Pertinence des essais de lixiviation en batch dans la prédiction du comportement hydrogéochimique des rejets miniers

The management of mine wastes is one of the problems facing the mining industry. An appropriate management is required to minimize the environmental impacts of these wastes. The main issues are related to acid mine drainage (AMD), contaminated neutral drainage (CND), and metal leaching. Many tests have been proposed to predict AMD generation and allow planning mine waste storage. These tests are classified as static and kinetic tests. The kinetic tests results are also used to study CND generation. In addition to the management of AMD and CND generating wastes, the mining water quality must comply with environmental standards and many of these tests are used to predict water quality. The results of kinetic tests can also be used to predict the quality of mine drainage water. Batch leaching tests are also used to predict the hydrogeochemical behavior of mine wastes. In Quebec, the most used batch leaching tests are the TCLP test, the SPLP test, and the CTEU-9 test. The kinetic and batch leaching tests are carried out in different conditions. Studies in the literature have shown that the conditions in which the kinetic tests are performed enable to simulate the field conditions. While allowing to have faster prediction results than the kinetic tests, the use of the batch leaching tests to this purpose remains arguable. The question remains whether the batch leaching tests are relevant for predicting the mining water qualities. The objective of this study is to assess the relevance of batch leaching tests to predict the hydrogeochemical behavior of mine wastes. For this purpose, results of kinetic tests (column and humidity cell tests) and batch leaching tests (TCLP, SPLP, and CTEU-9 tests) were compared from former projects carried out by the URSTM. The results of both tests were compared with the concentrations in mg/l, the normalized amounts of metals in mg/kg, and the daily rates of lixiviation in mg/kg/day. Parallel to this comparison, mixtures of pure minerals were made with sulfides and acid neutralizing minerals, and submitted to weathering cell tests, while batch leaching tests were performed on the fresh and weathered (post-testing) mixtures. Sequential chemical extraction tests were also performed on the fresh and post-testing materials.