Optimizing Brucite Slurry Performance for Industrial Applications: Particle Size and Surfactant Effects on Settling, Dissolution, and Rheology

This study systematically investigates the effects of particle size and surfactants (polyethylene glycol (PEG), poly(acrylic acid) (PA), and sodium hexametaphosphate (SHP)) on the settling behavior, dissolution kinetics, and rheological properties of brucite slurries. Settling experiments reveal that smaller particles (1 μm) exhibit uniform hindered settling, while larger particles (3–7 μm) undergo biphasic settling with an initial fast phase followed by compression. Surfactants significantly alter settling behavior: PA and SHP reduce the final interface height of 1 μm slurries from 10.25 cm (blank) to 3.00 cm via electrostatic repulsion, whereas PEG has minimal effect. For 3–7 μm slurries, PA/SHP induce an extended stabilization phase followed by sudden compression. Adsorption isotherms show PEG and SHP follow Freundlich behavior (multilayer adsorption), while PA fits Langmuir (monolayer). Dissolution tests demonstrate smaller particles dissolve faster (1 μm: 0.24 mmol/min vs 7 μm: 0.05 mmol/min), with PA/SHP reducing rates by 50%–85% via adsorption barriers. Rheological analysis reveals shear-thinning behavior, with 1 μm slurries viscosities decreasing from 587 mPa·s (blank) to 6 mPa·s (PA) at shear rate of 100 s–1, consistent with ζ-potential shifts (+28 mV → −30 mV). These findings provide critical insights into optimizing brucite slurry performance for industrial applications.