Intensified Centrifugal Dewatering of Bauxite Residue for Potential Caustic Liquor Recovery: An Upper-Bound Laboratory Consolidation Study

Bauxite residue (red mud), a highly alkaline byproduct of the Bayer alumina process, poses major environmental and geotechnical challenges owing to its fine particle size, residual caustic content, and long-term storage risks. This study proposes an integrated centrifuge-assisted framework for sustainable bauxite residue management by combining alkaline-conditioned flocculant-assisted centrifugation with potential caustic liquor recovery under intensified high-G consolidation. A response surface methodology (RSM) design was used to examine the effects of centrifugal force (1000–1800 G) and flocculant dosage (50–300 g/tonne) on solids content, void ratio, apparent residual NaOH retention, total suspended solids (TSS), and total dissolved solids (TDS). Results showed that centrifugal force had a stronger influence on dewatering performance than flocculant dosage. The highest solids content, 73.8 ± 0.5 wt%, was achieved at 1800 G and 200 g/tonne, while 1800 G with 50 g/tonne was identified as the preferred laboratory operating condition when solids consolidation, centrate clarity, and polymer consumption were considered together. Increased centrifugal loading reduced void ratio and apparent residual NaOH retention, indicating improved consolidation and potential liquor recovery. Moderate flocculant addition substantially improved supernatant clarity, whereas higher dosages under high-G conditions were associated with increased suspended solids, potentially reflecting changes in floc structure or stability. The quadratic regression model for solids content showed good agreement with the experimental data within the investigated factor domain ( R 2 = 0.936; adjusted R 2 = 0.903). Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) observations showed relatively compact, agglomerated particle morphologies and identified the principal elements present in the analyzed residue regions. Overall, the results establish an upper-bound laboratory benchmark for intensified centrifugal dewatering and provide a basis for subsequent pilot-scale evaluation of continuous centrifuge-assisted dewatering of bauxite residue.