Differential dewatering responses to flocculant dosage in particulate slurries: Centrifugation versus filtration

Efficient dewatering of fine particulate suspensions remains a critical challenge in powder processing and slurry handling. Although polymer flocculants are widely used to promote particle aggregation, their effects on mechanical dewatering, particularly the contrasting responses of centrifugation and filtration, are not fully understood. This study systematically investigates the influence of an anionic polyacrylamide (AN934SH) at varying dosages on dewatering efficiency, slurry rheology, and cake consolidation. At low to moderate dosages (0–50 g/t), floc growth and enhanced permeability improved water removal in both centrifugation and filtration, reducing moisture from 37.3 % to 35.3 % in centrifugation and from 36.0 % to 35.8 % in filtration, with centrifugation exhibiting a more pronounced improvement. At higher dosages (200 g /t), however, centrifugation efficiency declined sharply to 41.2 % moisture, whereas filtration performance decreased less and remained comparatively stable (39.8 %). Higher dosages also produced denser, mechanically stronger cakes, with filter cakes exhibiting higher yield stress and viscoelastic moduli, whereas centrifuge cakes remained softer but more elastic. Mechanistic analysis indicates that these differences arise from the distinct force–viscosity relationships of the two dewatering methods: centrifugation is governed by a strong dependence of driving force/drag on viscosity, making it highly sensitive to viscosity-induced resistance, whereas filtration is buffered by pressure-driven compression and cake permeability. This work provides a unified framework linking flocculant dosage, particle aggregation, and cake properties, highlighting the fundamental differences in how centrifugation and filtration respond to flocculant dosing and offering guidance for optimizing dewatering strategies in powder processing. • Flocculant dosage controls slurry dewatering efficiency. • Centrifugation and filtration show distinct responses to dosage. • Rheology and cake structure govern differences in cake strength. • Force–viscosity effects explain efficiency differences between methods. • Optimized dosage balances water removal and cake properties for each method.