Two-dimensional (2D) particle coating on membranes for pervaporation dehydration of isopropanol: A new approach to seal defects and enhance separation performance

The aim of this work is to introduce a new post modification method for polymeric hollow fiber membranes with much-enhanced separation performance for pervaporation dehydration of isopropanol. An ultrathin two-dimensional (2D) ammonia functionalized graphene oxide (NHGO) was vacuum deposited on the shell side of P84 hollow fibers to seal defects without much increasing the overall mass transport resistance. The separation factor of the treated fibers in NHGO solutions for 5 min increased by more than 4 times with a small flux reduction compared to the original fibers. In addition, annealing fibers at low temperatures after the 2D modification further improved separation factor and increased fibers' long-term stability. For example, a P84 fiber treated for 5 min in NHGO and then annealed at 100 degrees C exhibited excellent performance. It had a flux of 1914 g m(-2) h(-1) and a water purity of 99.1% (i.e., a separation factor of 624). These superior properties may arise from three factors: (1) the simultaneous amidation reaction between the polymer matrix and the 2D particles effectively sealed the membrane defects and covalently bonded 2D particles on the surface; (2) the densification of the selective layer during annealing not only increased its selectivity but also reduced membrane swelling; and (3) the partial reduction of certain functional groups of the 2D particles during annealing regulated the pathway for water transport and produced a balanced membrane structure.