| Description |
A mathematical model for simulating the neutralization of mine water has been developed and applied to the neutralization of precipitation-plant tails from a copper dump leaching operation. The results obtained from the simulation were checked experimentally in order to verify or reject the model. The neutralization of oxidized solution with Ca (OH)2 and reduced solution with KOH was approximated reasonably well by the model with respect to predicting he pH at which buffering occurs in the solution and the amount of reagent needed to achieve a given pH. The simulation of Ca(OH)2 neutralization was characterized by several buffering zones resulting from the precipitation of H-jarosite at pH - 2/5, Fe (OH)3 and Al203 'SO3 'gH2O at pH - 4.5, A1 (OH)3 at pH - 7, Fe(OH)2 and brucite at pH - 9. at pH - 4.5, A1(OH)3 at pH - 7, Fe(OH)2 and brucite at pH - 9. Similarly, KOH neutralization precipitated K-jarosite and K-alumite at pH -2, Fe(OH)2 at pH - 8, Fe(OH)3 and brucite at pH - 10. The aqueous phase contained highly stable sulfate complexes of iron, aluminum, calcium, and magnesium. Hydroxide complexes were of relatively low concentration throughout the entire neutralization process. The model is nonkinetic and uses the independent variable reaction progress instead of time. The dissolution of the neutralizing agent into the initial solution, the changes in solution composition, and the precipitation of mineral produces are determined as a function of reaction progress. The model assumes that the solution is in homogeneous internal equilibrium and heterogeneous equilibrium with the precipitating with the solution is attained, and at this point the solution has been neutralized the maximum amount possible since no further reaction can occur. The concentrations of all aqueous species and the amounts of precipitated mineral are plotted as a function of reaction progress. The neutralization curve is also determined for comparison with experimental data. |
