Super-hydrophobic ceramic membrane with dense and robust silane grafting for efficient water-in-oil emulsion separation

Separate water from water-in-oil (W/O) emulsions is essential in oil resources recycling and wastewater treatment. Hydrophobic ceramic membranes (HCM) have shown great potential in the dehydration of W/O emulsions but developing high-performance HCM is still a challenge due to the difficulty in hydrophobic modification of ceramic membranes. In this study, an HCM with high grafting density and robust structure was prepared by the grafting silane coupling agent onto an attapulgite (ATP) ceramic membrane. The hexadecyltrimethoxysilane (HDTMS) was chosen for membrane surface modification considering its reaction activity and stability based on molecular dynamic simulation. The effect of the HDTMS contents in the grafting solution and reaction time on the membrane properties were examined. The ATP membrane grafted by HDTMS solution with a content of 9600 ppm for 24 h had a water contact angle of 161° and oil permeability larger than 2207.5 L·m-2·h-1·bar-1 (LMHB). When dealing with W/O emulsions with a water content of 10000 ppm, the steady permeability, permeability recovery ratio, and water rejection of ATP-based HCM was 362 LMHB, 97%, and 99%, respectively. Ascribe to the –OH-rich nature of ATP, the performance of HCM in this work is superior to most membranes including Al2O3, ZrO2, and SiC. Hydrophobic-modified ATP provides a new idea for the development of high-performance HCM based on natural mineral ceramics.