Brazilian Bauxite Residue Physical–Chemical Characterization and Acidic Neutralization Potential

Abstract

Physical-chemical evaluation of Brazilian (Amazon region) bauxite residue (BR) and analysis of its acid neutralization capacity (ANC) using, hydrochloric (HCl), sulfuric acid (H2SO4) and citric acid (C3H8O7) were carried out to assess the potential application of BR as soil ameliorant. Analysis indicated a particle size average size (D50) of 6.04 μm, 1.65 g cm−3 density and 18.28 mS cm−1 electrical conductivity. Mineral phases determined by XRD showed hematite, aluminous goethite, anatase, sodalite, gibbsite and quartz, in agreement with XRF (%) elemental characterization: Fe (24.38), Al (11.20), Si (7.91), Na (8.11), Ti (3.24), Ca (0.79), Zr (0.71), S (0.06), V (0.07) and Mn (0.09). ANC analyses conducted after 21 days indicated a lower acid consumption and pH equilibrium for H2SO4 and HCl (1.75 and 1.00 mol H+ kg−1, respectively and ~pH8) when comparing with C3H8O7 (2 mol H+ kg−1). Results validate and provide basis for an effective use of BR in agronomic applications.