Rapid exfoliation of well-defined vermiculite nanosheets via ultrasound-triggered limited space shear for pollutant adsorption

Abstract Well-defined vermiculite (VMT) nanosheets with promising physico-chemical properties are commercially appealing and urgently required for various applications. However, it is still challenging to realize rapid scalable production in a green and low-cost way. Herein, an ultrasound-triggered limited space shear method is proposed on the base of shear and cut collision mechanism. Exfoliation of well-defined ultrathin VMT nanosheets is achieved quickly and effectively through the synergy of cut collision effects, ultrasonic forces, and shear forces. The productivity and dimension distribution of VMT nanosheets can be readily regulated by varying the rotation space, rotation speed, and shear and cut collision forces, among which the rotation space is the critical factor. The better peeling effect is achieved under smaller rotation space. Compared to the traditional ball mill method, the time required to produce the same amount of VMT nanosheets is accelerated by a factor of 10 times for the ultrasound-triggered limited space shearer. Besides, the usage of water as exfoliated solution avoids subsequent separation process of traditional salt solvent. The colloidal solution of VMT nanosheets could be stably saved for about 6 months. The obtained VMT nanosheets exhibit excellent performance for rapid adsorption of methylene blue (MB), and can be regenerated without agglomeration and stacking of nanosheets. This rapid and high-yield method can be satisfactorily applied in the production of VMT nanosheets and other two-dimensional (2D) layered materials.