DE2621144C3 - 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 chromium, copper, zinc and Contain 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 iron 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 nickel 0 to 5, in the Middle: 1 Calcium 0 to 20, in the Middle: 4th sodium 0 to 2, in the Middle: 0 · Silica 0 to 5, in the Middle: 1 Cyanide (complex) 0 to 0.1, - - sulfite -ί- - - 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. As waste, however, they add the Environment; A deposit can only be made on hazardous waste landfills and is very costly from an economic point of view.

Therefore, at least a clean elimination or Destruction necessary, a work-up under However, recovery of the ingredients is desirable. It has already been proposed to carry out such waste

Destroy admixture in brick production. 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. Here, however, there are no selective separations of the valuable

Achieved non-ferrous metals. Most often mixed solutions

received, which are precipitated together, with the Any residue that arises is eliminated as waste sludge must become.

From DE-OS 23 40399 a method is for

Extraction of copper and zinc from non-ferrous scrap is known in which the sludge with a Ammonium carbonate solution is leached in the presence of oxygen and then from the Copper ammonium carbonate or zinc ammonium carbonate

*> leach solutions containing nat separated the metals will. Such a process is not to be used for the processing of non-ferrous metal hydroxide sludge waste, since the proportion of calcium is disruptive affects the ammonium carbonate equilibrium and also chromium hydroxide remain in the residue would.

The extraction of copper and nickel by liquid-liquid extraction from ammoniacal solutions is just as well known as the liquid-liquid ex- traction of copper at pH values of 1 to 3. These processes usually work in conjunction with a Electrolysis, the end of which is used to strip off the metal-laden organic phase. There are also processes from zinc-containing, sulfuric acid

bi ren solutions, zinc through organic liquids 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 companions Calcium, aluminum and chromium is feasible.

Attempts by selective precipitation of the non-ferrous metal compounds from the waste sludge have failed due to the co-precipitation of considerable amounts of the accompanying elements

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 thought of the collected non-ferrous metal hydroxide sludge waste in a mostly continuous process the individual non-ferrous metals, such as Separate chromium, copper, zinc and nickel side by side. This is achieved through the combination the following process steps to be carried out one after the other:

a) Chlorination of the aqueous waste sludge suspension at temperatures of 20 to 80 ° C and pH values between 4 and 13, then Acid acids with sulfuric acid up to a pH value of 1.0 to 3.0, separation of the insoluble Components and subsequent separation of the hexavalent chromium from the solution in one Fixed bed anion exchanger (at pH values of <3)

b) Separating the copper from the remaining solution by liquid-liquid-ext / action 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, the trivalent chromium is broken down to hexavalent, the soluble sulphates of copper, zinc and nickel being formed after the subsequent treatment with sulfuric acid and interfering components such as calcium sulphate, basic iron sulphate and, above all, silicic acid being separated off as insoluble residues . The usual oxidizing agents, such as hydrogen peroxide and potassium permanganate, etc. are of course also suitable for converting the trivalent chromium into the selectively separable hexavalent form, but the oxidation by chlorine has proven to be the most economical. The subsequent recovery of the chromium in its hexavalent form by means of fixed bed anion exchangers as the first process step is advantageous because if the chromium remained in its trivalent form during the liquid extraction of nickel, acidic processing was not previously possible. Through the liquid-liquid extraction of copper and zinc, which is not previously known in this successive combination of processes, and the precipitation of aluminum as hydroxide, in the last process step Nikkei is finally obtained in a highly concentrated form by liquid-liquid extraction. The separation of the disruptive accompanying elements, such as calcium, is essential in the course of the individual process steps. Iron, silicon and aluminum.

The entire Buntmetallhydroxidschlamm waste is in a suspension with a solid content of 15 wt, - transferred% and strong at a pH value of 4 to 13, preferably at pH values around the neutral point, and reaction temperatures from 20 to 8O ⁰ C under Stirring and continuous addition of alkali lye mixed with chlorine until there is no significant increase in the chromium VI content. During this chlorination, iron II, sulfite, cyanide and oxidizable organic components are oxidized at the same time. After this chlorination, sulfuric acid is added to the suspension with stirring until a pH of preferably 1.5 to 2.5 is established. This treatment with sulfuric acid results in the formation of 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 is also produced. The soluble components are separated from the insoluble residues by filtration. The insoluble residues, consisting mainly of the sulphates already mentioned and of silica, can be discarded.

This chlorinating digestion of metal hydroxide sharks Sludge with subsequent treatment by sulfuric acid is the ammoniacal leaching process Technically superior to the state of the art. While the ammoniacal leaching for nickel, Copper and zinc only leach values between 50 and 90% are achieved by the chlorinating Digestion of the metals copper, chromium, nickel and zinc recorded almost 100%.

The acidic ritrate freed from the residues is now fed to a fixed bed anion exchanger. as such anion exchanger can, for. B. a macroporous anion exchanger on styrene bast 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 dichromate ions. 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 dichromate are obtained directly or after their Processing to crystals in tanneries or for pigment production. 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.

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

Metal salt solution can have a copper content of up to 10 g / l, whereby the accompanying elements such as zinc, nickel and aluminum do not interfere in the same concentration. In three to five-stage mixer-settler for extraction after the other can be lowered depending on the l ~ Anfangskon-> concentration as the Kupfergehall the aqueous phase (raffinate) to values below 0.01 g / cc.

Mixer-settlers are box-like, / large-sized vessels, in the first part of which the mixing takes place of inorganic and organic phase takes place, while in the second part the separation of the goes in both phases. The mixing promotes the intimate contact of the liquid phase for the desired mass transfer. The organic phase is fed in countercurrent. It is beneficial before 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 200g HjSCV!) Stripped. It will be a Copper electrolyte or a copper sulfate solution with over 50 g Cu / I and less than 0.05 g / l foreign metals and a regenerated organic phase with traces of copper obtained. The resulting copper salt solution can, for. B. the The production of cathode copper is used by a copper electrolysis.

Zinc is separated from this solution, which has now been freed of 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, depending on the content of di- (2-ethyl-hexyl) phosphoric acid, can contain 10 to 30 g / l zinc. is in d; ; i Mixer-settler stages using a dilute sulfuric acid with 100 to 200 g H ₂ SO ₄ /! stripped in countercurrent. The stripping diet has zinc concentrations of over 100 g Zn / I and can be used in a known manner, e.g. B. be fed as an electrolyte, a zinc electrolysis.

Processes are known. Recover zinc from relatively pure, sulphatic solutions or sewage 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 drainage 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 some of the nickel as well as 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 traces of metal chromium, 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. The sodium form of di- (2-äthylhexyi-) phosphoric acid in dilution with the free acid of this compound and high-boiling aromatic solvents, such as, for. B. trimethylbenzene or xylene have been proven. A disadvantage of the above-mentioned sodium di- (2-ethy! -Hexyl) phosphate is that it is readily soluble in water but poorly soluble in organic diluents Stripping off a homogeneous phase is created. Surprisingly, it has been found, however, in this process step that can be carried out without solubilizers and without excess of di- (2-ethylhexyl) phosphoric acid, when the dilution with the high-boiling aromatic solvent more than 40 by volume ⁰ '. Contains di- (2-ethyl-hexyl) phosphoric acid. If these conditions are met, distributions of nickel are achieved that 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-setting stages are sufficient to prevent the nickel content of the aqueous solution (raffinate) from occurring beforehand to bring approx. 6 g / l to contents <10 m ^ / l. The organic phase fully loaded with nickel (30 to 40 g Ni / I) is stripped in two mixer-settler stages through concentrated hydrochloric acid or hydrochloric acid-containing NiCl ^ solution or through dilute sulfuric acid or sulfuric acid-containing nickel sulphate solution or amidosulphonic acid-containing solutions so that one can directly receives highly concentrated nickel salt solutions. Depending on the application of the stripping acid, either solutions of nickel chloride, nickel sulfate or nickel sulfamate are obtained. These solutions or the salts that can be crystallized from them can be used directly in the electroplating industry for nickel plating.

The process 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 ₇ O; 13 Cu; 1.7 Cr; 13 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 65 by adding sodium hydroxide solution. The introduction rate was 260 parts by volume of Chloigas 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, combined the first wash water with Filtral and the Discard residue.

18 parts by weight of filter return land with 67 were obtained Wt% solids; 0.1 wt% Cr; 0.05 wt% Cu; 0.03 wt% Ni; 0.02 wt% Zn; 14 wt% Ca; 3 wt .-% κι SiO. and 7.5% by weight of Fc and 280 parts by weight of raw solution with 6.7 g Cr / l: 6.0 g Cti / I: 5.2 g Ni / I: 12 g Zn / I: l.2gAI / l; - ^ 0.1 g Fe / I and 0.6 g SiO./l.

To separate off the hexavalent chromium, the crude solution was passed through a column ι ί within 2 hours led, which with 22 parts by volume of a schwaehbasisehen Anionenausiauschers based on styrene in the SOi shape was filled. The anion exchanger was by the chromium-Vl-Mcnge contained in the raw solution almost fully loaded. _> m

According to the ChronUrennsture, the filtrate of the crude solution contained 0.08 g / l chromium-HI and <0.1 g SiO ₂ / l. while the other components remained almost unchanged.

The chromium-laden ion exchanger became-> -, next fully loaded with a second batch of crude solution to remove impurities from the first batch To displace as much as possible, then rinsed with water and finally through 44 parts by weight of a 6% by weight NaOH eluted. The w chromium-rich fractions running off at pH 3 to 8 contained more than 95% of the Amount of chromium used in a concentration of 20 to 60 g / l Cr.

The dechromed filtrate was then fed to a solvent extraction step to extract the copper, j-> A 20% by volume solution of benzophenone 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 l mixer room and 4 l settler room. The flow rate of the organic phase was on average 12.5 l / h and that of the to be extracted inorganic phase 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 0.002 g / l Cu contained. Between the second and third stage, the pH of the aqueous phase was adjusted by adding NaOH set to 2.0.

To strip off the amount of copper, the copper-laden organic phase was _{brought into contact with a sulfuric acid containing 140 g / l H 2} SO ₄ in three identical mixer-settler stages one after the other. The copper content of the organic phase fell to 0.1 g / l and the copper content the acidity rose to 82 g / l. This: so-called stripping diet also contained 0.005 j Ni / I; <0.001 g Al / l; 0.001 g Zn / I; <0.00lg Cr / I around <0.l gCI / l.

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

In order to separate the zinc, this solution was mixed with a large number of mixer-settler stages (design as for copper) Extraction solution of 20% by volume of di- (2-ethyl-xylphosphoric acid) in low-aromatic (<0.1 "/ o) kerosene (Sp 192-254) treated. The flow rate of the inorganic phase was 10.0 l / h and that there organic phase 8.0 l / h. whereby / iilet / i eiiu / inkbcladenc phase with approx. 15 g Zn / I was obtained.

After the second extraction stage, the pH of the aqueous solution was adjusted to i. ( Using NaOII).

After the fourth Level 0.1 g Zn / I can be determined.

To strip the zinc from the zinc-laden organic phase, it was mixed with sulfuric acid with 200 g of H ₂ SO ₄ /! treated The zinc content of the organic phase fell aiii about 0.1 g / l, that of the inorganic phase reached 102 £ Zn / l. No nickel and no chloride could be detected in the stripped zinc.

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

The resulting precipitation, especially de < Aluminum, was separated by decantation and repeated decantation washing, producing a aqueous solution of pH 4.5 with 4.5 g Ni / I chalter, which also contains alkali metal chloride and sulfai contained.

This solution was also subjected to a third solvent extraction with a flow rate of 10 l / h step fed to the nickel separation. This Solven textraction consisted of three stages as for the previous metals. The extraction agent used was a 4C neutralized with sodium hydroxide solution to pH 6.5 % By volume solution of di (2-ethyl-hexyl) phosphoric acid in a solvent rich in aromatic compounds (such as trimethylbenzene), Boiling range 172-192 ° C, used.

The flow rate of the organic phase was approx. 1.5 l / h. In the organic phase, after three Classify a nickel content of 29.6 g / l. while there: raffinate nickel contained <0.01 g / l nickel.

To recover the nickel, the nickel was loaded ^ ¹ sne organic phase, also in three mixer-settler stufer by stripping with 30 wt .-% HCl treated In this per hour 0.34 I NiC ^ solution with 130 g of Ni /! obtain.

Claims (5)

Claims; 1. Process for the processing of non-ferrous metal hydroxide sludge waste, which is classified as non-ferrous metals in contain essential chromium, copper, zinc and nickel, with recovery of the non-ferrous metals by separating the individual non-ferrous metals from one another, 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 of 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) Separating the zinc from the remaining chloride- and sulfate-containing solution by 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) the sodium salt of di- (2-ethyl-hexyl-) as the extractant phosphoric acid used in dilution with a high-boiling aromatic solvent where the proportion of di (2-ethyl-hexyl) phosphoric acid in the mixture is> 40% by volume. 4. The method according to claim 1, characterized in that in process step b) dilutions of substituted hydroxy-benzophenone oximes with petroleum are used as the extraction agent will. 5. The method according to claim 1, characterized in that in process step c) di- (2-ethyl-hexyl) phosphoric acid diluted with petroleum is used as the extractant. Industry, contain essentially the following components (data in% by weight):