DE3805906A1 - Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions - Google Patents

Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions

Info

Publication number
DE3805906A1
DE3805906A1 DE19883805906 DE3805906A DE3805906A1 DE 3805906 A1 DE3805906 A1 DE 3805906A1 DE 19883805906 DE19883805906 DE 19883805906 DE 3805906 A DE3805906 A DE 3805906A DE 3805906 A1 DE3805906 A1 DE 3805906A1
Authority
DE
Germany
Prior art keywords
solution
gas
ozone
reactor
tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
DE19883805906
Other languages
German (de)
Inventor
Konrad Dr Matt
Hans Georg Dr Guttenberger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde AG
Original Assignee
Linde AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Linde AG filed Critical Linde AG
Priority to DE19883805906 priority Critical patent/DE3805906A1/en
Priority claimed from EP19890102384 external-priority patent/EP0330028A1/en
Publication of DE3805906A1 publication Critical patent/DE3805906A1/en
Ceased legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/72Treatment of water, waste water, or sewage by oxidation
    • C02F1/78Treatment of water, waste water, or sewage by oxidation with ozone
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/10Inorganic compounds
    • C02F2101/16Nitrogen compounds, e.g. ammonia
    • C02F2101/18Cyanides

Abstract

The invention relates to a process and an apparatus for detoxifying cyanide- and heavy metal-containing solutions. To remove both free cyanide ions and heavy metal ions and also cyanide-heavy metal complexes, according to the invention it is proposed to dissolve an ozone-containing gas in the solution, then to feed CO2 into the solution and to take off the resulting precipitation products. <IMAGE>

Description

The invention relates to a method for detoxifying solutions containing cyanide and heavy metals as well as a Device for performing the method.

Solutions containing cyanide and heavy metals such as Electroplating waste can be due to its considerable toxicity not easily to natural waters or biological Sewage treatment plants are handed over.

Cyanide ions are usually contained in the solutions and cyano complexes removed by adding chlorine bleach. Cyanocomplexes are destroyed and the cyanide initially closes Chlorine cyanide oxidizes, which then converts to cyanate. While the end product cyanate is significantly lower than cyanide Shows toxicity, it is the intermediate Chlorine cyanide is a highly volatile and very toxic substance. The chlorine cyanide also reacts with organic ingredients also among the most undesirable in wastewater Chlorinated hydrocarbons. These are extremely difficult biologically  degradable and even hinder bacterial degradation processes from otherwise easily degradable water constituents.

On the other hand, heavy metals in solutions, too natural waters or biological sewage treatment plants should be a significant problem. Heavy metals accumulate in the sewage sludge and prevent or complicate it economical sludge disposal, such as wet application, Digestion etc. Usually the heavy metals are removed Add suitable precipitants, e.g. Caustic soda or Lime, precipitated as hydroxides.

Especially with waste water from the electroplating and Metal processing industry, however, are the heavy metals Cyanide complexes. In this case it is a direct precipitation heavy metals not possible.

The object of the present invention is therefore a method of the type mentioned in such a way that both Cyanidinones and heavy metals as well Cyan heavy metal complexes on simple and economical Way to be largely removed and toxic or Environmentally hazardous reaction products in the lowest possible Amount arise.

According to the invention, this object is achieved in that an ozone-containing gas is dissolved in the solution, then CO 2 is fed into the solution and any precipitated products formed are taken off.

Due to the ozone-containing gas, the cyanide ions are already at Oxidized to cyanate ions at room temperature. Cyanates only show about 1/1000 of the toxicity of cyanides biodegradable without great difficulty.  

In contrast to oxidation with chlorine bleach, the Use of an ozone-containing gas no salting and also no formation of disruptive or toxic secondary products.

The decomplexed heavy metal ions are then precipitated by feeding CO 2 into the solution. The resulting carbonate sludge is drawn off.

The combination of the two process features ozonization and CO 2 precipitation according to the invention enables simple and economical detoxification of solutions containing cyanide and heavy metals. In particular, heavy metal-cyano complexes are also effectively removed by the process according to the invention.

A pH of about 9 to about 11 is expediently set in the solution before and / or when CO 2 is fed in. This facilitates the precipitation of the heavy metal ions.

In a preferred embodiment of the invention dissolving the ozone-containing gas a pH of approx. 11 in Solution set. This measure has a high effect Oxidation potential for the oxidation of the cyanide ions by the gas containing ozone. It also becomes the following Precipitation eased.

Preference is given to dissolving the ozone-containing gas Heavy metals uncomplexed in the solution precipitated. The uncomplexed heavy metals don't have to go through Ozonization of the cyan complexes can be decomplexed.  

They can therefore precipitate before ozonization , causing the precipitation following the ozonization is relieved.

It has proven to be particularly expedient to also precipitate the non-complexed heavy metals by feeding in CO 2 , since the CO 2 is already available for the subsequent precipitation of the decomplexed heavy metals. A pH of approximately 9 to approximately 11 is advantageously set in the solution. As an alternative or in addition, the pH can also be adjusted accordingly, for example by adding NaOH, before the actual CO 2 feed.

If the ozone is made from technically pure oxygen e.g. by silent electrical discharge or UV radiation produced, so you get a gas mixture of about 5 to 10% ozone and 90 to 95% oxygen. This has the advantage that no annoying Nitrogen oxides are created and the inert gas is eliminated Nitrogen more oxygen can be dissolved in the solution.

A device for carrying out the method is characterized by at least one reactor for dissolving the ozone-containing gas in the solution, which is connected via at least one line to at least one reactor for feeding the CO 2 into the solution.

In a preferred embodiment, the reactor is for dissolution of the ozone-containing gas in the solution as a tube, in the concentric a cylinder made of gas-permeable material is used. Between the cylinder outer wall and the Inner tube wall is a space  intended. The interior of the cylinder is also with a Gas supply line for the ozone-containing gas in connection, while the space with a supply line for the Solution is connected. The supply line for the one to be treated Solution flows tangentially into the pipe. So the solution occurs tangentially into the pipe and thus gets a twist around the Reactor axis. Sedimentable particles are thus caused by the Centrifugal force kept away from the cylinder so that Clogging of the gas-permeable cylinder material avoided will. At the same time, this results in an increased Turbulence in the solution affecting the gas-liquid mass transfer promotes.

The cylinder is preferably made of sintered ceramic. The pipe is expedient because of the high corrosiveness of in Water-dissolved ozone is made from stainless steel, PTFE or PVC.

In a particularly expedient embodiment, the gas supply line and the supply line for the solution are attached to one end of the tube, while the discharge of the solution to the CO 2 reactor is arranged at the other end of the tube. This ensures the longest possible reaction path and an intensive mass transfer between gas and solution.

In a further development of the inventive concept are in Clearance between the cylinder and the pipe inclined guide vanes provided. Wear this on the one hand the cylinder and on the other hand ensure one Maintaining the twist of the solution that is going through Mitigates friction.  

The invention is suitable for detoxification of all conceivable Solutions containing cyanide and heavy metals. In particular is for pretreatment of wastewater from electroplating, Metal processing and coking industry interesting. The so pretreated wastewater can be harmless to biological Wastewater treatment plants are handed over. The one with the Invention associated oxygen loading of the pretreated Wastewater even has a positive effect on the subsequent one biological cleaning.

In the following the invention is based on a figure schematically illustrated embodiment explained in more detail.

Fig. 1 shows a flow diagram of the method according to the invention,

Fig. 2 shows the reactor according to the invention to dissolve the ozone-containing gas in the solution,

Fig. 3 shows a section through the reactor shown in FIG. 2 in the region of the feed solution,

FIG. 4 shows a section through the reactor according to FIG. 2 in the region of the guide vanes.

In Fig. 1 the individual process steps of the invention are shown schematically. The solution containing cyanide and heavy metals is first adjusted to a pH of about 11 by adding NaOH via line 9 . The non-complexed heavy metals are then precipitated in the reactor 6 by feeding in CO 2 via line 10 .

In principle, a conventional reactor for gas-liquid reactions can be used as the reactor 6 . The carbonate sludge is then separated off after the CO 2 precipitation. In the exemplary embodiment shown here, however, the reactor described in the patent application "Reactor for gas-liquid reactions" filed simultaneously with the present application (internal file number G 88/09) is used. This is particularly suitable for the method according to the invention, since it does not cause any problems with silting and clogging. Precipitation and separation of the precipitated products take place in one device.

The solution freed from the non-complexed heavy metals is then led via line 11 to the reactors 2 for dissolving the ozone-containing gas. The ozone-containing gas is generated in an ozone generator 1 from technically pure oxygen by silent electrical discharge. This gives a gas mixture of approximately 8% ozone and approximately 92% oxygen. This gas mixture is fed to the reactors 2 via line 12 , where it is introduced into the solution via ceramic sinter candles. The cyan heavy metal complexes contained in the solution are broken down and the cyanide ions are oxidized to the non-toxic cyanate ions.

The solution treated in this way is then fed to an expansion tank 3 , where excess ozone can escape to the atmosphere via line 13 and an ozone destroyer 4 . The solution is fed to a second CO 2 reactor 6 via pump 5 and line 14 . CO 2 is introduced via a measuring and control section 7 and line 15 into the reactor 6 and fed into the solution. The heavy metal ions decomplexed in the ozone reactors 2 are precipitated and withdrawn from the reactor 6 via line 16 . In the outlet of reactor 6 , the pH is regulated via the amount of CO 2 fed into the reactor 6 to facilitate the precipitation reaction so that a pH of approx. 9-10 is established in the solution. The detoxified liquid finally leaves the reactor 6 via line 17 and can be fed to a biological treatment stage.

In Fig. 2 is a cross section through the ozone reactor 2. The cylinder 21 is inserted concentrically in the stainless steel tube 20 , which has a diameter of 100 mm. A commercially available ceramic aerator candle with a diameter of 70 mm and a length of 500 mm is used as cylinder 21 . The solution enters tangentially into the intermediate space 23 between the stainless steel tube 20 and the ceramic aerator plug 21 via the supply line 24 . The solution thus has a swirl around the reactor axis, so that sedimentable particles are kept away from the ceramic aerator candle. The ozone / oxygen mixture coming from the ozone generator is introduced via the gas supply line 22 into the interior of the ceramic aerator candle 21 and passes through it into the intermediate space 23 . In space 23 , the oxidation of the cyanide ions contained in the solution and the splitting of the cyan heavy metal complexes takes place.

A vortex chamber 26 with inclined guide vanes 25 is arranged in a lower part of the reactor 2 . This maintains the spin of the solution.

Following the swirl chamber 26 , further pipe sections with inserted ceramic aerator candles can follow. The tube 20 finally merges at its lower end into the line 8 for discharging the treated solution.

Fig. 3 shows a section through the reactor 2 in the solution supply line 24. The feed line 24 , which has a diameter of 50 mm, is flanged tangentially to the stainless steel tube 20 .

In FIG. 4 is a section finally represented by the reactor 2 in the area of the vortex chamber 26. The inclined guide vanes 25 on the one hand carry the ceramic aerator candle 21 and on the other hand ensure that the swirl of the solution is maintained around the reactor axis.

Claims (16)

1. Process for the detoxification of solutions containing cyanide and heavy metals, characterized in that an ozone-containing gas is dissolved in the solution, then CO 2 is fed into the solution and resulting precipitates are removed.
2. The method according to claim 1, characterized in that a pH of about 9 to about 11 is set in the solution before and / or when feeding in CO 2 .
3. The method according to claim 1 or 2, characterized in that before dissolving the ozone-containing gas, a pH of about 11 is set in the solution.
4. The method according to one of claims 1 to 3, thereby characterized in that before dissolving the ozone-containing gas non-complexed heavy metals are precipitated.  
5. The method according to claim 4, characterized in that the non-complexed heavy metals are precipitated by feeding in CO 2 .
6. The method according to claim 4 or 5, characterized in that before and / or during the precipitation of the uncomplexed Heavy metals have a pH of approx. 9 to approx. 11 in the Solution is set.
7. The method according to any one of claims 1 to 6, characterized characterized in that the ozone-containing gas from technical pure oxygen is obtained.
8. The method according to any one of claims 1 to 7, characterized characterized in that the ozone-containing gas consists of approx. 5 to 10% There is ozone and about 90 to 95% oxygen.
9. Device for performing the method according to claim 1, characterized in that at least one reactor ( 2 ) for dissolving the ozone-containing gas in the solution via at least one line ( 8 ) with at least one reactor ( 6 ) for feeding the CO 2 into the Solution is connected.
10. The device according to claim 9, characterized in that
  • a) the reactor ( 2 ) for dissolving the ozone-containing gas in the solution is designed as a tube ( 20 ) into which a cylinder ( 21 ) made of gas-permeable material is concentrically inserted,
  • b) a space ( 23 ) is provided between the cylinder ( 21 ) and the tube ( 20 ),
  • c) the interior of the cylinder ( 21 ) is connected to a gas supply line ( 22 ) for the ozone-containing gas,
  • d) the intermediate space ( 23 ) is connected to a supply line ( 24 ) for the solution and
  • e) the supply line ( 24 ) opens tangentially into the tube ( 20 ).
11. The device according to claim 10, characterized in that the tube ( 20 ) consists of stainless steel.
12. The apparatus according to claim 10, characterized in that the tube ( 20 ) consists of PVC.
13. The apparatus according to claim 10, characterized in that the tube ( 20 ) consists of PTFE or PTFE composite materials.
14. Device according to one of claims 10 to 13, characterized in that the cylinder ( 21 ) consists of sintered ceramic.
15. The device according to one of claims 10 to 14, characterized in that the gas supply line ( 22 ) and the supply line ( 24 ) for the solution is attached to one end of the tube ( 20 ) and the line ( 8 ) for discharging the solution to Reactor ( 6 ) is arranged at the other end of the tube ( 20 ).
16. The device according to one of claims 10 to 15, characterized in that in the intermediate space ( 23 ) inclined guide vanes ( 25 ) are arranged.
DE19883805906 1988-02-25 1988-02-25 Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions Ceased DE3805906A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19883805906 DE3805906A1 (en) 1988-02-25 1988-02-25 Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19883805906 DE3805906A1 (en) 1988-02-25 1988-02-25 Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions
EP19890102384 EP0330028A1 (en) 1988-02-25 1989-02-11 Process and apparatus for the detoxification of solutions containing cyanides and heavy metals

Publications (1)

Publication Number Publication Date
DE3805906A1 true DE3805906A1 (en) 1989-09-07

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Application Number Title Priority Date Filing Date
DE19883805906 Ceased DE3805906A1 (en) 1988-02-25 1988-02-25 Process and apparatus for detoxifying cyanide- and heavy metal-containing solutions

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DE (1) DE3805906A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4428147A1 (en) * 1994-08-09 1996-02-15 Bwt Wassertechnik Gmbh Treating water contg. ozone-consuming components

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2984463A (en) * 1951-08-31 1961-05-16 Torricelli Alfred System for disinfecting water
US3736254A (en) * 1971-06-03 1973-05-29 Owens Illinois Inc System for removing color from paper mill liquid waste
US3775314A (en) * 1971-06-07 1973-11-27 Water Treatment Corp Method and apparatus for mixing gases with water
DE2637418A1 (en) * 1975-08-18 1977-03-03 Emery Industries Inc Method and apparatus for ozone treatment liquids aqueous
EP0125162A1 (en) * 1983-05-10 1984-11-14 SOCIETE LYONNAISE DES EAUX ET DE L'ECLAIRAGE Société dite: Apparatus for dissolving ozone in a fluid

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2984463A (en) * 1951-08-31 1961-05-16 Torricelli Alfred System for disinfecting water
US3736254A (en) * 1971-06-03 1973-05-29 Owens Illinois Inc System for removing color from paper mill liquid waste
US3775314A (en) * 1971-06-07 1973-11-27 Water Treatment Corp Method and apparatus for mixing gases with water
DE2637418A1 (en) * 1975-08-18 1977-03-03 Emery Industries Inc Method and apparatus for ozone treatment liquids aqueous
EP0125162A1 (en) * 1983-05-10 1984-11-14 SOCIETE LYONNAISE DES EAUX ET DE L'ECLAIRAGE Société dite: Apparatus for dissolving ozone in a fluid

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
JP 59-83000-A, Referat aus Chemical Patents Index, Derwent Publications LTD, London, Ref.Nr. 84-155771/25 *
Referat aus Chemical Abstracts, Vol 86., 1977, p. 381, Ref. Nr. 86: 95450j *
Referat aus Chemical Abstracts, Vol. 81, 1974, p. 416, Ref.Nr. 175905y *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4428147A1 (en) * 1994-08-09 1996-02-15 Bwt Wassertechnik Gmbh Treating water contg. ozone-consuming components

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