FR2626007A1 - AGENTS FOR THE ELUTION OF PRECIOUS ADSORBED THIOUREE-METAL COMPLEXES ON ACTIVE CHARCOAL AND METHODS FOR OBTAINING PRECIOUS METALS - Google Patents

Abstract

Agents for the elution of thiourea-precious metal complexes adsorbed on activated carbon based on an acidic aqueous solution containing thiourea and an organic solvent which has a thiourea content of 0.1 to 50 g / l and which contains at least least one organic solvent partially soluble in water, such as mono- or polyalcohols, optionally substituted, ethers, esters or ketones. Application to the production of precious metals such as silver or gold from complexes of these metals with thiourea, adsorbed on activated carbon.

Description

AGENTS FOR THE ELUTION OF THIOUREE-METAL COMPLEXES

  PRECIOUS ADSORBES ON ACTIVE CHARCOAL AND METHODS

  FOR OBTAINING PRECIOUS METALS

  The present invention relates to agents and processes for obtaining precious metals from

  their complexes with thiourea adsorbed on

good assets.

  A particular mode of use for obtaining

  precious metal complexes adsorbed on

  good asset is constituted by the so-called "Carbon-in-

  Pulp "which has become of great importance on the scale

  dustrial. In this process, granulated activated carbon with a grain diameter of about 0.5 mm or more is added directly to a finely ground suspension of

  ore or other raw materials containing a

  such as roasting residues and "laundry" when the dissolution of the precious metal is complete.Here, an expensive separation of the leached solid substance from the liquid containing the precious metal is not necessary, since the activated carbon containing the precious metal can be separated in a simple manner from the valueless leaching residues by a large sieve

sts.

  In the later stage of the process, the precious metals must be separated from the active carbon. In the

  the case of the use of cyanides as

  the precious metals are in the form of

  Cyanide plexes adsorbed on activated charcoal. For the desorption of the precious metal, the activated carbon must

  preferably be treated under pressure at temperatures below

  above 100C, by an alkaline solution of cyanide. This process is technically complicated. because he

  In particular, it requires that we work with cyanide

extremely toxic.

  The use of thiourea much less

  compared with cyanides, as a leaching reagent for precious metals, has also been known for a long time. Compared with cyanides, thiourea has a higher dissolution rate.

  for precious metals, and its complexes with the

  valuable rates are adsorbed more rapidly and to a greater extent by activated carbon,

  To elute again the thlourea complexes

  In the case of the active carbon, the expensive pressure technique known from cyanide leaching has been used. According to another suggestion, it is eluted with thiourea solutions of high concentration (100 g / l of thiourea), strongly acidic (50 g / l of sulfuric acid), which contain up to 30% by volume of acetone. How-

  such as precious metals can not be ob-

  taken directly from these strongly acidic solutions, a prior neutralization, with a considerable expense of neutralization chemicals and 2f additional filtration, is necessary in this case. The use of solutions containing alcohol

  glycol, as it has been recommended for the elucidation of

  heavy metals adsorbed as complex

  with cyanides, does not lead to

  the desired result in the case of thiourea-methyl complexes

  precious tal (see Engineering & Mining Journal, June

1987, p. 48,49).

  The invention therefore proposes to provide a procedure.

  technically simple and economical die for the elution of thiourea-precious metal adsorbed coal complexes

  active and to obtain from these metals the pre-

heavens in metallic form.

  This object is achieved according to the invention by an agent for the elution of thiourea-metal complexes.

  valuable adsorbed on activated carbon based on a solution

  acidic aqueous solution containing thlourea and a sol-

  organic material, which is characterized in that

  holds from 0.1 to 50 g / l of thiourea and at least one solvent

  organic partially soluble in water.

  Another object of the invention is a process for obtaining precious metals using the agent according to the invention, which is characterized by the following reaction steps:

  0 a) elution of the thiourea-precious metal complexes at

  heating activated carbon at room temperature or at room temperature with 1 to 100 ml of the agent according to the invention for 0.1 g of charged activated carbon,

  b) Precious metal precipitation from the phage

  - Aqueous / organic by addition of non-precious metals

  in the presence of a small quantity of sulphite and, where appropriate, reactivation of the active carbon

  with an aqueous solution of a sulfite.

  This agent and the process surprisingly make it possible to obtain silver and gold precious metals.

  under relatively mild conditions and with a

  high lectivity, from suspensions of finely ground ores. Compared with the more procedures

  old, we operate in addition with solutions of concentration

  relatively low levels, so that losses of chemicals and organic solvents remain low. As partially water-soluble organic solvents, polyalkyls, substituted alcohols, esters,

  ethers (and also cyclic ethers such as dioxane

  or tetrahydrofuran), ketones, nitriles, amides (see Table VI). A preferred agent is a

  aqueous solution adjusted to a pH of 1 to 3 with

  from 1 to 50 g / l of thiourea and from 0.1 to 20% by

  lume of at least one alcohol with 3 to 5 carbon atoms,

  a glycol or a glycolic ether. We particularly prefer

  In particular, an aqueous solution having an acid-adjusted pH of 1.5 to 2.5 and containing 1 to 1 g / 1 thlourea and 0.1 to 10% by volume n-butanol (see Table II). . The combination according to the invention of thiourea and an organic solvent partially soluble in water leads to a surprisingly synergistic effect when

  the elution of the precious metal from coal

  because, under the conditions chosen, neither a solution

  acidified with thlourea, or an acidified solution containing

  For example, butanol alone does not achieve a satisfactory elution of the precious metal. It's only

  the combination in the form of an acidic aqueous solution

  thiourea difiere containing an organic solvent which unexpectedly leads to a high elution of

precious metal (see Table I).

  The process according to the invention for elution

  thioure-precious metal complexes adsorbed on char-

  good asset is carried out with the agent according to the invention.

  preferably at room temperature or at an increased temperature up to 95 ° C, using 0.1 g of charged activated carbon 1 to 100 ml of an elution solution having a thiourea concentration of 0, 1 to

  50 g / l, the partial organic solvent content of which

  soluble in water is 0.1 to 20% by volume and whose pH has been adjusted to values between 1

  and with an acid. When the elution of the thio-complexes

  urea-precious metal is complete, the metals are precipitated

  valuable levels from the aqueous / organic phase after separation of the activated carbon, preferably by addition of non-precious metals. It is preferably carried out - here in the presence of a small amount of sulfite and

  regenerates, if necessary, activated carbon with a solution

aqueous sulphite.

  Preferred conditions of application of the procedure

  are: an elution at a temperature of 20 to 80C (see

  Table III): a concentration of 1 to 10 g / l of thio-

  urea in the elution solution; an organic solvent content of 1 to 20% by volume; a pH of the solution

  1.5 to 3 (preferably by addition of sulfuric acid

  than). Particularly preferably used as partially water-soluble organic solvents are propanols, butanols, amyl alcohols or glycol ethers. These solvents can be used alone or as a mixture. Table VI shows a

  number of partially solvable organic solvents

  lubles in the water that give in combination with a

  aqueous solution, thiourea acid (10 g / l of thio-

  urea; pH 2) a clear synergistic effect when separating

  complex silver or gold complex from

activated carbon.

  As activated carbons, it is possible to use

  trade products. These must simply be suf-

  strongly resistant in aqueous solutions for

  able to be separated by filtration in a practical manner

  completely complete of the finely dispersed disorder. Char-

  good and particularly suitable assets are provided

  others by Calgon Companies (eg Calgon GRC 22), Haycarb Carbon 6 - 16, Carbon (eg PICA G 210), Degussa (eg Degusorb C 25), Norite (eg R

2520), Kop Ank 11, 8 - 16.

  A particular advantage of the invention should be seen in the fact that the elution is very selective for the precious metals adsorbed on activated carbon. Other metals simultaneously adsorbed such as in particular copper, lead or other elements, such as for example sulfur, arsenic are not separated from the coal by the eluting agent or are only to a small extent. As a result, the precious metals can be obtained with high purity from the eluate, for example by carburizing with non-metals.

  Preciously finely pulverized such as iron, aluminum.

  magnesium, zinc. Iron which is cheap is preferably used. A small amount of sulfite, for example 0.05 to 5 g / l, is added to the precipitation solution.

  in the form of sulfur dioxide or sulphite

  dlum, sodium pyrosulfite is preferably used in an amount of about 0.1 to 1 g / l. The addition of

  sulphite on the one hand increases the extraction of the pre-

  heaven or lowers on the other hand the needs of non metal

  valuable for carburizing (see Table IV). The

  The addition is preferably carried out by adding 1 to mass units. of non-precious metal per unit mass of precious metal bonded under the complex form for a content of 0.1 to 1 g / l of sulfite in the reaction solution, at a temperature of 40 to 70 ° C, it is

  almost complete after 0.15 to 4 hours.

  As coal can become increasingly inactive during repeated charging and discharging processes, it is advisable to regenerate it continuously,

  that is to say, to rid it of impurities still ad-

  sorbed to maintain its initial carrying capacity

  the. A hot treatment with sulphites such as, for example, sodium sulphite, sodium pyrosulphite,

  sodium bisulphite has been found suitable for this purpose.

  fet. The contaminated activated carbon is preferably regenerated at a temperature of 50 to 95 ° C for 0.15 to 4 hours.

  with an aqueous solution containing 1 to 100 g / 1 of sulphate

  fite of sodium. After this treatment, the activated carbon again has its initial adsorption capacity for

  the precious metal-thiourea complexes (see Table V).

  The following examples are intended to explain

  the invention in more detail without limiting its scope.

E X E M P L E 1

  Elution of activated carbon silver with an acidified solution of thiourea, an acidified solution

  containing butanol and an acid solution of thio-

uree containing butanol.

  For the demonstration of the synergistic effect during the separation of silver from activated carbon, an active carbon of the Calgon GRC 22 type was used.

  contained, after a leaching process by thio-

  urea, 40% water and 3% silver in the

  che. 50 ml each time solutions 1 to 3 (see Table I) were stirred in a water bath at 70 ° C. for 3 hours with 0.1 g of activated carbon Calgon GRC 22, then

  analyzed to determine the money eluted.

  As can be seen from Table I, we separate

  coal, with an acidified thiourea solution,

  holding butanol, practically all the silver, while with a solution containing only butanol

  or that thiourea can only be

  unsatisfactory portions of money.

TABLE I

  Solution 1 Solution 2 Solution 3 thiourea g / 1 10 - 10 n-butanol ml / l -50 50 sulfuric acid g / 1 0.66 0.66 0.66 (= pH 2) silver eluted mg / l 4.3 1, 6 35.2 silver eluted% 11.9 4.5 92.8

E X E M P L E 2

  Influence of thiourea concentration and butanol content in the elution solution on

the elution of money.

  The conditions of the experiment were similar to that

  described in Example 1. Calgon GRC 22 activated carbon was used which was charged with 0.52% by weight of silver. The mixture was shaken off for 3 hours in a 70C waterbath with increasing amounts of butanol and increasing amounts of thiourea in

the eluting agent.

  Table II gives the result obtained.

TABLE II

  1-butanol thlourea eluted silver ml / l g / l (X)

- 2.6

2 32.9

5 37.0

10 39.0

- 3.8

2 58.6

5 58.9

10 62.7

- 5.1

69.9

5 68.0

10 79.1

3O

- 4.5

2 95.0

5 96.0

10 97.8

EXAMPLE 3

  Influence of temperature on the elution of money. The test conditions corresponded to those of Example 1. An activated charcoal loaded with 2.8% silver, Degusorb C 25 from the Degussa Company (as a dry substance) was eluted by shaking for 3 hours at various temperatures with a solution which contained 50 ml / l of butanol, 10 g / l of thiourea and which was acidified to pH 2 with sulfuric acid. The

  Table III gives the results obtained.

TABLE III

eluted silver temperature

(C) (%)

59.6

72.0

2Of, 60 94.5

96.0

97.5

E X E M P L E 4

  Cementation of silver from the elution solution.

  As a starting solution, a solution is used

  elution at pH 2 containing 5% by volume of butadiene

  nol, 10 g / l of thiourea and 99 mg / l of silver.

  The cementation is carried out by adding 250 mg / l of iron powder and increasing additions of

  sodium pyrosulfite at 60C for 2 hours.

  The results obtained are gathered in the

Table IV.

TABLE IV

  Test N 'Silver Powder Na2S205 Dissolved Silver Fe mg / l mg / l mg / 1 AAg

1 --- --- 99 _

2 250 --- 52 5.32

3,250,250 44 4,55

4,250,500 35 3.91

at 5 250 750 19 3.13

6 --- 750 98 -

  Fe Amount of silver powder involved aAg - Amount of precipitated silver: 5

EXAMPLE 5

  Regeneration of activated charcoal by treatment with

sodium sulfite solutions.

  Active charcoal PICA G 210 A2 8 -

  16, which was used to adsorb silver from a process of leaching the zinc roasting material

with thlourea.

  After the elution of money with a solution

  of butanol / thourea, the screened and washed charcoal contained

25% by weight of moisture.

  g of this coal were treated each time in 1 l of water by increasing amounts of sulphite

  sodium for 3 hours at 70C, then used again

calf for the adsorption of silver.

  Table V shows the results that have been obtained with a regenerated activated carbon which has been treated with increasing amounts of sodium sulphite and

  used to obtain money from a social

  Elution solution containing 350 mg / l of silver.

TABLE V

  Test N 'Activated Carbon Na2SO3 Ag remained in g / il g / l solution ml / l

1 25 - 48

2 25 2.5 24

3 25 5.0 9

4 25 50.0 8

E X E M P L E 6

  Elution of silver and / or gold complexes of thlourea from activated carbon with various solvents

organic.

  Test conditions: We elected each time

  a) i g of activated charcoal containing 40% by weight of hum-

  and 0.52% by weight of silver in the dry substance:

  (b) 0.5 g of activated carbon containing 40% by weight of human

  mildew and 2.55% by weight of gold in the secondary substance

  with 40 ml of an aqueous solution which contained 10 g / l of thiourea, 0.66 g / l of sulfuric acid (= pH 2) and in each case 2 ml of one of the organic solvents indicated in Table VI. (for tests 7 to 10, we added

  in each case only 1 ml of the organic solvent).

  The elution time was 3 hours at 70C at

shaking water bath.

  Like the desorption of silver complexes and

  of thiourea takes place in a very similar way.

  However, not all solvents have been studied in the case of

  the elution of gold. Table VI which follows gives the

  results obtained with the various solvents. The features

  that no test has been carried out.

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  ## EQU1 ## where: ## EQU1 ## n - D - n C ct (D - - - -. - 0 ------- I t II t c0 0

  ## EQU1 ## where ## EQU1 ## l 'nn Vc' "'': 3'- .-

  ## EQU1 ## CD <, <W ct - 0 m ai CL.Dr W Dy -..-, - :: O Zr VV cOr "o 00000 cO c- OO tO 0O 0 ct ai Co - r '' t .: ## STR1 ## ## STR1 ## ## STR2 ## ## EQU1 ##. ## EQU1 ## ## EQU1 ## C ## EQU1 ## ## EQU1 ## ## STR2 ## ## STR1 ## r) or D Dl - Q i nC) -. - - - - - - - - - - - CoD 0 -, <O, (DCD: a CL <(D DJ N 3 : 3 (OI 0 Qt 3 = 1 '-D n "o: 3- CZr r V3 O 0 - n.-c" D (O - C o -, -_ - .: <- <<n 0. 0 ## STR1 ##

  -0 <- I <r. - -, 0 <-n - - <0 <-

  ## EQU1 ## wherein: ## STR2 ##

, (D - _-, - -O - W 'D (D CD CD

  ## STR1 ## ## STR2 ## where ## STR2 ##

N O o, _---

O O.

  -I- _ - c-t - (i aeO - - - - - - - - - - - --- - t -... -C Ct

  _1 c D I-o_O r W O WD - o o - N t ---

  a rd a lt a a a i w e w e r w e r w o r l i I I I 08 I! I: (gl 0I tJ CD -'O

Claims (10)

  1. Agent for the elution of thiourea complexes   precious metal adsorbed on activated charcoal, based on an acidic aqueous solution containing thiourea and an organic solvent, characterized in that it contains   0.1 to 50 g / l of thiourea and at least one organic solvent.   only partially soluble in water.   Agent according to claim 1, characterized   in that it contains as a partial organic solvent   water-soluble monoalcohols or polyal-   cools, optionally substituted, ethers, esters or ketones.   3. Agent according to claims 1 and 2,   characterized in that it has a pH of 1 to 5 and in that it contains from 1 to 50 g / l of thiourea and from 0.1 to   % by volume of an alcohol with 3 to 5 carbon atoms.   4. Agent according to claim 3, characterized in that it has a pH adjusted by an acid of 1.5 to   2.5 and in that it contains 0.1 to 10% by volume of n- butanol.   5. Process for obtaining precious metals, characterized by the following reaction steps: a) elution of the thiourea-precious metal complexes of the activated carbon at room temperature or under heat,   with 1 to 100 ml of the agent according to the claims   1 to 4 for 0.1 g of charged activated carbon,   (b) precipitation of precious metals from the aqueous phase   se / organic by addition of non-precious metals in the presence of a small amount of sulfite and the case   3Reactivation of the active carbon by a solution aqueous sulphite.   6. Process according to claim 5, characterized   in that the precious metal-thiourea complexes are eluted at a temperature of 20 to 80.degree.   that the concentration of thiourea in the solu-   at 1 to 10 g / l, that of the organic solvent at 1 to 20% by volume, and that the pH of the solution is brought to 1.5 to 3.   7. A process according to claim 5 or 6,   characterized in that for the precipitation of precious metals, per unit mass of precious metal bonded in the form of complex, 1 to 10 mass units of   in powdered form and 0.1 to 1 g / l of solu- reaction of sulfite.   8. A process according to claim 7, characterized   in that sulphite is added as sulphite sodium.   9. The process according to claims 5 to 8,   reacts by reactivating the activated carbon with a   solution containing 1 to 100 g / l of sulphite at a   50 to 95 ° C for 0.15 to 4 hours.