Geochemical Study of Laterite and Its Use as Reactive Permeable Barrier for Responsible Management of Mine Tailings at Sabodala Gold Operations

The Sabodala mine uses laterite in the tailings and water dams as the main material for the dikes of the hydraulic structures and as a sealing layer (physical barrier) to limit the seepage of discharge water and protect groundwater from contamination, arsenic in particular. For the permanent storage of arsenic in mining environments and the protection of environmental matrices (soil, water and air), it is processed in the form of scorodite (FeAsO4∙2H2O) or arsenic-adsorbed ferrihydrite. Both minerals are ecologically stable under a wide range of physicochemical conditions. This study aims to investigate the geochemical behaviour of laterite and its use in a Reactive Permeable Barrier (RPB) for the responsible management of arsenic mine tailings in a sustainable development context. The methodology begins with a physico-chemical and mineralogical characterization of laterite and mine tailings. After characterization, two kinetic tests were carried out in a control Mini-Cell Alteration (MCA) and a laterite beneficiation test in a Reactive Permeable Barrier (RPB). Electrochemical parameters (pH, electrical conductivities), sulphates, calcium ions and metalloids (As and Sb) in the leachates were measured. The results of physico-chemical and mineralogical characterizations of laterite and mine tailings showed that: (i) laterites are composed of quartz (SiO2), kaolinite (Al2Si2O5(OH)4), hematite (Fe2O3), goethite (FeO(OH)) and anatase (TiO2); (ii) tailings contain high levels of arsenic and antimony; (iii) they also include calcite, ferrodolomite, quartz albite, muscovite and chlorite. Kinetic tests in MCA geochemical studies have shown that mine tailings are non-acid-generating, with low metalloid mobility (0.90% for arsenic and 0.86% for antimony). The study of laterite recovery in an RPB in MCA showed a high retention of metalloids (55.26% for arsenic and 57.14% for antimony) and sulphate and calcium ions by the laterite layer. This reactive property of laterite helps protect groundwater from pollutants leached from mine tailings and should enable the mine to develop an appropriate management approach as part of a sustainable development strategy.