RU2431689C1 - Procedure for extraction of gold from refractory clay ore - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure for extraction of gold from refractory clay ore consists in its crumbling, sizing, after-crumbling and cyaniding. Also, sized ore with fraction of 0.5 mm is subjected to repeated crumbling. Ore is repeatedly crumbled in solution of non-ionogenic SAS (surface active substance) till formation of sludge fraction 0.02-0.05 mm which is subjected to cyaniding. 1.2-2.3 wt % solution including poly-alcohols and mixture of synthetic fat acids SFA C₁₂-C₃₀ is used as SAS at repeated crumbling. Hydraulic sizing is carried out at temperature 13-75°C.

EFFECT: intensification of process and reduced losses of gold.

3 cl, 2 dwg, 2 tbl, 2 ex

Description

The invention relates to the field of hydrometallurgy of precious metals (heap cyanide leaching of gold and silver from refractory ores) and can be used in the mining industry.

Heap leaching methods using cyanide solutions are known and widely used. Selectivity of metal extraction is achieved by a low concentration of cyanide solution (0.03–0.3%), which significantly reduces the share of competing reactions, or by concomitant non-target metals. The simultaneous presence of an alkali solution (0.005 ÷ 0.02%) stabilizes the supplied cyanide solution, and air-oxygen aeration intensifies the process of dissolution of the target metals from the feedstock.

All this together allows the noble metals to be extracted stably and relatively efficiently, converted to the corresponding complexes, followed by the precipitation of the target metals from cyanide solutions by zinc dust, sorption on coal and / or anion exchangers.

In industry, two cyanidation methods are used:

- percolation (leakage of the working solution through a layer of dispersed ore or sand) with intensive purging (I method);

- sorption cyanidation (a combined process of leaching and extraction of dissolved metals from the pulp by sorption on carbon) (II method);

- these methods have long been well known (1843 P.R. Bagration, 1856 M. Faraday, 1887-1888 J. MacArthur and brothers R. and W. Forest).

The present invention relates to hydrometallurgy of precious metals, in particular to a method for extracting gold by cyanide leaching from clay ores according to methods I and II.

The objective of the present invention is to optimize and intensify the process of gold extraction due to:

- chemical opening of ore (I method);

- hydraulic classification of raw materials with chemical opening of ore (II method).

Both of these techniques intensify the process of gold extraction and reduce the loss of the latter with tails of crystalline fractions.

Closest to the proposed invention according to method I (prototype 1) is a method of processing gold-bearing ores (RU 2096504 C1, application 9619975/02 of 1996.05.17).

The invention is reduced to the following.

The technical result is achieved by the fact that in the known method for processing gold-bearing ores, including crushing ore, forming an ore stack and subsequent heap leaching with cyanide solutions, before forming an ore stack, the ore is subjected to gravitational enrichment to obtain gravity concentrates and gravity tails, and the gravity tailings are directed to the formation of the ore head and gravity concentrates are cyanide in a separate cycle with obtaining commodity gold-bearing sediments, cyanide cakes and both gilded solutions. In this case, cyanide cakes of gravity concentrates are directed to the formation of an ore stack together with gravity tails, and desalted solutions of cyanidation of gravity concentrates are sent to heap leaching.

The difference of the proposed solution is the processing of crushed ore with a solution of nonionic surfactant (1.2 ÷ 2.3 wt.% Aqueous solution).

Closest to the proposed invention according to method II (prototype 2) is a method for extracting gold from clay ores (RU 1616159 from 1989 01.12).

The invention consists in the following.

The objective of the invention is to intensify the process and reduce the loss of gold with tails of the crystalline fraction. For this, ore containing 3.8 g / l of gold and 35% clay is wet milled and classified. Classifier plum and sands are processed separately. A fraction of 0.071 mm is separated from the drain by hydrocyclone and screening, which is sent to sorption of gold, and the saturated resin to electrolysis. Gold is recovered 49.8%. The sands of the classifier are refined and reclassified from the discharge of the classifier, after hydrocyclonation and screening, a fraction of 0.16–0.071 mm is isolated, which is subjected to sorption cyanide followed by electrolytic separation of gold. Gold recovery from the crystalline phase is 37.7%. The total gold recovery is 86.6%, which is 1.6% higher than the known methods. The number of steps in the sorption cyanidation step is reduced from 9 to 6.

The disadvantage of this method is the under-extraction of gold. The objective of the present invention is to optimize and intensify the process of gold extraction due to additional chemical opening of ore, as well as additional hydraulic classification, leading to a decrease in gold losses with tails of crystalline fractions.

The foregoing is illustrated by examples.

Example 1

Crushed ore in an amount of 100 kg (minus 2 mm) was packed in column 1 (model of a fragment of an ore stack) and treated with a nonionic surfactant (a mixture of polyalcohols and FFA С ₁₂ -С ₃₀ , 1: 1). Leaching was carried out in the mode of leakage of sodium cyanide 0.5-0.7 g / L. Gold was recovered by cementation on zinc chips. After stabilizing the concentration, the cyanide solution was recycled. The results of the experiment are presented in table 1 and figure 1.

Thus, the use of surfactants provides stabilization of the pH of the solution at a level of more than 8 and increases the gold yield by 5–6.8%, several times reducing the process time (from 2 to 0.5 days).

Example 2

The original ore was crushed and classified on sieves. A fraction of 0.5 mm was subjected to repeated grinding in a surfactant solution at a temperature of 20 ° C and above. The resulting pulp was subjected to hydrocyclone. The discharge of hydrocyclones contained 83–87% of the sludge fraction of 0.02–0.05 mm and 10–17% of the fraction of 0.05–0.07 mm.

The larger fraction was subjected to repeated hydraulic regrinding.

The discharge of hydrocyclones of I and II stages was combined and subjected to decantation and cyanidation with vigorous stirring for 4 hours.

The dissolved gold was separated by decantation and washed, followed by cementation with metallic zinc on a carbon material. Cement sludge was processed using existing technologies.

The main results are presented in table 2 and figure 2. The main effect is achieved due to the fact that after processing the surfactant, Ca, Ba, Mg, Fe, Al, and other metals partially leave the raw materials.

Thus, the use of nonionic surfactants leads to additional chemical ore opening due to the extraction of a number of metals from the rock, which in turn increases the yield of the target product from 86.6 to 89.7%, reducing the process time to 4 hours.

In this case, the optimum processing temperature of ores should be considered T≥13 ° C. An increase in temperature above 75 ° C is undesirable since dramatically increases safety requirements.

Figure 1. Dependence of the influence of concentration and the total amount of surfactants on the efficiency of gold recovery. The conditions are normal.

Figure 1 shows that the optimal amount of surfactant, leading to a maximum yield of gold, is 30 l / t when its concentration in the solution is from 1.2% to 2.3%. A further increase in the concentration of surfactants even leads to a slight decrease in the yield of the target product (gold), and an increase in its quantity does not produce any noticeable changes in the technology of the extraction process, only slightly increasing the cost of the process as a whole.

Figure 2. Dependence of the efficiency of the gold recovery process on temperature.

Figure 2 shows that at relatively low temperatures (T ° = 10 ° C and below), the effectiveness of the surfactant is reduced to zero. In the range of 10–20 ° С, a sharp qualitative jump occurs, which lasts up to 75 ° С.

Table 1 The yield of the main product and the leaching time No. Indicators Traditional method According to the prototype Proposed one Gold yield,% 69.0 75,5 82.3 2 Leaching time, day 70.0 2-3 0.5

Table 2 Clay ore gold recovery results No. Indicators Conventional heap leaching Prototype fr.0.070, ÷ 16 The proposed method FR 0.02 ÷ 0.05 one Product yield after classification,% one hundred one hundred 96 * 2 The gold content in the tails, 0.6 0.45 0.40 3 Gold recovery,% 85.0 86.6 89.7 four Planning time up to 70 days 6 o'clock 4-6 hours

Claims (3)

1. The method of extraction of gold from refractory clay ores, including grinding, classification, regrinding and cyanidation, characterized in that to intensify the process and reduce gold losses, classified ore with a fraction of 0.5 mm is subjected to repeated grinding, which is carried out in a solution of non-inogenic surfactant to the formation of a sludge fraction of 0.02-0.05 mm, which is subjected to cyanidation. 2. The method according to claim 1, characterized in that 1.2 to 2.3 wt.% Solution including polyalcohols and a mixture of synthetic fatty acids FFA C ₁₂ -C ₃₀ are used as surfactants during repeated grinding. 3. The method according to claim 1 or 2, characterized in that the hydraulic classification is carried out at temperatures of 13-75 ° C.

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