Cellulose nanocrystals as a rheology modifier in the processing of ultramafic nickel ores

Abstract

Rheological behaviors, such as high viscosity and yield stress of suspensions, present tremendous challenges during comminution, flotation, and dewatering in the processing of low-grade nickel ores. Owing to the presence of anisotropic serpentine, particle–particle interactions that are attractive in nature can lead to high yield stresses, which increases the energy costs for pumping slurry suspensions. In this study, we investigated the rheological behavior of low-grade ultramafic nickel ore suspensions at varying dosages of cellulose nanocrystals (CNC) at solid densities of 30, 40, and 50 wt.%. Based on the CNC dosage, the serpentine interparticle interaction resulted in aggregation at dosages of 0, 0.1, and 1.0 mg/g CNC and dispersion at dosages of 2.5 mg/g, for slurry concentrations of 30, 40, and 50 wt.%. The viscosity at 1s^-1 shear rate for 30 wt.% suspension increased from 0.12 Pa.s to 0.18 Pa.s on increasing the dosage from 0 to 1 mg/g CNC and then decreased to 0.10 Pa.s at 2.5 mg/g CNC dosage. The rheology effect by CNC was more pronounced for higher solid density such as 50 wt.%., where the viscosity increased from 2.74 to 4.42 Pa.s and then decreased to 2.3 Pa.s. This dual effect of CNCs on the rheology of ore can reduce the need for numerous hazardous chemicals used in different unit operations during nickel processing. This study paves the way for CNC to be used as post-processing flocculants for tailings management, which is one of the major environmental concerns faced by the mining and mineral processing industry.