Metal oxide, acid-soluble iron and arsenate equilibrium pH Ó© | |||
Acid dissolution reaction | Balance standard pH Ó© | ||
SnO 2 +4H + ====Sn 4+ +2H 2 O | -2.102 | -2.895 | -3.55 |
Cu 2 O+2H + === 2Cu + +H 2 O | -0.8395 | 1.921 | 　 |
Fe 2 O 3 +6H + ====2Fe 3+ +3H 2 O | -0.24 | -0.9998 | -1.579 |
Ga 2 O 3 +6H + ===2Ga 3+ +3H 2 O | 0.743 | 　 | -1.412 |
Fe 3 O 4 +8H + ===2Fe 3+ +Fe 2+ +4H 2 O | 0.891 | 0.043 | 　 |
In 2 O 3 +6H + ====2In 3+ +3H 2 O | 2.522 | 0.969 | -0.453 |
CuO+2H + === Cu 2+ +H 2 O | 3.945 | 3.549 | 1.78 |
ZnO+2H + === Zn 2+ +H 2 O | 5.801 | 4.374 | 2.88 |
NiO+2H + === Ni 2+ +H 2 O | 6.06 | 3.162 | 2.58 |
CoO+2H + === Co 2+ +H 2 O | 7.51 | 5.5809 | 3.89 |
CdO+2H + === Cd 2+ + H 2 O | 8.69 | 　 | 　 |
MnO+2H + === Mn 2+ +H 2 O | 8.98 | 6.7921 | 　 |
ZnO · Fe 2 O 3 +8H + === Zn 2+ +2Fe 3+ +4H 2 O | 0.6747 | -0.1524 | 　 |
NiO · Fe 2 O 3 +8H + === Ni 2+ +2Fe 3+ +4H 2 O | 1.227 | 0.205 | 　 |
CoO · Fe 2 O 3 +8H + === Co 2+ +2Fe 3+ +4H 2 O | 1.213 | 0.305 | 　 |
CuO · Fe 2 O 3 +8H + === Cu 2+ +2Fe 3+ +4H 2 O | 1.581 | 0.56 | 　 |
FeAsO 4 +3H + === Fe 3+ +H 3 AsO 4 | 1.027 | 0.1921 | -0.511 |
Cu 3 ( AsO 4 ) 2 +6H + === 3Cu 2+ +2H 3 AsO 4 | 1.918 | 1.32 | 　 |
Zn 3 ( AsO 4 ) 2 +6H + === 3Zn 2+ +2H 3 AsO 4 | 3.294 | 2.441 | 　 |
Co 3 ( AsO 4 ) 2 +6H + === 3Co 2+ +2H 3 AsO 4 | 3.162 | 2.382 | 　 |
PbSiO 3 +2H + === Pb 2+ +H 2 SiO 3 | 2.86 | 　 | 　 |
FeO · SiO 2 +2H + === Fe 2+ +H 2 SiO 3 | 2.63 | 　 | 　 |
ZnO · SiO 2 +2H + === Zn 2+ +H 2 SiO 3 | 1.791 | 　 | 　 |
From the pH 上 in the above table, we can see the following rules:
(1) The order of stability of the metal oxide in the acidic solution is: Sn0 2 >Cu 2 0>Fe 2 0 3 >Ga 2 0 3 >Fe 3 0 4 >In 2 0 3 >Cu0>Zn0>NiO> Coo>CdO>MnO. Since iron oxide is difficult to dissolve, separation of Mn, Cd, Co, Ni, Zn, Cu and iron can be achieved under normal pressure at a temperature of 25 to 100 ° C and a pH of 1 to 1.5.
(2) The order of stability of the ferrite in the metal in an acidic solution is:
Zn0·Fe 2 0 3 >NiO·Fe 2 0 3 >CoO·Fe 2 0 3 >Cu0·Fe 2 0 3
(3) The order of stability of the metal arsenate in an acidic solution is:
FeAs0 4 >Cu 3 (As0 4 ) 2 >Co 3 (As0 4 ) 2 >Zn 3 (As0 4 ) 2
(4) The order of stability of the metal silicate in an acidic solution is:
PbSi0 3 >FeSi0 3 >ZnSi0 3
(5) The order of stability of metal compounds such as zinc , copper , and diamonds is:
Ferrite>silicate>arsenate>oxide
(6) The pH of all oxides, ferrites, and arsenates. Both decrease with increasing temperature, which requires leaching at higher acidity.
Study on the leaching thermodynamics of zinc sulfide concentrates . The reaction of zinc sulfide (ZnS) and other metal sulfides in aqueous solution, what kind of substance will be formed at a certain pH and a certain potential, E-pH diagram can be used to study the reaction of MeS in aqueous solution. Thermodynamic law.
The main reaction equilibrium and E-pH diagrams in the ZnS-H 2 0 system are shown in the table below. [next]
Main reaction equilibrium formula and E-pH diagram relationship in ZnS-H 2 O system | ||
sequence  number | Reaction equilibrium | E-pH relationship |
1 | O 2 +4H + +4e === 2H 2 O | E=1.229-0.0591pH+0.01491gP o2 |
2 | H + +2e === H 2 | E=-0.0591 pH-0.02951gP H2 |
3 | Zn 2+ +S+2e === ZnS | E=0.264+0.02951g[Zn 2+ ] |
4 | ZnS+2H + === Zn 2+ +H 2 S ( g ) | pH=-1.586-0.51g[Zn 2+ ]0.51gP H2S |
5 | S+2H + +2e === H 2 S ( g ) | E=0.171-0.0591pH-0.02951 gP H2S |
6 | SO 4 2- +H + === HSO 4 - | pH=1.91+1g[SO 4 2- ]0.51g[HSO 4 - ] |
7 | Zn 2+ +2e === Zn | E=-0.763+0.02951g[Zn 2+ ] |
8 | ZnS+2H + +2e === Zn+H 2 S ( g ) | E=-0.857-0.0591pH-0.02951gP H2S |
9 | HS - +H + === H 2 S ( g ) | pH=8.00+lg[HS - ]-lgP H2S |
10 | S 2- +H + === HS - | pH=12.9+lg[S 2- ]-lg[HS - ] |
11 | ZnS+2e === Zn+S 2- | E=-1.474-0.02951lg[S 2- ] |
12 | Zn 2+ +2H 2 O === ZnO 2 2- +4H + | pH=10.08-0.251g[Zn 2+ ]0.25lg[ZnO 2 2- ] |
The ZnS-H 20 O-pH diagram (bottom) can be drawn from the equilibrium in the table.
It can be seen from the figure that there is a stable region of elemental sulfur. When the potential drops, pH value in the range 1.9-8, SO 4 2- reduced to elemental sulfur, and further reduced when the potential of pH <7, is further reduced to H 2 S, pH> further reduced to the HS when 7-- .
When the potential is raised, at pH<8, both H 2 S and HS − are oxidized to elemental sulfur S and then oxidized to SO 4 2- . At pH >8, HS − can be directly oxidized to SO 4 2- .
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