Effects of Mercury and Lead Minerals on cyanide leaching
2020-07-22 09:51Introduction：Effects of Mercury and Lead Minerals on cyanide leaching Lead in ores is mostly in the form of sulfides and oxides, and the most common in gold-bearing ores is galena (PbS).The cyanidation of gold and silver is often beneficial when the or
Effects of Mercury and Lead Minerals on cyanide leaching
Lead in ores is mostly in the form of sulfides and oxides, and the most common in gold-bearing ores is galena (PbS).The cyanidation of gold and silver is often beneficial when the ore contains a proper amount of lead, because lead can eliminate the harmful effect of alkali metal sulphide in cyanide solution.When zinc powder is replaced, lead can form zinc-lead partial battery on zinc powder surface and increase gold precipitation. In order to promote the dissolution of silver in cyanide solution, lead salt can be used to eliminate Na2S in order to promote the dissolution of silver in cyanide solution.Metal mercury dissolves slowly in the cyanide solution, but its compounds dissolve, but their compounds dissolve quickly:
Hg+4NaCN+H2O+1/2O2=Na2Hg(CN)4+2NaOH
HgO+4NaCN+H2O= Na2Hg(CN)4+2NaOH
During leaching, half of the chloride of monovalent mercury is reduced to metallic mercury:
2HCl+4NaCN=Hg+Na2Hg(CN)4+2NaCl
The common lead mineral in gold ores is galena PbS, which has a weak interaction with cyanide when it is oxidized, but it can produce NaCNS and Na2PbO2 after long time contact.Lead sulfite and mercury compounds play a positive role in cyanidation and they can eliminate alkali metal sulfides from the solution. Cerusite (PbCO3) can be dissolved into CaPbO2,and CaPbO2 reacted with soluble sulfides to form PbS precipitation.
It should be noted that excessive lead in pulp has adverse effects on the leaching of gold, which is stronger when lime is used as protective alkali, as shown in Table 1.2-5.
Table 1.2-5 effects of lead salts on gold dissolution at different lime concentrations
|
CaO dosage /kg.t-1 |
PbCO3 | PbSO4 | PbO | |||
|
NaCN consumption /kg.t-1 |
dissolution rate of gold /% |
NaCN consumption /kg.t-1 |
Dissolution rate of gold /% |
NaCN consumption /kg.t-1 |
Dissolution rate of gold /% | |
|
0 1 2 4 |
0.28 0.06 0.04 0.08 |
94 57.5 57.4 65.8 |
0.68 0.08 0.04 0.04 |
96.4 56.2 49.7 52.4 |
0.28 0.04 0.04 0.04 |
99.4 61.4 35.2 47.8 |
