RU2423538C1 - Procedure for preparation of sulphide gold containing concentrates to bacterial oxidation at extraction of gold - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure for preparation of sulphide gold containing concentrates to bacterial oxidation at extraction of gold consists in preparation of pulp of concentrate and in neutralisation of its carbonate constituent. For preparation of pulp and neutralisation there is used recycled liquid phase of bio-pulp containing ions of Fe³⁺, As⁵⁺ and SO₄ ^2- with additive of hydrophilisation agent on base of silicic acid or gelatine. Neutralisation is carried out to pH=2.6÷2.8 at temperature as high, as 40°C and duration of mixing 2÷4 hours.

EFFECT: reduced consumption of sulphur acid in process of bacterial oxidation, increased efficiency, increased rate of filtration of bio-pulp and reduced contents of elementary sulphur in bio-cake.

1 dwg, 2 tbl

Description

The method of preparing sulfide gold-containing concentrates for bacterial oxidation relates to hydrometallurgical methods for the extraction of gold.

A known method of preparing sulfide gold-containing concentrates for gold recovery by cyanidation (US Pat. RU No. 1767900, publ. 02.27.1995), based on the bacterial oxidation of pulp, in which the liquid phase is represented by a biofiltrate with biomass and sulfur-alkaline solution with 10 g / l sulfur and pH 12 , 0.

In this method, the biofiltrate is used as a carrier of microorganisms, and the ferric iron contained in it is used as a chemical oxidizer of sulfides. In this case, the carbonate component of the gold-containing concentrate is already neutralized with sulfuric acid, since the vital activity of bacteria proceeds in a slightly acidic environment at pH <2.0. The method is characterized by an increased sulfur content in the bio-cake and a ~ 2-fold increase in the consumption of sulfuric acid in comparison with the classical bioleaching method [Polkin S.I., Adamov E.V., Panin V.V. The technology of bacterial leaching of non-ferrous and rare metals. - M .: Nedra, 1972, p. 287].

The closest in technological essence and the achieved result is the "Method of bacterial oxidation of gold-containing sulfide concentrates in the preparation of gold" according to US Pat. RU No. 2346063 dated 02.10.2009, including pretreatment of sulfide concentrate with acid at a flow rate of 70% of the amount supplied to the entire process of bacterial oxidation (10 ÷ 30 kg / t of concentrate).

However, despite the fact that in this method the degree of oxidation of sulfides increases, the consumption of sulfuric acid and the content of elemental sulfur in the bio-cake remain high due to the reactions:

Cyanization of a bio-cake with a high content of elemental sulfur proceeds with a high consumption of sodium cyanide (45 ÷ 55 kg / t of bio-cake), which reduces the technical and economic indicators of the gold extraction process.

The objective of the invention is to reduce the consumption of H ₂ SO ₄ on the process of preparing the concentrate for biooxidation, increasing the filtration rate of the biopulp and reducing the concentration of elemental sulfur in the bio-cake.

This is achieved by the fact that in the method of preparing sulfide gold-containing concentrates for bacterial oxidation during gold extraction, for the preparation of pulp from the concentrate and neutralization of its carbonate component, the reverse liquid phase of the biopulse containing Fe ³⁺ , As ⁵⁺ and SO ₄ ² ions with the addition of hydrophilizer based on silicic acid or gelatin and neutralization is carried out to a pH of 2.6 ÷ 2.8 at a temperature of not more than 40 ° C and the duration of mixing 2 ÷ 4 hours.

The carbonate components of the sulfide concentrate (CaCO ₃ , MgCO ₃ ) are not neutralized by sulfuric acid, but by Fe ³⁺ , As ⁵⁺ and SO ₄ ^2- ions, which, when reacted with carbonates, form insoluble compounds by the reactions:

The resulting gypsum and iron (III) hydroxide, respectively having a negative and positive surface charge [Ayler R.K. Colloidal chemistry of silica and silicates. - M .: Chemistry, 1959.- 423 pp.] Are attracted to each other and compensate for the surface potential, which leads to their coagulation and the formation of a coarse-grained precipitate 3СаSO ₄ · 2Fе (ОН) ₃ . This compound in the process of bacterial oxidation strengthens its crystalline structure, does not “catch” like gypsum in the pores of the filter cloth and the filtration rate of the biopulp remains high.

The addition of a hydrophilizer based on silicic acid or gelatin to the pulp reduces foaming during the neutralization of carbonates of sulfide concentrate, leads to wetting with a solution of hydrophobic minerals antimonite (Sb ₂ S ₃ ) and pyrite (FeS ₂ ), which during bacterial oxidation facilitates access of microorganisms and reagents to them - solvents. All this helps to accelerate the process and increase the degree of oxidation of MeS.

The method is as follows.

The carbonate component of the sulfide concentrate is neutralized by ions

Fe ³⁺ , As ⁵⁺ and SO ₄ ^2- contained in the circulating liquid phase of the biopulp to pH (2.6 ÷ 2.8) with the addition of a hydrophilizer based on silicic acid or gelatin. The process is carried out at a temperature of not more than 40 ° C and the duration of mixing (2 ÷ 4) hours.

An increase in the process temperature accelerates reactions (3, 4) and contributes to the formation of crystalline precipitates that are well filtered [Zelikman A.N., Voldman G.M., Belyaevskaya L.V. Theory of hydrometallurgical processes. - M .: Metallurgy; 1975, 504 S.], however, an increase in temperature of more than 40 ° C leads to the death of microorganisms. Therefore, the pulp preparation process is carried out at a temperature of not more than 40 ° C.

The duration of pulp mixing depends on the carbonate content in the concentrate; it is determined by stabilizing the pH and is (2–4) hours. At the end of the pulp preparation process, the liquid phase was analyzed for the content of iron and arsenic, and the degree of decomposition of carbonates was calculated by the mass loss of these elements.

The pulp thus prepared was sent to bacterial oxidation in a batch mode. Bacterial oxidation conditions: biopulp volume 2 l, solid concentration 15%, inoculant amount 0.5 l, iron and sulfur-oxidizing bacteria in the inoculant 1.6 g / l, respiratory activity of bacteria 50 μl O ₂ / ml · 15 min, temperature process 38 ° C, nutrient salts, g / l: 3 (NH ₄ ) ₂ SO ₄ ; 0.5 K ₂ HPO ₄ · 3H ₂ O; 0.5 MgSO ₄ · 7H ₂ O; 0.1 K ₂ SO ₄ , (pH biopulps) beg. 2.0, air consumption 1 l / min.

After the bacterial oxidation of the sulfide concentrate was completed, the pulp was filtered on a Buchner funnel at a vacuum of ~ 20 kPa through a paper filter with a blue ribbon with a diameter of 90 mm and the filtration rate was determined.

The solid product - bio-cake was analyzed for the content of sulfide and elemental sulfur.

For the experiments used the starting materials: sulfide gold-containing concentrate composition,%: 24.69 Fe; 7.44 As; 4.91 Sb; 16.88 S _s ; 1.78 S _SO4 ; 1.71 S ⁰ ; 4.5 Ca; 89 g / t Au and others - up to 100. Mineralogical composition of the concentrate,%: 23.12 Fe ₇ S ₈ ; 16.06 FeAsS; 5.69 FeS ₂ ; 5.45 Sb ₂ S ₃ ; 11.25 CaCO ₃ and a biopulp liquid phase containing, g / l: 20 Fe ³⁺ ; 4 As ⁵⁺ ; 0.9 Sb ³⁺ , pH 2.0. Ions are represented by oxygen sulfur compounds SO ₄ ^2- .

According to the proposed method, two series of experiments were carried out. In the first series, the ratio of concentrate (T): the liquid phase of the biopulp (W) was varied with a pulp mixing time of 3 hours and a temperature of 40 ° C. The influence of the ratio W: T on the indicators of the processes of preparation of the pulp and bacterial oxidation, the concentration of elemental sulfur in the bio-cake are presented in table 1 and in the drawing. From the presented results it is seen that the best results in the degree of decomposition of CaCO ₃ , (ε _decomp. Curve 1, the filtration rate of the biopulp υ, curve 4, and the sulfur content C,%, in the bio-cake curve 2 are observed at pH 2.6-2.8 curve 3 with the ratio W: T = 2: 1 (drawing). Upon receipt of the initial pulp with a pH of 2.6 ÷ 2.8 to acidify the biopulp to a pH of 2.0 will require no more than 8 ÷ 10% sulfuric acid from its total consumption, therefore, the reduction in acid consumption compared to the prototype may be 60%.

At higher pH> 4 ÷ 6 and the ratio W: T <1.75, the degree of decomposition of CaCO ₃ becomes less than 80%, which will lead to an increase in the consumption of sulfuric acid to neutralize carbonates and increase the concentration of elemental sulfur in the bio-cake formed during bacterial oxidation of sulfides according to reactions (1) and (2).

At pH <2.5 (W: T> 2.5), carbonates decompose by 98-98.5%, but due to the incomplete consumption of Fe ³⁺ ions in the pulp, the pyrrhotite oxidation process begins by the reaction:

The resulting elemental sulfur during bacterial oxidation is practically not oxidized [Sovmen V.K., Guskov V.N., Bely A.V. and other processing of gold ores using bacterial oxidation in the Far North. - Novosibirsk: Nauka, 2007. - 144 p.] And when extracting gold from bio-cake by cyanidation increases the consumption of an expensive and toxic reagent - sodium cyanide.

Table 1 The influence of the ratio of the liquid phase of the biopulse: concentrate (W: T) on the pH of the pulp, the degree of decomposition of CaCO ₃ and the content of elemental sulfur in the bio-cake. (Pulp preparation: loading the concentrate into the liquid phase of the biopulse for 0.5 hours, the total duration of the process is 3 hours, temperature 40 ° C, the addition of a hydrophilizer based on silicic acid). Bacterial pulp oxidation: Stv = 15%, reactor volume 2 l; temperature 38 C; the concentration of iron and sulfur oxidizing bacteria in the pulp is 1.6 g / l, the respiratory activity of bacteria is 50 ÷ 20 μl O ₂ / ml · 15 min, duration 10 days.) The ratio of biofiltrate: concentrate in the original pulp (W: T) Process indicators The degree of decomposition of CaCO ₃ ,% pulp pH The filtration rate of the biopulp, t / m ² · h The concentration of iron in solution, g / l Concentration
S ⁰ in bio-cake,% 0.5: 1 24.0 6.10 0,021 - 2.78 1: 1 47.1 6.07 0.058 - 2.17 1.5: 1 72,2 6.07 0,076 - 1.88 2: 1 95.3 2.70 0,083 0.05 1.78 2.5: 1 98.0 2,50 0,085 0.40 2.07 3: 1 98.1 2.47 0,088 0.56 2,51 3.5: 1 98.5 2.40 0,089 0.88 3.15

In the second series of experiments, the effect of hydrophilizer additives on pricing during the preparation of the initial pulp and the main indicators of the bacterial oxidation of sulfide concentrate were studied (table 2).

С_K+=13,4 г/л, рН 1,3) составил 2 мл/л биопульпы, а 1% - ного раствора желатины - 1 мл/л биопульпы.The hydrophilizer consumption is determined empirically for each sulfide concentrate and depends on the concentration of hydrophobic minerals Sb ₂ S ₃ and FeS ₂ . When processing the test concentrate, the consumption of acidic silicon-potassium solution

With _{K +} = 13.4 g / l, pH 1.3) amounted to 2 ml / l of biopulp, and a 1% gelatin solution - 1 ml / l of biopulp.

The addition of hydrophilizers to the pulp not only reduces the stability of the foam formed during the neutralization of alkaline earth metal carbonates, but also increases the productivity of the reactors at the stage of bacterial pulp oxidation by 16% and 18%, respectively, in the presence of gelatin or acidic silicon - potassium reagent. The degree of oxidation of metal sulfides in this case increases by (2.4-3.0)%.

table 2 The effect of hydrophilizer on pricing in the preparation of the initial pulp and the main indicators of bacterial oxidation of sulfide concentrate (W: T = 2: 1, t = 40 ° C, n = 500 rpm, τ = 3 hours) No. p / p The conditions for the preparation of the original pulp Pulp foaming Indicators of bacterial oxidation of MeS Productivity, kg / m ³ · hour The oxidation state of MeS,% one No hydrophilizer added The presence of stable foam during loading of the concentrate into the biofiltrate 0.92 86.5 2 The addition of acidic flint-potassium solution, 2 ml / l of biopulp Insignificant, the duration of the "life" of CO ₂ gas bubbles is 1-2 s 1,08 89.1 3 Additive 1% gelatin solution, 1 ml / l biopulp A small length of the "life" of gas bubbles of CO ₂ is equal to 2-3 1.06 88.5

Thus, the optimal parameters of the process for preparing pulp of a sulfide gold-containing concentrate for bacterial oxidation are:

- neutralization of the carbonate component of the sulfide concentrate by ions

Fe ³⁺ , As ⁵⁺ and SO ₄ ^2- contained in the circulating liquid phase of the biopulp (biofiltrate or clarified solution), up to pH (2.6 ÷ 2.8);

- additive in the pulp of a hydrophilizer based on silicic acid or gelatin;

- process temperature no more than 40 ° C;

- the duration of the pulp mixing (2 ÷ 4) hours;

Carrying out the pulp production process in compliance with the specified parameters allows to reduce the consumption of sulfuric acid by 60%, increase the productivity of bacterial oxidation by (16 ÷ 18)%, reduce the content of elemental sulfur in the bio-cake by 1.5 ÷ 1.7 times and increase the filtration rate of the biopulp to 0.083 ÷ 0.086 t / m ² · h.

Claims (1)

A method of preparing sulfide gold-containing concentrates for bacterial oxidation during gold recovery, comprising preparing pulp from a concentrate and neutralizing its carbonate component, characterized in that the reverse biofuel containing liquid Fe ³⁺ , As ions is used to prepare pulp from the concentrate and neutralize its carbonate component. ⁵⁺ and SO ₄ ^2- , with the addition of a hydrophilizer based on silicic acid or gelatin, and neutralization is carried out to pH = 2.6 ÷ 2.8 at a temperature of not more than 40 ° C and the duration of stirring 2 ÷ 4 hours