Yang Xianwan and other calculations plotted the E-pH diagram and the E-lg[Cl - ] diagram of Bi 2 S 3 -Cl - -H 2 O system at 298 K (see Figures 1 and 2), and the corresponding reaction equations and The equilibrium equation is slightly.
Figure 1 Bi 2 S 3 -Cl - -H 2 O system E-pH diagram
Fig. 2 Bi 2 S 3 -Cl - -H 2 O system E-lg[Cl - ]
As can be seen from Figure 3, Figure 1 and Figure 2:
Fig. 3 Bi(III)-S-H 2 O system potential-pH diagram
(1) In a solution containing no Cl - , the reaction Bi 2 S 3 +6H + = 2Bi 3 + +3H 2 S is unlikely to occur (its equilibrium pH = -3.67), and the oxidation potential of Bi 2 S 3 is higher (0.42). V). In the solution containing Cl - , the equilibrium line of the above reaction was significantly shifted to the right (pH = -0.027), and the oxidation potential of Bi 2 S 3 was also significantly decreased. That is, in an aqueous solution containing Cl - which can form a complex with Bi, Bi 2 S 3 is easier to be dissolved or oxidized than in a solution containing no Cl - . Accordingly Cl - CONTAINING acidic medium, processed by hydrometallurgical Bi 2 S 3 is thermodynamically feasible.
(2) Fe 3 + and Cu 2 + can completely oxidize Bi 2 S 3 , and the presence of Fe 3 + in the solution is favorable for the leaching of Bi 2 S 3 .
(3) It is necessary to keep the solution with a certain acidity. The addition of hydrochloric acid has the following effects: it is beneficial to the formation of elemental sulfur. Promote the dissolution of the bismuth oxide, to improve the solubility of bismuth in the solution, to prevent hydrolysis of the bismuth salt.
(4) Bi 2 S 3 can be leached in two ways
In the treatment of antimony ore with slurry electrolysis technology, there is also anodization of Bi 2 S 3 :
(5) The equilibrium pH value of elemental sulfur is -2.34 and the lower limit is -5.54. When the pH is greater than -2.44, the sulfur in the sulfide should be oxidized to HSO 4 - or SO 4 2 - . In fact, due to kinetics, more than 80% of the sulfur is still produced as a simple substance.
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