Guilin metallurgical Geological Institute analyzed the thermodynamic FeC1 3 gold leaching solution. Ferric chloride leaching of gold redox reaction. Due to the reaction:
Fe 3+ + e - ====Fe 2+
The standard reduction electrode potential E 1 Ó© =0.771 V.
And Au 3+ + 3e - ==== Au
E 2 Ó© = 1.420 V. Thus, with Fe 3+ can be oxidized to Au Au 3+. If C1 - is present in the solution, C1 - can be complexed with Au 3+ to form AuC1 4 - :
AuCl 4 - +3e - ==== Au+4C1 -
E 3 Ó© =0.994 V, so it is easier for Fe 3+ to oxidize Au to AuC1 4 - in the presence of chloride ions. By controlling the concentration of the substances involved in the reaction in the control system, the leaching of gold by the ferric chloride can be achieved, and the leaching reaction is:
Au+3Fe 3+ +40 - ==== AuC1 4 - +3Fe 2+
The primary battery electromotive force corresponding to this reaction is:
RT α( AuC1 4 - )· α 3 (Fe 3+ )
E = E ө ( Fe 3+ /Fe 2+ )- E ө ( AuC1 4 - /Au )- ——In ———————————
3F α 4 (Cl - )· α 3 (Fe 3+ )
To make the reaction spontaneous from left to right, E must be greater than zero. If a (AuC1 4 - )=10 -2 , a (Cl - )=10, it is not difficult to calculate that when a(Fe 3+ )/a(Fe 2+ )>10 1.80 , E is greater than zero.
These conditions are not difficult to meet during the actual operation. For example, at 298 K, when FeCl 3 is added to make [Fe 3+ ]=3 mol/L, [Cl - ]=10 mol/L is adjusted (FeC1 3 ionization). C1 - , adding HCl or NaCl to the insufficient concentration. The concentration of AuC1 4 - in the solution can reach 10 -2.28 mol/L. Throughout the reaction [Fe 3+ ] / "Fe 2+ ] > 10 2.80 . Such results are valuable for industrial production. Thermodynamic analysis shows that as long as a certain thermodynamic condition is controlled, sufficient Fe 3+ and C1 are maintained. - Concentration, at room temperature (25 ° C), pH 1.0, the gold can be leached with FeCl 3 solution.
Similarly, certain metals (Fe, Sn, Pb, Cu , Ag) sulfide, arsenic compounds can be reacted with iron chloride, consumption of FeC1 3, while generating the ore particle surface S attached, form a sulfur film, hindering Leaching reaction. Furthermore, the presence of organic matter and clay is also detrimental to leaching.
In recent years, there has been a 200t/d scale ferric chloride heap leaching field in the United States. The process is very simple. You only need to dig some parallel pits on the ground, pile a layer of ore, spray a layer of leaching solution, and then stack a layer. The ore is sprayed with a layer of leaching solution, and the cycle is repeated until the heaping operation is completed, and finally the rich liquid is taken out of the tank and gold is recovered therefrom. This method is suitable for processing low-grade gold mines, but the leaching rate of gold is not high because of the small gap between the mineral powder and the poor permeability.
Further, using FeCl 3 HNC Institute Yongsan leached arsenic antimony slag calcine gold, the gold leaching rate of 98% -99%. The electrodeposition rate is 98% -99%, and the total gold recovery rate is 96.54%. Compared with the cyanidation method, the leaching rate is 4%-6% higher, the total recovery rate is 5.34% higher, and the gold content in the leaching residue is also reduced from 3-5g/t to 0.75-1.5g/t.
Fe 3+ + e - ====Fe 2+
The standard reduction electrode potential E 1 Ó© =0.771 V.
And Au 3+ + 3e - ==== Au
E 2 Ó© = 1.420 V. Thus, with Fe 3+ can be oxidized to Au Au 3+. If C1 - is present in the solution, C1 - can be complexed with Au 3+ to form AuC1 4 - :
AuCl 4 - +3e - ==== Au+4C1 -
E 3 Ó© =0.994 V, so it is easier for Fe 3+ to oxidize Au to AuC1 4 - in the presence of chloride ions. By controlling the concentration of the substances involved in the reaction in the control system, the leaching of gold by the ferric chloride can be achieved, and the leaching reaction is:
Au+3Fe 3+ +40 - ==== AuC1 4 - +3Fe 2+
The primary battery electromotive force corresponding to this reaction is:
RT α( AuC1 4 - )· α 3 (Fe 3+ )
E = E ө ( Fe 3+ /Fe 2+ )- E ө ( AuC1 4 - /Au )- ——In ———————————
3F α 4 (Cl - )· α 3 (Fe 3+ )
To make the reaction spontaneous from left to right, E must be greater than zero. If a (AuC1 4 - )=10 -2 , a (Cl - )=10, it is not difficult to calculate that when a(Fe 3+ )/a(Fe 2+ )>10 1.80 , E is greater than zero.
These conditions are not difficult to meet during the actual operation. For example, at 298 K, when FeCl 3 is added to make [Fe 3+ ]=3 mol/L, [Cl - ]=10 mol/L is adjusted (FeC1 3 ionization). C1 - , adding HCl or NaCl to the insufficient concentration. The concentration of AuC1 4 - in the solution can reach 10 -2.28 mol/L. Throughout the reaction [Fe 3+ ] / "Fe 2+ ] > 10 2.80 . Such results are valuable for industrial production. Thermodynamic analysis shows that as long as a certain thermodynamic condition is controlled, sufficient Fe 3+ and C1 are maintained. - Concentration, at room temperature (25 ° C), pH 1.0, the gold can be leached with FeCl 3 solution.
Similarly, certain metals (Fe, Sn, Pb, Cu , Ag) sulfide, arsenic compounds can be reacted with iron chloride, consumption of FeC1 3, while generating the ore particle surface S attached, form a sulfur film, hindering Leaching reaction. Furthermore, the presence of organic matter and clay is also detrimental to leaching.
In recent years, there has been a 200t/d scale ferric chloride heap leaching field in the United States. The process is very simple. You only need to dig some parallel pits on the ground, pile a layer of ore, spray a layer of leaching solution, and then stack a layer. The ore is sprayed with a layer of leaching solution, and the cycle is repeated until the heaping operation is completed, and finally the rich liquid is taken out of the tank and gold is recovered therefrom. This method is suitable for processing low-grade gold mines, but the leaching rate of gold is not high because of the small gap between the mineral powder and the poor permeability.
Further, using FeCl 3 HNC Institute Yongsan leached arsenic antimony slag calcine gold, the gold leaching rate of 98% -99%. The electrodeposition rate is 98% -99%, and the total gold recovery rate is 96.54%. Compared with the cyanidation method, the leaching rate is 4%-6% higher, the total recovery rate is 5.34% higher, and the gold content in the leaching residue is also reduced from 3-5g/t to 0.75-1.5g/t.
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