Enhanced dewaterability of colloidal hydrophilic mineral dispersions, via flocculation and gravity-assisted thickening, remains an important and technically challenging issue. To develop the right customized approach for flocculant selection to improve dewaterability, the influence of eight polyacrylamide (PAM) copolymers on flocculation, particle interactions and dewatering behaviour of fine, 9.5 wt% gibbsite dispersions at pH 7.5, 9.5 and 11.5 at 22• C is investigated. The results show that polymer charge type (anionic vs cationic) and charge density (5-45%) and molecular weight [(5-20) × 106 Da] had a striking, pH-dependent impact on dewaterability and dispersion rheology. Depending upon polymer type and dosage (50-200 g t −1 solid) and pulp pH, good to extremely fast settling rates (14-200 m h −1 ) were obtained upon orthokinetic flocculation. Sediment solid loadings recorded also showed polymer structure-and pH-dependency and were in the range 40-54 wt%. Upon shear of the pre-sedimented pulps, a 6-10 wt% solid improvement in consolidation resulted. The polymer with lower charge density (5% anionic) and lower molecular weight [(5-10) × 106 Da] was more effective in producing enhanced dewaterability of charged and neutral gibbsite particles than the polymers with higher molecular weights and/or charges. The settling rate, sediment consolidation and particle interactions (rheology) correlated positively, where faster settling flocs displayed higher sediment yield stresses which were accompanied by greater compaction behaviour. The findings underscore the need for greater understanding of the interplay between pulp interfacial chemistry and flocculant characteristics for optimum dewaterability. 2008