RU2458160C1 - Method of gold extraction from mercury-containing cyanic solutions - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method of gold extraction from mercury-containing cyanic solutions consists in sorption by ion-exchange resin of AM-2B mark. Then mercury de-sorption is carried out from saturated ion-exchange resin at a temperature 40-50°C and for 6 hours and aurum de-sorption. Note that mercury de-sorption is done by solution containing sulfuric acid 30-50 g/l with the presence of hydrogen peroxide 5-10 g/l.

EFFECT: reduction of mercury content in saturated gold-containing ion-exchange resin till safe concentration or complete elimination of mercury penetration into finished products.

5 tbl, 1 ex

Description

The invention relates to the field of sorption technology for the extraction of gold from solutions obtained as a result of cyanide leaching of gold ore products.

Small amounts of mercury minerals in gold-bearing ores interact with sodium cyanide to form a series of mercury cyanide complexes Hg (CN) ₂ ⁰ , Hg (CN) ₃ ^1- and Hg (CN) ₄ ^2- .

To extract gold and silver in the presence of dissolved mercury from cyanide solutions, it is known to use anion-exchange sorption of metals on ion-exchange resins of the AM-2B (or Rossion-12) type [“Heap leaching of noble metals”. - / Edited by M.I. Fazlullin, Moscow: Publishing House of the Academy of Mining Sciences, 2001; p. 548-550].

Gold, silver and mercury are sorbed by ion-exchange resins collectively and practically completely, and their separation is possible only at the stage of desorption.

In sorption processes using ion-exchange resins for processing gold-containing cyanide solutions with a concentration of free cyanide ion in the range of 0.5-1.0 g / l, sorption of the multiply charged complex anion of mercury Hg (CN) ₄ ^2- prevails, while the neutral complex Hg (CN) ₂₀ ^{0 is} characterized by a lower affinity for the anion exchange resin.

Increased concentrations of mercury in productive gold cyanide solutions complicate sorption redistribution, and at the stage of regeneration of saturated resin, it is necessary to extract mercury from the resin before the gold desorption operation is performed.

Dissolved mercury contained in cyanide productive solutions of leaching of gold-bearing ores creates unfavorable sanitary and hygienic working conditions for working personnel due to toxicity of mercury (in the working area the mercury content in the air is MPC.s. = 0.005 mg / m ³ ). In addition, mercury has a harmful effect on the subsequent operations of the technological scheme for the extraction of gold from ores:

- in the process of sorption, mercury is an additional load on the sorbent, increasing the consumption of ion-exchange resins and reagents used in its regeneration;

- during the electrolysis of commodity desorbate solutions, mercury is precipitated together with gold at the cathode, significantly worsening working conditions (the concentration of mercury vapor in the service area of electrolyzers sometimes exceeds the maximum permissible concentration);

- in the processing of cathode deposits, preliminary removal of mercury from them is necessary, which is carried out by the operation of distillation (distillation) of mercury in special retort furnaces at temperatures exceeding 400 ° C.

The main objective is the purification of mercury from a saturated gold-containing ion-exchange resin by preliminary desorption of mercury from the resin before gold desorption using methods that efficiently remove mercury without significant gold loss.

The prototype, as the closest analogue to the technical solution of our proposed method for the desorption of mercury from a saturated gold-containing ion-exchange resin, can be a process carried out using a mixture of acids 70 g / l H ₂ SO ₄ and 20 g / l HNO ₃ as a stripping solution. In this case, the desorption temperature is 45-50 ° C, the desorption time is 6 hours at a feed rate of the solution of 1 v / v resin per hour in dynamic mode. Almost all impurities of non-ferrous metals (zinc, nickel, etc.), including mercury, are desorbed from the resin as a result of such an acid treatment. In this case, the loss of gold is minimal. The mercury content in the resin decreases from 19 mg / g to 0.002 mg / g. A desorbate containing a significant amount of mercury (~ 3 g / l) enters the electrochemical purification unit and then the solution purified from mercury is further strengthened with НNО ₃ and H ₂ SO ₄ and returned to the process of desorption of impurities [“Heap leaching of noble metals”. - / Edited by M.I. Fazlullin, Moscow: Publishing House of the Academy of Mining Sciences, 2001; p. 580-583].

The disadvantages of this method of desorption of mercury from an ion exchange resin are: increased consumption of acids (H ₂ SO ₄ and HNO ₃ ).

The technical result of the invention is the reduction of the mercury content in saturated gold-containing ion-exchange resin to a safe concentration or the complete prevention of mercury entering the gold desorption cycles in the finished product — rough alloy of gold alloy.

The technical result is achieved in that the extraction of gold is carried out from cyanide solutions containing mercury. Sorption is carried out on an AM-2B brand ion-exchange resin, desorption of mercury is carried out before gold desorption by treating a saturated resin with a solution of 30-50 g / l sulfuric acid in the presence of an oxidizing agent - hydrogen peroxide (5-10 g / l H ₂ O ₂ ) at a temperature 40-50 ° C and a duration of 6 hours.

Desorption is carried out in the presence of a stronger oxidizing agent - hydrogen peroxide (E ₀ = + 1.80 V) than nitric acid (E ₀ = + 0.96 V).

The following factors play an important role in the desorption of cyanide complex compounds such as Cu (CN) ₄ ^3- , Zn (CN) ₄ ^2- , Ni (CN) ₄ ^2- and Hg (CN) ₄ ^2- with a mixture of sulfuric acid and hydrogen peroxide:

- decomposition of cyanide complex compounds in the phase of the ion exchange resin;

- the formation of soluble in eluant compounds;

- the formation of cationic type compounds not retained in the phase of the ion exchange resin.

These processes proceed according to reactions of the type:

R ₂ [Hg (CN) ₄ ^2- ] + 2H ₂ SO ₄ + 2H ₂ O ₂ → R ₂ SO ₄ + HgSO ₄ + 4HCN ↑ + 2H ₂ O + O ₂ ↑

Below the essence of the present invention is explained in more detail by examples, confirming its implementation.

EXAMPLE

Saturated ion exchange resin brand AM-2B after water washing from reagents with the content of components, mg / g: 6.5 gold; 7.5 mercury; 0.2 copper; 5.3 zinc; 0.6 iron; 0.3 nickel was wet loaded into a 50 ml desorption column. The columns were equipped with a water jacket to ensure heating of the stripping solutions, which were supplied to the column from the bottom up with a speed of 1 r / v resin per hour.

The experimental results are given in table 1-4.

Table 1 Effect of H ₂ SO ₄ Concentration on Desorption of Mercury The concentration of H ₂ O ₂ - 10 g / l Temperature - 50 ° С Duration - 6 hours The concentration of H ₂ SO ₄ , g / l The residual mercury content in the resin after desorption, mg / g Desorption of mercury during desorption,% twenty 0.17 97.70 thirty 0.05 99.30 40 0.003 99.96 fifty 0.002 99.97 60 0.002 99.97

The data in table 1 show that the extraction of mercury from the resin during desorption above 99.3% is achieved at a concentration of sulfuric acid of 30-50 g / l. A significant decrease in desorption is observed with a decrease in the concentration of sulfuric acid in the stripping solution from 30 g / l to 20 g / l. Increasing the concentration of sulfuric acid over 50 g / l is impractical.

table 2 The effect of the concentration of H ₂ About ₂ on the extraction of mercury during desorption The concentration of H ₂ SO ₄ - 50 g / l Temperature - 50 ° С Duration - 6 hours The concentration of H ₂ O ₂ , g / l The residual mercury content in the resin after desorption, mg / g Desorption of mercury during desorption,% 3 0.10 98.67 5 0.05 99.30 7.5 0.003 99.96 10 0.002 99.97

From the data given in Table 2, it follows that the maximum mercury recovery of more than 99.3% was achieved at a concentration of hydrogen peroxide of 5-10 g / l.

Table 3 Temperature dependence of mercury recovery from tar during desorption The concentration of H ₂ O ₂ - 50 g / l Temperature - 50 ° C Duration - 6 hours Temperature ° C The residual mercury content in the resin after desorption, mg / g Desorption of mercury during desorption,% twenty 0.05 99.30 thirty 0.05 99.30 40 0.003 99.96 fifty 0.002 99.97 60 0.002 99.97

The maximum mercury recovery of more than 99.3% was achieved at a temperature of 40-50 ° C. Further increase the temperature of the process is impractical.

Table 4 The effect of the duration of desorption on the extraction of mercury from the resin The concentration of H ₂ SO ₄ - 50 g / l The concentration of H ₂ O ₂ - 10 g / l Temperature - 50 ° С Duration of desorption, hour The residual mercury content in the resin after desorption, mg / g Desorption of mercury during desorption,% 2 0.10 98.70 four 0.05 99.30 6 0.002 99.97 8 0.002 99.97 10 0.002 99.97

The data in Table 4 show that mercury extraction during desorption from the resin above 99.3% is achieved with a process duration of 6 hours. Further increase the duration of the desorption process is impractical

Under the conditions of increased mercury and zinc content in cyanide leaching solutions, in order to determine the change in the sorption properties of the AM-2B resin in the sorption-desorption cycles, experiments were conducted under static conditions to perform multiple sorption-desorption operations (6 cycles). Sorption was carried out from a cyanide solution with a content, mg / l: mercury - 3.5; zinc - 20 and sodium cyanide - 1000, with a ratio of resin volumes: solution equal to 1: 250, and a contact duration of 6 hours; and desorption - with a solution containing 50 g / l of sulfuric acid and 10 g / l of hydrogen peroxide with a ratio of resin volumes: a solution of 1:50, a temperature of 50 ° C and a contact duration of 6 hours.

For comparison, experiments were carried out in parallel under similar conditions using 70 g / l sulfuric acid with an addition of 20 g / l nitric acid as a stripping solution.

Table 5 Ion-exchange properties of AM-2B resin in sorption-desorption cycles No. The content of components in the resin, mg / g cycle Desorption of mercury with a solution of 50 g / l H ₂ SO ₄ + 10 g / l H ₂ O ₂ Desorption of mercury with a solution of 70 g / l H ₂ SO ₄ +20 g / l HNO ₃ Resin capacity in the sorption cycle, mg / g The residual capacity of the resin in the desorption cycle, mg / g Resin capacity in the sorption cycle, mg / g The residual capacity of the resin in the desorption cycle, mg / g mercury zinc mercury zinc mercury zinc mercury zinc one 6.9 25,2 0.002 0.3 7.4 13.0 0.05 0.2 2 7.7 19.5 0.003 0.2 7.1 14.0 0.06 0.2 3 7.5 18.3 0.003 0.2 6.9 15.0 0.08 0.2 four 7.3 20.1 0.002 0.2 7.4 14.6 0.09 0.2 5 7.5 23,4 0.002 0.2 7.6 14.3 0.14 0.2 6 7.6 21,2 0.002 0.2 6.5 15.7 0.17 0.2

From the data table. Figure 5 shows that with a 6-fold implementation of the sorption-desorption cycles, the use of a solution of 70 g / l of sulfuric acid with the addition of 20 g / l of nitric acid for mercury desorption leads to an increase in the residual capacity of the AM-2B resin with respect to mercury from cycle to cycle from 0.05 mg / g to 0.17 mg / g, which in the future under production conditions using this desorption method can lead to a sharp deterioration in the technological parameters of the gold extraction process.

At the same time, during the desorption of mercury with a solution of 50 g / l of sulfuric acid in the presence of 10 g / l of hydrogen peroxide, the sorption properties of the resin AM-2B remain unchanged.

Thus, it has been experimentally proved that the method for extracting gold from cyanide solutions containing mercury during preliminary desorption of mercury (before the operation of gold desorption) by acid treatment under the following conditions:

- concentration of H ₂ SO ₄ = 30-50 g / l;

- the concentration of H ₂ About ₂ = 5-10 g / l;

- temperature = 40-50 ° C;

- the duration of the process = 6 hours;

has several advantages:

1) significantly increases the degree of selective extraction of mercury from saturated resin,

2) the process is greatly simplified by reducing the consumption of acids (H ₂ SO ₄ AND HNO ₃ ).

Claims (1)

A method for extracting gold from cyanide solutions containing mercury, including sorption on an AM-2B grade ion-exchange resin, desorption of mercury from a saturated ion-exchange resin with a solution containing sulfuric acid, at a temperature of 40-50 ° C and a duration of 6 hours and gold desorption, characterized in that the desorption of mercury is carried out with a solution containing 30-50 g / l of sulfuric acid in the presence of 5-10 g / l of hydrogen peroxide.