Comprehensive physicochemical investigation of red mud from an aluminium industry landfill: Environmental risks and...

Red mud, a hazardous byproduct generated from the Bayer process in aluminium production, poses environmental risks due to its alkalinity and toxic elements content. This study provides a comprehensive physico-chemical characterization of red mud from an industrial landfill near Mostar, Bosnia and Herzegovina, to assess environmental impact and valorisation potential. Basic water parameters (pH, temperature, and electrical conductivity) of the flooded landfill section were measured on-site. Red mud samples showed pH values between 8.04-9.16 and a point of zero charge (pHpzc) of 8.7. Moisture content ranged from 20.08% to 37.21%, with the majority of particles < 0.25 mm. Mineral content varied between 12.45% and 17.77%, while bulk and true densities were 1.01-1.58 g/mL and 2.74-3.31 g/mL, respectively. Gamma spectrometry revealed radionuclide activity concentrations in the order ²³²Th > ²²⁶Ra > ²³⁸U. FAAS analysis showed pseudo-total heavy metal contents in the sequence Fe > Mn > Cr > Ni > Pb > Zn > Co > Cu > Cd. EDX analysis confirmed Fe₂O₃, CaO, and Al₂O₃ as dominant components (85.62%-92.35%), corroborated by FTIR spectroscopy. Heavy metal total content in plant material followed the trend Fe > Mn > Zn > Cu < Cr, Ni > Cd, with cobalt below detection limits. The results obtained in this study could provide guidelines for using red mud as a secondary raw material. Furthermore, current research highlights the importance of recycling and valorising valuable red mud components to secure future resources and reduce the irrational exploitation of conventional mineral sources.