known in which the sludge with an ammonium carbonate solution in the presence of oxygen is leached and then from the copper ammonium carbonate or zinc ammonium carbonate containing leach solutions, the metals are separated. Such a procedure is not for that Processing of non-ferrous metal hydroxide sludge waste to be used, as the proportion of calcium has a disruptive effect on the ammonium carbonate balance and moreover, chromium hydroxide would remain in the residue.

The extraction of copper and nickel by liquid-liquid extraction from ammoniacal solutions is just as well known as the liquid-liquid-Ex-

Bo traction of copper at pH values from 1 to 3. This Process mostly work in connection with an electrolysis, whose end electrolyte is used to strip the metal-laden organic phase is used. There are also processes from zinc-containing, sulfuric acid

b5 ren solutions, zinc through organic liquids too extract and strip off by the final electrolyte of an electrolysis. All of these described Extraction process has in common that the separating

only in the absence of the accompanying elements iron, Calcium, aluminum and chromium is feasible.

Attempts by selective precipitation of the non-ferrous metal compounds from the waste sludge are on Co-precipitation of considerable amounts of the accompanying elements failed.

Compared to these known methods and attempts to recover nonferrous metals, in which only individual elements were obtained in an economically justifiable manner, the invention is based on the idea of using the collected non-ferrous metal hydroxide sludge waste in a mostly continuous manner In the process, the individual non-ferrous metals such as chromium, copper, zinc and nickel are next to each other to separate. This is achieved by combining the following process steps to be carried out one after the other:

a) Chlorination of the aqueous waste sludge suspension at temperatures from 20 to 80 ⁰ C and pH values between 4 and 13, subsequent acidification with sulfuric acid up to a pH value of 1.0 to 3.0, separation of the insoluble constituents and subsequent Separation of the hexavalent chromium from the solution in a fixed bed anion exchanger (at pH values of <3)

b) Separating the copper from the remaining solution by liquid-liquid extraction in itself known way

c) Separating the zinc from the remaining chloride and sulfate-containing solution by liquid extraction

d) Precipitation and separation of the aluminum as hydroxide from the remaining solution and Separation of the nickel from the filtrate by liquid-liquid extraction

and working up the individual non-ferrous metal fractions obtained according to process step a) to d) as such known way.

With this combination of processes, a decomposition of the trivalent chromium becomes a hexavalent one achieved, whereby after the subsequent treatment with sulfuric acid the soluble sulfates of copper, zinc and nickel and, as insoluble residues, interfering components such as calcium sulfate, basic Iron sulfate and especially silica are separated. To convert the trivalent chromium into the selectively separable hexavalent form are of course also suitable for the usual oxidizing agents, such as Hydrogen peroxide and potassium permanganate, etc., however, has proven to be the oxidation by chlorine proven most economical. The subsequent extraction of chromium in its hexavalent form by Fixed bed anion exchanger as the first process step is advantageous because the remaining Chromium in its trivalent form in liquid-liquid extraction. Nickel would interfere and thereby acidic work-up was previously not possible. Through the liquid-liquid extraction of copper and zinc, such as them in this successive combination of processes hitherto unknown, and the precipitation of aluminum as hydroxide will eventually last Process step obtained by liquid-liquid extraction Nikkei in a highly concentrated form. Essential in the course of the individual process steps is the separation of the disturbing accompanying elements, such as calcium, Iron, silicon and aluminum.

The entire colored metal hydroxide sludge waste is put into a suspension with a solids content of 15% by weight and at a pH of 4 up to 13, preferably at pH values around the neutral point, and the reaction temperatures of 20 to 80 ° C with vigorous stirring and continuous addition of Alkaline potassium hydroxide solution is mixed with chlorine until there is no significant increase in the chromium VI content. During this chlorination, iron (II), sulphite, cyanide and oxidizable organic components are produced at the same time oxidized. After this chlorination, the suspension is mixed with sulfuric acid with stirring until a pH of preferably 1.5 to 2.5 is established. As a result of this treatment with sulfuric acid, they are formed the sulphates of copper, nickel, zinc and aluminum. Dichromate is formed at the same time. Iron and calcium are converted into compounds that are sufficiently insoluble for practical use, and insoluble silicic acid also falls at. The soluble components are separated from the insoluble residues by filtration. The insoluble residues, consisting mainly of the sulphates already mentioned and of silicic acid, can be discarded.

This chlorinating digestion of metal hydroxide-containing sludge with subsequent treatment by Sulfuric acid is technically superior to the prior art ammoniacal leaching processes. While the ammoniacal leaching for nickel, copper and zinc only leaches between 50 and 90% are reached, the metals copper, chromium, nickel and zinc are converted by the chlorinating digestion almost 100% recorded.

The acidic filtrate freed from the residues is now fed to a fixed bed anion exchanger. as such anion exchanger can, for. B. a macroporous anion exchanger based on styrene with weakly basic tertiary amino groups can be used. This has a particularly high resistance to oxidation. Such an anion exchanger is now made with the solutions containing sulfuric acid dichromate ions loaded. The solutions contain up to 10 g / l chromium-VI as dichromations. With at least two exchangers connected in series that use the sulfate or chloride form of the resin described are filled, dichromate is collected and then eluted with alkali (4 to 8% by weight). It eluates with 100 to 200 g / l alkali chromate or alkali metal dichromate are obtained directly or after their Processing to crystals in tanneries or for pigment production use. Can continue the resulting chromate or dichromate can be used as a preliminary product for the production of chromium oxide.

The chromium-free raffinate leaking from the exchange columns is now largely from before Colloidally dissolved silica freed, namely in the liquid-liquid extractions that now follow Formation of non-separating emulsion layers would interfere.

Under liquid-liquid extractions is the exchange of metal ions or hydrogen ions between understood two liquid, immiscible phases, one of which is an aqueous phase and the other is an organic solvent phase. In the following separation of copper by a such liquid-liquid extraction are the known extraction agents such. B. Dilutions of substituted hydroxy-benzophenone oximes with petroleum. The pH of the aqueous phase should be be kept between 1.5 and 2.5. The sour

Metal salt solution can have a content of up to 10 g / l copper, with the accompanying elements such as Do not interfere with zinc, nickel and aluminum in the same concentration. In three to five mixer set-up levels for the Extractions one after the other can, depending on the initial concentration, thus reduce the copper content of the aqueous phase (Raffinate) can be reduced to values below 0.01 g / 1.

Mixer-settlers are box-like, two-part vessels, in the first part of which the inorganic and organic phases are mixed ι ο takes place, while in the second part the separation of the two phases takes place. The mixing promotes intimate contact with the liquid phase for the desired exchange of substances. The organic Phase guided in countercurrent. It is advantageous, especially with chloride-containing loading solutions, the copper-laden ones organic phase after leaving the extraction stages with water, a sodium sulfate or wash a copper sulfate solution. Then the organic phase is in a three-stage Mixer-settler system with a copper end electrolyte (100 to 200 g H2SO4 / I) stripped. There is a copper electrolyte or a copper sulfate solution with over 50 g Cu / l and less than 0.05 g / l foreign metals and a regenerated organic phase with traces of copper obtain. The resulting copper salt solution can, for. B. the production of cathode copper by a copper electrolysis to serve.

Zinc is separated from this solution, which has now been freed from chromium and copper, by liquid-liquid extraction, using the mixer-settler apparatus mentioned above. Di (2-ethyl-hexyl) phosphoric acid diluted with petroleum is particularly suitable as an extraction agent. After three to five mixer-settler stages, the zinc content in the raffinate is brought to a level below 0.01 g / l. The pH of the incoming inorganic aqueous phase should be kept at 2 to 3. The loaded organic phase, which can contain 10 to 30 g / l zinc depending on the content of di- (2-ethyl-hexyl) phosphoric acid, <to is in three mixer-settler stages by a dilute sulfuric acid with 100 to 200 g H ₂ SO ₄ /! stripped in countercurrent. The Abstreifeluat has zinc concentrations of over 100 g Zn / 1 and can in a known manner, for. B. be fed as an electrolyte, a zinc electrolysis.

Processes are known to recover zinc from relatively pure, sulphatic solutions or waste waters or to extract zinc as a chloro complex from high chloride solutions, but it was not known to extract zinc in addition to nickel, aluminum from sulfatic solutions so that practical Heavy metal-free stripping evacuates with a high zinc sulfate content can be obtained.

After the chromium, copper and zinc have been separated off, the aqueous raffinate may still contain traces these elements as well as the main amounts of aluminum and nickel. To prepare the solution for the Nickel separation and the separation of the aluminum, the pH of the solution is t> o by adding soda and / or lime adjusted to 3.5 to 4.5. This precipitation causes a partial co-precipitation of the nickel and the Traces of chromium, copper and zinc. After decantation and filtration, the bulk of the is obtained in the filtrate Nickel. The residue is treated with alkali, which leaves the freshly precipitated aluminum hydroxide practically completely as sodium aluminate in solution, while the acids of metal! Chrome, copper. zinc and nickel remain undissolved as carbonates or hydroxides and can be returned to process step a) (chlorination) for reprocessing.

Nickel is now separated from the first filtrate of the hydroxide precipitation by liquid-liquid extraction. as The sodium form of di (2-ethylhexyl) phosphoric acid in dilution with has proven to be a suitable extraction agent the free acid of this compound and high-boiling aromatic solvents, such as. B. trimethylbenzene or xylene proved. A disadvantage of the above-mentioned sodium di- (2-ethyl-hexyl) phosphate is that it is well soluble in water but poorly soluble in organic diluents. Using So-called solvent is achieved that both when loading and after stripping a homogeneous Phase arises. Surprisingly, however, it has been found in this process step that without Dissolving agent and without an excess of di- (2-ethylhexyl) phosphoric acid can be used if the dilution with the high-boiling aromatic solvent is more than 40% by volume of di- (2-ethyl-hexyl) contains phosphoric acid. If these conditions are met, distributions of nickel are achieved that are one allow economic use. It has been shown that in the extraction of the nickel-containing aqueous solution with the sodium salt of di- (2-ethylhexyl) phosphoric acid in appropriate dilution practically two mixer-settler stages are sufficient to reduce the nickel content of the aqueous solution (raffinate) of previously to bring approx. 6 g / l to levels <10 mg / l. The organic phase fully loaded with nickel (30 to 40 g Ni / 1) is concentrated through two mixer-settler stages Hydrochloric acid or NiCb solution containing hydrochloric acid, or by means of dilute sulfuric acid or nickel sulphate solution containing sulfuric acid or amidosulphonic acid Solutions stripped off so that highly concentrated nickel salt solutions are obtained directly. ] e according to application the stripping acid is optionally solutions of nickel chloride, nickel sulfate or nickel sulfamate won. These solutions or the salts that can be crystallized from them can be used directly in the electroplating industry Nickel plating can be used.

The process which proceeds according to the invention gives high yields (98.5 to 99.5%) of the in the Waste hydroxide sludge contained valuable non-ferrous metals. Those remaining after the procedure Solutions only contain traces of these elements. Through the chlorinating, sulfuric acid leaching and the associated separation of the non-ferrous metal elements is further achieved that the amount of waste sludge on a Third of the original amount is reduced.

The method according to the invention is explained in more detail using the following exemplary embodiment.

example

100 parts by weight of moist electroplating sludge with the analysis in% by weight: 69.6 H ₂ O; 1.5 Cu; 1.7 Cr; 1.3 Ni; 3.0 Zn; 1.4 Fe; 0.4 Al; 2.6 Ca; 0.7 SiO ₂ were mixed with 80 parts by weight of water. Chlorine gas was introduced with constant stirring at 50 ° C. and while maintaining a pH value of 6.5 by adding sodium hydroxide solution. The rate of introduction was 260 parts by volume of chlorine gas per hour, measured at room temperature. A total of 5 hours was initiated and 24 parts by weight of 32% sodium hydroxide solution were consumed. The end point was determined by measuring the chromium VI content in the suspension.

After completion of the oxidation, 23 parts by weight of concentrated sulfuric acid became within 30 minutes metered in and thus adjusted the pH to 2.5. After a further 30 minutes the suspension became filtered and washed with about 70 parts by weight of water, the first wash water combined with the filtrate and the Discard residue.

18 parts by weight of filter residue with 67% by weight of solids were obtained; 0.1 wt% Cr; 0.05 wt% Cu; 0.03 wt% Ni; 0.02 wt% Zn; 14 wt% Ca; 3% by weight SiO ₂ and 7.5% by weight Fe and 280 parts by weight crude solution with 6.7 g Cr / I; 6.0 g Cu / I; 5.2 g Ni / 1; 12 g Zn / 1; 1.2 g Al / l; <0.1 g Fe / 1 and 0.6 g SiO ₂ / l.

To separate off the hexavalent chromium, the crude solution was passed through a column within 2 hours led, which with 22 parts by volume of a weakly basic Styrene-based anion exchanger was filled in the SO4 "form. The anion exchanger was almost fully loaded due to the amount of chromium VI contained in the raw solution.

After the chromium separation stage, the filtrate of the crude solution contained 0.08 g / l chromium III and <0.1 g SiO ₂ / l, while the other components remained almost unchanged.

The chromium-laden ion exchanger was first filled with a second batch of crude solution loaded in order to displace impurities from the first batch as much as possible, then rinsed with water and finally cluted by 44 parts by weight of 6% by weight NaOH. Those running at pH 3 to 8 chromium-rich fractions contained more than 95% of the amount of chromium used in a concentration of 20 to 60 g / l Cr.

The dechromed filtrate was now fed to a solvent extraction step to extract the copper, A 20% by volume solution of betizophenone oxime in low-aromatic (<0.1%) Kerosene with a boiling range of 192-254 ° C is used. Four connected in series served as apparatus Mixer-settler with 1 1 mixer room and 4 1 set room each. The flow rate of the organic phase was on average 12.5 l / h and that of the inorganic phase to be extracted was 10.0 l / h.

The Cu concentration of the organic phase reached about 4.8 g / l, while the so-called raffinate, the aqueous phase extracted in four stages contained 0.002 g / l Cu. Between the second and third stage was the pH of the aqueous phase was adjusted to 2.0 by adding NaOH.

In order to strip off the amount of copper, the copper-clad organic phase was brought into contact _{with 140 g / l HiSO 4 in three identical mixer / siphons one after the other with sulfuric acid.} The copper content of the organic phase fell to 0.1 g / l and the copper content of the acid rose to 82 g / l. This so-called stripping element also contained 0.005 g Ni / I; <0.001 g Al / 1; 0.001 g Zn / I; <0.001 g Cr / I and <0.1 gCI / l.

The raffinate solution from the copper extraction now still contains 12 g Zn / l; 5.2 g Ni / I; 1.2 g Al / l and traces of Cu, Cr, Fe and SiO ₂ .

To separate the zinc, this solution was mixed in four mixer-settler stages (design as for copper) with an extraction solution of 20% by volume of di- (2-ethyl-hexyl) phosphoric acid in low-aromatic (<0.1%) Kerosene (Sp 192-254) treated. The flow rate of the inorganic phase was 10.0 l / h and that of the organic phase was 8.0 l / h, resulting in a ι ¹ ; zinc-laden phase with approx. 15 gZn / l was obtained.

After the second extraction stage, the pH of the aqueous solution was adjusted to 3.0 with NaOH set.

In the "dezincified" raffinate, 0.1 g Zn / I could still be determined after the fourth 2 (i stage.

To strip the zinc from the zinc-laden organic phase, it was mixed with sulfuric acid with 200 g of H ₂ SO ₄ /! In three mixer-settler stages. treated. The zinc content of the organic phase fell to approx. 0.1 g / l, that of the inorganic phase reached 102 g Zn / l. No nickel and no chloride could be detected in the zinc scrap.

The raffinate, which has now been de-zincified, decoppered and dechromed, was mixed with 10% soda solution at 50 ° C jn was added until a pH of 4.5 was reached.

The ensuing precipitation, in particular of aluminum, was separated by decantation and washing with decantation repeated, whereby an aqueous solution ^of pH γ- obtain 4.5 g 4.5 Ni / I, was still further alkali metal chloride and sulphate containing .

This solution was also subjected to a third solvent extraction step with a flow rate of 10 l / h fed for nickel separation. This solvent extraction consisted of three stages as for that previous metals. A 40 neutralized with sodium hydroxide solution to pH 6.5 was used as the extractant Vol.% Solution of di (2-ethyl-hexyl) phosphoric acid in a solvent rich in aromatic compounds (such as trimethyl-4-, benzene), boiling range 172-192 ° C.

The flow rate of the organic phase was approx. 1.5 l / h. In the organic phase, a nickel content of 29.6 g / l was established after three stages, while the nickel raffinal contained <0.01 g / l nickel.
To obtain the nickel, the nickel-laden organic phase was also treated in three mixer-settler stages by stripping with 30% by weight HCl. This gave 0.34 l of NiCl ₂ solution containing 130 g of Ni / l per hour.

Claims (5)

Patent claims: 1. Process for the processing of non-ferrous metal hydride sludge waste: n, those as non-ferrous metals essentially chromium, copper, zinc and nickel contain, with recovery of the non-ferrous metals by separating the individual ßuntmeialle from each other, characterized by the combination of the following process steps to be carried out one after the other: a) Chlorination of the aqueous waste sludge suspension at temperatures from 20 to 80 ⁰ C and pH values between 4 and 13, subsequent acidification with sulfuric acid up to a pH value of 1.0 to 3.0, separation of the insoluble constituents and subsequent Separation of the hexavalent chromium from the solution in a fixed bed anion exchanger (at pH values of <3) b) Separating the copper from the remaining solution by liquid-liquid extraction in an known way c) Separation of the zinc from the remaining solution containing chloride and sulfate by means of liquid-liquid extraction d) Precipitation and separation of the aluminum as hydroxide from the remaining solution and Separation of the nickel from the filtrate by liquid-liquid extraction and working up the individual non-ferrous metal fractions obtained according to process step a) to d) in an known way. 2. The method according to claim 1, characterized in that the chlorination in the process step a) takes place at pH values of 6 to 7. 3. The method according to claim 1, characterized in that in process step d) as the extraction agent the sodium salt of di- (2-ethyl-hexyl) phosphoric acid in dilution with a high-boiling one aromatic solvent is used, the proportion of di- (2-äthyI-hexyl-) phosphoric acid is> 40% by volume in the mixture. 4. The method according to claim 1, characterized in that in process step b) as the extraction agent Dilutions of substituted hydroxy-benzophenone oximes with petroleum used will. 5. The method according to claim 1, characterized in that in process step c) as the extraction agent Di (2-ethyl-hexyl) phosphoric acid is used in dilution with petroleum. Industry, contain essentially the following components (data in% by weight):