Abstract
Prediction of neutral mine drainage (NMD) chemistry is difficult with the predictive tools developed for acid mine drainage (AMD). To address this problem, a methodology to assess NMD risk was developed using Lac Tio Mine waste rock as a positive control. The methodology compares the maximum potential for contaminant release (in this case, nickel) using the waste rock's total metal content and the sorption capacity of the material (q(max)) combined with a mineralogical assessment and modified kinetic leaching experiments that use a chelating agent to prevent immobilization processes from occurring. The results indicate that the potential NMD risk associated with Lac Tio waste rock would be assessed as probable with the proposed methodology. Indeed, the total nickel concentrations in the Lac Tio waste rock range from 270 to 590 mg/kg. The nickel is found in Ni-rich pyrites, which proved to effectively leach when no immobilization occurred (using ethylenediaminetetraacetic acid, or EDTA, leaching). The material's sorption capacities were between 127 and 197 mg/kg of Ni. The sorption capacity to total Ni content ratio of the material was < 1, indicating that the material has fewer sorption sites for Ni than Ni contained within the material, thereby underscoring the potential risk of Ni leaching over time. The approach proposed in this work provides an additional tool for the assessment water quality risk associated with NMD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10230-025-01023-6.