Correlation between Clay Minerals, Rheology, and Flotation in the Desulfurized Pulp of High-Sulfur Bauxite

Eliminating the adverse influence of clay minerals on the flotation separation of pyrite from high-sulfur bauxite has always posed a challenge. In this study, the correlations among rheology, clay minerals, and flotation in desulfurized pulp of high-sulfur bauxite were explored after the mineralogical characteristics were understood. The fine pyrite particles were closely intergrown with kaolinite, Illite, and diaspore. A total of 73.74% of the Illite and 65.60% of the kaolinite were liberated when the high-sulfur bauxite was ground to -0.075 mm, accounting for 79.33% by a ball mill. The influence on the apparent viscosity and yield stress of the pulp followed the order of kaolinite > Illite > pyrite. However, heterocoagulation occurred in the case of pyrite mixed with kaolinite and Illite, resulting in the formation of a network structure characterized by a higher apparent viscosity and greater yield stress. Generally, pulp rheology and the flotation index were negatively correlated, with the sulfur grade (S grade) in the flotation products decreasing as the apparent viscosity and yield stress increased. A strategy to mitigate the adverse effects of clay minerals on the rheological properties of high-sulfur bauxite pulp involves the addition of sodium hexametaphosphate (SHMP) to destroy this network structure. For kaolinite-pyrite mixed pulp, the S grade and sulfur recovery (S recovery) of the sulfur concentrate (S concentrate) increased by 1.36% and 6.93%, respectively, when the mass fraction of kaolinite was 60% and the apparent viscosity (or yield stress) decreased to 0.00616 Pa·s (or 0.33 Pa) from 0.00679 Pa·s (or 0.4239 Pa). This study provides valuable insights for enhancing the flotation desulfurization performance of high-sulfur bauxite through rheological regulation.