Tuning the Functional Groups of Carbon Quantum Dots in Thin Film Nanocomposite Membranes for Nanofiltration
Huazhen Sun, and Peiyi Wu*. Tuning the Functional Groups of Carbon Quantum Dots in Thin Film Nanocomposite Membranes for Nanofiltration. J. Membr. Sci. 2018, 564, 394-403.
Carbon quantum dots (CQDs), a kind of zero-dimensional carbon-based nanomaterialscontaining a carbon core with a tiny size of only several nanometers and a shell linked with functional groups, have shown great potential in fabricating high-performance water treatment membranes due to their excellent hydrophilicity, tunable size and surface properties, and favorable polymer affinity. Herein, three functionalized CQDs with carboxyl, amino and sulfonic acid groups, respectively, were synthesized and further incorporated into the polyamide layer of thin-film nanocomposite (TFN) membranes via interfacial polymerization. The influences of functional groups of CQDs on the membrane properties were systematically investigated. Benefiting from the advantages of excellent hydrophilicity and ultra-small size of CQDs, all the TFN membranes incorporated with CQDs exhibited a higher permeate flux along with well-maintained Na2SO4 rejection efficiency and a better antifouling capacity in comparison with the thin film composite (TFC) membrane. Nonetheless, the different functional groups on CQDs also endowed these TFN membranes with different properties. Among them, the TFN-SCQD membrane possessed the highest permeate flux of 42.1 L m−2 h−1 and the Na2SO4 rejection of 93.6%. Moreover, the introduction of SCQD also endowed the TFN membrane with the best antifouling performance. Differently, the TFN-NCQD membrane exhibited a better retention of divalent cations and showed only slightly improved antifouling performance. Our investigation results reveal that the membrane properties of TFN-CQD membranes, especially separation performance, can be effectively modulated through tuning the functional groups of CQDs.