Plant-Based Natural Surfactant for Improved Dispersion and Rheology of High-Solid Limestone Slurries

This study examines the dispersion and flow behavior of highly concentrated limestone–water slurries stabilized using an aqueous extract of Trigonella foenum-graecum (fenugreek) seeds as a natural, plant-based dispersant. Slurries with solid concentrations ranging from 25 to 65 wt% were prepared and characterized through morphological (FESEM–EDS), rheological, and physicochemical analyses, including surface tension, yield stress, and zeta potential measurements. Rheological tests were performed over shear rates of 50–1000 s−1 at 30 °C. At its critical micelle concentration (1.9 wt% or 0.019 g/cc), the fenugreek extract reduced the surface tension of water from 72.75 to 45 mN/m, decreased apparent viscosity by up to 22%, and lowered yield stress by approximately 25% at high solids loading. Zeta potential increased from +3.2 mV to +28.4 mV, indicating enhanced stability predominantly via steric mechanisms associated with saponin adsorption. These findings demonstrate that fenugreek extract can effectively improve slurry flowability and stability, providing an environmentally sustainable alternative to synthetic dispersants for industrial limestone slurry transport.