Improved dewatering of nickel laterite ore slurries using superabsorbent polymers

- Dewatering of low-grade nickel (Ni) laterites slurries using superabsorbent polymer.
- Achieving up to 90 wt.% water absorption and 55 wt.% solid sediment consolidation.
- Regeneration of the superabsorbent for multiple use and greater dewatering efficiency.

High sedimentation rates, good supernatant clarity and compact consolidation of valuable mineral slurries and waste tailings are the main requirements for effective dewatering. The current conventional flocculant-mediated and gravity-assisted thickening processes used in industry are far from being efficient in terms of maximising pulp water recovery. The present work investigates an unconventional approach using anionic, highly cross-linked polyacrylate, superabsorbent polymer to dewater slurries of three, unflocculated and flocculated, low-grade nickel (Ni) laterites ores (goethitic, siliceous goethite and saprolitic). The superabsorbent (SAB) sealed in a water permeable polyester bag was applied over 24 h contact time at 1-5 wt.% dosage to dilute (2-8 wt.% solid) and 20-25 wt.% solid, self-settled and polyacrylamide (PAM, 0-400 g/t solid) flocculated sediments generated at 10−3 - 2 M solution ionic strength, pH 2.5-10.5 and 25 °C. The results showed that SAB water absorption of 80-90 wt.% occurred within 8 h, reflecting sediment consolidation to 40-55 wt.% solid. SAB water recovery capacity was maximum at dosages of 3 and 2 wt.%, respectively, for dilute and concentrated slurries and at pH 6.0-7.0. The SAB-mediated pulp dewaterability, however, decreased markedly with increasing ionic strength and smectite clay mineral content. Slurries' pre-flocculation at up to 400 g PAM/t solid had a noticeable impact on SAB's dewatering efficacy which decreased appreciably with increasing flocculant dosage. The regeneration and recycle trials of the superabsorbent showed that there is unique opportunity for multiple use and greater pulp water recovery with a given sample. Both the water absorption and release capacities, however, decreased steadily with increasing number of superabsorbent recycles.

Graphical AbstractEffect of superabsorbent (1 g/100 g slurry) on water removed from self-settled laterite slurry as a function of time (A) and subsequent sediment consolidation behaviour at different pH (B).131