Dual-selective imprinted membrane with asymmetric recognition sites for high-selectivity toward TBBPA and Cr6+ separation

To realize the removals of different specific pollutants in wastewater with high affinity and identifiability is highly desired but not perfected yet, because it requires stringent adjustment over selectivity in membrane. Here, a dual-selective imprinted membrane (DSIM), in which the recognition sites were separately generated on the asymmetric surfaces of the membrane based on the sequential method of delayed phase inversion and surface modification steps to simultaneously separate Tetrabromobisphenol A (TBBPA) and hexavalent chromium ion (Cr6+), is reported. A collection of integrated structural and functional characterizations manifests that DSIM generates a unique asymmetric structure with different recognition sites on the different surfaces of the membrane. As a result, the DSIM displays binding capacities as high as 54.28 mg g−1 and 74.38 mg g−1 as well as high selectivity factors of 5.763 and 6.623 toward TBBPA and Cr6+, respectively, which outperform most currently reported materials. Further, the selective separation performance utilizing DSIM is also realized in a single-component system, where the permeation equilibrium of TBBPA and Cr6+ can be realized within 55 min and 60 min, respectively, and the weak interference is also proven in a binary-component system. Density function theory (DFT) reveals the interaction between recognition sites and template/analogous, which explains the reason of high selectivity. This work provides a successful example for the efficient assembly of double recognition sites on the membrane for high-selectivity and effective removals of co-existed contaminants.