Bauxite residue neutralization with simultaneous mineral carbonation using atmospheric CO2

Abstract Simultaneous carbon mineralization during neutralization of bauxite residue, a caustic alkaline by-product of alumina refining, was tested using laboratory batch and a field pilot study in contact with atmospheric CO 2 . Since CO 2 sequestration is limited by the Ca concentration in the bauxite residue, extra Ca sources were added in a semi-soluble mineral and salt form (flue gas desulfurization gypsum or CaCl 2 ) to verify whether this Ca addition accelerated and enlarged the CO 2 sequestration obtained as a consequence of neutralization. The results of 55 days of batch and longer-term field tests were in good agreement, and the neutralization rate was accelerated through the addition of both Ca sources. Without the addition of the extra Ca source, atmospheric CO 2 contributed to neutralization of pore water alkalinity alone, while Ca addition induced further neutralization through mineral carbonation of atmospheric CO 2 to CaCO 3 . This simple addition of environmentally benign Ca to bauxite residue may provide a feasible bauxite residue management practice that is cost-effective and easy to apply in the field.