Effect of zinc minerals on cyanide leaching for gold ores
2020-07-17 09:45Introduction：Effect of zinc minerals on cyanide leaching forgold ores The zinc content in gold ores is generally low.The oxidized zinc minerals are easily dissolved in cyanide solution. Zinc sulphide and cyanide solution react slightly to form cyanide
Effect of zinc minerals on cyanide leaching for gold ores
The zinc content in gold ores is generally low.The oxidized zinc minerals are easily dissolved in cyanide solution. Zinc sulphide and cyanide solution react slightly to form cyanide and thiocyanate.The dissolution rate of various zinc minerals in cyanide solution is shown in Table 1.2-4.The effect of zinc minerals on gold dissolution is not as strong as that of copper minerals, but when the content of dissolved zinc in cyanide solution is greater than 0.03 ~ 0.1%, it has a great influence on the leaching of gold and silver.
Table 1.2-4 dissolution rate of zinc minerals in cyanide solution
|
Mineral name |
molecular formula |
Zinc content /% |
Dissolution rate /% |
|
| Row ore | Leaching slag | |||
|
blende willemite hydrozincite calamine franklinite zincite bonamite |
ZnS Zn2SiO4 3ZnCO3·2H2O H2Zn2SiO5(Fe,Mn,Zn)O (Zn,Mn)Fe2O4 ZnO ZnCO3 |
1.36 1.22 1.36 1.19 1.19 1.22 1.22 |
1.11 1.05 0.78 1.03 0.95 0.79 0.73 |
18.4 13.1 35.1 13.4 20.2 35.2 40.2 |
Sphalerite is reversible when dissolved in cyanide solution:
ZnS+4NaCN⇌Na2Zn(CN)4+Na2SIn anaerobic conditions, the degree of reaction to the right is proportional to the concentration of cyanide.Sodium sulphide decomposes into sodium thiocyanate and sodium hydroxide in water:
Na2S+H2O⇌NaHS+NaOH
NaHS and Na2S react with oxygen and cyanide to form sodium thiosulfate and sodium thiocyanate when aerobic
Na2S+2O2+H2O=Na2S2O3+2NaOH
NaHS+2O2=Na2S2O3+H2O
2 Na2S+2 NaCN+2H2O+O2=2NaCNS+4NaOH
2NaHS+2 NaCN+O2=2NaCNS+2NaOH
The results show that when sphalerite is dissolved in cyanide solution, oxygen and cyanide will be consumed, which will affect the leaching of gold and silver.
The reaction of oxidized minerals of zinc in cyanide solution is relatively simple:
ZnO+4NaCN+H2O=Na2Zn(CN)4+2NaOH
ZnCO3+4NaCN=Na2Zn(CN)4+Na2CO3
Zn2SiO4+8NaCN+H2O=2Na2Zn(CN)4+Na2SiO3+2NaOH
It can be seen that the oxide of zinc also increases the consumption of cyanide.
