A novel approach for dispersion palygorskite aggregates into nanorods via adding freezing process into extrusion and homogenization treatment

Palygorskite is a natural nanorod with about 20–70 nm in diameter and 1–2 μm in length, but the intrinsic existence form of palygorskite as aggregates or bundles effaces its nanometer characteristic. In this work, a novel method for effective disaggregation of crystal bundles of palygorskite was developed via freezing assisted extrusion and homogenization process. The effects of freezing process and freezing time on the disaggregation state, micro-structure and properties of treated palygorskite were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray diffraction (XRD), N2 adsorption–desorption isotherm (BET), and rotary viscosity measurements. The dispersion of palygorskite depended greatly on freezing time, and a highly dispersed palygorskite nanorods were achieved after freezing for 4 h followed by homogenization at 10 MPa. The treated palygorskite retained its original structure, and the rods were rarely disrupted. The specific surface area of palygorskite enhanced from 163 m2/g to 237 m2/g as the freezing time increased from 0 to 8 h, and the rotary viscosity increased from 152 mPa·s of natural palygorskite to 2682 mPa·s, which was about 2.0 folds of the sample without freezing treatment.