DE3014315A1 - Sepn. of metals from soln. by cementation - esp. for purificn. of neutral leaching liq. contg. zinc prior to electrolytic winning of zinc - Google Patents

Abstract

The initial soln. (21) is fed together with a cementation agent (24) into a vibrating reactor (1). The purified soln. (23) is then rapidly sepd. from the cementation prod., pref. within max. 5 minutes, using a flocculant (28) and a centrifuge (2), or a filter. flocculant (28) is pref. an acrylamide polymer with mol.wt. of 1-30 millions, used as an 0.01-0.2% soln. and adding 5-25 mg flocculant to each litre of soln (23). Cementation is pref. at 85-95 deg.C using 6-15 mg/l of Sb203, and Zn shot as agent (24). A continuous centrifuge (2) is pref. employed. Esp. where liq. (21) is a neutral ZnSO4 soln. obtd. from roasted zinc blende, contg. other metals. Soln. (21) contained 150 g/l Zn, plus Cu, Cd, Co, and Ni, and was fed with Sb203 (22) into heated tank (3), and then pumped (19) through the two oscillating tubes (8,9) of reactor (1), which is fed with Zn shot (24). Slotted plates (10,11) retain the cementation prod., but the purified soln. (23) contains Zn shot, which is partly removed in sedimentation tank to obtain soln (27) fed with flocculant (28) and entering centrifuge (2). Solids (29) leave via exit (16), but the pure soln. (30) is fed via tanks (32, 33, 37) to electrolysis cell (39) for winning Zn cathodes (40).

Description

Annex to the patent application by

Klöckner-Humboldt-Deutz Aktiengesellschaft Procedure and device for removing metals from metal salt solutions The invention relates to a method and a device for removing metals from metal salt solutions, especially for cleaning zinc neutral eyes for electrolysis, by cementation in the vibrating reactor and subsequent separation of cementate and purified solution.

The zinc blende concentrates roasted during leaching, for example Accruing metal salt solution or zinc neutral lye contains in addition to the dissolved zinc sulphate other valuable metals that have dissolved, such as copper, cobalt, nickel and cadmium.

A direct use of the zinc neutral for electrolytic Zinc deposition is not possible because the electrochemically more noble impurities Cu, Co, Ni, -Cd, etc.

be deposited cathodically together with the zinc, whereby the Cathode quality is severely impaired. At the same time, however, you can also get through Lowering the hydrogen overvoltage significantly reduces the current yield. The additional Metals in the metal salt solution represent impurities and must be separated before further processing.

There are essentially four ways of cleaning metal salt solutions Process, a chemical precipitation, the electrochemical deposition, an ion exchange (Solvent extraction) as well as cementation, whereby these types of process are also combined can be.

From the specialist journal Erdmetall "31 (1978) pages 170 to 175 is a process known with the uncleaned zinc neutral lye by multi-stage cementation is treated in the vibrating reactor. The separation of cementate and purified solution is effected in each case by filtration using filter presses.

Cementation tests in the swing reactor have shown that after very short residence times of only 2 minutes, the precipitation by cementation so far has progressed that the contents of copper, nickel and cobalt in the purified Solution below 0.1 milligrams per liter, while however the cadmium content decreases to 0.2 milligrams per liter. The essential acceleration of the cementation process however, the use of the oscillating reactor evidently has a disadvantageous effect on the subsequent one Separation of cementate and purified solution by filtration in a filter press off as much of the precipitated metal can go.

cement back in solution That is partly due to the huge Dwell time of the cementate in the filter presses, on the other hand, causes the accelerated Cementation in the vibrating reactor also results in a significantly faster re-dissolution of the Cementate. The explanation for this can be assumed that the cementation conditions exert a significant influence on the form of the cementate eristallization and thus also strongly influence the properties with regard to the redissolution.

The use of filter presses to separate cementate and purified Solution also shows the disadvantage that gel-like zinc hydroxides (Zn (OH) 2) formed or other metal hydroxides, such as Ni (OH) 2 or Cd (OH) 2, the filters through their sticking Quickly render the effect unusable.

The invention is therefore based on the object of a method and to show a device for removing metals from metal salt solutions, with which in particular the redissolution of the metal cement or of the cementate largely avoided and at the same time a reoxidation of the cementate as a result of contact with oxygen is prevented, while at the same time improving the separating effect between cementate and purified solution and economic optimization of the overall process. The object of the invention is achieved in that the separation takes place in a quick disconnect device. This shows a technical teaching with a one-step process that is particularly economical and easy Way, for example, zinc neutral eyes can be cleaned for electrolysis purposes.

In an advantageous embodiment of the invention, in the quick disconnect device an average contact time between the cleaned solution and cementate of 5 minutes not exceeded. By this measure, the redissolution of the cementate limited to an economically justifiable framework.

Another advantageous embodiment of the invention provides that a centrifuge is used as a quick separation device and a suitable flocculant is used is used for coagulation. Using a centrifuge for example one Solid bowl screw centrifuge for separating cementate and purified solution in connection with the use of strongly anionic flocculants setting average residence times of the purified solution of approx. 5 Minutes and less and therefore also a high separation effect in contrast to the known filter presses, in which an average solids residence time of approx up to 10 hours is common. Compared to the known prior art from centrifuge technology can, surprisingly, an almost complete separation of cementate and purified solution can be achieved. The use of a solid bowl screw centrifuge offers the further advantage that the residue separated off in it is compared to one another conventional process has very low residual moisture of less than 30 S6.

The ready-to-use, purified solution has contents of <0.2 mg / l Cu, <0.4 mg / l Cd, <0.1 mg / l Co and <0.05 mg / l Ni.

In a further embodiment of the invention, as an expedient measure provided, the quick separation in a rotary filter press or in a pressure filter, both to be carried out with continuous discharge of solids. This achieves that with a suitable choice of the filter medium a complete separation of the Metal gels or the metal hydroxides such as Zn (ob) 2 Oo (OH) 2, Cd (OH) 2 and Ni (OH) 2 takes place and thus a particularly high degree of purity of the solution in just one cleaning stage can be achieved.

An expedient embodiment of the invention also provides that the purified solution is fed to a post-cementation device, the a filtration device is connected downstream. This measure will also highest degrees of purity of 0.05 mg / l Cu, 0.15 mg / l Cd, 0.08 mg / l Co and 0.05 mg / l Ni obtained for electrolysis purposes.

Since the cleaned solution coming from the quick disconnect stage is already is very clean, it is the post-cementation device and the downstream one Filtration device to a fine cleaning stage with only very little effort of expensive cementing agents such as zinc dust.

In a further advantageous embodiment of the invention, the filter residue from the filtration stage before the metal salt solution enters the vibrating reactor mixed in. Since this filter residue contains a lot of zinc, its reuse increases the zinc output of the overall process and thus significantly improves the process economy.

According to a further advantageous embodiment of the invention post-cementation was carried out in a vibrating reactor. Cementation in a vibrating reactor is known to have the advantage of being able to control the process at the same time high throughput rates and low space requirements.

In an expedient embodiment of the invention, the vibrating reactor is attached a settling tank and a quick disconnect device, preferably a solid bowl screw centrifuge connected, which is associated with a reduction in the consumption of zinc granules.

In a further embodiment of the invention, the device also has a post-cementation device, preferably a vibrating reactor, the discharge side is connected to a filtration device. This ensures the highest possible level of security and quality maximization of the electrolyte guaranteed.

The invention is advantageously improved in that the quick disconnect device arranged below the vibrating reactor feeding them and via lines with the Feed pipe of the quick disconnect device directly - or via a sedimentation container connected is. With this arrangement according to the invention, a feed pump can be used between the cementation device and the quick disconnection device and thus dispensed with Costs are saved.

Further details, features and advantages of the invention result from the following explanation of several shown schematically in the drawings Embodiments for carrying out the method according to the invention.

It. 1 shows a system for single-stage zinc lye cleaning for electrolysis.

Fig. 2 is a further representation of a zinc lye cleaning with main and post-cleaning stage.

FIG. 3 shows a representation as in FIG. 2, with a vibrating reactor in the post-cleaning stage is used.

The system shown in Figure 1 with the device according to the invention A vibrating reactor 1 is the main unit for carrying out the process as well as a quick disconnect device 2, as ancillary units a feed container 3 and a settling tank 4. The units are connected to each other via the lines 5, 6 and 7 connected. The vibrating reactor 1 has two tubes 8, 9, from one The unbalance drive lying in the longitudinal direction is set in circular oscillations will.

At the end of the tubes there are slotted disks 10, 11. The quick disconnect device 2 is shown as a solid bowl screw centrifuge with a drum jacket 12 and a screw conveyor 13 and has a feed pipe 14, a liquid discharge 15 and a Residue discharge-16. The feed container 3 is provided with an agitator 17 and one Heating coil 18 equipped. In the lines 5, 6 there are pumps 19 and control valves 20 provided.

When operating the system according to FIG. 1, metal salt solution 21, -zum Example zinc neutral lye with, for example, 150 g / l.Zn, referred to as raw lye, with a content of 800 mg / l Cu, 500 mg / l Cd, 10 mg / l Co and 20 mg / l Ni in the feed container 3 supplied. As cementation aids 22 there are additives such as Antimontatrat or also Sb203 in such an amount that an antimony concentration of 20 mg / l in the purified solution 23 at the outlet end of the tubes 8 and 9 of the Vibrating reactor 1 is kept approximately constant.

With the help of the heating coil 18, the temperature of the raw liquor 21 brought to about 90 to 95 0C in the feed container 3.

At a pH between 3 to 4.5, the raw liquor 21 is about the Line 5 into the tubes 8 and 9 of the oscillating reactor 1 through the action of the pumps 19 promoted. Throughput and liquid level in the swing reactor 1 are controlled by pumps 19 and control valves 20. In the tubes 8, 9 of the oscillating reactor 1 there is the cementation agent 24, which is supplied to the pipes via the metering element 25 8 and 9 is fed continuously. The cementation agent 24 is in the present case about zinc granules with a diameter of about 10 to 15 millimeters, which are added in such an amount that the filling level of the tubes 8, 9 is between 60 to 90%. However, granules can also be used as cementation agent 24 Made from a zinc-antimony alloy can be used as described above Introduce amount of antimony into the purified solution.

The purified solution 23 leaves together with the cementate and zinc particles the vibrating reactor 1 via the line 6, the cementation agent 24 through the Slotted disks 10, 11 is retained and enters the sedimentation tank 4, where the coarse solids content is sedimented as sedimentation residue 26, which then continuously or discontinuously mixed with the raw liquor 21 in line 5 or can be deducted from time to time for other use. The cleaned solution with the cementate 27 suspended in it reaches the feed pipe via line 7 14 of the quick disconnection device 2, for example a solid bowl screw centrifuge.

Before entering into the quick disconnect device 2, the cleaned Solution 27 flocculant 28 mixed in. The separation residue 29 passes through the Residue discharge 16 from the quick separation device 2 and has solid fractions in the grain size range up to 1> im. The separation residue 29 can be prepared according to known Process for the extraction of non-ferrous and precious metals are processed. The cleaned and solution 30 freed from the solids content has, for example, a content of Copper <0.2 mg / l, cadmium <0.4 mg / l, cobalt <0.1 mg / l and nickel < 0.05 mg / l of impurities at a pH value of 5.5 and is therefore suitable for numerous Plant suitable for zinc extraction using the electrolysis process.

For the production of cathodes zinc 40, for example, the cleaned Solution 30 is fed to a storage and test tank 32 by means of a feed pump 31, from which an electrolysis tank 33 is fed, in which cell acid 34 together with other additives 35 is added to the usable electrolyte 36, which then a cooling tower 37 is fed to which a fan 38 is connected.

The cooled electrolyte 36 continuously flows through the electrolytic cell 39, in which zinc is deposited cathodically as cathode zinc 40.

In the example described, the quick disconnect device 2 can also replaced by a rotary filter press or a pressure filter, the facilities have for the continuous removal of the separation residue 29, so that the-average Contact time between the cleaned solution and the cementate in the quick-release device 2 is as short as possible in order to dissolve the cementate once it has formed impede.

In FIG. 2, the system has in addition to that shown in FIG Main cleaning stage, a post-cleaning stage, which consists of a post-cementation facility, for example from an intermediate container 41 and a filtration device 42 exists, both of which are connected to one another via a line 43, in which a feed pump 44 and a pH value control 45 is located. The intermediate container 41 has an agitator 46 and is connected to the quick disconnect device 2 via the Line 47 connected.

When the system is in operation, purified solution 30 comes out of the quick disconnect device 2 via the line 47 into the intermediate container 41, into which at the same time for post-cleaning the Purified solution 30 a cementing agent, for example zinc dust 48 in only small amounts such as 500 milligrams per liter must be added. Cell acid is used to regulate the pH value between 4 and 4.7 by means of pH control 45 49 is also supplied to the intermediate container 41 in a suitable amount. The separation of the cement formed in the post-cleaning stage from that for the electrolysis certain post-purified solution 50 takes place in a suitable filtration device 42, for example, a filter press from which the filtrate 50 was purified Zinc extraction solution is supplied to the electrolysis treatment during the very zinc-containing filter residue 51 of the metal salt solution 21 is mixed. Appropriately is therefore the filtration device 42 by means of line 52 and pump 53 with the Line 5 connected to the introduction into the oscillating reactor 1.

In Figure 3 is used as a post-cementation device in an advantageous manner a second vibrating reactor 54 used, which the cementing agent 55 for the Post-cleaning of zinc lye in the form of zinc granules is abandoned. Regarding the regulation of the pH in pH control 45, cellic acid 56 can be introduced into line 57 by the solution 30 from the quick-disconnect device, which has been purified by a feed pump 31 2 enters the second oscillating reactor 54. The throughput in the vibrating reactor 54 is due to the high degree of pre-cleaning of the cleaned solution 30 four- up to five times as high like that of the swing reactor 1. The filtrate 50 or the subsequently purified solution that is fed to the electrolysis has contents of 0.05 mg / l Cu, 0.15 mg / l Cd, 0.08 mg / l Co and 0.05 mg / l Ni.

In addition to the examples described, the inventive Method and device also for removing other metals not mentioned here from metal salt solutions can be applied. In principle, this applies to all cementation processes, that of the purification, extraction or separation of metals from metal salt solutions to serve. An important prerequisite is the use of the appropriate active ingredients for the device, especially with regard to corrosion resistance.

It is pointed out by way of example that by using the method and the device a) from solutions containing cobalt-nickel containing sulfuric acid, nickel separated by means of cobalt or cobalt and sulfur, b) from chloride solutions, For example, Co, Ni, Cu, Ag and Au are precipitated with zinc or iron as a cementing agent, c) cemented out of cyanide solutions, gold and / or silver with zinc and d) copper can be cemented out of copper-containing mine waste water.

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Claims (10)

Patent claims 1. Process for removing metals from metal salt solutions, especially for cleaning zinc neutral eyes for electrolysis by cementation in the vibrating reactor and subsequent separation of cementate and purified solution, d a d u r c h g e k e n n n z e i c h n e t that the separation in a quick disconnection device he follows. 2. The method according to claim 1, characterized in that in the quick disconnect device an average contact time between the cleaned solution and cementate (27) of 5 minutes is not exceeded. 3. The method according to claim 1 or 2, characterized in that as Quick separation device uses a centrifuge (2) and a suitable flocculant (28) is used for coagulation. 4. The method according to claim 1 or 2, characterized in that the Quick separation in a rotary filter press or in a pressure filter, both is carried out with continuous discharge of solids. 5. Process according to claims 1 to 4, characterized in that that the purified solution is fed to a post-cementation device, the a filtration device (42) is connected downstream. 6. The method according to claim 5, characterized in that the filter residue (51) from the filtration device (42) before entering the vibrating reactor (1) the metal salt solution (21) is admixed. 7. The method according to claim 6, characterized in that the post-cementation is carried out in a vibrating reactor (54). 8. Device for removing metals from metal salt solutions, especially for cleaning zinc neutral eyes for electrolysis, by cementation in the oscillating reactor according to the method according to any one of claims 1 to 7, characterized marked. that an.den swing reactor (1) a quick disconnect device, preferably a full-shell screw centrifuge (2) is connected. 9. Apparatus according to claim 8, characterized in that the device additionally has a post-cementation device (41, 54), preferably one Vibrating reactor (54) connected on the discharge side to a filtration device (42) is. 10. Apparatus according to claim 8 or 9, characterized in that the quick disconnection device (2) below the vibrating reactor (1) that feeds it arranged and via lines (6, 7) to the feed pipe (14) of the quick-release device is connected directly or via a sedimentation tank (4).