Influence of coagulants and flocculants dosing sequence on the dewaterability of oil sands mature fine tailings by pressure filtration

• Optimal oil sands tailings filtration depended on flocculant and coagulant dosing sequence. • Flocculant-coagulant sequence (F-C) generated much better filtration results than C-F. • Surface charges of tailing flocs potentially impacted floc strength and filtration efficiency. Rapid and cost-effective dewatering of wet tailings is crucial for clean and sustainable production in mineral processing. In the process of dewatering oil sands mature fine tailings (MFT) through coagulation-flocculation followed by pressure filtration, we observed that the dosing sequence of coagulants and flocculants had a significant influence on dewatering efficiency. Employing two anionic commercial flocculants (SNF3338 or Kemira PAM) together with an inorganic or a natural coagulant (aluminum sulfate, or chitosan), it was found that the sequence of flocculants followed by coagulants (F-C) gave higher net water release during filtration and lower moisture content in filter cakes than those in reverse sequence (C-F). The capillary suction time measurement showed a faster water release rate from the MFT treated with the F-C sequence. Zeta potential measurements indicated that flocs formed by treatment with the F-C sequence had lower negative potential or more positive potentials, likely contributing to the stronger floc strength and improved inter-floc porosity that favored pressure filtration. The findings in this Technical Note could help optimize the chemical treatment regime and reduce chemical consumption in the filtration of fine wet tailings.