| Abstract: | Conclusions
| 1. |
Nitrous acid has a catalytic effect on the sulfuric-acid decomposition of galena. With oxygen at atmospheric pressure, the
presence of even small quantities of HNO2 in the solution (0.01 M) at room temperature increases the degree of oxidation of lead sulfide twofold.
|
| 2. |
The solid products of the oxidation of PbS (PbSO4 and S) form a dense film on the surface of the reacting particles, which leads to a decrease in the reaction rate. The kinetic
curves are parabolic in form.
|
| 3. |
The rate of oxidation of galena depends on the initial concentration of sulfuric acid in the solution. The order of the reaction
with respect to H2SO4 is close to unity (0.99).
|
| 4. |
The apparent activation energy of the process is 12.8 kJ/mole.
|
| 5. |
A change in the rate of mixing of the reaction mixture has almost no effect on the degree of decomposition of galena.
|
The process of the sulfuric-acid oxidation of galena, catalyzed by nitrous acid, occurs in the intradiffusional regime and
can be satisfactorily described by the Ginstling—Braunstein equation. This, equation reflects the fact that the reaction rate
depends on the completeness of the reaction due to the changing thickness of the layer of solid product that is formed. The
dependence is described by the equation for different temperatures and different concentrations of sulfuric acid in the solution:
{fx331-1} where α is the fraction of galena oxidized to the sulfate; CH2SO4is the initial concentration of sulfuric acid, moles/liter; T is temperature, K; τ is time, sec.
United Institute of Geology, Geophysics, and Mineralogy of the Siberian Branch of the Russian Academy of Sciences. Novosibirsk.
Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 56–64, July–August. 1998. |
