Cherif, M, Plante, B, Coudert, L, Prieto-Espinoza, M & Guérin, J-E 2026, 'Comparative performance of Bauxsol™ and lime in acid mine drainage prevention 
from reactive waste rock for sustainable mine closure: a Canadian case study', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2615_116
(https://papers.acg.uwa.edu.au/p/2615_116_Cherif/)
Abstract: Effective mine closure strategies are essential for ensuring geochemical stability of mine wastes and minimising their environmental risks. This study investigates the potential of Australian Bauxsol™ (Bauxsol) technology adapted to bauxite residues derived from the Vaudreuil Canadian refinery (Rio Tinto Aluminium and Lithium) as a sustainable alternative to lime for acid mine drainage (AMD) neutralisation and metal immobilisation for flooded waste rocks in open pits. Thirteen stabilisations tests were conducted in batch mode using 100 g of AMD-generating waste rocks and 150 mL of deionised water under controlled laboratory conditions (150 rpm on a rotary shaker), with varying amendment ratios (5 to 15% w/w Bauxsol or lime) and reaction times (4 to 24 hours). The results showed that Bauxsol increased pH progressively from 2.9 (control) to 6.7 (15%) after 24 hours. At a 15% Bauxsol amendment ratio, contaminants mobility decreased by more than 99% for Al, Fe, Zn and Cu, and reached 97% for Cd and Cr, and 95% for Ni and Co, while maintaining moderate alkalinity. Metals immobilisation efficiencies were positively correlated with amendment dosage, likely through hydroxide co-precipitation and sorption onto ferric oxides. In contrast, lime amendment induced high pH (> 12), raising concerns about effluent ecotoxicity and the stability of secondary minerals. However, Bauxsol amendment released Na (2,895 mg L⁻¹), K (83 mg L⁻¹), Ca (510 mg L⁻¹) and Mg (320 mg L⁻¹), increasing electrical conductivity to 12.5 mS cm⁻¹, while lime amendment released less Na (160 mg L⁻¹) and K (79 mg L⁻¹) but more Ca (920 mg L⁻¹), resulting in a lower increase in electrical conductivity (7.4 mS cm-1). Thermodynamic modelling will provide an additional insight into the geochemical mechanisms involved. These findings highlight the potential of Bauxsol as a promising alternative to lime to prevent AMD generation from reactive waste rocks, supporting circular economy by valorising industrial residues. 

Keywords: mine closure, acid mine drainage, Bauxsol, lime, metal immobilisation, circular economy, flooded open pits