Layered heterogeneous polyamide-hydrazide based reverse osmosis membranes with enhanced separation performance
It is the goal of membrane science to continuously overcome the trade-off between permeability and selectivity of reverse osmosis (RO) membranes. In this study we propose a strategy based on the pore characteristics of cyclobutane-1,2,3,4-tetracarboxylic acid chloride (BTC) and trimesoyl chloride (TMC) crosslinked with cyclobutane-1,2,3,4-tetracarbohydrazide (CBTH) for constructing layered heterostructures of polyamide-hydrazide membranes. By using BTC and TMC successively, the porous BTC-CBTH polyamide was employed as the bottom layer, and the dense TMC-CBTH polyamide as the top layer, creating an RO membrane with a “sparse and dense” heterogeneous structure. This layered heterostructure ingeniously differentiates the structure and function of the selective layer of the RO membrane, enabling the loose bottom layer and the dense top layer to respectively perform the tasks of support and separation. The permeability coefficient of the prepared RO membrane reached 3.82 L⋅m −2 ⋅h −1 ⋅bar −1 , which was enhanced by 29% compared with that of the polyamide-hydrazide membrane prepared by single-step interfacial polymerization, while the rejection of NaCl was maintained at 99.13 %. The heterogeneous layered construction strategy effectively improves the permeability and selectivity of the RO membrane, and provides a universal solution for consistently overcoming the “trade-off” effect in RO membranes.
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