Substantial amount of recyclable water is trapped in clay mineral waste tailings generated by the mining industry. Conventional polyacrylamide (PAM) flocculant-assisted dewatering in gravity thickeners leads to fast settling but low solid content sediment, even under modest shear/compression conditions. Significant increase in consolidation of clay mineral sediment using shear-sensitive polyethylene oxide (PEO) has been demonstrated.

In this study, the links between interfacial chemistry, PEO adsorption and dewatering behaviour, established through the effect of Mg(II) ions, talc solid loading, suspension conditioning time (18 h vs 1 h), PEO dosage (100 – 500 g polymer/t solid) and shear are shown. The adsorption kinetics and equilibrium isotherms of PEO onto talc under orthokinetic conditions have been investigated by batch depletion techniques. The adsorption rate and density increased in higher Mg(II) concentration but decreased after longer suspension conditioning time. Upon flocculation, 8 wt% solid content suspension produced both good supernatant clarity (<50 mg/dm³) and ~5 wt% greater sediment consolidation than a fast settling (10 – 30 m/h), lower solid content (2 and 4 wt% solid) suspension. An inverse correlation between PEO adsorption rate/density and settling behaviour of talc dispersion exist, implying slower polymer adsorption rate facilitated higher floc settling behaviour. Mg(II) ions, suspension conditioning time and PEO dosage all had pronounced effect on PEO adsorption affinity and settling rate, however, these factors had no noticeable effect on the extend of sediment consolidation. Dramatic improvement of 12-16 wt% in consolidation was achieved upon shear for PEO flocculated talc sediment.