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The Snakewushan gold ore is a strongly weathered laterite-type gold ore. The gold is highly free, which is sub-microscopic gold or ultra-microscopic gold. The content of silver and non-ferrous metals is very low. Therefore, no matter what physical ore processing method is adopted, It is impossible to obtain gold independent minerals to enrich them into gold concentrates, and only gold can be extracted by chemical beneficiation or solvent leaching. The ore is pretreated, and 91% of the gold is recovered, but some of the fine gold remains in the tailings. A large amount of tailings has been piled up in the mining area. In order to explore the possibility of utilization, a column leaching test was carried out.
First, tailings properties
The chemical analysis composition of the two gold-containing tailings is shown in Table 1, and the phase analysis results are shown in Table 2.
Table 1 Chemical analysis results of two kinds of tailings % (1)
Table 1 Chemical analysis results of two kinds of tailings % (2)
Table 2 Gold phase analysis results of two kinds of tailings
Second, the results and discussion
Gold leaching process, the ore Au, Ag and other metals in the solution CN - contacting, generating Au (CN) -, Ag ( CN) - complex ion, calculated stoichiometrically, per gram of gold, silver, respectively consumption Sodium cyanide 0.5g and 0.91g. At the same time, Cu, Fe, Zn, etc. contained in the ore also consume part of sodium cyanide. The sodium cyanide consumed per gram of copper , iron, zinc and lead is 2.3g and 5.26 respectively. , 3.0g and 0.95g. Therefore, the sodium cyanide in the solution should be in an appropriate excess. When the concentration of cyanide is in the range of 0.5-1.5g/L, the dissolution rate of gold increases with the increase of concentration. However, after the concentration of cyanide increases to a certain value, the dissolution rate of gold decreases, and some è´±The metal will be dissolved, affecting the leaching of gold. In the test, after the amount of sodium cyanide exceeded 3 kg/t, the amount of sodium cyanide continued to increase, and the gold leaching rate did not change much. Considering various factors, the amount of sodium cyanide is preferably 3kg/t.
Adding sodium hydroxide for alkaline pretreatment can weaken or eliminate the influence of harmful elements in the ore, improve the leaching environment, and achieve better leaching effect. Because the pyrite, sphalerite, chalcopyrite and other minerals present in the ore sample will produce harmful ions such as Fe 2 + , Fe 3 + , S 2 - , Cu 2 + , etc., if no alkali pretreatment, cyanide When leaching, these harmful ions consume a large amount of cyanide and dissolved oxygen, which seriously hinders the dissolution of gold and causes a decrease in the gold leaching rate. When alkali is pretreated, Cu 2 + and Zn 2 + form insoluble hydroxide precipitates, and S 2 - is oxidized to form SO 3 and SO 4 2 - , which reduces the Fe(OH) 3 to cyanide. Fe(OH) 3 surface protective film is formed on the surface of minerals such as iron ore, which hinders its rapid oxidation and further dissolution, thereby reducing the consumption of CN - .
(1) Stirring leaching test
In order to investigate the cyanide leaching performance of gold-containing tailings, the tailings were subjected to a stirring leaching test. After the tailings are pulverized, a certain amount is weighed into a cone type bottle, a certain amount of the infusion agent is added, and the stirring speed is controlled to carry out cyanidation leaching. Through orthogonal test, the dosage of sodium cyanide was determined to be 3kg/t, the mass ratio of liquid solid product was 1.2:1, and the stirring time was 8h. Under this condition, the gold leaching rates of the two tailings were 68.5% and 65.5%, respectively. It is indicated that the tailings are feasible to use cyanide leaching.
The ore sample is broken so that the particle size of 10 to 20 mm accounts for 70%. The 1.5 kg column was weighed, wetted with an alkaline solution of pH=8, and then subjected to an oxygen spray leaching test with different concentrations of sodium cyanide solution to control the spray intensity of 1 to 1.2 mL/min. The results showed that when the amount of sodium cyanide was 0.92 kg/t, the gold leaching rate was 65.6%; when the amount of sodium cyanide was 0.90 kg/t, the gold leaching rate was 64.5%.
(3) Large-scale column immersion test
The 1 # and 2 # tailings ore samples were crushed to a certain size and then packed respectively. The 1# particle size was 30-40 mm, accounting for more than 80%, and the 2 # particle size was 70-90 mm, accounting for more than 70%. Spray leaching was carried out with different concentrations of sodium cyanide solution, and the cycle was repeated once in 1 day. The results are shown in Table 3.
Table 3 Large column leaching results
Third, the conclusion
Through experimental research, gold ore tailings can be recovered by agitation and heap leaching cyanidation method. The leaching rate of gold can reach 67.19%. After comprehensive utilization, good results are obtained. The use of tailings can not only improve the economic benefits of the mine, but also produce good social benefits. The use of advanced technology and equipment to develop tailings can make tailings a new resource for mining companies in the 21st century. The low-grade gold ore heap leaching technology has developed rapidly and has been widely used in China. Received significant economic benefits. The gold mine tailings are large in quantity and have a certain reserve scale. It is feasible to use granulation heap leaching.
Cyanide leaching gold from low grade gold-bearing tailings
Secondary use of mineral resources are non-renewable resources, it is necessary to strengthen mineral resources, including gold recovery of gold from the tailings has practical significance. The granulation heap leaching technology developed in recent years has the advantages of good leaching index, low investment, low cost and quick effect. It is used to recover gold from the flotation tailings of the Shewushan Gold Mine in Hubei Province with good results.
Mineral sample
Au
SiO 2
Fe
FeO
Fe 2 O 3
Al 2 O 3
CaO
MgO
1 #
2 #
3.8×10 - 3
4.1×10 - 3
72.98
68.73
3.70
4.11
0.17
4.11
5.10
5.65
10.9
13.08
1.42
1.77
0.40
0.44
Mineral sample
MnO
TiO 2
K 2 O
Na 2 O
Cu
S
C
Lost
1 #
2 #
0.13
0.13
0.25
0.34
1.12
1.41
0.12
0.064
0.014
0.005
0.069
0.13
0.25
0.22
6.38
7.37
Mineral sample
Monomer gold
Gold sulfide
Iron oxide gold
Silicate gold
total
1 #
2 #
0.02
0.02
0.10
0.11
0.23
0.26
0.03
0.02
0.38
0.41
(2) Small column immersion test
Numbering
Sodium cyanide consumption / (kg·t -1 )
Leach rate /%
1
2
1.02
1.13
66.2
42.5