Effect of Ball-to-Material Ratio on the Exfoliation Degree and Properties of Bentonite by High-Energy Ball Milling

Efficient exfoliation of montmorillonite (MMT) into single or few-layer nanosheets is essential for its high-value applications in gels, membrane separation, and composite reinforcement. In this study, Na + -exchanged bentonite underwent solvent-free, high-energy ball milling for 2 hours, with the ball-to-powder mass ratio as the sole variable. This method reduces the average layer thickness from >7 nm to 1-2 nm concomitantly enhancing surface charge, colloidal stability, gel viscosity, and 24 h water uptake. In contrast to conventional chemical intercalation and ultrasonic protocols, the proposed approach eliminates the need for organic solvents and costly intercalants, reduces energy consumption by more than 60%, and is characterized by simplicity, scalability, and user-friendliness. This work offers a green, low-cost pathway for the large-scale production of high-performance two-dimensional clay nanosheets and their multifunctional composites.