FR2608628A1 - PROCESS FOR EXTRACTING METALS FROM METAL COMPOUNDS IN STONE MATERIALS - Google Patents

Abstract

EARTH TREATMENT PROCESS. ONE OR MORE TANKS 1 ARE FILLED WITH POLLUTED EARTH, EACH ON A PERMEABLE SOIL SURFACE 2 OF AT LEAST 10 M AND A HEIGHT OF 0.5 TO 5 M AND THESE MASSES ARE TREATED BEFORE OR THEN FILLING THE CONTAINER (S) IN SUCH A WAY THAT A PERMEABLE HOMOGENEOUS MASS IS CREATED. APPLICATION TO AGRICULTURE.

Description

The invention relates to a method for extracting

  contained in one or more metal compounds in any form in loose stony materials, by spraying these materials in an open reservoir, with one or more reagents reacting with the metal compound (s), remove the new metal compound (s) formed from the stony material and evacuate the

metal of the eliminated solution.

  Here, the term "stony materials" refers to the surface soil containing undesirable metal compounds, such as compounds of Cd, Cu, Hg, Pb and Zn and others

harmful substances.

  The process described above has already been mentioned in US Pat. No. 4,473,532, but it relates to the treatment of ores,

  a material almost always easily permeable. The

  in situ leaching methods except for, for example,

  EP-0 059 020, there are other known methods

  both the treatment of polluted soil such as paste, with an aqueous reagent, for example from JP-52 072 368 and JP-52 107 964. In the manual "Handboek Bodemsaneringstechnieken" ("Manual of soil remediation techniques" ), fasc.1,

  July 1983, extracting the polluted surface from the soil is also

  indicated, but without any further essential details

have been provided.

  It is also known that reactive

  appropriate for this purpose; US Pat. No. 3,634,070 mentions EDTA in this connection, but in the examples given, for

  extremely small amounts of land.

  It is generally agreed that further development of soil remediation techniques is needed, including the Dutch daily "NRC Handelsblad" of the

  12 September 1987, p.7, or "Energy in Afbalbeheer" ("Ener-

  and Waste Management "), No. 4, April 1987.

  If, according to US Pat. No. 3,634,070, the use of EDTA on a laboratory scale was obvious, for the application of EDTA on a larger scale and under well-defined conditions, also relating to treatment of the earth with an aqueous EDTA solution by recovering the EDTA, quite expensive, used, it is required a process which is the object

of the present invention.

  EDTA forms complexes with metal compounds

  present. The full denomination is: sodium salt of Ethy-

  lene-Diamine-Tetra-acetic acid and has, among others, been described in great detail as "dissolvine E 39" of the "sequestering agents" of AKZOChemie. Normally 1 mole of

  this complex trainer binds 1 metal mole.

  Moreover, the invention is not limited to the use

  EDTA, but depending on the pollution, it is also possible to use an aqueous solution of an acid, a detergent,

  another complex trainer or even water.

  The application of an installation as described in

  US-4,473,532 is for this purpose the central element, as men-

  initially, but for the treatment of the land, the

  specifications indicated as being general are

  ficient. The process is continuously applied by: a) filling one or more tanks with polluted soil, each on a permeable soil surface with an area of at least 10 m2 and a height of 0.5 to 5 m and treating these masses before or during the filling of (the) container (s) such that a homogeneous permeable mass is created; b) then spraying each quarter of m2 of the surface of this (these mass (s) with an aqueous solution of a reagent previously prepared so that at least 1 solution per hour lixivie the (the) mass (s);

  (c) recycling the leachate by means of a reservoir of

  turn away by undesirable elements while adding as many reagents to the solution to be sprayed so that the losses caused by the regeneration are compensated; and

  (d) continuing recycling until the evacuation

  tion of the metal ions achieves an admitted value in the soil in question, after which reagent still present will be removed with water having a pH value

may vary from 3 to 11.

  It is essential that the soil is impregnated with

  in order to avoid channel formation. This can be achieved by compressing the soil slightly with a mechanical vibrator, but it may be necessary

  add sand or other additive to increase the

  Maintain the permeability, possibly adding followed by

  slight compression to prevent the formation of

  tioned. The recycled liquid is partially regenerated by adding the chemicals and water needed for this purpose. As reagent is preferably used an EDTA solution having a pH value of about 6, and a content

between 2 and 40 m%.

  It is best to add the liquid using

  drip, for the reason already mentioned and for use

  a number of pressure compensating drips, already listed per se and known among others

  under the trade name Revaho. With these drop

  which are also used for watering plants.

  it is quite possible to deposit on or inject

  ter in the mass of earth a known quantity determined by surface. The use of drip allows a simple treatment process and makes it a natural process

  accelerated leaching. It is thus possible after the treatment

  to deliver the materials with guarantees of

  vency. According to the process of the invention, only part of the leachate is preferably continuously regenerated. This is so since: a) the lixivia is neutralized with Ca (OH) 2 and / or NaOH until a pH value of about 12 is reached;

  (b) the neutralized solution is directed to a first

  first settling tank and the mud that has settled

  is separated, washed, dehydrated and disposed of as waste;

  (c) almost all the remaining liquid is acid

  until a pH value of about 6 and

  rowed to a return tank for reuse.

  Another step limiting the use of EDTA to its minimum is as follows: a) a part of the filtrate and washing liquid of

  the dehydrated sludge is acidulated until it reaches a

  their pH of about 2, case of precipitation of EDTA; b) the formed precipitate is deposited in its liquid in a second settling tank and is then directed to the last phase of acidulation where this EDTA deposit with a pH value of about 6 resolves and is directed again to the return tank, still for reuse,

  with the filtrate, the filter wash liquid and the

  clear quid of the first settling tank.

  The quantity of leachate recycling directly, is

  ie without regeneration, is equal to the amount to be regenerated, in practice between the limits of 1: 5 and: 1. Some elements depend on the concentration or the remaining concentration, metal ions of the land undergoing treatment and residence time of the lixivant in the land mass.

  When pH values are mentioned, it is

  are the most recommended values; differences are tolerated, provided that the different values have not been

  no adverse influences on the principle and effectiveness

efficiency of the process.

  It is obvious that a deposit must be found

  suitable for the extracted solid product. Reprocessing

  metallurgical will be largely taken into consideration.

  Another method to regenerate the separate part

  lixivia consists in subjecting it to a process of elec-

  trolysis, o, in this case, there is firstly a continuous separation of metals and secondly an EDTA solution which is returned to the solution to be prepared. For these purposes electrolytic cells are applicable

  commonly found in commerce.

  The application of this process also makes it possible to

  Use EDTA by acidulating part of the solution, separating the solid EDTA formed and returning it to the mixing tank. In principle this

  technique does not deviate from the method already described above.

  The concentration of the aqueous EDTA solution is not critical; the use of a solution for sprinkling of the earth pile can be applied with a concentration of between 1 and 40 m%, preferably between

  2 and 20 m%; a concentration of 5 m%

  came. The invention has the following advantages: a) possibility of delivering the earth, if necessary

  industrial waste, with guarantees of washing-up

ity;

  b) simple and easily controllable process.

  The invention is explained by means of a global plan.

  trant: Figure 1: a flowchart with chemical regeneration of the solution used;

  Figure 2: a flowchart with electrolytic regeneration

than the solution used.

  Figure 1 shows a mass of earth 1 with dimensions

  and density as described above. The mass 1 is formed by spreading layer by layer in flat surfaces, of the soil previously sorted in advance following

its degree of pollution.

  When a "mass of land" is mentioned, it can also mean several masses that are processed at the same time. This may be the case, for example, when land with several types of pollution, such as a mass of soil polluted by various heavy metals, is treated.

  and a mass containing for example slag (zinc).

  It is also possible that a highly polluted mass is

  treated at the same time as a mass of a low degree of pol-

  lution. Indeed, the treatment of this last mass could be of shorter duration. The same mass of

  earth can be treated successively with several

  extraction reagents if two or more types

pollution are present.

  In addition, it is possible that it is necessary to increase the permeability of the earth. In this case

  soil is pre-mixed with sand, in proportion

  up to 50 m%. What is also important in this situation is particle size. This may lead to separating the material (sieving) into fractions and / or to reducing the material in whole or in part

  to make the substances to be removed more accessible.

  The mass (possibly the masses) rests on a

  permeable soil 2 which can be composed of all the

  possible, provided that it is not attacked

  ble by the solution. The liquid passing through the soil 2 is collected at the level of the non-permeable soil 3 inclining towards a rallying point A. The liquid collected at A is pumped with a pump 4 into a return leach tank 5 and from this point, directed to a large number of sprinklers or drip 6 above or in the mass 1; a drip 6 per area of approximately

0.50 x 0.50 m.

  The permeable soil 2 preferably comprises gravel

  sand, and possibly drifting pipes.

  swimming which can, among other things, convey the leachate to a rallying point A. For the extraction of metals, it is taken as

  starting point in this case a pre-prepared EDTA solution.

  SOE. It is in a tank 7 and can feed

  wholly or to the extent necessary, the drop-in

  drop. The solution of this reservoir is partially

  decked in a mixing tank 8 with a concentration

  approximately 5 m% of EDTA, at a pH value of 6, but

  will also partially come from the Regeneration

  ration. This operation may be described as follows: part of the leachate is taken from point B and conveyed to a neutralization tank 9, where a solution of Ca (OH) 2 and / or of NaOH is added until a solution is obtained.

pH value of about 12.

  The suspension formed is directed from the neutralization tank to a settling device 10, where the precipitate formed of metal hydroxide can be deposited. The precipitate of deposited metal hydroxide is pumped to a filter press plant. In the filter press, the precipitate, containing 2 - 10% of dry substance, is dehydrated discontinuously or not, until a filter cake with a dry substance content is obtained.

A4 2608628

from 40 to 50%.

  The remaining percentage of the filter cake is

  holds the EDTA solution. This EDTA solution is

  most of the time by washing the filter cake during a filter cycle using wash water having a pH value of about 12. The washed filter cake is collected by filter cycle in

  containers and represents the waste of the process

  holding the heavy metals having been evacuated from the earth bed.

  The clear liquid supernatant in the decantation bottom

  the filtrate and the wash water from the filter press are discharged to a joining point C. The liquid is pumped from the joining point C to a dividing point D, where the total flow is divided into two flow, each undergoing separate treatment. Most of the total flow is added from the

  point D to a mixing tank 12. The other part,

  more EDTA solution, is added to a reservoir of

  13. The excess EDTA solution consisted of the dilution of the lixivia by adding lime milk,

  NaOH solution and wash water.

  In the acidizing tank, the pH value is

  approximately 2, in groups of approximately

  1-4 m3 by adding 30 m% HCl solution. At this pH value, EDTA rushes the solution in quality

  of organic acid in the form of crystals.

  From the acidizing tank, the suspension obtains

  is transported to a decanting device 14.

  In the decanting device 14, the EDTA crystals are separated as EDTA sludge. EDTA sludge is added

  mixing tank 12 so that the EDTA is reused

read at maximum.

  In the mixing tank 12, the EDTA solution

  is again prepared for reuse. This preparation

  It can be described as follows: a) most of the total flow from point D is mixed with the EDTA sludge from decantation device 14;

  (b) loss of EDTA during the regeneration process

  ration is here, if necessary, compensated by adding 40 m% of EDTA solution; c) after correction of the pH value by adding

  of the HCl solution or a solution of NaOH, the solution

  lution is ready for reuse; d) this solution is pumped from the mixing tank

  12 to the tank 7 and can be used as lixi-

  viant. The clear supernatant liquid from the decantation device 14 is partially reused as dilution water in the mixing tank 8 and partially

  as rinsing water to a rinsing water tank 15.

  During the final phase (rinsing phase) a part

  this liquid is discharged to a sewer system.

  At the end of the purification operation, which lasts

  1 to 4 months after the start of the leaching process, the EDTA remains rinsed from the soil mass 1

  lixiviant with rinsing water. The rinse water exits

  can undergo the whole regeneration process as

  written for the regeneration of leachate. On the other hand, the outgoing rinse water can also be added directly to the acidizing tank 13 in order to recover the EDTA as

solid substance.

  Figure 2 depicts up to the regeneration part

  starting at B, the same process as described in

figure 1.

  The regeneration part of Figure 2 can be described as follows: part of the leachate is taken from point B and conveyed to the electrolytic unit 8. In the electrolytic unit 8, passing an electric current in one or more electrolytic cells, heavy metals are separated from the leachate as metal or metal oxide. These metals are separated into groups by purification of the electrode material of the electrolytic unit and are discharged as residues. The purified EDTA solution is introduced from

  from the electrolytic unit 8 to a mixing tank 9.

  In the mixing tank 9, this EDTA solution is ready for reuse by adding 40 m%, if necessary, of EDTA solution and correcting the pH value by

  addition of solution of HCl or NaOH solution.

  After adaptation for reuse, the EDTA solution is pumped from the mixing tank to the

  tank 7 and can again be used as lixi-

viant.

  The mixing tank 9 is also used for preparing

  of the EDTA solution at the beginning of the

  ration. At the end of the purification operation, approximately 1 to 4 months after the beginning of the leaching process, the

  remnants of EDTA are rinsed from the earth mass 1 in lixi-

  with rinsing water from the rinsing water tank

13, as described above.

  The outgoing rinse water is discharged from point B and undergoes the same treatment as the leachate in

  the electrolytic unit 8. The purified rinsing water is di-

  removed from the electrolytic unit 8 to a

  In the acidizing tank 10 is added HCl solution to this rinse water containing EDTA, until a pH value of about 2 is obtained. EDTA rushes to this pH value in

  organic acid in the form of crystals.

  The suspension formed is conveyed from the reservoir

  see acidification 10 to a decanting device 11.

  EDTA crystals are discharged as EDTA sludge

  the settling device to a storage tank

age 12.

  The stored EDTA sludge can then be used as a raw material for the preparation of EDTA solutions. The invention is not limited to EDTA; it is also possible to apply, depending on the pollution,

  acidic solutions and alkaline solutions.

  The sprinkler principle of a soil bed can also be applied to:

  (a) the biochemical or bacteriological treatment

  monitored followed by extraction or rinsing with

very solutions;

  (b) the leaching of industrial residues under

  granular, causing the evacuation of leachable unwanted constituents or the extraction of usable constituents.

For example:

  An amount of soil containing loess having the following pollutions: Cd, Pb and Zn, was treated according to the method of the invention. 10 m3 of soil have been crammed to a height of 1 m

  on a layer of gravel 10 cm and vibrated.

  Above the bed were installed 40 drip-type of those described above. The quantity of liquid supplied, in this case an aqueous 5 m% EDTA solution with a pH value of 6, was determined in such a way that all the added liquid leached the layer of soil;

  the quantity of leachate then rose to 40 l / h.

  After continuous treatment for a period of 3 months,

  it turned out that the contents of the metals mentioned

  above it dropped 92% from the original value,

  measurement established by taking samples from the soil.

  Then rinsing was again carried out with acidulated water for 15 days while recovering the EDTA always present. Then, after drainage for 5 days, the relatively dry soil could be returned in quality

of "clean earth".

  The use of EDTA exceeded the calculated amount

only 4.6%.

  Finally, variants of the described method are possible. The leachate can thus, immediately after it has been collected or at another time, be purified

  or again purified by means of electrolysis.

  If, in the soil to be purified, there are components each requiring a specific extraction agent, these can be introduced at the same time (such as DTPA, HEDTA, gluconates, sulfite, pyrosulfite, and / or oxalate / oxalic acid). Similarly, in the earth bed, certain conditions can be created, such as a reducing medium,

  oxidizing, acidic or basic. If necessary, in order to improve

  contact the extractant with the pollutants

  it is possible to add humectants

to the extraction agent.

  Although it is better to water according to the given guidelines, the invention is not for

  strictly limited and the introduction of liquid

  extraction by the base is not excluded in advance;

  it is also possible to introduce the extractive liquid

  during the purification of the earth bed, alternatively

  from above or from the base and to evacuate the leachate

  by the base or the top of the bed for

neration or recycling.

Claims (19)

  1. Process for the extraction of metals containing   in one or more metal compounds, in any form in loose stone materials, by spraying these materials in an open container,   several reactants reacting with this compound (s)   by removing the new compound (s) from the   formed from stony materials and by evacuating the   of the removed solution, characterized by the following operations: a) filling one or more reservoirs (1) with the polluted earth, each on a permeable soil surface (2) with an area of at least 10 m2 and a height of   0.5 to 5 m and these masses are treated before or when filling   container (s) in such a way that a homogeneous mass permeable gene is created;   (b) each quarter square meter of   area of this (these mass (s) with an aqueous solution   of a previously prepared reagent, so that at least   40 ml of solution per hour lixivie the mass (es); c) the lixivia is recycled through a return tank by removing the undesirable elements while adding as many reagents to the solution to be sprayed so that the losses caused by the regeneration are compensated;   (d) continue recycling until the   cuation of the metal ions makes it possible to reach a permissible value in the soil in question, after which the reagent   still present will be removed with the help of water having a   their pH can vary from 3 to 11.   2. Process according to Claim 1, characterized in that the mass of soil is slightly compressed.   using, for example, a mechanical vibrator.   3. Method according to claim 1, characterized in that sand is added to the earth or another adduct.   4. Process according to claims 1 to 3, characterized   rised by the fact that the land to which was added   sand or other additive, will be slightly hurry.   5. Process according to claims 1 to 4, characterized   in that the aqueous solution of the reagent is an EDTA solution having a pH value of about 6 and   a content between 2 and 40 m%.   6. A process according to claims 1 to 5, characterized   rised by the fact that the recycled liquid is partially   regenerated by adding chemicals and water necessary for this purpose.   7. A process according to claims 1-4, characterized   rised by the fact that watering is done by means of drop-   droplet (6), preferably compensating drip pressure testers.   8. Process according to claims 1-7, characterized   in that: a) the leachate is neutralized with Ca (OH) 2 and / or NaOH until a pH value of about 12 is reached;   (b) the neutralized solution is directed to a first   first settling tank (13) and the mud that was there   deposited is separated, washed, dehydrated and disposed of in four waste disposal;   (c) almost all of the remaining liquid is   until a pH value of about 6 is reached and   directed to a return tank (5) for reuse.   9. A process according to Claims 1 to 8, characterized   in that: a) a portion of the filtrate and washing liquid of the dewatered sludge is acidulated to a pH value of about 2, when precipitation of EDTA; b) the formed precipitate is deposited in its liquid   in a second settling tank (14) and is   continued to the last acidizing tank (12)   o This EDTA deposit with a pH value of approximately 6 is   back and is directed back to the tank back   (5), again for reuse, with the filtrate, the li-   filter wash and the clear liquid of the first settling tank (10).   10. Process according to claims 1 to 9,   by the fact that the quantity of liquid that recycles without being regenerated is equal to the quantity   regenerate between the limits of 1: 5 and 100: 1.   11. Process according to one of Claims 1 to 9,   characterized by the fact that more than one mass of soil of different composition and / or pollution is treated at the same time, each with its treatment duration and its   specific reagent, if desired.   12. Process according to one of Claims 1 to 11,   characterized by the fact that the earth is mixed by advancing   this with sand or other additive up to 50 m%.   13. Process according to one of Claims 1 to 12,   characterized by the fact that the soil to be treated, before the treatment, is separated according to the dimension   particles and / or is reduced in whole or in part LEMENT.   14. Process according to one of Claims 1 to 10,   characterized in that the permeable layer (2) is composed of sand or gravel and provided with a drainage system, if desired.   15. Process according to claims 1, 3, 4, 7,   8, 9, 10 and 11, characterized by the fact that the masses   if necessary pretreated, are sprayed with an acid,   lixiviant or liquid for bacteriological treatment   controlled logic or leaching of industrial residues in granular form.   16. Process according to one of Claims 1 to 12,   characterized by adding solutions with a   reagent by drip (6) can be done by   tallant drip (6J in the mass (es) of material.   17. Process according to one of Claims 1 to 9,   characterized by the fact that: a) the leachate after undergoing neutralization is purified by means of electrolysis;   (b) the leachate is cleaned by immediate electrolysis   diatement after collection of the earth bed.   18. Process according to one of Claims 1 to 12,   characterized by the fact that: a) for each polluted component in the earth, a combination of extraction agents can be used; b) according to the order of addition of the various extraction agents, it is possible to create certain conditions in the earth bed, such as a reducing, oxidizing medium, acidic or basic; -   c) for the creation of these conditions can be applied other chemicals, such as DTPA, HEDTA,   gluconates, sulfite, pyrosulfite, and / or oxalate / acid. oxalic;   (d) to improve contact between the agent of   traction and the pollution present, it is possible   adding humectants to the extractant.   19. Process according to one of Claims 1 to 6,   characterized by the fact that: a) the extraction liquid can also be introduced by means of a system through the base; b) the extraction liquid during the purification of the earth bed is introduced alternately from above or from the base and the leachate is discharged respectively by   the base or from the top of the earth bed for regeneration tion or recycling.