Synthesizing high-flux polymeric membranes using Kevlar and graphene oxide and treating with calcium chloride

The global demand for energy and growing concerns over environmental pollution are motivating researchers and industrialists to shift towards greener technologies. Organic solvent nanofiltration (OSN) is a rapidly emerging membrane-based technology that has shown potential to lower energy demand and waste generation. Pharmaceutical and chemical industries widely utilize organic solvents as reactants, intermediates, and cleaning agents. Consequently,energy-intensive processes are needed for solvent handling, recovery, and disposal. OSN, on the other hand, can reduce carbon footprint and be utilized as a sustainable alternative to the conventional methods commonly used in industries. However, like every new technology, there are some major shortcomings that should be resolved before widespread application. Particularly, fabricating membranes that are stable in harsh solvents is one of the foremost concerns and topics of research. Also, membrane selectivity and permeability are important factors to achieve a viable separation. For this research work, the goal was to synthesize thin and robust membranes using Kevlar polymer- an extremely strong and resistant fiber. Kevlar nanofibers have a highly ordered chain of benzene and aramid bonds that are linked by hydrogen bonds and Van der Waals forces, giving them remarkable chemical and solvent resistance properties. However, because of these strong bonds, they form a very dense structure which prevents high flux for OSN. To mitigate this shortcoming, we introduced graphene oxide (GO) as fillers to improve the flux while maintaining good rejection. GO has a very ordered structure with interconnected rings, and it was hypothesized that it can lead to channels of specific size and display a reasonable cut off. The other step that led to permeance enhancement was immersion of the membrane in calcium chloride (CaCl2) solution after casting the Kevlar-GO membrane. The purpose was to preserve membrane structure and prevent pore collapse during the drying stage. Modification of Kevlar aramid nanofiber membranes with both GO and CaCl2 led to improvement in permeance. Further process optimization using CaCl2 can provide interesting results related to the performance of membranes.

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