Non-Steady State and Steady State Silicate Dissolution: Non-Carbonate Acid Neutralisation for Long-Term Acid and Metalliferous Drainage Control

Abstract

The dissolution of silicate minerals has been largely examined under steady state conditions. The primary aim of this study was to understand the potential of the non-steady state dissolution of silicate minerals in treatment of acid and metalliferous drainage (AMD) resulting predominantly from pyrite oxidation. To this end, flow-through dissolution cell experiments were carried out using selected silicate minerals (biotite, chlorite, olivine and K-feldspar), all commonly found in AMD environments, under various pH and flow rate conditions, for comparison to pyrite dissolution carried out under the same conditions. Both acid generation rate (pyrite) and steady-state and non-steady state acid neutralisation rates (silicates) were calculated and compared. Results showed that the non-steady state acid neutralisation rates due to silicate dissolution were greater than the steady-state neutralisation rates and that all silicate minerals investigated in this study, except K-feldspar, can provide acid neutralisation rates to match the acid generation rate due to pyrite dissolution under certain conditions.