Green production of silica hydroxyl riched palygorskite by shear-assisted supercritical CO_2 separation process for dye adsorption and heavy oil viscosity reduction

摘要

A green shear-assisted rapid depressurization process was developed to produce highly-dispersed palygorskite (Pal) nanorods with abundant silica hydroxyl (Si-OH) groups by using supercritical CO2 (ScCO2) treatment. The disentangled Pal (DPal) nanorods prepared by ScCO2 were obtained with small particle sizes and high dispersity, and confirmed by electron microscopy and particle size analysis. Higher zeta potential and smaller contact angle were achieved for DPal due to the efficient exposure of Si-OH groups, consistent with the better rheological property as well as the higher adsorption of methylene blue (88%) and rhodamine B (86%). The nano viscosity reducer synthesized by DPal achieved a high viscosity reduction rate of 95% with Liaohe heavy oil, attributed to the higher degree of modification due to the increased Si-OH groups and the stronger aggregation effect on wax crystal caused by the nano viscosity reducer. The disentangled and modified Pal demonstrated great potential in dye adsorption and heavy oil viscosity reduction applications.