Numerical modelling of the effectiveness of sealants in retarding acid mine drainage from mine waste rock

Abstract

An extensive study was carried out to determine the effectiveness of various sealants in retarding or preventing the production of acid mine drainage (AMD) from mine waste rock and reactive tailings. In addition to cementitious compounds, the sealants included polymer and organic based solutions. Coated and uncoated (control) samples of mine waste rock and tailings were placed in large leaching columns and the leachate solutions were regularly analyzed for parameters such as pH level, redox potential (Eh), conductivity, sulphate and the dissolved heavy metals, Fe, Ni, and Cu. Concurrent with the laboratory tests, samples were exposed to weathering effects for seven months, which included one complete winter season. Mathematical models were fitted to moving averages of the measured data to establish the relationships between pH and Eh, and conductivity and sulphate concentrations which are necessary for indicating AMD production or lack thereof. These models also enabled the estimation of the terminal pH and Eh values. The results indicate that uncoated samples produce significant AMD and that the polymer and organic based solutions were more effective in retarding AMD than the cementitious coatings.